Optimization of Q-switched lasers

The authors extend the standard rate equation analysis to obtain expressions for the maximum peak power, maximum pulse energy, and minimum pulsewidth of a single Q-switched output pulse; the maximum power efficiency of a repetitively Q-switched laser; and the corresponding cavity output couplings. Results are obtained analytically and numerically, and a comparison of the two sets of results is made. As a first step in this process the authors derive general expressions for the peak power, pulsewidth, pulse energy, and power efficiency. The authors next differentiate these expressions in order to find the maxima or minima that optimize the parameter of interest. Differentiation is done with respect to the cavity output coupling     

Three-dimensional imaging laser radar with a photon-counting avalanche photodiode array and microchip laser

We have developed a threedimensional imaging laser radar featuring 3-cm range resolution and single-photon sensitivity. This prototype direct-detection laser radar employs compact, all-solid-state technology for the laser and detector array. The source is a Nd:YAG microchip laser that is diode pumped, passively Q-switched, and frequency doubled. The detector is a gated, passively quenched, two-dimensional array of silicon avalanche photodiodes operating in Geigermode. After describing the system in detail, we present a three-dimensional image, derive performance characteristics, and discuss our plans for future imaging three-dimensional laser radars.     

Miniature eye-safe laser system for high-resolution three-dimensional lidar

A microchip-laser-pumped optical parametric amplifier produces 35-microJ, 1.537-microm pulses of 190-ps duration at 8 kHz, in a near-diffraction-limited output beam with a Fourier-transform-limited spectrum. The flight-ready laser head is pumped by 20 W of optical power from two fiber-coupled laser-diode arrays, occupies a volume of 0.14 liters, and has a mass of 0.34 kg.     

The effects of spatial hole burning and energy diffusion on thesingle-mode operation of standing-wave lasers

Spatial hole burning in the absence of energy diffusion is examined. A formula is derived which predicts how far above threshold a homogeneously broadened standing-wave laser operates in a single-longitudinal mode. This is a conservative formula, since energy diffusion decreases the effects of spatial hole burning and increases the power level at which single-mode operation can be maintained. The role of energy diffusion is also examined. A formula is derived for how far above threshold a standing-wave laser oscillates in a single-longitudinal mode when energy diffusion is accounted for. Examples of the use of these formulas are given     

Miniature, pulsed Ti:sapphire laser system

A robust, miniature Ti:sapphire laser system produces 18.4-/spl mu/J, 780-nm pulses of 700-ps duration and 0.17-nm linewidth at 8 kHz. The system is pumped by two fiber-coupled 808-nm laser diode arrays and occupies a volume of <0.5 liters. The OCIS codes are (140.3580) for solid-state lasers and (140.3480) for diode-pumped lasers.     

Diode-pumped composite-cavity electrooptically tuned microchiplaser

A diode-pumped composite-cavity electrooptically tuned microchip laser has been constructed that tunes up to 30 GHz. The laser incorporates a LiTaO₃ electrooptic tuning element with acoustic damping to provide linear voltage-to-frequency conversion with a tuning sensitivity of ≈14 MHz/V at modulation frequencies from DC to >1.3 GHz     

Microchip optical parametric oscillators

The frequency-doubled output of a high-power passively Q-switched Nd:YAG microchip laser has been used to pump a KTP doubly resonant miniature monolithic Fabry-Perot (microchip) optical parametric oscillator (OPO). The OPO operated with 20% conversion efficiency, generating 8.4 /spl mu/J of 1.064-/spl mu/m radiation in 600-ps pulses, with excellent mode quality and pulse-to-pulse stability. This is the most compact OPO system yet demonstrated, generating the shortest pulses reported for an OPO pumped with Q-switched pulses. This technology makes it possible to obtain miniature optical system operating at any wavelength throughout the near IR, visible, and UV.     

Pump-induced bleaching of the saturable absorber in short-pulse Nd:YAG/Cr/sup 4+/:YAG passively Q-switched microchip lasers

Bleaching of the saturable absorber by pump light increases the length of the pulse generated in a passively Q-switched Nd:YAG/Cr/sup 4+/:YAG microchip laser and decreases the pulse energy. This effect is greatest when transmitted pump light is nearly focused in the Cr/sup 4+/:YAG and when pumping is sufficiently intense to bleach the absorption of the Nd:YAG. Both effects are important in short-pulse microchip lasers. The maximum repetition rate of a passively Q-switched Nd:YAG/Cr/sup 4+/:YAG microchip laser is correlated with the pulsewidth. In general, it decreases as the pulsewidth gets shorter.     

Diode-pumped 214.8-nm Nd:YAG /Cr4+:YAG microchip laser system for the detection of NO

A passively Q-switched 214.8-nm Nd:YAG/Cr(4+):YAG microchip laser system for the detection of NO was designed, constructed, and tested. The system uses the fifth harmonic of the 1.074-microm transition in Nd:YAG to detect NO by laser-induced fluorescence. A significant challenge was the development of an environmentally stable coating to provide the necessary discrimination between the 1.074-microm laser line and the stronger transition at 1.064 microm. The exact position of the fifth-harmonic frequency was determined by use of NO fluorescence excitation spectra to be 46556 +/- 1.5 cm(-1). With a pulse energy of approximately 50 nJ of fifth-harmonic light, we observed a detection sensitivity for NO of approximately 15 parts per billion by volume in a simple, compact optical system.