High-efficiency 2 µm Tm:YAP laser with a compact mechanical Q-switch.

We describe a compact, highly efficient, diode-pumped, mechanically Q-switched Tm:YAP laser operating near 2 µm. The Q-switch, based on a torsion spring resonant mirror scanner, had negligible optical loss and required very low electrical drive power. At a 10 kHz pulse repetition frequency, the laser generated an average output power of 10.5 W at 1.94 µm, Q-switched pulse energy of 1.05 mJ, a pulse length of 31 ns, and a peak power of 34 kW. The Q-switched laser exhibited maximum optical and electrical efficiencies of 51% and 26%, respectively.

Narrow-band 1 W source at 257 nm using frequency quadrupled passively Q-switched Yb:YAG laser.

We describe generation of 1.1 W of 257 nm emission by frequency quadrupling the 1030 nm emission from a compact passively Q-switched Yb:YAG laser. The laser utilized a volume Bragg grating to achieve a 0.1 nm linewidth required for UV-Raman spectroscopic applications, generated 100 kW peak power, 250 µJ pulses and 3.6 W of average power at 1030 nm. Fourth harmonic generation (FHG) was carried out using a 10 mm lithium triborate (LBO) crystal to generate 515 nm second harmonic with 70% conversion efficiency, followed by a 7 mm beta-barium borate (BBO) crystal to generate 257 nm fourth harmonic with 45% efficiency, resulting in an overall nonlinear conversion efficiency of 31%. Far-field and near-field of the FHG emission were characterized.

Improved Monoblock laser brightness using external reflector.

The Monoblock laser has become the laser of choice in long-range, eye-safe laser range finders. It is eye-safe with emission at 1570 nm, high pulse energy, simple construction, and high efficiency when pumped by a laser-diode stack. Although the output beam divergence of a typical Monoblock with a 3 mm×3 mm cross section is relatively large (10-12 mrad), it can be reduced to <1 mrad using a telescope with large magnification. In this paper we present a simple and compact technique for achieving significant reduction in the Monoblock beam divergence using a partial reflector that is placed a short distance from the optical parametric oscillator (OPO). Using a 38 mm long Monoblock with a 10 mm long potassium titanyl phosphate OPO, we achieved a beam divergence of <4 mrad, corresponding to a >2.5× reduction from the unmodified laser. Performance using this technique with various feedback and etalon spacings is presented.

End-pumped 1.5 microm monoblock laser for broad temperature operation.

We describe a next-generation monoblock laser capable of a greater than 10 mJ, 1.5 microm output at 10 pulses/s (pps) over broad ambient temperature extremes with no active temperature control. The transmitter design is based on a Nd:YAG laser with a Cr4+ passive Q switch and intracavity potassium titanyl phosphate optical parametric oscillator. To achieve the repetition rate and efficiency goals of this effort, but still have wide temperature capability, the Nd:YAG slab is end pumped with a 12-bar stack of 100 W (each) diode bars. Different techniques for focusing the pump radiation into the 4.25 mmx4.25 mm end of the slab are compared, including a lensed design, a reflective concentrator, and a lens duct. A wide temperature operation (-20 degrees C to 50 degrees C) for each end-pumped configuration is demonstrated.

Effect of dispersion on the operation of a KTP electro-optic Q switch.

The effect of dispersion on the operation of a KTP electro-optic Q switch was investigated. A KTP crystal in the normal orientation has been successfully operated as a Q switch. The experiment was performed with a laser resonator containing a Nd:YLF crystal end pumped with a cw diode-laser array. A pulse length of approximately 100 ns was obtained at a repetition rate of 1 KHz. Temperature tuning was used to eliminate static phase retardation. The effect of dispersion was found to affect Q switching. Wavelength stabilization was performed to counteract the effect of dispersion. These measures allowed us to achieve Q switching action.

3-W continuous-wave diode-pumped 532-nm laser.

A cw diode-pumped Nd:YAG laser is mode locked at 80 MHz and produces 5.5 W of output at 1.064 microm. Intracavity frequency doubling by using KTP produces 3 W of mode-locked output at 0.532 microm.

Efficient optical parametric oscillator at 1.6 microm.

We extend the operating regime of diode-pumped Nd:YAG lasers into the eye-safe region at 1.61 microm by using an efficient optical parametric oscillator in KTP. Total energy conversion efficiencies of the 1.06-microm pump to 1.61-microm signal and 3.1-microm idler approach 40%, with 25% converson to 1.61microm alone. This device has a wallplug efficiency of 0.8%, producing 2.5-mJ output energies at an eye-safe wavelength, and is readily scalable to higher energies.

High-power diode-array-pumped frequency-doubled cw Nd:YAG laser.

We report the demonstration of a diode-array-pumped Nd:YAG laser with a cw output of 3.3 W at 1.06 microm. The laser was side pumped using linear diode arrays focused with cylindrical optics to provide efficient spatial overlap between the pump and cavity modes. Intracavity doubling using KTP produced 0.76-W output repetitively Q switched at 532 nm. The electrical efficiency for the 1.06-microm output was 3.5%.