Gallium nitride laser development for optical atomic clock applications

This work explores the design and fabrication of gallium nitride (GaN) lasers for use in optical atomic clocks. Software allows the laser material and grating structures to be modelled, and devices have been fabricated in the cleanroom based on this. Currently, many atomic clock systems use large, expensive lasers which are frequency doubled, and coupling requires lots of benchtop optical components. A distributed feedback (DFB) laser is one option to realise a compact source which can hit the specifications required for the atomic cooling process. Grating structures have been designed to produce single mode performance at key wavelengths in the blue part of the spectrum. Development of the etching process and metal deposition are being optimised to ensure the best quality lasers are produced. These devices can then be used for the cooling of atoms in optical atomic clocks, taking what is currently a lab scale technology to something which is much more compact. Single mode GaN lasers with high output power and narrow linewidth have been realised for this purpose. Other laser structures, such as surface emitting devices are also being considered. National Physical Laboratory are developing a compact ion trap and vibrationally insensitive cubic cavity which along with these compact lasers, will lead to a portable optical atomic clock.