Optical Resonators Integrated into a Hollow Core Photonic Crystal Fiber for Enhanced Light-Matter Interactions

Abstract

The focus of this thesis is to investigate and fabricate a platform that can facilitate the enhancement of light-matter interactions. By tightly confining the photons and atoms to the same region of space, the probability of interaction is drastically increased as compared to free space interactions. Specifically, we focus on forming an optical cavity (or resonator) incorporated into a hollow-core photonic crystal fiber (HCPCF) using two distinct types of reflective mirrors along the axis of the fiber while still permitting atoms to be loaded into the region of high field confinement.

One means of pursuing this goal that we explored was to propose and numerically simulate two methods for implementing Bragg gratings in a HCPCF. These two methods leave the hollow-core unobstructed and are both based on controlled selective injection of photosensitive polymers into the photonic-crystal region of the hollow-core fiber, followed by interference photolithography. We report the results of numerical simulations for the hollow core fiber with Bragg gratings formed by the two methods. We find that a reflectivity of > 99.99% should be achievable from such fiber-integrated mirrors. Such a device could support high cooperativity and strong coupling regimes to be achieved.

We also demonstrate a fiber-integrated Fabry-Pérot cavity formed by attaching a pair of dielectric metasurfaces to the ends of a hollow-core photonic-crystal fiber segment. The metasurfaces consist of perforated membranes designed as photonic-crystal slabs that act as planar mirrors but can potentially allow injection of gases through their holes into the hollow core of the fiber. We have so far observed cavities with finesse of 11 and Q-factors of ~ 4.5 × 10^5, but much higher values should be achievable with improved fabrication procedures. We expect this device to enable the advancement of new fiber lasers, enhanced gas spectroscopy, and studies of fundamental light-matter interactions and nonlinear optics. These mirrors can be designed to be polarization dichroic — transparent for one polarization and reflective for another. This unique property can be exploited to allow for all signals to be directed along the high optical depth axis of the cavity and may provide a excellent platform for applications such as optical switching.

Finally, we develop a novel protocol for a single photon all-optical transistor and how it may be implemented in the above mentioned fiber cavity systems. This unique scheme utilizes a far off-resonant vacuum cavity mode to stimulate a Raman absorption process of a source photon which may be switched off by the insertion of a single gate photon into the cavity mode. Relatively high switching contrasts and ratios for the source photon transmission can be obtained in our system.