VCSEL-based smart pixels

Smart pixels incorporating vertical-cavity surface-emitting lasers (VCSELs) have shown great potential for use in optical computing systems and photonic switching networks because the integration of the VCSEL makes optical circuits easy to construct. We have developed integration with a VCSEL, MESFETs, and a metal-semiconductor-metal (MSM) photodetector. In this device, both NOR- and OR-types of operation can be performed with the same circuit. The device operated at a high contrast ratio of more than 30 dB with optical gain. It also showed the 3-dB bandwidth of 220 MHz with 300-/spl mu/W input power. We recently proposed a novel structure that uses three-dimensional integration of the compound semiconductor thin-film and a silicon circuit. The VCSEL and photodetector layers are bonded onto a silicon circuit using polyimide. This method does not require any alignment before wafer bonding. The fabrication process for the photonic circuit is the same technology that is used in our monolithic integrated smart pixel, so it facilitates a wafer-scale fabrication process. To demonstrate this technology, we fabricated an MSM photodetector on a silicon substrate.