High data rate laser transmitter based on a diode double end-pumped Nd:YAG laser with linearly polarized output for free space laser communication

Abstract

Optically pumped solid-state lasers with Nd:YAG may have to operate over a wide range of temperatures. We designed and fabricated a diode double end-pumped Nd:YAG laser for free space laser communication. Various laser beam parameters have been characterized for the same application. The temperature dependence of the effective stimulated emission cross section for 4 F 3/2 → 4 I 11/2 transition and fractional thermal loading of Nd:YAG are determined using a planar resonator with two collimated and focused pump beams from fiber-array package laser diodes at 808 nm. The pump power-induced thermal lensing is used to stabilize the cavity. The diode double end-pumped Nd:YAG laser possesses an extremely good beam profile that exactly matches the theoretical Gaussian intensity distribution up to a diode current of 30 A. After that the ellipticity slightly increases, indicating deviation from the circular symmetry of beam, which may be due to the thermally induced birefringence of the Nd:YAG crystal offered to the polarized laser beam. The thermal lens focal length decreases with an increase in the absorbed pump power, similar to the case of a lamp pumped Nd:YAG laser and a diode pumped Nd: YVO 4 laser. All the results indicate that the laser beam characteristics are useful for high data rate free space laser communication links.

Demonstration of a free-space optical communication system using a solar-pumped laser as signal transmitter

“…The output from diode lasers pumps solid-state lasers, as only the output from solid-state lasers can be used for FSO communication due to the requirement for high beam quality in a long distance in space. There are several energy converting steps, each step causes losses and complicity for maintenance [4][5][6].…”