Degenerate and Non-Degenerate Two-Photon Rubidium Frequency Standard

Nguyen, Tin Nghia

Graduate Thesis Or Dissertation

Degenerate and Non-Degenerate Two-Photon Rubidium Frequency Standard Public Deposited

Analytics

Citations

Citeable URL: https://scholar.colorado.edu/concern/graduate_thesis_or_dissertations/c821gm63p

Abstract

Compact and portable optical clocks based on intrinsic properties of atoms or molecules play important roles far from basic timekeeping. These clocks, such as the two-photon rubidium clocks, only deliver a fraction of the timing stability of the best optical atomic clocks due to the broader linewidth of the atomic transition of choice and the environmental factors. This dissertation details the design and construction of two compact optical atomic clocks based on two different excitation schemes for the two-photon transition of rubidium. The first clock was based on the degenerate excitation scheme using two counter-propagating photons of the same wavelength. The clock featured a small physics package and a control system based on a low-cost and commercial field-programmable gate array (FPGA) chip. This chip can provide phase modulation techniques to lock lasers to optical frequency references together with all the required servos to construct an optical atomic clock. A reliable, active, long-term residual amplitude modulation (RAM) suppression scheme that relies on complex modulation was also incorporated to the same FPGA chip and was demonstrated to suppress up to 60 dB of RAM with the remaining RAM level at -100 dBc. With this RAM suppression, the clock’s stability was no longer limited by RAM but light shift and temperature shiftafter long averaging times.

To mitigate light shift and temperature shift in two-photon rubidium clock, I proposed a scheme for interrogating a warm rubidium vapor using two different clock lasers. This approach not only allowed for higher signal-to-noise (SNR) ratio for an improved short-term performance, but also offered light shift cancellation and temperature shift suppression to maintain long-term stability. Finally, this dissertation details the design, construction, and characterization of a preliminary setup following this new excitation scheme.

Creator