MOPA Laser Transmitter with Passive Q-Switch for Space LIDAR

The use of a Passive Q-Switch (PQS) in a high power MOPA configuration with multiple tens of watts output will enable a smaller, compact, lightweight lidar transmitter with significantly increased reliability over existing legacy transmitters for space applications. The proposed MOPA transmitter will reduce transmitter size and weight by integrating a Passive Q-switch (PQS) into the master oscillator, which will eliminate the Active Q-switch (AQS) used in high power MOPArsquo;s. Replacing the AQS with a PQS eliminates the high voltage power supply, high voltage AQS driver, and intracavity AQS crystal. This also eliminates the sensitive alignment and locking of the intracavity AQS and mount. Cr:YAG PQS crystals have been used as a separate component in a resonator to produce Nd:YAG and Nd:YVO4 PQS lasers.They can be designed to produce longer output pulse widths around 8-10 nsec and use QCW laser diode pumping to fix the laser rep rate. The MO output can be amplified up to the level required for lidar applications.nbsp;The proposed transmitter will use a Carbon Fiber (CF) optical bench to reduce weight and increase stiffness in an aluminum housing. The resonator,nbsp;amplifiers and second harmonic generationnbsp;optics and mounts will occupy the top side of the optical bench, with the beam expandernbsp;located on the bottom side. Two amplifiers will be used with the MO to amplify the energy per pulse up to 5-10 mJ at 4.0-5.0 kHz rep rate, depending on application requirements. The MOPA output can be configured with SHG, THG and OPO wavelength conversion options to operate from the UV to IR.nbsp;For environmental monitoring applications the laser will operate at 1064 nm and 532 nm. We propose the engineering model phase IInbsp;deliverable laser to be configured with 6 mJ total output energy/pulse at 4 kHz rep rate, with 3 mJ at 1064 nm, and 3 mJ at 532 nm, and anbsp;proposed rep rate ofnbsp;4 kHz and pulse width of 10 nsec. The laser will use Nd:YVO4 laser slabs pumped at 878.6 nm with VBG stabilization.