D. Coppee

Spatially modulated light detector in CMOS with sense-amplifier receiver operating at 180 Mb/s for optical data link applications and parallel optical interconnects between chips

We present a first realization of a detector receiver combination based on the spatially modulated light detector (SML-detector). The SML-detector gives an output signal that has a shorter falling edge than that of a conventional CMOS detector. It is combined with a sense-amplifier in a standard 0.8-/spl mu/m CMOS technology, allowing one to receive over 155-Mb/s of light pulses at 5.6-/spl mu/W average light input power for /spl lambda/=860 nm. The detector 3-dB bit-rate is 300 Mb/s for this wavelength and for the used spatial topology. For /spl lambda/=635 nm the detector 3-dB bitrate is 510 Mb/s. Apart from monolithic integration of detector and receiver, further signal processing circuitry (including digital signal processing functions) can be integrated on the same chip. The compact system allows conceiving low cost densely packed optoelectronic receivers for parallel optical interconnects and for wavelength division multiplexing applications in the visible and the near-infrared wavelength range.

Experimental study of the spatially-modulated light detector

Abstract Usually, integrated detectors in CMOS exhibit long recovery times, limiting the detector bandwidth to only a few MHz. This is due to the long absorption length and the slow diffusion speed of photo-generated carriers. Different approaches have been proposed to solve these problems hereby taxing the compatibility with standard CMOS fabrication processing. We present a novel detector for high-speed light detection in standard CMOS. To solve the problem of slow CMOS-detector recovery, the incident light is spatially modulated and the spatially modulated component of the photo-generated carrier distribution is measured. Though only a single light input signal is required, from the detector on, analog signal processing can be achieved fully differentially. Subsequently, expected good PSRR (Power supply rejection ratio) allows integration with digital circuits. Avoiding hybridization eliminates the conventional problems caused by bonding-pad capacitance, bonding-wire inductance. This reduces the associated signal degradation. In addition, the very low detector capacitance, due to the low effectively used detector area and the low area capacitance of the n-well junction, yields high voltage readout of the detector. This facilitates further amplification and conversion to digital signal levels. The detector will be applicable in arrays due to expected low cross talk. The expected fields of operation involve: serial and parallel optical communication receivers (e.g. for WDM), DVD-reading heads with integrated amplifier, etc. First measurements show 200 Mbit/s operation with a detector-responsivity of 0.05 A/W at λ=860 nm and 0.132 A/W at λ=635 nm. The detector has inherently a low capacitance, in this case only 50 fF (for an effective detector area of 70×70 μm2).

Demonstration of a monolithic multichannel module for multi-Gb/s intra-MCM optical interconnects

In this letter, we report on the demonstration of a 2.48-Gb/s multichannel optical data-link for intramultichip module interconnects. The optical module was fabricated in polymethylmethacrylate (PMMA) by deep proton lithography and monolithically integrates micromirrors and cylindrical lenses. With the same technology, we have also fabricated a single-channel optical bridge and used this component to demonstrate a proof-of-principle optical intrachip interconnect by establishing a digital data-link between optoelectronic transceivers integrated on the same chip.

The spatially modulated light detector

Summary form only given. We present a novel detector for high-speed light detection in standard complementary metal-oxide semiconductor (CMOS). The device consists of a substrate wherein the light being absorbed is spatially modulated thereby creating a signal with a spatially modulated component in that substrate. A shadow mask spatially modulates the incident, and consequently, the absorbed light. By measuring the magnitude of the spatial frequency component in the minority carrier distribution, a fast detector is conceived.

Fabrication and experimental demonstration of a multichannel module for intra-MCM optical interconnects

We use deep proton irradiation of poly(methyl methacrylate) (PMMA) as a deep-etch lithographic technique that allows us to fabricate monolithic structures integrating refractive microlenses, micromirrors, fiber positioning holes, standoffs, and alignment features. The technique works as follows: a proton beam in the energy range between 5 and 10 MeV, passing through a metal mask, impinges on a high-molecular-weight PMMA substrate.