The typical approach for producing laser output at the 1651-nm wavelength is via nonlinear frequency conversion. Lasers based on nonlinear conversion are complex, and it is very difficult to provide stability over time and over a wide range of operating temperatures. The efficiency of such optical sources is also low. A much more promising approach is the use of active media that allows for the development of solid-state lasers (SSL) with spectral emission at 1651 nm. An important requirement for this active medium is the ability to support in-band pumping with a low quantum defect since this approach leads to significant improvement in efficiency of SSLs and excellent beam characteristics due to low thermal stress of the active media.
The technology being reported involves the development of an efficient SSL for methane detection at 1651 nm. One intended application of this technology is for use in active remote sensing optical instruments, such as those used in NASA’s ASCENDS, ACE, and Doppler Wind LIDAR programs. The novel approach is to utilize low-erbium-doped yttrium gallium garnet as the active media, combined with in-band resonant pumping near 1468 nm to create SSLs and power amplifiers operating at 1651 nm.
An yttrium gallium garnet doped with a low concentration of erbium acts as a potentially ideal active medium to support the operation of efficient SSLs with spectral emission 1651 nm. The broad gain spectrum (>1 nm) of this medium also allows for sufficient spectral tuning to achieve methane detection utilizing path differential absorption techniques. This active media allows in-band pumping with a very small quantum defect (≈11%), defined as the difference between the emission wavelength (i.e., 1651 nm) and the pump wavelength (i.e., ≈1468 nm).
This work was done by Igor Kudryashov of Princeton Lightwave Inc. for Goddard Space Flight Center. GSC-16735-1