Broadly defining lasing wavelengths in single bandgap-graded semiconductor nanowires

Designing lasing wavelengths and modes is essential to the practical applications of nanowire (NW) lasers. Here, according to the localized photoluminescence spectra, we 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. 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 pre-defined lasing wavelength is realized in short NWs due to the strong mode competition and increase of FSR. Finally, the gain properties of the bandgap-graded NWs are investigated. The combination of wavelengths and modes selectivity in NW lasers may provide a new platform for the next generation of integrated optoelectronic devices.This work is supported by National Key Basic Research Program of China (No. 2013CB328703), National Natural Science Foundation of China (No. 51372220, 61177062, 61125402 and 51172004), the Fundamental Research Funds for the Central Universities, the Program for Zhejiang Leading Team of S&T Innovation and the Fundamental Research Funds for the Central Universities.This is the author accepted manuscript. The final version can be found on the publisher's website at: http://pubs.acs.org/doi/abs/10.1021/nl500432m Copyright © 2014 American Chemical Societ