PhD Defense: Hari Lamsal
TITLE: Ultralow-power nonlinear optics using optical nanofibers in metastable xenon
ABSTRACT: Nonlinear optics (NLO) is a very broad field with applications ranging from frequency conversion and all-optical switching to quantum computing. For many of these applications, the use of low power lasers is desirable. Consequently, there is currently a push for the realization of new physical platforms enabling ultralow-power NLO. Here I perform research on a promising new ultralow-power NLO platform consisting of an optical nanofiber (ONF) suspended in a gas of metastable xenon atoms (Xe*). The origin of the strong nonlinearity in this platform is due to the tight confinement of the ONF guided evanescent mode (~ 1 μm2) over a long distance (~1 cm), and a resonant interaction of the mode with the surrounding atoms.
This work focusses on the results of two key experimental studies using this “ONF in Xe*” platform. In the first study, we investigate the transmission characteristics of ONF’s surrounded with a xenon plasma produced by low-pressure inductive RF discharge. In contrast with related experiments using rubidium vapor, we find essentially no degradation of optical transmission through the ONF’s as a function of time. We also observe a pronounced ONF transmission modulation effect that depends on the conditions of the xenon plasma, and may have practical applications.
The second study is motivated by the goal of producing high metastable state densities in the xenon gas surrounding the ONFs. Specifically, we investigate the physics required to promote a large fraction of the xenon atoms from the ground state to the metastable state using a recently proposed hybrid technique that combines RF discharge techniques with optical pumping from an auxiliary state in xenon. We study the effect of xenon pressure on establishing initial population in both the auxiliary state and metastable state via the RF discharge, and the role of the optical pumping beam power in transferring population between the states. We find experimental conditions that maximize the effects, and provide a robust platform for producing relatively large long-term metastable state densities. We expect these high Xe* densities to be a key enabling technology for ultralow-power NLO in the “ONF in Xe*” platform.
Defense will be held using Webex.