Hossein Rokhsari

Analysis of Radiation-Pressure Induced Mechanical Oscillation of an Optical Microcavity

Microcavities can enter a regime where radiation pressure causes oscillation of mechanical cavity eigenmodes. We present a detailed experimental and theoretical understanding of this effect, and report direct scanning probe spectroscopy of the micro-mechanical modes.

Loss characterization in microcavities using the thermal bistability effect

We investigate the role of absorption and scattering losses in limiting the quality factor of toroidal micro-cavities by monitoring the threshold power for thermal bistability in these structures.

Theoretical and experimental study of radiation pressure-induced mechanical oscillations (parametric instability) in optical microcavities

Radiation pressure can couple the mechanical modes of an optical cavity structure to its optical modes, leading to parametric oscillation instability. This regime is characterized by regenerative oscillation of the mechanical cavity eigenmodes. Here, we present the first observation of this effect with a detailed theoretical and experimental analysis of these oscillations in ultra-high-Q microtoroids. Embodied within a microscale, chip-based device, this mechanism can benefit both research into macroscale quantum mechanical phenomena and improve the understanding of the mechanism within the context of laser interferometer gravitational-wave observatory (LIGO). It also suggests that new technologies are possible that will leverage the phenomenon within photonics.

Observation of Kerr nonlinearity in microcavities at room temperature.

We have devised and experimentally verified a method for observation of the optical Kerr effect in microcavities at room temperature. The technique discriminates against the much larger and typically dominant thermal component of nonlinearity by using its relatively slow frequency response. Measurement of the Kerr coefficient or equivalently of the third-order nonlinear susceptibility of the cavity material is demonstrated for a silica microcavity. With this approach, useful information about the characteristic thermal response time in microresonators can also be acquired.

Characterization of a Radiation-Pressure-Driven Micromechanical Oscillator

We present results of an experimental study of the oscillation frequency, linewidth, RF-spectrum and the phase noise of a radiation-pressure-driven optomechanical oscillator in a microtoroidal geometry. Through this study we identify the critical parameters that can be used for tailoring the desired characteristics of this device

Brownian noise in radiation-pressure-driven micromechanical oscillators

The authors demonstrate Brownian-noise-limited operation of an optomechanical oscillator, wherein mechanical oscillations of a silica optical microcavity are sustained by means of radiation pressure. Using phase noise measurement above threshold, it has been shown that the short-term linewidth of mechanical oscillations is fundamentally broadened, limited by thermal equipartition of energy.

Temporal behavior of radiation-pressure-induced RF oscillation of an optical micro-cavity phonon mode

We analyze experimentally and theoretically mechanical oscillation at RF frequency within an optical cavity stimulated by the pressure of circulating optical radiation. Oscillations and chaos were observed in output power.

Signature of Noise Mechanisms in the Linewidth of Self-Sustained Optomechanical Oscillations

We study the linewidth-noise relation in a self-sustained radiation-pressure-driven optomechanical oscillator. The experimental outcomes demonstrate that at room temperature Brownian noise is the dominant noise mechanism in this oscillator.

Oscillation linewidth and brownian noise in a radiation-pressure-driven opto-mechanical oscillator

For the first time we have studied the linewidth of mechanical oscillations in a radiation-pressure-driven microtoroid opto-mechanical oscillator and we demonstrate that Brownian noise is the dominant noise mechanism in this oscillator.

Characterization and scanning probe spectroscopy of radiation-pressure induced mechanical oscillation of a microcavity

Microcavities can enter a regime where radiation pressure causes oscillation of mechanical cavity eigenmodes. We present a detailed experimental and theoretical understanding of this effect, and report direct scanning probe spectroscopy of the micro-mechanical modes.