Chen Yunyun

Integrating moiré and emission tomography to visualize and diagnose high-temperature flow fields

In this Letter, moiré and emission tomography are integrated to visualize and diagnose high-temperature flow fields, and a jet flame is chosen as a practical example for experiment. The refractive index and intensity distributions are simultaneously obtained by moiré and emission tomography, respectively. Based on the intensity distribution, the structure of the jet flame is well visualized, so that the spatial distribution of species composition can be considered in the temperature reconstruction process. Finally, the refractive index and intensity distributions are matched, and a partition model is adopted to reconstruct the temperature distribution of the jet flame.

Finite-size behavior near the critical point of QCD phase-transition

It is pointed out that finite-size effect is not negligible in locating critical point of QCD phase transition at current relativistic heavy ion collisions. Finite-size behavior near critical point, in particular, finite-size scaling and fixed-point behavior of the final observables can be served as a quantitative identification of critical point and the nearby boundary of the QCD phase transition. The validity of the method at finite detector acceptances at RHIC is discussed.

Subwavelength beam manipulation via multiple-metal slits coupled by disk-shaped nanocavity

A novel plasmonic structure consisting of three nano-scaled slits coupled by nano-disk-shaped nanocavities is proposed to produce subwavelength focusing and beam bending at optical frequencies. The incident light passes through the metal slits in the form of surface plasmon polaritons (SPPs) and then scatters into radiation fields. Numerical simulations using finite-difference time-domain (FDTD) method show that the transmitted fields through the design example can generate light focusing and deflection by altering the refractive index of the coupled nanocavity. The simulation results indicate that the focal spot is beyond the diffraction limit. Light impinges on the surface at an angle to the optical axis will add an extra planar phase front that interferes with the asymmetric phase front of the plasmonic lens, leading to a larger bending angle off the axial direction. The advantages of the proposed plasmonic lens are smaller device size and ease of fabrication. Such geometries offer the potential to be controlled by using nano-positioning systems for applications in dynamic beam shaping and scanning on the nanoscale.