No abstract

We report on highly reproducible low-loss fusion splicing of polarization-maintaining single-mode fibers (PM-SMFs) and hollow-core photonic crystal fibers (HC-PCFs). The PM-SMF-to-HC-PCF splices are characterized by the loss of 0.62 +/- 0.24 dB, and polarization extinction ratio of 19 +/- 0.68 dB. The reciprocal HC-PCF-to-PM-SMF splice loss is found to be 2.19 +/- 0.33 dB, which is caused by the mode evolution in HC-PCF. The return loss in both cases was measured to be -14 dB. We show that a splice defect is caused by the HC-PCF cleave defect, and the lossy splice can be predicted at an early stage of the splicing process. We also demonstrate that the higher splice loss compromises the PM properties of the splice. Our splicing technique was successfully applied to the realization of a low-loss, environmentally stable monolithic PM fiber laser pulse compressor, enabling direct end-of-the-fiber femtosecond pulse delivery.

No abstract

Cluster expansions are simplified, Ising-like models for binary alloys in which vibrational and electronic degrees of freedom are coarse grained. The usual practice is to learn the parameters of the cluster expansion by fitting the energy they predict to a finite set of ab initio calculations. In some cases, experiments suggest that such approaches may lead to overestimation of the phase transition temperature. In this work, we present a novel approach to fitting the parameters based on the relative entropy framework which, instead of energies, attempts to fit the Boltzmann distribution of the configurational degrees of freedom. We show how this leads to T -dependent parameters.

No abstract