Vertical cavity modulator for optical interconnection and its high speed performance

Free-space smart-pixel optical interconnect architecture promises to relieve the interconnect bottleneck in high-speed parallel interconnection and switching systems. Vertical cavity Fabry-Perot multiple quantum well (MQW) modulators, which offers high on-off contrast, low insertion loss, low operating voltage swing, low chirp and easy to be integrated with silicon electronics is one of the most promising devices. A low chirp vertical cavity Fabry-Perot modulator where the top and bottom mirrors are made of distributed Bragg reflector (DBR), the undoped regions between top mirrors and intracavity contact region (n-doped) contain 26 GaAs/Al_0.35Ga_0.5As quantum wells. By applying a voltage across the quantum well regions through intracavity contacts (the n-doped region), the absorptive characteristics of the active region at the cavity's resonance wavelength can be modified through the quantum-confined Stark effect (QCSE). The device under test is integrated with a microwave probe for efficient wafer level GHz probing without further high frequency packaging. To minimize the parasitic capacitance of the probe pads, the conducting region underneath probe pads is etched away and planarized with low dielectric material-electronics resins BCB. In this paper, we report the low switching voltage with only 3.5 V, high contrast ratio of 10:1 and high bandwidth of 16 GHz. The effects of incident laser power on the contrast ratio and modulation bandwidth were also discussed.