Determination of refractive index profiles of gradient optical waveguides by ellipsometry

Tonova, D.; Paneva, A.; Pantchev, B.

doi:10.1016/s0030-4018(98)00094-7

Cited by 17 publications

(11 citation statements)

References 20 publications

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“…These include ellipsometry using multiple angle data [1], mode measurements mediated with a prism coupler (for both guided and leaky modes) [2][3][4], reflectance analysis [5,6] and numerous interferometric methods [7][8][9][10][11][12][13]. Each method has advantages and disadvantages.…”

Section: Introductionmentioning

confidence: 99%

Measurement of planar refractive index profiles with rapid variations in glass using interferometry and total variation regularized differentiation

Oven

2015

Journal of Modern Optics

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Planar refractive index profiles with rapid variations, formed in glass, are measured with interferometry. This involves forming a bevel in the glass and orientating the fringe pattern to be normal to the bevel edge. The index profile is determined by differentiation of the phase function of the fringe pattern. The differentiation has been performed using the total variation regularization method in order to preserve rapid changes in the derivative. This new approach avoids the necessity of filtering, in order to reduce noise, in the direction perpendicular to the bevel, which would otherwise smooth out the rapid index changes. The method is assessed using a model refractive index profile that contains an index gradient of 0.24 μm −1 and is then applied practically to measure the refractive index profile of electrically poled BK7 glass. The new approach allows the sharp transition in the index between poled and unpoled glass to be observed as well as the accumulation of potassium ions beyond the poled glass region.

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Section: Introductionmentioning

confidence: 99%

Measurement of planar refractive index profiles with rapid variations in glass using interferometry and total variation regularized differentiation

Oven

2015

Journal of Modern Optics

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“…They could be calculated from measurements at two different angles of incidence. [6][7][8] This would be subject to complicating effects of finite substrate thickness that do not exist for normal incidence. More practical is the use of Eq.…”

Section: Types Of Experiments and Specific Data Analysismentioning

confidence: 99%

“…For observable fringes, it is necessary that the index of refraction of the layer differ from the indices of refraction of the phases bounding it, presumably relatively dry alginate (n a between 1.00 and 1.334, the index for hydrated alginate) 10,11 and solid substrate (n quartz ¼ 1.46, n polystyrene ¼ 1.57). 6,7 Since ΔA for the fringes decreases as the film dries, the higher value is chosen for n f in Fig. 1.…”

Section: Layer Formationmentioning

confidence: 99%

Optical interference probe of biofilm hydrology: label-free characterization of the dynamic hydration behavior of native biofilms

et al. 2017

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Biofilm produced by Escherichia coli (E. coli) or Pseudomonas aeruginosa (P. aeruginosa) on quartz or polystyrene is removed from the culture medium and drained. Observed optical interference fringes indicate the presence of a layer of uniform thickness with refractive index different from air-dried biofilm. Fringe wavelengths indicate that layer optical thickness is < 20 ?? ? m or 1 to 2 orders of magnitude thinner than the biofilm as measured by confocal Raman microscopy or fluorescence imaging of the bacteria. Raman shows that films have an alginate-like carbohydrate composition. Fringe amplitudes indicate that the refractive index of the interfering layer is higher than dry alginate. Drying and rehydration nondestructively thins and restores the interfering layer. The strength of the 1451-nm near infrared water absorption varies in unison with thickness. Absorption and layer thickness are proportional for films with different bacteria, substrates, and growth conditions. Formation of the interfering layer is general, possibly depending more on the chemical nature of alginate-like materials than bacterial processes. Films grown during the exponential growth phase produce no observable interference fringes, indicating requirements for layer formation are not met, possibly reflecting bacterial activities at that stage. The interfering layer might provide a protective environment for bacteria when water is scarce.

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“…In past years, several methods, especially nondestructive ones, have been created and developed to recover the gradient refractive index profile on the condition that the effective refractive indices of each guided mode have already been measured, such as reflectivity profiling, 1 ellipsometry, 2 Wigner distribution of an optical waveguide. [3][4][5] Among them, the most popular methods are the inverse WKB method, [6][7][8] and the improved IWKB method.…”

Section: Introductionmentioning

confidence: 99%

Improved method for recovering graded-index profile of isotropic waveguide by cubic spline function

2010

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An improved method for recovering the refractive index profile of an isotropic graded-index waveguide is presented on the basis of the cubic spline interpolation method. The surface refractive index of the waveguide can be obtained by using a polynomial function that is related with the parameters of all modes. The simulation results of several typical index distributions show that this method can be employed to recover a graded-index profile well.

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Determination of refractive index profiles of gradient optical waveguides by ellipsometry

Cited by 17 publications

References 20 publications

Measurement of planar refractive index profiles with rapid variations in glass using interferometry and total variation regularized differentiation

Measurement of planar refractive index profiles with rapid variations in glass using interferometry and total variation regularized differentiation

Optical interference probe of biofilm hydrology: label-free characterization of the dynamic hydration behavior of native biofilms

Improved method for recovering graded-index profile of isotropic waveguide by cubic spline function

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