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倾斜波导半导体激光器内基侧模的“之”字形谐振条件

Theoretical study of “zigzag” resonance condition in angled cavity laser diode
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摘要 倾斜波导半导体激光器具有独特的谐振光路,基侧模在倾斜波导内满足“之”字形振荡,可有效抑制广域激光器中的高阶侧模激射和灯丝效应。目前倾斜波导半导体激光器大多采用强折射率导引设计,其“之”字形谐振腔长仅由几何关系确定,在弱折射率导引下谐振条件存在一定偏移。为此,基于静态相位法引入古斯-汉欣位移因子,给出了一种适用于两种折射率导引情况的理论模型。对比分析表明,数值计算的结果与两种折射率引导下的仿真结果吻合较好,能更准确地满足弱折射率引导下倾斜波导内基侧模的“之”字形谐振。理论分析同时表明,m阶侧模存在相应的临界刻蚀深度,在基侧模临界刻蚀深度附近,倾斜波导表现出更强的模式选择能力。 Objective Laser diodes have great demands in material processing and space communication because of their small size and high electro-optical conversion efficiency.However,due to the nonlinear effect,the traditional broad-area lasers are prone to filamentary emission and face the problems of large divergence angle and poor lateral beam quality,which limit their direct application.Angled cavity laser diodes have a unique oscillation optical path in which the fundamental lateral mode satisfies zigzag resonance,then the high-order lateral modes and filamentation effects in the broad-area lasers can be suppressed effectively.Presently,most of the angled cavity laser diodes are designed with a strong index guiding to total internal reflection of the fundamental lateral mode on the sidewalls,the non-radiative recombination loss is enhanced because the etching depth exceeds the active region.However,the resonance condition of the fundamental lateral mode is deviated as the etching depth decreases.Therefore,it is necessary to research angled cavity laser diodes with weak index guiding structure.For this purpose,the zigzag resonance conditions of angled cavity laser diodes in different etching depths are studied.Methods Based on the stationary phase method,this paper gives a theoretical model containing the GH shift factor for strong and weak index guiding.The influence of the GH shift in the angled cavity laser diodes on the zigzag resonance condition of the fundamental mode is discussed theoretically(Fig.2),and the new fundamental lateral mode zigzag resonance conditions containing the GH factor are clarified.It is pointed out that the corresponding shallowest critical etching depth Dc,m exists for each order lateral mode,and the mode selection characteristics of the angled cavity under the fundamental lateral mode critical etching depth Dc,0 are analyzed.Results and Discussions The GH shift factor in the angled cavity is studied based on the stationary phase method,and a theoretical model for strong and weak index guiding is given.Comparative analysis shows that the calculation results of the theoretical model are in good agreement with the simulation results under the two types of index guiding and can more accurately describe the resonance of the fundamental lateral mode in the angled cavity under the weak index guiding(Fig.3-Fig.4).The analysis of the theoretical model shows that there exists a corresponding critical etching depth Dc,m for the m-order lateral mode,when the etching depth of the angled cavity is less than Dc,m,the limiting effect of the waveguide on the m-order lateral mode decreases drastically,so the angled cavity exhibits a strong mode selective ability near the fundamental lateral mode critical etching depth Dc,0(Fig.5).Conclusions The theoretical model of the angled cavity for strong and weak index guiding is obtained through the theoretical analysis of the GH shift inside the angled cavity,and the critical etching depths Dc,m of lateral modes are given according to the effective refractive index method and the Snell's law.Combined with the software simulation,it shows that the GH shift is proportional to the ridge width W and inversely proportional to the waveguide tilt angleθ,which has a great influence on the zigzag resonance conditions of the fundamental mode under the weak refractive index.After the GH shift factor is introduced,the theoretical calculation results and simulation results are in good agreement in both strong and weak index guiding,which solves the problem of the zigzag resonance conditions deviation of the fundamental lateral mode under weak index guiding,and helps to improve the coupling efficiency of the fundamental lateral mode.In addition,the etching depth of the angled cavity laser diodes must be larger than or equal to the fundamental lateral mode critical etching depth Dc,0,selected the fundamental lateral mode critical etching depth Dc,0 reduces the non-radiative composite loss of the sidewalls and enhances the selectivity of high-order lateral modes at the same time compared with the strong index guiding.
作者 虞顺超 宫梓傲 邹永刚 徐英添 范杰 YU Shunchao;GONG Ziao;ZOU Yonggang;XU Yingtian;FAN Jie(Chongqing Research Institute,Changchun University of Science and Technology,Chongqing 401120,China)
出处 《红外与激光工程》 EI CSCD 北大核心 2024年第6期81-89,共9页 Infrared and Laser Engineering
基金 重庆市自然科学基金面上项目(CSTB2022NSCQ-MSX0401,CSTB2022NSCQ-MSX0889)。
关键词 半导体激光器 倾斜波导 静态相位法 侧模调控 semiconductor laser angled cavity stationary phase method lateral modes control
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