| 研究実績の概要 |
In this fiscal year, experimental and theoretical studies of the laser resonator using a reflective axicon lens (AL) with 90 degrees apex angle as a high-reflective element in the resonator were performed. The resonator stability conditions were determined by calculations. A laser based on cryogenic Yb:YAG TRAM with exchangeable high reflection elements; (a) flat mirror (Fabri-Perot (FP) resonator) and (b) AL retro-reflector, were designed and constructed.
The output power efficiency vs. the pump power, near- and far field intensity profiles, were monitored and analyzed. Experimental results for both resonator cases have been compared. In contrast to FP resonator output, from AL resonator a donut-like flattop intensity profile was obtained. The laser threshold and the slope efficiencies were estimated to be 235 W/cm2 and 0.5, and 470 W/cm2 and 0.4, for FP and AL resonators, respectively. From AL resonator, ~ 24 W output power at 90 W absorbed power was obtained. It was shown that at moderate pump powers thermal effects hardly affect the main features of the beam intensity profiles. However, at higher pump powers the system was unstable.
Marked increase of the laser threshold for AL resonator is explained by the small beam diameter (~ 1.8 mm), incurring fractionally large losses due to the scattering on the tip of the AL.
|
| 現在までの達成度 (区分) |
現在までの達成度 (区分)
3: やや遅れている
理由
We have planned measuring the beam quality (M2) and the wavefront error of the AL resonator output at high pump/output powers, however, the cryogenic laser system was not stable enough (due to LN2 pool cooling).
We intend doing these comparative measurements at ambient temperature laser system which will be constructed during the final year of the project.
|
