SESAM实现脉冲式Nd∶YAG激光器的被动锁模特性研究

为了研究半导体可饱和吸收镜的被动锁模特性,采用中科院半导体所提供的半导体可饱和吸收镜,实现了脉冲式Nd:YAG激光器1.06μm激光的被动锁模,获得了稳定的皮秒激光脉冲序列输出.经自相关实验装置测量,其锁模激光脉冲宽度大约为48.2ps,脉冲序列的能量为24mJ,实验中采用直腔结构的谐振腔,该腔结构简单、易于调整.理论上分析了1.06μm半导体可饱和吸收镜结构及被动锁模基本原理,计算并模拟了半导体可饱和吸收镜中布喇格反射层不同周期时对应的反射谱图以及不同周期时中心频率处布喇格反射层的反射率曲线.结果表明,随着布喇格反射层周期数的增加,其中心波长处的反射率也随着增加.当周期数大于13时,其中心波长反射率超过99%.半导体可饱和吸收镜是实现Nd:YAG激光器的被动锁模的理想锁模器件.

Study on passive mode-lock of pulsed Nd:YAG laser with SESAM

For studying the passively mode-locked character of semiconductor saturable absorber mirror(SESAM),a semiconductor saturable absorber mirror,made by Institude of Semiconductors,Chinese Academy of Sciences,was used to obtain a passivel mode-locked Nd∶YAG laser with a simple straight cavity. Stable ps mode-locked pulse train was realized. The modelocked pulse duration is about 48.2ps measured by autocorrelation. The energy of the train is 24mJ. In addition,the constructure of 1.06μm semiconductor saturable absorber mirror and the theory of passively mode-lock was analyzed. Semiconductor saturable absorber mirror is mainly made up of distributed Bragg reflection(DBR)and saturable absorber. The DBR is made up of different higher and lower refractive index materials. Then the reflection spectrum of different pairs of DBR in semiconductor saturable absorber mirror was simulated,so was the distribution of electric field in DBR. From the results,it can be seen that as the increase of pairs of DBR,the reflectivity of central wavelength also increased;when the pairs is above 13,the reflectivity of central wavelength exceeded 99%. In conclution,semiconductor saturable absorber mirror can replace the traditional passively modelocked component(such as Cr4+∶YAG or organic dye)to be the most perfect component for the mode-lock of solid laser.