Imaging of relaxation times and microwave field strength in a microfabricated vapor cell

Abstract

We present a new characterisation technique for atomic vapor cells, combining time-domain measurements with absorption imaging to obtain spatially resolved information on decay times, atomic diffusion and coherent dynamics. The technique is used to characterise a 5 mm diameter, 2 mm thick microfabricated Rb vapor cell, with N2 buffer gas, placed inside a microwave cavity. Time-domain Franzen and Ramsey measurements are used to produce high-resolution images of the population (T1) and coherence (T2) lifetimes in the cell, while Rabi measurements yield images of the σ−, π and σ+ components of the applied microwave magnetic field. For a cell temperature of 90• C, the T1 times across the cell centre are found to be a roughly uniform 265 µs, while the T2 times peak at around 350 µs. We observe a 'skin' of reduced T1 and T2 times around the edge of the cell due to the depolarisation of Rb after collisions with the silicon cell walls. Our observations suggest that these collisions are far from being 100% depolarising, consistent with earlier observations made with Na and glass walls. Images of the microwave magnetic field reveal regions of optimal field homogeneity, and thus coherence. Our technique is useful for vapor cell characterisation in atomic clocks, atomic sensors, and quantum information experiments.

Chip-scale atomic devices

“…Spatially resolved measurements of both transverse and longitudinal polarization in a microfabricated cell inside a microwave cavity were carried out. 276 In these pulsed measurements, the atoms are first optically pumped into a single hyperfine level and the population of the depumped level is measured some time later using a probe pulse. A spatially resolved measurement of this level population as a function of time results in a transverse image of the relaxation time throughout the cell, as shown in Fig.…”

Subwavelength microwave electric-field imaging using Rydberg atoms inside atomic vapor cells

“…Even in the field of magnetometry, where vapor cell magnetometers have played a central part [13], absorption imaging for vapor cell MW magnetometry has only been recently reported [14,15]. Many of the technical issues of imaging a MW magnetic field as opposed to an electric field with a vapor cell are different.…”

Aging studies on micro-fabricated alkali buffer-gas cells for miniature atomic clocks

“…V C 2015 AIP Publishing LLC. Micro-fabricated alkali-atom vapor cells with volumes of few mm 3 are of interest for applications in instruments such as miniature atomic magnetometers, 1 gyroscopes, 2 imaging of microwave fields, 3 and atomic clocks. 4 Particular applications like Chip Scale Atomic Clocks 5 (CSAC) based on Coherent Population Trapping (CPT) 6 were first reported by NIST.…”