Ralph L. Burnham

Efficient Raman conversion of XeCl-laser radiation in metal vapors

The output from a discharge-pumped XeCl laser (75-mJ, 25-nsec FWHM at 308 nm) has been converted to several wavelengths in the visible spectrum through stimulated electronic Raman scattering in vapors of Ba, Ti, Pb, and Bi. Energy-conversion efficiencies of up to 40%6 have been reached in initial experiments.

High-average-power KTiOAsO4 optical parametric oscillator.

Using noncritically phase-matched 1-cm(2) -aperture KTiOAsO(4) (KTA) crystals in an optical parametric oscillator (OPO), we have demonstrated a sustained average signal power of 33 W at 1534.7 nm. To our knowledge, this is the highest-average-power signal ever generated by an OPO. The pump source was a 100-Hz Q -switched 1064-nm Nd:YAG laser. Compared with that of the similar and more-common material KTiOPO>(4) , idler absorption in KTA is negligible, allowing high-power operation with minimal thermally induced refractive distortion in the OPO crystal.

Near-diffraction-limited laser beam shaping with diamond-turned aspheric optics

We used a pair of diamond-turned CaF(2) aspheres to convert the pure TEM(00) Gaussian spatial profile output of a diode-pumped Nd:YAG laser oscillator into a super-Gaussian intensity profile with a nearly flat phase front. The resulting super-Gaussian beam was nearly diffraction limited with an M(2) of 1.75; in the near field the 5-mm diameter beam retained a nominally flat-top intensity distribution without significant diffraction peaks for an excellent working distance of more than 50cm. A 10% improvement in amplifier-energy extraction obtained by use of the reshaped beam is demonstrated.

Highly efficient optical parametric oscillators

An eyesafe source (1.61 micrometers ) with 1.1% wallplug efficiency, is demonstrated using a Nd:YAG pumped KTP optical parametric oscillator with peak-power conversion efficiencies of 70%. Joule-level scaling, kHz repetition-rates, and ns pulselengths are now accessible using this technology.

Near-diffraction-limited, high-energy, high-power, diode-pumped laser using thermal aberration correction with aspheric diamond-turned optics

We achieved a 1.3× diffraction-limited output beam with a pulse energy of 0.76 J at 60 Hz (average power of 46 W) at 1.064 μm from a diode-pumped Nd:YAG master oscillator power amplifier rod laser using a diamond-turned aspheric optic to compensate thermally induced phase distortion of the gain medium. The output was frequency doubled in KTP to 30 W (0.5-J pulse energy) and 2.4× diffraction-limited at 532 nm.

Diode-pumped 1.34-μm Nd 3+ :YAlO 3 laser

We have pumped Nd(3+):YAlO(3) lasers with a 40-stripe, 500-mW, 807-nm diode laser. Maximum output powers at 1.34 microm of 26 mW multimode and 20 mW in a single transverse mode were achieved. The several longitudinal modes had a total spectral width of ~0.4 nm.

Devices: Visible and UV lasers: Problems and promises: New families of gas lasers are expected to deliver a range of pulse intensities, durations, and wavelengths for diverse applications

New families of gas lasers are expected to deliver a range of pulse intensities, durations, and wavelengths for diverse applications.

Diode-pumped solid state lasers with kilowatt average power

In this paper we discuss progress toward the development of kilowatt-class diode-pumped lasers with beam quality approaching the diffraction limit. The development of high- efficiency, high-brightness lasers will open new applications for precision laser machining. The design and performance of diode-pumped Nd:YAG lasers with average powers in the kilowatt range are addressed. Fibertek, Inc. is presently developing laser systems at this power level for industrial applications such as drilling, cutting, and welding. This work has a goal of producing 0.5 to 2.5 kW average power with less than four times diffraction-limited beam quality (2.6 mm - mr, D(Theta) /4). Both rod and slab architectures are under development. This talk covers initial results with diode-pumped rod lasers operating at up to 500 W average power.

All-solid-state diode-pumped eyesafe lasers

An eyesafe source at 1.61 J.UD with 2.1 % wallplug efficiency, is demonstrated using a Nd:YAG pumped KTP optical parametric oscillator with total peak-power conversion efficiency of 70% and an energy conversion efficiency of 47 % to 1.61 J.UD or 30% to l.54J.UD.

Multiband generation of mid infrared by use of periodically poled lithium niobate

We report the generation of simultaneous multiband mid-infrared laser output by use of periodically polled lithium niobate pumped by the 1.54-microm output from a KTP optical parametric oscillator. The multiband source is capable of producing three mid-infrared wavelengths ranging from 2.5 to 4microm . In initial experiments we obtained output powers of 542 mW near 2.5microm and 453 mW near 4microm , with power conversion efficiencies of 30% and 25%, respectively. To the best of our knowledge, this is the first demonstration of this kind in the literature.