Proceedings Volume 4267

Solid State Lasers X

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Proceedings Volume 4267

Solid State Lasers X

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Volume Details

Date Published: 16 April 2001
Contents: 5 Sessions, 25 Papers, 0 Presentations
Conference: Photonics West 2001 - LASE 2001
Volume Number: 4267

Table of Contents

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Table of Contents

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  • Novel Devices
  • New Materials
  • Solid State Lasers
  • Solid State Technologies
  • Poster Session
  • Novel Devices
  • Poster Session
Novel Devices
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Compact diode-pumped Yb:YAG slab laser
Alexander E. Mandl, Daniel E. Klimek
We have developed a diode end-pumped Yb:YAG slab laser which operates at 10Hz. The device uses a novel endcap design which allows simplified coupling of the 940nm Q-CW InGaAs diode pumps and improves the excitation uniformity of the Yb:YAG. We have achieved 500mJ of laser output operating in the long pulse mode (2ms pulses) in excellent agreement with kinetic code calculations. Very little difference in laser performance between long pulse and Q-switched operation has been observed. To date, Q-switched measurements have been performed at energies to 6OmJ with pulse lengths of 6Ons.
Design and characterization of a 12-channel dual-wavelength fiber-coupled laser system
A compact, ruggedized 12-channel, dual wavelength, fiber-coupled laser system was designed, assembled and tested to support fiber injection experiments. A flashlamp pumped, Q-switched, Nd:Cr:GSGG laser, operating at 1061 nm was assembled and characterized. To optimize the laser for fiber injection, a stable, multimode, Polarization Output Coupled (POC) resonator design was utilized. The design did not use any active cooling and was ideal for low duty cycle applications requiring no more than one shot every 30 seconds. The laser output was frequency doubled to 530 nm utilizing a Type II interaction in a KTP crystal. A nonlinear conversion efficiency of 56% was obtained. Two beam splitting and fiber injection modules, one for each wavelength, were utilized to transform the single laser input beam into six parallel fiber channels. Four of the channels were provided for high output energy and two for low energy monitoring. In addition to the 12 fiber optical outputs, full aperture 1061 nm and 530 nm output ports were provided with independent energy adjustments. The entire laser system was packaged into a rugged 0-ring sealed aluminum housing to maintain cleanliness. The housing measured 18" x 22" x 2.75" and weighed 43.5 pounds. The capability to externally select wavelength, beam format (fiber coupled or full aperture) and output energy was provided. This was to preserve internal cleanliness and facilitate system operation in dirty environments. Alignment strategies and performance results including laser efficiency, far field beam divergence, nonlinear conversion efficiency, fiber-to-fiber energy uniformity, and fiber output intensity profiles will be presented.
All-solid-state and compact multiwavelength laser
Wei Zhao, Sanghong Zhao, Guofu Chen, et al.
Multi-wavelength lasers from near-infrared to deep-ultraviolet range, 532, 266, 830, 415, 208nm, were developed in one all-solid-state laser system for the first time to our knowledge. The laser system was pumped by a diode-Q-YLF laser, a Ti:sapphire laser and the nonlinear SHG crystals LBO and BBO were used to generate different wavelengths. Maximum average powers (repetition rate 1khz) of 1.8W at 266nm, 1.1W at 830nm, 380mW at 415nm, and 39mW at 208nm were obtained when the pumping power was 3.8W. Main characteristics of this system are presented.
New Materials
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High-power operation of continuous-wave Cr4+:forsterite lasers: excited state absorption versus crystal temperature
We study temperature and pump power dependence of fluorescence in Cr4+:forsterite crystal. We find that the luminescence yield has a strong temperature and pump power dependence. We also observe two-photon fluorescence induced by continuous wave pumping of Cr4+:forsterite and study its temperature behavior as well. The obtained results are used as a guidance to construct high-power, high energy femtosecond Cr4+:forsterite oscillator.
New generation high-power rare-earth-doped phosphate glass fiber and fiber laser
Ruikun Wu, John D. Myers, Michael J. Myers
High power, high brightness fiber lasers have numerous potential commercial and military applications. These lasers offer unique flexibility as they may be coherently combined to provide a potential multi-kilowatt laser source and integrated delivery system. Fiber lasers with cladding pump designs represent a new generation of diode pumped configurations that are extremely efficient, have single mode output and may be operated with or without active cooling. They have a number of novel or unusual attributes, stemming from the fact that they represent the extreme case of a long gain length thin laser cavity. Reports indicate that over 100 watts of TEMoo CW output power are readily demonstrated from current cladding pumped fiber laser designs.
Highly efficient polycrystalline Nd:YAG ceramics laser
Jianren Lu, T. Murai, K. Takaichi, et al.
Highly efficient Nd:YAG ceramic laser at 1064 nm was demonstrated. Using 1 W LD end-pumping scheme, with 883 mW pumping, 499 mW 1064 nm CW laser output has been obtained corresponding to an optical to optical efficiency of 56.5%. High power CW Nd :YAG ceramic rod laser was also demonstrated. The maximum output power of 62.5 W with was obtained at 1064 nm. The optical to optical conversion efficiency is 21.6%.
Evaluation of scaling output power of diode-end-pumped vanadate lasers
The evaluation of pump capability and scaling output power of vanadate lasers are presented in this paper. With the consideration of thermal fracture limitation and fundamental mode operation, systematic investigations of vanadate crystals are conducted to scale the output power of diode-end-pumped lasers to higher levels. Based on the limitation of pump power, the input-output characteristics and beam propagation factor of vanadate lasers are optimized with the knowledge of thermal effects. The theoretical analyses provide a good prediction to the experiment. A practical example of a single endpumped vanadate laser is demonstrated with cw output powers of 9.8W in TEM00 mode and 12.4W in multimode.
Solid State Lasers
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Diode-pumped regenerative amplifier delivering 100-mJ single-mode laser pulses
Vincent Bagnoud, Jacques Luce, Laurent Videau, et al.
We report on a side pumped Nd:Phosphate laser regenerative ampli er that delivers up to 100 mJ laser pulses in a single TEM mode. The laser beam is mode matched to the ampli cation medium thanks to an intra-cavity fused silica phase plate for mode shaping and a telescope for adjustment of the beam mode to the ampli cation rod section, so that most of the energy stored in the rod is transferred to the laser pulses. As a result of the good overlap and the low losses, an optical to optical conversion eÆciency up to 10 % was measured for a pumping current of 80 A and above 100 mJ output pulses.
Laser performance of Cr2+-doped ZnS
Keith Graham, Sergey B. Mirov, Vladimir V. Fedorov, et al.
Laser properties and spectroscopic characterization of diffusion doped Cr2+: ZnS crystals synthesized by chemical transport reaction from gas phase are reported. Lasing was realized with a threshold of 170 ?J and slope efficiency of 9.5 % with respect to the 1.5607 ?m pump energy, in a hemispherical cavity. Low doped samples (3-4 cm-1 at 1.7 ?m) of 1.7 mm thickness were utilized. The 1.5607 ?m excitation was realized with a D2 Raman cell pumped in a backscattering geometry by the 1.064 ?m radiation of the single frequency Nd:YAG laser. Maximum output energy reached 100 ?J. Lasing in the hemispherical cavity was achieved with output couplers R2.36?m=80 % and 90 % and radius of curvature 20 cm. Absorption cross section was estimated from spectroscopic measurements and was in a good agreement with saturation data (?abs.= 0.80x10-18 cm2) calculated with the modified Frantz-Nodvik equation for a four level slow absorber. Findlay Clay losses were found to be about 14%. Selective cavity experiments were performed in a hemispherical cavity with a CaF2 prism as the dispersive element. A tuning range of 2.05-2.40 ?m was realized, limited by the spectral range of the output coupler of the selective laser cavity.
Pump uniformity study of a side-pumped DPSS laser
Jianhui Gu, Siu Chung Tam, Yee Loy Lam, et al.
We reported pump uniformity study of a side-pumped DPSS laser, which produced CW output of 30 W with a proper uniform pumping. An JR camera was employed to study the pump energy distribution as well as the thermal effect inside the laser crystal. Theoretically simulated energy distributions were compared with the experimentally measured JR images. Jt is found that the JR imaging technology is an effective method to study pump uniformity of side-pumped DPSS lasers, and uniform pumping is very essential to achieve a good beam quality and a wider stable operating range for high-power DPSS lasers.
Solid State Technologies
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Highly efficient high-brightness diode stacks side-pumped Nd:YAG rod laser
Shuichi Fujikawa, Keisuke Furuta, Koji Yasui
We have proposed a highly efficient and high-brightness quasi-cw Nd:YAG rod laser with a novel-side-pumping design using micro-lens free diode-stacks. We demonstrated 320-W output power with 28-% electrical-to-optical efficiency, which is, to our knowledge, the highest efficiency reported for diode-pumped solid-state lasers. We also achieved the beam quality of M2 =4 with the output power of 500 W by introducing a bifocusing compensation resonator. The corresponding electrical-to-optical efficiency was 20 %.
Tunable distributed-feedback sol-gel dye lasers
XiaoLei Zhu, Sio Kuan Lam, Dennis Y. Lo
Distributed feedback (DFB) solid state dye laser with optically induced periodic gain modulation is a compact laser capable of tunable lasing from the UV to the near JR. Using E377 dye-doped sol-gel silica as gain medium, pumped by a Q-switched laser at 308nm, DFB laser emission in the near UV has been successfully demonstrated. Wavelength tuning from 367nm to 383nm with an emission spectrum linewidth of 8Opm has been realized by varying the pump beams intersection angle, and a slope efficiency of 4.4% has been obtained. Similarly, DFB laser emission tuning has also been realized by varying the refractive index of the gain material. Wavelength tuning has been first achieved by temperature variation of the R6G doped poly(methyl methacrylate) and sol-gel silica bulk in the DFB structure. Tunable output from 573nm to 556nm has been demonstrated. The thermal coefficients of the refractive index of sol-gel silica have been measured for the temperature ranges of 21°C to 43°C and 43°C to 58°C.
Simple high-efficiency diode-pumped Nd:YVO4 slab laser
Prasanta Kundu, Joseph S. Chakkalakal, Chandrashekaran Natarajan
A diode laser-pumped Nd: YVO4 slab laser with side pumping configuration is presented in this paper. A folded confocal resonator configuration produces a maximum of 7mJ multi mode laser energy for the output coupler reflectivity of 70%. The optical-to-optical conversion efficiency of 29.86%. and slope efficiency of 35.6% are reported in this investigation. Straightthrough resonator arrangement and directly side-coupled technique provjde high efficiency with design simplicity of this laser.
Poster Session
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Passive Q-switch and mode-lock modulators for the diode-pumped Nd:hosted solid state lasers
Junewen Chen, Horng Chang, Duen-Kai Chen, et al.
Four kinds of currently available Nd:hosted laser passive Q-switch and mode-lock modulators: plastic dye sheet, LiF:F2- color center crystal, Cr4+:YAG crystal and RG1000 colored glass filter were investigated in detail for the diode-pumped Nd:hosted solid state lasers. Nd:YVO4 lasers, ?-Nd:YAG lasers as well as conventional Nd:YAG lasers, Nd:Glass lasers had been set up for investigations. Detailed analyses of the mode-locking effect in combination with Q-switching were provided. Interpretation given based on the characteristic features of the materials, like saturation intensity and relaxation times. The results explained at hand of adequate equations derived with respect to the relevant physical parameters of the materials.
Starting of self-mode-locking solid state laser
Qirong Xing, Ning Zhang, Weili Zhang, et al.
A dynamic equation of passive mode locking with the equivalent fast saturable absorber in self-mode-locked solid state laser is presented. With the linearized rate equations , we obtained the self-starting condition .Furthermore, the relation between the growth rate of coupling modes and the starting factor is presented. The theory is in good agreement with the experimental results obtained by other researchers.
Mode-locking of flashlamp-pumped Nd:YAP laser using solid state saturable absorbers
Vaclav Kubecek, Andrej Dombrovsky, Jens Biegert, et al.
We report on application of semiconductor quantum well saturable absorber as a passive mode-locker in flashlamp pumped Nd:YAP laser. In passive regime of modulation, reproducible single trains containg about 10 pulses were generated with probability higher than 90 %. The single pulse duration was ~ 50 ps with a nearly Gaussian spatial profile. Energy ofthe whole train was 3 mJ. In active passive-regime using an additional acousto-optic modulator the probability of generation of mode-locked trains increased to 98 %.
Development of a picosecond Nd:YLF amplifier for laser-Compton x-ray generator
Yasuhiro Okada, Masafumi Yorozu, Jinfeng Yang, et al.
A multipass amplifier for a picosecond Nd:YLF laser was designed and developed for the light source of a laser-Compton X-ray generator. The developed amplifier was constructed of a water-cooled Nd:YLF rod (20mm long, 4mm in diameter) and a pair of quasi-CW laser diodes (peak power 1kW) with optical systems for rod pumping. The amplifier was operated as a laser with a generated output energy of 218mJ and slope efficiency of 31% at 10Hz. We then operated the laser as an amplifier with 0.4mJ, at 10ps, 1047nm seed light. The amplified energy was 4mJ in the single-pass configuration and 3OmJ in the double-pass configuration. The experiment result was compared with the theoretical result derived from the Frantz-Nodvik equation. The results agreed well in the lower energy region but diverged in the higher energy region.
Miniature Cr4+:YAG Q-switched repetitive operation conductive-cooling (Ce, Nd):YAG laser: I. Theoretical analysis
Xiaoyan Chen, Yuzhi Wang, Gang Zhao
In this paper a theoretical analysis for optimization of the miniature Cr4+ YAG passive Q-switched, repetitive operation, conductive cooling (Ce,Nd) YAG laser has been made The critical threshold energy curve, analytical expression oflaser efficiency and single pulse region were obtained This analysis was useful in guiding developing a miniature Cr4+.YAG passive Q-switched, repetitive operation, conductive cooling (Ce,Nd) .YAG laser which is now being used in airborne height-finders
Miniature Cr4+:YAG Q-switched repetitive operation conductive-cooling (Ce,Nd):YAG laser: II. Experiments
Xiaoyan Chen, Yuzhi Wang, Gang Zhao
Upon the theoretical guiding and some related experimental as well as theoretical results concerning the project, a miniature Cr4+:YAG Q-switched, repetitive operation, conductive cooling(Ce,Nd):YAG laser was developed up to practical application level. the laser rod was fixed at a pedestal with a contact angle of about 1200 compacted with an intersecting circles pump cavity, together with a plane-parallel resonator. The main specifications of this laser are listed below. Laser output energy:single pulse:5~3OmJ Repetitive rte:2~5pps Pulse-width:?5ns Beam divergence:3~5mrad Limitation of ambient temperature :-40°C~60°C Dimensions:130x30x 30
Design of intersectional circle cylinder pump cavity with conductive cooling
Yuzhi Wang, Xiaoyan Chen, Gang Zhao
Elliptical cylinder pump cavity is widely used in solid state lasers. But because of the complexity of its technology, a replacement is always pursued. Intersectional circle cylinder pump cavity is a kind ofcavity similar to the elliptical cylinder one, and several investigators have used it. However, theoretical analysis for it is rather scarce. In this paper, the authors presents a design for this kind ofcavity, suitable for miniature lasers. The most importantjob in the design is to explore the optimum couple oflight energy, so as to get the highest efficiency ofaccumulating light. For miniature conductive cooling devices, the construction ofpump cavity is schematically shown in Figure 1. Principal parameters needed to define are: the dimension between the pumping lamp and the laser rod 2C; the distance ofthe cutted height h (see Figure 2) and the radius R of the intersectional cycle cylinders. By theoretical analysis, a method ofdesignning this kind ofcavity has been performed. The results are listed below: h=0289R,R=2C.
Nucleation-damage of laser rod
Yuzhi Wang, Gang Zhao, Xiaoyan Chen
A phenomenon called "nucleation-damage" was observed in the laser rod made of dual-doped laser crystal (Ce, Nd): YAG. This damage occurred mainly iii the zone ofthe rod nearby the total reflector. A replacement of the plane-reflector with a rectangular prism or a TIR ( total internal reflecting ) prism diminished this damage considerably.
Proposal method for in-situ measuring dip-angle of curved railroad
Yuzhi Wang
A proposal method based upon laser technique for measuring dip—angle of curved railroad is presented. In this method, a miniature solid-state laser is used as a pointer whose direction can be persisted permanently perpendicular to the earth by a simple gyroscope. The dip-angle of railroad is calculated by the readings of the pointer.
Novel Devices
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Photochemical and lasing properties of pyrromethene dyes
Guilford Jones II, Oksana Klueva, Satish Kumar, et al.
Pyrromethene dyes, particularly PM 567, have been studied in liquid media using various spectroscopic techniques. Photodecomposition of dyes was monitored by absorption and fluorescence spectroscopy. In laser flash photolysis experiments on dyes in liquids, phototransients were observed (microsecond time domain) that included dye triplets and at least one other transient of the radical or radical-ion type. Experiments included product studies that allowed identification of major products of photodegradation; an assessment of the effectiveness of known stabilizing additives such as DABCO and butazate was also conducted. Purposes of the work included definition of the roles of energy and electron transfer mechanisms in dye photodegradation and the effects of oxygen or additives in dye media.
Beam-quality measurements on solid state dye lasers using nonconfocal unstable resonators
Jeffrey A. Russell, Dennis P. Pacheco, Henry R. Aldag, et al.
This paper reports on a systematic study ofthe beam quality ofsolid-state dye lasers for different resonator designs. The resonators investigated include: multimode stable, hard-edge unstable, and unstable with a graded-reflectivity mirror (GRM) output coupler. The purpose ofthe work was to investigate the conditions under which good beam quality can be achieved, and to examine the possible trade-off between beam quality and energy extraction efficiency. Beam quality was quantified through conventional M2 measurements. A hard-edge unstable resonator of magnification ?2.5 produced a beam ofM2 ?11 - 12 at a PRF of 2Hz and a pump flux of 5 MW/cm2. The value increased to ? 18 — 19 at a pump flux of2O MW/cm2. This can be compared with an M2 of ? 140 - 150 with the multimode stable resonator. Preliminary measurements with the GRM resulted in M2 values of ? 5 to 6 at 5 MW/cm2.
Poster Session
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Cr,Tm,Ho: YAG laser amplifier
Bjoern I. Lange, Benno Radt, Gereon Huettmann
Among other applications, Q-switched, single-mode and high energy Ho:YAG lasers are useful tools in temperature- jump experiments designed for biophysical research. But if pulse energies of 200 J at one microsecond pulse widths or shorter are to be generated in a single oscillator, the damage threshold of the optical coatings is likely to be exceeded. Experiments with an oscillator/amplifier system show that the saturation fluence of Cr,Tm,Ho:YAG amounts to 2.3J/cm2 and that a small signal gain coefficient of 0.15/cm can be obtained at moderate pump densities. This suggests the use of extracavity ampli cation if high power holmium pulses are required.