70-nm-bandwidth achromatic waveguide coupler

This article describes two mathematical formalisms for the determination of the second and fourth order parameters of molecular films using optical spectroscopy. Method A uses polarized total internal reflection fluorescence (TIRF) to calculate the second and fourth order parameters, 〈P 2 (cos θ)〉 and 〈P 4 (cos θ)〉, using an independently determined value for the angle between the absorption and emission dipoles, γ. Method B uses 〈P 2 (cos θ)〉 obtained from attenuated total reflectance (ATR) data, along with polarized TIRF measurements to calculate 〈P 4 (cos θ)〉 and 〈cos 2 γ〉. The choice of a specific method should rely on experimental considerations. We also present a method to separate the contributions of substrate surface roughness and dipole orientation with respect to the molecular axis from the spectroscopically determined second and fourth order parameters. Finally, a maximum entropy approach for construction of an orientation distribution from order parameters is compared with the commonly used delta and Gaussian distributions.

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“…3,53 By combining eqs 8 and 9, we obtain Similarly, by combining eqs 10 and 11, and using eqs 18 and 19, we obtain…”

Section: Polarized Fluorescencementioning

confidence: 96%

Combination of Polarized TIRF and ATR Spectroscopies for Determination of the Second and Fourth Order Parameters of Molecular Orientation in Thin Films and Construction of an Orientation Distribution Based on the Maximum Entropy Method

2006

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“…The number of reflections can be easily determined from geometrical considerations and is given by 22 where h is the thickness of the guiding element, L is the distance between the in-and out-coupling prisms, n 0 is defined above, and N is the effective refractive index (also called Snell's invariant, N ) n 0 sin θ 0 ). N is experimentally determined by the incoupling conditions of the propagating beam into the guiding element 23 as shown in Figure 1, where θ inc is the angle between the prism A ) -log 10 (…”

Section: Theorymentioning

confidence: 99%

Determination of Anisotropic Optical Constants and Surface Coverage of Molecular Films Using Polarized Visible ATR Spectroscopy. Application to Adsorbed Cytochrome c Films

et al. 2004

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This article describes a method to determine the anisotropic optical constants and surface coverage of molecular films using polarized attenuated total reflectance (ATR) absorbance measurements. We have extended the transfer-matrix formalism to describe birefringent and dichroic films in ATR geometries and have combined it with an iterative numerical procedure to determine the anisotropic values of both the real (n) and imaginary (k) parts of the complex refractive index of the film under investigation. Anisotropic values of the imaginary part of the refractive index (k) allow for the determination of the surface coverage and one order parameter of the film. To illustrate this approach, we have used cytochrome c (cyt c) protein films adsorbed to glass and indium tin oxide (ITO) surfaces. Experimental results show that cyt c films on these surfaces, which were formed under identical conditions, have significant differences in their surface coverages (11.2 ( 0.4 pmol/ cm 2 on glass and 21.7 ( 0.9 pmol/cm 2 on ITO); however, their order parameters 〈cos 2 θ〉 are similar (0.30 ( 0.02 on glass and 0.36 ( 0.04 on ITO).

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“…For constructive interference to be achieved, the total phase shift during one "round-trip" should equal an integral multiple of 2π. For those values of N wg that satisfy this resonance condition, a propagating field (mode) along the waveguide is established (27,29).…”

Section: Fundamentalsmentioning

confidence: 99%

“…Numerous attempts to address the spectral bandwidth problem have been reported but had limited success (29). Mendes reported the first truly successful solutions when he tested two different approaches for achieving achromatic coupling into a single-mode, planar IOW (29,34,35).…”

Section: Broadband Iow-atr Spectroscopymentioning

confidence: 99%

“…In those cases, achromatic incoupling was unsuccessful at wavelengths <500 nm because of the "steep" dispersion of a 7059 glass IOW in this region of the spectrum (29,34,35). In contrast, incoupling white light with the large-NA approach extends the bandwidth down to at least 390 nm; the total bandwidth exceeds 200 nm, twice that of the spectrometers based on achromatic coupling.…”

Section: Broadband Iow-atr Spectroscopymentioning

confidence: 99%

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