Effect of emitter number on quantum cascade laser monolithic phased array.

We present the optical analysis of spatial single-mode monolithic quantum cascade laser arrays in the mid-IR. Subwavelength parallel microstripe waveguides are buried into InP:Fe and phase locked by evanescent coupling. Lasing at room temperature is obtained at λ=8.

Passive coherent beam combining of quantum-cascade lasers with a Dammann grating.

An external cavity using a binary phase grating has been developed to achieve coherent combining of five quantum-cascade lasers emitting at 4.65 μm. The grating phase profile is designed to combine five beams of equal intensities into a single beam with a good efficiency (~75%).

Magnetotransport in quantum cascade detectors: analyzing the current under illumination.

Photocurrent measurements have been performed on a quantum cascade detector structure under strong magnetic field applied parallel to the growth axis. The photocurrent shows oscillations as a function of B. In order to describe that behavior, we have developed a rate equation model.

Phase seeding of a terahertz quantum cascade laser.

The amplification of spontaneous emission is used to initiate laser action. As the phase of spontaneous emission is random, the phase of the coherent laser emission (the carrier phase) will also be random each time laser action begins. This prevents phase-resolved detection of the laser field.

Coherent combining of two quantum-cascade lasers in a Michelson cavity.

We developed a Michelson-type cavity to achieve coherent combining of two quantum-cascade lasers, emitting at around 4.5microm. We report a cw combining efficiency of 85% (up to 91% near threshold) with good beam quality (M(2)<1.

Optical parametric amplification of a distributed-feedback quantum-cascade laser in orientation-patterned GaAs.

We demonstrate what is to our knowledge the first realization of an optical parametric amplifier in orientation-patterned GaAs amplifying the emission of a quantum-cascade laser (QCL) with a distributed-feedback (DFB) structure. We report a gain as high as 53 dB at 4.5 mum, in good agreement with theoretical calculations.

Phase-resolved measurements of stimulated emission in a laser.

Lasers are usually described by their output frequency and intensity. However, laser operation is an inherently nonlinear process. Knowledge about the dynamic behaviour of lasers is thus of great importance for detailed understanding of laser operation and for improvement in performance for applications.

Semiconductor waveguide source of counterpropagating twin photons.

We experimentally demonstrate an integrated semiconductor source of counterpropagating twin photons in the telecom range. A pump beam impinging on top of an AlGaAs waveguide generates parametrically two counterpropagating, orthogonally polarized signal/idler guided modes. A 2 mm long waveguide emits at room temperature one average photon pair per pump pulse, with a spectral linewidth of 0.