Improvement of low pitch near-infrared semiconductor laser diode array performance

Quantum technology can leverage from various semiconductor laser solutions - depending on the technology, lasers can be used for excitation for quantum systems and quantum control of molecules. Examples of such quantum systems are single photon emitters, timing sources used for picosecond pulses, and frequency combs. Necessary performance parameters for such laser devices are single-mode operation, narrow spectral line width, and frequency stability over operation lifetime. Wavelength and optical output power of the diode laser devices can vary depending on the system. Narrow spectral linewidth with frequency stability can be achieved with distributed Bragg reflector (DBR) or distributed feedback (DFB) lasers with quarter-lambda phase shift is included in the grating, or with external cavities. In addition, efficiency of the systems can be improved when using laser diode arrays instead of single-emitter chips. Further improvement can be introduced by implementing individually addressable laser diode array operation (IAB). In this work, we present ways to improve our state-of-the-art low pitch laser diode array operation, within NIR wavelengths 780 to 930 nm. Emitter pitches as low as 20 mu m introduce complex interference and cross-talk phenomena that can appear as multiple transverse modes. These matters can be addressed with device design starting from the epitaxial structures, gratings, ridge waveguide optimizations up to facet coating of the arrays. Such arrays offer opportunities for dense device design and flexibility for end applications in, e.g., external cavity operating applications or silicon photonics.