Guoyun Ru

An optical packet switch based on WDM technologies

Dense wavelength-division multiplexing (DWDM) technology offers tremendous transmission capacity in optical fiber communications. However, switching and routing capacity lags behind the transmission capacity, since most of todays packet switches and routers are implemented using slower electronic components. Optical packet switches are one of the potential candidates to improve switching capacity to be comparable with optical transmission capacity. In this paper, we present an optically transparent asynchronous transfer mode (OPATM) switch that consists of a photonic front-end processor and a WDM switching fabric. A WDM loop memory is deployed as a multiported shared memory in the switching fabric. The photonic front-end processor performs the cell delineation, VPI/VCI overwriting, and cell synchronization functions in the optical domain under the control of electronic signals. The WDM switching fabric stores and forwards cells from each input port to one or more specific output ports determined by the electronic route controller. We have demonstrated with experiments the functions and capabilities of the front-end processor and the switching fabric at the header-processing rate of 2.5 Gb/s. Other than ATM, the switching architecture can be easily modified to apply to other types of fixed-length payload formats with different bit rates. Using this kind of photonic switch to route information, an optical network has the advantages of bit rate, wavelength, and signal-format transparencies. Within the transparency distance, the network is capable of handling a widely heterogeneous mix of traffic, including even analog signals.

A model for optimization of the performance of frequency-Modulated DFB semiconductor laser

We have developed a model of frequency modulated distributed feedback laser with intracavity phase modulator and have shown that it can operate in two different regimes, only one of which has good frequency-modulated (FM) response. We have identified the combination of the laser parameters that forces laser to operate in high FM efficiency regime. The results of our initial experiments support these conclusions.

High power slab-coupled waveguide laser

Slab-coupled waveguide laser was theoretically analyzed by E. A. J. Marcatili [1] in the 1970s, based on which, we recently demonstrated a high power slab-coupled waveguide laser with buried hetero-structure. The laser lases around 1525.5 nm, with 3.4 μm*4.4 μm (FWHM) spatial mode shape. With improved current blocking mechanism, the output power reaches 326mW per facet, the coupling efficiency to the single mode fiber (SMF) is 80%, the horizontal and vertical far field angles are 10°, 18° respectively. Electron blocking layer will be implemented to improve internal quantum efficiency. Epi-side down bonding will be used to improve heat dissipation and output power.

In1-xGaxAsyP1-y nipi structure and its application to semiconductor optical amplifiers

In1-xGaxAsyP1-y nipi Structure has been grown by MOCVD and been characterized by photoluminescence. The two PL profiles from the direct and the indirect recombination channels were clearly observed. The excitation intensity and temperature dependence of the PL profiles are studied. A calculated carrier lifetime, as long as 71μs is possible to be realized. With such a long carrier lifetime, we can push the XT noise out of the signal band down to frequencies < f=f=1/(2πτ)=2.2kHz. Equivalently, the XT is eliminated.

Measurement of the lifetimes of photo-excited carriers in type-I and type-II quantum well materials

Room temperature carrier lifetimes of both type-I and type-II InP-based multiple quantum wells near optical transparency were measured using the pump-probe technique. Longer carrier lifetime in the type-II sample was observed.

Very low threshold, carrier-confined diode lasers by a single selective area growth

Very low threshold, carrier-confined semiconductor lasers made of a single selective area growth by metal organic chemical vapor deposition without using any regrowth are reported. Room-temperature continuous wave threshold of 2.7mA emitting around 1.54μm was achieved from as-cleaved facet. The fabricated lasers have good uniformity across the wafer and initial aging test shows that the laser is reliable.

Study of P-type carbon doping on In0.53Ga0.47As, In0.52Al0.2Ga0.28As, and In0.52Al0.48As

The incorporation of carbon into In0.53Ga0.47As, In0.52Al0.48As and In0.52Al0.2Ga0.28As lattice matched to InP was investigated using carbon tetrabromide (CBr4) as the carbon source in Metalorganic Chemical Vapor Depositions growth. The parameters and growth conditions are optimized to get high p-type doping for photonic device applications. This is among the first few studies on C-doping in InAlAs and InAlGaAs, and the results show that the presence of Al also efficiently helps to obtain high p-type carbon doping.

Study of N-type Si delta doping on InP and In0.53Ga0.47As

The method of using Si delta doping to obtain high n-type doping for InP and In0.53Ga0.47As lattice matched to InP was studied. With the multiple delta doping, we can obtain ~1019 cm-3 N-type doping for both the InP and InGaAs materials by using TMI, PH3, Si2H6 and TEGa precursors in Metalorganic Chemical Vapor Depositions growths. Current results show that the delta doping technique is critical for getting extremely high N-type doping in InP and InGaAs.

Gamma-X band mixing in GaAs/AlAs superlattice

GaAs/AlAs superlattices (SLs) were grown by MOCVD. The temperature dependence of photoluminescence was measured. The type II-transition dominated PL spectrum was achieved by controlling the layers thickness of GaAs and AlAs at low temperature. Such SLs with long carrier lifetime is very attractive for low crosstalk semiconductor optical amplifier applications.

Study of wavelength shift in quantum well structure by MOCVD selective area growth

Bulk InGaAs and InGaAsP and quantum well structure were grown on different oxide pattern. The material composition varies with the width of oxide pattern. The PL peak wavelength of the grown SAG quantum well is determined by the variation of both the material composition and the well width. We have experimentally identified the ratio of the contribution from the two sources, which agree well with the theoretical calculation from the measured thickness changes.