Squeezed vacuum phase control at 2 µm.

We demonstrate phase control for vacuum-squeezed light at a 2 µm wavelength, which is a necessary technology for proposed future gravitational wave observatories. The control scheme allowed examination of noise behavior at frequencies below 1 kHz and indicated that squeezing below this frequency was limited by dark noise and scattered light. We directly measure 3.9±0.2 dB of squeezing from 2 kHz to 80 kHz and 14.2±0.3 dB of antisqueezing relative to the shot noise level. The observed maximum level of squeezing is currently limited by photodetector quantum efficiency and laser instabilities at this new wavelength for squeezed light. Accounting for all losses, we conclude the generation of 11.3 dB of squeezing at the optical parametric oscillator.

Optomechanical design and construction of a vacuum-compatible optical parametric oscillator for generation of squeezed light.

With the recent detection of gravitational waves, non-classical light sources are likely to become an essential element of future detectors engaged in gravitational wave astronomy and cosmology. Operating a squeezed light source under high vacuum has the advantages of reducing optical losses and phase noise compared to techniques where the squeezed light is introduced from outside the vacuum. This will ultimately provide enhanced sensitivity for modern interferometric gravitational wave detectors that will soon become limited by quantum noise across much of the detection bandwidth. Here we describe the optomechanical design choices and construction techniques of a near monolithic glass optical parametric oscillator that has been operated under a vacuum of 10(-6) mbar. The optical parametric oscillator described here has been shown to produce 8.6 dB of quadrature squeezed light in the audio frequency band down to 10 Hz. This performance has been maintained for periods of around an hour and the system has been under vacuum continuously for several months without a degradation of this performance.

Thermo-optic locking of a semiconductor laser to a microcavity resonance.

We experimentally demonstrate thermo-optic locking of a semiconductor laser to an integrated toroidal optical microcavity. The lock is maintained for time periods exceeding twelve hours, without requiring any electronic control systems. Fast control is achieved by optical feedback induced by scattering centers within the microcavity, with thermal locking due to optical heating maintaining constructive interference between the cavity and the laser. Furthermore, the optical feedback acts to narrow the laser linewidth, with ultra high quality microtoroid resonances offering the potential for ultralow linewidth on-chip lasers.

Backscatter absorption gas imaging: a new technique for gas visualization.

This paper presents a new laser-based method of gas detection that permits real-time television images of gases to be produced. The principle of this technique [which is called backscatter absorption gas imaging (BAGI)] and the operation of two instruments used to implement it are described. These instruments use 5-W and 20-W CO(2) lasers to achieve gas imaging at ranges of approximately 30 and 125 m, respectively. Derivations of relevant BAGI signal equations that can be used to predict the performance of a gas imager are provided. The predictions of this model and the measured range performance of an extended-range gas imager are compared. Finally, the results of gas sensitivity measurements and imaging tests on flowing gases are presented. These can be used to generate a realistic estimate of the BAGI sensitivity expected in detecting leaks of many different vapors.