The excitation power dependence of the ground and excited state transitions in type-II InAs-GaAs0.78Sb0.22 quantum dot structure has been studied. Both transitions exhibit a strong blueshift with increasing excitation power but their separation remains constant. This behavior indicates a carrier-induced electric field oriented predominantly along the growth axis, which requires the holes to be localized in the GaAsSb above quantum dots. An accelerated blueshift of the ground state emission is observed once the excited state in the dots starts to populate. This behavior can be explained by a smaller spontaneous recombination coefficient for the excited state transition.
In order to identify the performance limitations of InGaAs/ AlAs(Sb) quantum cascade lasers, experimental investigations of the temperature and pressure dependencies of the threshold current (I th ) were undertaken. Using the theoretical optical phonon current (I ph ) and carrier leakage (I leak ) to fit the measured threshold current at various pressures, we show that the electron scattering from the top lasing level to the upper L-minima gives rise to the increase in I th with pressure and temperature. It was found that this carrier leakage path accounts for approximately 3% of I th at RT and is negligible at 100 K.
We report on the development of strain compensated InGaAs/AlAs(Sb) quantum cascade lasers, incorporating a buried third order distributed feedback grating. Single mode operation with a side mode suppression ratio of ∼30 dB has been achieved in the wavelength range of 3.358–3.380 μm for temperatures between 270 and 360 K. The threefold increase in grating pitch size, compared with a first order grating, allows conventional photolithographic techniques to be used for single mode laser fabrication.
We report on distributed feedback quantum cascade lasers at a wavelength of 3.58 µm operating at room temperature. Single-mode emission with a side-mode suppression ratio of 30 dB is achieved by manufacturing single-sided third-order lateral gratings. The devices exhibit watt level peak powers with a threshold current density of ∼ 4.3 kA/cm 2 at room temperature and remain in single-mode operation over the temperature range of 280-420 K.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.