Over the last few weeks I've gradually prepared the optics lab for the VOPO build.  The main task was to fiber couple the 1064 and 532 beams from the Prometheus.

For 532nm, the Prometheus has a waist 0.1 meters inside the laser head, I measured the horizontal waist as 78 um and the vertical waist as 62um.  The path has a half wave plate and PBS for power control, a couple of steering mirrors.  There is a PLCX-24.5-77.3-UV-532 lens (f = 154.7mm) placed 470mm from the laser head.  The fiber port thorlabs PAF-X-5-A is 710mm from the laser head.  This gives only a mediocre fiber coupling, 20%, but this is good enough for what we need. 

For 1064 nm, the waist of the Prometheus is also -0.1meters inside the laser head, I measured 122um for horizontal and 92um for vertical.  The path also starts with a half wave plate and PBS, then a PLCX-25.4-77.3-UV-1064 lens 0.26 meters from the laser head to form a waist for the New Focus 4004 broadband EOM at 0.53 meters from the laser head.  A PLCX-25.4-128.8-UV-1064 lens is 0.83 meters from the laser head to couple to the thorlabs PAF2-5C fiber port 2.2 meters from the laser head.  This is also mediocre coupling efficiency at 50%, but also good enough for what we need.

One of the things that we will be using these fiber coupled beams for is to couple IR light into the input/output coupler (M1) of the OPO to measure the escape efficency after we replace two of the cavity mirrors.  We plan to use a thorlabs F220FC-1064 collimator at LLO and LHO to make this measurement. I measured the mode out of the collimator using a the PC end of the patch cable, for horizontal I got a waist of 194um 1.15 meters behind the collimator, for vertical 215 um 1.3meters behind the collimator.