Thermal noise of whispering gallery resonators

By direct application of the fluctuation-dissipation theorem, we numerically calculate the fundamental dimensional fluctuations of crystalline CaF2 whispering gallery resonators in the case of structural damping, and the limit that this noise imposes on the frequency stability of such resonators at both room and cryogenic temperatures. We analyze elasto-optic noise - the effect of Brownian dimensional fluctuation on frequency via the strain-dependence of the refractive index - a noise term that has so far not been considered for whispering-gallery resonators. We find that dimensional fluctuation sets a lower limit of 1E-16 to the Allan deviation for a 10-millimeter-radius sphere at 5 K, predominantly via induced fluctuation of the refractive index.Comment: 7 pages, 3 figure

A silicon single-crystal cryogenic optical resonator

We report on the demonstration and characterization of a silicon optical resonator for laser frequency stabilization, operating in the deep cryogenic regime at temperatures as low as 1.5 K. Robust operation was achieved, with absolute frequency drift less than 20 Hz over 1 hour. This stability allowed sensitive measurements of the resonator thermal expansion coefficient ($\alpha$). We found $\alpha=4.6\times10^{-13}$ ${\rm K^{-1}}$ at 1.6 K. At 16.8 K $\alpha$ vanishes, with a derivative equal to $-6\times10^{-10}$ ${\rm K}^{-2}$. The temperature of the resonator was stabilized to a level below 10 $\mu$K for averaging times longer than 20 s. The sensitivity of the resonator frequency to a variation of the laser power was also studied. The corresponding sensitivities and the expected Brownian noise indicate that this system should enable frequency stabilization of lasers at the low-$10^{-17}$ level.Comment: 5 pages, 5 figure

Spectrally narrow, long-term stable optical frequency reference based on a Eu3+^{3+}:Y2_{2}SiO5_{5} crystal at cryogenic temperature

Using an ultrastable continuous-wave laser at 580 nm we performed spectral hole burning of Eu$^{3+}$:Y$_{2}$SiO$_{5}$ at very high spectral resolution. Essential parameters determining the usefulness as a "macroscopic" frequency reference: linewidth, temperature sensitivity, long-term stability were characterized, using a H-maser stabilized frequency comb. Spectral holes with linewidth as low as 6 kHz were observed and the upper limit of the drift of the hole frequency was determined to be on the order of 5$\pm$3 mHz/s. We discuss necessary requirements for achieving ultra-high-stability in laser frequency stabilization to these spectral holes.Comment: 4 pages, 4 figure

Currents of second kind in electroweak interactions of leptons with nucleons and nuclei

Matrix elements of nucleon currents are investigated in the paper aiming at the search of possible contributions of currents of the second kind into differential probabilities of betta-decays and differential sections of the neutrino scattering on light nuclei. As a result expressions for differential sections of scattering and differential probabilities of betta-decays of nuclei and nucleons with the account of currents of the second kind, right lepton currents and mass of neutrino have been obtained. The paper results may find their field of application in physics of elementary particles and nuclear physicsAvailable from VNTIC / VNTIC - Scientific & Technical Information Centre of RussiaSIGLERURussian Federatio