GTE GOVERNMENT SYSTEMS CORP MOUNTAIN VIEW CA SYLVANIA SYSTEMS GROUP-WESTERN D IV
This report describes the efforts on a 10 month program whose objective was the design, development and delivery of a mode-locked internally frequency doubled NdYAG laser operating at 500 MHz prf with an average output power of 250 mW at 0.53 micrometers or 1.0W at 1.06 micrometers TEM Sub oo mode with a pulse width of less than 300 ps measured at 10 amplitude points. Further constraints were that the laser be conduction cooled and the maximum power into the pump lamp be 250W. The approach utilized a 4 mm bore diameter, protected end seal Potassium-Rubidium K-Rb lamp as a pump source in a cold mirror pump cavity with a 3 mm diameter by 54.5 mm long rod conductively cooled with heat pipes. A three mirror L shaped resonator was used to allow efficient coherent combination of the two green beams generated in a 5 mm cube Barium-Sodium-Niobate BSN crystal. The internal 1.06 micrometers beam was focused into the doubling crystal with a 7.5 cm focal length lens. Modelocking at the cavity c2L frequency was achieved with both an acousto-optic modulator and an electro-optic modulator. The doubler crystal served as the electro-optic modulator material. During the program, it was determined that great enough mode-locking depth was not available from state-of-the-art mode-lockers to allow for short pulses simultaneously with high conversion rate to the green.