:YAG crystal Saturable Absorber for NASA SLR Stations

Since 1983, the current network of NASA Satellite Laser Ranging (SLR) stations used an Nd:YAG oscillator cavity in an active-passive configuration to generate 150-200 psec (2mj) 1064nm pulses for satellite ranging. This cavity (active-passive) used a liquid (chlorobenzene) dye cell as the passive saturable absorber. The dye consisted of Exciton (Kodak-9740) Q-Switch I dye and monochlorobenzene as a solvent. The dye mixture would degrade during use and would require daily maintenance. Chlorobenzene is a hazardous substance that requires special handling equipment and procedures. The dye cell was replaced with a Cr 4+ :YAG crystal used as a saturable absorber in an active-passive mode-locked Nd:YAG laser. The new absorber requires little or no daily maintenance and the improved stability and laser performance is equal to or better than the dye cell. Pulse widths of 150psec were easily obtained and output energy variations of less than 10% shot to shot.