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Probing localized states with spectrally resolved speckle techniques.
1Department of Physics and Astronomy, Northwestern University, Evanston, Illinois 60208, USA.
Physical Review. E, Statistical, Nonlinear, and Soft Matter Physics
|September 21, 2002
Summary
Researchers used speckle correlation to study localized states in random media. They found these states have an exponentially decaying spatial extent, even below the localization threshold.
Area of Science:
- Condensed matter physics
- Wave phenomena in disordered systems
- Photonics and optics
Background:
- Localized states in random media are crucial for understanding wave transport.
- Speckle correlation techniques offer insights into the spatial properties of light fields.
- Inducing optical gain can reveal the nature of these localized states.
Purpose of the Study:
- To investigate the spatial extent of localized states in random media.
- To utilize optical gain and lasing to probe localized states.
- To determine the correlation function of laser emission from localized states.
Main Methods:
- Speckle correlation techniques were employed to analyze light emission.
- Optical gain was introduced to a localized region of the random medium.
- Far-field speckle patterns were measured to obtain spatial field correlation functions.
Main Results:
- The spatial field correlation function's envelope decays exponentially with transverse distance.
- The decay length of the correlation function is independent of pumping rate and excitation area.
- Localized states were observed in disordered systems below the localization threshold.
Conclusions:
- Localized states in random media exhibit a well-defined spatial extent characterized by exponential decay.
- The observed decay length provides a metric for the spatial confinement of these states.
- The findings confirm the existence of localized states in disordered systems even before reaching the full localization threshold.