Syamsundar De
Published: 2015
Total Pages: 0
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Coherent sources emitting two optical frequencies with a widely tunable frequency difference lying in the radio-frequency range and having a high degree of correlation between their fluctuations can be useful for numerous applications such as microwave photonics, ultra-stable atomic clocks, atom manipulation and probing, metrology, etc. Dual-frequency lasers, which emit two orthogonal linearly polarized modes with a frequency difference lying in the radio-frequency range, have huge potentials for the above mentioned applications. We compare the characteristics of such dual-frequency oscillation in lasers based on either semiconductor (VECSEL: vertical-external-cavity surface-emitting laser) or solid-state active media (mainly Nd3+, or Er3+ doped crystalline host). Apart from the obvious difference between the gain mechanisms in semiconductor and solid-state laser media, the dual-frequency VECSEL and the dual-frequency Nd:YAG laser exhibit different dynamical behaviors. The dual-frequency VECSELs exhibit relaxation oscillation free class-A dynamics as the photon lifetime inside the cavity is longer than the population inversion lifetime. On the contrary, the dual-frequency Nd:YAG lasers obey class-B dynamics linked with the fact that the photon lifetime inside the cavity is shorter than the population inversion lifetime, leading to the existence of relaxation oscillations. In this thesis, we figure out how the laser dynamics, in addition to the nonlinear coupling between the two laser modes, governs different noise phenomena in dual-frequency lasers. In particular, we demonstrate, both experimentally and theoretically, the influence of the laser dynamics and the nonlinear coupling between the two modes on the laser noise, by analyzing the spectral properties of the different noises (intensity, phase) and their correlation in a class-A dual-frequency VECSEL (vertical-external-cavity surface emitting laser) and a class-B dual-frequency Nd:YAG laser. Moreover, the noise correlation results are interpreted in terms of the linear response of two coupled damped oscillators.