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Development of shallow trench isolation bounded single- photon avalanche detectors for acousto-optic signal enhancement and frequency up-conversion

Abstract

This dissertation describes the development of the first CMOS single photon avalanche diode (SPAD) fabricated in a deep-submicron commercial CMOS process. Single photon detection is often necessary for high-sensitivity, high dynamic range time-resolved optical measurements in diverse applications in medicine, biology, military, and optical communication links. Single photon avalanche diode (SPAD) detectors have become the device of choice and have made strong gains in recent years. They are unique in that they provide digital information of the arrival of an individual photon impinging on the detector, thus being a very powerful tool when time-of-arrival information and timing resolution are crucial. Timing precision of the detector will improve contrast in fluorescence lifetime imaging and resolution in laser ranging applications. Traditionally, single photon detectors have been fabricated using custom processes because of the conditions under which the devices operate under. Because of the need to sustain high currents and high electric- fields, special custom fabrication processes have been developed. These fabrication processes have great benefits such as low-noise, high detection efficiencies, low jitter, and tailored spectral responses towards longer wavelengths. However, these fabrication techniques are often undesirable due to increased capacitance from off- chip quenching, recharging, and processing circuitry, resulting in longer detector dead times and slower sampling rates. Furthermore, large-scale production and scalability to arrays is impractical. There has been a trend towards using Complementary Metal-Oxide- Semiconductor (CMOS) technology for constructing SPAD pixels and arrays with integrated circuitry to overcome these limitations. Though commercial CMOS technologies are by nature, generic, and are not designed for SPAD devices, they can still offer considerable advantages in certain areas where custom processes lack. This dissertation describes the modeling, simulation, and full characterization of a CMOS STI-bounded Single Photon Avalanche Diode (SPAD). State-of-the-art sampling rates, dead-time, and jitter performance are characterized, and the device is compared to traditional diffused-guard ring structures for solid-state SPADs. Further, novel applications of the CMOS SPAD for acousto-optic signal enhancement and frequency up-conversion of 1550nm are described. An optical scatter system for acoustic characterization of ultrasound responsive microbubbles and particles is designed and developed. Further, a novel method of fluorescence modulation using dye-loaded microbubbles is demonstrated

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