D-COLTS had two strands. A Ti:sapphire laser strand to de-risk and develop the 813 nm lattice laser required in a strontium neutral atomic system and a praseodymium-doped fluoride waveguide laser platform to de-risk and develop the 689 nm (and other red wavelengths) laser in a strontium neutral atomic system.

Project D-COLTS de-risked and progressed the development of laser systems required for strontium-based optical frequency standards to be used in the next generation of global positioning systems (GPS) and for precision metrology such as atom interferometry for gravitational field measurements. The laser systems require an increase in TRL in order to support future missions.

The Ti:Sapphire laser strand delivered average power of 570 mW, fiber coupling efficiency >75%, compact and rugged design (system volume 5.7l), prolonged locking stability and a 100 kHz linewidth in a TRL 4 package. Low-loss waveguides were demonstrated in praseodymium doped fluoride with transmission greater than 50% for a range of mode sizes 15- 20um demonstrating a suitable platform for laser operation.

The D-COLTS programme has de-risked two critical technologies required for strontium based frequency standards. These systems have shown a significant reduction in size weight and power over alternative approaches.

A further programmer of work is required to increase the laser systems to TRL 5/6 in order to secure flight opportunities and commercial opportunities terrestrial deployment.