Broadband semiconductor lasers and their applications

Self-assembled semiconductor quantum dots (QDs) constitute a class of nanoscale materials that provide fundamental advantages compared to the dominating 2-D quantum well (QW) structures in photonic device applications. QD devices based on InAs/GaAs material system operating at emission wavelengths between 1.0 and 1.3 μm have achieved a relative maturity and many outstanding performances such as low threshold current, high temperature stability, high gain and differential gain, have already been demonstrated. For long wavelength operations in the S-C-L communication bands, particularly for the 1.55 μm window, the InAs/InP QD and quantum-dash (Qdash) material systems have been seen as the most suitable material system. Recent attempts in extending the technology of self- assembled QD on InP substrate has led to the development of InAs-based Qdashes that give the wavelength spans of ground state (GS) transition over several bands of optical telecommunication windows between 1.4 and 2.0 μm. Apart from its superior characteristics as compared to conventional quantum well structures and apart from its predominant applications in optoelectronics industry, self-assembled QD/Qdash lasers have demonstrated a number of unique features like broad emission spectra which have been attributed to the carrier localization in non-interacting or spatially isolated dot/dash employing a highly inhomogeneous QD/Qdash structures. These novel semiconductor light emitters are particularly attractive for novel many practical imaging and sensor applications due to their compactness and relatively low energy requirement in comparison to other state-of-the-art broad-spectrum light sources.