Statistical Properties of a Ring Laser with Injected SIgnal and Backscattering

The statistical properties of a homogeneously broadened ring laser with an injected signal are investigated and the normalized two-mode intensity auto- and cross-correlation functions are calculated by a full saturation laser theory with backscattering. The theoretical predictions are in good agreement with the experimental measurements.Further investigation reveals that the backscattering can reduce the fluctuations in the system while the full saturation effect plays a major role when the laser is operated above threshold. It is also quite important to notice that the injected signal can drive the weak mode from incoherent light to coherent light.

Enabling ultranarrow blue emission linewidths in colloidal alloy quantum dots by decreasing the exciton fine structure splitting and exciton–phonon coupling

The realization of colloidal alloy quantum dots(QDs)with narrow spectral linewidths requires minimization of the contributions of inhomogeneous and homogeneous broadening to the ensemble spectrum.Recently,there has been remarkable progress in eliminating the inhomogeneous contribution by controlling the size distribution of the QDs.However,considerable challenges remain in suppressing the homogeneous broadening,in terms of both intrinsic principles and rational synthetic routes.We find that ground-state exciton fine structure splitting and exciton-phonon coupling play a pivotal role in the homogeneous broadening mechanism.Here we demonstrate that the elimination of the lattice mismatch strain by using a coherent strain structure can decrease the light-heavy hole splitting,thus suppressing the asymmetric broadening of the emission on the high energy side.Besides,the improvement of the uniformity of the alloy by using a stepwise ion exchange strategy can weaken the exciton-longitudinal optical(LO)-phonon interactions,further minimizing the homogeneous broadening.As a result,the final alloy QD products exhibit a widely tunable blue emission wavelength(445-470 nm)with the narrowest ensemble photoluminescence full width at half maximum(FWHM)of 10.1-13.5 nm(or 58.4-75.3 meV).Our study provides a potential strategy for other semiconductor nanocrystals with ultranarrow spectral linewidths.