Study On Local Optical Field Enhancement Of GaAs-based Quantum Well Infrared Photodetectors

As the third-generation infrared detector,quantum well infrared photodetector(QWIP)has become the focus of research in the field of infrared detectors due to its good material uniformity,adjustable detection wavelength,and mature processing technology.However,due to the working mechanism of the quantum well inter-subband transition,it cannot absorb vertically incident light and has low quantum efficiency,which is an urgent problem to be solved in the practical engineering application of QWIP.In addition,based on the requirements of intelligence and the increase of detection scenario complexity,the polarization detection,multi-band detection and high integration of QWIP have become the current research hotspots.In this paper,metamaterials and plasmon microcavity are used to make QWIP absorb normal incident infrared radiation,enhance the local optical field in the quantum well active region,improve the inter-subband absorption of the quantum well,and realize circular polarization identification detection,dual band detection and local optical field enhancement of multi-period QWIP.The main contents of this article are as follows:1.A chiral metamaterial microcavity structure for circular polarization detection is designed.When left circularly polarized(LCP)light is incident,the left chiral metamaterial excites the surface plasmon polariton(SPP)effect,which enhances the local optical field(E_z)in the quantum well active region,and improve the inter-subband absorption of quantum well.Meanwhile,the left chiral metamaterial will reflect most of the right circularly polarized(RCP)light and have lower absorption for RCP light,the circular polarization extinction ratio(CPER)can reach 9.03.The right chiral metamaterial also has a similar enhanced absorption effect for RCP light.This chiral metamaterial microcavity structure can not only improve the quantum efficiency of QWIP,but also realize the identification detection of circularly polarized light,which has a broad application prospect.2.A long-wave and very-long-wave stacked dual-band QWIP based on dual microcavities is designed.Two quantum well materials with different working bands are sandwiched in the microcavity and stacked up and down to form a double microcavity structure.The incident light with corresponding wavelength can excite the microcavity resonance and enhance the local optical field in the active region of the two quantum wells.The two microcavities are independent of each other.Optimizing the structural parameters of a single microcavity will not affect the resonance of the other microcavity,and can be adapted to QWIP with different detection wavelengths.Generally,the enhancement effect of the bottom active region of stacked dual band QWIP is low,but the double microcavity structure can ensure that the upper and lower quantum well active regions have strong enhancement effect,which provides a new idea for the design of optical coupling structure of QWIP dual band detection.3.Aiming at the multi-period long-wave QWIP which cannot effectively use the plasmon microcavity to enhance the local optical field,a gold corrugated backplane grating structure is designed to enable the inter-subband absorption of 16-period QWIP up to 68.4%in the long-wave infrared atmospheric window of 13?m.By analyzing the local optical field distribution of the quantum well active region,and optimizing the thickness of the grating and electrode layer.When the thickness of the entire dielectric layer remains unchanged and the QWIP period is further increased,the inter-subband absorption of the 20-period QWIP can be increased to 76%,a 22-fold enhancement over the standard 45°device.At the same time,by adjusting the length of the gold corrugated backplane grating,it is possible to achieve both the detection of arbitrary polarization direction and the independent identification of specific polarization direction.