A frequency stabilization technique for diode lasers based on frequency-shifted beams from an acousto-optic modulator

Abstract

We present a simple method for diode laser frequency stabilization that makes use of a Doppler-broadened vapor cell absorption signals of two frequency-shifted laser beams. Using second-order-diffracted, double-passed beams from an acousto-optic modulator, we achieve a frequency separation roughly equal to the Doppler half width. The differential transmission signals of the two beams provide an error signal with a very large linear feature, allowing frequency stabilization over a range of greater than 1 GHz by means of standard proportional-integral-derivative servo feedback to the piezoelectric control of the grating in our external cavity diode laser. We have applied this technique to two different diode laser systems, one used to lock to the 410 nm E1 transition in indium and another for locking to the M1/E2 transition in thallium at 1283 nm. In both cases the technique reduces frequency fluctuation to roughly 1 MHz over time scales from 10(-3) to 10(2) s.

Measurement of7p1/2-state hyperfine structure and7s1/2-Ranjit1, Kealhofer2, Vukasin3 et al. 2014Phys. Rev. ASelf Cite

“…This difference signal is the input to a standard servo circuit which steers the laser frequency via a voltage applied to the piezoelectric transducer (PZT) controlling the diffraction grating in the laser cavity. We find that this locking technique reduces the drift of the laser frequency to 1 MHz or less over time scales of several hours [18]. Fig.…”

“…The locking scheme is based on a method developed in our group [18,19]. Briefly, we pass the UV laser beam through an acousto-optic modulator (AOM), producing diffracted beams which are frequency shifted by ±250 MHz from the incident beam.…”

Opto-Electronics Review

“…A useful solution is an AOM in a double-pass configuration which doubles the frequency offset, widens the tuning bandwidth and, at the same time, significantly reduces beam pointing fluctuations [83]. Also, higher multi-pass schemes, odd [84] or even [85], high diffraction orders [86] or combinations thereof [87] can be employed to expand the range of frequency shifts.…”

Thallium 7plifetimes derived from experimental data andab initiocalculations of scalar polarizabilities

“…For both atomic systems, we have completed such two-step spectroscopy experiments in a vapor cell environment to study excited-state hyperfine structure and isotope shifts [30,31]. In these twostep experiments, we begin by locking the blue or UV laser to the first transition step, using a supplementary atomic vapor cell and technique developed recently [32]. We then overlap this laser beam with that of a second infrared laser and intersect both with our atomic beam using a transverse geometry.…”