A high-gain, distributed feedback (DFB), end-face emitting laser is fabricated in GaInAsP such that its effective guide index of refraction is 3.65. It has a first-order grating of periodicity = 1150...

A high-gain, distributed feedback (DFB), end-face emitting laser is fabricated

in GaInAsP such that its effective guide index of refraction is 3.65. It has a

first-order grating of periodicity = 1150 A and length 300 ˚ μm.

(a) What is the frequency of the lowest-order mode in rad/s?

(b) What is the mode spacing in rad/sec between the lowest-order mode and

the next higher-order mode?