光子晶体面发射蓝光激光器的高速调制性能分析

Analysis of High-Speed Modulation Performance of Photonic Crystal Surface-Emitting Blue Lasers

光子晶体面发射激光器基于光子晶体能带带边模式,形成二维微腔谐振,继而实现光增益和激射,其具有高功率、单纵模等优异特性。基于氮化镓基蓝光激光器结构和速率方程调制理论,对异质结构光子晶体面发射激光器进行了动态调制性能分析。通过仿真计算得出,在所研究的激光器结构参数下,阈值电流为1.76 mA,最大3 dB调制带宽为42 GHz,最低数据发送能耗为62.78 pJ·bit^(-1),展示出了该结构激光器的基础性能和高速调制特性,为具有大调制带宽的蓝光激光器的设计提供了参考。

Objective With the development of a new generation of electronic communication technology,data traffic for transmitting information is increasing,thereby driving the development of optical communication technology for higher speed,larger capacity,and lower power consumption.Photonic crystal surface-emitting lasers(PCSELs)are the key devices in this field that have a wide range of potential applications.PCSELs exhibit outstanding features,such as large-area single-mode excitation,arbitrary beam shaping and polarization,and high power.Simultaneously,GaN compounds can be flexible and adjustable to cover any wavelength band from ultraviolet(UV)to green,thereby the laser based on this is complementary to the mature GaAs-and InP-based lasers.Using a photonic crystal heterostructure design can improve the performance of a laser,particularly for achieving large bandwidths.In this study,the expressions for the threshold current,3 dB modulation bandwidth,and output power of PCSELs are derived using the rate equation model,and the fundamental and modulation performances of a GaN-based photonic crystal surface emission laser are analyzed and compared with those of other reported lasers.This investigation lays the foundation for the design of blue-light lasers with large modulation bandwidths.Methods In this study,we first derive expressions for the threshold current,3 dB modulation bandwidth,and output power of PCSELs using the classical rate equation model to lay the foundation for subsequently writing the code in MATLAB.GaN-based PCSELs are selected for modulation analysis,and the core parameters of the laser are derived after strict finite-domain difference(FDTD)-based calculations and verified using the ensemble wave analysis method(RCWA).The MATLAB codes are written using the derived equations and the laser parameter values are substituted into this code to obtain a plot in which the 3 dB modulation bandwidth,output power,and minimum energy consumption are indicated.The relationship between the calculated and simulated values of the threshold current is investigated by changing a single parameter using the control-variable method.Finally,properties such as the modulation bandwidth are compared with those of vertical cavity surface-emitting,wavelength-level active region buried photonic crystal defect,nanobeam,and Si-based distributed feedback lasers to highlight the advantages of GaN-based heterostructure PCSELs.Results and Discussions We first derive the expressions for the threshold current,3 dB modulation bandwidth,and output power of PCSELs.The calculated and simulated values of the threshold current can be obtained by changing the volume of the active region of the laser,and the values show good agreement.When the quality factor(Q)of the laser increases,the calculated and simulated values of the threshold current decrease,and when Q increases further,the calculated and simulated values of the threshold current converge to remain constant(Fig.2).Subsequently,the FDTD calculations of the PCSELs(Fig.3)yield a threshold current of 1.76 mA for the laser and a minimum data transmission energy consumption of 62.78 pJ/bit for direct modulation at 2.4 mA bias current when the 3 dB modulation bandwidth is 6.166 GHz and the output power is 0.795 mW.With an increase in the injection current,the 3 dB modulation bandwidth peaks at 42 GHz(Fig.4).Finally,the threshold currents,maximum modulation bandwidths,minimum energy loss values,and output powers of various types of lasers that have been reported(Table 2)are listed to compare their advantages and disadvantages with those of PCSELs,and it is observed that GaN-based PCSELs can make up the shortcomings of the current laser applications.Conclusions This study focuses on the modulation,threshold,and output power characteristics of PCSELs.We first derive the expressions for the threshold current,3 dB modulation bandwidth,and output power of the PCSELs based on the rate equation model theory of the laser.Subsequently,the fundamental performance and modulation bandwidth performance of a GaN-based photonic crystal surface emission laser are analyzed,and the threshold current of 1.76 mA,the maximum 3 dB modulation bandwidth of 42 GHz,and the minimum data transmission energy consumption of 62.78 pJ/bit are obtained by simulation,thus demonstrating the fundamental performance and high-speed modulation characteristics of the proposed GaN-PCSEL with the studied structure parameters.This study provides the basic performance and high-speed modulation characteristics of the laser and the comparisons with other reported lasers.In this study,a methodology for simulating and analyzing the fundamental and dynamic modulation characteristics of semiconductor lasers is developed,which provides a theoretical basis and guidance for the design of PCSELs with excellent high-speed modulation characteristics.