A simple and highly reliable laser system for cold atom experiments

Optics Communications 290 110-114 (2013)
D. Sahagun, V. Bolpasi, and W. von Klitzing
http://dx.doi.org/10.1016/j.optcom.2012.10.013 (local link)

Abstract:

The increasing complexity of cold atom experiments puts ever higher demands on the stability and reliability of its components. We present a laser system for atom cooling experiments, which is extremely reliable yet simple to construct and low-cost, thus forming an ideal basis for ultracold atom experiments such as Bose-Einstein condensation and degenerate Fermi gases. The extended cavity (master) diode and slave lasers remain locked over a period of months with a drift in absolute frequency well below 1MHz with a line-width of less than 300kHz. We generate the repumper light by modulating the current of an injection locked slave laser at a frequency of 6.6GHz. The construction of the laser is simple and largely based on off-the-shelf electronic and optomechanical components.

Design

The basic idea of this laser system is to keep the individual elements modular, so that a fault in one part of the system can be repaired by only changing the sub-system with zero changes elsewhere.  Each parts in the graph on the right thus represents a separate bread-board.
The article also describes a very simple diode laser with extraordinary long term stability (depicted here on the right). This master-laser uses simply to machine parts and a commercial mirror mount for holding the grating.  The diode holder and mirror mount are screwed onto an aluminium base plate, which is glued onto a Peltier element, which in turn is glued onto a base.  The whole assembly is then surrounded by thick-walled aluminium box, which has been lined with standard isolation foam.

Another key element are the distribution and AOM breadboards.  They consist of standard 40mm kitchen-top granite plates cut to 300x600mm.  The optical mounts are 1” aluminium posts which are glued onto the base plate using cyanoacrylate adhesive (Loctite 408).  The beam hight is 50mm.

Supplementary Material:

– Layout of the AOM board (including alignment procedure) (link)
– Layout of the distribution board (including alignment procedure) (link)
– Electronics Diagramms (link)
– Technical drawings of the master laser (link)
– Technical drawings of the slave laser (link)