腔内布氏角声光反馈的低噪声稳定氦镉激光

本文研究了氦镉激光4416Å的噪声和输出功率稳定特性,得到噪声频谱、噪信比与放电电流,工作气压的关系。提出用腔内布氏角插入声光反馈器伺服反馈,抑制氦镉激光噪声和提高功率稳定性的方法,获得满意的实验结果.声光反馈器为厚6mm的熔石英,换能器为铌酸锂,工作频率为40MHz,用Raman-Nath衍射调节腔内损耗.输出35mW经伺服,噪信比由6.3%降为1.5%,2Hz到200kHz噪声幅值都有显著抑制,功率起伏由11.6%降为3.7%,光损耗14%,获得输出30mW大功率低噪声氦镉激光.在最佳放电参数下,可使抑制后噪信比为0.8%.该方案适用更大功率的氦镉激光器.

LOW NOISE STABLE He-Cd LASER OF A-O FEEDBACK AT BREWSTER ANGLE IN CAVITY

The noise characteristic and the stability of He-Cd lager at 4416Å have been investigated. The noise spectra and the relations between noise and discharge current as well as He pressure have been measured. The method of using the A-0 feedback at Brewster angle in cavity is introduced to reduce the noise of He-Cd laser and the results have been good. The A-O device is 6 mm thick quartz, 40MHz in frequency. The transducer is made of the crystal LiNbO₃, being operated in Raman-Nath diffraction to modulate the cavity loss according to the laser power, after operating che device, the noise ratio decreases from 6.3% to 1.5% and all the noise amplitudes tan be obviously reduced in the band from 2 Hz to 200 kHz, the fluctuation of laser output power comes down from 11.6% to 3.7% and the laser power decreases from 35mW to 30 mW with the optical loss 14%. By changing the discharge parameters, the high power with low noiso He-Cd laser having noise ratio 0.8% and output power 33mW may be abtained. There is no need to change the laser structure for this method, which may be applied on the He-Cd laser having higher power and other lasers.