Injection locking and laser linewidth

Spontaneous emission and optical feedback influence the linewidth of semiconductor lasers. Linewidths of less than 1MHz are required for coherent optical communications.

self_hetero_setup

We utilise the delayed self-heterodyne method to determine laser linewidth, a key parameter to optimize for applications.
linewidth_laser  linewidth_lasertwo
 

The linewidth found are about 1 MHz for a single mode laser with cavity length of about 700 microns. For the Vernier laser, the linewidths are relatively broad, around 6 MHz, due to the high carrier densities in the mirror sections. Very good agreement is seen when comparing experiment and simulation.

 

Reference

Tuning behaviour of slotted vernier widely tunable lasers. Wallace, M. J.; Jain, Gaurav; Mckenna, Robert; Bello, Frank; Donegan, J. F. 2019  Optics Express 27(12) 17122-17137

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