Extended lattice filters enabled by four-directional couplers

Novel lattice-filter structures consisting of four-directional couplers are introduced, analyzed, and discussed. Four-directional couplers are discussed, and energy-conservation relations in a field-wave application are derived. A thick linear lattice filter is presented and studied as a simple extension to the traditional lattice. A two-dimensional lattice structure is also introduced and studied. Transfer functions are derived and discussed for several examples.     

Preferential-order waveguide grating couplers: a comparative rigorous analysis using the finite-difference time-domain method

We rigorously analyze and compare preferential-order waveguide grating output couplers using the finite-difference time-domain method in the total-field/scattered-field formulation for TE and TM polarizations. Four kinds of preferential-order grating couplers are studied: volume holographic grating couplers, slanted parallelogrammic surface-relief grating couplers, double-corrugated surface-relief grating couplers, and reflecting-stack surface-relief grating couplers. The outcoupling efficiencies and branching ratios of the couplers, revealing their preferentiality, are calculated and compared with the rigorous coupled-wave analysis leaky-mode method. In addition, their performance is examined in terms of the main design parameters and the excitation wavelength.     

Compact tuneable single and dual mode ferrite left-handed coplanar waveguide coupled line couplers

For the first time, single and dual mode novel left-handed coupled line couplers implemented on ferrite substrates are reported. Both of the proposed couplers demonstrate novel characteristics of coupler operation with properties of tunability and non-reciprocity, which have not been demonstrated before. The proposed couplers are realised in a left-handed coplanar waveguide configuration, constructed using interdigital capacitors and various types of planar shunt inductors. The performance of the couplers has been studied theoretically and verified numerically. The single mode tuneable coupler demonstrates a coupling level as high as 4 dB with a maximum isolation level better than 25 dB. The dual mode tuneable coupler exhibits nonreciprocal operations with a near-zero dB coupling level and a maximum non-reciprocal isolation level of more than 30 dB. Moreover, both the couplers have very compact sizes: 10.32 mm x 19.8 mm for the single mode coupler and 10.2 mm x 19.8 mm for the dual mode tuneable coupler, respectively.     

Inter- and Intra-Molecular Interactions in the Systems Couplers-Gelatin and Couplers-Synthetic Polymers

The interactions between photographic gelatin and couplers employed in colour photography (derived from acylacetanilides and, in a few cases, from pyrazolones series) have been studied by viscometry, determining the effect of the addition of different amounts of couplers on the viscosity of aqueous solutions of gelatin. In particular, the effect of the length of the antidiffusional aliphatic chain of the couplers has been examined, as well as that of molecular weight and concentration of gelatin. Some synthetic polymers, having in their macromolecules the same functional groups as are present in gelatin, have also been investigated for comparative purposes: the hydroxyl groups seemed to be the major ones responsible for the interactions. The results obtained are briefly reported and discussed in terms of intra- and inter-molecular aggregations.     

Dispensed polymer waveguides and laser-fabricated couplers for optical interconnects on printed circuit boards

Optical interconnects can provide chip-to-chip data communication with much needed bandwidth as processor speed and density keep growing. Optical waveguides and couplers are essential components for implementing optical interconnections. Techniques for directly dispensing polymer waveguides in laser-ablated trenches on printed circuit boards and for fabricating optical couplers are presented for quick prototype of optical interconnects. High-quality UV curable polymer waveguides were routinely fabricated. High-efficiency couplers, blazed grating couplers on sloped waveguides, sloped facet metal film couplers, and reflective-undercut facet couplers can be fabricated by using excimer laser ablation.     

Controlling the polarization dependence of dual-channel directional couplers formed by silicon-on-insulator slot waveguides

The polarization dependence of directional couplers (DC) formed by silicon-on-insulator (SOI) slot waveguides was studied, and its applications as highly efficient polarization beam splitters (PBSs) and polarization-independent directional couplers (PIDCs) were investigated. The coupling lengths for the quasi-TE and quasi-TM modes may vary with the waveguide geometry due to structural birefringence; thus numerical simulations of the coupling effects in the directional couplers with different aspect ratios and waveguide spacing were conducted to obtain the optimal design parameters for high efficiency as well as compact device size. The lengths of the coupling regions of the designed PBS and PIDC are 47.61 and 23.13 μm, respectively, and they delivered good performance, with an extinction ratio greater than 20 and 1 dB bandwidth larger than 100 nm. The tolerance of fabrication error in the practical device is also discussed.     

Traveling waves in two parallel infinite linear point-scatterer arrays

Traveling waves in two coupled parallel infinite linear point-scatterer arrays are studied analytically for the first time to our knowledge. The two arrays are considered to be generally offset in the axial direction. It is found that slow quasi-even/odd supermodes are supported, as a result of the coupling-induced splitting of the modes of the single array, in direct analogy to standard optical waveguide couplers. Exactly even/odd supermodes are supported when the axial offset is zero. Mode splitting, dispersion curves, and coupling length are numerically investigated versus the inter-element spacing, the inter-array distance, and the axial offset. Potential applications of the concept are in directional optical couplers made of metallic or dielectric nanoparticle chains.     

Input waveguide grating couplers designed for a desired wavelength and polarization response

Input grating couplers are used to couple light from free space into a waveguide and can provide additional functions such as focusing and beam splitting of the light into arbitrary desired positions in the waveguide. We show that it is possible to design the couplers so that they perform different desired functions depending on the polarization or wavelength of the incident light. We demonstrate experimentally a number of couplers that may be of interest, e.g., in optical fiber communications. Examples are polarization-independent couplers, designed to have the same response for two orthogonal polarizations of the incident light, and couplers for demultiplexing in wavelength division multiplexing applications, designed to separate and focus different input wavelengths to different positions in the waveguide.     

Volume grating couplers: polarization and loss effects

We analyze the polarization-dependent performance and the loss performance of volume grating couplers using a leaky-mode approach in conjunction with rigorous coupled-wave analysis for two configurations: the volume grating in the cover layer and the volume grating in the waveguide. The angular dependence of TE and TM polarization coupling efficiency is studied, and designs for polarization-dependent and polarization-independent couplers are presented for both configurations. Polarization-dependent couplers are obtained with an outcoupling angle close to normal. Polarization-independent couplers are obtained with outcoupling angles away from normal, 46.7 deg in the case of a volume grating in the cover layer and 54.4 deg in the case of a volume grating in the waveguide. The effect of loss on coupler performance is also analyzed. It is found that, for cases of practical importance, the effect of lossy coupler materials is small. The estimated loss for a commercially available material is 5 dB/cm. For TE-polarized light and the volume grating in the waveguide, a loss of this magnitude reduces the coupling efficiency by less than 3%, whereas in the case of the volume grating in the cover layer, it reduces the coupling efficiency by less than 0.3%.     

Non-classical behaviour and switching in Kerr nonlinear couplers

Abstract

Directional nonlinear couplers composed of two Kerr nonlinear waveguides are studied. Quantum consistent solutions of the equations of motion are obtained showing the collapses and revivals of the field mode amplitudes. The approximate method is also adopted for the contradirectional geometry and the switching accompanied by collapses of the modes is revealed. Kerr couplers with varying linear coefficients are examined and possible controls of the switching of modes, for instance, digital switching and fast switching are demonstrated. The two-mode squeezing of vacuum fluctuations and the generation of pure states are shown.     

超高速彩色乳剂中DAR成色剂的应用研究

论述了 Ｄ Ａ Ｒ 成色剂在超高速感蓝和感红乳剂中增感作用及影响因素。     

Optimization of nonbinary slanted surface-relief gratings as high-efficiency broadband couplers for light guides

We propose and investigate the use of slanted surface-relief gratings with nonbinary profiles as high-efficiency broadband couplers for light guides. First, a Chandezon-method-based rigorous numerical formulation is presented for modeling the slanted gratings with overhanging profiles. Then, two typical types of slanted grating couplers--a sinusoidal one and a trapezoidal one--are studied and optimized numerically, both exhibiting a high coupling efficiency of over 50% over the full band of white LED under the normal illumination of unpolarized light. Reasonable structural parameters with nice tolerance have been obtained for the optimized designs. It is found that the performance of the couplers depends little on the grating profile shape, but primarily on the grating period and the slant angle of the ridge. The underlying mechanism is analyzed by the equivalence rules of gratings, which provide useful guidelines for the design and fabrication of the couplers. Preliminary investigation has been performed on the fabrication and replication of the slanted overhanging grating couplers, which shows the feasibility of fabrication with mature microfabrication techniques and the perspective for mass production.     

硫醚类二当量品红成色剂的研究

本文叙述硫醚类二当量品红成色剂的合成和性能研究,经彩色胶卷和彩色相纸应用试验,与四当量成色剂比较,有着更高照相活性与稳定性,并说明了与DIR品成色剂的区别．     

柯达公司成色剂的最新进展（上）

综述了柯达公司近年来提出新的成色剂（包括主成色剂和功能性成色剂）的结构、类型、特性及应用，并总结出成色剂的最新进展。     

Couplers in colour photography—chemistry and function Part 2

Abstract

Part 2 deals with magenta and cyan couplers and—in addition—white couplers and scavengers, centred about the years between 1960 and 2000 as in Part 1.

Magenta couplers have been a domain of heteroaromatic compounds. This fundamental situation has not changed, except for the fact that the predominance of pyrazolone type magenta couplers has been broken. Today, 3-acylamino- and 3-anilinopyrazolones are still used, but mainly in colour negative film, and pyrazolotriazoles of the pyrazolo[5,1-c](1,2,4)triazole and pyrazolo[1,5-b](1,2,4)triazole classes have taken a larger share, despite the fact that suitable syntheses had to be explored for both classes.

In colour negative (CN) paper, where the lower reactivity level of pyrazolotriazoles does not really bother, the inherently clean absorption and high tinctorial strength of the azomethine dyes from pyrazolotriazoles plays an important role. While the stability level of azomethine dyes from 3-anilinopyrazolones was considerably improved between 1960 and 1980, it does not compare favourably to the stability achieved today by azomethine dyes from pyrazolotriazoles. This applies equally to stain resistance, light fading and dark fading.

Within the anilinopyrazolone series, valuable two-equivalent couplers have been found by the introduction of arylthio groups as leaving groups. Within the acylaminopyrazolones this has been achieved by the introduction of pyrazoles as leaving groups. The chemical problems encountered in these—and in comparable, but less successful—transformations must not be underestimated. Within the pyrazolotriazole classes, chlorine presents itself as a trouble-free and readily introduced leaving group.

Throughout the years, phenols and naphthols have been used as cyan couplers. For both classes of cyan couplers a strong need for improvement in dye stability was recognized. In CN film, the cyan dyes from 1-hydroxy-2-naphthoic amides showed low resistance to reduction by exhausted bleaches and were replaced by 2-phenylureido-5-acylaminophenols or 5-amino-substituted 1-hydroxy-2-naphthoic amides. In CN paper, 2-acylamino-4,6-dichloro-5-methylphenol type cyan couplers were replaced by 2-acylamino-4,6-dichloro-5-ethylphenols which show high stability to light fading. Thus, improved dark fading resistance of the cyan dye in colour paper has turned out to be a major objective of continued chemical research.

Research on, among other options, the field of polyazapentalenes, a large group of bicyclic acidic heteroaromatic compounds, comprising also the well-known pyrazolotriazoles, has yielded some classes of new heterocyclic cyan couplers giving cyan dyes of outstanding tinctorial strength and absorption, of which the pyrrolo[1,2-b](1,2,4-triazoles) are the most prominent examples. The dyes from presently known pyrrolotriazole couplers are stable to dark fading, but they need some improvement in light stability. An entirely different approach to solving the dark stability problem without any sacrifice in hue and light stability has been found within the class of 2,5-diacylaminophenols, by introduction of a sulphone-modified acyl group.

White couplers and scavengers are expected to function without additional problems, and in most cases do. Nevertheless, the compounds under discussion are interesting under theoretical aspects. True white couplers, e.g. of the 4-methylpyrazolone class, show incomplete coupling and do not fix the developer residue permanently: it can be shown to be split off by oxidation. Scavengers of the 2,4-disulphonamidophenol class and also of the 2,5-disulphonamidophenol class do not show the coupling reaction of a two-equivalent coupler; instead they undergo electron transfer to an oxidized colour developer.     

新一代的DIAR成色剂

本文叙述了ＤＩＡＲ成色剂的发明人柯达公司的Ｐｈｉｌｉｐ Ｔ．Ｓ．Ｌａｕ于１９９１年１０月提出的新一代的ＤＩＡＲ成色剂的结构特点、典型结构式、制备及应用效果。     

Optimization of pump absorption in MOF lasers via multi-long-period gratings: design strategies

Different strategies for designing optical couplers, optimized to enhance the pump absorption in the rare-earth-doped core of microstructured fiber lasers, are illustrated. Three kinds/configurations of optical couplers have been designed and compared as examples of the different design strategies which can be followed. Their effectiveness to enhance the performance of an ytterbium-doped, double cladding, microstructured optical fiber laser has been accurately simulated. They consist of a suitable cascade of multiple long-period gratings (MLPGs) inscribed in the fiber core region. The characteristics of the MLPG couplers have been simulated via a homemade computer code based on both rate equations and an extended coupled mode theory. The proposed MLPG couplers seem particularly useful in the case of low rare-earth concentration but, even for a middle-high ytterbium concentration, as N(Yb)=5×10(25) ions/m(3), the slope efficiency S can be increased up to 20%, depending on the fiber length.     

Exact design of novel miniaturised fractal-shaped branch-line couplers using phase-equalising method

Although miniaturised and fractal-shaped branch-line couplers have been reported by many researchers, their operating bandwidth are narrowed and shifted because the phase-shifting properties of the fractal-shaped microstriplines with different iteration orders are different to each other; thus the application of these techniques were limited. In this paper, an exact design technique is presented to obtain compact and fractal-shaped branch-line couplers for a given frequency. By using the length reduction formulae of the chamfered bend and equalising the transmission phase of the fractal-shaped microstriplines of the proposed fractal-shaped branch-line couplers to their counterparts of the conventional branch-line coupler, the phaseshifting phenomenon of the fractal branch-line couplers can be compensated. As an example, novel fractalshaped branch-line couplers operated at 2.4 GHz using Koch fractal shapes of different iteration orders have been designed successfully, and the designed couplers all operated at the designed frequency and achieved a maximum 81.8% size reduction. And furthermore, the operating frequency and its bandwidth are virtually unaltered. The proposed method is verified by the measurement results.     

Design of miniaturised branch-line and rat-race hybrid couplers with harmonics suppression

Shunt open-stubs are used to design reduced size branch-line and rat-race couplers with suppressed harmonics. The band stop response of shunt stubs has been utilised to suppress the harmonics. Design graphs are presented to ease the design process. Even?odd mode analysis is carried out to investigate in-band and out-of-band performances of the couplers. Two branch-line and one rat-race couplers have been fabricated. Experimental results of the designed couplers agree well with the theoretical predictions. For the branch-line coupler, up to fifth harmonic suppression and 37% size reduction are obtained. Up to seventh harmonic suppression and 69% size reduction are obtained for the rat-race coupler.     

Multifunctional gratings for surface-emitting lasers: design and implementation

We experimentally demonstrate the use of two different multifunctional grating couplers in surface-emitting lasers for improved beam quality and advanced beam profiles. The lasers used for the demonstration are grating-based unstable resonator lasers, each with a grating coupler for surface emission and beam shaping. The new design method, described in detail, allows for simultaneous optimization of arbitrary feedback and outcoupling characteristics of the grating coupler. The first coupler is designed to reduce feedback to the resonator that would otherwise disturb the operation of the laser and lower the beam quality and to produce an output beam focused to four spots. The second coupler is designed to provide the feedback needed to support the unstable resonator, eliminating one feedback grating, and simultaneously focus the output beam to a single spot. As far as we know, this is the first time such multifunctional couplers are used in grating-coupled surface-emitting lasers. The couplers provide near-diffraction-limited spots that are a considerable improvement compared with previous lasers with no feedback control in the couplers.