In interferometry, spectroscopy, and holography, HeNe lasers or semiconductor lasers with external wavelength stabilization have been widely used to achieve the required narrow linewidth at 633 nm. Semiconductor lasers utilizing wavelength selective grating fabricated on semiconductor chip enable the miniaturization of laser systems while also providing numerous advantages such as low energy consumption, reliability and tunability by temperature and injection current. Moreover, DBR gratings reduce the complexity of the laser system compared to external cavity solutions where integration of multiple components is required. DBR gratings on semiconductor surface are fabricated without epitaxial regrowth step that could degrade the performance and lifetime of the device. In addition, low-order surface gratings are providing higher reflectivity than high-order gratings which could lead to a decreased emission linewidth and the output power. To this end, at red emission region low-order gratings require a small pitch, which in combination with the required etching depth for surface gratings leads to high aspect ratio gratings. In this work, Modulight demonstrates the fabrication of high aspect ratio low-order DBR surface gratings to optimize the device performance. DBR gratings are fabricated by electron beam lithography (EBL) method to achieve the required tight pitch patterns. EBL gratings are etched to AlGaAs or AlInP cladding layer using inductively coupled plasma reactive ion etching (ICP-RIE) to produce the desired high aspect ratio structures with smooth vertical side profiles. These two cladding materials are compared based on the etching profiles and device performance.
Glasses with the system (84.60-x) NaPO3-5 ZnO-(9.40-x) NaF-x Ag2O-1 Er2O3, (x = 0, 2, 4, and 6) (mol%) were synthesized by the conventional melt-quenching method. The impact of the addition of Ag2O on the physical, thermal, structural, and optical properties of the glasses is discussed. The Judd-Oflet analysis was used to evaluate the radiative properties of the emission transitions of the glasses. The enhancement of luminescence properties due to Ag2O is discussed in terms of consequent changes in the local electromagnetic field, symmetry, and the ligand field around the Er3+ ion. The heat treatment of the glass was performed in order to precipitate Ag nanoparticles (NPs), which form as a layer at the surface of the heat-treated glasses as confirmed using scanning electron microscopy (SEM). The Ag NPs were found to increase the intensity of the emission at 1.5 µm.
The impact of the progressive addition of ZnO up to 5 mol% on the thermal, structural, and optical properties of Er3+-doped phosphate glasses within the system NaPO3-NaF-ZnO-Ag2O is discussed. The glass network was found to depolymerize upon the addition of ZnO. This promotes a slight increase in the intensity of the emission at 1.5 µm as well as enhances the silver ions clustering ability under the heat treating. The Ag-nanoparticles formed after moderate heat-treatment can further enhance the emission at 1.5 µm, whereas an excessive amount of the clusters leads to the opposite effect. The addition of ZnO helps to slightly increase the glass ability of the system. The crystallization behavior study revealed that surface crystallization is observed for all the glasses. It is found that even a small ZnO addition changes the crystalline phases formed after devitrification. Moreover, the addition of ZnO decreases the crystallization tendency of the glass.
Laser diode solutions for quantum systems have highly variable requirements, depending on the technology and purpose of the laser used in the applicationfor 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.
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