High-efficiency defect-based photonic-crystal tapers designed by a genetic algorithm

Håkansson, Andréas; Sanchís, Pablo; Sánchez‐Dehesa, José; Martí, J.

doi:10.1109/jlt.2005.857760

Cited by 26 publications

(16 citation statements)

References 22 publications

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“…The position, the radii and the number of rods was varied until numerical simulations showed the structure to have low reflection; each candidate defect was evaluated by a computationally expensive FDTD (finite difference time domain) simulation. The technique was demonstrated experimentally [56], and later refined by Håkansson et al [57], who employed genetic algorithms to perform the search of parameter space, before a semianalytic method [58] was developed to make the evaluation of each set of defects more efficient. In the semi-analytic method [58], numerics are used to calculate Bloch mode transmission and reflection matrices representing the properties of each interface (between input waveguide and taper, and taper and PC waveguide); these quantities are then used in an analytic expression to calculate the reflection of the structure as a whole.…”

Section: Adiabatic Coupling Regionsmentioning

confidence: 99%

Photonic-crystal surface modes found from impedances

et al. 2010

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We present a rigorous definition of a wave impedance for 2D rectangular and triangular lattice photonic crystals (PCs), in the form of a matrix. Reflection and transmission at an interface between PCs can be represented by matrices that relate the Bloch mode (eigenmode) amplitudes in the two PCs; we show that these matrices, which are multi-mode generalisations of reflection and transmission coefficients, may be calculated from the PCs' impedances that we define.Given the impedances and Bloch factors (propagation constants) of a collection of PCs, the reflection and transmission properties of arbitrary stacks of these PCs may be calculated efficiently using a few matrix operations. Therefore our definition enables PC-based antireflection coatings to be designed efficiently: some computationally expensive simulations are required in an initial step to find a range of PCs' impedances, but then the reflectances of every coating that consists of a stack of these PCs can be calculated without any further simulations.We first define the PC impedance from the transfer matrix of a single PC layer (i.e., a grating). Since transfer matrix methods are not especially widespread, we also present a method and associated source code to extract a PC's propagating and evanescent Bloch modes from a scattering calculation that can be performed by any off-the-shelf field solver, and to calculate impedances from the extracted modal fields.Finally, we put our method to use. We apply it to design antireflection coatings, nearly eliminating reflection at a single frequency for one or both polarisations, or lowering it across a larger bandwidth. We use it to find surface modes at interfaces between PCs and air, and their projected band structures. We use the impedance to define effective parameters for PC homogenisation, and we briefly describe how our definition has been used to dispersion engineer a PC waveguide. Statement of contribution for joint author publicationsLawrence, F. J. et al. "Antireflection coatings for two-dimensional photonic crystals using a rigorous impedance definition". Appl. Phys. Lett. 93, 1114Lett. 93, (2008 This Letter is partially based on work done in FL's Honours year, and partially on work done during his PhD. Most of the software used was provided by KD and LB, and FL extended it in collaboration with them. In FL's PhD he extended the software implementation of the method (with help from KD and LB) to support non-normal incidence and frequencies above the first Wood anomaly. FL wrote the letter, which was heavily edited and proofread by MdS, KD, and LB.Lawrence, F. J. et al. "Impedance of square and triangular lattice photonic crystals". Phys. Rev. A 80, 23826 (2009) The suggestion of generalising the method to triangular lattices was made by FL's supervisors. LB supplied the orthogonality relations, which as noted in the paper are from previous work, and FL worked out how to use these to define the impedance for these structures. LB suggested the final notation used in the paper. Taking the Ma...

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Section: Adiabatic Coupling Regionsmentioning

confidence: 99%

Photonic-crystal surface modes found from impedances

et al. 2010

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“…6 demonstrate the possibility of fabricating high-aspect-ratio rod-type PCs for the visible light region. A coupling technique based on properly inserting localized defects within a PC taper has been proposed and experimentally demonstrated [25] to improve the coupling efficiency between conventional waveguides and PC waveguides. We also designed and fabricated the 18a-long PC taper for coupler and splitter to achieve the high coupling efficiency.…”

Section: Fabrication and Optical Measurement Of Rod-type Pc Wavelengtmentioning

confidence: 99%

Fabrication and optical characteristics of silicon-based two-dimensional wavelength division multiplexing splitter with photonic crystal directional waveguide couplers

Liu

2011

Physics Letters A

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“…9,10 Yet, the main attraction was directed toward the utilization of the tapered PCWs that facilitate adiabatic mode conversion. [11][12][13][14][15][16][17][18][19][20] The supporting theoretical studies show promise for considerably high coupling efficiencies when we make use of these tapered PCWs. 21,22 Nonetheless, tapered PCWs have simultaneously led to serious drawbacks.…”

Section: Introductionmentioning

confidence: 73%

High efficiency of graded index photonic crystal as an input coupler

Cakmak

Çolak

Çağlayan

et al. 2009

Journal of Applied Physics

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Cataloged from PDF version of article.A graded index photonic crystal (GRIN PC) configuration was placed at the input side of a photonic crystal waveguide (PCW) in order to efficiently couple the light waves into the waveguide. We compared the transmission efficiencies of light in the absence and presence of the GRIN PC structure. We report a significant improvement in coupling when the GRIN PC is incorporated with the PCW. The intensity profiles were obtained by carrying out the experiments at microwave frequencies. Finite difference time domain based simulations were found to be in good agreement with our experimental results

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High-efficiency defect-based photonic-crystal tapers designed by a genetic algorithm

Cited by 26 publications

References 22 publications

Photonic-crystal surface modes found from impedances

Photonic-crystal surface modes found from impedances

Fabrication and optical characteristics of silicon-based two-dimensional wavelength division multiplexing splitter with photonic crystal directional waveguide couplers

High efficiency of graded index photonic crystal as an input coupler

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