Phase-Locked Lasers
Lasers are phase locked when there is a fixed phase difference between them. This can only occur when the lasers oscillate at exactly the same frequency and are optically coupled.
The locking condition can be directly observed in the interferometer image returned by the physical lab.
In a Locked State the interference phase is stable in time. Images integrated over the exposure time produce sharp, high-contrast fringes, and the phase is well defined.
In an Unlocked State The Interference state moves or fluctuates. The time integration images produce a smeared pattern with low contrast, phase may become unreliable.
Coupling and Detuning
To observe phase locking between lasers, they must be coupled. Without coupling, lasers evolve independently and will generally not lock.
When two lasers do not oscillate at the same frequency, they are said to be detuned.
Detuning prevents stable phase locking. In some configurations, the coupling itself can induce effective detuning under certain conditions.
Demonstration: Laser Pair Detuning Scan
To demonstrate phase locking and detuning behavior, we scan a phase parameter using thesolve_scan_lpu function.
Recommended Workflow
1. Set up a coupling matrix (coupmat) and a scan dictionary (scan_dic).
2. Run the scan in the physical lab.
note: This run may be lengthy because it consists of a sequence of experiments.
3. Inspect the returned image_problem_list as a time/scan series.
4. Plot the contrast versus scan step.
When the lasers are locked, the contrast remains high and stable.
When detuned, the contrast drops and the phase may become undefined.