We investigated cw intra-cavity third-harmonic generation (THG), where both the second- and third-harmonic NLO processes are type-I. The concept and results from a prototype with output of 28mW at 307nm are presented here.
The main challenge in thin disk laser design is the realization of efficient heat removal from the pumped area by optimizing the heat spreading and the water impingement cooling. This generally requires calculating of the temperature distribution in the disk by numerically solving the heat conduction equation using finite element algorithms. <p> </p>We have developed a simple method to calculate disk temperature profiles that is based on analytically solving the heat conduction equation in Hankel Transform Space. This method can be applied to disks that are mounted on multi-layered, water-cooled heat spreaders, which may include glue or solder layers and dielectric coating layers. This allows parametric optimization of the heat removal process in pumped solid state and semiconductor disks without having to use finite-element programs.
Optically-pumped semiconductor (OPS) lasers are power-scalable, wavelength-flexible, infrared brightness converters.
Adding intra-cavity frequency doubling turns them into efficient, low noise, high power visible laser sources. We report
on a laser combining an InGaAs gain medium with an LBO nonlinear crystal to produce more than 20 Watt CW in
single transverse mode at 532 nm. Efficient cooling of the single gain chip using advanced mounting techniques is the
key to making the laser reliable at high CW powers. A rugged and compact package withstands significant
environmental excursions. The laser's low noise makes it suitable for demanding Ti:Sapphire pumping applications.
The design and experimental testing of an Optical Parametric Oscillator generating 2 Watts of continuous wave radiation
at 3.5 micron is presented.
The oscillator uses a KTA (Potassium Titanyl Arsenate) crystal as the nonlinear medium, pumped by the 1.06 mm
intracavity radiation of an Optically Pumped Semiconductor Laser (OPSL).
A review of the nonlinear characteristics of KTA is presented, and design criteria for the OPSL intra-cavity pumped
OPO are given.
The experimental results are presented and discussed.
Optically-pumped semiconductor lasers provide efficient laser sources in the ultraviolet by intra-cavity nonlinear
frequency tripling. A laser combining InGaAs gain media with LBO nonlinear crystals produces hundreds of mW CW at
355 nm. A compact package that combines thermal and opto-mechanical stability is the key to making this laser robust
and manufacturable. A temperature controlled, monolithic aluminum base supports opto-mechanical mounts made from
low expansion alloys and ceramics to create a resonator that can withstand substantial environmental excursions.
Phase aberrations play an important role in shaping the beam and in determining the losses of laser resonators. An
efficient method is presented for modeling arbitrary phase aberrations in a resonator and for computing modes, modal
losses and frequencies in the aberrated resonator. The method is then used to assess the effect of thermal phase
aberrations in lasers where the active medium is a solid state rod, and in lasers where the active medium is an OPS
(Optically Pumped semiconductor). The adverse effect of the thermal aberrations is found to be severe in the case of rod
geometries and small and less significant in the case of OPS lasers. The analysis conducted allows one to identify simple
design criteria that further minimize the effect of thermal aberrations in the case of OPS lasers.
Power-scaling of optically pumped semiconductor lasers (OPSL's) using a resonator with multiple OPS chips is
demonstrated. With a 3-chip cavity and intra-cavity second harmonic generation, we obtain 55W of TEM<sub>00</sub> mode output
at 532 nm and 66 W in multi-transverse mode. In addition, we describe the design of a periodic dynamically stable
resonator that allows scaling to more than 4 chips and demonstrate that the output power scales with the number of chips
in the cavity.
Optically pumped semiconductor material is a complimentary gain medium for rare earth or transition metal doped crystals. The design of several compositions based on GaAs allows the realization of a wavelength range between 710nm and 1180nm. This can be diode pumped and frequency doubled to cover the near UV up to the yellow spectral range. The power is scaleable and we have realized several Watts at 488nm and 460nm. Experimental results will be presented and discussed as well as reliability data to show that this technology has ripened for industrial applications.
We discuss a compact RGB source with ouput power of several watts per color consisting of a red (638 nm) diode and OPS lasers with blue (460 nm) and green (530) nm output. Suitability for display applications is shown by replacing the lamp of a standard Rear Projection TV.
Optically pumped, external-cavity, surface emitting semiconductor lasers (also known as optically pumped semiconductor lasers, OPS lasers, and vertical external cavity surface emitting lasers, VECSELs) generate near-diffraction limited beams from low brightness diode-array pumps. We have demonstrated 30 W cw at 980 nm and 15 W cw at 488 nm in a single spatial mode from these emitters and believe they can be scaled to > 100 W. Potential applications we have explored for such devices include wavelength conversion, spectral and spatial brightness conversion.
We report on the development and testing of a laser system that delivers up to 200 mW of continuous-wave radiation at 198.54 nm in a near diffraction-limited beam, to be used as a source for photolithography mask writing and mask inspection. The source has been developed with the support of International SEMATECH. The laser output is obtained by intra-cavity sum frequency generation in a CLBO (Cesium Lithium Borate) non-linear crystal
Numerical simulations of the pulse build-up in a Q-switched laser reveal a considerable change in the beam spatial profile during the pulse evolution, on a nanosecond time scale. Such changes were measured experimentally, and the measured temporal evolution of the beam profile is shown to be in good agreement with the theoretical results. The time evolution of the spatial profile translates into an evolution of the beam quality parameter M<SUP>2</SUP>; for typical experimental conditions, in a Nd:YAG laser utilizing a variable reflectivity mirror resonator<SUP>1</SUP>, M<SUP>2</SUP> is very close to a value of 1 at the beginning of the pulse, and increases smoothly throughout the pulse to reach a value of approximately 2 in correspondence of the pulse trailing edge.
A Matrix formalism is proposed to treat the propagation of ultrashort light pulses in laser resonators. The existence of
"Gaussian temporal eigenmodes" for laser resonators is discussed, with emphasis on the dependence of the time duration of
such eigenpulses on various parameters of the resonator. Results of computer simulations based on the formalism are