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通过构建外腔半导体激光器的等效腔模型,并在修正的肖洛-汤斯线宽公式中引入外腔压窄因子,系统模拟了光纤光栅外腔半导体激光器的电流阈值特性和线宽特性。以等效腔模型为基础,综合考虑外腔压窄因子,利用修正后的肖恩-汤斯公式,使用Matlab对外腔激光器的阈值和线宽特性进行了系统的模拟。模拟结果表明:通过增加外腔反射率,可有效增加光子寿命并降低阈值载流子浓度,进而获得较低的阈值电流,对于0.81的外腔等效反射率,阈值电流低至3.83mA;通过增加外腔反射率、耦合效率和外腔长度,可显著压窄线宽至千赫兹量级;此外,合理限制增益芯片尺寸也会压窄线宽。激光器工作电流为60mA时,当外腔光栅反射率由0.1提高至0.9可使阈值电流由9.04mA降低至4.01mA,线宽由95.27kHz降低至1.34kHz;当外腔长度由2cm增加至6cm时,激光器线宽由3.20kHz降低至0.36kHz。
By constructing an equivalent cavity model of an external cavity semiconductor laser and introducing a cavity narrowing factor into the modified line width formula of the Shorotowath system, the current threshold characteristics and linewidth characteristics of the fiber grating external cavity semiconductor laser are simulated. Based on the equivalent cavity model, the external cavity narrowness factor is considered, and the threshold and linewidth characteristics of the external cavity laser are systematically simulated by using the modified Sean-Thoms formula. The simulation results show that by increasing the reflectivity of the external cavity, the photon lifetime can be effectively increased and the threshold carrier concentration can be lowered, thereby obtaining a lower threshold current with the threshold current as low as 3.83mA for the external cavity equivalent reflectivity of 0.81; Increasing external reflectivity, coupling efficiency, and external cavity length can significantly narrow the linewidth to the order of kilohertz; in addition, limiting the gain chip size reasonably will also narrow the line width. When the operating current of the laser is 60mA, the threshold current decreases from 9.04mA to 4.01mA and the linewidth decreases from 95.27kHz to 1.34kHz when the reflectivity of outer grating increases from 0.1 to 0.9. When the external cavity length increases from 2cm to 6cm The laser linewidth is reduced from 3.20kHz to 0.36kHz.