Xinye Fan

A flat-top steep-edge waveguide photodetector composed of cascaded silicon microring resonators

In this paper, we proposed a novel photodetector composed of cascaded microring resonators on silicon-on-insulator. In order to enhance the tolerance of signal wavelength drifting in optical communication, the photodetector was designed with a flat-top steep-edge response. In the photodetector, we used polarization insensitive cascaded silicon microring resonators as optical filter cavity, and used a silicon racetrack resonator bonded in p-i-n chip as optical detecting cavity. We used finite element (FE) mode solver, finite different time domain (FDTD), and transfer matrix method (TMM) to simulate the behavior of the polarization insensitive optical filter. With optimized parameters, the photodetector showed high quantum efficiency, narrow line width, and flat-top steep-edge.

Analysis and design of a tunable filtering waveguide based on silicon-on-insulator

One of the current research trends in silicon photonics is to integrate many kinds of optical functionalities on a single chip. In this paper, based on Silicon-on-Insulator (SOI) we design a tunable filtering waveguide consisted of a Fabry-Pérot cavity and a straight waveguide. The Fabry-Pérot cavity is used for wavelength selectivity and the waveguide is used for light guide. The transmission characteristic of the device has been numerically simulated. The result shows that the Full-Width Half-Maximum (FWHM) is inversely proportional to pairs of the DBR. The tunable filtering waveguide can be integrated with waveguide photodetector, and hopefully to be used in WDM system.

Hybrid integrated photodetector with flat-top steep-edge spectral response

Hybrid integrated photodetectors with flat-top steep-edge spectral responses that consist of an Si-based multicavity Fabry-Perot (F-P) filter and an InP-based p-i-n absorption structure (with a 0.2 μm In(0.53)Ga(0.47)As absorption layer), have been designed and fabricated. The performance of the hybrid integrated photodetectors is theoretically investigated by including key factors such as the thickness of each cavity, the pairs of each reflecting mirror, and the thickness of the benzocyclobutene bonding layer. The device is fabricated by bonding an Si-based multicavity F-P filter with an InP-based p-i-n absorption structure. A hybrid integrated photodetector with a peak quantum efficiency of 55% around 1549.2 nm, the -0.5 dB band of 0.43 nm, the 25 dB band of 1.06 nm, and 3 dB bandwidth more than 16 GHz, is simultaneously obtained. Based on multicavity F-P structure, this device has good flat-top steep-edge spectral response.

Design and analysis of InGaAs PIN photodetectors integrated on silicon-on-insulator racetrack resonators

The integration of optical functionalities on a chip has been a long standing goal in the optical community. The ability to integrate compound semiconductors onto foreign substrates can lead to superior or novel functionalities. In this paper we integrate InGaAs /InP photodetectors onto Silicon-on-Insulator (SOI) racetrack resonators. The racetrack resonators can be fabricated by utilizing electron beam lithography and inductively-coupled-plasma reactive ion etching (ICP-RIE) technique. The racetrack structure is used for wavelength selectivity and the straight waveguide sections are used to achieve a large value of the coupling coefficient with a bus waveguide. The transmission characteristic of the racetrack resonator with a multimode interference (MMI) coupler has been numerically simulated. The result shows that the free spectral range (FSR) is inversely proportional to the length of the racetrack resonator. The FSR decreases as the increase of the length of straight waveguide sections or the radius of rings. The generalized multimode transmission matrix of the MMI has been evaluated with beam-propagation method. It has been found that the resonance wavelength can be reasonably predicted. Finally, the equation of quantum efficiency of the device is derived. The calculated peak quantum efficiency of the designed photodetector can achieve about 90% at 1.5499 μ m.

A monothically integrated dual-wavelength photodetector with a step-shaped Fabry-Pérot filter

A novel long wavelength photodetector with dual-wavelength response has been designed and fabricated, which can be realized by a step-shaped Fabry-Perot (F-P) filter structure. By using low pressure metal organic chemical vapor deposition (LP-MOCVD), the step-shaped GaAs/AlGaAs distributed Bragg reflectors (DBR) and the InP PIN photodetector are grown on a GaAs substrate, and by employing a thin low temperature buffer layer, the high quality GaAs/InP heteroepitaxy is realized. The structure of the photodetector is optimized by theoretical simulation. This device has a dual-peak distance of 19nm (1558, 1577 nm). The peak quantum efficiency of 8.5% around 1558 nm and 8.6% around 1577 nm, the 3dB bandwidth of 16 GHz are simultaneously obtained.

Design of novel tunable resonant cavity enhanced photodetector (RCE-PD)

A novel tunable resonant cavity enhanced photodetector (RCE-PD) is achieved by using an air gap. The optical properties of the photodetector are designed by using the transfer matrix method (TMM). The quantum efficiency (QE) of the tunable RCE-PD is calculated and the optimizing structure is obtained. It is revealed that the peak QE increases to the highest value ( 92%) when the thickness of active layer is 106nm. When the air layer thickness changed 20nm under a low bias voltage, the peak wavelength blue shifts from 1550nm to 1547.9nm and the QE of the device keeps almost invariant at the same time.