Unweaving the Rainbow

… and blinding us with science….

…in this case, one of two wildly complex light tables, with a setup to generate an extremely precise wavelength of infrared light.

For those unfamiliar with free-space optics, laser beams traverse the table bouncing off mirrors and through beam-splitting cubes. Non-linear photonic crystals of PPLN and acoustic phonon-mixers are used for wavelength shifting.

The system is on, but the beams are not visible. Looking through the handheld frequency-shifter (like night-vision goggles) allows us to observe beam scatter off less-than-perfect mirrors, and to see if any stray light or unanticipated ricochets are threatening our eyes (hence the eye protection policy in laser labs).

This is the light source for a laser atomic cooling trap on the adjacent light table. The trap laser has to be very precisely tuned in the infrared band to a doppler-red-shift from the resonant frequency of the trapped atoms (Rubidium in this case), so that any vibration toward the source is offset by a photon, thus arresting their motion, and cooling the atoms to about 100 microkelvin. To get all the way to 150nK (150 billionth of degree above absolute zero), they then switch off the Doppler cooling lasers and do evaporative cooling, typically in a pure magnetic trap.

This layout is the subject of Puzzle 94. The section in the rear reflects the compact order of design-in-advance, and the section in the foreground grew iteratively from there.