纳秒脉冲激光抽运下的铯蒸气电离度研究

为了研究碱金属蒸气电离对半导体抽运碱金属激光器(DPAL)定标放大的影响, 采用适宜于短脉冲激光抽运源的光电流法来测量碱金属蒸气电离度, 并开展了铯蒸气电离度同激光抽运功率密度、碱金属池温度、抽运激光器重复频率之间关系的实验研究。结果表明, 在不考虑热效应的情况下, 即使抽运激光的功率密度高达3×108W/cm2、碱金属池温度150℃、氦气缓冲气压力9.33×104Pa条件下, 铯蒸气的电离度也仅仅达到1%左右; 在碱金属池温度从122℃升高至163℃的过程中, 相对于铯蒸气粒子数密度的显著增大, 铯蒸气电离度的变化非常小。该研究结果对于铯DPAL通过增加抽运激光功率密度和提高碱金属池温度进行定标放大具有非常积极的意义。

Ionization degree measurement of cesium vapor medium pumped by a nanosecond pulse laser

In order to study the effects of alkali vapor ionization on the scaling potential of diode pumped alkali lasers (DPAL), a photocurrent method suiting for measuring the ionization degree of alkali vapor that pumped by a short-pulse laser has been established. By using the photocurrent method, ionization degree of cesium vapor was measured versus different power density of pump laser, temperature of alkali cell, and repetition frequency of the pump laser. Experimental results show that the ionization degree of cesium vapor is merely around 1% even if the power density of the pump laser has reached 3×108W/cm2 in the case of temperature of alkali cell is around 150℃ and pressure of helium buffer gas is about 9.33×104Pa with no heat effects. Moreover, the variation of ionization degree of cesium vapor is minor relative to the obvious increase of the number density of cesium vapor when the temperature of alkali cell rises from 122℃ to 163℃. These results indicates important signification for cesium DPAL scaling by increasing the power density of pump laser and the temperature of alkali cell.