The correct answer is: B. Higher than Brillouin threshold.
Stimulated Raman scattering (SRS) is a nonlinear optical process in which a light wave of a particular frequency (the pump wave) interacts with a medium to create a second light wave of a different frequency (the Stokes wave). The Stokes wave has a lower frequency than the pump wave, and its energy is taken from the pump wave.
The threshold for SRS is the minimum intensity of the pump wave required for the process to occur. The threshold depends on the material properties of the medium, such as its refractive index and Raman gain coefficient.
The Brillouin scattering is a type of light scattering that occurs when light interacts with acoustic waves in a material. The acoustic waves cause the refractive index of the material to change, which in turn causes the light to be scattered.
The threshold for Brillouin scattering is much lower than the threshold for SRS. This is because the acoustic waves are much more common than the Raman-active molecules that are required for SRS.
Therefore, the correct answer is: B. Higher than Brillouin threshold.
Here is a brief explanation of each option:
- Option A: Lower than Brillouin threshold. This is incorrect because the threshold for SRS is higher than the threshold for Brillouin scattering.
- Option B: Higher than Brillouin threshold. This is correct because the threshold for SRS is higher than the threshold for Brillouin scattering.
- Option C: Same as Brillouin threshold. This is incorrect because the threshold for SRS is higher than the threshold for Brillouin scattering.
- Option D: Higher than Rayleigh threshold. This is incorrect because the threshold for SRS is much higher than the threshold for Rayleigh scattering.