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

Journal of Applied Physics

Phase modulation technique for eliminating phase noise in picosecond T2 measurements based on stimulated Raman gain

Martine M. De Maziere, D. Schoemaker

Published Aug 15, 1985• 12 citations
Publisher

Abstract

The pump and probe variant of the stimulated Raman gain technique permits the measurement of picosecond dephasing times with low-power, continuous-wave mode-locked lasers, but it suffers by its susceptibility to inevitable randomly induced fluctuations in the relative phases of the interacting laser fields. The resulting severe requirements on optical stability can be circumvented through application of a double-modulation–detection scheme that we have developed. It is based on rms detection of the T2 signal as generated through application of a low-frequency phase modulation of precise amplitude, additional to the commonly applied rf modulation with corresponding lock-in detection. A detailed description of the method and its experimental realization is presented. T2 measurements on the 656 cm−1 vibration of liquid CS2 illustrate its performance. In comparison with previous techniques, precision is improved by about a factor of 4. But more important is the fact that the technique permits to make a continuous recording of the T2 signal, while achieving at the same time a reduction in measurement time by an order of magnitude. Furthermore, optimization of the optical setup is possible, through direct monitoring of the dephasing signal at any delay. Automating the data taking and processing should be straightforward.

DOI
10.1063/1.336073

Related papers

Vibrational dephasing measurements with cw mode-locked dye lasers

J.P. Heritage

Recent advances in the development of synchronously mode-locked dye-laser systems have permitted the first low-power measurement of the time-resolved dephasing dynamics of a Raman active molecular vibration. Excitation and delayed probing of the coherent ensemble of vibrators is accomplished with the help of synchronized picosecond pulse trains from two independently tunable mode-locked dye lasers. A new probe technique, based on a gain measurement, is employed that provides a signal that scales linearly with the coherent vibrational amplitude. We demonstrate this technique with the first measurement of the dephasing dynamics of the normal mode (656.5 cm−1) of CS2 in the liquid state. An exponential decay with time constant 20±1 psec is obtained for the isotropic component of the coherent scattering.

Applied Physics Letters•Apr 1, 1979•71 citations

Analysis of dephasing signal in picosecond stimulated-Raman-gain experiments

Martine M. De Maziere, Chris Sierens, D. Schoemaker

A detailed theoretical analysis is presented of the dephasing signal measured in four-beam picosecond time-resolved stimulated-Raman-gain experiments. The analytical expressions derived are successful in simulating observations on the CS2 model system under various experimental conditions. It is established that the tail of the curve for sufficiently long delay times is uniquely determined by the vibrational Raman term that yields the vibrational dephasing time T2. It is also found that the rotational dephasing time cannot be fundamentally determined from the rotational Raman peak centered around zero delay. Furthermore, it is shown that the coherence properties of the stimulating laser fields, as distinguished from their pure pulse-envelope properties, are crucially important in determining the time resolution of the experiments and for explaining several experimental phenomena observed under mismatched excitation-pulse conditions. In this respect, the domain model for mode-locked pulses has proved to be useful. It is found that the time resolution of the dephasing measurements is determined by the combined pulse-coherence time of the driving fields and not by the cross-correlation width of the pulse envelopes.

Journal of the Optical Society of America B•Dec 1, 1989•4 citations

Stimulated effects in interferometric four-wave mixing experiments

Lde.S. Menezes, Valery P. Kozich, Cid Bartolomeu de Araujo

Summary form only given. Nonlinear techniques using broadband light have been developed and applied for studying dephasing processes, population and orientational dynamics of molecules. These techniques are based on the fact that in wave-mixing processes one may have the time resolution determined by the laser coherence time instead of the laser pulse duration. One limiting factor of the measurement sensitivity is a constant signal (pedestal), which is present even when the delay time between the exciting broadband beams is substantially longer than their coherence time and relaxation time under study. A technique has been developed, which uses not "white" detection, but spectral filtering in field-correlated four-wave mixing, the so called interferometric four-wave mixing (IFWM), which gives a signal that reveals oscillatory modulation, enabling us to discriminate it more easily from the pedestal. The technique allows to determine rather precisely the frequency of a molecular vibration and its dephasing time, as well as to study damped molecular rotations in liquids. We report the first measurements of population relaxation rates affected by stimulated emission in the presence of the pump field applying the IFWM technique.

Conference on Lasers and Electro-Optics•Jan 1, 2000•0 citations

Phase locking technology for Raman laser system based on 1560 nm external cavity lasers

Kainan Wang, Bing Cheng, Yin Zhou +8 more

The technology of generating Raman laser is not only an important research content in the field of quantum precision measurement, but also a core technology of quantum inertial sensors such as cold atom gravimeter, gyroscope. For 87Rb atoms, two 780-nm lasers with a frequency difference of 6.834 GHz and a stable phase are needed to generate Raman light. Raman lasers can be generated by optical phase-locked loops of two 780-nm narrow linewidth external cavity tunable semiconductor lasers (ECDL). But the system thus developed is complicated in structure and very poor in environmental adaptability. The other method to generate Raman laser is based on intracavity 1560-nm laser with frequency doubling and electro-optic modulation technology. This system is simple in structure and strong in environmental adaptability, but it will introduce sideband effects and cannot achieve phase lock due to the limit by the linewidth and feedback bandwidth performance of the laser. In view of this, based on two new 1560-nm external cavity lasers and a home-made phase-locked circuit, in this paper the phase lock of the laser is achieved, and a Raman laser with low phase noise is obtained. The phase noise of beat note signal is as low as –95 dBc/Hz at the Fourier frequency in a range from 1 kHz to 10 kHz. A comparison of this system with the phase-locked performance of the 780-nm dual laser and the hybrid dual laser shows that this scheme has a slight advantage. In addition, the effect of the phase-locking performance on the phase noise of the cold atom interferometer through the method of piecewise integration is analyzed in this work. The experimental results given in this work provide a scheme for developing a miniaturized Raman optical system suitable for external fields.

Acta Physica Sinica•Jan 1, 2021•1 citation

Self-Modulation and Picosecond-Pulse Generation by Stimulated Raman Scattering

Kōichi Shimoda

The regular structure in frequency broadening spectrum of the self-trapped laser and Raman radiations is produced by the phase-modulation of light waves propagating in the filament with intensity-dependent index of refraction. A quantum-mechanical calculation of double quantum transition in a three-level system is shown to explain the process of self-modulation and the production of picosecond pulses in the Raman process. Coherent coupling of the laser and the Stokes waves produces mutual modulation of large amplitude, if the optical field is strong and the vibrational relaxation time is long. Numerical evaluation for CS2 gives a modulation frequency of about 1011 Hz, when an optical power of 10 kW is trapped in a filament of 2 µm radius. Besides, the effect of self-modulation on the spatial distribution of anti-Stokes emission along the filament is discussed and shown to agree with the experimental results observed by Stoicheff and his co-workers.

Japanese Journal of Applied Physics•Dec 1, 1969•6 citations

Composite Raman-Nath heterodyne interferometry with relevance for precise spectroscopy

Matteo Barbiero, Juan Pablo Salvatierra, Davide Calonico +2 more

Atomic state manipulation by laser radiation requires a stringent control of the light phase noise for precise spectroscopy and quantum computation . In this work we describe a novel interferometer recently employed to estimate the phase noise induced by an optical frequency shifter based on serrodyne modulation for optical frequency standards (Barbiero et al., 2023). The interferometer is generated by an acousto-optic actuator working in the Raman-Nath regime. Using the heterodyne detection between the unshifted optical mode with the first higher order optical components , we are able to detect the differential phase between the two optical path arms with a reduction of the phase noise induced by the actuator. We provide a theoretical treatment for the actuator phase suppression and we estimate the detectable phase noise limit of this interferometer. Finally, we discuss the possible applications in the field of precision measurements.

Optics & Laser Technology•Aug 29, 2024•0 citations
The pump and probe variant of the stimulated Raman gain technique permits the measurement of picosecond dephasing times with low-power, continuous-wave mode-locked lasers, but it suffers by its susceptibility to inevitable randomly induced fluctuations in the relative phases of the interacting laser fields. The resulting severe requirements on optical stability can be circumvented through application of a double-modulation–detection scheme that we have developed. It is based on rms detection of the T2 signal as generated through application of a low-frequency phase modulation of precise amplitude, additional to the commonly applied rf modulation with corresponding lock-in detection. A detailed description of the method and its experimental realization is presented. T2 measurements on the 656 cm−1 vibration of liquid CS2 illustrate its performance. In comparison with previous techniques, precision is improved by about a factor of 4. But more important is the fact that the technique permits to make a continuous recording of the T2 signal, while achieving at the same time a reduction in measurement time by an order of magnitude. Furthermore, optimization of the optical setup is possible, through direct monitoring of the dephasing signal at any delay. Automating the data taking and processing should be straightforward.
Recent advances in the development of synchronously mode-locked dye-laser systems have permitted the first low-power measurement of the time-resolved dephasing dynamics of a Raman active molecular vibration. Excitation and delayed probing of the coherent ensemble of vibrators is accomplished with the help of synchronized picosecond pulse trains from two independently tunable mode-locked dye lasers. A new probe technique, based on a gain measurement, is employed that provides a signal that scales linearly with the coherent vibrational amplitude. We demonstrate this technique with the first measurement of the dephasing dynamics of the normal mode (656.5 cm−1) of CS2 in the liquid state. An exponential decay with time constant 20±1 psec is obtained for the isotropic component of the coherent scattering.
A detailed theoretical analysis is presented of the dephasing signal measured in four-beam picosecond time-resolved stimulated-Raman-gain experiments. The analytical expressions derived are successful in simulating observations on the CS2 model system under various experimental conditions. It is established that the tail of the curve for sufficiently long delay times is uniquely determined by the vibrational Raman term that yields the vibrational dephasing time T2. It is also found that the rotational dephasing time cannot be fundamentally determined from the rotational Raman peak centered around zero delay. Furthermore, it is shown that the coherence properties of the stimulating laser fields, as distinguished from their pure pulse-envelope properties, are crucially important in determining the time resolution of the experiments and for explaining several experimental phenomena observed under mismatched excitation-pulse conditions. In this respect, the domain model for mode-locked pulses has proved to be useful. It is found that the time resolution of the dephasing measurements is determined by the combined pulse-coherence time of the driving fields and not by the cross-correlation width of the pulse envelopes.
Summary form only given. Nonlinear techniques using broadband light have been developed and applied for studying dephasing processes, population and orientational dynamics of molecules. These techniques are based on the fact that in wave-mixing processes one may have the time resolution determined by the laser coherence time instead of the laser pulse duration. One limiting factor of the measurement sensitivity is a constant signal (pedestal), which is present even when the delay time between the exciting broadband beams is substantially longer than their coherence time and relaxation time under study. A technique has been developed, which uses not "white" detection, but spectral filtering in field-correlated four-wave mixing, the so called interferometric four-wave mixing (IFWM), which gives a signal that reveals oscillatory modulation, enabling us to discriminate it more easily from the pedestal. The technique allows to determine rather precisely the frequency of a molecular vibration and its dephasing time, as well as to study damped molecular rotations in liquids. We report the first measurements of population relaxation rates affected by stimulated emission in the presence of the pump field applying the IFWM technique.
The technology of generating Raman laser is not only an important research content in the field of quantum precision measurement, but also a core technology of quantum inertial sensors such as cold atom gravimeter, gyroscope. For 87Rb atoms, two 780-nm lasers with a frequency difference of 6.834 GHz and a stable phase are needed to generate Raman light. Raman lasers can be generated by optical phase-locked loops of two 780-nm narrow linewidth external cavity tunable semiconductor lasers (ECDL). But the system thus developed is complicated in structure and very poor in environmental adaptability. The other method to generate Raman laser is based on intracavity 1560-nm laser with frequency doubling and electro-optic modulation technology. This system is simple in structure and strong in environmental adaptability, but it will introduce sideband effects and cannot achieve phase lock due to the limit by the linewidth and feedback bandwidth performance of the laser. In view of this, based on two new 1560-nm external cavity lasers and a home-made phase-locked circuit, in this paper the phase lock of the laser is achieved, and a Raman laser with low phase noise is obtained. The phase noise of beat note signal is as low as –95 dBc/Hz at the Fourier frequency in a range from 1 kHz to 10 kHz. A comparison of this system with the phase-locked performance of the 780-nm dual laser and the hybrid dual laser shows that this scheme has a slight advantage. In addition, the effect of the phase-locking performance on the phase noise of the cold atom interferometer through the method of piecewise integration is analyzed in this work. The experimental results given in this work provide a scheme for developing a miniaturized Raman optical system suitable for external fields.
The regular structure in frequency broadening spectrum of the self-trapped laser and Raman radiations is produced by the phase-modulation of light waves propagating in the filament with intensity-dependent index of refraction. A quantum-mechanical calculation of double quantum transition in a three-level system is shown to explain the process of self-modulation and the production of picosecond pulses in the Raman process. Coherent coupling of the laser and the Stokes waves produces mutual modulation of large amplitude, if the optical field is strong and the vibrational relaxation time is long. Numerical evaluation for CS2 gives a modulation frequency of about 1011 Hz, when an optical power of 10 kW is trapped in a filament of 2 µm radius. Besides, the effect of self-modulation on the spatial distribution of anti-Stokes emission along the filament is discussed and shown to agree with the experimental results observed by Stoicheff and his co-workers.
Atomic state manipulation by laser radiation requires a stringent control of the light phase noise for precise spectroscopy and quantum computation . In this work we describe a novel interferometer recently employed to estimate the phase noise induced by an optical frequency shifter based on serrodyne modulation for optical frequency standards (Barbiero et al., 2023). The interferometer is generated by an acousto-optic actuator working in the Raman-Nath regime. Using the heterodyne detection between the unshifted optical mode with the first higher order optical components , we are able to detect the differential phase between the two optical path arms with a reduction of the phase noise induced by the actuator. We provide a theoretical treatment for the actuator phase suppression and we estimate the detectable phase noise limit of this interferometer. Finally, we discuss the possible applications in the field of precision measurements.