A simple and novel method to obtain an FSR free silicon ring resonator

A simple and novel method to make a silicon ring resonator without the limit of free spectral range (FSR) is presented. For many applications, a ring resonator is desired with an ultra-wide FSR, a high quality factor, a large extinction ratio and low-fabrication complexity. In this paper we propose a novel method to obtain such a ring resonator, which is a single all-silicon micro-ring with a FSR as large as 150 nm around 1550 nm. It's based on the well-known phenomenon of resonance splitting

Renormalization group improved predictions for ttˉW±t\bar{t}W^\pm production at hadron colliders

We study the factorization and resummation of the $t\bar{t}W^\pm$ production at hadron colliders. The cross section in the threshold limit can be factorized into a convolution of hard and soft functions and parton distribution functions with the soft-collinear effective theory. We calculate the next-to-leading order soft function for the associated production of the heavy quark pair and colorless particle, and we perform the resummation calculation with the next-to-next-to-leading logarithms accuracy. Our results show that the resummation effects reduce the dependence of the cross section on the scales significantly and increase the total cross section by $7-13\%$ compared with NLO QCD results.Comment: 23 pages, 7 figures and 2 tables; final version in PR