University of Colorado

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

William R Milner

Jun Ye

Terry Brown

Colin J Kennedy

Eric G Oelker

Tobias Bothwell

John M Robinson

Dhruv Kedar

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

Growing community of inventors

Boulder, CO, United States of America

William R Milner