Yufeng Shang

Theoretical analysis and design guideline for focusing subwavelength gratings

We propose a planar dielectric reflector with focusing ability using concentric circular subwavelength gratings (CC-SWGs). The two-dimensional focusing ability of CC-SWGs is investigated by the rigorous coupled-wave analysis (RCWA) and finite element method (FEM). By designing the concentric circular pattern of the grating surface, a focusing reflector with high numerical aperture (NA) and high reflectivity is constructed. A CC-SWG reflector with a diameter of 32.6μm and a focal length of 6μm is investigated, which exhibits high focusing ability at normal incidence with a radially polarized plane wave. At the reflection focal plane, the full-width-half-maximum (FWHM) of the electric field intensity is 0.89μm. Numerical aperture value as high as 0.93 is achieved for the reflector with very high reflectivity of 92%.

Mushroom-Mesa Photodetectors Using Subwavelength Gratings as Focusing Reflectors

A novel grating-integrated mushroom-mesa photodetector is demonstrated, which uses an undercut mushroom-mesa structure and a grating focusing reflector to increase bandwidth and efficiency simultaneously. The mushroom-mesa p-i-n structure is heterogeneously integrated on a non-periodic concentric circular subwavelength grating by a wafer bonding process. High speed can be obtained by using a mushroom-mesa structure for reducing its RC time constant. Meanwhile, high quantum efficiency can be obtained by using a grating reflector for its focusing ability. The external quantum efficiency measured on a device of 30 μm in diameter is 45.28% at a wavelength of 1.55 μm, which is enhanced by 21.4% in contrast to the device without reflector. And a 3-dB bandwidth of 30 GHz at a reverse bias of 3 V is simultaneously measured for our photodetector.

Design and analysis of resonant cavity enhanced photodetector by using InP-based concentric circular subwavelength grating

This paper presents the design and analysis of a novel resonant cavity enhanced photodetector which is realized by utilizing concentric circular subwavelength gratings (CC-SWGs) as reflective mirrors. The CC-SWG proposed here can achieve a reflectivity of higher than 99% within a broad wavelength range from 1.37 to 1.63 µm. The calculated peak quantum efficiency of the designed photodetector can achieve 90% at 1.55 µm.

Study on resonant cavity enhanced photodetector using subwavelength grating

Sub-wavelength gratings are used in the new photodetector in this paper. The detectivity is enhanced by excitation of surface plasma waves (SPW) using a Metal Aperture Arrays grating. Sub-wavelength dielectric grating is used to replace the top Bottom Distributed Bragg Reflectors(DBR).

Study on high speed photodetectors with plasmonics flilter

A new photodetector was designed with Metal Aperture Arrays filter in this paper. The shape and dimensions of the holes in an arrays do influence its transmission spectrum compare to the conventional photodetector. Hole array and annular aperture arrays were discussed.

Design and fabrication of multichannel tunable photodetector array

A long wavelength multichannel tunable photodetector array was fabricated based on multistep Fabry-Pérot filter by using the heteroepitaxy growth of InP-In0.53Ga0.47As-InP PIN structure on a GaAs based GaAs/AlAs Fabry-Pérot filter structure. High quality heteroepitaxy was realized by employing a thin low temperature buffer layer. The array can detect multiple channels, and the tuning range of each detector is about 10nm. A spectral linewidth of 0.5nm, a quantum efficiency over 25%, and a 3dB bandwidth of 9.2GHz were simultaneously obtained.