High Energy, Diode-Pumped, Nd:YAG Laser for Space-Based Lidar

Lidar systems are powerful tools for a wide range of remote sensing applications. These include precision distance measurements, target detection, designation, and imaging, and the mapping of chemical species concentrations. The transition of lidartechnology into space will provide a powerful tool for defense and commercial applications. For space-based measurements, lasers with a near diffraction limited beam quality and pulse energies on the order of 1 J are often required. Higher repetitionrates increase the data acquisition rate. We are proposing to investigate 1 ¿m laser designs that can provide 1 J/pulse at 100 Hz in a robust and compact package suitable for space.Our approach is based on an oscillator/amplifier design. The design incorporates diode-pumped, conductively cooled zigzag slabs as the gain media. The oscillator is an innovative application of polarization output coupling to a ring resonator to achievea high beam quality with pulse energies on the order of 250 mJ. By starting with higher energy oscillator pulses we can achieve a more compact overall system. Proof of principle resonator measurements and scaling analysis will be performed in Phase I.The addition of amplifiers to achieve the final 0.5 -1 J output would occur in Phase II. There is commercial, DOD, and NASA interest in the development of state of the art, diode-pumped lasers to use in a variety of space-based lidar systems. The purpose of these lidar systems include tracking, imaging, and identification of objects nearearth, in deep space, on land, and under water. There is also a growing interest, for both environmental monitoring and national security reasons, in the application of lidar systems to the sensing of trace levels of chemical and biological materials.Another active area of both commercial and NASA interest is lidar based wind measurements. Because of the large distances involved, large laser pulse energies are frequently required to achieve an adequate signal-to-noise from the lidar system. The classof laser of interest is in the 1 J, 100 Hz range. The higher repetition rates allow the opportunity for faster data acquisition for rapidly changing scenes of interest. Diode-pumped, 1 ¿m solid-state lasers are a relatively mature technology and are goodcandidates for use as the primary laser or as the pump source for generating other wavelengths at the required pulse energies. In order to minimize the output and receiver optics, as would be needed for a space-based system, it is also desirable that theoutput from the laser be near diffraction limited.Although diode-pumped 1¿m lasers with the properties described above have been demonstrated for commercial and R&D applications, considerable development is still required to build the robust systems that would be needed for space-based and otherfield-based systems. Our SBIR proposal is intended to develop a high pulse energy Nd:YAG laser that can meet the needs of such lidar systems.