Resonant Light Pressure Research Articles

Giant resonant light forces in microspherical photonics

Resonant light pressure effects can open new degrees of freedom in optical manipulation with microparticles, but they have been traditionally considered as relatively subtle effects. Using a simplified two-dimensional model of surface electromagnetic waves evanescently coupled to whispering gallery modes (WGMs) in transparent circular cavities, we show that under resonant conditions the peaks of the optical forces can approach theoretical limits imposed by the momentum conservation law on totally absorbing particles. Experimentally, we proved the existence of strong peaks of the optical forces by studying the optical propulsion of dielectric microspheres along tapered microfibers. We observed giant optical propelling velocities ∼0.45 mm s−1 for some of the 15-20 µm polystyrene microspheres in water for guided powers limited at ∼43 mW. Such velocities exceed previous observations by more than an order of magnitude, thereby providing evidence for the strongly enhanced resonant optical forces. We analyzed the statistical properties of the velocity distribution function measured for slightly disordered (∼1% size variations) ensembles of microspheres with mean diameters varying from 3 to 20 µm. These results demonstrate a principal possibility of optical sorting of microspheres with the positions of WGM resonances overlapped at the wavelength of the laser source. They can be used as building blocks of the lossless coupled resonator optical waveguides and various integrated optoelectronics devices.

Magnetoassisted pump–probe spectroscopy of cesium atoms

We studied the spectral behavior of a probe transmission in the presence of a counterpropagating pump beam for various laser polarizations and magnetic fields with and without the assistance of an additional repopulation laser beam. These parametric studies enabled us to distinctively extricate the influence of saturation, optical pumping, and resonant light pressure. The enhanced probe absorption resulting from the pump-beam-induced Zeeman substate dressing was maximized when the change in the resonance frequency was suitably compensated by the change in the Doppler shift arising from resonant light pressure. The possibility of tuning the laser frequency locked to saturation absorption spectroscopy was investigated and implemented to a laser cooling and trapping setup.

10.1007/s11490-008-1012-3

The application of resonant light pressure in the presence of nonuniform bichromatic laser fields for the localization and control of ultracold electron-ion plasma in which the quantum transitions of ions are resonant with respect to the laser radiation is analyzed. It is demonstrated that the so-called rectified radiation forces that selectively act upon plasma ions and give rise to a dissipative optical superlattice (for ultracold plasma) whose period is significantly greater than the radiation wavelength can be used for this purpose.

Dissipative optical superlattice for confinement of ultracold plasma with resonant ions

The application of resonant light pressure in the presence of nonuniform bichromatic laser fields for the localization and control of ultracold electron-ion plasma in which the quantum transitions of ions are resonant with respect to the laser radiation is analyzed. It is demonstrated that the so-called rectified radiation forces that selectively act upon plasma ions and give rise to a dissipative optical superlattice (for ultracold plasma) whose period is significantly greater than the radiation wavelength can be used for this purpose.

Effect of light pressure on transitions from excited states of the Ne atom

Anomalous behavior of the saturated absorption resonance line shape on the $1\phantom{\rule{0.2em}{0ex}}{s}_{5}\ensuremath{-}2\phantom{\rule{0.2em}{0ex}}{p}_{8}(J=2\ensuremath{-}J=2)$ transition in the Ne atom is experimentally observed. The shape of the saturation resonance on transitions with degenerate excited states of atoms is numerically analyzed. The reasons and conditions for the anomalous behavior of the resonance line shape and the formation of its doublet spectral structure are established. The influence of the resonant light pressure force on the amplitude and the frequency properties of the saturated resonance is investigated. It is shown, that the asymmetry of the doublet splitting of the resonance is caused by the effect of resonant light pressure.

The shape of saturated absorption resonance in atoms with degenerate levels and light pressure effect

Anomalous behavior of the shape of saturated absorption resonance on the transition 1s5→ 2p8 (J=2→J=2) in the Ne atom is experimentally observed. The shape of the saturation resonance on transitions with degenerate excited states of atoms is analyzed numerically and the reasons for the anomalous behavior of the resonance shape and the formation of its doublet spectral structure are established. The effect of the resonance light pressure on the amplitude and frequency properties of resonance is investigated. It is shown that the asymmetry of the doublet splitting of the resonance is associated with the effect of resonance light pressure.

Light-pressure-induced line-shape of the saturation resonance dip in an atomic gas

The effect of a force of resonance light pressure on the amplitude and frequency properties of the absorption resonance dip occurring in optical saturation spectroscopy of a gas of two level atoms was studied. On the basis of numerical solutions of the Liouville and Fokker–Planck equations the behaviour pattern of the velocity distribution function of a two level atomic gas in relation to the saturation intensity and time of their interaction with a strong resonant light field was evaluated. The shape of a resonance line, related to saturated absorption, and its location relative to the frequency of the atomic transition were determined taking into account the dynamics of the velocity distribution function. It is established, that the line shape is determined by the interaction of the strong light field with slow moving atoms. The represented numerical results explained qualitatively a number of experimental facts, that could not be explained before.

Selective optical trap for low-temperature plasma

The possibility is demonstrated of utilizing resonant light pressure to provide prolonged selective optical confinement of a low-temperature plasma with resonant ions. For this purpose it is proposed to employ rectified gradient forces in strong interfering bichromatic fields and laser cooling methods.

Light-pressure-induced nonlinear dispersion of a laser field interacting with an atomic gas.

We report on detailed studies of the effect of resonant light pressure on the optical response of an atomic gas to a single monochromatic laser field. In this very elementary situation of laser spectroscopy, the redistribution of atomic velocities that is induced by spontaneous light pressure leads to a novel contribution to the optical dispersion curve of the medium. This light-pressure-induced dispersion phenomenon displays a pronounced nonlinear dependence on the laser intensity. Moreover, for a given intensity, its strength is closely related to the laser beam diameter. As most important feature, this light-pressure-induced dispersion displays an even symmetry with respect to the optical detuning from line center. As a result, the total Doppler-broadened dispersion curve of the gas can become asymmetric, and a significant shift of the dispersion line center can occur. In addition to a detailed theoretical description of the phenomenon, we report on its experimental investigation on the \ensuremath{\lambda}=555.6 nm $^{1}$${\mathit{S}}_{0}$${\mathrm{\ensuremath{-}}}^{3}$${\mathit{P}}_{1}$ transition in atomic ytterbium vapor with the use of frequency-modulation spectroscopy. The experimental findings are in good quantitative agreement with theoretical predictions.

The effect of resonant light pressure in saturation spectroscopy

We report on line-shape modifications in optical saturation spectroscopy on an atomic gas, which are caused by resonant light pressure: Asymmetries and line shifts occur as a result of the small modification of the atomic velocity distribution that is caused by the spontaneous scattering force of the saturating light field. In addition to a detailed theoretical description, we report on the observation of this phenomenon in atomic Yb vapor. Our measurements clearly show the expected light-pressure-induced modifications of both absorptive and dispersive saturation signals and demonstrate the significance of the phenomenon for high-resolution laser spectroscopy.

Light-pressure-induced nonlinear dispersion in a Doppler-broadened medium: theory and experimental proposal

We study the effect of resonant light pressure on the optical response of a Doppler-broadened atomic medium to a single monochromatic laser field. As a main consequence of the spontaneous scattering force, a novel contribution to the optical dispersion of the atomic gas is predicted, which shows a pronounced nonlinear intensity dependence; moreover, for a given laser intensity, its strength is closely related to the laser-beam diameter. Most importantly, this light-pressure-induced dispersion displays an even symmetry with respect to the optical Doppler detuning; as a result, the total dispersion curve of the medium can be changed substantially. In addition to a detailed theoretical description of the phenomenon, we propose a simple experiment based on frequency-modulation spectroscopy for the measurement of the predicted nonlinear dispersion feature.

Collimation of atomic beams by resonant laser radiation pressure

The application of the resonant light pressure created by an axially symmetrical light field for collimating atomic beams has been considered. As an example, consideration is given to the possibility of collimating an atomic beam by the light field produced by the reflection of a plane wave from the internal surface of a metal cone. It has been shown that the radiation pressure can reduce the atomic-beam transverse velocities to the value of the order of 100 cm/s which corresponds to effective temperature of about 10−3 K. A method for producing collimated beams of cold atoms based on simultaneous deceleration and collimation of atomic beams by resonant laser radiation pressure is proposed.

Dynamics of a three-level atom in a resonant light field

The paper is devoted to a consideration of the motion of a three-level atom in two resonant light waves. A kinetic equation of the Fokker-Planck type for the atomic distribution function is derived, which is valid when the recoil energy is small compared to the linewidths of the resonant transitions. The detailed behaviour of the radiation force and the diffusion tensor are studied numerically. The case of exact resonance and the nonresonant case are both considered. It is shown that a detuning from exact resonance results in a drastic decrease of the resonant light pressure force. For the detuning we determine the condition, under which an efficient action of the light pressure on a three-level atom takes place.

On the possibility of highly selective detection of rare isotopic atoms by means of resonant laser light pressure

The application of laser deceleration and monochromatization of atoms in the schemes of single atom fluorescent detection is examined. The analysis performed shows that the use of resonant-light pressure in experiments with atomic beams enables one to obtain an ultimate value of detection selectivity that ranges from 1013 to 1016.

Atomic beam deflection by resonant light pressure

A method is proposed for generating a near-monoenergetic atomic beam by deflection resulting from the pressure of light of a resonance frequency. A system in which a beam of atoms passes through N periodically distributed regions of interaction with laser radiation is considered: the system ensures a high selectivity in respect of the atomic velocities. The following applications of deflection of monoenergetic atoms are considered: analysis of the velocity distribution in an atomic beam, determination of the lifetime of excited atomic states, and testing of the theory of photon statistics.

On the resonance light pressure

An expression for the resonance radiation pressure is found in the framework of the Weisskopf-Wigner theory. It is shown, that at saturation its value is twice that of the phenomenological theory.

The motion of atoms and molecules in a resonance light field

The influence of the resonance light pressure on the motion of atoms and molecules is studied. A kinetic equation has been obtained describing the action on particles of both the mean force of light pressure and its fluctuations. The forces that are considered are due to spontaneous and stimulated transitions and also to a certain combination thereof. The kinetic equation is used to describe the scattering of atoms in conditions close to the experimental ones [16]. The temperature of atoms cooled in a standing wave with the aid of the force of light pressure of the combined type has also been found.

Broad band resonant light pressure

Broad band resonant light pressure

Broad band resonant light pressure

This paper treats the mechanical pressure of resonant light acting on a two-level system, where the degenerate magnetic sublevels are taken into account. The theory is developed with arbitrary relations between the quantization axis and the propagation and polarization of the light. Rate terms are obtained both for spontaneous and induced transitions; the requirements of incoherence put restrictions on the possible geometries of the experiment. The rate equations are restricted to motion along a light beam only; this one-dimensional case is simpler to handle. For small recoil velocities a Fokker-Planck equation is derived, and an adiabatic elimination procedure enables us to derive an equation for the velocity distribution of the total population. The assumptions and approximations are formulated and discussed.

Resonant light pressure forces in a strong standing laser wave

The light pressure forces acting on a two-level atom in a strong standing laser wave are calculated. It is shown that at strong saturation of a resonant atomic transition the velocity dependence of these forces include sharp variations due to multiphoton resonances. At small atomic velocities these multiphoton resonances may even change the sign of the forces. The results obtained are important for many applications of resonant light pressure, e.g. in cooling and trapping of atoms in standing laser waves.