R. Hauffe

Crosstalk-enhanced polymer digital optical switch based on a W-shape

A three branch digital optical switch in polymers with a crosstalk of -30 dB is presented. Its crosstalk is insensitive to increasing heat power, which is the main advantage to ordinary DOS.

Methods for passive fiber chip coupling of integrated optical devices

A useful technique for high precision passive coupling of single mode optical fibers to integrated optical devices is crucial for cost effective packaging especially in multiport devices like switches (N/spl times/N) and other WDM components. These devices were fabricated on two different material bases, silicon on insulator (SOI) and polymers. In both cases the waveguides are based on the oversized rib waveguide concept and utilize silicon as a substrate. Two possible fabrication processes for this passive fiber chip coupling IN or ON silicon are presented and compared. The first approach involves a technology similar to flip chip fabrication using a sub- and superstrate, that allows separate processing of v-grooves for fiber alignment and the integrated optical devices. The self aligned mounting of the chip is achieved by a v-shaped rib-groove combination created by wet chemical etching, where the rib is the exact negative of the groove so that the flip chip is put on precisely defined crystal planes rather than on sensitive edges, which would be the case when using rectangular alignment ribs. The second approach utilizes the same chip for waveguides and fiber alignment structures which makes it possible to define both in the same lithographic step and thereby eliminating any vertical displacement. Processing difficulties arise primarily from completely different processing requirements of fiber aligning v-grooves and integrated waveguides. The need to define patterns of the size of only several microns (/spl mu/m) in the proximity to deep grooves makes the use of an electrophoretic photoresist necessary that is deposited via galvanic means on the extremely nonplanar surface. Both processes allow for fiber chip alignment precisions in the sub-/spl mu/m range which was also experimentally verified with coupling losses as low as 0.7 dB per end-face. The fabrication processes along with experimental and theoretical results are presented.

Polymer digital optical switch with an integrated attenuator

A polymer digital optical switch with an integrated attenuator is presented. This switch shows a crosstalk (CT) value of -46 dB.

Passive alignment of single-mode fibers to integrated polymer waveguide structures utilizing a single-mask process

A fabrication process for high precision passive fiber chip coupling is presented. The difficulties of structuring highly nonplanar surfaces were solved by using an electrophoretic photoresist and introducing additional structures to prevent wide holes. The method involves only a single lithographic step for structuring the polymer waveguide and fiber aligning structures in Si and thereby minimizing the horizontal displacement. The loss due to fiber displacement is about 0.7 dB per front face.

Crosstalk-optimized integrated optical switching matrices in polymers by use of redundant switch elements

We present a crosstalk (CT) optimized digital optical switching matrix (4/spl times/4) based on the oversized rib waveguide concept in polymers utilizing redundant switches in the matrix configurations and tapered waveguide crossing sections yielding an average CT of -42 dB (all CT values below -30 dB) without any additional space requirements (on a 4-in wafer).

Digital Optical Circuit Switches and Switching Matrices in Polymers

Summary We discuss and compare different designs of digital optical switches (DOS) in polymers utilizing the thermo optical effect (y-branched DOS, three branched DOS, DOS cascade with partially merged switching stages, DOS with integrated attenuators) with respect to their applicability in switching matrices and their crosstalk (CT) performance. The underlying oversized rib waveguide concept is also briefly discussed with emphasis on the integration of absorbers. Finally we present results for an optimized matrix switch design.

An improved polymer digital optical switch with cross talk of -46 dB

We present a polymer digital optical switch in which an attenuator is integrated. With the help of this an excellent cross talk (CT)) of -46 dB is obtained.