GaN quantum technologies for defence and security

GaN laser diodes have the potential to be a key enabler for many quantum technologies that are crucial for defence and security, such as PNT (position, navigation and timing), quantum sensing, precision metrology, quantum communications and quantum computing, since the AlGaInN material system allows for laser diodes to be fabricated over a wide range of wavelengths from ultra-violet to visible. Furthermore, GaN allows the development of very high specification laser diode sources that are portable, robust and provide practical solutions that are otherwise unobtainable using more conventional laser sources. Novel applications for quantum technologies include GaN laser sources for cold-atom interferometry, such as next generation optical atomic clocks, quantum sensors and quantum metrology. Several approaches are taken to achieve the required linewidth, wavelength and power for cold-atom interferometry, including an extended cavity GaN laser diode (ECLD) system, and a distributed feedback (DFB) GaN laser diode with side-wall etched nano-gratings. We report the development of a generic passive waveguide photonic integrated circuit (PICs) platform for quantum applications that covers all the key cold-atom wavelengths for quantum sensing, including the 369nm cooling transition for Yb+, 422nm for Sr + and 461nm for Sr neutral.