飞秒激光在KCl晶体中诱导色心

Femtosecond Laser-Induced Color Centers in KCl Crystal

分别利用1kHz和200kHz两种重复频率的近红外飞秒激光,经过低数值孔径的物镜聚焦,空间选择性地辐照KCl晶体,在KCl晶体内部诱导出了一系列色心缺陷。通过飞秒激光辐照前后KCl晶体的吸收光谱分析,明确了飞秒激光照射后KCl晶体内部5种色心的归属,发现色心的浓度随着飞秒激光功率的升高而增长。对吸收光谱的分析表明,两种重复频率的飞秒激光所诱导的色心吸收带相应的峰值略有偏移。认为这是由高重复频率的飞秒激光的热累积效应引起的。理论分析表明,KCl晶体内部的点缺陷和高功率密度飞秒激光与KCl晶体相互作用所诱导的多光子吸收是色心形成的主要原因。

The space-selective formation of a series of color center defects in bulk transparent potassium chloride（KCl） crystal induced by 1 kHz and 200 kHz,800 nm near-IR femtosecond laser which is focused via low-aperture objectives are reported,respectively.Absorption spectra before and after femtosecond laser irradiation indicate that five kinds of color centers are induced.With the increment of laser power,the concentration of color centers also increases.From the absorption spectra,it is found that the corresponding peak values of absorption bands of color centers induced by two different repetition rates femtosecond laser have slight shift.It is speculated that this phenomenon is resulted from the heat accumulation of the high repetition rate femtosecond laser.Theoretical analysis confirms that the point defects in bulk transparent KCl crystal and multiphoton absorption induced by high power density femtosecond laser-KCl crystal interaction are the main reasons of the formation of color centers.