Highly efficient metallic optical incouplers for quantum well infrared photodetectors

Long Liu,Wei Du,Peng Zhan,Zhong Huang,Zhenlin Wang,Yu Chen

doi:10.1038/srep30414

Abstract

Herein, we propose a highly efficient metallic optical incoupler for a quantum well infrared photodetector (QWIP) operating in the spectrum range of 14~16 μm, which consists of an array of metal micropatches and a periodically corrugated metallic back plate sandwiching a semiconductor active layer. By exploiting the excitations of microcavity modes and hybrid spoof surface plasmons (SSPs) modes, this optical incoupler can convert infrared radiation efficiently into the quantum wells (QWs) layer of semiconductor region with large electrical field component (Ez) normal to the plane of QWs. Our further numerical simulations for optimization indicate that by tuning microcavity mode to overlap with hybrid SSPs mode in spectrum, a coupled mode is formed, which leads to 33-fold enhanced light absorption for QWs centered at wavelength of 14.5 μm compared with isotropic absorption of QWs without any metallic microstructures, as well as a large value of coupling efficiency (η) of |Ez|2 ~ 6. This coupled mode shows a slight dispersion over ~40° and weak polarization dependence, which is quite beneficial to the high performance infrared photodetectors.

Highlights

We propose a highly efficient metallic optical incoupler for a quantum well infrared photodetector (QWIP) operating in the spectrum range of 14~16 μm, which consists of an array of metal micropatches and a periodically corrugated metallic back plate sandwiching a semiconductor active layer
Quantum well infrared photodetectors (QWIPs), as an alternative choice, have developed rapidly due to their low cost, excellent reproducibility as well as high uniformity compared with the traditional mercury cadmium telluride (MCT) infrared photodetectors[6,7]
By introducing the coupling of localized surface plasmons (LSPs) and surface plasmon polaritons (SPPs), Chen et al proposed a design of quasi-1D metallic grating to enhance the optical coupling in AlGaN/GaN QWIPs around the resonance wavelength of 4.65 μm 22

Summary

Introduction

We propose a highly efficient metallic optical incoupler for a quantum well infrared photodetector (QWIP) operating in the spectrum range of 14~16 μm, which consists of an array of metal micropatches and a periodically corrugated metallic back plate sandwiching a semiconductor active layer. Regarding the applications such as infrared imaging that requires small-pixel and focal plane arrays (FPAs), it is necessary to couple infrared radiation uniformly to two-dimensional (2D) arrays of such infrared photodetection devices To solve these issues, one-dimensional (1D) and 2D grating microstructures such as the photonic crystal slab[12] have been proposed to serve as a grating coupler integrated on the top-surface of QWIPs to couple normally incident light into the in-plane direction, and to control the optical state in the QWs layer, which is beneficial to the inter-subband transition. It has been demonstrated that a perforated metal film coated with a thin high-index dielectric layer supports strongly confined hybrid SSPs due to the coupling of SSPs with the conventional guided-wave modes in the thin dielectric layer, and such a hybrid SSPs mode leads to a perfect absorption even for a thin weakly absorbing semiconductor film[28]

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