Squeezer team

The mode matching solution on the green path from the SHG to the green fiber was changed (from SHGtoFiberOld.pdf to SHGtoFiberAM.pdf) to accommodate the small aperture AM (New Focus 4102).

With very low powers (<3mW, with a spot size of 200-500 um) we can get a Gaussian image on the beam profiler when viewed after a PBS (AOM7.png).

With 11mW (11mWnoPol.png) the profile is distorted and a Gaussian profile cannot be reliably recovered with alignment or polarization control, it seems to be some complex dynamic of heating and birefringence of the crystal is limiting us.

As a last resort we tried putting the AM at the focus hoping for a symmetric effect on each crystal in the modulator (AOM11mWfocus.png) with no improvement.

Note the intensity .36W/mm^2 (@11mW for 200um beam diameter) is below the limit (.5W/mm^2, and we should be able to operate at a 500um spot size I just wanted to be sure strange beam profile were not due to clipping or diffraction). The Rayleigh range is about a factor of two larger than required by the modulator (minimum Rayleigh range is the length of the crystal). We should be able to operate at a max of 100mW with a beam diameter of 500um and throw away half the power operating as a noise eater. This would give us give us a potential operational range of up to 50mW which we can attenuate down to 20mW before the fiber (or just operate at lower power, point is there should be lots of head room here).