Covesion SFG Crystals for Laser Cooling and Trapping

Covesion’s range of MSFG crystals are most commonly used in quantum optics systems where narrow linewidth lasers are needed to access specific atomic transitions in order to manipulate and cool atoms and ions. Cooling lasers with Watt level powers are readily achievable by using high power fibre pump lasers for sum frequency generation in MgO:PPLN.

For example, the MSFG626 can be used for cooling Beryllium ions from two pump lasers at 1051nm and 1550nm which are then combined in the MSFG626, generating 626nm. This output is can then be frequency doubled to a ⁹Be⁺ ion transition at 313nm using a BBO crystal [1,2]. Similarly, our MSHG637 has been used to demonstrate cooling of Caesium atoms from 1560nm and 1077nm to 637nm, which is then frequency doubled to an atomic transition [3]. Our full range of MSFG crystals is shown below.

To achieve efficient SFG, you ideally want the two pump beams to be confocally focussed into the PPLN (i.e. ratio of the crystal length to the confocal parameter is 1) and for both beams to be roughly equal in power. Note that for high power beams, a looser focus is recommended, avoiding back-conversion or crystal damage.

For generation of 626nm light from 1051nm and 1551nm, efficiencies of 3.5-2.5%/Wcm have been achieved [1,2]. Here, the efficiency η, is defined by

Where P is the power at each wavelength, and l is the crystal length. Lo et al. demonstrated an efficiency of 44% for the generation of 7.2W of 626nm light from 1051nm (8.5W) and 1551nm (8.3W) [1]. Here they used a 40mm long, 0.5mm thick crystal at 180C with a 58μm spot size (1/e2 radius). Further examples and technical details are summarised in the table below of some selected publications.

References

[1] H.-Y. Lo et al., Applied Physics B, doi:10.1007/s00340-013-5605-0, (2013)
[2] A. C. Wilson et al., Applied Physics B, vol. 105, no. 4, pp. 741 – 748, (2011)
[3] J. Wang et al., Optics Communications, vol. 370, pp. 150–155, (2016)

• Share