Slab photonic crystal demultiplexers : analysis and design

The exploitation of the superprism phenomenon for optical demultiplexing using a slab photonic crystal on the silicon on insulator platform is the main subject of this thesis. The S-vector and k-vector superprisms are considered. Design equations for the S-vector superprism demultiplexer which fully take into account the nonlinear spectral dependence of beam propagation and dispersion are introduced. This allows wide-band coarse wavelength division multiplexing (CWDM) demultiplexers to be designed. Selecting minimum prism area as a metric, the best photonic crystal lattice, design parameters and prism geometry is sought. A full 3-D modeling approach using the plane wave expansion method is employed to ensure the practicality of the design. We show that the slab 1-D photonic crystal can provide the smallest superprism. Based on our result, an area of 1367 mum2 is sufficient to resolve 4 standard CWDM channels (20nm channel spacing). We extend this approach by proposing a stratified photonic crystal which has 5 times less area for an 8 channel CWDM design.We then propose the first fully integrated k-vector superprism layout. Design rules and equations are presented and we use these to obtain the design parameters that result in a minimum prism area. We show that an optimized 1-D photonic crystal k-vector superprism with the area of less than 0.1 mm2 is sufficient to resolve 32 standard dense wavelength division multiplexing (DWDM) channels (100GHz channel spacing). The resulting chip size is approximately 4.5 times less than an equivalent etched grating demultiplexer.We also demonstrate that fast lenses can be made using slab 1-D photonic crystal with an periodicity.We introduce an analytical approximation technique for slab 1-D photonic crystals based on the weighted index method. The variational nature of the method leads to acceptable results for moderate refractive index contrast materials. The method can also be extended to 2-D cases and to nonlinear systems.The plane wave expansion (PWE) method and field matching have been combined to obtain a new method which is capable of obtaining all types of modes including the leaky modes of slab 1-D photonic crystals. The method requires fewer plane waves than the conventional PWE method but provides a better approximation. We compare our results with an accurate finite element method as a benchmark.A report of our first attempt for the fabrication, post-possessing and optical characterization of the proposed k-vector superprism demultiplexer is also presented. We recommend the development of a cladding, and more accurate fabrication procedures for future investigations

Effect of Honey on Peridural Fibrosis Formation after Laminectomy in Rats: A Novel Experimental Study

Despite progress in surgical techniques, some patients still face postoperative recurrence of pain. Recently, more attention has been focused on peridural fibrosis (PF), which may be responsible for recurrent pain after laminectomy or discectomy. Honey has been shown to exert anti-inflammatory effects on exposed tissues besides its well-known antibacterial properties. The aim of this study were to investigate the effects of honey on the prevention of postlaminectomy fibrosis formation in a rat model. A controlled blinded study was performed in 45 male adult white Sprague-Dawley rats that underwent laminectomy at the L5-L6 levels. They were divided into 3 groups (A, B, and C) of 15 rats each. Group A (sham) underwent laminectomy and group B was treated with normal saline at the laminectomy site. Rats in group C received 0.1 mL honey at the laminectomy site. All rats were killed 4 weeks after laminectomy. PF was found in 5 rats (33%) of control groups A and B, and in 2 rats (10%) in honey-treated laminectomy group C. The difference was not statistically significant. Wound healing was not affected, and there was no cerebrospinal fluid leakage. Although honey appears to be safe, it cannot cause a significant reduction of PF formation after lumbar laminectomy in rats

Periodic Arrays of Gold Nano-Disks Coupled with Evanescent Spectroscopy

We study and analyze various spectral features of gold nano-disk arrays coupled with the evanescent field of an optical waveguide using finite difference time domain simulations for comparison to our previous work on this topic (Jiang et al, Journal of Lightwave Technology 27, no.13, (2009): 2264-2270). We find that the quadrupolar and dipolar peaks are both heavily dependent on the coherent interactions of the periodic array and show comparable performance for refractive index sensing applications. We also find sharp extinction peaks and dips in the simulated spectra, but they are not sensitive to the index change of the surface-bound layer. A detailed analysis on these sharp features reveals that the sharp extinction peaks are grating-induced quadrupolar modes and the dips represent the suppressed plasmon resonances caused by the photonic band gap

Effect of circadian rhythm disturbance on morphine preference and addiction in male rats: Involvement of period genes and dopamine D1 receptor

It is claimed that a correlation exists between disturbance of circadian rhythms by factors such as alteration of normal light-dark cycle and the development of addiction. However, the exact mechanisms involved in this relationship are not much understood. Here we have studied the effect of constant light on morphine voluntary consumption and withdrawal symptoms and also investigated the involvement of Per1, Per2 and dopamine D1 receptor in these processes. Male wistar rats were kept under standard (LD) or constant light (LL) conditions for one month. The plasma concentration of melatonin was evaluated by enzyme-linked immunosorbent assay (ELISA). Real-time PCR was used to determine the mRNA expression of Per1, Per2 and dopamine D1 receptor in the striatum and prefrontal cortex. Morphine preference (50 mg/L) was evaluated in a two-bottle-choice paradigm for 10 weeks and withdrawal symptoms were recorded after administration of naloxone (3 mg/kg). One month exposure to constant light resulted in a significant decrease of melatonin concentration in the LL group. In addition, mRNA levels of Per2 and dopamine D1 receptor were up-regulated in both the striatum and prefrontal cortex of the LL group. However, expression of Per1 gene was only up-regulated in the striatum of LL rats in comparison to LD animals. Furthermore, after one month exposure to constant light, morphine consumption and preference ratio and also severity of naloxone-induced withdrawal syndrome were significantly greater in LL animals. It is concluded that exposure to constant light by up-regulation of Per2 and dopamine D1 receptor in the striatum and prefrontal cortex and up-regulation of Per1 in the striatum and the possible involvement of melatonin makes animals vulnerable to morphine preference and addiction. © 2016 IBRO