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- Laser Applications
- Solid State Lasers I
- Poster Session XIV: Optics Components
- Optics Components
- Laser Applications
- Poster Session II: Solid State Laser Technology
- Solid State Lasers II
- Gas and Dye Lasers
- Poster Session I: High-Average-Power Solid State Lasers
- Solid State Lasers I
- Poster Session XII: CO and CO2 Lasers
- Chemical Lasers
- Solid State Lasers I
- Optics Components
- Optics Analysis
- Solid State Lasers I
- Poster Session II: Solid State Laser Technology
- Poster Session XV: Optics Analysis
- Poster Session I: High-Average-Power Solid State Lasers
- Poster Session III: Ti:Sapphire Solid State Lasers
- Poster Session IX: Applications (Metrology and Detection)
- Poster Session VIII: Applications (Modulation)
- Poster Session XI: Gas Lasers
- Chemical Lasers
- Poster Session VII: Applications (Lidar)
- Poster Session IX: Applications (Metrology and Detection)
- Poster Session V: Nonlinear Optical Phenomenon
- Poster Session XIV: Optics Components
- Poster Session V: Nonlinear Optical Phenomenon
- Solid State Lasers II
- Poster Session VIII: Applications (Modulation)
- Solid State Lasers II
- Optics Analysis
- Poster Session XIV: Optics Components
- Solid State Lasers I
- Optics Analysis
- Gas and Dye Lasers
- Poster Session XI: Gas Lasers
- Poster Session XV: Optics Analysis
- Laser Applications
- Poster Session XI: Gas Lasers
- Poster Session X: Excimer Lasers
- Poster Session XII: CO and CO2 Lasers
- Poster Session IV: New Solid State Laser Materials
- Solid State Lasers II
- Poster Session XV: Optics Analysis
- Laser Applications
- Poster Session I: High-Average-Power Solid State Lasers
- Poster Session XV: Optics Analysis
- Chemical Lasers
- Poster Session IV: New Solid State Laser Materials
- Poster Session III: Ti:Sapphire Solid State Lasers
- Poster Session II: Solid State Laser Technology
- Poster Session VI: Applications (Internal Confinement Fusion)
- Gas and Dye Lasers
- Poster Session IX: Applications (Metrology and Detection)
- Poster Session VII: Applications (Lidar)
- Poster Session XII: CO and CO2 Lasers
- Poster Session VII: Applications (Lidar)
- Poster Session IX: Applications (Metrology and Detection)
- Poster Session XIII: Chemical Lasers
- Poster Session XVI: Miscellaneous Topics
Laser Applications
Squeezing of radiation field in multiphoton processes
Show abstract
Squeezing of electro-magnetic field, which is a purely quantum phenomenon has attracted considerable attention owing to its low noise property with applications in high quality telecommunication. This quantum effect is expected to manifest itself in optical processes in which the nonlinear response of the system to the radiation field plays an important role. In this paper squeezing of electro- magnetic field in some multi-photon processes are investigated under short-time approximation. The processes studied include Raman and hyper Raman processes and sum- frequency generation. The coupled Heisenberg equations of motion for field operators are set up and solved under short-time approximation. The occurrence of squeezing of field is investigated using the required conditions of squeezing in each of the cases. The squeezing is found to exist in the fundamental mode and the squeezing in the generated field depends on squeezing in fundamental mode. Squeezing in higher order amplitudes are also studied. This corresponds to the squeezing of the variables which describe the real and imaginary parts of square and cube of the complex amplitudes of the radiation field. The higher order multimode sum squeezing of radiation field is dealt with for harmonic and sum frequency generation. It s shown that squeezing in the sum frequency field depends directly on the sum squeezing of fundamental modes. The results can be utilized in selecting a suitable process which will generate a radiation field with optimum squeezing and can be useful in high quality telecommunication.
Longitudinal mode selection in a dye Q-switched ruby laser: a comparison between theoretical and experimental results
Thangavel M. Thevar,
John Watson
Show abstract
This paper provides a mathematical analysis to calculate the number of longitudinal modes and their relative strength in a dye Q-switched ruby laser. The calculations were based on formulae developed to accurately predict the number of loop transmits that occur while the laser pulse builds up from noise levels. An experiment was carried out using a ruby laser set-up to confirm our theoretical predictions. The number of longitudinal modes present in the laser output was evaluated by recording holograms of a two meter long graduated panel using the same laser source. The end results closely matched our theoretical predictions. This proven mathematical analysis was then applied to our laser design to optimize the longitudinal mode selection property of the dye Q-switch in the laser. As a result, the developed ruby laser produced single longitudinal mode pulses at a probability of 98%.
Solid State Lasers I
Design and construction of high-power solid state laser amplifiers with phase conjugating mirror
Hans Joachim Eichler,
Andreas Haase,
Baining Liu,
et al.
Show abstract
Beam quality improvement of high power solid state lasers for industry and science is a crucial point. A simple way to increase the beam quality of conventional flash lamp pumped rod systems is to use a phase conjugating mirror based on stimulated Brillouin scattering (SBS). Pulsed multi amplifier setups with SBS were investigated. Nd:YALO as active material was used to avoid stress birefringence and decrease of beam quality. In case of serial arrangements on optimized optical system between the individual rods is used to achieve high efficiency independent of thermal lensing. With a two amplifier system an average output power of 1 Watt up to 210 Watt in a near diffraction limited beam was realized. In case of parallel arrangements phase coupling of the individual beams was achieved using a common SBS-cell after the first amplifier pass. First experiments show an average output power of 50 W. CW-pumped MOPA-systems with SBS and repetition rates above 10 kHz are under development. A fiber phase-conjugator is used to reduce the power threshold down to 6 kW. An average output power of 14 Watt from a pulsed MOPA-system was achieved with a fiber phase- conjugator. As an application high power second harmonic generation was realized.
Poster Session XIV: Optics Components
Dichroic mirror for high-power Nd:YAG laser
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The paper presents the design of a dichroic mirror used in a Nd:YAG high power laser to reflect the 1.44 micrometers radiation and to transmit the 1.064 micrometers one. In order to obtain a wide transmission band, all the solutions for matching basic stack with the substrate, consisting in a number of periods less or equal than three, were investigated and the best was selected. The solutions were obtained by analytical inversion of the equations for the three layer equivalent system.
Optics Components
Optical coatings for HF overtone laser
Shengming Xiong,
Yundong Zhang
Show abstract
Optical components which highly reflect the hydrogen fluoride (HF) overtone wavelengths (near 1.3 micrometers ) and transmit or absorb the HF fundamental wavelengths (2.6 to 3.1 micrometers ) can be used to obtain high intensity 1.3 micrometers radiation with HF chemical laser technology. This paper describes the development of the HF overtone laser resonator mirrors. Also presented are the designs of the coatings for laser resonator and the optical performance results for the coatings which includes separated coatings that are highly reflected in 1.3 - 1.4 micrometers wavelengths and highly transmitted or low reflected in 2.6 - 3.1 micrometers wavelengths and the double band antireflection coating for 1.3 - 1.4 micrometers and 2.6 - 3.1 micrometers .
Laser Applications
Investigation of absorption saturation in diode end-pumped microchip lasers
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Two sorts of microchip laser materials, such as Nd:YVO4 and Er/Yb:Cr phosphate Kigre glass, are used to perform the experimental study of pump absorption saturation. A spatial- dependent rate equation model has been developed for the simulation, and hence the corresponding absorption saturation intensities are determined, the pump saturation intensity is 840 W/cm2 in the (pi) -polarization, and 2200 W/cm2 in the (sigma) -polarization for the 3% a-cut Nd:YVO4 crystal for the 810 nm pump wavelength, and 130 kW/cm2 for Er/Yb:Cr phosphate Kigre glass for the 975 nm pump wavelength. Based on this nonlinear absorption effect, a high performance LD end-pumped Nd:YVO4 microchip laser was obtained with a low pump threshold of 3 mW and a high slope efficiency of 50%, while for Er/Yb:Cr phosphate Kigre glass laser, a low pump threshold of 5 mW and 20% slope efficiency was obtained when pumped by a Ti:Sapphire laser. All the laser operated in a single transverse mode, and the 1.535 micrometers laser operated at a single longitudinal mode. This study gives a useful guideline to design and to optimize the pump beam radius of LD end-pumped microchip lasers.
Poster Session II: Solid State Laser Technology
Output optimization for pumping solid state lasers with fiber-coupled laser diodes
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A useful model has been developed for the optimization of fiber-coupled laser-diode pumped lasers by including the effect of pump beam quality into the mode overlap integrals. Simple analytical expressions for the optimum pump spot size, the threshold pump power, and the slope efficiency have been derived by fitting the numerical results of the mode overlap integrals to an analytical function which is in terms of laser-diode beam quality and properties of the active medium. With these expressions the optimum mode size and the maximum output efficiency can be calculated for arbitrary values of pump beam quality and input power. Also, we obtained an analytical expression to relate the required input power and pump beam quality to the desired output efficiency and properties of an active medium. The present model provides a straightforward procedure to design the laser resonator and the optical coupling system for output optimization. To illustrate the utility of the present model, a Nd:YAG laser pumped by fiber-coupled laser diodes is considered and optimized. Experimental results have shown a fairly good agreement with the theoretical predictions.
Solid State Lasers II
Frequency tunable Ti:sapphire laser system for UV lidar
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Multipass Ti:sapphire amplifier for the light source of DIAL was developed in an angular-multiplexing, and the characteristics of output energy and spectrum was investigated. In the two-stage multipass amplifier, we obtained the maximum output energy of 42 mJ, the amplification gain of 21 dB and the output efficiency of 26% on the wavelength of 790 nm. In the tuning range of 715 approximately 930 nm the spectral linewidth is 0.05 cm-1. The conversion efficiencies of 35% for SHG at 780 nm and 13% for THG at 390 nm are obtained respectively. The continuous tunabilities of 240 approximately 306 nm in UV region and 360 approximately 460 nm in deep-blue region could be achieved.
Gas and Dye Lasers
kHz repetition rate operation of excimer laser
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We have developed an excimer laser of compact coaxial type which the one line cross flow fan is only used. At 1 kHz repetitive operation, the average power of KrF laser is 56 watt. In this paper, the design parameters and CR characteristics are investigated for the attainment of the 1 kHz excimer laser. We have obtained the overall efficiency of 1.2% with KrF laser gas. At this time, CR and the variation of laser output are 2.97, +/- 9%, respectively. Laser gas volume and active volume are 10 liter, 1.8 (H) X 1.2 (W) X 30 (L) equals 64.8, respectively.
Poster Session I: High-Average-Power Solid State Lasers
Impact of lensing on interferometric analysis of high-average-power solid state media
Julia M. Laurenzano,
Bruce W. Liby,
Jacy O. Grannis,
et al.
Show abstract
Temporal methods of fringe analysis have been used to measure transient effects due to high average power thermal loading in solid-state optical crystals. Studies using a dual-interferometric configuration have revealed non-uniform and non-reciprocal lensing to be a significant source of error in the output fringe patterns. This study isolated and quantified the impact of such lensing with respect to interferometric analytic techniques.
Solid State Lasers I
Modeling of high-power cw Nd:YAG laser welding
Evelyne Dumord,
Jean-Marie Jouvard,
Dominique F. Grevey
Show abstract
The model developed allows to know the temperature field in a cw Nd:YAG laser joining piece. To realize the model, a physical approach has been used for defining the heat sources. First, from a pressure balance the geometry of the keyhole is determined. Then, an analysis of the plume existing at the surface of the target shows that the beam is scattered by the plume and consequently one more heat source must be considered. The spectrometric characterization indicates that no ionized particles exist in the plume and certainly in the keyhole. So Fresnel absorptions must be the predominant effects for energy absorption in the keyhole. This assumption has been verified owing to Fresnel absorption coefficient measurements.
Poster Session XII: CO and CO2 Lasers
Ridge-waveguide type microwave-pumped system versatile to both CO2and CO lasers
Yutaka Kodama,
Heihachi Sato
Show abstract
A prototype of ridge-waveguide type microwave pumped systems versatile to both CO2 and CO lasers has been adopted to a compact fast-axial flow scheme. Dependence of the output power Pout on total gas pressure p, microwave power Ppump and gas-flow velocity (nu) is investigated for both the lasers, together with the effect of (nu) on gas temperature T. The maximum output powers of 42 W and 15 W are, respectively, obtained with the discharge lengths of 11 cm and 37 cm for CO2 and CO lasers, corresponding to the scaling-powers of 380 W and 38 W to a unit discharge length. Since the ridge-waveguide is, thus far, not optimized yet, there is still some room in CO laser to be modified for effective pumping, involving the direction of gas-flow.
Chemical Lasers
Effects of mirror expansions to obtain higher power from an unstable resonator
Kenzo Nanri,
Tomoo Fujioka
Show abstract
Effects of mirror expansions to obtain higher power from an unstable resonator are proposed. Calculations are performed for expanding radius of a concave or a convex mirror to reduce the diffraction loss power from the concave mirror and to convert the power spread out from it into the output power. The Fresnel-Kirchhoff formula is used for the iterative computer calculation in the passive resonator and a CO2 laser. The calculations show that the increase of the output power can be obtained more than 25 percent with expanding the convex mirror in the CO2 laser.
Solid State Lasers I
Improvement of the beam quality of the high-power solid state laser using phase conjugation
Jun Chen
Show abstract
Stimulated Brillouin Scattering (SBS) as a phase conjugate mirror is successfully used in high power solid state laser system due to its self adaptive character and his simple step without optical damage in SBS medium. In oscillator and in amplifier with the SBS phase conjugate mirror the output beam quality has been improved. The beam quality with the diffraction limit and high power were obtained.
Optics Components
High-average-power Nd:YAG slab with laser with improved beam quality
Shiwen Zhang
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The fundamental concepts and developments of solid-state slab laser technology is briefly reviewed. The performance of the high average power zigzag Nd:YAG slab laser facility having been established at NCRIEO is presented. Experiments with several slabs of different dimensions and qualities were performed and the results of two of them are presented. Stable, cylindrical and spherical unstable resonator configurations were tested. When the devices worked at a repetition rate of 50 Hz and the pumping pulse energy of 307 J, the maximum output from a cylindrical 1D unstable resonator is 690 W with a total efficiency of 4.5%. The divergent angle is 3.6 X 0.5 mrad in Y and X directions respectively corresponding to about 10.8 X 1.62 times diffraction limit and a beam parameter product d0/4 about 5.5 X 0.75 mm.mrad in Y and X directions respectively. The device worked continuously at above 630 W output level for an hour. When the device worked at a repetition rate of 100 Hz, the maximum output power was 520 W.
Optics Analysis
Gaussian output coupler and resonator geometry of confocal unstable resonator
Jinxiong Wang,
Zongying Mu,
Pinglei Zhang
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In this paper, we present a simple and easy-use geometrical approach for designing the unstable resonator of Nd:YAG laser with a Gaussian output coupler. An equivalent rear mirror, which formed a confocal resonator with the output coupler, was introduced to include the effects of rear mirror, the thermal focus of YAG rod and optical path of Q- switch. Numerical results were calculated for various couples of matching curvatures of rear mirror and output coupler under the confocal condition. The correspondent optimal spot sizes of the output coupler were also given. Couples of mirrors were selected according to theoretical parameters and applied to the experimental setup. A high- beam-quality output with Gaussian profile, and high efficiency of second harmonic generation were obtained. The experimental results were in good agreement with theoretical prediction.
Solid State Lasers I
Low pump power, passively Q-switched erbium-doped fiber laser
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A novel structure FP cavity erbium-doped fiber laser is reported in this paper. The passively Q-switched operation of the laser has been achieved by using a bulk semiconductor waveguide as a saturable absorber. Under 15 mW pump power, pulse of 2 microsecond(s) full width at half maximum and peak power close to 22 mW has been obtained.
Poster Session II: Solid State Laser Technology
Simple method to tune the pulse-width for a single-mode Q-switched YAG oscillator
Weiming He,
Zhiwei Lu,
Qi Wan,
et al.
Show abstract
This report deals with a simple method to tune the pulse- width for a single-mode Q-switched YAG oscillator by simply changing the inner distance of two-cell stimulated Brillouin scattering (SBS) systems. The SBS pulse is amplified as it returning into the YAG medium and then output coupled by a quarter wave-plate and a cavity polarizer. This double-pass phase-conjugate configuration improves the laser beam quality. Less than 2 times diffraction-limited divergence is achieved. Pulses with 2 - 8 ns tunable range and about 10 mj pulse energy are obtained.
Poster Session XV: Optics Analysis
Optimum design of Q-switched Nd:YAG lasers with super Gaussian mirrors
Show abstract
Recently, high beam quality, large energy pulsed lasers with variable reflectivity mirrors has increasingly applied in nonlinear optics, scientific research lidar, industry manufacture, and military etc. To obtain high beam quality and efficient extraction simultaneously from an unstable resonator, the super Gaussian mirrors peak reflectivity R0, the super Gaussian order n, and the round-trip magnification M are three key parameters which must be carefully selected. In this paper, intensive investigation on beam quality of unstable resonators with VRM affected by R0, n, M, R0Mn is presented by computer simulation. A optimum design resulting near diffraction limited beam quality, large energy, high repetition is obtained. Various VRM tested in Q-switched Nd:YAG lasers pumped by flashlamp. Less than 2 X LD, 6 ns, 40 Hz, 350 mj/pulse laser beams are obtained in single oscillator, more than 1 J/pulse is realized through one amplifier. The experimental results are in good agreement with the optimum design.
Poster Session I: High-Average-Power Solid State Lasers
Modeling of thermal lensing in cw end-pumped solid state lasers
Jin Yu,
Hongxiang Meng,
Tianfeng Jin
Show abstract
Thermal focusing acts as a key role in limiting and degrading the laser performance in a continuously end-pumped solid-state laser. In order to evaluate the deleterious effect caused by thermal lensing in such a laser scheme, heat transfer equation is solved to obtain the temperature distribution in an edge-cooled and axially Gaussian beam heated rod in the form of a power series, taking into account only the radial heat flow, which is a reasonable simplification of the real situation. Also, under the two assumptions of thin disk and long rod, the induced stress- and strain-field are deduced, respectively. Thus the analytical expressions for the induced thermal focusing length are determined over the extent of axially average pump spot size, considering all the following three elements contributing to thermal focusing: thermal dispersion, surface deformation and stress-induced birefringence, and regarding the rod as thin lens and thick lens, respectively. The results are applied to cubic crystals, such as Nd:YAG and Nd:GSGG, and the homogeneous medium of silicate Nd:glass. It can be seen that with ten watt of pump power, the effective focusing lengths of these materials are in the order of millimeters and much more serious than those predicted by other authors.
Poster Session III: Ti:Sapphire Solid State Lasers
Design and performance of an astigmatism-compensated self-mode-locked ring cavity Ti:sapphire laser
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Based on the nonlinear ABCD matrix and the renormalized q- parameter for Gaussian-beam propagation, self-focusing in conjunction with a spatial gain profile for self-mode locking in a ring-cavity Ti:sapphire laser are analyzed. In the experiment, an astigmatism-compensated self-mode-locked ring-cavity Ti:sapphire laser is demonstrated, and self- mode-locked operation is achieved in both bidirection and unidirection with pulse durations as short as 36 fs and 32 fs, respectively. The experimental observations are in good agreement with theoretical predictions.
Intracavity frequency doubling in a self-mode-locked Ti:sapphire laser
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In this letter we report the use of intracavity frequency doubling in a self-mode-locked Ti:sapphire laser to generate violet-blue light ultrashort pulses at a repetition rate of 82 MHz. Our Ti:sapphire laser can produce 100 fs pulses at a wavelength of 780 nm. By frequency doubling in a 1-mm-thick lithium triborate crystal we generate 25 mw violet-blue light in each of two ends from the laser. This laser will make it possible to extend ultrafast techniques to a new spectrum regime.
Output stability of Ti:Sapphire laser
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Stability of Ti:Sapphire laser is researched in the paper. The experimental results and theoretical analysis show that the instability of the output is contributed to the pump stability, the quality of the crystal, and the spontaneous emission photon numbers that enter into stimulated emission modes, which we believe is put forward for the first time.
Poster Session IX: Applications (Metrology and Detection)
Reference systems for laser beam quality and parameter measurements
Xu Dagang,
Chong Ma,
Zhengqiang Guo,
et al.
Show abstract
Three reference systems for the calibration and comparison of beam parameter measurements and beam quality of cw and pulsed lasers at NIM are described. While the cross- sectional power/energy density distribution function of TEM00 He-Ne laser and pulsed Nd:YAG laser are detected by a CCD-camera, the power density distribution function of cw CO2 laser is scanned by a liquid nitrogen cooled TeCdHg detector. Test procedures and evaluations are referred to ISO/DIS 11146 document. From the measured cross- sectional distribution function, the first and second spatial moments as well as the beam width are calculated. The waist location and width are determined by a hyperbolic fit to different measurements of the beam width along the propagation axis. The error evaluation equations for beam parameter measurement have been derived. Measurement agreements using different test methods and instruments are studied. Varieties of beam characteristics and measurement uncertainty for two measuring apparatus are given.
Poster Session VIII: Applications (Modulation)
Kerr lens mode-locking of solid state lasers with thermal lensing
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Aberrative nonlinear transfer matrices are introduced to treat the propagation of laser beam in Kerr medium with thermal lensing. The dependence of mode-locking regions on cavity symmetry and the distance between the fold mirror and the crystal, and the optimal agreement for Kerr-lens mode- locking are discussed with ABCD matrix method.
Poster Session XI: Gas Lasers
Development of red internal mirror He-Ne lasers with near critical concave-convex stable resonators
Xianshu Li,
Yuchuang Chen,
Taoyu Li,
et al.
Show abstract
Basic properties of the concave-convex stable resonator (CCSR) with cavity parameter g1g2 near to 1 are discussed in the infinite aperture approximation. The field distributions and diffraction losses of the low order transverse modes of related resonators with finite aperture are analyzed numerically. The stability of the output power of the lasers with CCSR are studied experimentally. We have made a total of 120 red internal mirror He-Ne lasers with CCSR (g1g2 >= 0.90) whose cavity lengths are approximately 63 cm and the effective lengths of discharge tubes are about 52 cm. Most of the lasers operate with TEM00 stably, and the highest output power is 30 mw. The laser beam waist lies outside the resonator at a distance of 1.0 m from the concave mirror, and the beam divergence is 0.45 mrad. For the TEM00 lasers operate normally, the misalignment angle of the resonator mirrors must be less than 10-5 mrad. The following facts are of particular value. (1) When the resonant frequency spacing between two successive transverse modes of a CCSR (Delta) (nu) is so small that its effect on the competition among transverse modes in the lasers with the CCSR can be negligible, we call such a CCSR near critical CCSR (NCSR). It is observed that even if the round trip total loss (including the transmission loss and so on) of TEM00 is only about 0.2 round trip small signal gain of the laser, and the round trip diffraction loss of TEM00 is only about 0.001, still the laser with the NCSR operate with pure TEM00 stably. It is clear that the mode competition in a laser with NCSR is extraordinarily favorable for TEM00$. (2 While the TEM00 lasers operate normally, the center frequency of every longitudinal mode is stable, its drift per hour is less than 0.1 longitudinal mode spacing (approximately equals 2.4 X 107 Hz). (3) The superradiant transition at 3.39 micrometers is suppressed.
Narrowband mirrors for a new type 1300-nm He-Ne laser
Yaonan Zhu,
Jinyi Miao,
Zhengrong Hu
Show abstract
An approach to the design and fabrication of the mirrors for a new type 1300 nm He-Ne laser is described. In addition to special reflectance at the central wavelength, these mirrors must be not only hard surface with lower loss, but also narrowband, and have lower reflectance at 1150 nm, 1500 nm, 1700 nm, 3390 nm wavelength and so on. Moreover, optical coatings on the mirrors can withstand high temperature.
Chemical Lasers
Nozzle design in cw hydrogen fluoride chemical laser
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Different geometry nozzles used in CW hydrogen fluoride chemical laser are investigated. Four geometry parameters, including throat width; area ratio; axis length and base width are considered. The flow properties, laser outcoupling power and small signal gain (SSG) of a Fabry-Perot resonator are calculated. The results show that when throat width and area ratio increase, the power and SSG peak will decrease in varying degree; they also varied when axis length changed; larger base width is related to lower cavity pressure, and smaller base width is related higher cavity pressure.
Poster Session VII: Applications (Lidar)
Optical System of an imaging CO2 laser radar
Yi He,
Jian Wu
Show abstract
In this paper, an optical system is described that is an optical head of a coherent imaging CO2 laser radar. Discrimination and field of regard limit decided by the optical head itself are discussed. In the experimental laser radar only one continuous wave, single mode CO2 laser is used, and the signals from buildings of 7 km away are obtained with acceptable SNR while the laser output is about 5 w. Furthermore, the comparison between two optical systems based on individually linear frequency modulation (or chirp) pulse compression and frequency modulated continuous wave technique is also introduced in this paper.
Poster Session IX: Applications (Metrology and Detection)
Application of chaos-based signal processing in the laser underwater target detection system
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In this paper, we first demonstrate that the signal received from the laser underwater target detection system may be chaotic through phase space reconstruction, correlation dimension analysis and Lyapunov exponent calculation. Then the result of the correlation dimension analysis is used to construct a neural network predictor which is considered as an approximation of the basic dynamics of the received signal. Finally we introduce a chaos-based detection method and apply it to detect the underwater target. The performance of this new method is superior to that of the conventional method.
Fingerprint fluorescence identifying by using the wideband tunable laser
Liu Huang,
Jinfeng Zhou,
Baolu Yin,
et al.
Show abstract
In this paper, we report the `Ultraviolet-Visible-Infrared Wide Band Tunable Pulse Laser' has been used in identifying the criminal's fingerprint. Different contaminator and secretion of fingerprint in different carrier can be reappeared by illuminating with different wavelength of laser beam. Separating off the laser beam from its induced fluorescence beam with different optical filter, the clear high signal noise ratio fluorescence picture is obtained in a dark background. A series of fluorescence fingerprint picture excited by different wavelength laser light is taken in our Lab. In addition, by using the wide band tunable laser, we test different fluorescence powder or reagent, which sensitivity in different wavelength, a lot of clear fluorescence picture is taken by correspondent wavelength laser beam injection. In this way, the wide band tunable laser offers a wide band of wavelength for develop high sensitivity new fluorescence powder or reagent in chemical field.
Poster Session V: Nonlinear Optical Phenomenon
Discussion of point light source in method of active beacon light in optical phase conjugation
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In some applications of optical phase conjugation in laser beam propagation in the atmosphere, the method of active beam light is used, in which a probe light is transmitted to the target and the reflective light acts as the beacon light. Generally, it is believed that the reflective area on the target must be small enough to be regarded as an unresolved glint, and this limits the application. In this paper, the effect of the reflective area on the optical phase conjugation is discussed, and an experiment by means of nonlinear optical phase conjugation using a ruby laser, Stimulated Brillouin Scattering is an acetone device and a hole to change the reflective area is made. We demonstrate that, the wavefront of light can be restored correctly on the target. In the case of motionless target, the limitation of the reflective area must be satisfied, otherwise the amplified phase conjugated light on the target will return to the probe light source and damage it, whereas, in the case of the remote and high speed moving target, because the reflective place on the target is changed during the period of phase conjugation, the light is only reflected on the target, and so the area may be larger than the limitation.
Poster Session XIV: Optics Components
Experimental study on microdeformation of water-cooled copper mirrors in high-power laser system
Jinan Xia,
Yaoning Zhang,
ZuHai Cheng,
et al.
Show abstract
The surface micro-deformations of a cavity copper mirror, an annular channel copper mirror, a multi-layer copper mirror and a sandwich copper mirror are tested when the mirrors are irradiated by high power laser and cooled by water. The test result shows that the surface deformation values of the multi-layer copper mirror and the sandwich copper mirror are much smaller than the cavity copper mirror and the annular channel copper mirror, and the multi-layer and the sandwich copper mirror can meet the requirement of a high power laser system on very small mirror surface deformation.
Poster Session V: Nonlinear Optical Phenomenon
LD-pumped Q-switched self-frequency-doubling laser
Show abstract
We report here LD pumped Q-Switched LNYAB Self-frequency-doubling Laser. Under 570mW of O.8O2.tm pumping power, the series pulses of O.53j.im green laser with 4.2ns of pulse width and 750W of peak power have been measured . The laser reliably operates when Q—switching rate ranges from CW to 100kHz. The highest peak power was obtained at repetition rate of 10kHz. To our knowledge, it is the first LD pumped acoustooptic Q-switched LNYAB green laser in the world and should be a desirable and reliable pulsed green laser source in the future.
KEY WORDS: Self-frequency-doubling Laser, LD Pumped, LNYAB, Q-Switched
UV laser by frequency doubling within the resonator of a helium neon laser
Can Tao Zhong,
Xin Zhang Li,
Sui Tang Zhao,
et al.
Show abstract
An ultraviolet laser has been developed from the 632.8 nm line of a Helium Neon laser using internal frequency doubling method with a Lithium Iodate crystal. It generates continuous ultraviolet radiation at 316.4 nm. By optimizing the optical components, a folded three-mirror resonator gave out UV radiation up to 1.5 mW.
KTP optical parametric oscillator pumped by the laser with a SBS phase conjugate mirror
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Potassium Titanium Oxide Phosphate (KTP) is a new nonlinear frequency-conversion crystal. It has high nonlinear coefficient, high damage threshold, easily-polished surface, and a broad transparency range. In this paper, the calculation method of angle phase-matching for parametric generation in KTP was presented. The angle phase-matching curve and their characteristics in KTP pumped by 532 nm, 694.3 nm radiation were calculated and analyzed. The propagating principal plane (x-y plane) and 56 degree(s) cut angle to z-axis were selected in our experiment, and the measured results agreed well with the calculated ones. The quality of laser beam is an important factor of affecting OPO threshold fluence and conversion efficiency, so the phase-conjugate technology of Stimulated Brillouin Scattering (SBS) for improving the pump laser beam quality was discussed and applied to the pump laser system. The tuning curves and output energy of KTP OPO pumped by Ruby laser (0.6943 micrometers ), the second harmonic of Nd:YAG (0.532 micrometers ) were measured and compared with the theoretical cases. An important result was obtained that the amplified back SBS light which was employed to pump KTP OPO could greatly reduce the OPO threshold.
Solid State Lasers II
Improving beam profile of LD-Pumped self-frequency-doubled NYAB laser
Shaojun Zhang,
Lianke Sun,
Baoshing Lu,
et al.
Show abstract
By means of studding on the characteristics of phase mismatch of Neodymium yttrium aluminum borate [NdxY1-xAl(BO3)4; NYAB] crystal, a method of improving beam profile of NYAB laser was presented. Because of the exist of little, periodically local shortcomings of NYAB crystal, there were different wave-vector mismatch (Delta) Ks at the different locations of NYAB when a wide incident beam passed through it for SHG. According to the phase matching theory of second harmonic generation, there were different conversion efficiencies at the different locations of the incident beam, resulting in inhomogeneous beam profile of second harmonics. We measured the curves of the SHG efficiencies versus phase mismatch angles of NYAB crystals under cases of different diameters (100 micrometers - 2 mm) of fundamental wave beam. The curves showed that the phase mismatch acceptance angle (Delta) (Theta) m was very small for the thin incident beam when a very homogeneous harmonic beam was obtained, while (Delta) (Theta) m was large for a wide incident beam and the profile of the harmonic beam was not homogeneous.
Poster Session VIII: Applications (Modulation)
Primary investigation of diode-pumped Kerr lens mode-locked Nd:LMA laser
Show abstract
We first demonstrate Kerr-lens mode locking of diode pumped Nd:LMA laser by using an additional Kerr medium of large nonlinear coefficient and fast response time. The laser produces 610-fs, 130-MHz pulses at 1054 nm of laser wavelength and 10 mW of average output power. Kerr-lens mode locking is initiated by mechanical perturbation.
Solid State Lasers II
Nd:YVO4 laser operating at 1340 nm and 670 nm with laser diode pumping
Changqing Wang,
Deyuan Shen,
Zongshu Shao,
et al.
Show abstract
The characteristics of a LD-pumped Nd:YVO4 laser operating at 1340-nm are reported. The maximum output power of 157mW with a slope efficiency of 3 1 .5% has been realized at the incident pump power of 515mW. With a KTP crystal for intracavity-frequency-doubling , 3.6 mW red laser at 670-n.m is obtained. Keywords: LD-pumped, Nd:YVO4, intracavity-frequency-doubling
Optics Analysis
Preliminary theoretical analysis for intracavity new beam lasers
Chengzhi Pan
Show abstract
A preliminary theoretical analysis for intracavity new beam lasers is given according to the point of view of (pi) phase jump at boundaries and the boundary wave theory in this paper.
Poster Session XIV: Optics Components
Investigation of frequency difference stabilization of stress birefringence dual frequency lasers
Shulian Zhang,
Yan Li,
Xiaohong Quan,
et al.
Show abstract
This paper introduces a new method for both producing and stabilizing the frequency difference of a HeNe birefringence dual frequency laser, which employs a PZT to press the intracavity quartz crystal plate according to the difference between objective beat frequency and output beat frequency of the laser.
Solid State Lasers I
Acousto-optically induced single-frequency operation of a Nd:YAG ring laser
Xuxiang Ni,
Zukang Lu,
Bizhen Wu
Show abstract
We describe the mechanism for the nonreciprocal behavior of a traveling-wave A-O modulator. 20 mw single-frequency output for 200 mw pump and 4 (mu) j/pulse are obtained in a ring laser with A-O Q-switch. Finally, we describe a design of monolithic, planar, diode-pumped, single-frequency ring laser with A-O Q-switch.
Optics Analysis
Theoretical model of ultranarrow bandwidth Faraday-Zeeman optical filter at 780nm
Show abstract
Natural rubidium is a mixture of the two isotopes, 85Rb and 87Rb. Taking into account their hyperfine structure, and using a quantum-mechanical treatment of the resonant Faraday effect, we calculate the transmission, central frequency shift and pass bandwidth of Rb 780 nm Faraday- Zeeman optical filter, as functions of magnetic field strength and atomic cell temperature.
Gas and Dye Lasers
Stabilize cw laser power by successive approximation method
Hejun Yao,
Zai-Qing Li,
Renyu Zhang
Show abstract
The successive approximation method was used to stabilize cw laser power. Silicon photodiode is used to monitor the laser output power, and elector-optical modulator is used to control the power. The feedback loop could work in both linear and non-linear states. Thus the time to reach stabilization is shorten and the stability is improved. We experiment with an external He-Ne laser whose own output power is 8 mW and stability is 3%, and obtained stable output power 5.5 mW with stability 0.002%/hour. This kind of laser power stabilizer can also be used in other visible to near infrared laser.
Poster Session XI: Gas Lasers
Key technique in designing electrode for transversly discharged S2 laser
Henry D. Wu M.D.,
Wenyuan Hu,
Zhenghe Sun,
et al.
Show abstract
By the principle of double-layer slice the fabrication of adaptive compound electrodes without thermo-curvature is reported first for transversely discharged S2 laser. The fabrication adopts a wide filmy sealing outlet as well as hard-connection between metals and results in electrode parallelism better than 3 X 10-5 in the temperature range of 273 - 673 K and least dynamic impedance.
Poster Session XV: Optics Analysis
Binary optical resonator for mode optimization in a high-power laser
Show abstract
A novel method for mode optimization of a high-power laser is presented in this paper. A binary optical resonator is formed through introducing binary optical technology into a laser resonator. The traditional spherical mirrors are substituted by binary optical mirrors. Diffraction analyses show that this kind of resonator can construct any modes as desired with a strong ability of mode selecting and optimization. For a high-power CO2 laser, an optimum design of the binary optical resonator is implemented to obtain a fundamental-mode laser output with a uniform intensity distribution.
Studies of circular-polarized ion channel laser with axial guiding magnetic field
Pu-Kun Liu,
Cai-Dong Xiong,
Chang-Jian Tang
Show abstract
The ion-channel laser (ICL), which make use of an electromagnetic instability of an ion-focused relativistic electron beam, is a new form of free-electron laser. In this paper, we introduce a cyclotron electron beam into the ion channel and study the circular polarized ion-channel laser (CPICL) with an axial guiding magnetic field. Using 3D fluid theory, the dispersion relation of the CPICL has been derived. A new kind of radiation mode-ion electrostatic gyro-penitron mode--is found, and the growth rate of this new mode has been obtained for the first time. The effect of axial guiding magnetic field on CPICL is also investigated.
Nondiffraction supershort pulse beam
Peifeng Chen,
You-qing Wang,
Junlin Qiu
Show abstract
Here we present a class of exact pulse solutions of full- wave-equation in free-space. The most important characteristics (faster-than-c propagation and farther-than- J0-beam propagation) of these nondiffraction pulse beam solutions are discussed. The arrangement to create this pulse solution also is considered.
Laser Applications
Studying of interferometer imaging laser radar
Lianhe He,
Jian Wu
Show abstract
We have developed an imaging theory of interferometer imaging laser radar. This method probes a target using a scanning fringe pattern that is formed by two interfering beams of slightly different frequency on the surface of the probed target, then the received signal on the detector includes the information of the probed object. In other words, the scanning fringe pattern formed on the surface of the probed target is modulated by the characteristics of the object. So an image of the target being probed can be generated from the amplitude and phase of the received signs by taking the inverse Fourier transform of this information. This interferometer imaging laser radar can be superior to the mechanical scanning laser radar in the imaging rate and the spatial resolution.
Poster Session XI: Gas Lasers
Technique of wide transmission lines for reducing the impedance of S2 laser head in discharge
Zhenghe Sun,
Henry D. Wu M.D.,
Zhonghua Zhang,
et al.
Show abstract
We select the alloy and glass which match each other in expansion coefficient, which can prevent the corrosive sulfur vapor to make the electrodes and the tube wall, making the transverse discharge electrodes pass through the well sealed tube wall by technique of glass-to-metal high vacuum sealing under the condition of high temperature. The S2 discharge tube of wide transmission lines has been made. The inductance is reduced to 3% and the resistance to 28% compared with existent S2 discharge tube of single- axle transmission lines in the transmission lines.
Poster Session X: Excimer Lasers
Research of the quenched dye lasers pumped by excimer lasers
Show abstract
In this paper, the quenched dye lasers pumped by XeCl and KrF excimer lasers were investigated theoretically and experimentally. Dye laser pulses with duration of 0.8 ns for XeCl laser pumping and 2 ns for KrF laser pumping were obtained.
Poster Session XII: CO and CO2 Lasers
Mini high-repetition frequency sealed-off TEA CO2 laser
Dong Jiang,
Tianjin Hou,
Chongzhong Zheng,
et al.
Show abstract
This paper gives some results and curves from digital calculating about equations of TEA CO2 laser. 3D Chang's electrode was precisely calculated and manufactured to gain well-distributed electric field in discharge space, which is necessary for TEA CO2 laser. A pre-ionization technique used in this laser was described. A gas circulating system was designed to let the laser operate at high repetition frequency (HRF). It is a key technique to extend the operating life of mini high repetition frequency sealed-off TEA CO2 laser. So, an efficient low temperature catalyst is used in this laser. Mini HRF sealed-off TEA CO2 laser can be applied for the military such as rangefinder, tracing, designating, etc. The specifications of this laser are following: mode is TEM00, divergence (whole angle) in far field is less than 4 mrad, pulse energy of TEM00 mode is 87.8 mJ, FWHF is 36.5 ns, peak power of TEM00 mode is more than 0.9 MW, operating frequency is 130 Hz (the maximum frequency is up to 255 Hz and it can operate continuously at 50 Hz), it's operating life is more than 1 X 107 shots.
Ccharacteristics of superpulse discharge for a high-power fast-axial-flow CO2 gas laser
Show abstract
The characteristics and mechanism of superpulse discharge for high power FAF CW CO2 lasers are based on the rate equation theory. The mathematical modeling analysis of superpulse discharge especially considering the influence of turbulence and convection is simulated on the computer. Detailed mathematical modeling curves which demonstrate how superpulse operation is employed around population inversion, gain and injection power density are obtained. The results are relevant for superpulse CO2 lasers.
Poster Session IV: New Solid State Laser Materials
Investigation of "green problem" in a LDA-pumped, intracavity-frequency-doubled Nd: YVO4 laser
Show abstract
Low-frequency amplitude instabilities, called `green problem', were observed in a laser diode array pumped, intracavity-frequency-double Nd:YVO4 laser under certain experimental conditions. The results of an experimental and theoretical investigation of these instabilities are described, and the theoretical analysis agrees fairly well with the experimental observations.
Solid State Lasers II
Intracavity doubling of cw LD-pumped Nd:S-FAP laser with KTP
Shaojun Zhang,
Lianke Sun,
Qingpu Wang,
et al.
Show abstract
In this paper the lasing performance of a intracavity doubling of CW diode-laser end-pumped Nd3+:Sr5(PO4)3F, Nd:S-FAP, laser with KTP crystal was reported. We measured the single output performance of the green laser: the pumping threshold was 8 mW; when the pumping light of 210 mW was absorbed, the maximum single output at 529.7 nm was 4.4 mW (TEM00 mode), corresponding to a total conversion efficiency 2.1%. The comparison between experimental results and theoretical calculation was also discussed in this paper.
Poster Session XV: Optics Analysis
Design considerations for monolithic unidirectional planar ring oscillators
Show abstract
In this paper, the characteristics of monolithic unidirectional planar ring oscillator (PROs) are analyzed, and design criteria for PROs with low thresholds and large nonreciprocities are expounded on the basis of the eigenpolarization theory of monolithic nonplanar ring oscillators. A Nd:BGO PRO is designed to take advantage of its large Verdet coefficient.
Laser Applications
Diode-pumped birefringent dual-frequency Nd:YAG laser for absolute distance interferometry
Mingxing Jiao,
Shulian Zhang,
Jinwen Liang
Show abstract
Proposed for the first time to our knowledge is a novel scheme of a diode-pumped birefringent dual-frequency Nd:YAG laser, whose resonant cavity contains a piece of versatile element: crystal quartz Fabry-Perot etalon, acting as a mode selector and a mode splitter as well as a reference of stabilizing the frequency-difference. The laser will oscillate simultaneously in two linearly and orthogonally polarized modes spaced 5-GHz, corresponding to a synthetic wavelength of approximately 60-mm, which is well suitable for absolute-distance interferometry. The stabilization of the frequency-difference is also considered in detail.
Poster Session I: High-Average-Power Solid State Lasers
Investigation of the beam quality improvement of high-average-power solid state lasers
Show abstract
First, the factors that degrade the beam quality of high average power Nd:YAG lasers are analyzed. Especially the optical asymmetry of Nd:YAG rod under high power pumping is experimentally verified. A novel resonator--the four mirrors resonator is introduced, which has two mechanisms of beam quality improvement: the image-rotating and interference filtering. Experimental results show obviously the effect of beam quality improvement of the new resonator compared with its equivalent plane-parallel resonator under the same pumping power.
Poster Session XV: Optics Analysis
Compound cavity optical parametric oscillator
Show abstract
We report a new type of optical parametric oscillator (OPO) cavity, i.e. a compound cavity OPO, and present its time dynamics based on a mathematical model. Both the numerical simulation and experimental results show that this type of cavity is superior in that its threshold is lower than that of a simple narrow-band cavity with dispersive elements, and its external efficiency is increased while its narrow linewidth remains nearly the same across the tunable range of the nonlinear crystals used.
Chemical Lasers
Effect on the cw hydrogen/deuterium fluoride chemical laser with different diluents
Show abstract
The He is usually used as diluent in combustion cw hydrogen/deuterium fluoride (HF/DF) chemical lasers. Sometimes, the N2 is also used as diluent in cw HF/DF chemical laser, because N2 is more cheaper than the He. It was thought that the efficiency of cw HF/DF laser with N2 diluent was lower than that of HF/DF laser with He diluent since the molecular weight of N2 is heavier than that of He. In this paper, the performance of cw DF chemical lasers with He and N2 diluent was investigated. The small signal gain, power spectral distributions, cavity pressure, power and efficiency of DF lasers with these two diluents have been calculated using a finite-difference technique for the numerical integration of the steady and unsteady Navier-Stokes equation with reactive flow (compressibility scaling method-CSM), which was developed in the chemical gas dynamic laboratory of the state institute of applied chemistry in Russia. The numerical results show that the efficiency of DF lasers with N2 diluent is not lower than that of the lasers with He diluent.
Poster Session IV: New Solid State Laser Materials
LD-pumped red lasers and its application in Cr:LiSAF laser
Show abstract
We report here the Nd:YAP-KTP red laser pumped by LD for pumping Cr:LiSAF tunable laser. Using a CW 802 nm LD of 3 W, 670 nm CW red laser of 95 mW has been measured. The red laser is used to pump Cr:LiSAF laser, and over 4 mW CW laser from the Cr:LiSAF laser has been measured. They are to our knowledge the first Nd:YAP-KTP red laser pumped by LD and the first Cr:LiSAF laser pumped by Nd:YAP-KTP red laser.
Prelase A-O mode-locked Cr:LiSAF laser pumped by flashlamp
Zhenlin Wang,
Aihua Wang,
Qiang Guo,
et al.
Show abstract
In this paper, we report the properties of flashlamp-pumped Cr:LiSAF laser operating both in Q-switched and modelocked modes. Stable Q-switched pulse with energy of 85 mj and pulse duration of 50 ns (FWHM) is obtained. Reliable ps pulse train is observed by prelase A-O modelocking and the pulse duration is 80 ps (FWHM). Wavelength tuning is realized from 810 nm to 890 nm by a two-plate crystal quartz birefringent filter (BRF, d1:d2 equals 0.5:1).
Poster Session III: Ti:Sapphire Solid State Lasers
Studies on pulsewidth charcteristics of a ring cavity mode-locked Ti:sapphire laser
Guizhong Zhang,
Wanghua Xiang
Show abstract
Our paper gives the results of pulsewidth characteristics of a self modelocked ring cavity Ti:sapphire laser which is simulated numerically by means of split step Fourier method. By taking account of the Kerr-lens effect quantitatively, we have been able to show that the Kerr-lens effect plays a dominant role in the buildup of ultrashort pulse and its interplay with the total dispersion of the cavity eventually determines the pulse duration.
Longitudinally pumped pulsed Ti:S laser
Show abstract
Our pulsed Ti:S laser is abaxial longitudinally pumped by a frequency double YAG laser with VRM unstable resonator, the Ti:S crystal is Bi-Brewster-cutting. The single output energy of the Ti:S laser is over 130 mJ at 1 Hz and over 110 mJ at 10 Hz, the efficiency is 39.6% and 36. 7% respectively, the tunable range is 0.723 approximately 0.996 micrometers with only a pair of flat mirrors, the output energy in the two ends is 1/10 of that in the center wavelength. We discuss the effect of choice of the crystal size, the angle (alpha) (between the pump beam and the cavity axis) on efficiency. We suggest that the high absorptivity, high FOM value of the crystal bring high output and high efficiency when longitudinally pumped by a flat-top laser beam. We also show the scheme of our Ti:S laser and our broad band transmitted curve of reflective mirror.
Poster Session II: Solid State Laser Technology
Square wave pulsewidth variable solid state laser
Liu Huang,
Yu Zhao,
Pulei Sun,
et al.
Show abstract
On the basis of the rate equation of laser oscillation, we study the capable of square wave output of solid state laser in temporal domain. By means of the smooth cavity dumping, the reduce of output loss compensated the photon decrease in cavity. In experiment, we use two sets of avalanche transistor chains to control the functional voltage which applied on the Pockels cell in order to get a uniform and pulsewidth variable square wave pulse laser. Compare with the traditional Gaussian pulse, the pulsewidth variable square wave laser pulse has some advantages in waveform, polarization, energy uniformity. So it can be used in high power, high conversion efficiency without damping rods, mirrors and crystals.
Poster Session VI: Applications (Internal Confinement Fusion)
Investigation on coaxial double-pass main amplifier in high-power laser fusion driver
Show abstract
We have constructed coaxial double-pass amplifiers with individual beamlet aperture of 20 cm in a 2 X 2 array architecture. Each element contains six phosphate glass disks. The amplifier consists of two pairs of disk amplifiers, each six deep, that share a common central flash-lamp array. The central array is expected to be more efficient for the pumping of disks, thereby raising the amplifier storage efficiency. A particular coaxial double- pass amplification optical scheme was designed. The input and output beam are performed by spatial filter. Technique advantage is avoidance of large aperture electric optical switch. In this paper we theoretically calculate population inversion variation in multipass amplification and the gain of multipass amplification. The experimental results are in agreement with the theoretical calculation.
Gas and Dye Lasers
High-power excimer laser and application
Show abstract
A high power XeCl and KrF excimer lasers pumped by an intense relativistic electron beam have been developed. The pump power density ranges between 1.5 to 2.0 MW/cm3. The maximum output energy of 136 J with the peak power of 1.5 GW is obtained for the XeCl laser. In KrF laser case, the maximum output energy is 157 J and the peak power 2.0 GW. The UV laser interaction with some materials has been studied by this excimer laser.
Poster Session IX: Applications (Metrology and Detection)
Laser inducement of agricus bisporus I
Show abstract
Using different power, different dosage's He-Ne laser (632.8 nm) and semiconductor laser (805 nm) to irradiated mycelia of four Agricus bisporus strains. And using no irradiate strain as contrast. Picking out some mycelium from irradiation position and then transfer them into Potato Dextrose Agar culture medium, culturing 12 - 15 days. We use the polyacrylamide slab gel electrophoresis to examine the esterase (EST) isozymes of mycelium. We could find from the result that laser irradiating could not change the Rf of main bands (F&s zones) of mycelium EST. However, 20 mw He- Ne, 10 minutes irradiation could not only raise the activity of EST distinctly, but also increase the numbers of enzyme zone of M zone, the difference between the semiconductor irradiation of 140 mv, 10 minutes and 20 mv, 10 minutes are not remarkable. And the irradiating effect of He-Ne laser is better than that of semiconductor laser.
Poster Session VII: Applications (Lidar)
Transmission loss in extinction test
Qiwan Fang,
Zhaohui Chen,
Weiyi Chen,
et al.
Show abstract
The problems in the extinction test for transmission losses are analyzed. According to laser transmissions theory, the laser rangefinder's comprehensive range ability equation and the transmission loss equation are derived. And the relationships between transmission losses and visibility are verified.
New determination equation for visibility
Qiwan Fang,
Jionghui Rao,
Zhinxiang Ying,
et al.
Show abstract
In this article the problems in the range index are analyzed. The way to determine visibility is put forward. Extinction determination equation for visibility is derived. And it is applied in practice, which verifies the determination equation is functional and effective.
Poster Session XII: CO and CO2 Lasers
New kind of efficient preionic long life time TEA CO2 laser
Show abstract
In our work, the design and performance of a new kind TEA CO2 laser is reported. It was preionized by ultraviolet (UV) from surface corona discharge. A BN ceramic structure was employed as an assembly of resonators. The output energy of 143 mJ, the pulse duration of 50 ns, the transverse mode of TEM00, the repetition-rate of 50 Hz, the divergence of only 4 mrad was obtained. Comparing with UV bare-spark- preionized (BSP) TEA CO2 lasers, it was found that (1) the uniform of the main electrode discharge was improved, (2) the repetition-rate was improved from 30 Hz to 50 Hz, (3) the input energy was four times lower than that of BSP TEA CO2 laser under the same output energy, (4) the lifetime reached 106 pulse, (5) the stability of resonator was improved, the output energy eliminated only 14% after 3.5 hours operation. The performance was improved because the intrinsic efficiency of surface corona preionization was four times higher than that of BSP one, the corona discharge was very uniform and photodissociation processes involved in BSP were avoided. The extremely low thermal-expansion of BN minimized the misalignment, so the high reliability can be obtained.
Poster Session VII: Applications (Lidar)
Backscatter of basic target for CO2 laser
Show abstract
In this paper the expansion, transmission and distributed function of antenna are analyzed, and the optimum characteristics of antenna is obtained. If we accurately calculate intensity of backscatter for target, the sign of light facula and distribution of energy have to be considered on surface of the target. We had built swapping relation equation between coordinates of the radar and object space of the target, using computer the pseudo-color imaging of the basic target are produced by the equation.
Poster Session IX: Applications (Metrology and Detection)
Measurement of ultrashort pulse with fundamental wave by computer
Show abstract
A new technique of measuring light pulse with fundamental wave information is presented in order to surmount the difficulty of phase matching of tunable laser in second- harmonic wave method. The expressions of upper-envelope of interference correlation function of fundamental pulse are derived for Gaussian and hyperbolic secant pulse shapes. It is pointed out that the width of the envelope at ordinate of 1.72 (for Gaussian) and 1.76 (for sech) equals to FWHM of second-order intensity correlation curve for above shapes respectively. It is not necessary to double frequency for this method, the arrangement of experiment is simpler and the ratio of signal to noise is greatly raised. The measurement of single pulse is simply discussed.
Poster Session XIII: Chemical Lasers
Laser mode control using an inverse external cavity
Chun-Ching Shih
Show abstract
It was found that the odd (anti-symmetric) modes of a laser cavity can be effectively suppressed by using a lossy inverse external cavity coupled to the main cavity. This mode-control technique is particularly useful for high- aspect-ratio laser resonators used in, for example, waveguide lasers and laser diode arrays. The effect is analyzed in the limit of geometric optics.
Poster Session XVI: Miscellaneous Topics
1059 and 1328-nm LD-pumped Nd:S-FAP solid state laser
Lianke Sun,
Shaojun Zhang,
Shengzhi Zhao,
et al.
Show abstract
In this paper we introduce a new laser crystal -Nd3+:Sr5(PO4)3F, Nd:S-FAP, and present its optical and physical characteristics. Based on the experiment lasing performance of CW LD pumped Nd:S-FAP crystal is reported here: the threshold and slope efficiency of 1059 nm Nd:S-FAP laser pumped by CW LD at 805 nm are 7 mW and 41%, and that of 1328 nm Nd:S-FAP laser are 19 mW and 35%. The comparison between experimental result and theoretical calculation is also discussed in this paper.
Diode-laser-side-pumped Nd:YAG Q-switch TEM00 laser
Weimin Wang,
Chenglong Yang,
Chun Tang,
et al.
Show abstract
The diode laser side pumped E-O Q-switch Nd:YAG laser was described that produced energy 0.36-mJ/pulse, 7-ns pulse width, pulse repetition rates 50-Hz, TEM00 mode. The laser has a zigzag slab geometry, side pumped with a quasi- CW 15 W diode bar. We used a 1.1% Nd:YAG Brewster-cut seven- bounce thin trapezoidal slab that was 1.2 nm thick. Using a cylindrical lens (f equals 1.6 mm), it made the diode laser couple in the slab. The laser resonator was a plane-concave cavity, radius of mirror curvature was 3 m. The cavity length was about 20 cm. The plane output mirror transitivity was T equals 0.1. We decided to the beam quality M2 equals 1.1. Q-switch laser slope efficiency was 19%.
Some challenges in ultrafast intense laser science
See-Leang Chin
Show abstract
Some challenges in ultrafast intense laser science will be discussed. We introduce the possibility of lightning control based on the self-focussing and channeling phenomenon. This leads us to discuss various basic scientific and technological problems which include the laser source technology, high harmonics generation, multiphoton and tunnel ionization, stabilization and dissociation in atoms and molecules, etc. The propagation of these pulses (self- focussing, supercontinuum generation, transport of high intensity pulses to long distances etc.) and applications (intense VUV and X-ray source, medical sterilization, control of lightning etc.) will also be discussed.
Experimental investigations of uniformly pumped Nd:YAG slab laser
Fathi Elmansuri,
Xuedong He,
Lian Yan,
et al.
Show abstract
The fluorescence from a Nd:YAG slab with dimensions 6 X 22 X 202 mm3 showing a uniform distribution of pump light in the slab was observed. The refractive power of the slab under this condition was measured. As high as 547 W of average output power with the slab in an on-axis one dimension unstable resonator configuration has been obtained.
Thermally induced depolarization in Nd:YAG slab geometry
Xiaoyuan Wu,
Xuedong He,
Lian Yan,
et al.
Show abstract
The thermally induced depolarization of a zig-zag slab geometry Nd:YAG crystal with dimensions 6 X 27 X 202 mm3 uniformly pumped in a cavity was measured under different pumping power levels. Analysis of results with the calculation by an expression developed from argument and from the results of numerical model are presented. The deformed He-Ne beam spot passed through the pumped slab showing the deformed slab cross section and end effect resulting in the thermally induced depolarization are obtained. The depolarization in our case has resulted substantially from ends effect.
New beam lasers
Show abstract
A new suggestion that there is a phase jump of (pi) in the boundary wave is put forward in this paper. This suggestion may be a supplement of Huygens-Fresnel principle. Based on this new suggestion, a series of new beam was invented, both outside and inside laser cavity. Especially, a new CO2 laser with equivalent beam quality factor M2 < 1 is achieved. it can be considered as the result of some controllable nonlinear self-focusing, and the physical background of deformed quantum mechanics.