| Summary: | Cold atoms have proven to be a promising medium for numerous sensing and timing applications. Atomic clocks have provided the definition of the second since the 1960s and are essential for navigation and telecommunications. Increasingly precise clocks are capable of measuring small changes in the gravitational potential, which can be used to detect seismic activity, and atomic clock networks have been suggested for detecting dark matter. Cold atom-based gyroscopes have already demonstrated stability comparable to light-based gyroscopes, with the potential to exceed them.
For all of these applications, a compact and mobile system is required. Atom chips use microfabricated wires to produce magnetic traps that can confine atoms close to the surface of the chip using modest current. We hope to combine the mature fields of semiconductor fabrication with atom chips to produce chip-scale cold atom systems with electronics, trapping structures, antennas, sensors, and optics all integrated into a substrate. Our current work focuses on the integration of sensors and electronics through the production of CMOS-based atom chips.
The first CMOS atom chip was designed at the University of Applied Sciences of Wiener Neustadt (FHWN) and features a Z-wire with an adjustable geometry and photodiodes. Part of this thesis described the design and progress in implementing an experimental system built to measure the performance of this first chip. Rb atoms are accumulated and cooled in a magneto-optical trap, then sub-Doppler cooled to 70µK and loaded into an Ioffe trap located below the CMOS chip, generated by a copper Z-wire.
In parallel to the construction of this experimental system, further iterations of CMOS atom chips are being developed. Described in this thesis is the design of the second generation chip, referred to as chip1. This chip is designed to perform an atom chip Mach-Zehnder interferometric scheme using spatial modes, but with sensors and electronics integrated onto the chip. In addition to the modifiable Z-wire, this chip features avalanche photodiodes and single-photon avalanche photodiodes designed to detect very low light intensities, Hall sensors for magnetic field measurement, a direct-digital synthesiser for generating RF fields, and a serial interface for communication with the chip.
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