Optimization and fabrication of 780 nm DFB lasers for quantum systems

Laser diode solutions for quantum systems have highly variable requirements, depending on the technology and purpose of the laser used in the application – for instance, quantum control of particles or molecules and excitation of the quantum systems. Requirements of the laser systems used in the mentioned applications are highly demanding, such as single-mode operation, frequency stability over operation lifetime and narrow spectral linewidth. Narrow spectral linewidth can be achieved with distributed Bragg reflector (DBR), distributed feedback (DFB) lasers and external cavities. Wavelength of laser diode and light output power can vary depending on the intended application. For further efficiency, such emitters can be fabricated in arrays, eliminating the need for multiple single-emitter chips. Individually addressability of the emitters further enhances the efficiency. Examples of different applications using laser diodes described earlier are frequency comb generation, single-photon emitters, and timing sources for picosecond pulses. In this work, we present our results in 780 nm region DFB laser diodes. Gratings were implemented within the structure, including overgrowth step. Multiple variants in grating pitch were introduced for structure and design optimization purposes. Future improvements in the device processing, design, and reliability are discussed. 780 nm region laser diodes are used in multiple quantum systems, such as atomic clocks and manipulation of Rb atoms. In addition, it can be used for terahertz wave generation.