Thomas Zinke

0.1 dB/cm waveguide losses in single-mode SOI rib waveguides

Waveguide losses as low as 0.1 dB/cm at a wavelength of /spl lambda/=1.3 /spl mu/m have been achieved in SOI rib waveguides fabricated by wet chemical etching. The single-mode waveguides have a large cross section yielding field mismatch losses to a standard single-mode fiber of only 0.17 dB/facet (both polarizations). Polarization independent fiber-chip-fiber insertion losses of 0.9 dB (best 0.5 dB) at a chip length of 60 mm have been measured.

Integrated optics in silicon and SiGe-heterostructures

This paper reviews various techniques and ideas in the field of integrated optics in silicon, mainly focused on silicon in conjunction with germanium. We will discuss different approaches for waveguides, passive and active components in silicon as well as recent developments in the fabrication and performance of such components. For waveguides in silicon, the characteristics such as losses and spot-sizes are given, showing that silicon could be an attractive candidate for integrated optical devices.

Integration of waveguides and photodetectors in SiGe for 1.3 /spl mu/m operation

The integration of single-mode rib waveguides and photodetectors in silicon using MBE-grown SiGe-layers is reported. Short photodetectors exhibit dark currents below 200 nA at 7 V reverse bias. For the fiber-waveguide-detector coupling an overall quantum efficiency of 11% has been achieved at 7 V reverse bias for /spl lambda/=1.3 /spl mu/m. The maximum bandwidth is 2 GHz.<<ETX>>

Room‐temperature electroluminescence from Si/Ge/Si1−xGex quantum‐well diodes grown by molecular‐beam epitaxy

Tunable room‐temperature electroluminescence, photocurrent, and photoluminescence in the near infrared (λ∼1.3 μm) has been observed from Ge/Si/Ge/Si1−xGex quantum‐well (QW) diodes grown by molecular‐beam epitaxy. The QWs are grown on a p+‐doped 〈100〉‐Si substrate and consist of two thin Ge wells separated by a thicker Si middle layer, and the whole structure is embedded by two Si0.85Ge0.15 alloy layers. Our theoretical analysis of the data suggests that the strength of the spectra is linked to states localized at the interface.

Integrated optical waveguide switches in SOI

We report on the first 1/spl times/2 and 2/spl times/2 waveguide switches based on single-moded rib-waveguides in SOI. The switches are based on the thermo-optical effect and require switching powers of 85 mW at a wavelength of/spl lambda/=1.3 /spl mu/m. Optical device losses of 7 dB (cross talk -6 dB) for the 1/spl times/2-switch and 8 dB (cross talk -5 dB) for the 2/spl times/2-switch have been obtained including Fresnel losses of 2.4 dB.

Theoretical and experimental investigation of optical couplers in SOI

Integrated Optics in SOI need a concept for passive optical couplers, which is highly insensitive to fabrication tolerances. For this purpose directional couplers as well as couplers based on Multi-Mode-Interference (MMI) have been investigated, both theoretically and experimentally. BESOI material with a top layer thickness of 11 micrometers is optimally adjusted to single-mode-fibers resulting in a field mismatch loss of 0.17 dB. For fabrication tolerances of 5%, only MMI- couplers showed an insensitive behavior with additional losses of 0.4 dB and a crosstalk (CRT) of -30 dB at a wavelength of 1.3 micrometers . A particular interest was paid to the additional coupling in the access region of the coupler, since there is no possibility to its compensation in this concept. The potential application of couplers in combination with phase shifters was studied theoretically as well. Realized MMI-based cross-couplers showed additional losses of 1 dB and a CRT of -17 dB, the best values for SOI-based couplers reported so far.

Integrated optoelectronic waveguide detectors in SiGe for optical communications

The monolithic integration of a SiGe-optical waveguide with a detector based on SiGe- absorbing layers is presented. A maximum internal quantum efficiency of (eta) equals 40% has been measured at (lambda) equals 1.3 micrometers , which corresponds to an external efficiency of (eta) equals 11%. This device is suitable for 2.5 GBit/s data transmission, the performance is limited by the RC time constant due to a capacitance of C equals 1.7 pF.

Concepts for optical waveguide switches in silicon

By time domain measurements on a carrier injection switch using Ge-indiffused waveguides in silicon the plasma dispersion and the thermo-optical effect were separated and quantified. Optimized thermo-optical switches in silicon-on-insulator with low switching powers are also presented.

Absorption and emission characteristics of mesa and ridge waveguide diodes made from strain adjusted SImGEn superlattice and SI/GE quantum well layers grown by MBE

We have fabricated mesa and ridge waveguide diodes from Si/Ge quantum well (QW) and short-period superlattice samples deposited by MBE on a (100) Si substrate. We have grown Si/Ge/Si1-xGex QW samples consisting of thin Ge wells where 20 MLs of Si are embedded in-between and followed by a SiGe layer elastically strained on a Si substrate as well as symmetrically strained on a strain symmetrizing buffer layer. We have also grown SimGen short-period, strained layer superlattices consisting of N periods of (m + n) monolayers per period which are deposited on a strain adjusting buffer layer. The edge emitting ridge waveguide diodes fabricated from this material with standard semiconductor processing techniques were polished on the <110> side faces and etched to a height of roughly 1.0 micrometers with lateral dimensions of roughly 100 micrometers width X 3 mm length. Also circular mesa diodes were fabricated with the same height and varying diameters from 100 micrometers to 800 micrometers and were provided with a metal ring contact on top defining the illumination window. Photocurrent and electroluminescence signals at h(nu) approximately 0.8 eV were detected at room temperature from QW samples. The emission characteristics as a function of strain and composition of the SLS and QW layers are discussed.