We present the pulsed operation at room temperature of different strained InGaAs/ AlInAs quantum-cascade lasers grown by low-pressure metalorganic vapor-phase epitaxy. Devices based on a bound-to-continuum transition design have threshold current densities in pulsed mode as low as 1.84 kA/ cm 2 at 300 K. Identical lasers grown at higher rate ͑0.5 nm/ s͒ also have threshold current densities lower than 2 kA/ cm 2 at 300 K. Buried heterostructure lasers based on a double phonon resonance design were operated in continuous mode up to 280 K. Overall, the performance obtained from strained quantum cascade lasers deposited by metalorganic vapor-phase epitaxy are comparable with that of similar structures grown by molecular beam epitaxy.Quantum cascade lasers ͑QCLs͒ are the light source of choice for many potential applications such as gas sensing in the midinfrared. 1 State-of-the-art QCLs have indeed demonstrated large tunability, low-threshold, and high-power in continuous mode ͑cw͒ at room temperature. 2,3 The devices which exhibit the best performance have been so far grown by molecular beam epitaxy ͑MBE͒. This fabrication technique provides several advantages, such as the ease to form abrupt interfaces, but is not suitable for low-cost, high throughput production. On the contrary, low-pressure metalorganic vapor-phase epitaxy ͑MOVPE͒ is a well-established technology fitting the requirements of large scale production, especially since high growth rates are possible. 4-6 However, it is still necessary to demonstrate that MOVPE-and MBEgrown QCLs can have similar performance particularly since the control of interface abruptness is more challenging by MOVPE. QCLs fabricated using the latter technique have already been operated recently at room-temperature in pulsed mode. The threshold current densities for these latticematched devices were low, i.e., between 2.4 and 3 kA/ cm 2 at 300 K and the emission wavelength longer than 7.2 m. 4,6 Structures at shorter wavelengths require in order to achieve high performance at room temperature, the use of strainbalanced material because of the large band discontinuity available. 7 This letter reports on the fabrication of strained QC lasers grown by MOVPE working in pulsed mode above 320 K. Threshold current density as low as 1.84 kA/ cm 2 at 300 K and characteristic temperature T 0 close to 200 K were obtained from devices based on a bound-to-continuum design. Another sample based on a double phonon resonance
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 3ps (0.5pJ) were characterized by second-order autocorrelation.
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