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Weak temporal ratchet effect by asymmetric modulation of a laser
Cristina Elena Preda1, Bernard Ségard, Pierre Glorieux
1Laboratory de Physique des Lasers, Atomes et Molécules, CNRS (UMR 8523) CERLA, Universití de Lille I, 59655 Villeneuve d'Ascq, France.
Optics Letters
|July 13, 2006
Summary
Triangular laser modulation symmetry dictates pulse generation. Slow modulations can yield coherent pulses below threshold, unlike fast modulations, demonstrating a thermal ratchet-like effect.
Area of Science:
- Nonlinear dynamics
- Laser physics
- Quantum optics
Background:
- Lasers exhibit complex behaviors under external forcing.
- Modulation of pump sources can alter laser output.
- Stochastic fluctuations play a crucial role in nonlinear systems.
Purpose of the Study:
- To investigate the impact of triangular pump modulation symmetry on laser behavior.
- To explore the conditions under which coherent pulses are generated below the lasing threshold.
- To understand the role of fluctuations in modulation-induced phenomena.
Main Methods:
- Subjecting a laser system to triangular modulations of its pump source.
- Varying the symmetry and speed of the triangular modulation (slow vs. fast up-rising).
- Analyzing the laser output for the presence of coherent pulses in the presence of intrinsic fluctuations.
Main Results:
- Laser phenomena critically depend on the symmetry of the triangular modulation.
- Slow up-rising triangular modulations can induce coherent pulse emission from a laser operating below its average threshold.
- Fast up-rising triangular modulations do not produce coherent pulses under similar conditions.
- The observed effect requires the interplay of pump modulation and inherent system fluctuations.
Conclusions:
- The symmetry of external driving forces is a key parameter in nonlinear systems like lasers.
- A phenomenon analogous to the thermal ratchet effect can be observed in modulated lasers, extracting directed behavior from stochasticity.
- This work highlights a novel mechanism for controlling laser output and generating coherence via tailored modulation patterns.
