Copper tin sulfide (Cu 2 SnS 3 ) is a unique semiconductor, whose nanocrystals have attracted researchers' attention for its tunable energy bandgap and wavelength in visible and near infrared range. Quantum dots which are fabricated from this material are highly suitable for optoelectronics and solar cell applications. This paper discusses the tunable energy bandgap, exciton Bohr radius and wavelength range of wurtzite structure of Cu 2 SnS 3 quantum dots to assess the opportunity to use them in optoelectronics applications. The considerations show that the mole fraction of copper increases as energy bandgap decreases and tunable energy bandgap of this quantum dot material is inversely proportional to the wavelength.

High-speed vertical-cavity surface-emitting lasers (VCSELs) at different wavelengths present the backbone of high speed optical links showing large bandwidth density. The state of the art of present designs of VCSELs is summarized, including driving conditions. Several novel approaches for the design of GaAs-based VCSELs and VCSEL arrays are reported, potentially leading e.g. to lower power consumption, much larger single mode output and larger bandwidth. The first one is based on using the photon lifetime as a system sensitive optimization parameter. The second one reports for the first time details of a disruptively novel (patented) design based on oxidizing the apertures from multiple etched holes in varying arrangements and finally on multi-aperture designs in one device. These designs are essential for improving the energy-efficiency of modules by optimizing the interplay of electronic driver and photonic device.

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In this communication, we report on Cu2SnS3 quantum dots synthesized by the solvothermal process using different solvents. The optical properties of the quantum dots are analyzed by UV-Vis-NIR and photoluminescence spectroscopy. The results suggest that Cu2SnS3 material has tunable energy bandgap and appropriate wavelength for fabrication of light emitting diodes and laser diodes as sources for fiber optic communication. They exhibit wide absorption in the near infrared range. Further morphological studies with the use of atomic force microscope confirm the surface topography and the existence of quantum dots. The observed characteristics prove the efficiency of Cu2SnS3 quantum dots for O-band wavelength detection used in fiber optic communication and solar cell applications.