Xiaomin Ren

Long wavelength resonant cavity photodetector based on InP/air-gap Bragg reflectors

We demonstrate a long wavelength resonant cavity photodetector with InP/air-gap Bragg reflectors, which is fabricated by using selective wet etching. The peak quantum efficiency is 59% at 1510 nm. A 3-dB bandwidth of 8 GHz has been achieved with the active area of 50/spl times/50 /spl mu/m/sup 2/. Compared with the detector of same absorption depth, a three-fold increase of absorption efficiency is obtained at resonant wavelength.

High-Efficiency InGaAs/InP Photodetector Incorporating SOI-Based Concentric Circular Subwavelength Gratings

A grating-integrated silicon-on-insulator (SOI)-based photodetector for use in the long wavelength was fabricated and characterized. An InGaAs/InP p-i-n structure was heterogeneously integrated on an SOI-based concentric circular subwavelength grating (CC-SWG) by means of a low-temperature bonding process with benzocyclobutene as the bonding agent. The light absorption of the device is enhanced due to high-index-contrast CC-SWGs as a broadband reflector. These features lead to an increase in quantum efficiency, for the whole S, C, and L communication bands, while maintaining a high speed. The measured quantum efficiency was increased by 39.5% with CC-SWGs in comparison with the device without gratings. A quantum efficiency of 53% at a wavelength of 1.55 and a 3-dB bandwidth of 25 GHz at a reverse bias of 3 V were simultaneously obtained in the device.

Monolithically Integrated Photodetector Array With a Multistep Cavity for Multiwavelength Receiving Applications

A monolithically integrated photodetector array used for multiwavelength receiving was realized by growth of an InP-In0.53Ga0.47As-InP p-i-n structure on a GaAs/AlGaAs Fabry-Perot filter. The filter with a multistep cavity was fabricated by wet etching and regrowth. Each photodetector in the array detects a different wavelength, so the array functions as a multiwavelength receiver. The high-quality GaAs/InP heteroepitaxy was realized by employing a thin low temperature buffer layer. The photodetector array detects four wavelength channels, whose interval is about 10 nm , around 1550 nm. A full-width half-maximum less than 0.5 nm , a peak quantum efficiency over 15%, and a 3-dB bandwidth of 9 GHz were simultaneously obtained in the photo-detector array.

Monothically Integrated Long-Wavelength Tunable Photodetector

This paper demonstrated a tunable long-wavelength photodetector by using the heteroepitaxy growth of InP-In0.53Ga0.47As-InP p-i-n structure on a GaAs-based GaAs/AlAs Fabry-Perot filter structure. High-quality heteroepitaxy was realized by employing a thin low-temperature buffer layer. A wavelength tuning range of 10.0 nm, an external quantum efficiency of about 23%, a spectral linewidth of 0.8 nm, and a 3-dB bandwidth of 6.2 GHz were simultaneously obtained in the device.

Long Wavelength Multiple Resonant Cavities RCE Photodetectors on GaAs Substrates

A 1550-nm high-speed, high efficiency, and narrow-linewidth resonant cavity enhanced photodetector with three resonant cavities is demonstrated. The photodetector, operating at a long wavelength, is monolithically integrated by using a heteroepitaxy growth of an InP-based p-i-n structure on the GaAs-based multiple resonant cavities. High-quality heteroepitaxy was realized by employing a thin low-temperature buffer layer. A peak quantum efficiency value of 70%, a spectral response linewidth less than 0.75 nm (full-width at half-maximum), and a 3-dB bandwidth of 36 GHz were simultaneously obtained in the device.

Guiding properties of asymmetric hybrid plasmonic waveguides on dielectric substrates

We proposed an asymmetric hybrid plasmonic waveguide which is placed on a substrate for practical applications by introducing an asymmetry into a symmetric hybrid plasmonic waveguide. The guiding properties of the asymmetric hybrid plasmonic waveguide are investigated using finite element method. The results show that, with proper waveguide sizes, the proposed waveguide can eliminate the influence of the substrate on its guiding properties and restore its broken symmetric mode. We obtained the maximum propagation length of 2.49u2009×u2009103xa0μm. It is approximately equal to that of the symmetric hybrid plasmonic waveguide embedded in air cladding with comparable nanoscale confinement.

A Novel Hybrid Integrated Photodetector Based on a Cone Absorption Cavity

A novel hybrid integrated photodetector with flat-top steep-edge spectral response, which consists of a Si-based multi-cavity Fabry-Pérot (F-P) filter and an InP-based cone absorption cavity (with a 0.2 m In0.53Ga0.47As absorption layer), has been designed and fabricated. The operating lightwave is well confined to the cone absorption, and experiences multiple reflections across the absorption layer. Thus, an absorption enhancement effect without resonance can be achieved. Based on multi-cavity F-P structure and a cone cavity, this device can get good flat-top steep-edge spectral response and high quantum efficiency. The photodetector is fabricated by bonding a Si-based multi-cavity F-P filter with an InP-based cone absorption cavity. An integrated device with a peak quantum efficiency of 60% around 1550 nm, the dB band of 0.5 nm, and the 25 dB band of 1.06 nm, is simultaneously obtained.

A Monothically Integrated Dual-Wavelength Tunable Photodetector Based on a Taper GaAs Substrate

The design and fabrication of a monolithically integrated dual-wavelength tunable photodetector are reported. The dual-wavelength character is realized by fabricating a taper substrate. The photodetector, operating at a long wavelength, is monolithically integrated by using a heteroepitaxy growth of InP-In0.53Ga0.47As-InP p-i-n structure on a GaAs-based GaAs/ AlAs Fabry-Perot-filter structure, which can be tuned via the thermal-optic effect. High-quality heteroepitaxy was realized by employing a thin low-temperature buffer layer. The integrated device with a dual-peak distance of 7 nm (1530, 1537 nm), a wavelength-tuning range of 5.0 nm, and a 3-dB bandwidth of 5.9 GHz was demonstrated, agreeing with the theoretical simulation.

Subwavelength Energy Transport Along a Dielectric Nanoparticle Chain in a Metal Slot

Subwavelength energy transportation along a dielectric nanoparticle chain in a metal slot is investigated. It is demonstrated that subwavelength resonance modes with nanoscale confinement could be well achieved in the proposed waveguide, free from the demanding requirement of an ultralarge dielectric constant for a traditional dielectric nanoparticle waveguide (DNPW). In addition, the proposed waveguide exhibits the lowest attenuation factor in visible region and near-infrared region when compared with its counterparts including a traditional DNPW, a metal nanoparticle waveguide without/in metal slot, and a metal slot. The proposed mechanism of energy transport in the nanoscale has potential application in broadband and long-distance subwavelength transmission lines for photonic integration circuits (PICs).

Key technologies for novel wavelength-selective photodetectors

One-Mirror-Inclined Three-Mirror-Cavity (OMITMiC) photodetector, which combines a Fabry-Perot filtering-cavity with a taper absorption-cavity, features high-speed, high quantum efficiency and ultra-narrow spectral linewidth simultaneously and allows wide range tuning when proper tuning mechanism is introduced. First fabrication and demonstration of this kind of device on GaAs substrate had been done in our laboratory. A quantum efficiency of 75% and a spectral linewidth of 0.8 nm (FWHM) were achieved with an absorption layer as thin as 0.119 /spl mu/m. Relevant micromechanical tunable Fabry-Perot filter with a tuning range about 30 nm had been achieved. Research works on the key technologies to transfer our success to InP based long wavelength device are also presented.