Potassium lithium niobate (KLN), a nonlinear optical material with high nonlinearity and other desirable properties,
has the potential to improve the performance and reduce the cost of blue and UV lasers. KLN crystals have not entered
the commercial mainstream because it is impossible to grow them reproducibly by conventional techniques. We have
developed a proprietary process based on the laser heated pedestal growth (LHPG) technique that eliminates technical
barriers to manufacturing KLN crystals.
This paper describes the LHPG method of KLN crystal growth including improvements in crystal uniformity and
transparency, and our latest harmonic generation results in the UV.
A CW diode-pumped alkali laser (DPAL) based on the D1 rubidium resonance transition has been investigated. The
pump sources for these experiments are two 780 nm fiber-coupled diode modules, incorporating volume holographic
gratings for wavelength control. Total pump power is up to 64 W. Rb laser output at the 794.8 nm fundamental
wavelength is up to 7.8 W. Intracavity second harmonic generation in BIBO generates up to 250 mW at 397.4 nm.
The CW diode-pumped alkali laser (DPAL) based on the rubidium resonance transition at 794.8 nm has been
investigated. The pump sources for these experiments are commercially available 780 nm fiber-coupled diode modules,
incorporating volume holographic gratings for wavelength control. Operating characteristics, pump architecture, power
scaling and lifetime limitations have been studied. To date, lasers pumped by single 20 W diode bars have produced
over 1 W output at 794.8 nm and 100 mW at the 397.4 nm harmonic. Lasers pumped by two 40 W diodes generate
almost 8 W at 794.8 nm.
A measurement station to examine the longitudinal mode structure of Q-switched solid state lasers on a single
pulse basis is presented. The key component is a Fabry-Perot interferometer (FPI) providing a high finesse to
not only display the full spectral emission bandwidth but also resolve single modes of high gain laser media
such as Nd : YVO4. In addition the setup allows one to link relative pulse energy data to each recorded fringe
pattern. It is then used to quantify the spectral information of three lasers with a cavity length of up to 200mm
to evaluate correlations among pulse stability, pulse repetition frequency and spectral emission characteristics.
The optical approach implies a decaying finesse from approximately 250 to 60 across the measurement range.
Therefore the setup can only partially resolve single longitudinal modes of lasers with a cavity length greater
than 130mm but still gives a qualitative picture of the emission bandwidth that allows a deeper understanding
of the spectral characteristics and thus points the direction for performance improvement.
Norman Hodgson, Kim Griswold, Wilhelm Jordan, Steve Knapp, Amy Peirce, Christopher Pohalski, Emily Cheng, John Cole, Dave Dudley, Alan Petersen, William Nighan
The performance of end-pumped YAG and YVO4 lasers in fundamental mode operation (M2 < 1.1) is reviewed and the physical limits of TEM00 output power is discussed. By using special resonator configurations, end-pumped lasers can be designed to provide high-power, excellent beam quality, and high-efficiency in spite of the large phase distortions commensurate with the strong aberrated thermal focusing. A 35 W infrared Nd:YVO4 laser was developed with a quantum efficiency of 94%, defined as a percentage of 1064 nm photons generated per quantity of absorbed 809 nm pump photon. A Q-switched end-pumped Nd:YAG laser provides an average output power greater 15 W in a polarized TEM00 mode with 29% optical efficiency at 1064 nm. External frequency doubling and tripling of this laser resulted in maximum output powers of 8.8 W and 4.2 W, respectively.
The emergence of commercially available diode pumped solid state lasers in the 3-10 watt power range has created alternative laser sources for many light industrial applications. Laser marking, micro-machining, resistor trimming, disk texturing, and rapid prototyping are some of the applications which can benefit from this technology. In this paper, we describe fiber-coupled diode bar pumped Nd:YAG and Nd:YVO4 lasers with short pulse, high energy, and relatively high average power developed for these applications. Our design emphasizes system efficiency and simplicity to minimize the cost of ownership. The excellent beam spatial quality and pulse-to-pulse stability of these devices results in improved process yields for the end user.
A variety of applications require short, energetic laser pulses delivered at high repetition rate. These include micro-machining, range finding, and scientific applications such as amplifier pumping. An important advantage provided by diode-end-pumping of solid state lasers is that this type of geometry allows the generation of short, energetic, Q-switched pulses at high repetition rate. The high peak power of such pulses facilitates harmonic generation. In this paper, we describe a high average power, high repetition rate Q-switched Nd:YVO4 laser, pumped by a fiber-coupled diode bar. The laser provides pulses of excellent spatial quality at repetition rates up to 100 kHz, average power 3-4 W, and durations of 8 to 20 nsec. The near-diffraction-limited beam and the high peak power allow efficient harmonic generation at high repetition rates. Second harmonic generation is achieved in non- critically-phase-matched LBO with a conversion efficiency of 55% at 20 kHz, providing an average power of 1.75 W at 532 nm. third harmonic generations (to 355) in LBO has been achieved with > 20% efficiency, resulting in an ultraviolet average power of 0.65 W at 20 kHz.
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