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Measurement of Hurst exponents for semiconductor laser phase dynamics
Wing-Shun Lam1, Will Ray, Parvez N Guzdar
1Department of Physics, University of Maryland, College Park, Maryland 20742, USA and IREAP, University of Maryland, College Park, MD 20742, USA.
Physical Review Letters
|February 9, 2005
Summary
We analyzed semiconductor laser phase dynamics using Hilbert phase analysis. Increased optical feedback strengthens fractional Brownian motion in phase fluctuations, aligning with theoretical models.
Area of Science:
- Nonlinear dynamics
- Laser physics
- Optical engineering
Background:
- Semiconductor lasers are crucial for modern optics.
- Optical feedback can significantly alter laser dynamics.
- Understanding phase dynamics is key to laser stability and performance.
Purpose of the Study:
- To investigate the phase dynamics of semiconductor lasers subjected to optical feedback.
- To quantify phase fluctuations using the Hurst exponent.
- To compare experimental findings with theoretical models.
Main Methods:
- Experimental measurement of laser intensity time series.
- Construction of the Hilbert phase from intensity data.
- Evaluation of the Hurst exponent for phase fluctuations.
- Numerical simulations using a delay-differential equation model.
Main Results:
- The Hurst exponent for phase fluctuations increases with optical feedback strength, ranging from 0.5 to approximately 0.7.
- This increase indicates a transition towards fractional Brownian motion.
- Experimental results show excellent agreement with numerical computations.
- The study elucidates the interplay between spontaneous emission noise and deterministic dynamics.
Conclusions:
- Hilbert phase analysis is effective for studying semiconductor laser dynamics.
- Optical feedback induces more complex, persistent phase dynamics.
- The findings validate theoretical models and provide insights into laser noise and deterministic behavior.