Polarization insensitive self-collimation waveguide in square lattice annular photonic crystals

We propose a two-dimensional photonic crystal of rectangular symmetry with rather straight iso-frequency lines over the whole first Brillouin zone along theX direction to realize all-angle self-collimation. By tracking the spatial evolution and transmission efficiency of the collimated beam along the propagating direction, it is found that the beam spreading and propagation loss are negligible for incident angles within ±85 ◦ . The self-collimating behaviors in the rectangular and square lattices are compared and the differences between them are investigated. As an application, a Y-shaped beam splitter with transmission efficiencies for both branches as high as 43.8% is constructed by combining two rotated rectangular structures.

https://iopscience.iop.org/article/10.1088/1464-4258/10/8/085201/pdf

The all-angle self-collimating phenomenon in photonic crystals with rectangular symmetry

An efficient backbone is introduced for optical integrated circuits at Mid-IR region using PbTe ( n PbTe  ∼ 6) as the background material in a hole-type 2D square lattice photonic crystal in this article. The proposed waveguide benefits insensitivity to the polarization and is also virtually all-angle. Furthermore, it is applicable to a broad spectral width of 30 nm considering only a small compromise of 3° on the degree of self-collimation which will not cause a significant challenge in practical integrated applications. Here, based on finite difference time domain analysis, a complete study on coupling efficiency of the introduced structure is presented. It is shown that for optimized anti-reflection, the structure benefits a coupling efficiency of ∼70% for TE and TM polarizations around the central wavelength of λ  = 4.1175 μm. In this study, a single row of hole-type anti-reflection is used which does not affect the all-angle SC property of the proposed waveguide.

Highly efficient self-collimation based waveguide for Mid-IR applications

https://onlinelibrary.wiley.com/doi/pdf/10.1002/andp.201700049

Self‐Collimation in Photonic Crystals: Applications and Opportunities

Emission sensitization processes involving Nd3+ in YAG

A recyclable energy cycle using a pulsed laser and base-metal nanoparticles is proposed In this energy cycle, iron nanoparticles reduced from iron oxides by laser ablation in liquid are used for hydrogen generation The laser energy can be stored in the base-metal nanoparticles as the difference between the chemical energies of iron oxide and iron According to the results of an experiment on hydrogen production using the reduced iron nanoparticles, the reaction efficiency of the hydrogen generation at a temperature of 673 K was more than 94% for the ideal amount of generated hydrogen

https://downloads.hindawi.com/archive/2013/827681.pdf

Hydrogen Production Using Reduced-Iron Nanoparticles by Laser Ablation in Liquids

This paper investigates the optical characteristics of a light-focusing device (LFD) consisting of two-dimensional (2-D) photonic crystals (PCs) configured in a parallelogram lattice structure. The LFD is composed of two jointed symmetric PCs that have a strong self-collimation effect. This self-collimation effect focuses the incident light wave. For a square lattice, however, in which the equi-frequency contours have fourfold symmetry (/spl pi//2 rotation symmetry), the band structure needed to realize an LFD was not obtained. The proposed solution was to consider the parallelogram lattice arrangement since its equi-frequency contours do not have /spl pi//2 rotation symmetry; a prototype LFD composed of 2-D PCs with parallelogram lattice structure exhibits desirable focusing performance. The authors also investigate the asymmetry of light wave transmission through the LFD. Finite-division time-domain (FDTD) simulations of the optical property of the LFD show that the LFD has distinct transmission asymmetry.

Study on self-collimated light-focusing device using the 2-D photonic crystal with a parallelogram lattice

An increase in the effective fluorescence lifetime of Nd/Cr:YAG ceramics with temperature dependence was observed. The dependence on the doped Cr ion density for the increased effective fluorescence lifetime was also investigated. The effective lifetime of fluorescence in the ceramics increased from 1.1 to 1.8 ms owing to the phonon-assist cross-relaxation induced by the excited Cr ions, which is commonly observed in Tm:YAG or glass lasers. The increase in effective fluorescence lifetime can be explained by spontaneous emissions occurring from the excited Nd ions and excitations of the Nd ions from the lower level to the upper level at the same time. Additionally, an experiment for laser oscillations with the temperature of the laser material controlled was performed, and a remarkable increase of the output laser energy owing to cross-relaxation was observed when the temperature increased. The obtained maximum laser energy output was near twice that without cross-relaxation. The ceramics are considered promising lamp- or solar-pumped solid-laser materials owing to the efficient laser action based on this cross-relaxation.

https://www.worldscientific.com/doi/pdf/10.1142/S1793528813500032?src=recsys

INCREASE IN EFFECTIVE FLUORESCENCE LIFETIME BY CROSS-RELAXATION EFFECT DEPENDING ON TEMPERATURE OF Nd/Cr:YAG CERAMIC USING WHITE-LIGHT PUMP SOURCE

Research on the produce of re ne wable e ne rgy as a source of solar powe r has continuously ad vance d We have propose d an en ergy cycle that uses solar- pumpe d pulse lase rs and base me tal nanoparticles He re , Fe and Al nanoparticles we re pre pare d by lase r ablation in liquid for the e nergy cycle  Solar powe r was confine d in base me tal nanoparticles Me ta l plates we re fabricate d by sinte ring metal paste with base me tal nanoparticles Electricity was ge ne rate d by air ce lls using the sintere d me tal plate  A highly re pe titive laser pulse , which was an alte rnative to lasers drive n by solar power, was use d for laser ablation in liquid, and me tal oxides (Fe 3O4 or Al2O3) we re re duce d and metal nanoparticles were fabricate d Me tal plates with a low e lectrical resistance were fabricate d by sinte ring them at a low tempe rature of 520 K The e lectrical properties of the air ce lls fabricate d using sinte re d paste with nanoparticles as negative e lectrical cathodes we re the same as those of the air ce lls fabricate d in a blast furnace  It was found that the sinte re d me tal nanopaste could be use d for air ce lls

Air Cells Using Negative Metal Electrodes Fabricated by Sintering Pastes with Base Metal Nanoparticles for Efficient Utilization of Solar Energy

The wheeler cap method is studied by the electromagnetic field simulation and experiments. The guidelines when radiation efficiency is measured by using the wheeler cap method can be obtained. It is effective to select the shield where the frequency shift is not caused. The fact that only the contribution of the radiation can be removed by using a very small shield is reported in Reference, which is the study for the point source. In this paper, the same phenomenon was able to be confirmed about the antenna that had the finite size.

Yukio Iida

Papers

Hydrogen Production Using Reduced-Iron Nanoparticles by Laser Ablation in Liquids

Study on self-collimated light-focusing device using the 2-D photonic crystal with a parallelogram lattice

INCREASE IN EFFECTIVE FLUORESCENCE LIFETIME BY CROSS-RELAXATION EFFECT DEPENDING ON TEMPERATURE OF Nd/Cr:YAG CERAMIC USING WHITE-LIGHT PUMP SOURCE

Air Cells Using Negative Metal Electrodes Fabricated by Sintering Pastes with Base Metal Nanoparticles for Efficient Utilization of Solar Energy

A Study of Antenna Efficiency Measurements by Wheeler Cap Method Applied to Planer Inverted-F Antenna (PIFA)