Radiation pressure effects in a suspended Fabry-Perot cavity

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 2006.Includes bibliographical references (p. 65-67).We report on experimental observation of radiation-pressure induced effects in a high-power optical cavity. These effects play an important role in next generation gravitational wave detectors, as well as quantum non-demolition devices. We describe two experiments in which a low-transmission input mirror and near-perfectly-reflective end mirror are suspended as pendulums. A unified model of optomechanical coupling is presented, whereby a strong coherent laser field interacts with a classical harmonic oscillator. We show that such a system is well described using standard techniques from control theory. We measure the properties of an optical spring, whereby the optical field increases the rigidity of the pendulum mode of the mirrors; during our first (Phase 1) experiment, we measure an optical rigidity of K = (3.08 t 0.09) x 104 N/m, corresponding to an optical rigidity that is 6000 times stiffer than the mechanical stiffness. In our second (Phase 2) experiment with higher finesse and lower mirror mass, we find an unprecedented optical rigidity Ko = (9.60 ± 0.12) x 105 N/m. We also measure and characterize the parametric instability, caused by the coupling of the cavity field to the acoustic modes of the mirror, and find an instability strength R - 3.(cont.) We discuss the noise suppression features of an optically rigid system, and demonstrate a strong-coupling radiation pressure cooling of the mirror motion. A discussion of the path towards a measurement of the quantum mechanical state of the bulk mirror motion in future experiments is included.by Jason Scott Pelc.S.B

Measurement of radiation-pressure-induced optomechanical dynamics in a suspended Fabry-Perot cavity

We report on experimental observation of radiation-pressure induced effects in a high-power optical cavity. These effects play an important role in next generation gravitational wave (GW) detectors, as well as in quantum non-demolition (QND) interferometers. We measure the properties of an optical spring, created by coupling of an intense laser field to the pendulum mode of a suspended mirror; and also the parametric instability (PI) that arises from the nonlinear coupling between acoustic modes of the cavity mirrors and the cavity optical mode. Specifically, we measure an optical rigidity of $K = 3 \times 10^4$ N/m, and PI value $R = 3$.Comment: 4 pages, 3 figure

Photon pair generation in hydrogenated amorphous silicon microring resonators

We generate photon pairs in a-Si:H microrings using a CW pump, and find the Kerr coefficient of a-Si:H to be $3.73 \pm 0.25 \times 10^{-17}m^2/W$. By measuring the Q factor with coupled power we find that the loss in the a-Si:H micro-rings scales linearly with power, and therefore cannot originate from two photon absorption. Theoretically comparing a-Si:H and c-Si micro-ring pair sources, we show that the high Kerr coefficient of this sample of a-Si:H is best utilized for microrings with Q factors below $10^3$, but that for higher Q factor devices the photon pair rate is greatly suppressed due to the first order loss.Comment: 10 pages, 5 figure