Methods for adjusting feedback in terahertz lasers

Lateral distributed-feedback gratings for single-mode, high-power terahertz quantum-cascade lasers.

We report on terahertz quantum-cascade lasers (THz QCLs) based on first-order lateral distributed-feedback (lDFB) gratings, which exhibit continuous-wave operation, high output powers (>8 mW), and single-mode emission at 3.3-3.4 THz. A general method is presented to determine the coupling coefficients of lateral gratings in terms of the coupled-mode theory, which demonstrates that large couplin...

Nanowire terahertz quantum cascade lasers

Photonic quasi-crystal terahertz lasers

Quasi-crystal structures do not present a full spatial periodicity but are nevertheless constructed starting from deterministic generation rules. When made of different dielectric materials, they often possess fascinating optical properties, which lie between those of periodic photonic crystals and those of a random arrangement of scatterers. Indeed, they can support extended band-like states w...

Semiconductor lasers: Monolithic terahertz source

Twisted relativistic light pulses with a strong torque and an ultrahigh orbital angular momentum density can in principle be created by shining light pulses onto a specially design thin metal foil, report scientists in China. Theoretical analysis and simulations by Yin Shi and co-workers at the Shanghai Institute of Optics and Fine Mechanics predict that when intense pulses with planar wavefron...

A New Strategy for Choosing the Radius Adjusting Parameters in Trust Region Methods

Trust region methods are a class of important and efficient methods for solving unconstrained optimization problems. The efficiency of these methods strongly depends on the initial parameter, especially radius adjusting parameters. In this paper, we propose a new strategy for choosing the radius adjusting parameters. Numerical results from testing the new idea to solve a class of unconstrained ...