Extremely high temperature (220°C) continuous-wave operation of 1300-nm-range quantum-dot lasers

High temperature (>;125°C) resistant semiconductor lasers are attractive as light sources in a variety of harsh environments. Long-wavelength lasers operating under higher temperature of more than 200°C combined with silica-based optical fibers can expand application fields of data transmission and optical sensing to severe environments like space or deep underground. Temperature dependence of the threshold current of a semiconductor laser can be drastically reduced by employing quantum-dot (QD) active layers. Recent progress in epitaxial growth technology of QDs enhances the laser characteristics. Here, we report extremely high temperature continuous-wave (CW) operation up to 220°C of QD lasers emitted at 1300 nm-range for the first time by enhancing gain and increasing the quantized-energy separation of the QD active layers. Thus, QD lasers are proved to be suitable light sources for high temperature resistant applications.