Design And Optimization Of Resonant Cavity Structure Of Mushroom-type RCE Photodetector

Driven by the development of a new generation of high-speed optical communication systems,optoelectronic devices are developing more and more rapidly.In vertical PIN photodetectors,there is an inherent mutual constraint between bandwidth and quantum efficiency.Therefore,photodetectors with various new structures have been developed.Resonant cavity-enhanced(RCE)photodetector is one of them.In recent years,optoelectronic devices with integrated sub-wavelength gratings(SWG)have developed very rapidly due to their excellent light field control characteristics.Among them,photodetectors integrated with sub-wavelength gratings have also received extensive attention.In this paper,the deflection phase control of the non-periodic subwavelength grating is used as the core.Firstly,the theoretical analysis method of non-periodic subwavelength grating is introduced,and a high reflectivity grating deflection mirror with a deflection angle of 1 degree is designed.Secondly,replacing the top mirror of the traditional Fabry-Perot cavity(F-P cavity)with the mirror,a novel grating Fabry-Perot cavity is proposed.The advantage of the grating cavity is that it can controll the width of the oscillating light field.Finally,the application of the novel grating Fabry-Perot cavity is proposed,which is a mushroom-type RCE photodetector based on the grating cavity.The device combines the advantages of a mushroom-type structure with an RCE photodetector while achieving a narrow linewidth of 1 nm,a quantum efficiency of 95%,and a 3 dB bandwidth of 45 GHz.The main research results and innovations of this paper are as follows:1.Learned and mastered scientific methods for studying non-periodic subwavelength gratings,such as rigorous coupled wave analysis and finite element methods.According to the phase deflection principle of the non-periodic sub-wavelength grating,the design of the one-dimensional high-reflectance grating mirror with a deflection angle of 1 degree is completed.The reflectivity of the grating mirror is higher than 90%.2.A novel grating resonator is proposed by replacing the traditional Distributed Bragg reflector(DBR)with a designed high reflectivity grating deflection mirror.The resonator can control the width of the light field.The theoretical analysis and proof of the grating cavity are carried out using the equivalent optical path principle of ray optics.Not only the resonance conditions and cavity length of the grating resonator are derived in detail.It is also proved that the oscillating light field width is related to the cavity length and the deflection angle of the grating mirror.Finally,the grating cavity is simulated and analyzed.3.A mushroom-type RCE photodetector based on grating resonator is designed and proposed.The device combines the advantages of the mushroom structure and the RCE photodetector,and we optimizes the layer structure of the detector.The simulation analysis shows that the device has a narrow linewidth of 1 nm,a peak quantum efficiency of 95%,and a 3 dB bandwidth of 45 GHz.