Optical rotation in excess of 100 rad generated by Rb vapor in a multipass cell

Abstract

Paramagnetic Faraday rotation is a powerful technique for atom sensing widely used in quantum nondemolition measurements, fundamental symmetry tests, and other precision measurements. We demonstrate the use of a multipass optical cell for Faraday rotation spectroscopy and observe polarization rotation in excess of 100 rad from spin-polarized Rb vapor. Unlike optical cavities, multipass cells have a deterministic number of light passes and can be used to measure large optical rotations. We also observe a tenfold suppression of transverse spin relaxation when Rb atoms are placed in a coherent superposition state immune to spin-exchange collisions.

Observation of Optical Chemical Shift by Precision Nuclear Spin Optical Rotation Measurements and Calculations

“…However, the signal-to-noise ratio (SNR) of NSOR detection has been poor in the first experiments utilizing low-field CW NMR [4] and in high-field pulsed experiments [6,7]. NSOR differences between the same nuclei in different molecular positions have not been clearly observed [7].Here we use a multi-pass optical cell [8,9] to measure proton NSOR with an SNR greater than 15 after 1000 seconds of integration and perform systematic NSOR measurements on organic liquids with absolute uncertainty of 5%. Contrary to recent report [7], we find that the NSOR signals do not scale with the Verdet constant V of the liquid since the hyperfine interaction between electrons and nuclei is influenced by the chemical environment.…”

Subfemtotesla Scalar Atomic Magnetometry Using Multipass Cells

“…A key parameter for measurements of spin-projection noise is the optical depth on resonance OD = σ 0 nl, where σ 0 is probe laser absorption cross-section on resonance and l is the path length of the probe beam through the atomic vapor [23]. We have developed multi-pass optical cells with mirrors internal to the alkali-metal vapor cell to increase l by two orders of magnitude [16]. Compared to optical cavities, multi-pass cells have a much larger interaction volume and allow direct recording of large optical rotations.…”

“…The best directly measured scalar magnetometer sensitivity is equal 7 fT/Hz 1/2 with a measurement volume of 1.5 cm 3 [12], while estimates of fundamental sensitivity per unit measurement volume for various types of scalar alkali-metal magnetometers range from several fT cm 3/2 /Hz 1/2 [13, 14] to about 1 fT cm 3/2 /Hz 1/2 [12]. Here we describe a new type of scalar atomic magnetometer using multi-pass vapor cells [15,16] and operating in a pulsed pump-probe mode [17] to achieve magnetic field sensitivity of 0.54 fT/Hz 1/2 with a measurement volume of 0.66 cm 3 in each multi-pass cell. The magnetometer sensitivity approaches, for the first time, the fundamental limit set by Rb-Rb collisions.…”

“…We measure the atom density n from the transverse relaxation T 2 at low polarization, which is dominated by spin-exchange collisions with a known cross-section [16]. The number of atoms participating in the measurement at any given time N = nV b is determined from the area of Faraday rotation power spectral density for unpolar- ized atoms [24].…”

“…Figure 1(c) shows a typical record of the optical rotation signal during one of the probe pulses. We fit the data using the equation [16]:…”