Analysis and Design of Grating Couplers

Tamir, T.; Peng, Sheng-Yu

doi:10.1007/bf00895934

Cited by 15 publications

(32 citation statements)

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“…and a canonic surface-relief grating at the boundary between the waveguide and the substrate with a modulation depth of approximately 12 nm [32]. The stated parameters yield an enhancement factor of approximately 100 for the light intensity impinging on the mologram.…”

Section: B Focal Molography On a Thin-film Optical Waveguidementioning

confidence: 99%

“…2 the local light intensity that impinges on the mologram on the waveguide surface. The enhancement factor depends on the diameter D of the IC, its coupling efficiency, and on the optical parameters of the waveguide [32]. We consider a waveguide of high refractive index (e.g., Ta 2 O 5 , n f ¼ 2.117, λ ¼ 635 nm) with thickness t f ¼ 145 nm on a glass substrate with refractive index n s ¼…”

Section: B Focal Molography On a Thin-film Optical Waveguidementioning

confidence: 99%

“…(5), (6), (7), (9), and (10) can be derived for the fundamental TM mode of the considered waveguide and for the higher modes of thicker waveguides [32,44]. The influence of the waveguide parameters on the sensitivities of focal molography for the TE and TM modes of the waveguide can be derived from the analysis of the differential sensitivities ∂N=∂n 0 of the refractometric thin-film waveguide biosensor given in Ref.…”

Section: Sensitivity Of Focal Molography On a Thin-film Optical Wamentioning

confidence: 99%

“…We assume t m ≤ λ=20, so the parabolic region of A molo applies [32]. P wg is the power of the TE mode impinging on the mologram.…”

Section: Sensitivity Of Focal Molography On a Thin-film Optical Wamentioning

confidence: 99%

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Coherent Signal Picks Out Biomolecular Interactions

Binnig¹

2014

Physics

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We introduce and theoretically investigate here a novel analytical method that we have called focal molography, in which molecular interactions are made visible through scattering of coherent light by a coherent pattern of molecules. The scattered light quantifies the presence of molecules at molecular interaction sites. It is separated from noncoherent background scatter by a combination of local dark-field illumination, interference enhancement, and spatial filtering. The latter is achieved by holographic focusing of the wave field generated by the coherently assembled molecules onto an Airy disk and by subtraction of the noncoherent irradiance in the focal plane outside the disk from the irradiance in the disk. This new microscopic method allows distinct detection of low-refractive-index contrast in the nanoenvironment of biomolecules from which information on the interaction of the coherently assembled molecules with molecules in a liquid or gaseous sample may be deduced. The noncoherent surroundings of the coherently assembled molecules consist of freely diffusing solvent and solute molecules. The surroundings, as well as changes in temperature, do not contribute to the coherent signal in the diffraction focus. Interference lithography or high-resolution-imaging lithography can be used to synthesize the coherent pattern of molecules on a monolithic substrate. The coherent pattern of molecules constitutes a synthetic phase hologram that creates a diffraction-limited light wave. We suggest the term "mologram" for the coherent assembly of functional nanostructures and the term "focal molography" for label-free or labeled analysis of molecular interactions through the measurement of the properties of light in the focus of the mologram. We derive analytical formulas that express the detection signal and the sensitivity of focal molography on the surface of a high-refractive-index thin-film optical waveguide in terms of known parameters. We discuss the implementation of a readout system for molograms on a thin-film optical waveguide by adapting a confocal laser-scanning microscope to a bifocal laser-scanning microscope.

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Section: B Focal Molography On a Thin-film Optical Waveguidementioning

confidence: 99%

Section: B Focal Molography On a Thin-film Optical Waveguidementioning

confidence: 99%

Section: Sensitivity Of Focal Molography On a Thin-film Optical Wamentioning

confidence: 99%

“…We assume t m ≤ λ=20, so the parabolic region of A molo applies [32]. P wg is the power of the TE mode impinging on the mologram.…”

Section: Sensitivity Of Focal Molography On a Thin-film Optical Wamentioning

confidence: 99%

See 2 more Smart Citations

Coherent Signal Picks Out Biomolecular Interactions

Binnig¹

2014

Physics

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show abstract

“…We present a perturbation analysis of the guiding properties on refractive-index gratings by using equivalent transmission line approach [18]. The leakage parameter a, which influences the leakage energy into the diffracted orders scattered by the grating, is achieved as functions of the structure parameters of the refractive index grating, for example, grating period, thickness of the waveguide and index modulation Dn.…”

Section: Introductionmentioning

confidence: 99%