An investigation of electro-optical mixing using a GaAs MESFET has been performed. Since the optical signal illuminates the exposed GaAs regions along the gate of the MESFET, fiber to MESFET coupling is analyzed. It is shown that because the MESFET gate region is not designed to be compatible with the fiber core geometry, only a small fraction of the photons available for illumination contribute to the electrical output of the MESFET. We have shown electro-optical mixing performance, achieved when the gate region is illuminated with an optical signal modulated at 400 MHz, and an electrical signal at 1 GHz is applied to the gate. The MESFET output measured on a spectrum analyzer shows upper and lower sideband frequencies at 1400 and 600 MHz respectively. The mixer circuit implemented, resulted in 69 dB LO to RF isolation and perfect LO to IF isolation. A conversion loss, which included fiberoptic link loss, of 48 dB was measured. Mixing with LO frequencies of up to 3.8 GHz were achieved.

Date Published: 5 January 1990
PDF: 9 pages
Proc. SPIE 1177, Integrated Optics and Optoelectronics, (5 January 1990); doi: 10.1117/12.963346

Published in SPIE Proceedings Vol. 1177:
Integrated Optics and Optoelectronics
Leon McCaughan; Mark A. Mentzer; Song-Tsuen Peng; Henry J. Wojtunik; Ka Kha Wong, Editor(s)