Searching for Exoplanets Using a Microresonator Astrocomb.

Orbiting planets induce a weak radial velocity (RV) shift in the host star that provides a powerful method of planet detection. Importantly, the RV technique provides information about the exoplanet mass, which is unavailable with the complementary technique of transit photometry. However, RV detection of an Earth-like planet in the 'habitable zone' requires extreme spectroscopic precision that is only possible using a laser frequency comb (LFC).

On the properties of single-mode optical resonators.

We study the quality factor of single-mode optical whispering gallery mode resonators using finite element method simulations, with a particular focus on the photonic belt resonator geometry. We experimentally observe a large difference between the quality factors of TM and TE modes in such resonators. Examining radiative losses, we conclude that the TM fundamental mode of single-mode resonators can have geometry related radiative losses caused by mode hybridization and coupling that limits their achievable quality factor.

Properties of fluoride microresonators for mid-IR applications.

We study crystalline fluoride microresonators for mid-infrared (mid-IR) applications. Whispering gallery mode resonators were fabricated with BaF, CaF, and MgF crystals. The quality factors were measured at wavelengths of 1.

Impact of cavity spectrum on span in microresonator frequency combs.

We experimentally study the factors that limit the span in frequency combs derived from the crystalline whispering gallery mode resonators. We observe that cavity dispersion is the key property that governs the parameters of the combs resulting from cascaded four wave mixing process. Two different regimes of comb generation are observed depending on the precise cavity dispersion behavior at the pump wavelength.

Polarization conversion loss in birefringent crystalline resonators.

Whispering gallery modes in birefringent crystalline resonators are investigated. We experimentally investigate the XY-cut resonators made with LiNbO3, LiTaO3, and BBO and observe strong influence of the resonator's shape and birefringence on the quality factor of the extraordinary polarized modes. We show that extraordinary modes can have lower Q and even be suppressed owing to polarization conversion loss.

High-Q UV whispering gallery mode resonators made of angle-cut BBO crystals.

We report an investigation on angle-cut beta barium borate (BBO) whispering gallery mode (WGM) resonators operating in the ultra violet (UV) wavelength range. A quality (Q) factor of 1.5 × 10(8) has been demonstrated at 370 nm.

Frequency comb from a microresonator with engineered spectrum.

We demonstrate that by varying the ratio between the linewidth and dispersion of a whispering gallery mode resonator we are able to control the number N of free spectral ranges separating the first generated comb sidebands from the pump. We observed combs with N = 19 and N = 1. For the comb with N = 1 we have achieved a span of over 200 nm using a 0.

Compensation of thermal nonlinearity effect in optical resonators.

Thermal nonlinearity is known to cause bistability in Whispering Gallery Mode (WGM) resonators and to destabilize the red slope of the Lorentzian resonant curve. We demonstrate an optical technique that allows compensation of the thermal effect and forces the resonances to appear linear with both red and blue slopes stable.

Phonon laser action in a tunable two-level system.

The phonon analog of an optical laser has long been a subject of interest. We demonstrate a compound microcavity system, coupled to a radio-frequency mechanical mode, that operates in close analogy to a two-level laser system. An inversion produces gain, causing phonon laser action above a pump power threshold of around 7 microW.

Thermal instability of a compound resonator.

We investigate the thermal and Kerr nonlinearity in a system of two optically-coupled silica microtoroid resonators experimentally and theoretically. A model for two coupled oscillators describing nonlinear resonance curves is developed. Stability of the static solutions is analyzed.

Generation of optical frequency combs with a CaF2 resonator.

We demonstrate optical frequency combs using the fluorite whispering gallery mode resonator as a nonlinear Kerr medium. Two regimes of generation are observed, giving the record low repetition rate of 13 GHz, equal to the cavity's free spectral range (FSR) or high repetition rates of multiples of cavity FSR. An intermediate regime was also observed.

Brillouin lasing with a CaF2 whispering gallery mode resonator.

Stimulated Brillouin scattering with both pump and Stokes beams in resonance with whispering gallery modes of an ultrahigh Q calcium fluoride resonator is demonstrated for the first time. The resonator is pumped with 1064 nm light and has 3 muW Brillouin lasing threshold. The scattering is observed due to the unique morphology of the resonator reducing the phase mismatch between the optical modes and the hypersound wave.

On the fundamental limits of Q factor of crystalline dielectric resonators.

The temperature dependence of the processes which fundamentally limit optical quality factor of ideal crystalline whispering gallery mode resonators is investigated. The example of CaF(2) is used to show that spontaneous Raman scattering is the main limitation of the quality factor at low temperatures. Stimulated Raman scattering is also shown to be important at any temperature.

Ultralow-threshold Raman lasing with CaF2 resonators.

We demonstrate efficient Raman lasing with CaF2 whispering-gallery-mode resonators. Continuous-wave emission threshold is shown to be possible below 1 microW with a 5mm cavity, which is to our knowledge orders of magnitude lower than in any other Raman source. Low-threshold lasing is made possible by the ultrahigh optical quality factor of the cavity, of the order of Q=5x10(10).

Morphology-dependent photonic circuit elements.

We theoretically propose and experimentally demonstrate the design of a novel one-dimensional ringlike macroscopic optical circuit element. The similarity between morphologies of an optical planar waveguide and a whispering-gallery axially symmetric solid-state resonator is used.

Optical vortices with large orbital momentum: generation and interference.

We demonstrate a method for generation of beams of light with large angular momenta. The method utilizes whispering gallery mode resonators that transform a plane electromagnetic wave into high order Bessel beams. Interference pattern among the beams as well as shadow pictures induced by the beams are observed and studied.