Optical resonators and Gaussian beams
Spectral distribution of the longitudinal modes
We have an He-Ne laser, with a 20 cm long cavity, lasing at 632,8 nm.
Question
What is the frequency (and wavelength) gap between two consecutive longitudinal modes ?
Question
We want to use a spectral filter with a bandwidth of 1 nm. What value shoud we choose for the cavity length to select one (and only one !) longitudinal mode with this filter ?
