Coupled oscillators at a distance: applications to coupled semiconductor lasers

A theory for coupled oscillators is developed and applied to data for coupled semiconductor lasers. The theory generalizes much of the early work on this subject, as it includes the effects of time delays along the coupling path. By allowing for these time delays, additional degrees of freedom, or longitudinal modes are introduced in the coupled oscillator system. It is shown that quality phase locking requires that only one coupled-cavity mode be excited in the system, and that this limits the allowable levels of coupling to a range that extends from the minimum at which locking first occurs (the Adler condition) to a maximum coupling at which the lock begins to degrade; this latter level occurs only in oscillators coupled at a distance