Optical whispering gallery AndPI

1.

Optical whispering gallery mini-cavities for the determination of optical absorption,
scattering and acoustical losses in crystalline materials for future detectors.
A diamond lathe machine (designed for contact
lens industry) allows to prepare samples with
sub-nanometer resolution.
Coupling to high refractive WGM is challenging.
Semisphere coupler from the same material (Si) is a
solution.
Proof of the feasibility: Q=3x106 and coupling >10% is demonstrated on Si ball cavity (Q>1x108 for CaF2
disk cavity made by the lathe machine).

2.

Single mode cavity to avoid paramentic
instability in ET
Exiting elastic and Stokes
mode. Threshold effect.
Frequency sinchronizm
Too many possible optic
Stokes modes to participate in
PI
Solution: to thin out cavity
spectrum
Mirror's profile – not pure
spheric.
Intensity profile on mirror
slightly differ from Gaussian:

3.

Single mode cavity to avoid
parametric instability in ET (cont.)
Results:
Diffraction loss of Main mode
< 5 ppm
Losses of high order modes are larger
1000 ppm or even 10 000 ppm
Only one or two optic modes may
participate in parametric instability