Second Harmonic Generation

How two photons at a fundamental frequency can produce a photon at a doubled frequency. The key is that birefringence in the host material is required.
(Sorry for the audio quality; my normal microphone wasn't working.)

[@PresCalvinCoolidge]

8:50-8:30. Why did you identify the ellipses as n_tilde instead of n_e (n extraordinary) for the in-plane polarization?

[@DESETFQRI]

gives sense

[@johnsonlam6901]

Are you saying no(w) and na(w,g) have five intersection points ? or a minimum of two, being 0, where na =nb = nc

[@ph_ahmedali2207]

Thanks sir❤️❤️