Chuan-Wei Liu

Phase-locked array of quantum cascade lasers with an integrated Talbot cavity

We show a phase-locked array of three quantum cascade lasers with an integrated Talbot cavity at one side of the laser array. The coupling scheme is called diffraction coupling. By controlling the length of Talbot to be a quarter of Talbot distance (Zt/4), in-phase mode operation can be selected. The in-phase operation shows great modal stability under different injection currents, from the threshold current to the full power current. The far-field radiation pattern of the in-phase operation contains three lobes, one central maximum lobe and two side lobes. The interval between adjacent lobes is about 10.5°. The output power is about 1.5 times that of a single-ridge laser. Further studies should be taken to achieve better beam performance and reduce optical losses brought by the integrated Talbot cavity.

Phase-locked array of quantum cascade lasers with an intracavity spatial filter

We show a phase-locked array of quantum cascade lasers with an intracavity spatial filter based on the Talbot effect. All the laser arrays show in-phase operation from the threshold current to full power current with a near-diffraction-limited divergence angle. The maximum power is just about 5 times that of a single-ridge laser for an eleven-laser array device and 3 times for a seven-laser array device. The structure was analyzed by using the multi-slit Fraunhofer diffraction theory, showing very good agreement with the experimental results. Considering the great modal selection ability, simple fabricating process, and potential for achieving continuous wave operation, this phase-locked array may be a hopeful solution to obtain higher coherent power.

Coupled Ridge Waveguide Substrate-Emitting DFB Quantum Cascade Laser Arrays

A coupled ridge waveguide substrate-emitting quantum cascade laser array operating at

Chirped coupled ridge waveguide quantum cascade laser arrays with stable single-lobe far-field patterns

\lambda \sim ~7\mu

Sample Grating Distributed Feedback Quantum Cascade Laser Array

m was presented. Fifteen elements were integrated in parallel to get high peak power and improved beam quality. The device was operating at fundamental supermode with a single-lobed far-field pattern. A narrow divergence angle of 2.9° in the ridge-width direction and 0.36° in the cavity-length direction were obtained by carefullydesigning the coupled ridge waveguide structure.Single-mode emission was observed by employing a buried second-orderdistributed-feedback grating. The peak power of the device was more than 2 W in pulsed operation at room temperature. This letter showed great potential to enlarge the output power of the surface-emitting devices while maintaining good beam quality.

Tapered Quantum Cascade Laser Arrays Integrated with Talbot Cavities

Power scaling in a broad area quantum cascade laser (QCL) tends to deteriorate beam quality with the emission of a multiple-lobe far-field pattern. In this paper, we demonstrate a coupled ridge waveguide QCL array consisting of five elements with chirped geometry. In-phase mode operation is secured by managing supermode loss with properly designed geometries of ridges. A single-lobe lateral far-field with a near diffraction limited beam pattern was obtained in the whole current dynamic range. The devices were fabricated with the wet and dry etching method. The regrowth technique of the InP:Fe insulation layer and InP:Si waveguide layer was employed. Such a structure has the potential to optimize the beam quality of the recently reported high-power broad-area QCL with a reduced cascade number.