Injection seeded, diode-pumped, short pulse neodymium:YAG ring laser for space based laser ranging

In the near future, NASA plans to deploy LIDAR (Light Detection And Ranging) systems in space for the purpose of measuring geophysical quantities such as tectonic plate movement, crustal deformation near faults, and volcanic activity. Information on other quantities such as ice floes, cloud movement heights, and sea levels are also of interest. These measurements will require a spaceborne laser system which can operate unattended for extended periods of time and be able to make reliable sub-centimeter distance determinations from space. One system concept is the Geodynamic Laser Ranging System (GLRS) (Cohen et al. 1987). Optical pulses of 100 ps, or less, will be required from a Nd:YAG laser. The fundamental wavelength will provide altimetry information while the second and third harmonic frequencies will be generated to measure distances with high accuracy through two-color ranging techniques. Sub-100 ps pulses can be produced using either pulse pumped or continuous wave (cw) pumped mode-locked lasers. Shorter pulses are frequently achieved through cw pumping but the pulse energy is low, typically less than 10$\sp{-8}$ J. A method of achieving the pulse width of a cw mode-locked laser and pulse energy of a pulse pumped laser involves using regenerative amplification. The presented work covers one possible method of short pulse amplification. A pulsed Nd:YAG ring regenerative amplifier, pumped by laser diode-arrays and injection seeded by a 100 ps source, has been constructed. It was shown that high total optical gains can be achieved while holding the stringent alignment and timing specifications of regenerative amplification to a minimum. The construction of this laser/amplifier provided data on the behavior of 100 ps pulses when used as a temporal seed in a typical oscillator cavity with multiple optical surfaces.