Ellipsometric determination of permittivity in a negative index photonic crystal metamaterial

Abstract

In this work, we present the first experimental evidence of negative dielectric susceptibility in a two-dimensional silicon photonic crystal (PhC) with negative refractive index behavior. In the frequency range in which the effective refractive index n eff is equal to 21, the incident light couples efficiently to the guided modes in the top surface layer of the PhC metamaterial. These modes resemble surface plasmon polariton resonances. This finding was confirmed by ellipsometric measurements, demonstrating the isotropy of the PhC resonances. Such negative index PhC materials may be of use in biosensing applications. Light: Science & Applications (2012) 4 as well as multiplexing. 5 The power of PhCs and their unusual properties arises from the optical bandgap, which can be tailored by design. Recently, PhCs have been used more widely as a metamaterial with an effective negative refractive index.6-10 Light propagating in such a metamaterial can undergo a drastic change in group velocity, causing the light to bend away from the usual direction that is observed with a conventional refracting medium. Owing to the fine control over the optical bandgap of the PhC, the effective refractive index can exhibit optical antimatter behavior.7 For example, a set of circular holes etched vertically into a silicon slab in a hexagonal arrangement can produce an effective resonant refractive index of n eff 521 for light propagating along the length of the slab (perpendicular to the direction of the holes). Such a metamaterial strongly couples incoming light and can be used to transmit data with minimum losses over millimeter distances for lab-on-a-chip applications. 8The reflection spectra of patterned surfaces have been widely studied since the discovery of Wood anomalies in metallic gratings. 11In particular, Fano found a clear connection between the narrow anomalies and surface wave excitation that distinguished broad and sharp anomalies. 12 The theoretical understanding of this phenomenon has been provided by Hessel and Oliner. 13 Similarly, the resonances in PhC slabs have been analyzed in reflection and transmission.14 These resonances have been used to reconstruct the band structure 15 and equifrequency surface 16 of PhCs. Similar to surface plasmon polariton (SPP) resonances, the resonant anomalies allow for the propagation of otherwise forbidden modes. 15 Other analogies with SPP behavior arise for PhCs at frequencies where the refractive index turns negative. In this paper, we present an experimental study of the resonance effects directly connected with negative refractive index properties of PhC. Using standard ellipsometric measurements of the amplitude y and phase D of the ratio between the linear polarization reflection coefficients, we demonstrate that the change in the dielectric function of negative index PhC is similar to the change in the dielectric constant of a plasmonic structure.17 Similar to the Fano resonances, 17,18 the resonances in the y spectrum corresponding to a 180 6 phase change are slightly...

Flexible and Semitransparent Organic Solar Cells

“…[154][155][156][157][158][159] In 2013, Martorell et al [160] developed a new strategy by using nonperiodic photonic crystals to trap near-infrared and nearultraviolet photons for the OSCs. The photon management provided by the nonperiodic 1D structure of five layers is sufficient to maintain the light-harvesting capacity of the semitransparent device to 77% of that of the opaque cell.…”

Guided resonance in negative index photonic crystals: a new approach

“…This result confirms that the negative index PhC layer is strongly correlated with a resonant effective permittivity, 27 which, in this case, can be modeled with a Lorentzian function (1). 24 Moreover, we estimated the experimental quality factor Q and obtained a value on the order of 10 3 , which is among the highest values experimentally determined for a PhC slab. In addition, by varying the angle of incidence in the reflectivity spectrum, we calculated the band structure of the photonic crystal.…”

“…In Ref. 24, we experimentally demonstrated that, in the range of negative effective refractive indices, a photonic crystal can be modeled as a Lorentz resonator and can exhibit plasmon-like material behavior. 25 Therefore, we assume that the PhC slab can be described by a dielectric function given by a simple Lorentz function: Comparison between IR images in the resonance condition (l51588 nm and h565 6 ) and in the out-of-resonance condition (l51592 nm and h565 6 ) acquired in front of the sample (c) and from the lateral side (f).…”

Observation of resonant states in negative refractive photonic crystals

“…It provides unique optical properties, including unusual transmission and emission properties [22]- [25]. Recently, it has been demonstrated that the dielectric permittivity of PhC (non-metallic structures), in the frequency range where the refractive index is negative, is well described by a Lorentz model [26]:…”

“…As reported in Figure 4, the measured dispersion (black dots) is in good agreement with the simulated dispersion points (blue squares) obtained by using RCWA. Moreover, this corresponds to the sign of the calculated and measured group velocity of the mode along the parallel wavevector, k // [26]. …”