40 research outputs found
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. It is shown that thermal nonlinearity is responsible for driving the eigenfrequencies of the two resonators apart, making the normal modes of the system unstable as the pump power grows. The red-detuned normal mode becomes unstable for certain pumping powers
Fundamental thermal fluctuations in microspheres
We present a theoretical analysis and the results of measurements of thermorefractive noise in microcavities. These measurements may be considered direct observations of fundamental fluctuations of temperature in solid media. Our experimentally measured noise spectra are in agreement with our theoretical model
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. Raman lasing spectrum similar to modulation instability in fibers was observed for the first time to the best of our knowledge
Enhanced photothermal displacement spectroscopy for thin-film characterization using a Fabry-Perot resonator
We have developed a technique for photothermal displacement spectroscopy that is potentially orders of magnitude more sensitive than conventional methods. We use a single Fabry-Perot resonator to enhance both the intensity of the pump beam and the sensitivity of the probe beam. The result is an enhancement of the response of the instrument by a factor proportional to the square of the finesse of the cavity over conventional interferometric measurements. In this paper we present a description of the technique, and we discuss how the properties of thin films can be deduced from the photothermal response. As an example of the technique, we report a measurement of the thermal properties of a multilayer dielectric mirror similar to those used in interferometric gravitational wave detectors
Phonon laser action in a tunable, two-level photonic molecule
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 50 W. The device features a continuously tunable, gain
spectrum to selectively amplify mechanical modes from radio frequency to
microwave rates. Viewed as a Brillouin process, the system accesses a regime in
which the phonon plays what has traditionally been the role of the Stokes wave.
For this reason, it should also be possible to controllably switch between
phonon and photon laser regimes. Cooling of the mechanical mode is also
possible.Comment: 4 pages, 4 figure
Finite element modeling of coupled optical microdisk resonators for displacement sensing
We analyze normal mode splitting in a pair of vertically coupled microdisk
resonators. A full vectorial finite element model is used to find the eigen
frequencies of the symmetric and antisymmetric composite modes as a function of
coupling distance. We find that the coupled microdisks can compete with the
best Fabry-Perot resonators in displacement sensing. We also show how we
configured FreeFem++ for the sphere eigenvalue problem.Comment: 10 pages, 4 figures, 1 FreeFem++ script (download and unzip the paper
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