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Phase locking in a two-element laser array: a test of the coupled-oscillator model.

J Xu, S Li, K K Lee

|October 6, 2009

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Phase locking in Nd:YAG laser arrays occurs instantaneously, contrary to existing theories. This rapid, coupling-independent locking challenges current understanding of laser dynamics.

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Area of Science:

Optics and Photonics
Laser Physics
Nonlinear Dynamics

Background:

Phase locking is crucial for coherent operation of laser arrays.
Existing theories predict a gradual, coupling-dependent phase-locking process.
Understanding transient dynamics is key to controlling laser array behavior.

Purpose of the Study:

To investigate the transient dynamics of phase locking in a two-element Nd:YAG laser array.
To experimentally control and observe phase locking over a range of coupling strengths.
To compare experimental findings with predictions from time-dependent coupled-mode theory.

Main Methods:

Fabrication of two evanescent-coupled Nd:YAG lasers within an étalon.
Diode end-pumping to enable continuous variation of coupling strength by adjusting pump beam positions.
Observation and analysis of steady-state and transient phase-locking dynamics.

Main Results:

Phase locking develops as rapidly as lasing onset, without an evolutionary phase.
Instantaneous locking is observed and is independent of coupling strength above a threshold.
Experimental results contradict predictions from time-dependent coupled-mode theory.

Conclusions:

The instantaneous nature of phase locking in this Nd:YAG laser array challenges established theories.
Current models for laser array dynamics, particularly regarding optical instability, require reevaluation.
Further theoretical and experimental work is needed to fully explain these observed phenomena.