Optical coherences and wavelength mismatch in ladder systems

Urvoy, Alban; Carr, C. W.; Ritter, Ralf; Adams, Charles S.; Weatherill, Kevin J.; Löw, Robert

doi:10.1088/0953-4075/46/24/245001

Cited by 44 publications

(30 citation statements)

References 39 publications

(57 reference statements)

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“…The two laser beams are focused to a waist of 40 µm and overlapped in a copropagating configuration. This results in a simple Lorentzian-like excitation spectrum, in contrast to the counterpropagating configuration [23][24][25] population shelving [26], the transmission signal of the 795 nm laser is roughly proportional to the population of the Rydberg state. The transmission of the 795 nm laser is monitored as a function of the detuning ∆ 477 , recording both directions of the frequency scan (from red to blue, and vice versa).…”

Section: A Rubidiummentioning

confidence: 99%

Charge-induced optical bistability in thermal Rydberg vapor

et al. 2016

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We investigate the phenomenon of optical bistability in a driven ensemble of Rydberg atoms. By performing two experiments with thermal vapors of rubidium and cesium, we are able to shed light onto the underlying interaction mechanisms causing such a non-linear behavior. Due to the different properties of these two atomic species, we conclude that the large polarizability of Rydberg states in combination with electric fields of spontaneously ionized Rydberg atoms is the relevant interaction mechanism. In the case of rubidium, we directly measure the electric field in a bistable situation via two-species spectroscopy. In cesium, we make use of the different sign of the polarizability for different l-states and the possibility of applying electric fields. Both these experiments allow us to rule out dipole-dipole interactions, and support our hypothesis of a charge-induced bistability.Comment: 8 pages, 7 figure

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Section: A Rubidiummentioning

confidence: 99%

Charge-induced optical bistability in thermal Rydberg vapor

et al. 2016

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“…Ladder-type systems were recently shown to be advantageous for broadband, noise-free, photon storage [7,8], and they form the basis for quantum nonlinear optics with Rydberg atoms [19]. Nevertheless, a major caveat in ladder-type systems is the residual Doppler broadening due to wavelength mismatch of the two optical transitions, which leads to significant dephasing and broadening of the two-photon resonance [24].…”

Section: Introductionmentioning

confidence: 99%

Power narrowing: counteracting Doppler broadening in two-color transitions

et al. 2019

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Doppler broadening in thermal ensembles degrades the absorption cross-section and the coherence time of collective excitations. In two photon transitions, it is common to assume that this problem becomes worse with larger wavelength mismatch. Here we identify an opposite mechanism, where such wavelength mismatch leads to cancellation of Doppler broadening via the counteracting effects of velocity-dependent light-shifts and Doppler shifts. We show that this effect is general, common to both absorption and transparency resonances, and favorably scales with wavelength mismatch. We experimentally confirm the enhancement of transitions for different low-lying orbitals in rubidium atoms and use calculations to extrapolate to high-lying Rydberg orbitals. These calculations predict a dramatic enhancement of up to 20-fold increase in absorption, even in the presence of large homogeneous broadening. More general configurations, where an auxiliary dressing field is used to counteract Doppler broadening, are also discussed and experimentally demonstrated. The mechanism we study can be applied as well for rephasing of spin waves and increasing the coherence time of quantum memories. Doppler broadening is ubiquitous in atomic and molecular spectroscopy. Atoms and molecules with different thermal velocities experience different Doppler shifts, which broaden the absorption lines and reduce their contrast [1]. Increasing the light intensity typically causes further broadening due to saturation or other powerbroadening mechanisms, such as inhomogeneous light-shifts. These broadening or dephasing mechanisms are major limiting factors, particularly in the field of quantum optics with atomic ensembles [2][3][4][5][6]. For instance, the coherence time of collective excitations in atomic gasses is often limited by Doppler dephasing, hindering the performance of single-photon sources and memories [7-9]. As Doppler broadening is an inhomogeneous dephasing mechanism, one can potentially counteract it by introducing additional velocity-dependent shifts [10][11][12][13][14]. Here we study the counteraction of Doppler broadening by velocity dependent light-shifts and identify an important class of systems where such counteraction occurs naturally, without a need for additional auxiliary fields.Coherent two-photon processes, such as Raman transitions, two-photon absorption, and electromagnetically induced transparency (EIT), are at the heart of many quantum-optics protocols, ranging from quantum light sources and memories [15][16][17][18] to sensing and quantum nonlinear optics [19]. The canonical example of a three-level system employed for these processes is the Λ configuration, where two longlived ground states are coupled via an intermediate excited state. In these systems, two-photon transitions are usually characterized by negligible residual Doppler broadening, as the nearly-degenerate transition wavelengths experience opposite Doppler shifts [20]. Particularly in a degenerate Λ system under EIT conditions, atoms at all velocities cont...

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“…However, ladder EIT cannot be observed in our 'inverted wavelength' system where the upper transition wavelength (1470 nm) 4.1. Introduction is longer than the lower (852 nm) [94,95]. In this chapter we use quantum beats as an effective method to probe such 'inverted-wavelength' ladder systems in a thermal vapour.…”

Section: Introductionmentioning

confidence: 99%

Terahertz Wave Detection and Imaging with a Hot Rydberg Vapour

Wade

2018

Springer Theses

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This thesis investigates the resonant interaction between Rydberg atoms in a hot caesium vapour and terahertz frequency electromagnetic fields, and explores hyperfine quantum beats modified by driving an excited state transition in an inverted ladder scheme. The 21P 3/2 caesium Rydberg atoms are excited using a three-step ladder scheme and we use a terahertz field resonant with the 21P 3/2 → 21S 1/2 transition (0.634 THz), to measure Autler-Townes splitting of a 3-photon Rydberg electromagnetically induced transparency (EIT) feature. The Autler-Townes splitting allows us to infer the terahertz electric field amplitude, and we show a worked example measurement of a low-amplitude electric field, yielding 25 ± 5 mVcm −1. By driving an off-resonant Raman transition which combines the laser and terahertz fields, we restrict the Rydberg excitation to areas of the caesium vapour where the laser and terahertz fields spatially overlap. We show that the terahertz field intensity is proportional I would like to express my heartfelt thanks to everyone who has helped me through the years of my PhD study. Foremost, it has been a privilege to have the guidance of my supervisor, Kevin Weatherill-thank you for your patience, support and confidence. Thank you also to my second supervisor, Charles Adams, for your ideas and suggestions in our weekly meetings. Any of the work would have been impossible without a super team of people. Thank you to Massayuki, Natalia, Patrick, Hadrien and, in particular, Nick, to whom I am grateful for physical insight, laboratory guerrilla tactics and advice for life. Good luck to Lucy, who will be continuing work on the project, and to Massayuki and Natalia who are embarking in new employment. I would also like to thank Mike Tarbutt, Claudio Balocco and Andrew Gallant for loaning us vital equipment and offering helpful advice. Thank you to Ifan Hughes for introducing me to Durham as a summer student. I have been immensely happy working within the AtMol group-thank you to everyone who has made my time so enjoyable. In particular thank you to Rob, James, Christoph, Dan, Pete, Mark and Danny for board games and Dani, Tommy and Nick for lunchtime runs. Thank you Alistair for all the ready-salted crisps(!), and the members of fAtMol for weekly cake and physics chat. Finally I would like to thank my family, Sally, Geof and David, for their support and for passing me their interest in science.

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Optical coherences and wavelength mismatch in ladder systems

Cited by 44 publications

References 39 publications

Charge-induced optical bistability in thermal Rydberg vapor

Charge-induced optical bistability in thermal Rydberg vapor

Power narrowing: counteracting Doppler broadening in two-color transitions

Terahertz Wave Detection and Imaging with a Hot Rydberg Vapour

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