Response of microchip solid-state laser to external frequency-shifted feedback and its applications

Abstract

The response of the microchip solid-state Nd:YAG laser, which is subjected to external frequency-shifted feedback, is experimentally and theoretically analysed. The continuous weak response of the laser to the phase and amplitude of the feedback light is achieved by controlling the feedback power level, and this system can be used to achieve contact-free measurement of displacement, vibration, liquid evaporation and thermal expansion with nanometre accuracy in common room conditions without precise environmental control. Furthermore, a strong response, including chaotic harmonic and parametric oscillation, is observed, and the spectrum of this response, as examined by a frequency-stabilised Nd:YAG laser, indicates laser spectral linewidth broadening.

Nonlinear modification of the laser noise power spectrum induced by frequency-shifted optical feedback

“…10 17 times weaker than the laser intra-cavity power) has been detected [6]. When the optical feedback becomes stronger, nonlinearities appear in the laser dynamics [15,16]. They can cause the apparition of chaos, bi-stability and hysteresis phenomenon with the tuning (back and forth) of the frequency shift of the optical feedback [17].…”

“…where I and N are respectively the laser intensity (photon unit) and the population inversion (atom unit In the presence of a strong optical feedback, the laser intrinsic dynamics and in particular the relaxation oscillation frequency is modified and will depend on the modulation conditions ( to induce non-linear dynamical behaviors (which give rise to the generation of harmonic and parametric dynamical frequencies) in the laser output power modulation [13,15,16]. In contrast, the "weak feedback" regime corresponds to the situation where the modulation frequency is far away from the By comparison with the work made in [15,16], which is focused on the study of the signal power spectrum, the present work analyzes how the noise power spectrum of the laser is modified…”

“…In contrast, the "weak feedback" regime corresponds to the situation where the modulation frequency is far away from the By comparison with the work made in [15,16], which is focused on the study of the signal power spectrum, the present work analyzes how the noise power spectrum of the laser is modified…”

Development of an Abbe Error Free Micro Coordinate Measuring Machine

“…The metrological system consists of three laser heterodyne interferometers, developed by Zhang et al [12,13] to measure the movements of the 3D stage in X, Y and Z directions, respectively. The reflectors of the interferometers are plane mirrors.…”

“…In this micro CMM, movements in X, Y and Z directions are measured by three Nd:YAG laser feedback interferometers developed by Zhang et al [12,13]. Frequencies of all three lasers are stabilized.…”