Ultrathin high efficiency photodetectors based on subwavelength grating and near-field enhanced absorption

Abstract

Optical absorbers, comprising a thin semiconductor layer placed between two transparent ones in close proximity to a subwavelength grating, are considered. With no back mirror, these structures only mimic the resonant cavity enhanced photodetector, being an order of magnitude thinner. It is argued that the grating can assist the light confinement by near field microcavity resonance rather than by far field mirroring. Tolerant designs to attain nearly 100% optical absorption at a predefined wavelength are demonstrated, and the near-field enhancement of the absorption is confirmed. The results obtained indicate that the proposed near field enhanced photodetectors meet the combined challenges of significantly increasing the efficiency and reducing the complexity and size of the entire device as compared to the resonant cavity enhanced photodetectors, which may be useful for integrated multi-detector arrays.

Introductory Chapter: Photodetectors

“…By embedding an ultrathin semiconductor absorption layer into a Fabry-Pérot resonant cavity, resonant cavity enhanced photodetectors can be realised, to boost the quantum efficiency or bandwidth-efficiency product, and provide superior wavelength selectivity and high speed photoresponse for wavelength division multiplexing (WDM) systems. Subwavelength microcell gratings affixed in close proximity to the optical absorber can enable near-field enhancement of optical absorption through strong electromagnetic field confinement [1].…”

Beam Tailoring Devices Using Transmission-Type Subwavelength Grating

“…Moreover, most previous studies on metamaterials have lacked rigorous theoretical calculations and derivations. Subwavelength gratings (SWGs), in part, can be considered as subwavelength-scale photonic crystals and are emerging as an enabling technology for implementing compact, high-performance photonic integrated devices and circuits [6,7], including reflectors [8], directional couplers [9], filters [10], splitters [11], sensors [12], and modulators [13], among others. Moreover, certain subwavelength gratings with novel surface structures can greatly improve device performance [14].…”

Dual-guiding-layer resonance structure with an embedded metasurface for quasi-critical coupling without a perfect mirror

“…As an alternative optical cavity, a guided resonance structure is used to meet the critical coupling condition, formed by a metasurface or 1D or 2D photonic crystal layer backed with a metallic or DBR [13][14][15][16][17][18][19] . The metasurface has a fixed thickness, but by manipulating the other parameters, such as grating period or the ratio of high to low refractive index regions within a unit cell, the decay rates of the resonance mode from the resonance structure can be tuned 13,20 .…”