Y.S. Oei

A short polarization splitter without metal overlays on InGaAsP-InP

A new and very short polarization splitter on InGaAsP-InP is designed and realized for the first time. The component contains a ridge waveguide directional coupler of 0.4 mm length and an output section of 0.7 mm. It uses the large waveguide birefringence of the first-order TE and TM modes to obtain polarization selective directional coupling. In this way, additional metal layers on the waveguides to create birefringence are avoided and fabrication becomes very simple. Components are realized, which show splitting ratios close to -20 dB. Excess losses are below 1 dB. The polarization splitting is investigated in the wavelength region of 1525-1560 nm and found to be better than -9 dB.

Polarization independent dilated WDM cross-connect on InP

A four wavelength 2/spl times/2 optical wavelength-division-multiplexed cross-connect with dilated switches is reported. The device is monolithically integrated on InP and consist of two eight-channel PHASARs combined with 16 electrooptic Mach-Zehnder interferometer switches. On-chip loss is less than -17 dB and crosstalk is better than -20 dB.

Mode evolution type polarization splitter on InGaAsP/InP

A new type of mode-evolution polarization-splitter based on InGaAsP/lnP has been designed and realized. The component uses the large waveguide birefringence of the first-order TE and TM modes in a ridge waveguide made in a heterostructure, In the input section an asymmetric Y-junction acts as a mode converter in order to inject first-order TE- and TM-modes in a polarization-splitting section, which consists of a Y-junction formed by a bimodal and a monomodal waveguide. In the output section a third Y-junction is connected to the bimodal waveguide to couple the first-order mode to a monomodal output waveguide. Components that are 6-mm long and show polarization splitting at a wavelength of 1.55 mu m have been realized. The best splitting ratios are close to -20 dB, which is in agreement with BPM simulations. Excess losses are below 1 dB.<<ETX>>

Realization of a short integrated optic passive polarization converter

For the first time, passive polarization converters with lengths of less than 1 mm and high polarization conversions are realized on InGaAsP-InP. Angled facets in a periodic coupler are used to obtain efficient conversion. Polarization conversions of more than 70%, respectively more than 90%, are measured for two different realizations of the angled facets. The most promising technology used in the realization results in a propagation loss of less than 1 dB/mm for both polarizations.<<ETX>>

InP/InGaAs Photodetector on SOI Photonic Circuitry

We present an InP-based membrane p-i-n photodetector on a silicon-on-insulator sample containing a Si-wiring photonic circuit that is suitable for use in optical interconnections on Si integrated circuits (ICs). The detector mesa footprint is 50 μm2, which is the smallest reported to date for this kind of device, and the junction capacitance is below 10 fF, which allows for high integration density and low dynamic power consumption. The measured detector responsivity and 3-dB bandwidth are 0.45 A/W and 33 GHz, respectively. The device fabrication is compatible with wafer-scale processing steps, guaranteeing compatibility toward future-generation electronic IC processing.

Current Status and Prospects of Photonic IC Technology

The most complex photonic ICs today have been developed for WDM applications. An overview of the most important integration technologies will be given and recent developments towards broader applications and higher integration densities will be discussed.

Surface morphology of InP/GaInAs in selective area growth by chemical beam epitaxy

In this work some aspects of embedded SAE by chemical beam epitaxy are shown. The anisotropy in growth behaviour between 0° and off-oriented substrates is discussed in terms of the chemical difference between A- and B-type steps. The presence of B steps is beneficial for the InP morphology; simultaneous presence of A steps gives rise to (110) facets, which lead to macro-step formation. From a B step up edge no new B steps are generated during growth, causing a macroscopic ripple pattern starting from this edge. The terrace lengths of these ripples are sensitive to growth conditions that influence surface mobility. Furthermore, the surface diffusion is clearly anisotropic with fast diffusion along [011]. The morphological features can be explained by assuming a (2 × 4) reconstruction during growth.

Sharp vertices in asymmetric Y-junctions by double masking

A novel fabrication procedure is presented for the realization of sharp vertices in Y-junctions on InGaAsP/InP. Overlapping masking layers of silica and resist respectively define the two branches in the junction. A nearly perfect branching point is made by a reactive ion etch with two overlapping mask strips. An asymmetric Y-junction designed to function as a mode splitter is realized with this technique. It shows an improvement of 4-8 dB in mode splitting over a version made with a single masking layer. This agrees with BPM-simulations on the effect of blunting in these Y-junctions.<<ETX>>

Strained GaInAs/InP MQW layers grown by CBE for optical components

We investigated the influence of strain on the optical birefringence in waveguides consisting of Ga x In 1-x As/InP multiquantum well layers. The range of growth parameters to achieve good quality material for the waveguide structures were determined. In a number of layer structures low-loss optical waveguides and PHASAR demultiplexers were fabricated and characterized. The polarization dependence of the demultiplexer can be reduced by using quantum wells strained in tension. Without any precaution, the tensile strain in the well is limited by relaxation at e w ≃ - 0.8%. The strain in the well can be further increased to e w ≃ - 1% by introducing a strain-balancing layer of a compressive strained InAs monolayer in the InP barrier. But polarization independence is not yet achieved. The results indicate, that there is no negative effect of the strain-balancing layer on the optical performance. Also a number of design criteria for polarization independent waveguides are determined.

160Gb/s Serial Line Rates in a Monolithic Optoelectronic Multistage Interconnection Network

We demonstrate very high line rate serial 160Gb/s data transmission through a semiconductor optical amplifier based multistage switching matrix. This represents both the leading edge in monolithic switching circuit complexity and the highest reported line rates through monolithically cascaded switching networks. Bit error rate studies are performed to show only modest levels of signal degradation. Power penalties of order 0.6dB and 1.2dB are observed for two stages and four stages respectively in the monolithic circuits at 160Gb/s per path.