Broadly Defining Lasing Wavelengths in Single Bandgap-Graded Semiconductor Nanowires

As the core elements in nanophotonics, micro-/nano light emitting devices have great potential applications in high density optoelectronics, high sensitive sensing and high resolution imaging systems, which have attracted a lot of interests in the past decades. While for their practical applications, control and optimization of the parameters are of great significance. In 2013,Prof. Qing Yang’s group firstly utilized absorption-emission-absorption(AEA) process to achieve wavelength tailoring (40 nm) on a single non-doped CdSe NW. Recently, according to the localized photoluminescence spectra, they first demonstrate the ability to define lasing wavelengths over a wide range (up to 119 nm) based on an individual bandgap graded CdSSe NW by forward cutting the NW from CdSe to CdS end. The variable spectral range covers red and green colors. Furthermore, free spectral range (FSR) and modes of the obtained lasers could be controlled by backward cutting the NW from CdS to CdSe end step-by-step. Interestingly, single-mode NW laser with predefined lasing wavelength is realized in short NWs because of the strong mode competition and increase in FSR. The combination of wavelength and mode selectivity in NW lasers may provide a new platform for the next generation of integrated optoelectronic devices.