RESUMO
We demonstrate a microfabricated optomechanical accelerometer that is capable of percent-level accuracy without external calibration. To achieve this capability, we use a mechanical model of the device behavior that can be characterized by the thermal noise response along with an optical frequency comb readout method that enables high sensitivity, high bandwidth, high dynamic range, and SI-traceable displacement measurements. The resulting intrinsic accuracy was evaluated over a wide frequency range by comparing to a primary vibration calibration system and local gravity. The average agreement was found to be 2.1 % for the calibration system between 0.1 kHz and 15 kHz and better than 0.2 % for the static acceleration. This capability has the potential to replace costly external calibrations and improve the accuracy of inertial guidance systems and remotely deployed accelerometers. Due to the fundamental nature of the intrinsic accuracy approach, it could be extended to other optomechanical transducers, including force and pressure sensors.
RESUMO
Direct digital synthesis in concert with an electro-optic phase modulator was employed to generate optical frequency combs with tooth spacings as low as 100 Hz. These combs were utilized to probe electromagnetically induced transparency (EIT) and hyperfine pumping in potassium vapor cells. Long-term coherent averaging was demonstrated with performance similar to that achieved with a vastly more expensive arbitrary waveform generator. From the potassium EIT transition we were able to determine the ground state hyperfine splitting with a fit uncertainty of 80 Hz. Importantly, because of the mutual coherence between the control and probe beams, which originate from a single laser, features with linewidths several orders-of-magnitude narrower than the laser linewidth could be observed in a multiplexed fashion. This approach removes the need for slow scanning of a traditional cw laser or mode-locked-laser-based optical frequency comb.