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arXiv:1905.09484 · Optics Letters

Collimated UV light generation by two-photon excitation to a Rydberg state in Rb vapor

Mark Lam, Sambit B. Pal, Thibault Vogt, Christian Gross, Martin Kiffner, Wenhui Li

Published May 29, 2019• 22 citations
arXivHTMLPDF

Abstract

We use two continuous-wave laser beams of 780 nm and 515 nm to optically drive Rb85 atoms in a heated vapor cell to a low-lying Rydberg state 10D5/2. We observe a collimated ultraviolet (UV) beam at 311 nm, corresponding to the transition frequency from the 11P3/2 state to the 5S1/2 state. This indicates the presence of a coherent four-wave mixing process, built up by two input laser fields as well as terahertz (THz) radiation of 3.28 THz, which is generated by amplified spontaneous emission between the 10D5/2 and 11P3/2 states. We characterize the 311 nm UV light generation and its dependence on various physical parameters. This scheme could open up a new possibility for generating narrow-band THz waves as well as deep UV radiation.

DOI
10.1364/ol.44.002931

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Journal of the Optical Society of America B•Mar 1, 1984•38 citations
We use two continuous-wave laser beams of 780 nm and 515 nm to optically drive Rb85 atoms in a heated vapor cell to a low-lying Rydberg state 10D5/2. We observe a collimated ultraviolet (UV) beam at 311 nm, corresponding to the transition frequency from the 11P3/2 state to the 5S1/2 state. This indicates the presence of a coherent four-wave mixing process, built up by two input laser fields as well as terahertz (THz) radiation of 3.28 THz, which is generated by amplified spontaneous emission between the 10D5/2 and 11P3/2 states. We characterize the 311 nm UV light generation and its dependence on various physical parameters. This scheme could open up a new possibility for generating narrow-band THz waves as well as deep UV radiation.
We optically excite 85 R b atoms in a heated vapor cell to a low-lying Rydberg state 10 D 5 / 2 and observe directional terahertz (THz) beams at 3.3 THz and 7.8 THz. These THz fields are generated by amplified spontaneous emission from the 10 D 5 / 2 state to the 11 P 3 / 2 and 8 F 7 / 2 states, respectively. In addition, we observe ultraviolet (UV) light produced by four-wave mixing of optical pump lasers and the 3.3 THz field. We characterize the generated THz power over the detuning and power of pump lasers, and identify experimental conditions favoring THz and UV generation, respectively. Our scheme paves a new pathway towards generating high-power narrowband THz radiation.
Utilizing two-photon excitation in hot Rb vapor we demonstrate the generation of collimated optical fields at 420 and 1324 nm. Input laser beams at 780 and 776 nm enter a heated Rb vapor cell collinear and circularly polarized, driving Rb atoms to the 5D5/2 state. Under phase-matching conditions coherence among the 5S1/2 → 5P3/2 → 5D5/2 → 6P3/2 transitions produces a blue (420 nm) beam by four-wave mixing. We also observe a forward and backward propagating IR (1324 nm) beam, due to cascading decays through the 6S1/2 → 5P1/2 states. Power saturation of the generated beams is investigated by scaling the input powers to greater than 200 mW, resulting in a coherent blue beam of 9.1 mWpower, almost an order of magnitude larger than previously achieved. We measure the dependences of both beams in relation to the Rb density, the frequency detuning between Rb ground-state hyperfine levels, and the input laser intensities. (C) 2014 Optical Society of America
Utilizing two-photon excitation in hot Rb vapor we demonstrate the generation of collimated optical fields at 420 and 1324 nm. Input laser beams at 780 and 776 nm enter a heated Rb vapor cell collinear and circularly polarized, driving Rb atoms to the 5D(5/2) state. Under phase-matching conditions coherence among the 5S(1/2)→5P(3/2)→5D(5/2)→6P(3/2) transitions produces a blue (420 nm) beam by four-wave mixing. We also observe a forward and backward propagating IR (1324 nm) beam, due to cascading decays through the 6S(1/2)→5(1/2) states. Power saturation of the generated beams is investigated by scaling the input powers to greater than 200 mW, resulting in a coherent blue beam of 9.1 mW power, almost an order of magnitude larger than previously achieved. We measure the dependences of both beams in relation to the Rb density, the frequency detuning between Rb ground-state hyperfine levels, and the input laser intensities.
Collimated ultraviolet (UV) light is generated via four-wave mixing (FWM) in cesium vapor by continuously tuning the wavelength of the pump laser. Terahertz (THz) Stokes light is generated by the stimulated Raman scattering (SRS) effect in the FWM process, and its frequency is adjustable. When exciting the cesium atom to a virtual level using different combinations of pump lasers (P1 and P2), the strength distribution of UV light is asymmetric, which can be explained through a phase-matching mechanism. Furthermore, the SRS effect and phase matching influence the FWM.
We demonstrate the generation of the coherent 420 nm laser via parametric four-wave mixing process in Rb vapor. A single 778 nm laser with circular polarization is directly injected into a high-density atomic vapor, which drives the atoms from the 5S1/2 state to the 5D5/2 state with monochromatic two-photon transition. The frequency up-conversion laser is generated by the parametric four-wave mixing process under the phase matching condition. This coherent laser is firstly certified by the knife-edge method and a narrow range grating spectrometer. Then the generated laser power is investigated in terms of the power and frequency of the incoming beam as well as the density of the atoms. Finally, a 420 nm coherent laser with power of 19 μW and beam quality of M x 2 = 1.32 , M y 2 = 1.37 is obtained with optimal experimental parameters. This novel laser shows potential prospects in the measurement of material properties, information storage, and underwater optical communication.
A pulsed dye-laser beam (ωL) pumped by a frequency-doubled Nd:YAG laser is focused into a heat-pipe oven containing potassium vapor (nk ≈ 1016 cm−3). Two-photon resonant four-wave and six-wave mixing processes using the potassium 8s 2S1/2 state are investigated. Thirty-two coherent UV radiation lines are generated within the range of 300–400 nm through the processes ωUV = 2ωL ± ωIR and ωUV = 2ωL − ω′IR − ω″IR ± ω‴IR, where ωIR are frequencies of laser-induced IR waves generated in the vapor near the transitions 8S–7P, 7P–7S, 7P–5D, 8S–6P, 7S–6P, 5D–6P, etc. The influence of resonant enhancement on the UV line intensities and the phase-matching condition are analyzed.