Picosecond photorefractive diffraction in CdTe at 1 μm

Using a ps-transient grating technique the contribution of the ps-photorefractive effect to the first-order probe-beam diffraction signal has been studied in CdTe at 1 m investigating diffraction kinetics at different sample orientations in the thin grating regime. A fast photorefractive grating formation time during the pump pulses and a characteristic decay time of 600 ps, shorter than the free-carrier lifetime, have been observed.     

High-sensitivity atomic magnetometer unaffected by spin-exchange relaxation

Alkali-metal magnetometers compete with SQUID detectors as the most sensitive magnetic field sensors. Their sensitivity is limited by relaxation due to spin-exchange collisions. We demonstrate a K magnetometer in which spin-exchange relaxation is completely eliminated by operating at high K density and low magnetic field. Direct measurements of the signal-to-noise ratio give a magnetometer sensitivity of 10 fT Hz(-1/2), limited by magnetic noise produced by Johnson currents in the magnetic shields. We extend a previous theoretical analysis of spin exchange in low magnetic fields to arbitrary spin polarizations and estimate the shot-noise limit of the magnetometer to be 2x10(-18) T Hz(-1/2).     

New limit on Lorentz- and CPT-violating neutron spin interactions

We performed a search for neutron spin coupling to a Lorentz- and CPT-violating background field using a magnetometer with overlapping ensembles of K and 3He atoms. The comagnetometer is mounted on a rotary platform for frequent reversal of its orientation. We measure sidereal oscillations in the signal to search for anomalous spin coupling of extra-solar origin. We determine the equatorial components of the background field interacting with the neutron spin to be b?Xn=(0.1 ± 1.6) × 10?33 GeV and b?Yn=(2.5 ± 1.6) × 10?33 GeV, improving on the previous limit by a factor of 30. This measurement represents the highest energy resolution of any spin anisotropy experiment.     

Dynamics of two overlapping spin ensembles interacting by spin exchange

We describe linear and nonlinear dynamics of spin-polarized K and 3He ensembles interacting by spin exchange. The interactions are dominated by the imaginary part of the spin-exchange cross section and each spin species is primarily affected by the average magnetization of the other. Operating in a very low magnetic field we demonstrate novel dynamics when the electron and nuclear spin precession frequencies are nearly matched. We observe transverse damping as well as a dynamic instability of the 3He spins interacting with polarized K vapor. We also demonstrate operation as a self-compensating comagnetometer, useful for tests of CPT violation and other precision measurements.     

Nuclear spin gyroscope based on an atomic comagnetometer

We describe a nuclear spin gyroscope based on an alkali-metal-noble-gas comagnetometer. Optically pumped alkali-metal vapor is used to polarize the noble-gas atoms and detect their gyroscopic precession. Spin precession due to magnetic fields as well as their gradients and transients can be cancelled in this arrangement. The sensitivity is enhanced by using a high-density alkali-metal vapor in a spin-exchange relaxation free regime. With a K-3He comagnetometer we demonstrate rotation sensitivity of 5 x 10(-7) rad s(-1) Hz(-1/2), equivalent to a magnetic field sensitivity of 2.5 fT/Hz(1/2). The rotation signal can be increased by a factor of 10 using 21Ne with a smaller magnetic moment. The comagnetometer is also a promising tool in searches for anomalous spin couplings beyond the standard model.