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

Annual Meeting Optical Society of America

Observation of spatial ringing and internal beam fission in cw pumped pink ruby

Sohrab Afzal, N. M. Lawandy

Published Jan 1, 1988• 0 citations
Publisher

Abstract

Self-focusing and spatial ring formation have been predicted in strongly absorbing media of two-level atoms. The requirement for observation of this effect is that the absorption-length product must be greater than the ratio of the input intensity to the saturation intensity and both greater than unity. We have observed a spatial ring formation of an argon-ion laser beam traversing a sample of pink ruby pumped above resonance. In addition, we observed the development of on-axis nulls in the intensity profile. Experiments were also performed on the low-frequency side of the line with a rhodamine 6G dye laser. Ruby is a three-level system that can be modeled as a two-level system with a low saturation intensity because of the long lifetime of the Kramers doublet. The ruby sample was 7 cm long with an absorption coefficient of 0.75 cm−1. With an input intensity of 1 kW/cm2 we are ~2.5 times the saturation intensity of ruby, thereby satisfying both conditions where a spatial ring formation would be expected. We also observed intensity-dependent beam fission leading to an off-axis beam that tracked the c axis and was of the opposite polarization of the main beam. Experiments performed on a 1-cm sample of ruby exhibited no rings, and a second beam was not observed confirming the predicted conditions and excluding any interface effects.

DOI
10.1364/oam.1988.wz1

Related papers

Nonlinear Absorption of Coherent Resonance Radiation in Pink Ruby

Robert C. Mitchell, Jerald R. Izatt

A high resolution study has been made of the R(1) doublet in the absorption spectrum of pink ruby, using a temperature-controlled ruby laser as a variable frequency monochromatic source. The source and sample crystals were oriented for measurement of the absorption of alpha-polarized radiation, and the measurements were made near liquid nitrogen temperature. The observed absorption coefficient was found to decrease as the intensity of the incident beam was increased, indicating that significant depletion of the ground state was effected by the resonant pumping action of the laser beam. The highest laser beam intensity employed was approximately 100 J/cm(2). At this intensity level a significant reduction in the spectral spacing of the R(1)(+/-3/2) and R(1)(+/-(1/2)) components of the absorption doublet was also observed. Time-resolved spectral measurements showed, moreover, that at similar intensity levels, temporally smooth incident beams at frequencies near the absorption line peaks emerged from the sample temporally structued. The observed reduction in the absorption coefficient agrees well with calculations based on a simple model for ground state depletion, but no detailed theoretical explanation of the other observed phenomena has yet been developed.

Applied Optics•Jan 1, 1968•4 citations

Observation of Self-Focusing via Saturable Absorption in Atomic Na

J.S. Satchell, R. J. Ballagh, Weston J. Sandle

There has been recent interest in the phenomenon of on-axis enhancement of an intense cw laser beam in a strongly absorbing, nonrefractive, nonlinear medium.1,2 The purpose of this paper is to present experimental observations of this cw on-resonant enhancement (CORE) and the associated Fresnel fringe structure and narrowing (self-focusing) of the spatial profile. We use the collisionally broadened D1 line of atomic sodium. We also illustrate the relatively close agreement of predictions1 based on a simple model of homogeneously broadened two-state absorbers.

Journal of the Optical Society of America B•Jan 1, 1984•0 citations

Optical-Microwave Double-Resonance Studies of Ruby

A. Szabó

Studies of the resonant interaction of radiation from a liquid-nitrogen-cooled ruby laser with a ruby crystal in the temperature range 4.2°–100°K are described. The interaction was measured by observation of the change which occurs in the Cr3+ ground state EPR absorption on laser irradiation. At low radiation intensities, the temperature dependence of this change is shown to be determined by the well-known thermal tuning behavior of the R lines. Precise measurement of the relative laser and ruby-sample absorption frequencies by this technique of double-resonance spectroscopy is described. Under optical saturation conditions, additional temperature-dependent pumping effects occur at low temperatures. In particular, as the ruby temperature is increased from 4.2° to 40°K, the laser-induced change in EPR absorption is observed to undergo a large increase. This increase cannot be explained by a relative thermal shift of the laser and absorption frequencies which is known to be very small in this temperature range. The phenomena are attributed in part to the temperature-dependent homogeneous linewidth which determines the widths of the holes burnt into the inhomogeneous strain-broadened R lines. Calculations indicate that the related temperature-dependent thermalization process which redistributes excited Cr3+ among the 2E levels quantitatively accounts for most of the increase.

Journal of Applied Physics•Nov 1, 1968•3 citations

Observation of continuous-wave on-resonance enhancement (A)

Kuochou Tai, Hyatt M. Gibbs, Michael C. Rushford +4 more

Recently, Boshier and Sandle1 predicted an unexpected and interesting phenomenon of the propagation of intense cw light through a strongly absorptive two-level medium: an enhancement of the on-axis intensity occurs with the laser frequency tuned to exact resonance with the atomic transition. Previously, cw self-focusing was thought to occur only on the high-frequency side of the resonance where nonlinear dispersion gives rise to an effective positive lens that focuses the entire beam,2,3 And indeed this cw on-resonance enhancement (CORE) arises from a different mechanism: the nonlinear absorption strips away the outer portions of the beam while diffraction of the light in the outer edge of the remaining core directs some of the beam toward the axis, resulting in near-field Fresnel fringes and CORE.

Journal of the Optical Society of America B•Jan 1, 1984•0 citations

Verification of the Kramers–Kronig relations in optically pumped ruby

Brent L. Bean, Jerald R. Izatt

The real and imaginary parts of the complex index of refraction have been measured in the R1 line of optically pumped ruby. The experiments, which employed a temperature-controlled, single-mode ruby laser as a variable-frequency monochromatic source, were performed near liquid-nitrogen temperature, where the R1 doublet structure is well resolved. R1 absorption profiles were measured for several optical-pumping conditions, ranging from zero up to a pump power that excited a population in the 2E state equal to about 60% of the population of the 4A2 ground state. For each pumping condition, the anomalous-dispersion curve was measured interferometrically. The spectral profiles of the absorption coefficient and the anomalous dispersion display a dependence on the optical-pumping conditions that is more complicated than simple saturation of the R1 transitions, but for given pumping conditions the two quantities are correlated as predicted by the Kramers–Kronig relations.

Journal of the Optical Society of America•Jul 1, 1973•2 citations

Self-focusing and spatial ringing of intense cw light propagating through a strong absorbing medium

Martine Le Berre, Elisabeth Ressayre, Andree A. Tallet

This paper deals with the strongly nonlinear regime of the atom and field interaction which arises for both high cw input intensities and large absorption. The intensity of the light inside the medium is then highly nonlinear with respect to the incident one, the order of magnitude of the nonlinearity being approximately $\ensuremath{\alpha}1$, for a cell of length $l$ and an absorption length ${\ensuremath{\alpha}}^{\ensuremath{-}1}$. The transverse effects related to such a regime are analytically treated. They are shown to induce self-focusing, blooming, and also spatial ringing. These features strongly depend on the distance of the screen from the cell, on the detuning between the incident wavelength and that of the atomic transition, and on the input intensity. For self-focusing, analytical expressions of the focal point, of the waist, and of the maximum intensity are given. This model for transverse effects in strong nonlinear propagation of pulses would contribute to explain recent anomalous observations.

Physical Review A•Mar 1, 1982•38 citations
Self-focusing and spatial ring formation have been predicted in strongly absorbing media of two-level atoms. The requirement for observation of this effect is that the absorption-length product must be greater than the ratio of the input intensity to the saturation intensity and both greater than unity. We have observed a spatial ring formation of an argon-ion laser beam traversing a sample of pink ruby pumped above resonance. In addition, we observed the development of on-axis nulls in the intensity profile. Experiments were also performed on the low-frequency side of the line with a rhodamine 6G dye laser. Ruby is a three-level system that can be modeled as a two-level system with a low saturation intensity because of the long lifetime of the Kramers doublet. The ruby sample was 7 cm long with an absorption coefficient of 0.75 cm−1. With an input intensity of 1 kW/cm2 we are ~2.5 times the saturation intensity of ruby, thereby satisfying both conditions where a spatial ring formation would be expected. We also observed intensity-dependent beam fission leading to an off-axis beam that tracked the c axis and was of the opposite polarization of the main beam. Experiments performed on a 1-cm sample of ruby exhibited no rings, and a second beam was not observed confirming the predicted conditions and excluding any interface effects.
A high resolution study has been made of the R(1) doublet in the absorption spectrum of pink ruby, using a temperature-controlled ruby laser as a variable frequency monochromatic source. The source and sample crystals were oriented for measurement of the absorption of alpha-polarized radiation, and the measurements were made near liquid nitrogen temperature. The observed absorption coefficient was found to decrease as the intensity of the incident beam was increased, indicating that significant depletion of the ground state was effected by the resonant pumping action of the laser beam. The highest laser beam intensity employed was approximately 100 J/cm(2). At this intensity level a significant reduction in the spectral spacing of the R(1)(+/-3/2) and R(1)(+/-(1/2)) components of the absorption doublet was also observed. Time-resolved spectral measurements showed, moreover, that at similar intensity levels, temporally smooth incident beams at frequencies near the absorption line peaks emerged from the sample temporally structued. The observed reduction in the absorption coefficient agrees well with calculations based on a simple model for ground state depletion, but no detailed theoretical explanation of the other observed phenomena has yet been developed.
There has been recent interest in the phenomenon of on-axis enhancement of an intense cw laser beam in a strongly absorbing, nonrefractive, nonlinear medium.1,2 The purpose of this paper is to present experimental observations of this cw on-resonant enhancement (CORE) and the associated Fresnel fringe structure and narrowing (self-focusing) of the spatial profile. We use the collisionally broadened D1 line of atomic sodium. We also illustrate the relatively close agreement of predictions1 based on a simple model of homogeneously broadened two-state absorbers.
Studies of the resonant interaction of radiation from a liquid-nitrogen-cooled ruby laser with a ruby crystal in the temperature range 4.2°–100°K are described. The interaction was measured by observation of the change which occurs in the Cr3+ ground state EPR absorption on laser irradiation. At low radiation intensities, the temperature dependence of this change is shown to be determined by the well-known thermal tuning behavior of the R lines. Precise measurement of the relative laser and ruby-sample absorption frequencies by this technique of double-resonance spectroscopy is described. Under optical saturation conditions, additional temperature-dependent pumping effects occur at low temperatures. In particular, as the ruby temperature is increased from 4.2° to 40°K, the laser-induced change in EPR absorption is observed to undergo a large increase. This increase cannot be explained by a relative thermal shift of the laser and absorption frequencies which is known to be very small in this temperature range. The phenomena are attributed in part to the temperature-dependent homogeneous linewidth which determines the widths of the holes burnt into the inhomogeneous strain-broadened R lines. Calculations indicate that the related temperature-dependent thermalization process which redistributes excited Cr3+ among the 2E levels quantitatively accounts for most of the increase.
Recently, Boshier and Sandle1 predicted an unexpected and interesting phenomenon of the propagation of intense cw light through a strongly absorptive two-level medium: an enhancement of the on-axis intensity occurs with the laser frequency tuned to exact resonance with the atomic transition. Previously, cw self-focusing was thought to occur only on the high-frequency side of the resonance where nonlinear dispersion gives rise to an effective positive lens that focuses the entire beam,2,3 And indeed this cw on-resonance enhancement (CORE) arises from a different mechanism: the nonlinear absorption strips away the outer portions of the beam while diffraction of the light in the outer edge of the remaining core directs some of the beam toward the axis, resulting in near-field Fresnel fringes and CORE.
The real and imaginary parts of the complex index of refraction have been measured in the R1 line of optically pumped ruby. The experiments, which employed a temperature-controlled, single-mode ruby laser as a variable-frequency monochromatic source, were performed near liquid-nitrogen temperature, where the R1 doublet structure is well resolved. R1 absorption profiles were measured for several optical-pumping conditions, ranging from zero up to a pump power that excited a population in the 2E state equal to about 60% of the population of the 4A2 ground state. For each pumping condition, the anomalous-dispersion curve was measured interferometrically. The spectral profiles of the absorption coefficient and the anomalous dispersion display a dependence on the optical-pumping conditions that is more complicated than simple saturation of the R1 transitions, but for given pumping conditions the two quantities are correlated as predicted by the Kramers–Kronig relations.
This paper deals with the strongly nonlinear regime of the atom and field interaction which arises for both high cw input intensities and large absorption. The intensity of the light inside the medium is then highly nonlinear with respect to the incident one, the order of magnitude of the nonlinearity being approximately $\ensuremath{\alpha}1$, for a cell of length lll and an absorption length ${\ensuremath{\alpha}}^{\ensuremath{-}1}$. The transverse effects related to such a regime are analytically treated. They are shown to induce self-focusing, blooming, and also spatial ringing. These features strongly depend on the distance of the screen from the cell, on the detuning between the incident wavelength and that of the atomic transition, and on the input intensity. For self-focusing, analytical expressions of the focal point, of the waist, and of the maximum intensity are given. This model for transverse effects in strong nonlinear propagation of pulses would contribute to explain recent anomalous observations.