2 x 2 electrooptical switch in silicon-on-insulator waveguide

A 2 x 2 Mach-Zehnder interferometer electrooptical switch integrated in silicon-on-insulator using multimode interference 3-dB couplers as splitter and combiner has been proposed and fabricated. Free carriers plasma dispersion effect was utilized to realize light modulation in silicon. Switching operation was achieved at an injection current of 358mA and which can be much reduced by optimizing the PIN structure and improving fabrication process. Extinction ratio of 7.7dB and crosstalk of 4.8dB has been observed.

Long-wavelength Si-based MQW photodetectors for application in optical fiber communication

Si-based SiGe/Si strained MQW long-wavelength photodetectors (PD) with cycle type (Ring Shape) waveguide (CWG) and resonant-cavity-enhanced (RCE) structure have been investigated for the first time for improving the quantum efficiency and response time. The results show that the responsivities are higher than that of conventional PD with a same Ge content reported previously. In addition, RCE-PD has an obvious narrow band response with FWHM less than 6nm.

Stress analysis of silica-based arrayed waveguide grating by a finite element method

The stress distribution in silica optical waveguides on silicon is calculated by using finite element method (FEM). The waveguides are mainly subjected to compressive stress along the x direction and the z direction, and it is accumulated near the interfaces between the core and cladding layers. The shift of central wavelength of silica arrayed waveguide grating (AWG) on silicon-substrate with the designed wavelength and the polarization dependence are caused by the stress in the silica waveguides.

Investigation on integrated high speed DFB light source and narrow bandwidth RCE photodetector for WDM fiber communication network application

Electroabsorption (EA) modulator integrated with partially gain coupling distributed feedback (DFB) lasers have been fabricated and shown high single mode yield and wavelength stability. The small signal bandwidth is about 7.5 GHz. Strained Si1-chiGechi/Si multiple quantum well (MQW) resonant-cavity enhanced (RCE) photodetectors with SiO2/Si distributed Bragg reflector (DBR) as the mirrors have been fabricated and shown a clear narrow bandwidth response. The external quantum efficiency at 1.3 mum is measured to be about 3.5% under reverse bias of 16 V. A novel GaInNAs/GaAs MQW RCE p-i-n photodetector with high reflectance GaAs/ALAs DBR mirrors has also been demonstrated and shown the selectively detecting function with the FWHM of peak response of 12 nm.

Single ridge waveguide electroabsorption modulated DFB laser for 2.5Gb/s transmission

In this paper we proposed a single ridge waveguide electroabsorption modulated distributed feedback laser (EML) for long-haul high-speed optical fiber communication system. This EML was successfully fabricated by two step metal organic vapor phase epitaxy (MOVPE) including selective area growth (SAG) and helium partially implantation. No obvious changes of the threshold current (< 0.2 mA), extinction ratio (< 0.1 dB), output power (< 0.2 dBm) and isolation resistance were achieved in the preliminary aging test. With 2.5 Gb/s NRZ modulation, no power penalty was observed after the optical signal was transmitted through 280 Km normal single mode fiber.

An investigation on fiber coupled polymer waveguide for electro-optic modulator

A novel crosslinkable polyurethane is used as the core layer of the electro-optic(E-O) modulator. The refractive index and dispersion of this material have been detected by analyzing the F-P oscillation in transmission spectra. Calculated results from the effective index method are given to design the Mach-Zehnder and straight 5-layer ridge wave-guide device (including the metal electrodes). With light at 1.31 mum being fiber coupled into waveguide, the mode properties of these devices have been demonstrated in a micron control system. The guided mode is accordant with the theoretical analysis.

SiGe/Si quantum well resonant-cavity-enhanced photodetector

Resonant-cavity-enhanced photodetectors have been demonstrated to be able to improve the bandwidth-efficiency product. We report a novel SiGe/Si multiple quantum-well resonant-cavity-enhanced photodetector fabricated on a separation-by-implanted-oxygen wafer operating near 1300nm. The buried oxide layer in SIMOX is used as a bottom mirror to form a vertical cavity with silicon dioxide/silicon Bragg reflector deposited on the top surface. The quantum efficiency at the wavelength of 1300nm is measured with 3.5% at a reverse bias of 15V, which is enhanced by 10 folds compared with a conventional photodetector with the same absorption structures.

Circular crating optical scanning holography

The principle of optical scanning holography with circular gratings (CG) as the scanning field is presented. The generation and reconstruction processes of the scanning holography are described. These processes are numerical simulated by computer and the results are achieved. It is shown that the resolution power of the reconstructed image of CG scanning hologram is higher than that of FZP scanning hologram.

Design and fabrication of GaAs OMIST photodetector

We designed and fabricated GaAs OMIST (Optical-controlled Metal-Insulator-Semiconductor Thyristor) device. Using oxidation of A1As layer that is grown by MBE form the Ultra-Thin semi-Insulating layer (UTI) of the GAAS OMIST. The accurate control and formation of high quality semi-insulating layer (AlxOy) are the key processes for fabricating GaAs OMIST. The device exhibits a current-controlled negative resistance region in its I-V characteristics. When illuminated, the major effect of optical excitation is the reduction of the switching voltage. If the GaAs OMIST device is biased at a voltage below its dark switching voltage V-s, sufficient incident light can switch OMIST from high impedance low current"off"state to low impedance high current "on"state. The absorbing material of OMIST is GaAs, so if the wavelength of incident light within 600 similar to 850nm can be detected effectively. It is suitable to be used as photodetector for digital optical data process. The other attractive features of GaAs OMIST device include suitable conducted current, switching voltage and power levels for OEIC, high switch speed and high sensitivity to light or current injection.

Si-based resonant-cavity-enhanced photodetector

Resonant-cavity-enhanced (RCE) photodetectors have been demonstrated to be able to improve the bandwidth-efficiency product. We report one top-illumination and one bottom-illumination SiGe/Si multiple quantum-well (MQW) RCE photodetectors fabricated on a separation-by-implanted-oxygen (SIMOX) wafer operating near 1300nm, The buried oxide layer in SIMOX is used as a mirror to form a vertical cavity with the silicon dioxide/silicon Bragg reflector deposited on the top surface. A peak responsivity with a reverse bias of 5V is measured 10.2mA/W at 1285nm, and a full-width at half maximum of 25nm for the top-illumination RCE photodetector, and 19mA/W at 1305nm, and a full-width at half maximum of 14nm for the bottom-illumination one. The external quantum efficiency of the bottom-illumination RCE photodetector is up to 2.9% at 1305nm with a reverse bias of 25V. The responsivity of the bottom-illumination RCE photodetector is improved by two-fold compared with that of the top-illumination one.

Si-based optoelectronic devices and their attractive applications

The semiconductor photonics and optoelectronics which have a great significance in the development of advanced high technology of information systems will be discussed in this paper. The emphasis will be put on the recent research carried out in our laboratory in enhanced luminescence from low dimensional materials such as SiGe/Si and Er-doped Si-rich SiO2/Si and Er-doped SixNy/Si. A ring shape waveguide structure, used to promote the effective absorption coefficient in PIN photodetector for 1.3 mu m wavelength and a resonant cavity enhanced structure, used to improve the quantum efficiency and response in heterostructure photo-transistor (HPT), are also proposed in this paper.

Flat Surface Plasmon Polariton Bands in Bragg Grating Waveguide for Slow Light

The formations of the surface plasmonpolariton (SPP) bands in metal/air/metal (MAM) sub-wavelength plasmonic grating waveguide (PGW) are proposed. The band gaps originating from the highly localized resonances inside the grooves can be simply estimated from the round trip phase condition. Due to the overlap of the localized SPPs between the neighboring grooves, a Bloch mode forms in the bandgap and can be engineered to build a very flat dispersion for slow light. A chirped PGW with groove depth varying is also demonstrated to trap light, which is validated by finite-difference time-domain (FDTD) simulations with both continuous and pulse excitations.

Hybrid waveguide-plasmon resonances in gold pillar arrays on top of a dielectric waveguide

We propose a hybrid waveguide-plasmon system consisting of gold pillar arrays on top of a dielectric waveguide. The formation of extraordinary transmissions induced by the hybrid waveguide-plasmon resonances is investigated by rigorous coupled-wave analysis. The characteristics of the hybrid resonances can be predicted by introducing the photonic crystal slab theory. Extremely narrow absorption peaks and the electromagnetically induced transparency-like optical property are demonstrated in our hybrid system. (C) 2010 Optical Society of America

Rashba and Dresselhaus spin-orbit coupling in GaN-based heterostructures probed by the circular photogalvanic effect under uniaxial strain

The spin splitting in GaN-based heterostructures has been investigated by means of circular photogalvanic effect experiments under uniaxial strain. The ratios of Rashba and Dresselhaus spin-orbit coupling coefficients (R/D ratios) have been measured in AlxGa1-xN/GaN heterostructures with various Al compositions. It is found that the R/D ratio increases from 4.1 to 19.8 with the Al composition of the AlxGa1-xN barrier varied from 15% to 36%. The Dresselhaus coefficient of bulk GaN is experimentally obtained to be 0.4 eV angstrom(3). The results indicate that the spin splitting in GaN-based heterostructures can be modulated effectively by the polarization-induced electric fields.