Crystalline Whispering Gallery Mode Resonators for Quantum and Nonlinear Optics

Citation

Grudinin, Ivan Sergeevich (2008) Crystalline Whispering Gallery Mode Resonators for Quantum and Nonlinear Optics. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/3J52-QW65. https://resolver.caltech.edu/CaltechETD:etd-05132008-133522

Abstract

This work describes a series of projects and technology developments aimed at the realization of a solid-state photonic-ionic trap for quantum optics experiments. The projects however, are not constrained to this goal and explore the fields of nonlinear optics and fabrication techniques.

Fabri-Perot resonators have transformed the optical technology and can be found in many devices that utilize laser radiation. Whispering gallery mode resonators (WGMR) are relatively new elements and have such advantages as compactness, highest optical quality factors, and relative ease of fabrication. Small optical mode volume and long storage times allow record low thresholds of various nonlinear processes. Raman and Brillouin lasing, second and third harmonic generation, parametric oscillations and four wave mixing have all been enhanced in WGM resonators. Compared to glass microspheres, crystalline WGM resonators have higher nonlinear coefficients, may not be sensitive to water vapor, and have generally higher purity leading to record optical quality (Q) factors. Zero phonon lines of ions in crystals enable applications in cavity QED with single ions.

A novel application of diamond turning to fabrication of axially symmetric crystalline optical resonators is described. This technique enabled crystalline WGM microresonators, multiple resonators coupled via the evanescent field, and a single mode resonator. Crystalline resonators having a record high optical Q of 10¹¹ were demonstrated. Fundamental limits of the Q factor were investigated and Q=10¹⁵ was predicted at cryogenic temperatures. Record low threshold and high efficiency of stimulated Raman and Brillouin scattering led to the first observations of these effects in crystalline cavities. Brillouin and Raman lasers based on WGM resonators are expected to have very narrow linewidth. A cryogenic setup was developed that allowed observation of WG modes at low temperatures. Crystalline cavity was used as a reference for narrowing a linewidth of a commercial diode laser with a Pound-Drever-Hall technique for the first time. A device based on a fused silica WGMR was used to generate beams with large angular momenta. In addition, a Fabri-Perot cavity was used to sense thermal expansion of mirrors to derive thermal expansion and temperature conductivity of thin optical coatings.

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