Pulsed Laser Interferometry with Sub-Picometer Resolution Using Quadrature Detection

Abstract

Femtosecond pulsed laser interferometry has previously been used to measure picometer-level displacements on sub-nanosecond time scales. In this paper, we experimentally examine its achievable displacement resolution, as well as the relationship between the laser’s optical spectrum and the interferometer’s sensitivity. The resulting broadband displacement noise and noise floor of the pulsed laser Michelson interferometer are equivalent to that achieved with a stabilized continuous wave HeNe laser, where values of 1.2 nm RMS and 22.11 fm /rt-Hz have been demonstrated. It was also found that the interferometer’s sensitivity is set by the wavelength found at the peak intensity within the pulsed laser’s spectrum, even when the spectrum is modified by a bandpass filter. These results will be used for time-resolved displacement metrology with picosecond temporal resolution in the future.