Improving bandwidth of parallel-fed travelling wave photo detectors

Abstract

Parallel-fed travelling wave photo detectors (TWPDs) are used frequently in high power, high bandwidth applications. However increasing the number of photodiodes within their structure in order to increasing high power capabilities significantly reduces bandwidth. So there is trade-off. We have improved -3dB bandwidth of a parallel-fed TWPD, with four photodiodes, by varying its structural parameters. Resultant bandwidth of the photo detector is 105GHz which shows 25GHz improvement with respect to TWPDs that have been reported previously. S22 of this photo detector is below -10dB within its bandwidth which shows that Bragg frequency is much higher than bandwidth.