Question

For a cavity with gain 110 cm^-1 and loss 35 cm^-1 calculate the required length of the cavity to reach threshold, assuming total mirror loss of 0.4.

What is the restriction on the phase constant?

Answer 1

Let the length of the cavity be x.

The initial intensity be I

Then, the intensity after travelling a length x will be

So, the total gain of the medium will be

for a round trip.

Loss at mirror = 0.4.

So, for the cavity to be working properly,

Here,

G = 110 and L = 35

So,

The restriction in phase constant will be the linewidth of the cavity