Modeling of circular integrated optical microresonators by 2-D frequency domain coupled mode theory

Circular integrated optical (ring or disk) microresonators are increasingly employed as compact and versatile wavelength filters. In this paper, we investigate a 2-D frequency domain model for these devices, based on spatial coupled mode theory. The microresonators are functionally represented in terms of two couplers with appropriate connections using bent and straight waveguides. The abstract scattering matrices of the couplers and the propagation constants of the cavity bends allow to compute the spectral responses of the resonators. Capitalizing on the availability of rigorous analytical modal solutions for bent waveguides, the constituent bent-straight waveguide couplers are modeled using a spatial coupled mode formalism derived by means of a variational principle. The resulting scattering matrices show reciprocity properties as expected according to the symmetry of the coupler structures. We present results for the spectral response and field examples for microresonators with mono- and multi-modal cavities for TE and TM polarizations. Comparisons with finite difference time domain simulations show very good overall agreement.     

Novel multimode interference devices for low index contrast materials systems featuring deeply etched air trenches

A novel design of multimode interference (MMI) device is proposed for photonic integrated circuits fabricated in low index contrast materials. In this design, deeply etched air trenches are used to define the boundaries of the multimode section to achieve strong lateral confinement. This results in superior imaging quality and therefore lower loss and imbalance, which can only be achieved in strongly guiding MMIs. However, the access waveguides remain weakly guiding, which is essential for low loss fibre connection. We demonstrate the merit of the design in 1 × 4 MMI power splitters. By introducing air trenches, loss decreases from 0.45 to 0.053 dB and imbalance decreases from 0.15 to 0.058 dB for TE polarization. For TM polarization, loss decreases from 0.46 to 0.003 dB and imbalance decreases from 0.16 to 0.067 dB.     

Numerical Analysis on Transmission Characteristics of a Bragg Grating Assisted Mismatched Fiber Coupler

Based on mode-coupled theory, a Bragg grating assisted mismatched fiber coupler is analyzed theoretically. At the same time, a detailed numerical analysis on transmission characteristics of the coupler is carried out when it considers the arcs of two fibers in the coupling region of the coupler or not, and the optimized design on the Bragg grating assisted mismatched fiber coupler for wavelength-division multiplexing/ demultiplexing is proposed.     

TLM Analysis of Multimode Interference Devices

In this article, the use of the transmission line matrix (TLM) method for the analysis of multimode interference (MMI) devices is demonstrated. Time domain solvers of Maxwell equations, such as the TLM method, are a highly accurate alternative in the modeling of photonic devices that permit overcoming the limitations found in other approximate methods. The full optical transfer function is obtained from the computation of the device response to a single input temporal pulse. A novel parallel computation scheme based on a sliding window wave propagator permits reduction of the high computational load requirements.     

Numerical Analysis on Transmission Characteristics of a Bragg Grating Assisted Mismatched Fiber Coupler

l IntroductionWavelength-division multiplexing (~) technology is an imPOrtant approach tosatisfy substantial increase of telecommunication network capacity. As one Of keytechnologies used in WDM networks, much progress has been made for wavelengthdivision multipl exing/ demul tip lexing technology thes e years. Based on perfect spectrumcharacteristics of fiber Bragg gratingS and fiber coUPlers, many approaches have beenproPOSed for wavelength-division multiplexing/ de multi pl eXing in a…     

Study on a Multiplexer a 40 Gb/s OTDM System

In a 4?0Gb/s OTDM system (optical time-division-multiplication) system, multiplexing devices are key devices. The time interval of four channels of the 40Gb/s OTDM system is 25ps respectively. If the time intervals are no accurate, will induce the system performance to degeneration. In order to make out OTDM device and carry out a transmission experiment in a 40Gb/s OTDM system, a kind of OTDM device is researched. This scheme be used to fabricate multiplex device. Also the device have been used to a 40Gb/s OTDM system. Our experimental results shows that, the multiplex device based on the six 1 optical fiber couplers can be used to multiple at a time domain.That make four 10Gb/s optical signals multiple to 40Gb/s. The time interval error of each of channels is not bigger than 1ps, inserted loss is smaller than 2dB.     

光纤马赫—陈德尔干涉型8波分超窄波分复用器的研制

报道了采用７个单模光纤马赫－陈德尔干涉仪进行三级串联而组成的８波分复用器，既保留了干涉型光纤波分复用器超窄波分复用间隔的优点，又消除了其复用路数少的缺点。文中介绍了这类波分复用器的原理、设计方法和制造技术。实验样品的使用波段为１．５μｍ，波长复用间隔为２．４ｎｍ，整个器件的附加损耗约为１．５ｄＢ。     

Beam Waveguide Reflector with Integrated Direction-Finding Antenna for In-Situ Alignment

An in-situ alignment system for beam waveguides based on an interferometric direction-finding antenna was investigated numerically and experimentally. The system consists of a reflector with four off-central positioned waveguide couplers in two directions. By nulling the difference of the power signals as well as the mixing signal from each coupler pair, spatial and angular alignments of a beam impinging on the mirror can be performed.In this paper, the characteristics of such a mirror are presented, and the design of a prototype intended for use in an ECH transmission line at LHD is described. Low-power as well as high-power tests at a frequency of 82.7 GHz were carried out, and the results are discussed. The device shows a high performance in agreement with theory.     

Solid-state single photon sources: light collection strategies

We examine the problem of efficiently collecting the photons produced by solid-state single photon sources. The extent of the problem is first established with the aid of simple physical concepts. Several approaches to improving the collection efficiency are then examined and are broadly categorized into two types. First are those based on cavity quantum dynamics, in which the pathways by which the source may emit a photon are restricted, thus channeling emission into one desired mode. Second are those where we try to reshape the free space modes into a target mode in an optimal way, by means of refraction, without fundamentally altering the way in which the source emits. Respectively, we examine a variety of microcavities and solid immersion lenses. Whilst we find that the micropillar microcavities offer the highest collection efficiency (∼70%), choosing this approach may not always be appropriate due to other constraints. Details of the different approaches, their merits and drawbacks are discussed in detail. Received 19 July 2001 and Received in final form 5 October 2001     

Amphiphilic building blocks as head groups in linear polymers

Starting with asymmetric A,A′-carbonate couplers A1–A4 via substitution reaction with primary amines at low temperatures (0–25 °C) followed by addition reaction with primary amines at higher temperatures (60–80 °C), bis(functional) compounds with a free hydroxyl group were prepared. These compounds were used: (i) as initiators for ring-opening polymerization of ε-caprolactone; (ii) as substrate for the preparation of an ATRP initiator for MMA polymerization; (iii) as substrate for the preparation of an activated carbonate for grafting of an amine end-functionalized linear polymer (Jeffamine® M1000). Via modifications (i)–(iii), amphiphilic end-functionalized poly(ε-caprolactone)s, poly(methyl methacrylate)s, and polyethers were prepared, respectively.