An integrated heterojunction bipolar transistor cascode opto-electronic mixer

An integrated electrically pumped opto-electronic mixer consisting of two I nP/GaInAs heterojunction bipolar transistors in a cascode configuration is demonstrated, Intrinsic downconversion gains of 18.2 and 8.9 dB at RP optic al modulation frequencies of 3 and 9.5 GHz were obtained, The performance o f the cascode mixer and a single heterojunction bipolar transistor (IJ;ET) opto-electronic mixer are compared. The performance of the cascode mixer wa s superior to the single HET mixer, mainly at high frequencies, Up and down mixing conversion gains were measured and found comparable, A simulation w as carried out by solving the nonlinear differential equations that corresp ond to the large-signal equivalent circuit. The results of the simulation e nabled us to identify the principal nonlinear components in the equivalent circuit.