Physique des Lasers

Master / M2Première partie du cours de physique des lasers du M2 'Lasers et Matière'. A partir d'une approche semi-classique de l'interaction matière-rayonnement, on dérive les équations du laser monomode. On étudie ensuite le comportement des lasers à élargissement homogène et inhomogène. Ensuite, on étudie les régimes transitoires et déclenchés de ces lasers, avant d'étudier leurs bruits d'intensité et de fréquence

Intensity and phase noise correlations in a dual-frequency VECSEL operating at telecom wavelength

The amplitude and phase noises of a dual-frequency vertical-external-cavity surface-emitting laser (DF-VECSEL) operating at telecom wavelength are theoretically and experimentally investigated in detail. In particular, the spectral behavior of the correlation between the intensity noises of the two modes of the DF-VECSEL is measured. Moreover, the correlation between the phase noise of the radio-frequency (RF) beatnote generated by optical mixing of the two laser modes with the intensity noises of the two modes is investigated. All these spectral behaviors of noise correlations are analyzed for two different values of the nonlinear coupling between the laser modes. We find that to describe the spectral behavior of noise correlations between the laser modes, it is of utmost importance to have a precise knowledge about the spectral behavior of the pump noise, which is the dominant source of noise in the frequency range of our interest (10 kHz to 35 MHz). Moreover, it is found that the noise correlation also depends on how the spatially separated laser modes of the DF-VECSEL intercept the noise from a multi-mode fiber-coupled laser diode used for pumping both the laser modes. To this aim, a specific experiment is reported, which aims at measuring the correlations between different spatial regions of the pump beam. The experimental results are in excellent agreement with a theoretical model based on modified rate equations

Frequency stabilization at the kilohertz level of a continuous intracavity frequency-doubled singly resonant optical parametric oscillator

A continuous intracavity frequency-doubled singly resonant optical parametric oscillator (OPO) is stabilized to the side of the transmission peak of a medium finesse Fabry–Perot cavity. The narrow bandwidth of the frequency noise of this OPO allows this simple scheme to lead to a stability of a few kilohertz with respect to the locking etalon. The system, operating in the visible domain, remains locked for more than 1h

Interacting double dark resonances in a hot atomic vapor of helium

We experimentally and theoretically study two different tripod configurations using metastable helium ($^4$He*), with the probe field polarization perpendicular and parallel to the quantization axis, defined by an applied weak magnetic field. In the first case, the two dark resonances interact incoherently and merge together into a single EIT peak with increasing coupling power. In the second case, we observe destructive interference between the two dark resonances inducing an extra absorption peak at the line center.Comment: 7 pages, 7 figure