Context. Blazars are the most numerous class of high-energy (HE; E ∼ 50 MeV−100 GeV) and very (VHE; 100 GeV−10 TeV) gamma-ray emitters. Currently, a measured spectroscopic redshift is available for only about 50% BL Lacertae objects (BL Lacs), mainly due to difficulty in measuring reliable redshifts from their nearly featureless continuum-dominated optical spectra. The knowledge fundamental und...

The optical phased array (OPA) is an emerging non-mechanical device that enables high-speed beam steering by emitting precisely phase-controlled lightwaves from numerous antennas. In practice, however, it challenging to drive all phase shifters on OPA in a deterministic manner due the inevitable fabrication-induced errors and crosstalk between shifters. this work, we fabricate 16-element silico...

A chip-level optical beam steerer is an inevitable choice for next-generation light detection and ranging (LiDAR). The research on phased array (OPA) the most intriguing. However, complexity of control calibration speed limit full potential as number channels increases. In this paper, improved stochastic parallel gradient-descent algorithm combined with Nesterov accelerated gradient method (NSP...

We demonstrate a conceptually new mechanism for sub-wavelength focusing at optical frequencies based upon the use of nano-hole quasi-periodic arrays in metal screens. Using coherent illumination at 660 nm and scanning near-field optical microscopy, ~290 nm “hot spots”, were observed at a distance of ~12.5 μm from the array. Even smaller hot-spots of about 200 nm in waist were observed closer to...