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- Front Matter: Volume 8235
- Mid-IR Lasers
- Ceramics Laser Materials I
- Ceramics Laser Materials II
- Pulsed Lasers I
- Pulsed Lasers II
- Disk Lasers
- High-Power Fiber and Disk Lasers: Joint Session with Conference 8237
- Ultrafast Lasers
- Eye Safe Lasers
- Visible and UV Lasers I
- Visible and UV Lasers II: Joint Session with Conference 8240
- Novel Concepts for SSL
- Poster Session
Front Matter: Volume 8235
Front Matter: Volume 8235
Show abstract
This PDF file contains the front matter associated with SPIE Proceedings Volume 8235, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.
Mid-IR Lasers
High-efficiency diode-pumped Er:YLF laser with multi-wavelength generation
Mikhail Inochkin,
Leonid Khloponin,
Valery Khramov,
et al.
Show abstract
Er:YLF diode pumped solid-state laser with high optical efficiency and brightness was designed, built and tested. Pulsed
multi-frequency generation at a number of wavelengths in 2.66-2.85 μm range was theoretically analyzed and
experimentally investigated. An effective computational model used for Er:YLF laser optimization that accounts for the
generating spectrum was developed.
Mid-IR laser oscillation via energy transfer in the Co:Fe:ZnS/Se co-doped crystals
Show abstract
Room temperature iron doped II-VI lasers have demonstrated broad band tunability between 3.5 and 6 μm with
efficiency ~40%. However, these lasers require pump sources with a wavelength ~3 μm which could be selected only
from a few available. Cobalt ions in the II-VI materials have strong absorption bands at 4A2→4T1(4P) and 4A2→4T1(4F)
transitions located at ~0.75 and 1.5 μm, respectively. A number of different laser sources (including diode lasers) could
be potentially used for cobalt excitation followed by energy transfer to iron ions. Here we report materials fabrication
and study of energy transfer in Co:Fe:ZnS(ZnSe) crystals. Iron-cobalt co-doped samples were prepared using a two-stage
post-growth thermal diffusion procedure with Fe concentrations of 8.5-19x1018 cm-3. Kinetics and photoluminescence
spectra reveal energy transfer under cobalt excitation at 4A2-4T1(4F) transition by 1.56 μm radiation and 4A2-4T1(4P)
transition by 0.7 μm radiation. Analysis shows effective energy transfer from 4T1(4F), 4T2 and 4T1(4F) Co2+ energy levels
to 5T2 excited level of Fe2+ ions the first realization of Fe2+ ions lasing at 3.6 μm and 3.8μm via Co-Fe energy transfer.
Demonstrated effective Co2+→Fe2+ energy transfer process could result in utilization of a more convenient laser pump
sources for the Fe2+:II-VI lasers.
3.0-μm wavelength-tunable compact light source with 805/1064-nm differential frequency generation using intracavity photon reuse and spectrum shaping techniques
Show abstract
Mid-infrared (mid-IR) light sources operating in the 3-μm waveband are useful photonic devices for the spectroscopic
detection of trace gases and biomaterials. In order to achieve efficient mid-IR light emissions with a small footprint, we
propose an attractive technique for developing a compact intracavity system that enables the reuse of the photons emitted
by the pump source. Periodically poled congruent LiNbO3 (PPCLN) and Nd-YVO4 crystals were both set in the
intracavity. An 805-nm waveband GaAs-based laser diode was used as the signal and pump light sources for differential
frequency generation (DFG), since GaAs-based device technology enables the construction of high-power, highefficiency
lasers operating in this waveband. We have successfully demonstrated that a 3-μm wavelength-tunable light
source using the photon reuse technique is the most effective and compact intracavity system; it possesses useful
broadband wavelength tunability characteristics up to approximately 90 nm and offers a small footprint (15 × 30 cm).
We obtained high output power of the order of a few milliwatts from the developed light source. In addition, since the
optical spectrum shape of the mid-IR light is also important, we propose a useful spectrum shaping technique using a
Fabry-Perot (FP) etalon filter included in the intracavity system; we obtained a fine single-peak spectrum in the 3-μm
waveband. The developed wavelength-tunable compact intracavity mid-IR light source using the photon reuse and
spectrum shaping techniques is attractive for optical communications and biomedical applications.
Fabrication and optical properties of single-crystal YAG fiber optics
Show abstract
Single-crystal (SC) fiber optics have been grown for many years for use as passive fibers for the delivery of IR laser
radiation and as active fibers useful as minirod lasers. By analogy with doped-YAG, bulk laser crystals it is expected
that pure YAG SC fibers would be capable of transmitting extremely high laser energies. In this study we report on
the growth of SC yttrium aluminum garnet, Y3Al5O12 (YAG), fibers from undoped SC YAG source rods using the
Laser Heated Pedestal Growth (LHPG) technique. The YAG transmits IR wavelengths up to approximately 4 μm
which is a little beyond the transmission range for SC sapphire fibers. The garnet family of crystals is one of the
most commonly used oxide crystal hosts for lasing ions in high power solid-state lasers, with the most commercially
common laser host being YAG. The optical losses for 400-μm diameter YAG fibers have been measured to be about
1 dB/m at 2.94 μm. The longest length of YAG fiber grown has been about 65 cm.
Ceramics Laser Materials I
Ceramic materials for high power solid state lasers
Show abstract
We highlight our recent progress in achieving high efficiency solid state laser materials based on hot pressed Lu2O3.
Experimental details to further enhance the lasing performance from sesquioxide-based ceramic lasers are presented.
Synthesis of high purity rare-earth doped sesquioxide ceramic powder primarily based on Lu2O3 for high energy solid
state lasers is discussed. We also report the effect of the powder quality and fabrication process on the optical quality and
lasing performance of these ceramics. Various methods to obtain fine grained ceramics which are desirable for scaling to
high power lasers are also presented.
Ceramics Laser Materials II
Refractive indices and thermo-optic coefficients of Erbium-doped Yttria
Show abstract
The refractive indices and thermo-optic coefficients for varying concentrations of Er3+ doped polycrystalline yttria
were measured at a variety of wavelengths and temperatures. A Lorenz oscillator model was employed to model the
room temperature indices and thermo-optic coefficients were calculated based on temperature dependent index
measurements from .45 to 1.064 microns. Some consequences relating to thermal lensing are discussed.
Spectroscopic properties of Er-sesquoxides
Show abstract
The current effort reports on the spectroscopic properties (absorption, emission and fluorescence lifetime) as a function
of varying Erbium concentration in Y2O3. Results show a non-linear behavior in the fluorescence lifetimes and the
radiative-emission intensities for the 4I11/2 and the 4I13/2 energy levels.
Pulsed Lasers I
1kHz repetition rate, mode-controlled, passively Q-switched Nd:YLF laser operating at 1053 nm
Show abstract
This work presents a passively Q-switched and mode-controlled Nd:YLF laser that generates 150 kW of peak power at
1053 nm with 1kHz repetition rate. The new resonator design is capable of delivering 1.5 mJ and 10 ns pulses in a very
compact, simple and lightweight set-up.
1.34 μm Nd:YVO4 laser mode-locked by a single-walled carbon nanotube saturable absorber
Show abstract
Passive mode-locking of 1.3 μm solid-state lasers is problematic for semiconductor saturable absorber mirrors
(SESAMs) not only because of difficulties in their fabrication process but also in relation to the achievable parameters
and damage resistivity. In contrast, single-walled carbon nanotube saturable absorbers (SWCNT-SAs) exhibit broadband
absorption which is controllable by varying the nanotube diameter and chirality, and require relatively simple
manufacturing processes. Here we report on steady-state mode-locked operation of a diode pumped Nd:YVO4 laser on
the 4F3/2→4I13/2 transition at 1.342 μm using a transmitting SWCNT-SA. The SWCNT-SA employed in the present work
was fabricated by SWCNTs grown by high-pressure CO conversion technique, showing broad absorption around
1.3 μm. The linear transmission at the laser wavelength was about 99%. The Nd:YVO4 laser was longitudinally pumped
by the unpolarized radiation of a 808 nm fiber-coupled laser diode. The ~1.2-m long cavity was optimized for large
fundamental mode size. Above threshold the laser operated first in the CW mode, then had a range of Q-switched modelocked
operation before reaching the regime of stable steady-state mode-locking. With an output coupler of 90%
reflectivity, the average output power in the steady-state mode-locked regime reached 0.8 W at a slope efficiency of
14.5% with respect to the incident pump power. At a repetition rate of 127 MHz this corresponds to single pulse energy
of 6.3 nJ. Such pulse energies are comparable to the best results obtained using SESAMs but the pulse duration of
16.5 ps measured in the present experiment is substantially shorter.
Performance of a 100J cryogenically cooled multi-slab amplifier with respect to the pump beam parameters and geometry
Show abstract
We present advanced 3D ray-tracing code for calculation of amplified spontaneous emission (ASE), stored energy and
heat generation in laser active material. New results including spectrally resolved absorption, amplification and super-
Gaussian pump beam profile are obtained for 100 J cryogenically cooled multi-slab amplifier.
Comparative design study of 100 J cryogenically cooled Yb:YAG multi-slab amplifiers operating at 10 Hz
Show abstract
We present a comparison of two conceptual layouts of 100 J class laser systems for HiLASE and ELI Beamlines projects
with respect to the output energy, beam propagation and system performance obtained from MIRO code. Both systems
are based on cryogenically cooled Yb:YAG multi-slabs amplifiers technology and operate at 10 Hz repetition rate with
average power above 1 kW. First concept of the laser system consists of separate 10 J preamplifier and 100 J power
amplifiers, while the second consists of a main amplifier with two identical amplifier heads delivering 100 J.
Pulsed Lasers II
High power VCSEL array pumped Q-switched Nd:YAG lasers
Show abstract
Solid-state lasers pumped by high-power two-dimensional arrays of vertical-cavity surface-emitting lasers (VCSELs)
were investigated. Both end-pumping and side-pumping schemes of Nd:YAG lasers with high power kW-class 808 nm
VCSEL pump modules were implemented. For one application 10 mJ blue laser pulses were obtained from a frequencydoubled
actively Q-switched VCSEL-array dual side-pumped Nd:YAG laser operating at 946 nm. For another
application 10 mJ green laser pulses were obtained from a frequency-doubled passively Q-switched VCSEL-array endpumped
Nd:YAG laser operating at 1064 nm. Both QCW and CW pumping schemes were investigated to achieve high
average Q-switched power.
Compact VCSEL pumped Q-switched Nd:YAG lasers
Brian Cole,
Alan Hays,
Chris McIntosh,
et al.
Show abstract
We have explored using 808nm Vertical Cavity Surface emitting laser (VCSEL) arrays for end-pumping of Nd:YAG
lasers. A variety of laser designs were explored including a compact passively Q-switched lasers that produced a 22mJ
pulse having a pulse width of <1.5ns, and an actively Q-switched laser that produced a 40mJ pulse having a 7 ns pulse
width. The VCSEL pumped actively Q-switched laser was used as a source for sum frequency generation. Using a
2mm type II KTP and 3mm type I LBO, we generated greater than 5mJ at 355nm with a 21% THG conversion
efficiency.
Disk Lasers
Yb:CaGdAlO4 thin-disk
S. Ricaud,
A. Jaffres,
P. Loiseau,
et al.
Show abstract
We present an Yb-CALGO thin-disk laser in continuous regime. In a slightly multimode configuration we obtain up to
29.5W of average power, corresponding to a slope efficiency of 40% and an optical-to-optical efficiency of 32%. We
then design a monomode cavity, and achieve 25W of average power. The tuning range of the laser emission was from
1018 to 1052nm. In a Q-switch regime, we obtain more than 1 mJ at 100 Hz repetition rate, and 4.5W at 10 kHz
repetition rate.
Design and modeling of kW-class thin-disk lasers
Show abstract
We present recent progress in development of high power directly diode pumped lasers based on the Yb:YAG thin-disk
technology which are being constructed at the HiLASE project in the Czech Republic. Up to three laser chains, each
delivering more than 1 J in 1 ps pulse with 1 kHz repetition rate should be built until 2015. In order to overcome
technological barriers and optimize the amplifiers which are under construction, a new time-resolved numerical model
suitable for describing of quasi-three-level active media operateing at room temperature in the thin-disk laser head is
being created. The model is based on Monte Carlo ray-tracing and considers decreasing of the upper laser level
population due to the amplified spontaneous emission. In the near future, the model will be used for optimizing of a 2-
heads Yb:YAG zero phonon line pumped regenerative amplifier delivering up to 100 mJ in 1 ps pulse and 1 kHz
repetition rate.
Yb:YAG thin-disk laser performance at room and cryogenic temperatures
Show abstract
Cryogenic solid-state laser materials offer many improvements in thermal, optical, structural, and lasing properties over
their room temperature counterparts. As the temperature of Yb:YAG decreases from room to 80K it transitions from
quasi-three-level lasing to a 4-level laser. In this study, we compare Yb:YAG thin-disk laser performance at room 293K
and 80K. To achieve this direct comparison we have built two cooling systems based on R134A refrigerant and also on
liquid nitrogen (LN2). We have made an analytical calculation of the small signal laser gain that takes into account the
spurious amplified spontaneous emission and photon re-absorption. The cold thin-disk laser clearly outperforms room
temperature operation, and the theoretical results shows room temperature gain flattening.
Initial testing of edge-pumped Yb:YAG disk laser with multi-passed extraction
Show abstract
We report on initial testing of an edge-pumped Yb:YAG disk laser. The assembled laser uses two laser
disks having a composite ceramic construction with undoped perimetral edge designed to channel pump
light while efficiently outcoupling amplified spontaneous emission (ASE). Edge-pumping allows for
reduced doping of crystals with laser ions, which translates to a lower lasing threshold in Yb:YAG
material and much reduced waste heat flux. This work presents results of initial testing of the laser with
one Yb:YAG laser disk and resonator optics configured for power extraction with two passes through the
disk.
Gain tailoring model and improved optical extraction in CW edge-pumped disk amplifiers
Show abstract
The effect of gain tailoring upon the optical extraction and OPD in a CW edge-pumped disk amplifier is examined using
a two-dimensional model of diode pumping coupled with a two-dimensional, geometric model of optical extraction by a
Gaussian profile beam from a Yb:YAG medium1. The gain medium is described by the well-known quasi-three level
model of Beach2,3. Gain tailoring is accomplished by focusing the diode pump beam using cylindrical lenses. The diode
pump beam, optical extraction, and gain medium models are described after which the pump absorption efficiency, energy
deposition uniformity, output energy, and maximum peak-to-valley (PV) OPD are examined as a function of the
pump lens focal length and output aperture radius as well as amplifier input seed energy, number of roundtrip amplifier
passes, and diode pump power. It is shown that using pump beam focusing to tailor the gain radially deposits more energy
in the central region of the disk and thus results in improved optical extraction because a Gaussian input optical
beam preferentially accesses the central region of the disk. With gain tailoring one can achieve the same amplifier output
energies as without gain tailoring but using less pump power and/or amplifier seed energy, resulting in reduced disk
heating and diode-pump waste heat. Although the maximum PV OPD is larger, the central region of the thermally-induced
OPD remains relatively uniform, allowing one to increase the output energy with only modest increases in the effective
OPD.
High-Power Fiber and Disk Lasers: Joint Session with Conference 8237
High-power disk and fiber lasers: a performance comparison
Show abstract
The Performance of High Power Disk Lasers and Fiber Lasers along with their rapid development to the high power cw
regime have been of great interest throughout the last decade.
Both technologies are still in the focus of several conferences, workshops, and papers and represent the "state-of-the-art"
of industrial high power solid state lasers for material processing. As both laser concepts are considered to be the leading
1 μm light-source, this presentation presents an objective and fair comparison of the two different technologies from a
manufacturer who pursued both.
From the geometry of the active material, through the resonator design, cooling regime, and pumping method to the point
of beam quality and power scaling, the different approaches associated with the advantages, challenge and limits of each
technology will be discussed.
Based on ROFIN's substantial industrial experience with both laser concepts, an outlook into future trends and chances,
especially linked to fiber laser, will be given.
High-power disk lasers: advances and applications
Show abstract
Though the genesis of the disk laser concept dates to the early 90's, the disk laser continues to demonstrate the
flexibility and the certain future of a breakthrough technology. On-going increases in power per disk, and
improvements in beam quality and efficiency continue to validate the genius of the disk laser concept. As of today,
the disk principle has not reached any fundamental limits regarding output power per disk or beam quality, and
offers numerous advantages over other high power resonator concepts, especially over monolithic architectures.
With about 2,000 high power disk lasers installations, and a demand upwards of 1,000 lasers per year, the disk laser
has proven to be a robust and reliable industrial tool. With advancements in running cost, investment cost and
footprint, manufacturers continue to implement disk laser technology with more vigor than ever.
This paper will explain recent advances in disk laser technology and process relevant features of the laser, like pump
diode arrangement, resonator design and integrated beam guidance. In addition, advances in applications in the
thick sheet area and very cost efficient high productivity applications like remote welding, remote cutting and
cutting of thin sheets will be discussed.
Ultrafast disk lasers and amplifiers
Show abstract
Disk lasers with multi-kW continuous wave (CW) output power are widely used in manufacturing, primarily for cutting
and welding applications, notably in the automotive industry. The ytterbium disk technology combines high power (average
and/or peak power), excellent beam quality, high efficiency, and high reliability with low investment and operating
costs. Fundamental mode picosecond disk lasers are well established in micro machining at high throughput and perfect
precision. Following the world's first market introduction of industrial grade 50 W picosecond lasers (TruMicro 5050) at
the Photonics West 2008, the second generation of the TruMicro series 5000 now provides twice the average power
(100 W at 1030 nm, or 60 W frequency doubled, green output) at a significantly reduced footprint. Mode-locked disk
oscillators achieve by far the highest average power of any unamplified lasers, significantly exceeding the 100 W level in
laboratory set-ups. With robust long resonators their multi-microjoule pulse energies begin to compete with typical ultrafast
amplifiers. In addition, significant interest in disk technology has recently come from the extreme light laser community,
aiming for ultra-high peak powers of petawatts and beyond.
Ultrafast Lasers
A multi-wavelength, variable-pulse-width, diode-pumped laser system
Show abstract
An all-solid-state laser system that provides 165-fs to 60-ps FWHM (full-width-at-half-maximum) pulses in a UV to
near-IR wavelength range is described. The laser system consists of a femtosecond laser, a highly stable diode-pumped
regenerative amplifier, and frequency-conversion crystals. The system can be configured for various photodetector
impulse-response measurements, single-shot impulse and frequency response measurements for the photodetector-
oscilloscope combinations, streak-camera sweep calibration, and dynamic-range measurements.
SESAMs for high-power femtosecond modelocking: power scaling of an Yb:LuScO3 thin disk laser to 23 W and 235 fs
Clara J. Saraceno,
Oliver H. Heckl,
Cyrill R. E. Baer,
et al.
Show abstract
We report on power scaling of a modelocked thin disk laser (TDL) based on the broadband mixed sesquioxide material
Yb:LuScO3 (22 nm full width half maximum (FWHM) emission bandwidth). In a first experiment, we could demonstrate
pulse durations as short as 195 fs at a moderate average power of 9.5 W. Furthermore, we were able to power scale our
TDL while keeping the pulses short reaching 23 W at a pulse duration of 235 fs. A key element to achieve this result was
the design of new SESAM structures with multiple quantum wells (QW) and a suitable dielectric topcoating, resulting in
SESAMs with appropriate parameters for short pulse geneartion, low two-photon absorption (TPA) and high damage
thresholds. We will present SESAM optimization guidelines for short pulse generation from high-power modelocked
oscillators.
Regenerative amplifier with pulse-on-demand
Show abstract
A picosecond regenerative amplifier with pulse on demand operation is demonstrated. The pulse energy is held constant
for arbitrary pulse separation by employing an intracavity loss modulator. The loss modulator is controlled by a digital
signal processor monitoring the gain of the laser material in real time. The gain is estimated from a measurement of the
emitted fluorescence from the upper laser level, and the signal processor adjusts the loss in such way to keep the total
round-trip gain constant regardless of the time separation to the previous pulse. The system is able to completely
suppress the usual multistable regimes of a regenerative amplifier operated under a variation of the repetition rate. We
achieve constant output energy for a linear change of repetition rates between 0 and 100kHz with a slope of 2MHz/s.
Sub-100 fs pulses with 12.5-W from Yb:CALGO based oscillators
Show abstract
We report on the generation of 94-fs pulses with 12.5-W average output power from an 80-MHz Yb3+:CaGdAlO4(Yb:CALGO) oscillator with pulse energies and peak power levels higher than 150-nJ and 1.45-MW, respectively. To the
best of our knowledge, this is the highest average power ever reported for a sub-100-fs bulk oscillator. Average output
power levels higher than 10-W were also achieved in lower repetition rate oscillators at 23.7 MHz and 42.5 MHz with
pulse durations ranging from 141-fs to 323-fs and corresponding pulse energies as high as 0.42 μJ. In all experiments
stable and self-starting mode-locking with transform-limited pulses and beam quality factors better than M2<1.1 were
achieved. Continuous tunability in mode-locked operation between 1026-nm and 1052-nm was also demonstrated. We
believe that shorter pulses at higher average output powers should be possible and - combined with extended cavities -
such laser systems could reach the μJ pulse energy level with peak powers in the 10-MW regime.
Cryo-Yb:YAG lasers for next-generation photoinjector applications
Show abstract
Advanced, high-brightness photoinjectors are required for the next generation of linear accelerators and free-electron
lasers. Current photoinjector lasers suffer from complexity due to the use of multiple amplifier stages to achieve the
desired pulse energy and have issues with power scaling. In this work, we used a liquid-nitrogen-cooled, Yb:YAG,
mode-locked laser master-oscillator/power-amplifier as a high-average-power laser source for laser photoinjector applications.
Such a laser can provide average powers of 93 W with repetition rates of 1 MHz (93 μJ per pulse). The 10-ps
pulses from the oscillator were amplified in a four-pass cryo-Yb:YAG amplifier.
High-energy 1 Hz titanium sapphire amplifier for PetaWatt class lasers
François Lureau,
Sébastien Laux,
Olivier Casagrande,
et al.
Show abstract
We have obtained 23 J uncompressed laser pulses at a repetition rate of 1 Hz with a spectral width of 41 nm FWHM
which could produce 600 TW if compressed ; this is the highest energy obtained to date from a Titanium Sapphire
amplifier working at a such repetition rate. This amplifier is part of a 1.3 PW laser system under construction by Thales
Optronique for the BELLA project of LBNL aiming laser wakefield acceleration of electrons up to 10 GeV.
Eye Safe Lasers
Er-doped Tellurite glasses for planar waveguide power amplifier with extended gain bandwidth
Show abstract
Tellurite glass compositions doped with erbium and erbium/ytterbium optimised to support extended gain
bandwidth with significant amplification have been fabricated, and their thermal, optical absorption, excitation and
luminescence properties investigated. Each rare-earth dopant concentration was set at 1x1020cm-3. Broad emission crosssection
bandwidths up to 50nm FWHM were observed, with fluorescence lifetimes of ~3ms. Collinear pump probe
measurements on ~4mm thick bulk samples revealed peak gains of up to 2.1dB/cm at a wavelength of 1535nm in the codoped
material, with an incident pump intensity of only Iinc~8kWcm-2 at a wavelength of 974nm. At equivalent absorbed
pump powers between co-doped and single doped materials the relative gain was 1.25dB/cm (Iinc~4kWcm-2) and
0.9dB/cm (Iinc~8kWcm-2) respectively, demonstrating efficient energy transfer from the ytterbium to erbium ions.
Excited state absorption at longer wavelengths was observed and characterised and its implication on realising sufficient
gain in the wavelength band of interest is discussed.
Optimized heat extraction geometry for resonantly diode pumped Er3+:YAG lasers
Show abstract
A new heat extraction geometry for resonantly-diode-pumped Er3+:YAG lasers has been proposed. With this approach
heat extraction from a laser rod is symmetrised and improved significantly, thus thermal lensing and thermo-induced
aberrations of the active crystal are reduced. For proposed approach more than 10 W average has been generated both in
CW and QCW mode of operation at comparable pumping conditions with nearly diffraction limited beam. Investigations
on diffraction effects inside the fiber-like laser rod have been performed and theoretical background of observed
phenomena have been defined. Finally results of further investigations on actively Q-switched laser will be presented.
Resonant diode-pumping of Er:YAG single crystal fiber operating at 1617 nm
Show abstract
We demonstrated laser operation of a Er:YAG single crystal fiber at 1617 nm. Pumped on both sides by a laser diode at
1532 nm, a 600 μm diameter- 60 mm long- single crystal fiber produced an output power of 5.5 W once the wavelength
1617 nm was selected by an intracavity etalon. In Q-switched operation with an acousto-optic modulator, the laser
produced an energy of 0.5 mJ at 100 Hz repetition rate with a pulse duration of 28 ns. The Watt level in average power
was achieved for a repetition rate of 3 kHz with a pulse duration maintained around 30 ns.
Ho:KRE(WO4)2, RE=(Y, Gd, Lu), CW laser performance near 2.1 micron under resonant pumping by a Tm:KLu(WO4)2 laser
Show abstract
Continuous-wave (CW) lasing of Ho in KRE(WO4)2 (RE=Y, Gd, Lu) crystals has been compared using in-band
pumping by a diode pumped Tm:KLu(WO4)2 laser under identical conditions at room temperature. The three monoclinic
double tungstate hosts perform similarly with the maximum output power obtained for Ho:KY(WO4)2, 406 mW with
slope efficiency of 59.9%. For Ho:KLu(WO4)2 the maximum power reached 392 mW but the slope efficiency was
slightly higher, 61.6%. Ho:KGd(WO4)2, for which the ionic radius difference between dopant and substituted ions is
maximum, generated an output power of 368 mW with slope efficiency of 53.2%.
Crystalline fiber Ho3+:YAG laser resonantly pumped by high-spectral-brightness laser diodes
Show abstract
Recent advances of high power and narrow bandwidth laser diodes emitting at 1.9 μm open the path to direct diode
pumping of Ho3+:YAG lasers. The usual method to pump such laser is to use thulium fiber laser which has an excellent
beam quality with high power and narrow bandwidth emission. The draw back of this system is the low efficiency of this
fiber laser and the increased overall complexity. In this paper we present first results of resonantly diode pumping of a
Ho3+:YAG laser with fiberlike geometry. The fiber coupled diode modules used for pumping in this work (BrightLockTMUltra-500) produce each 25 W at 1.91 μm with 3 nm linewidth. The fiber has a core diameter of 600 μm with 0.22
numerical aperture. The Ho3+:YAG crystal has a diameter of 1.2 mm, a length of 60 mm, a doping concentration of 0.75
at.% and is symmetrically pumped by two diode modules from both ends. Total internal reflection on the polished rod
barrel allows a high pump intensity along the rod length. The Ho3+:YAG laser cavity is composed of a high reflective flat
mirror and a concave output coupler with a radius of curvature of 500 mm. With an output coupler of 50 % we measured
a threshold of 11 W. The maximum output power was 11.87 W with a wavelength of 2.09 μm. The incident power to
output power slope efficiency was 0.38 at currently 4 % of internal losses.
A coherent laser Doppler wind profiler for the active control of wind turbines
Show abstract
A low cost design concept for Fibre-based Coherent Laser Doppler Wind Profiler is presented for supporting an active
pitch control of Wind Turbines (WTs). The system is based on a 1.5μm Continuous-Wave (CW) semiconductor laser
source plus an erbium-doped fibre amplifier (EDFA) with an output power of 1W. A coherent detection method is used
for Doppler frequency measurement. In addition, a concept of wind turbine predictive pitch control system is proposed
for reducing the damage caused by wind turbulence. A mathematical simulation and the experimental result based on a
lab setup are presented to show the calibration of such a system.
Visible and UV Lasers I
Potential of the Eu:LYB crystal as a laser material for DPSS lasers emitting at 613 nm
R. Cattoor,
I. Manek-Hönninger,
J.-C. Delagnes,
et al.
Show abstract
We show the spectroscopic properties of a new potential laser crystal in the visible range. The Eu-doped borate
compound has the structure Eu3+:Li6Y(BO3)3 with a doping concentration of about 25%. We studied the absorption and
emission spectra of the crystal and calculated the gain cross sections. The compound shows a strong emission peak at
613 nm and absorption at 394 nm, which is compatible with pumping by new blue laser diodes. These features make the
Eu:LYB crystal a very interesting candidate for the development of DPSS lasers emitting in the visible range.
High average power sub-picosecond pulse generation at 515 nm by extracavity frequency doubling of a mode-locked Innoslab MOPA
Show abstract
More than 370 W average power at 515 nm were achieved by frequency doubling of sub-picosecond pulses of an
Innoslab based Yb:YAG MOPA system. At 50 MHz repetition rate this corresponds to a pulse energy of 7 μJ in the
green. The pulse duration of 680 fs and the transformation limit of the infrared source could be maintained, thus the laser
provides more than 10 MW pulse power. The beam quality at 280 W was M2 < 1.4, at more than 370 W it was measured
as M2 < 1.7. Extensive numerical modeling was applied to design the conversion stage.
Development and optimization of single-mode green solid state microchip laser
Show abstract
In this paper the development and optimization process of single frequency, diode pumped Nd:YVO4/YVO4/KTP
microchip laser operating at 532nm is presented. A birefringent filter formed by beam displacer (undoped YVO4 crystal)
and KTP crystal was used to obtain single mode operation. As a final result of optimization miniature, monolithic laser
resonator was elaborated. The laser generated Gaussian beam with quality better than M2<1.2 and maximum single
frequency output power at the level of 160mW @ 532 nm. The optical to optical efficiency (532nm to 808nm) was at the
level of 16,8% at the maximum single frequency output power.
Stability-enhanced, high-average power green lasers for precision semiconductor processing
Show abstract
Laser stability is critical to many industrial applications but is often a source of confusion when specifying and
comparing different laser systems. This can be due to the variety of parameters characterized, the range of measurement
techniques available and the many alternative methods that can be employed to analyse and present the stability data.
High throughput semiconductor applications with sensitivity to individual pulse variations require high average power
systems with optimised pulse energy stability. We report stability characterisation and optimisation for a range of
frequency doubled Q-switched Nd:YAG laser systems with average power up to 650 W and peak power up to 0.9 MW.
The techniques used to refine the stability of the lasers are described and the stability of the lasers is compared before
and after optimisation. Stabilised industrial 532 nm laser systems are presented with pulse energy up to 63 mJ and peak
to peak pulse energy variation reduced by a factor of two compared to standard systems at 10 kHz repetition rate.
Visible and UV Lasers II: Joint Session with Conference 8240
Frequency-doubled diode laser for direct pumping of Ti:sapphire lasers
Show abstract
A single-pass frequency doubled high-power tapered diode laser emitting nearly 1.3 W of green light suitable for direct
pumping of Ti:sapphire lasers generating ultrashort pulses is demonstrated. The pump efficiencies reached 75 % of the
values achieved with a commercial solid-state pump laser. However, the superior electro-optical efficiency of the diode
laser improves the overall efficiency of the Ti:sapphire laser by a factor > 2. The optical spectrum emitted by the
Ti:sapphire laser shows a spectral width of 112 nm (FWHM). Based on autocorrelation measurements, pulse widths of
less than 20 fs are measured. These results open the opportunity of establishing diode laser pumped Ti:sapphire lasers for
e.g. biophotonic applications like retinal optical coherence tomography or pumping of photonic crystal fibers for CARS
microscopy.
Mode hop free tunable blue laser
Show abstract
A mode hop free tunable blue laser at 465 nm based on an external cavity system is investigated. The single longitudinal
mode second-harmonic generation (SHG) blue laser was generated using quasi-phase matching (QPM) based MgO:
PPLN pumped by infrared diode laser at 930 nm with one lasing longitudinal mode. The wide turning rang in excess of
100 GHz is achieved by using combination the etalon, silica glass plate and narrow band filter into the external cavity,
which only allow one longitudinal mode running and operating wavelength tuning. 30 mw blue light was obtained at
wavelength of 465 nm with beam quality better then M2 =1.3.
Novel Concepts for SSL
Passive alignment and soldering technique for optical components
Show abstract
The passive-alignment-packaging technique presented in this work provides a method for mounting tolerance-insensitive
optical components e.g. non-linear crystals by means of mechanical stops. The requested tolerances for the angle
deviation are ±100 μrad and for the position tolerance ±100 μm. Only the angle tolerances were investigated, because
they are more critical. The measurements were carried out with an autocollimator. Fused silica components were used
for test series. A solder investigation was carried out. Different types of solder were tested. Due to good solderability on
air and low induced stress in optical components, Sn based solders were indicated as the most suitable solders. In
addition several concepts of reflow soldering configuration were realized. In the first iteration a system with only the
alignment of the yaw angle was implemented. The deviation for all materials after the thermal and mechanical cycling
was within the tolerances. The solderability of BBO and LBO crystals was investigated and concepts for mounting were
developed.
Generating multiple wavelengths, simultaneously, in a Ti:sapphire ring laser with a ramp-hold-fire seeding technique
Show abstract
The ability to simultaneously produce pulsed laser output over multiple discrete wavelengths can mitigate many of the
timing and jitter issues associated with the use of multiple laser systems. In addition, Fourier-transform limited laser
output on every pulse is required for many applications such as with pump-probe detection, non-linear frequency
mixing, differential absorption lidar (DIAL), and resonance ionization. As a matter of practice, such lasers need to be
capable of operating within uncontrolled or noisy environments. We report on a novel Ti:sapphire ring laser that has
been developed to produce Fourier-transform limited 20-ns laser pulses at multiple discrete wavelengths,
simultaneously, utilizing a Ramp-Hold-Fire (RHF) seeding technique. Resonance of the seed light is achieved by using a
KD*P crystal to modify the phase of the light circulating within the slave oscillator cavity where the fast response of the
crystal results in a seeding technique that is immune to noise throughout the acoustic regime.
Voltage tunable polymer laser device
Show abstract
Since organic laser materials offer broad optical gain spectra they are predestined for the realization of widely
tunable laser sources. Here we report on a compact organic laser device that allows for voltage controlled
continuously wavelength tuning in the visible range of the spectrum by external deformation. The device
consists of an elastomeric distributed feedback (DFB) laser and an electro-active elastomer actuator also
known as artificial muscle. Second order DFB lasing is realized by a grating line structured elastomer
substrate covered with a thin layer of dye doped polymer. To enable wavelength tuning the elastomer laser is
placed at the center of the electro-active elastomer actuator. Chosen design of the actuator gives rise to
homogeneous compression at this position. The voltage induced deformation of the artificial muscle is
transferred to the elastomer laser and results in a decrease of grating period. This leads to an emission
wavelength shift of the elastomer laser. The increase of actuation voltage to 3.25 kV decreased the emission
wavelength from 604 nm to 557 nm, a change of 47 nm or 7.8%.
Poster Session
Temperature effects on the operation and input/output wavelengths of a high-power fiber-coupled diode end pumped Nd:YVO4 laser
Show abstract
A complete electrical and optical characterization for the high power diode laser module operating at
808 nm was performed. The laser diode operating at room temperature 25oC gave a higher slope
efficiency with low consumption electrical power and low threshold current lasing of 1.3 A.
Maximum slope efficiency of 42% with a final electrical to optical conversion efficiency of 28% at
807.96 nm central wavelength with line width of 3.59 nm at FWHM was investigated. The emitted
laser wavelength was measured and is affected by the temperature increasing; the diode peak
wavelength was shifted by 0.35nm/oC.
Moreover, the appropriate wavelength for pumping Nd3+ doped materials (around 808nm) was
obtained at the temperature range of (20-25oC). Typical 808nm diode laser output was obtained with
different driving input current at constant temperature of 25oC.
To illustrate the effect of changing diode temperature on the DEPSS output laser wavelength, the
diode operating temperature must varied to be (12, 25, and 36oC) and consequently, the pumping
central wavelength will be changed, we presented that the output DEPSS (Nd:YVO4) wavelength
does not change because the broad band absorbance property for the Nd:YVO4 crystals.
DEPSS (Nd:YVO4) laser system was implemented, and its optical characteristics were measured.
Stable wavelength of 1066.08nm with a linewidth of 1.48nm at FWHM at different diode pumped
powers (1, 1.4, and 1.75 Watt) and at constant temperature of 25oC was measured. With diode
pumping power of 6.6W, the output power was 3.273W with an output coupler reflectivity of 90%.
The Fundamental mode (TEM00) was examined, and the measured DEPSS divergence angle was
11±0.5 milliradian.
Comparison between two active media Nd: YAG and Nd: YVO4 rods inside a cavity for producing a high-power 808nm diode end-pumping laser system
Show abstract
Diode end-pumped solid-state lasers have the potential to yield high quality laser beams with high efficiency and
reliability. This paper presents a comparison between high-efficiency Nd: YVO4 and Nd: YAG laser rods in the 20W
diode end-pumped laser systems. Comparison done by using a special finite element analysis software program
(professional LasCad version 3.6.1) for characterizing the all effective parameters inside the cavity like; optimized rod
length, optimized rod diameter, beam waist spot size, optimized resonator length. Theoretical modeling of the absorbed
power density for end pumped rods is studied. Stability and analyzed temperature distributions, temperature effects on
the solid state crystal (thermal fracture) and thermal lensing effects in 3-D numerical model are investigated. It is
important to simulate the temperature gradient on the front face and inside the pumped Nd: YAG and Nd: YVO4 crystal
to avoid thermally induced fracture and evaluates the maximum pumped power. This paper shows that Nd: YVO4 laser
system has higher optical efficiency of 40% than that of Nd: YAG laser system with optical efficiency of 25%, and the
optimized output powers for Nd: YVO4 and Nd: YAG of 8.63 W and 5.4 W, respectively for same parametric study like;
rod length of 6 mm, rod diameter of 2 mm, beam waist of 150 μm and resonator length of 56.16 mm.
Amplified spontaneous emission in thin-disk lasers
Show abstract
Amplified spontaneous emission (ASE) and parasitic oscillations (PO) in disk lasers with unstable resonators
are investigated theoretically. The efficiency loss due to ASE/PO is essentially determined by the product of
disk diameter D and "self-maintain gain" of ASE/PO. Threshold to establish the laser oscillations in presence
of ASE/PO is explored as the self-maintain gain of ASE/PO is higher than threshold gain gt of the resonator.
The criterion to ignore ASE/PO in disk laser is given by gtD < 2.0 as an ASE absorber is clad, gtD < 0.55 as
the disk side is roughened, and gtD <0.8 as the effective ASE path is half reduced. The time evolution of laser
output exhibits a strenuous relaxation oscillation, in which ASE plays a role of strong damping, and consume
the energy before each of sub-pulses.
Influence of Ce3+-ions in Pr,Ce:YAlO3 crystal on spectroscopic and laser characteristics
Show abstract
Influence of Ce3+-ions in Pr,Ce:YAlO3 crystal on spectroscopic and laser characteristics has been investigated.
Spectroscopic properties and preliminary laser results of GaN-diode pumped Pr,Ce:YAlO3 active medium at room
temperature have been reported and compared with the same crystal without Ce3+-ion. Co-doping of the active medium
by Ce3+-ions was proposed for crystal property improvement in terms of color center formation caused by UV radiation.
10 km dynamic laser oscillation with a coupled cavity assisted by four wave mixing
Show abstract
In this report, we present results of dynamic laser oscillation over a 10 km distance using a coupled-cavity structure
assisted by four wave mixing (FWM). The system consists of a master cavity and a slave cavity that are coupled together
through FWM in a nonlinear medium. The master and slave laser beams each form two arms of the four wave mixing
structure. The master laser consists of a cavity formed by two highly reflective mirrors, in which there is a gain medium
and the FWM nonlinear medium. For the slave laser cavity, one of the end mirrors is the grating formed inside the FWM
medium, and the other mirror is the remote moving target. In this case, this target is a retro-reflector located on a moving
airplane. The laser tracking was completed with a rotating gimbal mirror system that locked on the target. Successful
lasing field tests at distances over 10 km have been achieved, and further results can potentially be obtained at longer
distances. The laser oscillations are free running with a pump pulse width of 2-5 milliseconds. Based on the time
separations between the pulses from the master and slave cavities, the target distance can be precisely calculated.
Passive Q-switching of a diode-pumped (Tm,Yb):KLu(WO4)2 laser near 2-μm with a Cr2+:ZnS saturable absorber
Show abstract
Passive Q-switching of a diode-pumped (Tm,Yb):KLu(WO4)2 laser, operating between 1910 and 1950 nm, has been
achieved using polycrystalline Cr2+:ZnS as a saturable absorber in a hemispherical L-shaped cavity. The dependence on
the doping levels of Tm and Yb and the low-signal absorption of the saturable absorber has been studied. The highest
average output power reached 272 mW at a repetition rate of 2.04 kHz corresponding to a pulse energy of 133 μJ. This
was achieved with (8.8 at. % Tm, 2.3 at. % Yb):KLu(WO4)2 active element and a saturable absorber with 85% lowsignal
transmission. The highest pulse energy, 148 μJ, was achieved with the same combination at lower (0.94 kHz)
repetition rate. The obtained pulse energy with the different samples is compared with theoretical analysis and the pulse
duration and peak power are estimated from the calculations.
High-energy, picosecond regenerative thin-disk amplifier at 1 kHz
Show abstract
We present recent progress in development of a compact regenerative laser amplifier based on the Yb:YAG thin-disk
technology delivering up to 100 mJ picosecond pulses with a repetition rate of 1 kHz, designed for seeding a kW-class
multipass amplifier for industrial and scientific applications. System utilizes two laser heads pumped at zero-phonon line
(968.825 nm1) by stabilized high-power pump diodes operated in pulsed regime. The concept is based on the CPA
technique where seed pulses produced by fiber oscillator at 1030 nm are stretched and compressed by use of
transmission gratings.
Tuning possibility of dysprosium-doped lead thiogallate laser
Show abstract
One of the promising active ions giving the possibility of laser radiation generation in 4 - 5 μm region is trivalent
dysprosium in lead thiogallate crystal. On the basis of our previous Dy3+:PbGa2S4 laser study, this work is showing a
several wavelengths generation possibility. The laser was working at the room temperature and it was in-band pumped
by the Er:YLF laser radiation with the wavelength 1.73 μm. The investigated crystal Dy3+:PbGa2S4 was synthesized
using Bridgman technique from the melt. Dimension of the sample was 16 mm long and 19 mm in diameter and the
nominal Dy3+ ion concentration was ~ 0.7 at. %. The laser operation was tested with three resonator configurations. The
first was the non-selective resonator with the length 41 mm. To perform the wavelength tuning, in the second case the
MgF2 Lyot filter was inserted under Brewster angle inside the resonator which length was 100 mm. In both these cases
the laser resonator was formed by the incoupling flat dichroic mirror with low reflectivity at pumping wavelength (T =
90%@1.73 μm) and high reflectivity (R~100%) within the 3.5 - 4.5 μm spectral range, and by an out-coupling concave
(r = 500 mm) mirror with reflectivity of 95 % or 98 % in the same region of wavelengths. For the third case the selective
mirrors supporting the 3.0 - 4.0 μm spectral region were chosen. The generation possibility on three lines 4 μm, 4.3 μm,
and 4.6 μm were found without continuous tuning between them.
Compact pulsed high-energy Er:glass laser
Show abstract
Bulk Erbium-doped lasers are widely used for long-distance telemetry and ranging. In some applications such as
coherent Doppler radars, laser outputs with a relatively long pulse width, good beam profile and pulse shape are
required. High energy Q-switched Er:glass lasers were demonstrated by use of electro-optic (E/O) Q-switching or
frustrated total internal reflection (FTIR) Q-switching. However, the output pulse durations in these lasers were fixed to
relatively small values and extremely hard to tune. We report here on developing a novel and compact Q-switched Er:Yb
co-doped phosphate glass laser at an eye-safe wavelength of 1.5 μm. A rotating mirror was used as a Q-switch. Co-linear
pump scheme was used to maintain a good output beam profile. Near-perfect Gaussian temporal shape was obtained in
our experiment. By changing motor rotation speed, pulse duration was tunable and up to 240 ns was achieved. In our
preliminary experiment, output pulse energies of 44 mJ and 4.5 mJ were obtained in free-running and Q-switched
operation modes respectively.
Influence of undoped YAG cap on diode-pumped composite YAG/Er:Yb:glass laser
Show abstract
Two samples of Er-Yb doped phosphate glass were tested as a gain medium of longitudinally diode pumped
laser. One sample was a simple Er:Yb:glass rod (length 2.8 mm), second sample was composite rod consisting of
2.8mm long Er:Yb:glass and 6mm long YAG crystal. Diameter of both samples was 6 mm. Dopant concentration
for Er:Yb:glass was 0.75 × 1020 cm−3 Er and 1.7 × 1021 cm−3 Yb. The goal of the experiment was to investigate
an effect of the undoped YAG cap on the Er:Yb:glass laser operation. The active medium, fixed in cupreous
heatsink, was placed inside the 150mm long resonator consisted of a flat pumping mirror (HR @ 1.52−1.65 μm,
HT @ 0.97 μm) and curved output coupler (r = 150 mm, R = 97% @ 1.52−1.61 μm). For Er:Yb:glass pumping a
fiber coupled laser diode, operating in pulsed regime, was used. The pumping pulse width, energy, and wavelength
were 1 ms, 10 mJ, and 975 nm, respectively. The decrease of Er:Yb:glass laser output pulse energy with increasing
pumping repetition rate was observed for both samples. In case of simple Er:Yb:glass the energy dropped from
1.4mJ to 0.6mJ after pumping duty cycle increase from 0.5% to 6 %. In case of composite YAG/Er:Yb:glass active
medium the relative output energy decrease was only 20% for pumping duty cycle increase from 0.5% to 10%.
This result showed that the slope of the output energy decrease with increasing duty cycle was approximately
four times slower for composite active media in comparison with simple Er:Yb:glass.
Spectroscopic characterization of Ti3+:AgGaS2 and Fe2+:MgAl2O4 crystals for mid-IR laser applications
Show abstract
Mid-IR lasers based on Cr2+ and Fe2+ ions in II-VI tetrahedral crystal hosts have been proven useful as tunable solid-state
lasers operating over the 1.9-6 μm spectral range. However, the development of new effective gain media promising for
lasing over 3-4 μm and with wavelengths longer than 6 μm is still under progress. In this paper we report spectroscopic
characterization of Titanium doped AgGaS2 and Iron doped MgAl2O4 crystals with coordination number four. Polarized
absorption and luminescence spectra of titanium doped AgGaS2 crystals were measured at room and low temperatures. It
was shown that Ti ions in the AgGaS2 crystal were in both 1+ and 3+ valence states substituting silver and gallium sites,
correspondingly. Ti3+ ions in AgGaS2 and Fe2+ in MgAl2O4 crystals feature broad absorption bands with a maximums
near 2μm. These ions have no second excited state absorption bands and could potentially be used as effective saturable
absorbers for passive Q-switching of 2.1 μm holmium laser cavities. Broad emission covering the 3-6 μm spectral range
was observed under 1.9 μm excitation into Ti3+ absorption band. A luminescence signal between 3 and 6 μm was also
observed in the Fe:MgAl2O4 crystal.
Mid-IR volumetric Bragg grating based on LiF color center crystals
Show abstract
Currently, a majority of Volumetric Bragg gratings (VBG) use photorefractive glasses with a transmission band between
0.3 and 2.7 μm. We have proposed and realized VBGs for mid-IR spectral range based on LiF color center crystals
(LiF:CC). γ-irradiated LiF:CC crystals feature strong absorption bands in the visible and near-IR spectral range, where
selective color center photo-bleaching allows for the LiF refractive index modification. The absence of active absorption
in LiF:CCs at wavelengths longer than 1.3 μm results in a VBG that is stable under mid-IR irradiation. Our calculations
predict that ~60% diffraction efficiency over 1-6 μm spectral range could be realized in ~1 cm long VBG. To verify this
calculation, we fabricated periodic structures in LiF:CC crystals with 24 and 12 μm spacings by CCs photo-bleaching
using femtosecond Ti:sapphire laser pulses. Periodic structures exhibit diffraction in multiple orders in the Raman-Nath
regime at 0.532, 0.632, and 1.56 μm. The first order diffraction efficiencies were stronger for a visible radiation due to a
bigger refractive index variations and additional amplitude modulation. The demonstrated diffraction at 1.56 μm is a
clear manifestation of a phase grating in LiF and serves as a proof of feasibility of these LiF:CC crystals for mid-IR
VBG applications.
Yb:YAG/Cr:YAG composite crystal with external and microchip resonator
Show abstract
A compact diode pumped Q-switched lasers, operating at wavelength 1031 nm, were based on the composite
crystal Yb:YAG/Cr:YAG. This composite crystal (diameter 3mm) consisted of diffusion bounded 3mm long
Yb:YAG (10 at.% Yb/Y) and 1.6mm long Cr:YAG crystal (initial transmission 85% @ 1031 nm). External
resonator allowing to tune generated Q-switched pulse parameters or microchip configuration offering the shortest
pulses and highest peak power were tested for this device. For longitudinal pumping of Yb:YAG gain medium,
fibre coupled (core diameter 200 μm, NA= 0.22) laser diode, operating at wavelength 968 nm, was used. In
the first case, Yb:YAG/Cr:YAG composite crystal was AR-coated and placed inside the 150mm long semihemispherical
resonator consisted of a flat pumping mirror (HR @ 1.01 − 1.09 μm, HT @ 0.97 μm) and curved
output coupler (r = 150mm) with reflectivity 70% @ 1031 nm. Generated pulses with the peak power 23 kW
were 17 ns long (FWHM). The highest generated pulse energy was 0.38 mJ. In the second case, the resonator
mirrors were deposited directly on the crystal faces. The output coupler reflectivity was 85% @ 1031 nm. In this
compact microchip configuration, 140 ps long (FWHM) pulses with energy 0.13mJ and peak power 0.92MW
were generated at wavelength 1031 nm.
A highly efficient DPSS mode-locked Nd:YLF single-mode laser
Show abstract
A mode-locked laser system achieves average output power of more than 18 watts, in a single transversal mode, with a
pump power of 70 watts. The optical to optical conversion efficiency is about 25%. The output wavelength is 1053 nm
and the mode locked frequency is 150 MHz; the pulse width is less than 80 ps. The peak power reaches kilowatts per
pulse. The wavelength can be converted into 527nm and 351 nm with a nonlinear conversion.
DPSS laser beam quality optimization through pump current tuning
Show abstract
The goal of this study is to demonstrate how a DPSS laser beam's quality parameters can be simultaneously
optimized through pump current tuning. Two DPSS lasers of the same make and model were used where the laser
diode pump current was first varied to ascertain the lowest RMS noise region. The lowest noise was found to be
0.13% in this region and the best M2 value of 1.0 and highest laser output power were simultaneously attained at the
same current point. The laser manufacturer reported a M2 value of 1.3 and RMS noise value of .14% for these
lasers. This study therefore demonstrates that pump current tuning a DPSS laser can simultaneously optimize RMS
Noise, Power and M2 values. Future studies will strive to broaden the scope of the beam quality parameters impacted
by current tuning.
Observation of laser formation inside a laser cavity containing a phase conjugate mirror
Show abstract
Adaptive optics (AO) systems are used to compensate atmospheric perturbations on a propagating laser beam. However,
AO needs a beacon to obtain the phase information. This paper presents a possible formation of beacon in target-in-theloop
(TIL) geometry which is analog to a laser cavity. The TIL laser cavity is formed with a high reflectivity mirror on
one end and an optical phase conjugate mirror as the second mirror. The TIL laser is initialized by a single frequency 10
ns Q-switched laser pulse. This is very similar to how an injection seeding or regenerative amplifier scheme starts a laser
oscillation. With a cavity length of around 11 meters and an initial laser pulse of 10 ns, we have been able to isolate laser
field images related to each round-trip pulse. Furthermore, by replacing the first mirror with a rough-surface target to
simulate an uncooperative target and adding phase distortion elements to simulate atmospheric effects, we can observe
the image status under such conditions.