A. Umbach

High-power performance of a high-speed photodetector

The high power performance of an ultrafast GaInAs p-i-n photodiode photodetector with integrated optical waveguide and biasing network is demonstrated. Up to about +20 dBm optical peak power the FWHM of 9 ps remains nearly constant proving the applicability in EDFA-based 40 Gbit/s receivers.

Ultrafast, high-power 1.55 /spl mu/m side-illuminated photodetector with integrated spot size converter

40 Gbit/s photodetectors require high bandwidth at high power levels, as supplied by waveguide-integrated p-i-n diodes on InP. By monolithic integration of a spot size transformer a responsivity of 0.5 A/W is achieved and fiber alignment tolerances are increased by one order of magnitude.

37 GHz bandwidth InP-based photoreceiver OEIC suitable for data rates up to 50 Gb/s

A photoreceiver optoelectronic integrated circuit based on InP with a bandwidth of 37 GHz is presented. The receiver consists of a 50 GHz waveguide-integrated photodiode and a distributed amplifier with a bandwidth of 39.5 GHz, which is composed of four high-electron mobility transistors. A system experiment at 40 Gb/s receiving an return-to-zero coded optical input signal is demonstrated, and a good quality of eye pattern is achieved.

Ultrafast monolithically integrated InP-based photoreceiver: OEIC-design, fabrication, and system application

An InP-based photoreceiver OEIC for /spl lambda/=1.55 /spl mu/m with a bandwidth of 27 GHz is reported. The receiver design, fabrication and characterization is presented. The device consists of an optical waveguide-fed pin-photodiode and a coplanar traveling-wave amplifier being composed of four GaInAs-AlInAs-InP-HEMTs. The photodiode exhibits an external quantum efficiency of 30% and a 3-dB power bandwidth of 35 GHz. HEMTs with 0.7-/spl mu/m gate length, integrated on semi-insulating optical waveguide layers show cutoff frequencies f/sub T//f/sub max/ of 37/100 GHz at zero gate bias. Traveling-wave amplifiers with 0.5-/spl mu/m gate HEMTs have 28-GHz bandwidth. The receiver OEIC is packaged into a module with fiber pigtail and operates successfully within an SDH based 20-Gb/s transmission system. An overall system sensitivity of -30.5 dBm was achieved at a BER=10/sup -9/ after signal transmission over 198-km dispersion shifted fiber.

Narrow-band photoreceiver OEIC on InP operating at 38 GHz

We report on the successful monolithic integration of an InP-based photoreceiver operating in the narrow band around 38 GHz at a wavelength of 1.55 /spl mu/m, The optoelectronic integrated circuit (OEIC) incorporates two types of high-speed devices, a submicrometer metal-semiconductor-metal photodetector (MSM PD) made of InGaAs-InP and quarter-micrometer high-electron-mobility-transistors (HEMTs) based on a lattice-matched InGaAs-InAlAs-InP layer stack. For this purpose a fabrication process requiring only twelve main steps including a metal-organic chemical vapor deposition growth for the MSM PD layers and a MBE regrowth for the HEMT layers has been developed. At 38 GHz, a responsivity of 3.5 A/W for the OEIC is achieved.

Ultra-wide-band (>40 GHz) submicron InGaAs metal-semiconductor-metal photodetectors

Submicron feature size InGaAs metal-semiconductor-metal (MSM) photodetectors with 3-dB bandwidths in excess of 40 GHz are demonstrated. Devices with a 0.3-/spl mu/m-thick active layer and an interelectrode spacing of <0.5 /spl mu/m show a roll-off of the frequency response of /spl les/2 dB up to 40 GHz when operated at 5-V bias under front illumination with 1.3-/spl mu/m light.

A monolithically integrated balanced mixer OEIC on InP for coherent receiver applications

We report on the fabrication and characterization of a monolithically integrated balanced mixer receiver on InP consisting of a 3-dB coupler, twin balanced waveguide integrated photodiodes, and a low-noise electrical preamplifier. The receiver OEIC exhibits a transimpedance of 223 Omega and a 3-dB bandwidth of 1 GHz. Heterodyne operation and local laser noise cancellation capability of the OEIC are demonstrated.<<ETX>>

Technology of InP-based 1.55-/spl mu/m ultrafast OEMMICs: 40-Gbit/s broad-band and 38/60-GHz narrow-band photoreceivers

For future long-haul communication systems operating at bitrates of 40 Gbit/s and for broad-band mobile access systems using 38- or 60-GHz carrier frequencies, ultrafast photoreceivers have to be provided. Therefore, an integration concept for InP-based optoelectronic microwave monolithic integrated circuits for the 1.55-/spl mu/m wavelength regime is demonstrated, which allows independent optimization of the constituting devices. Two different types of photodetectors (PDs), a waveguide-integrated PIN photodiode (PD) and a top-illuminated metal-semiconductor-metal PD, both having bandwidths of up to 70 GHz, have been developed. These are fabricated together with different amplifier designs employing high electron mobility transistors which exhibit transit frequencies of up to 90 GHz. The application to a 40-Gbit/s broadband photoreceiver for high-bit-rate time-division multiplexing systems is reported, as well as the application to 38- and 60-GHz narrow-band photoreceivers for use as optic/millimeterwave converters in mobile communication systems.

A novel flexible, reliable and easy to use technique for the fabrication of optical spot size converters for InP based PICs

Spot size converters (waveguide tapers) are key elements for photonic integrated circuits (PICs) since they significantly reduce the effort and cost of the device packaging. In comparison to other technologies like micro lenses or lensed fibres the implementation of spot size converters can also reduce the optical insertion loss of the devices. The basic technological challenge is the fabrication of a vertical ramp with a maximum height of around 1 /spl mu/m and a length of 500-1000 /spl mu/m. Several approaches to form this ramp have been reported including shadow mask etching, shadow mask epitaxy and selective area growth. All this methods have in common that they require special processes which are rather complicated, expensive and inflexible in terms of tailoring of the ramp profile. In this paper, we present a novel method for the fabrication of spot size converters which can produce almost arbitrary taper profiles and requires only standard lithography and etching processes and can therefore easily be implemented into standard waveguide processes.

Ultrafast, high-power waveguide fed photodetector with integrated spot size converter

The monolithic integration of an ultrafast photodetector with an spot size transformer is presented. Using a shifting mask technique optimized taper ramp profiles are fabricated. The integrated devices exhibit a more than doubled responsivity (0.7 A/W) and about one magnitude higher misalignment tolerances compared to devices without spot size converters. The ultra large bandwith (f/sub 3dB/>50 GHz) and the excellent high power behaviour is unimpaired by the integration of the spot size converter.