| 研究実績の概要 |
Polarization properties and lasing characteristics of axicon lens (AL) and corner-cube retro-reflector (CCR) resonators have been studied theoretically and experimentally.
At cryogenic temperatures, the laser threshold and the slope efficiencies were estimated to be about 0.7 kW/cm2 and 0.5, 1.18 kW/cm2 and 0.4, and 1.5 kW/cm2 and 0.33 for FP (Fabry-Perot), AL and CCR resonators, respectively. Marked increase of the laser threshold for AL and CCR resonators is explained by the small beam diameter on those elements, incurring fractionally large losses due to the scattering on the tip of the AL and three corners of the CCR, respectively.
At ambient temperatures, the laser threshold and the slope efficiency could be estimated only for FP resonator: 0.74 W/cm2 and 0.5, respectively. Although lasing for AL resonator was observed, too, the pump power was not enough for accurate estimation of the laser slope and threshold. No lasing could be observed for the CCR resonator.
Unfortunately, the coherence properties of the AL resonator output cannot be studied for the particular case of TRAM active medium configuration. This is because the output beam polarization for TRAM configuration cannot be controlled due to the phase jumps caused by total internal reflection.
Although several characteristics of resonators with retro-reflecting elements have been recognized, more detailed investigations using CW systems are hindered by the insufficient pump densities. The benefits of CCR and AL resonators could be obtained in laser systems with pulsed regime operation.
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