Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE

Time-delayed second-harmonic generation in an atomic vapor of cesium

Alexander I. Lvovsky, Sven R. Hartmann

Published Oct 21, 1998• 0 citations
Publisher

Abstract

Second harmonic generation has hitherto been thought of as simultaneous with the excitation pulse which generates it. Recent experiments in Cs vapor demonstrate otherwise. A short two-photon 6D - 6S resonant excitation pulse in Cs vapor generates a superposition state which would radiate immediately were it not for destructive interference arising from the sample being large compared to the radiation wavelength. The radiation pattern of an isolated radiator (atom) starts out with a null in the plane transverse to the polarization (linear) direction but then rotates about the applied transverse magnetic field developing a radiation component along the phase matched direction which we detect. Experimental results are presented in excellent agreement with theory. Previous delay discrepancies have been resolved by using a nonmetallic sample cell. Cascade and yoked superfluorescence take place but not significantly until after the second harmonic emissions. Quantitative measurements of signal intensity are also presented.

DOI
10.1117/12.328222

Related papers

Time-delayed second-harmonic generation in atomic Cs vapor

Alexander I. Lvovsky, Sven R. Hartmann

Time-delayed second harmonic generation has recently been reported in an atomic vapor of Cs at a temperature near 180 degrees Celsius and situated in a magnetic field of the order of a killogauss. Short 10 ps excitation laser pulses at 885 nm were used to excite a macroscopic electric quadrupole density which was then observed to radiate at 442 nm after a delay of a few hundred picoseconds. The experiment is complicated by the presence of several superfluorescence transitions some of which radiate close to the 442 nm wavelength. These emissions are also delayed and our strategy is to set the experimental conditions so that they only become appreciable after the second harmonic emission is complete. In this paper we show how the second harmonic develops by considering the evolution of the radiation pattern of an isolated atomic radiator (not forbidden to radiate at the second harmonic even in the absence of a magnetic field). We estimate the intensity of the superradiant second harmonic emission and obtain agreement with experiment. Excellent agreement is also obtained between measured and calculated delay.

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE•Sep 26, 1997•0 citations

Time-Delayed Second Harmonic Generation

J. H. Brownell, Xilin Lu, Sven R. Hartmann

Second harmonic generation in Cs vapor is produced by the combined action of a polarized laser pulse and a magnetic field. It is delayed from the 10 ps excitation pulse by several hundred ps. The laser is two-photon resonant with the $6{S}_{\frac{1}{2}}\ensuremath{-}6{D}_{\frac{3}{2}}$ transition and initially induces a macroscopic quadrupole moment whose radiation pattern has a null in the forward direction. The magnetic field reshapes this pattern to produce second harmonic light, which is simply a free polarization decay signal evolving in a manner akin to the free induction decay following an adiabatic demagnetization.

Physical Review Letters•Nov 13, 1995•6 citations

Cooperative superfluorescence and time delayed 2nd harmonic generation

Xilin Lu, J. H. Brownell, Sven R. Hartmann

A 10 ps transform limited optical pump pulse two-photon-resonant with the 6 S1/2-6 D32 442 nm transition in Cs vapor generates a coherent state superposition which, after a delay exceeding the pulse width, gives rise to second harmonic emission (when a transverse magnetic field is present) and superfluorescence (SF) directed against the pump on the upper 6 D3/2-6 P1/2 transition, followed by cooperative SF along the pump simultaneously on both the upper and lower 6 P3/2 − 6 P1/2 transitions, followed in turn by SF against the pump on the lower transition. Phase locked quantum beats associated with the 1.17 GHz hyperfine splitting of the 6 P1/2 appear on all SF emissions.

Progress in Crystal Growth and Characterization of Materials•Jan 1, 1996•0 citations

Second-harmonic generation in atomic vapor with picosecond laser pulses

Doseok Kim, Christopher S. Mullin, Y. Ron Shen

Picosecond laser pulses were used to study the highly forbidden resonant second-harmonic generation (SHG) in potassium vapor. The input intensity dependence, vapor density dependence, buffer-gas pressure dependence, and spatial profile of the SHG were measured. A pump–probe experiment was conducted to probe the time dependence of the SHG signal. The experimental results can be understood from an ionization-initiated dc-field-induced SHG model. A theory of a dc-field-induced SHG model is developed that takes into account the time development of the dc electric field in detail. This temporal buildup of the dc field along with transient coherent excitation between two-photon-allowed transitions can explain the experimental results quantitatively, including the previous vapor SHG results with nanosecond laser pulses.

Journal of the Optical Society of America B•Oct 1, 1997•8 citations

Time-delayed second-harmonic generation in cesium vapor

Alexander I. Lvovsky, Sven R. Hartmann

Refined measurements and analysis of time-delayed second-harmonic generation on the ${6D}_{3/2}{\ensuremath{-}6S}_{1/2}$ transition in Cs vapor are presented that resolve the disparity between the measured and calculated time delays reported in its initial observation. We extend our work to the ${6D}_{5/2}{\ensuremath{-}6S}_{1/2}$ transition which, in agreement with our analysis, is characterized by a slightly smaller delay. For both transitions we also measure the amplitude of the second-harmonic intensity and find it close to what we estimate it should be.

Physical Review A•Nov 1, 1997•0 citations

Yoked Superfluorescence

J. H. Brownell, X. Lu, Sven R. Hartmann

A laser pulse two-photon resonant with the ${6S}_{1/2}\ensuremath{-}{6D}_{3/2}$ 442 nm transition in Cs vapor generates delayed superfluorescence (SF) on the upper ${6D}_{3/2}\ensuremath{-}{6P}_{1/2}$ 876 nm and lower ${6P}_{1/2}\ensuremath{-}{6S}_{1/2}$ 894 nm transitions. Yoked SF is observed in the forward (along the laser) direction as evidenced by the simultaneous appearance of SF on both transitions. Cascade SF is observed in the backward direction, where SF on the lower transition only evolves after it has terminated on the upper. The four SF signals exhibit quantum beats associated with the ${6P}_{1/2}$ hyperfine splitting.

Physical Review Letters•Oct 30, 1995•65 citations
Second harmonic generation has hitherto been thought of as simultaneous with the excitation pulse which generates it. Recent experiments in Cs vapor demonstrate otherwise. A short two-photon 6D - 6S resonant excitation pulse in Cs vapor generates a superposition state which would radiate immediately were it not for destructive interference arising from the sample being large compared to the radiation wavelength. The radiation pattern of an isolated radiator (atom) starts out with a null in the plane transverse to the polarization (linear) direction but then rotates about the applied transverse magnetic field developing a radiation component along the phase matched direction which we detect. Experimental results are presented in excellent agreement with theory. Previous delay discrepancies have been resolved by using a nonmetallic sample cell. Cascade and yoked superfluorescence take place but not significantly until after the second harmonic emissions. Quantitative measurements of signal intensity are also presented.
Time-delayed second harmonic generation has recently been reported in an atomic vapor of Cs at a temperature near 180 degrees Celsius and situated in a magnetic field of the order of a killogauss. Short 10 ps excitation laser pulses at 885 nm were used to excite a macroscopic electric quadrupole density which was then observed to radiate at 442 nm after a delay of a few hundred picoseconds. The experiment is complicated by the presence of several superfluorescence transitions some of which radiate close to the 442 nm wavelength. These emissions are also delayed and our strategy is to set the experimental conditions so that they only become appreciable after the second harmonic emission is complete. In this paper we show how the second harmonic develops by considering the evolution of the radiation pattern of an isolated atomic radiator (not forbidden to radiate at the second harmonic even in the absence of a magnetic field). We estimate the intensity of the superradiant second harmonic emission and obtain agreement with experiment. Excellent agreement is also obtained between measured and calculated delay.
Second harmonic generation in Cs vapor is produced by the combined action of a polarized laser pulse and a magnetic field. It is delayed from the 10 ps excitation pulse by several hundred ps. The laser is two-photon resonant with the $6{S}_{\frac{1}{2}}\ensuremath{-}6{D}_{\frac{3}{2}}$ transition and initially induces a macroscopic quadrupole moment whose radiation pattern has a null in the forward direction. The magnetic field reshapes this pattern to produce second harmonic light, which is simply a free polarization decay signal evolving in a manner akin to the free induction decay following an adiabatic demagnetization.
A 10 ps transform limited optical pump pulse two-photon-resonant with the 6 S1/2-6 D32 442 nm transition in Cs vapor generates a coherent state superposition which, after a delay exceeding the pulse width, gives rise to second harmonic emission (when a transverse magnetic field is present) and superfluorescence (SF) directed against the pump on the upper 6 D3/2-6 P1/2 transition, followed by cooperative SF along the pump simultaneously on both the upper and lower 6 P3/2 − 6 P1/2 transitions, followed in turn by SF against the pump on the lower transition. Phase locked quantum beats associated with the 1.17 GHz hyperfine splitting of the 6 P1/2 appear on all SF emissions.
Picosecond laser pulses were used to study the highly forbidden resonant second-harmonic generation (SHG) in potassium vapor. The input intensity dependence, vapor density dependence, buffer-gas pressure dependence, and spatial profile of the SHG were measured. A pump–probe experiment was conducted to probe the time dependence of the SHG signal. The experimental results can be understood from an ionization-initiated dc-field-induced SHG model. A theory of a dc-field-induced SHG model is developed that takes into account the time development of the dc electric field in detail. This temporal buildup of the dc field along with transient coherent excitation between two-photon-allowed transitions can explain the experimental results quantitatively, including the previous vapor SHG results with nanosecond laser pulses.
Refined measurements and analysis of time-delayed second-harmonic generation on the ${6D}_{3/2}{\ensuremath{-}6S}_{1/2}$ transition in Cs vapor are presented that resolve the disparity between the measured and calculated time delays reported in its initial observation. We extend our work to the ${6D}_{5/2}{\ensuremath{-}6S}_{1/2}$ transition which, in agreement with our analysis, is characterized by a slightly smaller delay. For both transitions we also measure the amplitude of the second-harmonic intensity and find it close to what we estimate it should be.
A laser pulse two-photon resonant with the ${6S}_{1/2}\ensuremath{-}{6D}_{3/2}$ 442 nm transition in Cs vapor generates delayed superfluorescence (SF) on the upper ${6D}_{3/2}\ensuremath{-}{6P}_{1/2}$ 876 nm and lower ${6P}_{1/2}\ensuremath{-}{6S}_{1/2}$ 894 nm transitions. Yoked SF is observed in the forward (along the laser) direction as evidenced by the simultaneous appearance of SF on both transitions. Cascade SF is observed in the backward direction, where SF on the lower transition only evolves after it has terminated on the upper. The four SF signals exhibit quantum beats associated with the 6P1/2{6P}_{1/2}6P1/2​ hyperfine splitting.