AC Stark-shift in CPT-based Cs miniature atomic clocks

We report on studies on the light-shift in caesium miniature atomic clocks based on coherent population trapping (CPT) using a micro-fabricated buffer-gas cell (MEMS cell). The CPT signal is observed on the Cs D1-line by coupling the two hyperfine ground-state Zeeman sublevels involved in the clock transition to a common excited state, using two coherent electromagnetic fields. These light fields are created with a distributed feedback laser and an electro-optical modulator. We study the light-shift phenomena at different cell temperatures and laser wavelengths around 894.6nm. By adjusting the cell temperature, conditions are identified where a miniature CPT atomic clock can be operated with simultaneously low temperature coefficient and suppressed light-shift. The impact of the light-shift on the clock frequency stability is evaluated. These results are relevant for improving the long-term frequency stability of CPT-based Cs vapour-cell clock

Observation of polarization quantum noise of laser radiation in Rb vapor cell

We present experimental study of polarization quantum noise of laser radiation passed through optically think vapor of Rb87. We observe a step-like noise spectrum. We discuss various factor which may result in such noise spectrum and prevent observation of squeezing of quantum fluctuations predicted in Matsko et al. PRA 63, 043814 (2001).Comment: 4 pages, 5 figures. Translated from Russian by I. Novikov

Frequency-stabilised laser reference system for water vapour spectroscopy and sensing applications

To acheive the requirements of DIAL instrument, a frequency detection unit (FDU) was realised for water vapour spectroscopy. For this we have developed and realised an ECDL, which can be adjusted at 935 nm or at 942 nm, a region also considered as possible for the WALES (water vapour lidar experiment in space) transmitter. The second main subsystem of the FDU, a frequency reference unit (FRU), grants short- and long-term frequency stabilities of the ISL. Offset-locking with frequency differences up to 19 GHz has been experimentally demonstrated with the proposed techniqu

Diode laser frequency stabilisation for water-vapour differential absorption sensing

We describe a low-power continuous-wave laser system for water-vapour sensing applications in the 935-nm region. The system is based on extended-cavity diode lasers and distributed-feedback lasers and delivers four single-mode frequency-stabilised optical signals. Three lasers are locked to three water-vapour absorption lines of different strengths, whereas the fourth lies outside any absorption line. On-line stabilisation is performed by wavelength-modulation spectroscopy using compact water-vapour reference cells. An offset-locking technique implemented around an electrical filter is applied for the stabilisation of the off-line slave laser to an on-line master laser at a frequency detuning of 18.8 GHz. Stabilities in the order of 15 MHz over one day were observed for the strongest lines, at the detection limit of the measurement instrumentation. The developed techniques and schemes can be applied to other wavelength ranges and molecular species. Differential absorption lidar instrumentation can in particular benefit from such a system when the stabilised lasers serve as injection seeders to pulsed power oscillators. © Springer-Verlag 2006

A cold-atom Ramsey clock with a low volume physics package

We demonstrate a Ramsey-type microwave clock interrogating the 6.835 GHz ground-state transition in cold 87Rb atoms loaded from a grating magneto-optical trap (GMOT) enclosed in an additively manufactured loop-gap resonator microwave cavity. A short-term stability of 1.5×10−11 τ−1/2 is demonstrated, in reasonable agreement with predictions from the signal-to-noise ratio of the measured Ramsey fringes. The cavity-grating package has a volume of ≈67 cm3, ensuring an inherently compact system while the use of a GMOT drastically simplifies the optical requirements for laser cooled atoms. This work is another step towards the realisation of highly compact portable cold-atom frequency standards

MICROFABRICATION AND PACKAGING OF A RUBIDIUM VAPOR CELL AS A PLASMA LIGHT SOURCE FOR MEMS ATOMIC CLOCKS

We report on the micro-fabrication and characterization of a chip-scale plasma light source based on a Rubidium (Rb) vapor cell. The Rb plasma light source is intended for use as an integrated optical pump-light source in miniature double-resonance Rb atomic clocks [1, 5]. The RF plasma is capacitively coupled using external electrodes, and the light source is impedance matched to the source for frequencies between 1 and 36 MHz. Rb vapor cells have been previously developed as reference cells for atomic clocks but not as light sources. This is the first reported Rb plasma emitted from a chip-scale device. Stable light emission is observed for over 18 days

Low-Power Chip-Scale Rubidium Plasma Light Source for Miniature Atomic Clocks

We present the development, testing and characterization of a low-power chip-scale Rubidium (Rb) plasma light source designed to serve for optical pumping in miniature atomic clocks. The technique used is electrodeless capacitively coupled plasma (CCP) discharge, driven in a microfabricated Rb vapor cell. The device is electrically driven at frequencies between 1 and 36 MHz to emit 140 μW of stable optical power while coupling < 6 mW of electrical power to the discharge cell. To our knowledge this is the first reported Rb plasma emitted from a chip-scale device