P.K. Majumder

A frequency stabilization method for diode lasers utilizing low-field Faraday polarimetry

We present a method of diode laser frequency stabilization based on the Faraday rotation of linearly polarized light passing through an atomic sample in the presence of a very modest (1mT) magnetic field. Near the zero crossing of this spectroscopic feature, an optical system capable of very precise polarimetry detects and corrects for very small frequency fluctuations via a feedback system, which keeps the rotation signal at zero. In our application, we have demonstrated robust frequency stabilization over time scales from 10ms to 1h at the 1MHz level or below. We utilize this technique to lock our laser to a “forbidden” M1∕E2 transition in thallium at 1283nm, for which saturated absorption techniques are not straightforward. This technique has broad applicability to spectroscopy of various atomic systems as we also demonstrate using a Rb cell and a 780nm diode laser.

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

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.

High‐precision measurements of atomic parity nonconservation in lead and thallium

Atomic parity nonconservative experiments in a number of elements have now achieved the level of precision necessary for significant tests of the physics of and beyond the standard model of electroweak interactions. In our laboratory, parity, nonconserving (PNC) optical rotation has recently been measured in both atomic lead and thallium at the 1% level of precision. The prospect of equally precise calculations of thallium atomic structure make this element an excellent candidate for a new low‐energy test of electroweak physics. By studying hyperfine differences in thallium PNC, this experiment is also sensitive to nuclear spin dependent (anapole moment) effects at the level predicted by several models.