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Abstract # 263

R. Urata, L. Y. Nathawad, R. Takahashi, K. Ma, D. A. B. Miller, B. A. Wooley, and J. S. Harris, "Photonic A/D conversion using low-temperature-grown GaAs MSM switches integrated with Si-CMOS," J. Lightwave Technol. 21, 3104-3115 (2003)

By linking the unique capabilities of photonic devices with the signal processing power of electronics, photonically-sampled analog-to-digital (A/D) conversion systems have demonstrated superior performance over all-electrical A/D conversion systems. We adopt a photonic A/D conversion scheme using low-temperature (LT)-grown GaAs metal-semiconductor-metal (MSM) photoconductive switches integrated with Si-CMOS A/D converters. The large bandwidth of the LT GaAs switches and the low timing jitter and ultrashort width of mode-locked laser pulses are combined to accurately sample input frequencies up to several tens of GHz. CMOS A/D converters perform back-end digitization, and time-interleaving is used to increase the total sampling rate of the system. In this paper, we outline the development of this system, from optimization of the LT GaAs material, speed and responsivity measurements of the switches, bandwidth and linearity characterization of the first stage optoelectronic sample-and-hold, to integration of the switches to CMOS chips. As a final proof-of-principle demonstration, a two-channel system was fabricated with LT GaAs MSM switches flip-chip bonded to CMOS A/D converters. The prototype system exhibits ~3.5 effective-number-of-bits (ENOB) of resolution over a 40 GHz input signal band.

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