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Quantum technologies containing key GaN laser components will enable a new generation of precision sensors, optical atomic clocks and secure communication systems for many applications such as next generation navigation, gravity mapping and timing since the AlGaInN material system allows for laser diodes to be fabricated over a wide range of wavelengths from the u.v. to the visible. We report our latest results on a range of AlGaInN diode-lasers targeted to meet the linewidth, wavelength and power requirements suitable for quantum sensors such as optical clocks and cold-atom interferometry systems. This includes the [5s2S1/2-5p2P1/2] cooling transition in strontium+ ion optical clocks at 422 nm, the [5s2 1S0-5p1P1] cooling transition in neutral strontium clocks at 461 nm and the [5s2s1/2 − 6p2P3/2] transition in rubidium at 420 nm. Several approaches are taken to achieve the required linewidth, wavelength and power, including an extended cavity laser diode (ECLD) system and an on-chip grating, distributed feedback (DFB) GaN laser diode.

We report on GaN lasers with extremely narrow linewidth (~1MHz) at ‘magic wavelengths’ for cold-atom quantum sensors and optical atomic clocks, using extended cavity GaN laser diodes and DFB GaN laser diodes.

We demonstrate a single wavelength operation from an InGaN/GaN distributed feedback (DFB) blue laser at 42X nm. The 39th order grating is etched in the sidewall to achieve single wavelength. The laser has a FWHM of ~ 25 pm at 500mA pulsed current with 15 mW output power.

A detailed study of the pump-intensity dependent characteristics of an all-inorganic CsPbBr3-in-Cs4PbBr6 quantum dot (QD) color converter are reported. This is an attractive material to color convert UV/blue GaN optical pump sources for digital lighting applications, e.g. visible light communications (VLC). It demonstrates narrow spectral emission (522 nm peak emission and < 20 nm full-width-at-half-maximum), invariant with the pump power density (from 0 to 7.15 kW/cm2). The optical bandwidth increases, from 10 MHz at 300 µW/cm2, up to 22 MHz at 3 W/cm2, and 41 MHz at 7.15 kW/cm2. This acceleration of the emission is ascribed to both an increase of the radiative decay rate in the low-pump-density regime, and to the emergence of non-radiative pathways at higher pump density. The higher bandwidth at high-pump density enables a 30% increase in the data rate of a free space VLC link using this color converter.

The implementation of spatial multiplexing has become an area of great interest for free-space communication links, particularly for its use in last-mile links within larger optical networks. Light carrying orbital angular momentum (OAM) has emerged as a potential candidate that could be utilised for multiplexing independent channels. We will present measured inter-channel crosstalk for a set of 11-OAM modes propagating through 3m of slowly flowing water, similar to that found in oceanic flow conditions

AlGaInN ridge waveguide laser diodes are fabricated to achieve single-mode operation with optical powers up to 100 mW at ∼420 nm∼420 nm for visible free-space, underwater, and plastic optical fiber communication. We report high-frequency operation of AlGaInN laser diodes with data transmission up to 2.5 GHz for free-space and underwater communication and up to 1.38 GHz through 10 m of plastic optical fiber.

The latest developments in AlGaInN laser diode technology are reviewed for defence and security applications such as underwater communications. The AlGaInN material system allows for laser diodes to be fabricated over a very wide range of wavelengths from u.v., ~380nm, to the visible ~530nm, by tuning the indium content of the laser GaInN quantum well. Thus AlGaInN laser diode technology is a key enabler for the development of new disruptive system level applications in displays, telecom, defence and other industries.