Frequency stabilization of diode lasers using a narrow bandwidth optical resonator and possible applications for ultracold atoms experiments

Seminar

Speaker: Chi Zhang
When: Apr. 30 2015 09:00
Where: Erwin Schrödinger Saal

This thesis describes the frequency stabilization of external-cavity diode lasers with a high-finesse optical cavity by the Pound Drever Hall technique, as well as the potential applications of optical cavities and the stabilized lasers in ultracold atomic experiments. First, a laser was locked onto a cavity, which was in turn characterized by the locked laser. Then the frequency fluctuations of the laser were estimated based on the cavity parameters and the measured transmission and reflection from the cavity. Furthermore, two lasers were locked on both sides of the cavity at neighboring modes. By improving the electric circuits of the locks, the linewidth of the beat note of the two lasers was reduced to less than 100Hz. Subsequently, an optical fiber was stabilized, by compensating the random phase shifts from the fiber by an acousto-optical-modulator, to transmit the stabilized lasers through the fiber to the future experiments without increasing frequency noise. In addition, two possible experimental schemes for ultracold fermionic atoms inside cavities are presented. The first one is to measure the antiferromagnetism correlations in the two-dimensional Hubbard model; via the cavity-induced Bragg scattering of an off-resonant laser, which is amplified significantly by the cavity. Since the scattering signal of a few atoms is already sufficient to be detected, this method can be used to determine the correlation length by probing a small amount of atoms, even if the temperature is not low enough to reach the global antiferromagnetic phase. The other scheme aims for the generation of a disordered optical lattice potential with cavities, where the cavities can select a series of standing waves with periodic frequencies but random amplitudes to form a stable disordered optical lattice.

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