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1

Guided modes in capillary optical fibers

Romaniuk R. S.

Electronics and Telecommunications Quarterly

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2008

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Vol. 54, No 3

323-342

EN

A comparatively large group of capillary optical fibers, referred to in this paper as COF, consists of several families of optical filaments. The basic division line goes through the wave guidance mechanism. Two basic kinds of capillary optical fibers are of refractive and photonic mechanism of guided wave transmission. The work tries to compare wave modes in both kinds of optical fiber capillaries: refractive (RCOF) and photonic (PCOF). The differences are emphasized indicating prospective application areas of these fibers. Refractive COF carries most of the modal light in the ring-like, high-refraction, optical glass core encircling an empty capillary hole. Refractive capillary optical fibers are used widely for photonic instrumentation applications, due to the proximity of optical wave and capillary hole with the evanescent wave. The hole can be filled with a material subject to optical guided wave spectrometry. Photonic COF carries most of the light in air (or vacuum). Thus, photonic capillary optical fibers are considered for trunk optical communications, with guided wave travelling in vacuum rather than in glass - avoiding in this way the Rayleigh scattering. The fundamental mode in a refractive COF is LPoi or dark hollow beam (DHB) of light with zero intensity on fiber axis. The fundamental mode in a photonic COF is Gaussian beam with maximum intensity on fiber axis. The photonic COFs can be further divided to two basic groups: porous or holey/hollow and Bragg or OmniGuide fibers. These two kinds of PCOFs differ by the method of building a photonic band gap (PBG) around a capillary hole. The paper is a concise digest of fundamental kinds of singlemode (or low-order mode) COFs and their properties, with an emphasis on applications in two basic fields: instrumentation and telecommunications.

2

Efficient calculations of dispersive properties of phonic crystals using the transmission line matrix method

Romo G., Smy T.

Optica Applicata

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2005

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Vol. 35, nr 1

139-154

EN

In this paper, we present an analysis of the accuracy and efficiency of different approaches for the simulation of photonic crystals using the transmission line matrix method. The approaches that we present can be divided into two categories: complex- and real-valued algorithms using a uniform mesh, and complex- and real-valued algorthms using a multigrid mesh. The adventages and disadvantages of each approach are discussed and a brief comparision between these methods is made from the points of view of computqtional expense and accuracy. It is found that a combination of a real-valued method in a multigrid mesh results in the most efficient algorithm. However, while the complex-valued formulation is valid for the analysis of any phonic crystal, the applicability of the real-valued formulation is limited by structural constraints requiring cell symmetries. It is also found that a multigrid approach can considerably reduce the computational cost required for simulating phonic crystals and our results indicate that a good compromise between accuracy and computational cost can be found. Various photonic crystals are simulated by applying these approaches, and the results are validated using alternative methods.

3

Kryształy fotonowe

Hernan M. A.

Elektronika : konstrukcje, technologie, zastosowania

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2000

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Vol. 41, nr 8/9

30-35

PL

Kryształy fotonowe są strukturami materiałowymi, w których sztucznie wytworzono periodyczną, w przestrzeni konfiguracyjnej, modulację wartości przenikalności elektrycznej [epsilon](r). Rozchodzenie sie światła w krysztale fotonowym podlega podobnym regułom jakim podlega, zgodnie z teoria oasmową ciał stałych, ruch elektronu w periodycznym polu elektrycznym wytworzonym przez jony naturalnego kryształu, np. półprzewodnika. Najistotniejsza cecha kryształów fotonowych jest wystepowanie w nich tzw. przerwy fotonowej ( jest to pasmo częstości niedozwolonych leżących na skali częstości światła pomiedzy dwoma pasmami częstości dozwolych); światło o częstości z zakresu przerwy fotonowej nie może się rozchodzić w tym krysztale w żadnym kierunku. Artykuł jest elementarnym wprowadzeniem w podstawowe zagadnienia fizyczne i technologiczne dotyczące nowej, bardzo dynamicznie rozwijającej się na świecie dziedziny optoelektroniki, która jest oparta na wykorzystaniu kryształów fotonowych z intencjonalnie wprowadzonymi do ich struktury sieciowej defektami, w tym punktowymi źródłami światła , tz.n laserami lub diodami elektroluminescencyjnymi.

EN

Photonic crystals are artificially manufactured materials with a characteristic periodic modulation of the dielectric constant [epsilon](r). The light propagation in such a crystal is governed by similar rules like these, which govern, according to the band theory of solids, the movement of electrons in the periodic electric field of crystal lattice in natural crystals, eg., in semiconductors. The most important feature of a photonic crystals is the occurrence of photonic band gap ( this is a band of forbidden frequency of light in between of two bands of allowed frequencies): and light wave of frequency belonging to the photonic gap cannot propagate throughout the photonic crystal in no direction. An elementary introduction to the basic physical and technological problems of a new branch of optoelectronics, based on application of photonic crystals with intentionally created defects, including inserting into the crystal of lasers or light emitting diodes, is presented in this paper.