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A mode-locking mechanism by active gain modulation is studied numerically and experimentally. The parameter window for the emission of stable pulse trains was found. Pulses as short as 3 ps (~0.5 pJ) were characterized by second-order autocorrelation.
We present a theoretical assessment of two open-path quantum cascade laser (QCL) approaches (mono/bi-static and backscatter) to measure ambient ozone and ammonia concentrations to within 1-10% accuracy at distances up to 10 km.
A quantum-cascade laser design for suppressing carrier leakage from the active region was achieved. For both threshold and slope efficiency the characteristic temperatures, T0 and T1, reach values of 238 K over the 20-60degC range.
The optical gain dynamics in an InGaAs/AlInAs quantum cascade laser is studied by midinfrared pump-probe experiments and electro-optic sampling. We find an extremely fast gain recovery time of <1 ps.
We demonstrate the inhomogeneous character of interface roughness broadening in intersubband transitions and analyze its impact on temperature dependence of the gain and absorption spectra in the quantum cascade laser.
We model the phase coherence of multi-transverse modes of buried-heterostructure quantum cascade lasers. The experimentally observed transverse mode locking and beam steering are explained by four-wave mixing of longitudinal modes belonging to different transverse modes.
An all-fiber-integrated supercontinuum laser having time-averaged power scalable up to 10.5 W with diffraction limited beam quality is demonstrated. The SC pulses can be generated with arbitrary modulation patterns having on/off durations as short as 10 muS.
Surface waves on metal films with subwavelength features and tunable optical resonances are excited with a quantum cascade laser. The resulting transmission through, and propagation on, the metal/dielectric interface is measured, both spectrally and spatially.
We demonstrated an array of distributed feedback quantum cascade lasers covering a spectral range of 220 cm-1. The variability in threshold current and slope efficiency is explained in terms of the position of the laser end facets.
A density-matrix based theory of transport and lasing in quantum-cascade lasers reveals that large disparity between lasing linewidth and tunneling broadening changes the design guidelines to favor strong coupling between injector and upper laser level.
We report on the high frequency modulation of terahertz (THz) quantum cascade lasers (QCLs). By resonantly enhancing the frequency response of the RF biasing circuit we show that 4 mm and 1.5 mm-long metal-metal waveguide 2.3 THz QCLs, can be modulated up to 21 and 24 GHz respectively.
A widely tunable, external cavity quantum cascade laser was used in the deployment of an open-path sensor for the measurement of water vapor, ozone, ammonia, and carbon dioxide in the urban atmosphere of Beijing, China.
We calculate intersubband absorption loss and report measured waveguide loss for two high-performance mid-infrared quantum cascade laser designs. Intersubband absorption loss accounts for a major component of waveguide loss for these structures.
We report an efficient technique to measure gain and losses of quantum cascade lasers (QCLs). It consists on the analysis of the Fabry-Perot fringes induced by the optical injection of a chirped distributed feedback QCL.
We demonstrate a novel four-well injectorless design with short wavelength (5.5 mum) and room temperature operation utilizing highly strained Ga0.35In0.65As/Al0.70In0.30As (0.8/-1.5%) quantum wells.
We demonstrate a Quantum Cascade Laser employing ultra-strong (~20 meV) coupling between the injector and the upper laser state. The laser shows a pulsed wall-plug efficiency of 34%(8%) and peak power of 8.0 W(2.0 W) at 80 K(300 K).
Mid-infrared beam shaping is demonstrated by using grating coupled surface emitting quantum cascade ring lasers. The devices allow for far-field tuning, ranging from highly symmetric spot-to ring-shaped beam patterns, depending on the grating period.
We report operation of v ~ 2.7 THz quantum-cascade lasers (QCLs) up to 174 K. A new three-well active region, one-well injector scheme is utilized to lower the operating current densities. While the temperature performance of this design is comparable to that of the best published THz QCLs, lower operating current densities make this design a viable alternative.
We demonstrate a new technique for fine tuning of optical delays using cascaded acousto-optic modulators. A 256-ns delay with <0.5-ps resolution is shown for 40-Gb/s RZ-OOK with no system penalty.
We have designed, fabricated and measured a first generation external modulator for a ~2.4 terahertz quantum cascade laser based on an electrically-driven active terahertz metamaterial structure.
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