We report experimental observation of velocity-selective resonances in the Doppler-broadened probe absorption spectra of 85Rb and 87Rb D 2 transitions in the presence of a strong co-propagating pump laser locked to a frequency within the Doppler profile of the transition. The set of three dips having the separation of allowed hyperfine transitions move along the Doppler profile while the pump laser frequency is tuned. This indicates a resonance between the pump laser frequency and the velocity shifted probe laser frequency. © 2004 Elsevier B.V. All rights reserved.

BISWAJIT RAY

Physics

S CHAKRABARTI

A PRADHAN

A BANDYOPADHYAY

A RAY

N KAR

P N GHOSH

Fulltext

University of Calcutta (informally known as Calcutta University or CU) is a collegiate public state university located in Kolkata, West Bengal, India.&nbsp;Within India it is recognized as a &quot;Five-Star University&quot; and accredited &quot;A&quot; Grade by National Assessment and Accreditation Council.

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The University of Calcutta has secured the Fifth position among the Universities of India in the prestigious &quot;Indian University Ranking 2019&quot; list, released by the NIRF of the Ministry of Human Resource Development, Government of India.

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It was established on 24 January 1857, and was one of the first institutions in Asia to be established as a multidisciplinary and Western-style university. Its alumni and faculty include several heads of state, heads of government, social reformers, prominent artists, only academy award winner and Dirac medal winner in India, many Fellows of the Royal Society and five Nobel laureates as of 2019 which is highest in South Asia.

University Of Calcutta

Chemical Physics Letters

Atomic coherence resonances such as electromagnetically induced transparency (EIT) and electromagnetically induced absorption (EIA) signals are observed in a Doppler broadened multi-level system for the D2 line of 85Rb atoms in a vapour cell considering different types of atom-laser coupling schemes. Besides the coherence resonances, the nonlinear resonances like velocity selective optical pumping (VSOP) dips and velocity selective resonances (VSR) are also observed for the non-zero velocity selective groups of atoms. In the presence of pump, control and probe laser fields, we observe two EIT signals in a double Λ-type system and two EIA signals in a double V-type system. We are able to see the EIA signal for the non-zero velocity group of atoms when the pump laser is locked with an open transition by a small red detuning. We also report the experimental observation of simultaneous EIT and EIA signals in a (Λ+V)-type system. The effect of frequency tuning of the control laser is also studied in the presence of the frequency locked pump laser. A simple theoretical analysis explains the experimental results. © 2011 IOP Publishing Ltd.

Journal of Physics B: Atomic, Molecular and Optical Physics

Nonlinear resonances caused by coherent, optical pumping and saturating effects in the presence of three laser fields for the 85Rb-D 2 line

Atomic coherence resonances such as electromagnetically induced transparency (EIT) and electromagnetically induced absorption (EIA) signals are observed in a Doppler broadened multi-level system for the D-2 line of Rb-85 atoms in a vapour cell considering different types of atom-laser coupling schemes. Besides the coherence resonances, the nonlinear resonances like velocity selective optical pumping (VSOP) dips and velocity selective resonances (VSR) are also observed for the non-zero velocity selective groups of atoms. In the presence of pump, control and probe laser fields, we observe two EIT signals in a double Lambda-type system and two EIA signals in a double V-type system. We are able to see the EIA signal for the non-zero velocity group of atoms when the pump laser is locked with an open transition by a small red detuning. We also report the experimental observation of simultaneous EIT and EIA signals in a (Lambda + V)-type system. The effect of frequency tuning of the control laser is also studied in the presence of the frequency locked pump laser. A simple theoretical analysis explains the experimental results.

Nonlinear resonances caused by coherent, optical pumping and saturating effects in the presence of three laser fields for the Rb-85-D-2 line

Pump-probe double resonance spectroscopy of Rb D2 transitions are reported for co and counter propagating lasers with tunable frequencies. A perturbative analytical solution of the optical Bloch equations is derived for the five-level atomic system to reproduce the experimental results. The optical pumping effect has been taken into account in the theoretical model. Velocity selective peaks can be observed for all velocity groups of atoms by choosing the appropriate pump frequency. The peaks can be narrowed by varying the lower level hyperfine decay rate. © 2007 Elsevier B.V. All rights reserved.

Velocity dependent pump-probe spectroscopy for a five-level system: An application to Rb D2 transitions

It is shown that the pump-probe spectroscopy of Λ-type system for the D2 transition of 87Rb exhibits additional absorption enhancement peaks due to velocity selective optical pumping along with the electromagnetically induced transparency (EIT). The separation of these peaks is consistent with the hyperfine splitting of the upper levels. For 85Rb the peaks are not clearly discernible since the hyperfine splitting is much smaller. © 2005 IOP Publishing Ltd.

Velocity selective optical pumping effects and electromagnetically induced transparency for D2 transitions in rubidium

An inexpensive GaAlAs single mode semiconductor diode laser operating in the 822 nm wavelength region is frequency stabilised at the line centre of a transition in the (2,1,1) vibration-rotation band of water vapour. A balanced photodetector is used for recording to improve the signal/noise (S/N) ratio. The laser frequency is locked at the line centre by using a simple current-feedback servocircuit. A long-term laser frequency stability of ∼4 MHz is attained, which is more than a hundred-fold improvement over the performance provided by the free running semiconductor diode laser. The corresponding Allan-variance measurement reaches σ(τ) = 8.0 × 10-12 for an integration time of 100s. © IEE, 2004.

IEE Proceedings: Optoelectronics

Frequency stabilisation of a GaAIAs semiconductor diode laser to an absorption line of water vapour at 822 nm

A theoretical model based on rate equations of a four-level atom with a common ground level and three closely spaced upper levels interacting with a standing wave has been developed and solved numerically to simulate the saturated absorption spectrum of rubidium. Doppler-free and collision free Lamb dip Rb-D2 transitions were recorded by using an external cavity diode laser spectrometer operating at 780 nm. The simulated spectra could reproduce the observed spectrum very well. The value of Rabi-frequency and the saturation parameter could be evaluated. © 2004 Elsevier B.V. All rights reserved.

Line shape simulation and saturated absorption spectroscopic measurement of Rb-D2 transition

The line shape of a pair of Doppler-broadened closely spaced transitions sharing a common lower level and under the effect of a standing-wave monochromatic radiation field is studied. The eight steady-state optical Bloch equations are solved analytically to obtain the polarization by retaining terms up to the third power in the electric-field amplitude. The absorption coefficient derived for the standing-wave case consists of two Lamb dips for the two allowed transitions at 1 and 2 and a crossover resonance dip at the intermediate frequency c=(1+2)/2. The Lamp-dip peak frequencies show intensity-dependent shifts. Numerical computations are presented for different values of Rabi frequencies and relaxation linewidth parameters, which are small compared to the frequency difference =2-1. The computed line shape and frequency shift are compared with the observed results in the Balmer H line of hydrogen and the infrared Zeeman spectra of methane. © 1992 The American Physical Society.

Journal	Chemical Physics Letters
Publisher	-
ISSN	0009-2614
Open Access	Yes