Question

A Nd microchip laser has an index of refraction 1.78 and a cavity length of 3.20 mm. Mirrors of reflectivity 0.997 and 0.975 are mounted directly on the faces of the chip. The emission line shape of the laser transition can be considered to be Lorentzian, with a line width of 4.80 THz.

a) Calculate the frequency spacing between modes of the laser and the frequency width of the modes.

b) Calculate the number of modes within the transition line width.

c) Given the loss coefficient of 0.4 m⁻¹ for the chip; calculate the gain coefficient at lasing threshold.

Answer 1

L= cavity length

α = loss coefficient

n= index of refrection

vf = transition line frequency

(a) frequency specing between modes of the laser

(b) number of mode

(c) gain coefficient of lasing threshold

α = loss coefficient  

are mirror reflectivity of laser