Fundamental limit to the use of effective medium theories in optics

Some theory of a dual-polarization interferometer for sensor applications

“…The ratio shows a near-linear increase with increasing layer index. However, the ratio is strikingly insensitive to layer thickness, a property previously observed and remarked on by Cross [6] for a similar structure. The theory provides a simple qualitative explanation for the weak dependence of the TE-TM index ratio on layer thickness and also the formulae for a quantitative description.…”

“…As an illustrative example of the application of the theory in section 2 we consider the effect of an adlayer on the modes of a waveguide with the parameter values given in table 1, which are those of a structure used in the work reported in [6]. In the absence of an adlayer the waveguide considered has modes with effective refractive indexes (to six significant figures), n te0 = 1.50754 and n tm0 = 1.50648 when excited by a helium-neon laser with a free space wavelength of 632.8 nm.…”

“…Cross and co-workers [1][2][3][4][5][6] have described in a series of papers the principles and some applications of a sensor based on a particular design of dual-waveguide interferometer. The basic structure is two parallel dielectric slab waveguides each with just one mode of each polarization (TE and TM) sharing a common cladding layer that is sufficiently thick that the two guides operate in an effectively independent manner.…”

Dual-Polarization Interferometry: A Novel Technique To Light up the Nanomolecular World

“…5 The input power coupling efficiency is about -26 dB for each waveguide. 12 Furthermore, the design of the waveguide stack allows transverse-magnetic (TM) and transverse-electric (TE)polarizations passing along the sensing and reference waveguides, which enables the measurement of two optical phase changes. The polarization can be switched rapidly (on a 2 ms cycle), allowing instantaneous measurements of molecular processes occurring on the sensing waveguide.…”

In-situ Optical Characterization of Noble Metal Thin Film Deposition and Development of a High-Performance Plasmonic Sensor

“…Once fabricated, the intensity and wavelength dependence of the plasmonic enhancement are related to the material and geometric parameters of metallic nanostructures: the size, 106,107 pattern, 108,109 as well as the permittivity of the metal and surrounding material. 105,113 While size and geometric patterns can be extracted with modern imaging and surface profilometric tools, the complex permittivity is typically obtained from the reflection and transmission measurements of the metallic film with analysis using Drude model parametrization and Kramers−Kronig relations. [114][115][116] However, it is now clear that these approaches, which were developed for bulk (i.e., continuous) metals films, are less suitable for ultrathin metals 117 or aggregates of metal nanoparticles (NPs) with individual sizes of the order 50 nm and less.…”