Highly efficient surface-emitting semiconductor lasers exploiting quasi-crystalline distributed feedback photonic patterns

Abstract

Quasi-crystal distributed feedback lasers do not require any form of mirror cavity to amplify and extract radiation. Once implemented on the top surface of a semiconductor laser, a quasi-crystal pattern can be used to tune both the radiation feedback and the extraction of highly radiative and high-quality-factor optical modes that do not have a defined symmetric or anti-symmetric nature. Therefore, this methodology offers the possibility to achieve efficient emission, combined with tailored spectra and controlled beam divergence. Here, we apply this concept to a onedimensional quantum cascade wire laser. By lithographically patterning a series of air slits with different widths, following the Octonacci sequence, on the top metal layer of a double-metal quantum cascade laser operating at THz frequencies, we can vary the emission from single-frequency-mode to multimode over a 530-GHz bandwidth, achieving a maximum peak optical power of 240 mW (190 mW) in multimode (single-frequency-mode) lasers, with record slope efficiencies for multimode surface-emitting disordered THz lasers up to ≈570 mW/A at 78 K and ≈720 mW/A at 20 K and wall-plug efficiencies of η ≈ 1%.

Homogeneous quantum cascade lasers operating as terahertz frequency combs over their entire operational regime

“…The active region design of the homogeneous gain medium is a slightly modified version [22,23] of the four quantum well bound-to-continuum structures described in Ref. [24].…”

A Tunable Unidirectional Source for GUSTO’s Local Oscillator at 4.74 THz

“…In contrast to more optimized surface emitting DFB lasers [31][32][33][34][35], edge-emitting structures are inherently have better radiation efficiency in c.w. operation.…”

Physics and technology of Terahertz quantum cascade lasers

“…Photonic engineering, combined with new resonator concepts, has enabled the performance of THz QCLs to be designed with an incredible level of control, offering a flexible platform to tailor the emission spectrum, the beam profile and the output power, simultaneously. As a typical example, quasi-crystal THz lasers, loosening the distinction between symmetric and anti-symmetric modes allow circumventing the typical photonic crystals issue of power cancellation in the far-field, achieving a remarkably high power extraction (240 mW), ≈720 mW/A slope efficiency and good beam collimation (<10° divergence), both in single-mode and multimode regimes [40,41,105]. Very recently, random THz lasers (RLs) have been also successfully developed [106][107][108][109][110], in either 2D or 1D [109] geometries.…”

“…Alternatively, by exploiting a coupled-cavity architecture with a precisely positioned defect lattice that engineers the free spectral range and finesse of the cavity, and by employing Vernier selection rules, frequency tuning over 209 GHz has been demonstrated, including mode hop-free continuous tuning of ~6 − 21 GHz across Figure 8. Device pictures of disordered THz QCL resonators with a quasi-crystal structures implemented in a) 1D [105]or b) 2D [40] cavity geometry and c) picture of a random THz laser [110].…”