双包层光子晶体光纤特性研究

通过对比双包层光子晶体光纤与聚合物双包层光纤的结构特性以及泵浦方法,得出双包层光子晶体光纤（DC-PCF）可以产生比聚合物双包层光纤大得多的数值孔径,但需要侧面泵浦和利用锥形多模光纤连接的PC-DCF不适合构建放大器的结论。研究表明,光子晶体光纤所具有的大数值孔径能有效地减少高功率放大器中的非线性光学效应。     

Fast speed pore formation via strong oxidizers

It is difficult to produce nice macropores at high speed with strong oxidants via the breakdown mechanism on low doped n-Si. In this letter, HF-containing electrolytes were modified with strong oxidants; galvanostatically anodizing in the dark, macropores with depths upto 80 μm and pore-diameters between 100 and 1000 nm were fast produced on low doped substrate. Two new phenomena were observed: pore tips could be tumefied simultaneously and macropores could be filled with a uniform microporous layer under dark conditions. Mild short-range ordering of pores was observed. The macropores are rather nice while the etching rate could reach the highest of its kind, 1800 μm/h. The underlying mechanism was in the framework of the current-burst-model combined with avalanche breakdown; both pore pitch and pore-wall thickness could be significantly less than SCR (space charge region) width.     

Light scattering by randomly rough isotropic dielectric surfaces

Abstract

An experimental investigation of the angular distribution of the light scattered by randomly rough, two-dimensional, isotropic dielectric surfaces is presented. The surfaces, whose profiles constitute good approximations to Gaussian random processes with Gaussian correlation functions, are fabricated in a photoresist and characterized by means of a mechanical profilometer. The substrates employed in the fabrication of the samples consist of thick parallel plates of filter glass that absorb the incident light and whose refractive index is close to that of the photoresist. This allows us to approximate experimentally a situation in which the light is scattered by a randomly rough interface between two semi-infinite dielectric media, illuminated from the air side. The results display features that can be attributed to multiple scattering. In particular, significant amounts of cross-polarized scattered light, as well as an enhanced backscattering peak, were observed in the scattering measurements.     

Photonic-crystal light-emitting diodes on p-type GaAs substrates for optical communications

Oxide-confined photonic-crystal (PhC) light-emitting diodes (LEDs) on p-type GaAs substrate in the 830 nm range are reported. The device consists of a bottom distributed Bragg reflector (DBR), quantum wells (QWs), and a top DBR, with a photonic-crystal structure formed within the n-type ohmic contact ring for light extraction. The etching depth of the PhC holes is 17-pair out of the 22-pair top DBR being etched off. The internally reflected spontaneous light emission can be extracted out of PhC holes because of lower reflectance within those areas. High-resolution micrographic imaging studies indicate that the device emits light mainly through the photonic-crystal holes and it is suitable for optical communications.     

A new iterative method for analysing nonlinear photonic-crystal structures

The article presents an efficient iterative method for analysing non-linear photonic crystals. The new approach is used for analysing a frequency converter constructed with a 2D pillar-type photonic crystal waveguide structure. The considered converter uses the non-linear properties and the compound waveguide structure. The analysis is based on the iterative resolution of two relationships between incident and reflected volume-waves. The reflection operator is expressed using Hankel functions. Numerical results have been obtained with moderate CPU time and memory requirement. Simulations obtained are in agreement with recent published results.