Hybrid Polymer/MSM Traveling Wave Photodetectors

Distributed traveling-wave photodetectors (TWPDs) are attractive devices because of their capability for high speed, high efficiency, and high saturation power handling. The bandwidth of surface-illuminated photodetectors (PDs) is limited by the bandwidth-efficiency product, but this limit can be avoided in distributed TWPDs because the light is absorbed in a distributed way along the transmission lines. The use of a polymer material for the optical waveguide is an attractive alternative to complex growth procedures for waveguides in semiconductors because polymer optical waveguides can provide low propagation loss and cost effectiveness. We have designed and fabricated monolithic distributed balanced traveling wave metal-semiconductor-metal photodetectors (MSM PDs) distributed along single mode polymer optical waveguides. These monolithically integrated polymer optical waveguides on a semiconductor can provide efficient optical interconnects in an optoelectronic circuit. A responsivity of 0.44 A/W and a 3 dB bandwidth of 10 GHz were obtained in a photodetector array with 5 MSM PDs. A high photocurrent of 7.3 mA was measured in an array having 8 MSM PDs.

Figure 4. Distributed balanced traveling wave photo-detector consisting of 
InGaAs MSM photodetectors
distributed along polymer optical waveguides.

“Design and Fabrication of Monolithic Distributed Traveling Wave Photodetectors Integrated with Polymer Optical Waveguides,” J. Kim, W.B. Johnson, S. Kanakaraju, W.L. Cao, W.N. Herman, and C.H. Lee, IEEE Trans. on Electron Devices 54, 3216(2007).

“Demonstration of balanced coherent detection using polymer optical waveguide integrated distributed traveling-wave photodetectors, Junghwan Kim, W. B. Johnson, S. Kanakaraju, W. N. Herman, and Chi H. Lee, Optics Express 17, 20242(2009).