Nick Brewer: Difference between revisions

 

Been trying to see EIT. No luck yet.

 

There is around 1.3 W of 527 nm light coming out of the SHG cavity. The beam goes through one beam splitter and as much light as possible is reflected, the remaining transmitted light is enough for the repump beam. The next beam splitter again reflects as much light as possible, this reflected beam goes to the control beam AOM. The remaining transmitted light through the second beam splitter is enough for the probe and goes to an AOM in a double pass configuration (so if I sweep out a spectral hole 20 MHz wide, the RF generator only sweeps over a 10 MHz range).

 

The control and repump beam are coupled into the same fiber using a polarizing beam cube and a polarization maintaining fiber. The output of the fiber is sent through a glan taylor polarizer and a 1/2 wave plate. The probe is also sent through a fiber with a glan taylor and 1/2 wave plate at the output. The two beams are directed parallel to each other, but horizontally displaced by ~3/4 inches, and sent through a 200 mm lens so that they focus and overlap each other in the crystal. This geometry is used so that the probe can be separated from the control/repump beams. There is another 200 mm lens on the other side of the crystal to recollimate the beams.

 

Right RF2 is on all the time. I start by sweeping out a 20 MHz wide spectral hole for 5 seconds with the probe beam at the max RF power (+5 dBm for the current RF generator and amplifier). Then for one second I turn on the control beam at -30 dBm. At this point a spectral hole should be swept out and a backburned population with width of ~2 MHz should be in the middle of the trough.