Polycrystalline ceramic laser rods, composed of a cubic solid solution of 89 mole% Y2O3, 10% ThO2, and 1% Nd2O3, were made by a conventional ceramic sintering approach. Rods of this material, called Nd-doped Yttralox (NDY) ceramic, have lasing thresholds between 16 and 30 J when employing a 95% output mirror reflectivity and a pump pulse of 150 μsec; the lasing slope efficiencies are approximately 0.1%. As a reference for comparison, a commercially available Nd-doped glass laser exhibits a threshold energy of 9 J and a lasing slope efficiency of 0.44% under the same testing conditions. Active attenuation coefficients for the NDY rods examined were between 5 and 7% cm−1. The lower values are within a factor of 6 of that found for laser glass. The major contribution to the attenuation coefficients for NDY laser rods, as currently produced, is a result of unidentified submicroscopic scattering centers. Direct observation of the pore size distributions in these highly transparent sintered ceramics reveals that (i) the volume fraction of pores is of the order of 1 ppm, (ii) there is a peak in the pore size distribution between 1 and 2 μm, (iii) pore growth to this size most likely occurs during the sintering process, and (iv) pores are not the major scattering centers responsible for high scattering losses.

Smooth polycrystalline ceramic substrates with enhanced metal adhesion by pulsed excimer laser processing Improved polycrystalline ceramic laser rods. composed of cubic solid solutions of 89-96.5 mole% Y,0 3 ' 10-2.5% ThO,. and 1% Nd,03' were synthesized by a conventional sintering process. This material. called Nd-doped Yttralox (NDY) ceramic. was produced with laser threshold energies lower than that of the best commercially available Nd:glass laser rod and with a lasing efficiency ~94% that of laser glass at 40 J of input energy under pulsed mode conditions. In a similar operating mode a NDY rod. containing 5 mole% ThO, and having dimensions 7.6XO.46 cm. delivered 0.41 J of optical energy when using an input energy of 162 J. a pump pulse of ISO p..sec. and output mirror reflectivity of 70%. The lasing efficiencies depended strongly on the method of powder preparation and processing. composition. and the cooling rate from the sintering temperature. The dependence of the fluorescent linewidth on the NDY composition provides a means of appreciably varying the material gain coefficient. Active attenuation coefficients for AR -coated NDY laser rods were about 2% per cm as compared to 0.76% per cm for an 01 ED-2 laser glass rod measured in the same optical cavity. The absorption component of the optical attenuation was measured to be 0.38% per cm at X = 1.06 p... indicating that the scattering component is the major contribution to the attenuation coefficient. Considerable evidence is presented which shows that submicroscopic scattering centers exist in the solid -solution matrix and are related to composition fluctuations arising from (i) chemical segregation in the starting powder which is not entirely eliminated during the high -temperature sintering process and (ii) the formation of extended defects or ordered zones in the solid -solution phase during specimen cooling from the sintering temperature. 4495

We report high-efficiency high-power uv generation at 266 nm by frequency quadrupling of Nd laser using two deuterated KDP crystals. An angle-tuned type-II phase-matched (eoe-interaction) deuterated KDP crystal is used for doubling 1.064 μm and a temperature-tuned 90° phase-matched deuterated KDP crystal is used, for the first time, for doubling 532 nm to 266 nm. Results indicate that an average uv power of several watts with an over-all quadrupling efficiency of around 20% is obtainable, and that high peak uv power on the order of 10 GW with an efficiency of greater than 35% can be expected for subnanosecond pulses. The high peak uv power is potentially useful for fusion studies.

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The theoretical investigations and experimental verifications of resonant modes of optically pumped solid host face-pumped lasers (FPL) are discussed. The conditions for a single transverse-mode operation for electrooptically Q-switched neodymium glass and YAG lasers are examined in both stable and stable/unstable resonator configurations. Resonant mode computations were made, based on a Gaussian quadrature and a complex non-Hermitian matrix program.