Narrow band noise rejection technique for laser frequency and length standards: application to frequency stabilization to I2 lines near dissociation limit at 501.7 nm

Abstract

An opto-electronic device for the stabilization of laser beam intensity in a narrow frequency band based on a numeric corrector driving the radio-frequency signal of an acousto-optic modulator is applied to improve the signal-to-noise ratio of the detected signal in saturation spectroscopy of iodine in a cell at 501.7 nm, both in the FM spectroscopy technique and in the transfer modulation technique. In the latter case, a 30 dB rejection of the amplitude noise of the probe beam is achieved and, when the laser frequency is locked to the saturation signal, the enhancement of the sensitivity of the frequency jitter detection is demonstrated in a frequency band extending up to 1 kHz. For the long term stabilization the laser is locked to a narrow line detected in a low pressure cell. A relative Allan deviation of about 10−13 is found for 1 s integration time and a deviation of 10−14 is reached for 500 s. Linewidths smaller than 40 kHz (FWHM) are also demonstrated at low saturating power for hyperfine components of the transition R(26)62-0 at 501.7 nm.