Rb D2 Transitions Research Articles

Portable Frequency Stabilized Lasers for Quantum Technologies Using Digital Techniques

Quantum atomic technologies such as optical clocks and atom interferometers have demonstrated their potential in laboratory settings, however their widespread deployment for real-world applications requires significant improvement in their Size, Weight, Power and Cost (SWaP-C). We have fabricated compact laser avionics suitable for laser cooling and spectroscopy applications. The system employs a commercial laser diode, fibre-coupled optics, current and temperature controllers, analogue-to-digital converters, all-digital signal processing, and operates on a single 5V power supply. Using these components, a 780nm laser has been stabilised to the Rb D2 transition via FM spectroscopy, with a SWaP budget of 1 L, 300 g, less than 10W. Due to its modular design and digital re-programmability, the low-SWaP-C system developed here can be applied to devices across the quantum technology sector.

Effects of neighboring transitions on the mechanisms of electromagnetically induced absorption and transparency in an open degenerate multilevel system

In this study, optical Bloch equations with and without neighboring hyperfine states near the degenerate two-level system (DTLS) in the challenging case of ^{85}Rb D2 transition, which involves the Doppler broadening effect, are solved. The calculated spectra agree well with the experimental results obtained based on the coupling-probe scheme with orthogonal linear polarizations of the coupling and probe fields. The mechanisms of electromagnetically induced absorption (electromagnetically induced transparency) for the open F_g=3 rightarrow F_e=2 and 3 transitions (open F_g=2 rightarrow F_e=2 and 3 transitions) are determined to be the effect of the strong closed F_g=3 rightarrow F_e=4 transition line (strong closed F_g=2 rightarrow F_e=1 transition line); this finding is based on a comparison between the calculated absorption profiles of the DTLS without neighboring states and those of all levels with neighboring states, depending on the coupling and probe power ratios. Furthermore, based on the aforementioned comparison, the crucial factors that enhance or reduce the coherence effects and lead to the transformation between electromagnetically induced absorption and electromagnetically induced transparency, are (1) the power ratios between the coupling and probe beams, (2) the openness of the excited state, and (3) effects of the neighboring states due to Doppler broadening in a real atomic system.

Doppler narrowing, Zeeman and laser beam-shape effects in Λ-type electromagnetically induced transparency on the 85Rb D2 line in a vapor cell

We study Λ-type Electromagnetically Induced Transparency (EIT) on the Rb D2 transition in a buffer-gas-free thermal vapor cell without anti-relaxation coating. Experimental data show well-resolved features due to velocity-selective optical pumping and one EIT resonance. The Zeeman splitting of the EIT line in magnetic fields up to 12 Gauss is investigated. One Zeeman component is free of the first-order shift and its second-order shift agrees well with theory. The full width at half maximum (FWHM) of this magnetic-field-insensitive EIT resonance is reduced due to Doppler narrowing, scales linearly in Rabi frequency over the range studied, and reaches about 100 kHz at the lowest powers. These observations agree with an analytic model for a Doppler-broadened medium developed in (Javan et al 2002 Phys. Rev. A 66 013805; Lee et al 2003 Appl. Phys. B, Lasers Opt. (Germany) B 76, 33–9; Taichenachev et al 2000 JETP Lett. 72, 119). Numerical simulation using the Lindblad equation reveals that the transverse laser intensity distribution and two Λ-EIT systems must be included to fully account for the measured line width and line shape of the signals. Ground-state decoherence, caused by effects that include residual optical frequency fluctuations, atom-wall and trace-gas collisions, is discussed.

Optical frequency reference stabilized to Rb D2 transition controlled by FPGA lock-in module

espanolLa modulacion y demodulacion lock-in es utilizada con frecuencia para la estabilizacion de la longitud de onda de emision de un laser sintonizable en laboratorios de metrologia, espectroscopia, fisica atomica y optica cuantica. En particular, la estabilizacion a una transicion atomica particular es utilizada para generar patrones de frecuencia optica de referencia. En este trabajo se presenta el desarrollo de un modulo de estabilizacion con tecnologia de electronica programable FPGA (del ingles, Field Programmable Gate Array) que permite realizar la modulacion a frecuencia f y demodulacion lock-in en frecuencias f y 3f. El modulo es economico, versatil y se puede controlar remotamente usando una plataforma de Software Libre. Se probo el desempeno del sistema estabilizando un laser sintonizable por cavidad externa (ECDL, del ingles External Cavity Diode Laser) a una de las transiciones hiperfinas del Rubidio (Rb), logrando una desviacion estandar en la frecuencia optica del orden de los 100 kHz, equivalentes a una estabilidad 2.6 10-10. EnglishLock-in measurement is frequently used for tunable laser wavelength stabilization in metrology, spectroscopy atomic physics and quantum optics labs. In particular, wavelength stabilization to atomic transitions is used to build optical frequency references. In this work we present the development of a stabilization module build using FPGA (Field Programmable Gate Array) technology for modulating at f frequency and lock-in demodulating on f and 3f frequencies. The module is economic, versatile and can be remotely controlled using a Free Software platform. We tested the system performance stabilizing a tunable External Cavity Diode Laser (ECDL) to a Rubidium (Rb) hyperfine transition, achieving an optical frequency standard deviation of 100 kHz, equivalent to an stability of 2.6 10-10.

An artificial Rb atom in a semiconductor with lifetime-limited linewidth

We report results important for the creation of a best-of-both-worlds quantum hybrid system consisting of a solid-state source of single photons and an atomic ensemble as quantum memory. We generate single photons from a GaAs quantum dot (QD) frequency-matched to the Rb D2-transitions and then use the Rb transitions to analyze spectrally the quantum dot photons. We demonstrate lifetime-limited QD linewidths (1.48 GHz) with both resonant and non-resonant excitation. The QD resonance fluorescence in the low power regime is dominated by Rayleigh scattering, a route to match quantum dot and Rb atom linewidths and to shape the temporal wave packet of the QD photons. Noise in the solid-state environment is relatively benign: there is a blinking of the resonance fluorescence at MHz rates but negligible upper state dephasing of the QD transition. We therefore establish a close-to-ideal solid-state source of single photons at a key wavelength for quantum technologies.

Double EIT and enhanced EIT signal in a combination of Λ- and V-type system of Rb-D2 transition

We report the experimental observations of double EIT and enhanced EIT signal in a combination of Λ- and V-type multi-level system of the D2 transition of 85Rb atoms interacting with three laser fields. The EIT formation under a Λ-type and V-type systems is also observed separately. It is found that the EIT width in a V-type system becomes narrower than the Λ-type system. Also the effect of frequency detuning of the control laser on the probe absorption profile is studied in presence of Λ- and V-type EIT systems.

Theoretical study of electromagnetically induced transparency in a five-level atom and application to Doppler-broadened and Doppler-free Rb atoms

We report theoretical studies of a Λ-type five-level atomic system. The density matrix equations are set up and solved numerically to obtain the probe absorption line shape of Rb D2 transitions for cold (Doppler-free) and room temperature (Doppler-broadened) atoms. Simulated spectra for Doppler-broadened systems lead to four velocity-selective dips along with an electromagnetic induced transparency (EIT) peak as observed earlier from the co-propagating pump–probe spectroscopy of Rb D2 transitions. Effects of pump power and spontaneous decay rate from the upper levels on the simulated spectra are also studied. For cold atoms a very pronounced EIT peak is observed when the pump frequency is on resonance with one allowed transition. We find that lower pump power leads to a much sharper EIT signal in this case. A simulated dispersion curve shows a rapid variation of the refractive index that may lead to a sharp reduction of the group velocity of photons.

Resonant Voigt-effect spectrum of the rubidium D^2 transition

We investigated the resonant magneto-optic spectra of the Rb D2 transition in the Voigt configuration (transverse magnetic field). To resolve the hyperfine structure of the Voigt-effect spectrum, we used a tunable single-mode GaAlAs diode laser as a light source. Elliptically polarized light with a small ellipticity was incident upon a Rb vapor cell placed in a magnetic field. The polarization change caused by magnetically induced optical anisotropy was detected by use of a birefringent prism placed behind the vapor cell. The Voigt-effect line profiles were measured for various degrees of light ellipticity and analyzer offset angle. The measured profiles were compared with the theoretical expression.