Terahertz quantum cascade laser array with spatially-separated beams

A lens-coupled terahertz (THz) quantum cascade laser (QCL) array with multiple spatially-separated beams is presented. The beam divergence and focusing efficiency after lens are both investigated by simulations and experiments. By integrating an appropriate hyper-hemispherical silicon lens with a well-designed six-element distributed feedback (DFB) QCL array inside the cryostat window, excellent emission characteristics of small divergence angles from 4.1 degrees x3.5 degrees to 7.2 degrees x5.8 degrees and multi-wavelength spectra are realized at 77 K. The deflection angle between adjacent beams is - 10 degrees. The output intensity after lens is 113 to 25 times that of original beams with a focusing efficiency ranging from - 58% to - 37% for lasers at different positions. This method provides a simple solution to form a multi-beam THz source with high intensity and low far-field divergence.

Automated summary

By integrating a suitable lens with a well-designed QCL array, multiple spatially-separated beams with controlled divergence angles and focusing efficiency are achieved. This method demonstrates excellent emission characteristics and multi-wavelength spectra at 77 K temperature.