Tunable and frequency-stabilized diode laser with a Doppler-free two-photon Zeeman lock

Abstract

We describe frequency locking of a diode laser to a two-photon transition of rubidium using the Zeeman modulation technique. We locked and tuned the laser frequency by modulating and shifting the two-photon transition frequency with ac and dc magnetic fields. We achieved a linewidth of 500 kHz and continuous tunability over 280 MHz with no laser frequency modulation.

Two-beam nonlinear Kerr effect to stabilize laser frequency with sub-Doppler resolution

“…We use the density matrix formalism for a closed two-level system to treat the interaction of the probe beam with this pump-modified medium. The χ (3) is obtained from the medium polarization expression [11]:…”

“…It can be interesting to generate dispersive sub-Doppler signals centered at hyperfine transitions to have an absolute frequency reference. Most of the techniques employed involve modulation with homodyne detection to generate dispersive lineshapes from the derivative of absorptive sub-Doppler lines, such as saturation absorption spectroscopy with frequency modulation [2] and two-photon absorption in the presence of ac magnetic field [3]. On the other hand, the use of modulation can limit the feedback linewidth [4] and should be avoided for some purposes [5].…”

“…We have called this technique ANGELLS [8], for Atomic Nonlinearly GEnerated Laser Lock Signal. Alkali vapors are very interesting nonlinear systems since the third-order susceptibility (χ (3) ) can be easily modified by changing the field amplitude or by finely tuning the laser frequency across the resonance [9]. The dependence of χ (3) with the detuning is the key element of the ANGELLS technique we have developed to lock the laser frequency with Doppler resolution [8].…”

“…Alkali vapors are very interesting nonlinear systems since the third-order susceptibility (χ (3) ) can be easily modified by changing the field amplitude or by finely tuning the laser frequency across the resonance [9]. The dependence of χ (3) with the detuning is the key element of the ANGELLS technique we have developed to lock the laser frequency with Doppler resolution [8]. Moreover, the χ (3) term can be drastically modified by the introduction of a second laser beam permitting sub-Doppler resolution.…”

Two-photon dichroic atomic vapor laser lock using electromagnetically induced transparency and absorption

“…Locking schemes using modulation of atomic resonances or light require demodulation to generate an error signal. Methods with one laser use fluorescence detection after a degenerate two-photon excitation with light [7], or atomic level modulation [8]. Methods with two lasers modulate the frequency of one laser to generate an error signal for the other when it is scanned over resonance [9][10][11].…”