University of Colorado

Other

Government of the United States of America, As Represented by the Secretary of Commerce

Jun Ye

John L Hall

Long-Sheng Ma

Henry C Kapteyn

Margaret Mary Murnane

Scott A Diddams

Kevin D Moll

Robert K Shelton

Terry Brown

Colin J Kennedy

William R Milner

Tobias Bothwell

Michael J Thorpe

Eric G Oelker

John M Robinson

Dhruv Kedar

R Jason Jones

The frequency stability of an optical local oscillator is improved by locking a laser to a silicon Fabry-Perot cavity operating at a temperature near 124 K, where the coefficient of thermal expansion of silicon is near zero. The cavity is mounted inside a cryostat housed in a temperature-stabilized vacuum system that is surrounded by an isolating enclosure and supported by an active vibration platform. Laser light is steered with a superpolished mirror toward a superpolished focusing optic that couples the laser light into the cavity. Light reflected from the cavity is used to stabilize the laser via the Pound-Drever-Hall technique, while light transmitted through the cavity is used to stabilize the laser power. A resonant transimpedance amplifier allows the laser power to be reduced, which reduces heating of the cavity caused by residual absorption of the light.

Optical local oscillator for all-optical time scales, and associated timekeeping methods

Cavity enhanced spectroscopy efficiently couples a broadband optical frequency comb to a high finesse optical cavity inside which a sample test gas is placed. The output of the optical cavity is a multiplicity of channels of data resulting from the differential absorption of light at various of the comb frequencies. The device can operate in a ringdown mode or a non-ringdown enhanced absorption spectroscopy mode. Careful measurement and control of cavity dispersion and comb spacing are part of the coupling process. Several dispersive detection methods adapted to detecting the multiplicity of channels are provided.

Frequency comb cavity enhanced spectroscopy

Accurate and efficient synchronization of two pulsed radiation sources (e.g. iwo mode locked lasers) is accomplished in stages. Rough synchronization is accomplished by synchronizing (for example) the fundamental repetition rate of the two lasers. Fine synchronization is accomplished by synchronizing high harmonics of the two lasers. More accurate synchronization may be accomplished by adding more stages, by utilizing light out of a nonlinear laser in which the two beams are crossed, or by utilizing heterodyne beats of the two laser beams. A dc offset signal may added to the control signal generated by the synchronization stages.

Multistage synchronization of pulsed radiation sources

An ac technique for cavity ringdown spectroscopy permits 1&times;10 absorption sensitivity with microwatt light power. Two cavity modes are provided temporally out of phase such that when one mode is decaying, the other mode is rising. When one of the modes probes intra-cavity absorption of a sample gas, heterodyne detection between the two modes reveals dynamic time constants associated with the cavity and the cavity plus intra-cavity absorption. The system and method provides a quick comparison between on-resonance and off-resonance modes and enables sensitivities that approach the shot-noise limit.

Cavity ringdown spectroscopy system using differential heterodyne detection

A low-loss comb-generating optical cavity including an optical amplifier and a microwave-driven electro-optic modulator crystal, produces a comb of optical frequency sidebands having spectral lines equally spaced around the frequency of an input laser beam incident on the comb-generating cavity. The comb-generating cavity includes an input mirror movable along the beam propagation direction, and a fixed position output mirror located at time synchronous distances of both the input laser wavelength and modulation wavelength. The comb-generating cavity and its microwave driven modulator are in resonance with the input laser beam, and provide iterative or recirculating beam action that transfers the input optical frequency of the laser, sideband by sideband, to remote and precisely known comb frequencies offset from, and centered on, the input laser frequency. Optical parametric amplification within the comb-generating cavity extends the sideband or comb spectrum and sharpens the time domain impulse represented by the cavity circulating fields. A relatively short bandpass filter optical cavity receives the comb output of the comb-generating cavity and is made up of the fixed-position mirror and a third mirror movable along the beam propagation direction. Fine movement of the third mirror tunes the bandpass filter cavity, and preferentially couples out the power of one or more comb frequencies. An optional input optical cavity at the input side may increase efficiency. A self-oscillating configuration provides optical parametric oscillation.

Comb generating optical cavity that includes an optical amplifier and an optical modulator

Growing community of inventors

Louisville, CO, United States of America

Jun Ye