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

Dynamics of stimulated emission and coherent backscattering of light from amplifying random medium

Kam Sing Wong, Tong Sun, George K. Wong

Published Jan 1, 2002• 0 citations
OpenAlex

Abstract

We investigated random scattering of light in a disorder gain medium of ZnO powder using the pump-probe technique. Using a probe beam at (lambda) =390nm, the width ((theta) ) of the coherent backscattering peak from the ZnO powder is measured to be ~7.5 degree(s), thus the coherent scattering length l is approximately 1.2(lambda) ((theta) =(lambda) /2(pi) l) which is close to the strong scattering regime. When a pump beam ((lambda) =267nm) exceeds a certain excitation threshold, supernarrow emission peaks (bandwidth less than 1nm) emerged from the ZnO broad photoluminescence background. Concurrently, we also observed enhancement and sharpening of the coherent backscattering cone. Since light from the center of the backscatter cone experience the largest number of scatterings (i.e. longest gain length), this result is thus consistent with the random laser model that the supernarrow peak is due to amplification and stimulated emission of photon in the random gain medium. The time-resolved pump-probe measurement shows that the lifetime of the emission state above the lasing threshold is only a few picoseconds which is consistent with the interpretation that the supernarrow peaks are due to stimulated emission.

Related papers

Dynamics of stimulated emission and coherent backscattering of light from amplifying random medium

Kam Sing Wong, Tao Sun, George K. Wong

We investigated random scattering of light in a disorder gain medium of ZnO powder using the pump-probe technique. Using a probe beam at (lambda) =390nm, the width ((theta) ) of the coherent backscattering peak from the ZnO powder is measured to be ~7.5 degree(s), thus the coherent scattering length l is approximately 1.2(lambda) ((theta) =(lambda) /2(pi) l) which is close to the strong scattering regime. When a pump beam ((lambda) =267nm) exceeds a certain excitation threshold, supernarrow emission peaks (bandwidth less than 1nm) emerged from the ZnO broad photoluminescence background. Concurrently, we also observed enhancement and sharpening of the coherent backscattering cone. Since light from the center of the backscatter cone experience the largest number of scatterings (i.e. longest gain length), this result is thus consistent with the random laser model that the supernarrow peak is due to amplification and stimulated emission of photon in the random gain medium. The time-resolved pump-probe measurement shows that the lifetime of the emission state above the lasing threshold is only a few picoseconds which is consistent with the interpretation that the supernarrow peaks are due to stimulated emission.

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE•Jun 13, 2002•1 citation

Dynamics of random laser and coherent backscattering of light from ZnO amplifying random medium

T. Sun, Zhiren Qiu, Huimin Su +4 more

We investigated the dynamics of coherent backscattering cone and random laser in a disordered gain medium of ZnO powder. Theoretical fit to the coherent backscattering cone yields a transport mean free path l approximately equal to the probe wavelength λ, indicating that the scattering process is in the strong scattering regime. Supernarrow emissions from the laser are accompanied by enhancement and sharpening of the coherent backscattering cone. This enhanced and sharpened backscattering cone returns to a normal profile within 10–20ps, indicating an ultrafast gain lifetime in the medium, which is in good agreement with the time-resolved measurement of the random laser emissions.

Applied Physics Letters•Dec 10, 2007•11 citations

Generation of coherent light from a disordered medium

Hui Cao, Y. Ling, J.Y. Xu +2 more

Summary form only given. Over the past two decades, there has been much progress in the study of light transport in a disordered dielectric medium. Most studies are within the framework of ray optics or wave optics. Quantum statistical properties of light in a random medium have received little attention. To bridge the gap between random media and quantum optics, we conducted an experimental study of photon statistics of random lasers. ZnO nanoparticles with an average diameter of 80 nm are cold-pressed to form a pellet. In the coherent backscattering experiment, the scattering mean free path is measured The frequency-tripled output of a picosecond Nd:YAG laser is used to optically excite the ZnO pellet. The ZnO emission is measured by a spectrometer which is connected to a streak camera.

Quantum Electronics and Laser Science Conference•Nov 13, 2002•0 citations

Excitation-dependent diffuse super-reflection from a random laser

Ravitej Uppu, Sushil A. Mujumdar

Enhancement of the diffusive albedo from a random amplifying medium is discussed. A pump-probe setup is used to study the amplification of the reflected probe pulse light outside the backscattering cone. Strong super-reflection is measured and its dependence on the disorder strength is studied. An optimal disorder strength is observed at high excitation energy wherein the super-reflection is maximal. The origins of this behavior are traced to the interplay between the out-coupling and amplification from a disordered amplifying medium with an inhomogeneous distribution of gain.

Physical Review A•May 13, 2015•0 citations

Coherent Backscattering of Light from Amplifying Random Media

Diederik Sybolt Wiersma, Meint P. van Albada, Ad Lagendijk

We report on coherent backscattering measurements from amplifying random media using optically pumped Ti:sapphire powders. The top of the backscattering cone sharpens with increasing gain, reflecting a change in the relative contributions to the intensity from paths of different lengths. A calculation based on diffusion theory is performed on coherent backscattering from amplifying random media, which is in good agreement with the data.

Physical Review Letters•Aug 28, 1995•197 citations

Coherent backscattering from high-gain scattering media

Paulo C. de Oliveira, Amy E. Perkins, N. M. Lawandy

We report on experimental observations of coherent backscattering signals from high-gain scattering media in the regime where significant amplification takes place over one transport length. Our samples consist of polymer sheets containing optically pumped dyes as the amplifying medium, with TiO(2) nanoparticles providing the scattering. The width of the backscattering cones narrows with increasing amplification, while the enhancement factor remains unchanged.

Optics Letters•Oct 15, 1996•49 citations
We investigated random scattering of light in a disorder gain medium of ZnO powder using the pump-probe technique. Using a probe beam at (lambda) =390nm, the width ((theta) ) of the coherent backscattering peak from the ZnO powder is measured to be ~7.5 degree(s), thus the coherent scattering length l is approximately 1.2(lambda) ((theta) =(lambda) /2(pi) l) which is close to the strong scattering regime. When a pump beam ((lambda) =267nm) exceeds a certain excitation threshold, supernarrow emission peaks (bandwidth less than 1nm) emerged from the ZnO broad photoluminescence background. Concurrently, we also observed enhancement and sharpening of the coherent backscattering cone. Since light from the center of the backscatter cone experience the largest number of scatterings (i.e. longest gain length), this result is thus consistent with the random laser model that the supernarrow peak is due to amplification and stimulated emission of photon in the random gain medium. The time-resolved pump-probe measurement shows that the lifetime of the emission state above the lasing threshold is only a few picoseconds which is consistent with the interpretation that the supernarrow peaks are due to stimulated emission.
We investigated random scattering of light in a disorder gain medium of ZnO powder using the pump-probe technique. Using a probe beam at (lambda) =390nm, the width ((theta) ) of the coherent backscattering peak from the ZnO powder is measured to be ~7.5 degree(s), thus the coherent scattering length l is approximately 1.2(lambda) ((theta) =(lambda) /2(pi) l) which is close to the strong scattering regime. When a pump beam ((lambda) =267nm) exceeds a certain excitation threshold, supernarrow emission peaks (bandwidth less than 1nm) emerged from the ZnO broad photoluminescence background. Concurrently, we also observed enhancement and sharpening of the coherent backscattering cone. Since light from the center of the backscatter cone experience the largest number of scatterings (i.e. longest gain length), this result is thus consistent with the random laser model that the supernarrow peak is due to amplification and stimulated emission of photon in the random gain medium. The time-resolved pump-probe measurement shows that the lifetime of the emission state above the lasing threshold is only a few picoseconds which is consistent with the interpretation that the supernarrow peaks are due to stimulated emission.
We investigated the dynamics of coherent backscattering cone and random laser in a disordered gain medium of ZnO powder. Theoretical fit to the coherent backscattering cone yields a transport mean free path l approximately equal to the probe wavelength λ, indicating that the scattering process is in the strong scattering regime. Supernarrow emissions from the laser are accompanied by enhancement and sharpening of the coherent backscattering cone. This enhanced and sharpened backscattering cone returns to a normal profile within 10–20ps, indicating an ultrafast gain lifetime in the medium, which is in good agreement with the time-resolved measurement of the random laser emissions.
Summary form only given. Over the past two decades, there has been much progress in the study of light transport in a disordered dielectric medium. Most studies are within the framework of ray optics or wave optics. Quantum statistical properties of light in a random medium have received little attention. To bridge the gap between random media and quantum optics, we conducted an experimental study of photon statistics of random lasers. ZnO nanoparticles with an average diameter of 80 nm are cold-pressed to form a pellet. In the coherent backscattering experiment, the scattering mean free path is measured The frequency-tripled output of a picosecond Nd:YAG laser is used to optically excite the ZnO pellet. The ZnO emission is measured by a spectrometer which is connected to a streak camera.
Enhancement of the diffusive albedo from a random amplifying medium is discussed. A pump-probe setup is used to study the amplification of the reflected probe pulse light outside the backscattering cone. Strong super-reflection is measured and its dependence on the disorder strength is studied. An optimal disorder strength is observed at high excitation energy wherein the super-reflection is maximal. The origins of this behavior are traced to the interplay between the out-coupling and amplification from a disordered amplifying medium with an inhomogeneous distribution of gain.