© 2026 Aqora Quantum S.A.S.

Terms Privacy Legal Notice

Journal of Modern Optics

Generation of single-cycle pulses spaced by an integer number of molecular periods

Andrea Burzo, Alexei V. Sokolov

Published Nov 1, 2004• 3 citations

Abstract

Previous work has shown that a new light source consisting of mutually coherent spectral sidebands ranging from 2.94 μm to 195 nm can be obtained by adiabatic preparation of a molecular ensemble in a single vibrational superposition state. Molecular motion modulated the refractive index and thus led to the frequency modulation of the driving beat-note. The resulting sidebands were equidistant and separated by a frequency equal to the modulation frequency. In the present work we extend this idea by applying more input fields to the molecular ensemble. We take two input fields separated by one half of the modulation frequency, such that their second harmonics drive the molecular ensemble. The proposed approach results in generating an equidistant comb of frequencies separated by a fraction (1/4) of the modulation frequency. Moreover, the intensity of the generated train of pulses increases by the inverse of the same factor. An important feature of the generated comb is that it reaches zero frequency, and as a consequence allows for control of the absolute phase, or the phase of the carrier with respect to the envelope. Since many physical processes, for example photoionization of molecules by intense laser pulses, are influenced by the time dependence of the electric field (and not the envelope), control of absolute phase will become an important issue for few-cycle pulses.

DOI: 10.1080/09500340408231825

Related papers

Generation and control of femtosecond pulses by molecular modulation

Alexei V. Sokolov, Miro Y. Shverdin, D. R. Walker +4 more

We have demonstrated that coherent molecular modulation can result in the collinear generation of mutually-coherent spectral sidebands that extend in frequency from the infrared to the far ultraviolet. Our technique is based on adiabatic preparation of a highly coherent molecular superposition-state, which is achieved by using narrow-linewidth lasers slightly detuned from a Raman resonance. The phases of the resultant Stokes and anti-Stokes sidebands are adjusted in order to synthesize desired single-cycle pulse trains at the target. In this article we review recent improvements and developments in this area, including: techniques for increasing the number of generated sidebands; synchronization of the pulse trains with the molecular motion in the given molecular system; laser self-focusing and spatial soliton formation due to the coherent interaction of light with oscillating molecules. In the future, this Raman source may produce sub-cycle optical pulses, and allow synthesis of waveforms where the electric field is a predetermined function of time, not limited to a quasi-sinusoidal oscillation.

Journal of Modern Optics•Jan 20, 2005•67 citations

Raman Generation by Phased and Antiphased Molecular States

Alexei V. Sokolov, D. R. Walker, Deniz D. Yavuz +2 more

We use molecular deuterium and two driving lasers to demonstrate collinear generation of mutually coherent equidistant sidebands, covering $50000{\mathrm{cm}}^{\ensuremath{-}1}$ of spectral bandwidth and ranging from $2.94\ensuremath{\mu}\mathrm{m}$ to 195 nm in wavelength. The essential idea is the adiabatic preparation of a single, highly coherent ( $|{\ensuremath{\rho}}_{\mathrm{ab}}|\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.33$) molecular eigenstate.

Physical Review Letters•Jul 17, 2000•247 citations

Femtosecond light source for phase-controlled atomic processes

Stephen E. Harris, Alexei V. Sokolov, D. R. Walker +2 more

Recent experiments have shown that coherent molecular oscillations may generate a comb of coherent collinear sidebands with 50,000 cm/sup -1/ of spectral bandwidth. The essence of this technique is the use of a Raman transition with a sufficiently large coherence that the generation and phase slip length are of the same order. The coherence is established by driving the molecular transition with two single-mode laser fields slightly detuned from the Raman resonance, so as to excite a single molecular superposition state. This talk will summarize the characteristics of this light source and describe two recent experiments which show the mutual coherence of the generated sidebands.

IEEE Lasers and Electro-Optics Society Annual Meeting (LEOS)•Nov 13, 2002•0 citations

Implementation of a single femtosecond optical frequency comb for rovibrational cooling

Wufu Shi, Svetlana Malinovskaya

We show that a single femtosecond optical frequency comb may be used to induce two-photon transitions between molecular vibrational levels to form ultracold molecules (e.g., KRb). The phase across an individual pulse in the pulse train is sinusoidally modulated with a carefully chosen modulation amplitude and frequency. Piecewise adiabatic population transfer is fulfilled to the final state by each pulse in the applied pulse train, providing a controlled population accumulation in the final state. Detuning the pulse train carrier and modulation frequency from one-photon resonances changes the time scale of molecular dynamics but leads to the same complete population transfer to the ultracold state. A standard optical frequency comb with no modulation is shown to induce similar dynamics, leading to rovibrational cooling.

arXiv:1001.3183•Physical Review A•Jul 13, 2010•16 citations

Subfemtosecond-pulse generation by rotational molecular modulation and pulse-spacing increase

Jian Wu, Heping Zeng

A technique is proposed to increase multiplicatively the pulse spacing of a periodic subfemtosecond-pulse train based on molecular modulation, with more pairs of driving lasers to control the higher-order stimulated Raman scattering. We demonstrate that the pulse spacing can be readily doubled, tripled, or even quadrupled by using pairs of off-resonant two-photon Raman transitions driven by laser beams of sufficient intensities and relatively shifted carrier frequencies. A periodic subfemtosecond-pulse train with a pulse width down to 0.53 fs and pulse spacing up to 376 fs can be generated with appropriate molecular coherence control of the fundamental rotational transition in molecular hydrogen.

Physical Review A•Jul 9, 2003•12 citations

Subfemtosecond pulse generation by nonadiabatic molecular modulation

Jian Wu, Heping Zeng

We suggest a technique to generate subfemtosecond pulse train in a Raman generator driven by three sufficiently intense single-mode laser beams whose carrier frequencies are tuned off the Raman resonance with two different two-photon detunings. The Raman interaction establishes a molecular modulation through a nonadiabatic process. The simulation based on the first fundamental vibrational Raman transition of solid hydrogen indicates that subfemtosecond pulse train can be generated when the signs of the two-photon detunings are opposite. This opens an experimentally feasible way to observe enhanced generation of broadband Raman sidebands as well as compression of the phase-locked Raman sidebands into subfemtosecond pulse trains in the same Raman media with above- and below-resonance Raman excitations.

Applied Physics Letters•Sep 12, 2003•1 citation

Previous work has shown that a new light source consisting of mutually coherent spectral sidebands ranging from 2.94 μm to 195 nm can be obtained by adiabatic preparation of a molecular ensemble in a single vibrational superposition state. Molecular motion modulated the refractive index and thus led to the frequency modulation of the driving beat-note. The resulting sidebands were equidistant and separated by a frequency equal to the modulation frequency. In the present work we extend this idea by applying more input fields to the molecular ensemble. We take two input fields separated by one half of the modulation frequency, such that their second harmonics drive the molecular ensemble. The proposed approach results in generating an equidistant comb of frequencies separated by a fraction (1/4) of the modulation frequency. Moreover, the intensity of the generated train of pulses increases by the inverse of the same factor. An important feature of the generated comb is that it reaches zero frequency, and as a consequence allows for control of the absolute phase, or the phase of the carrier with respect to the envelope. Since many physical processes, for example photoionization of molecules by intense laser pulses, are influenced by the time dependence of the electric field (and not the envelope), control of absolute phase will become an important issue for few-cycle pulses.

We have demonstrated that coherent molecular modulation can result in the collinear generation of mutually-coherent spectral sidebands that extend in frequency from the infrared to the far ultraviolet. Our technique is based on adiabatic preparation of a highly coherent molecular superposition-state, which is achieved by using narrow-linewidth lasers slightly detuned from a Raman resonance. The phases of the resultant Stokes and anti-Stokes sidebands are adjusted in order to synthesize desired single-cycle pulse trains at the target. In this article we review recent improvements and developments in this area, including: techniques for increasing the number of generated sidebands; synchronization of the pulse trains with the molecular motion in the given molecular system; laser self-focusing and spatial soliton formation due to the coherent interaction of light with oscillating molecules. In the future, this Raman source may produce sub-cycle optical pulses, and allow synthesis of waveforms where the electric field is a predetermined function of time, not limited to a quasi-sinusoidal oscillation.

We use molecular deuterium and two driving lasers to demonstrate collinear generation of mutually coherent equidistant sidebands, covering $50000{\mathrm{cm}}^{\ensuremath{-}1}$ of spectral bandwidth and ranging from $2.94\ensuremath{\mu}\mathrm{m}$ to 195 nm in wavelength. The essential idea is the adiabatic preparation of a single, highly coherent ( $|{\ensuremath{\rho}}_{\mathrm{ab}}|\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.33$) molecular eigenstate.

Recent experiments have shown that coherent molecular oscillations may generate a comb of coherent collinear sidebands with 50,000 cm/sup -1/ of spectral bandwidth. The essence of this technique is the use of a Raman transition with a sufficiently large coherence that the generation and phase slip length are of the same order. The coherence is established by driving the molecular transition with two single-mode laser fields slightly detuned from the Raman resonance, so as to excite a single molecular superposition state. This talk will summarize the characteristics of this light source and describe two recent experiments which show the mutual coherence of the generated sidebands.

We show that a single femtosecond optical frequency comb may be used to induce two-photon transitions between molecular vibrational levels to form ultracold molecules (e.g., KRb). The phase across an individual pulse in the pulse train is sinusoidally modulated with a carefully chosen modulation amplitude and frequency. Piecewise adiabatic population transfer is fulfilled to the final state by each pulse in the applied pulse train, providing a controlled population accumulation in the final state. Detuning the pulse train carrier and modulation frequency from one-photon resonances changes the time scale of molecular dynamics but leads to the same complete population transfer to the ultracold state. A standard optical frequency comb with no modulation is shown to induce similar dynamics, leading to rovibrational cooling.

A technique is proposed to increase multiplicatively the pulse spacing of a periodic subfemtosecond-pulse train based on molecular modulation, with more pairs of driving lasers to control the higher-order stimulated Raman scattering. We demonstrate that the pulse spacing can be readily doubled, tripled, or even quadrupled by using pairs of off-resonant two-photon Raman transitions driven by laser beams of sufficient intensities and relatively shifted carrier frequencies. A periodic subfemtosecond-pulse train with a pulse width down to 0.53 fs and pulse spacing up to 376 fs can be generated with appropriate molecular coherence control of the fundamental rotational transition in molecular hydrogen.

We suggest a technique to generate subfemtosecond pulse train in a Raman generator driven by three sufficiently intense single-mode laser beams whose carrier frequencies are tuned off the Raman resonance with two different two-photon detunings. The Raman interaction establishes a molecular modulation through a nonadiabatic process. The simulation based on the first fundamental vibrational Raman transition of solid hydrogen indicates that subfemtosecond pulse train can be generated when the signs of the two-photon detunings are opposite. This opens an experimentally feasible way to observe enhanced generation of broadband Raman sidebands as well as compression of the phase-locked Raman sidebands into subfemtosecond pulse trains in the same Raman media with above- and below-resonance Raman excitations.