The term photonic crystals appears because of the analogy between electron waves in crystals and the light waves in artificial periodic dielectric structures. During the recent years the investigation of one-, two-and three-dimensional periodic structures has attracted a widespread attention of the world optics community because of great potentiality of such structures in advanced applied optical fields. The interest in periodic structures has been stimulated by the fast development of semiconductor technology that now allows the fabrication of artificial structures, whose period is comparable with the wavelength of light in the visible and infrared ranges.

http://ieeexplore.ieee.org/iel5/6354/16969/00781867.pdf

Photonic crystals

http://nathan.instras.com/ResearchProposalDB/doc-108.pdf

Radiative decay engineering 5: metal-enhanced fluorescence and plasmon emission

Fluorescence is widely used in optical devices, microscopy imaging, biology, medical research and diagnosis. Improving fluorescence sensitivity, all the way to the limit of single-molecular detection needed in many applications, remains a great challenge. The technique of surface enhanced fluorescence (SEF) is based upon the design of surfaces in the vicinity of the emitter. SEF yields an overall improvement in the fluorescence detection efficiency through modification and control of the local electromagnetic environment of the emitter. Near-field coupling between the emitter and surface modes plays a crucial role in SEF. In particular, plasmonic surfaces with localized and propagating surface plasmons are efficient SEF substrates. Recent progress in tailoring surfaces at the nanometre scale extends greatly the realm of SEF applications. This review focuses on the recent advances in the different mechanisms involved in SEF, in each case highlighting the most relevant applications.

http://turroserver.chem.columbia.edu/surfaceplasmons/pdf/53_jpd_41_1_2008_sefsrev.pdf

Surface enhanced fluorescence

Metallic nanostructures now play an important role in many applications. In particular, for the emerging fields of plasmonics and nanophotonics, the ability to engineer metals on nanometric scales allows the development of new devices and the study of exciting physics. This review focuses on top-down nanofabrication techniques for engineering metallic nanostructures, along with computational and experimental characterization techniques. A variety of current and emerging applications are also covered.

/pdf/engineering-metallic-nanostructures-for-plasmonics-and-3c47ox5c4s.pdf

Engineering metallic nanostructures for plasmonics and nanophotonics

To improve light extraction from organic light-emitting diodes (OLEDs), we introduced a photonic crystal pattern into the glass substrate of an OLED. The periodic modulation converts the guided waves in the high-refractive-index indium-tin-oxide/organic layers into external leaky waves. We used the finite-difference time-domain method to optimize the structural parameters of the photonic crystal pattern and to analyze the microcavity effect by the metallic cathode of the OLED. With the use of an optimized photonic crystal pattern, an increase of over 80% in the extraction efficiency of the OLED is expected theoretically. An increase in the extraction efficiency of over 50% was achieved experimentally, without detriment to the crucial electrical properties of the OLED.

A high-extraction-efficiency nanopatterned organic light-emitting diode

In the present paper we determine the optical constants and thicknesses of multilayer thin film stacks, in the visible and near infrared ranges. These parameters are derived from the transmittance and reflectance spectra measured by a spectrophotometer, for several angles of incidence. Several examples are studied, from a simple single layer structure up to a 22-layer dielectric filter. We show that the use of a large number of incidence angles is an effective means of reducing the number of mathematical solutions and converging on the correct physical solution when the number of layers increases. More specifically, we provide an in-depth discussion of the approach used to extract the index and thickness of each layer, which is achieved by analysing the various mathematical solutions given by a global optimization procedure, based on as little as 6 and as many as 32 variable parameters. The results show that multiple incidences, lead to the true solution for a filter with a large number of layers. In the present study, a Clustering Global Optimization algorithm is used, and is shown to be efficient even for a high number of variable parameters. Our analysis allows the accuracy of the reverse engineering process to be estimated at approximately 1 nm for the thickness, and 2 10−3 for the index of each layer in a 22-layer filter.

Exploitation of multiple incidences spectrometric measurements for thin film reverse engineering

In this paper we use spectrophotometric measurements and a Clustering Global Optimization procedure to determine the complex refractive index of SiO2 layer from 250 nm to 1250 nm. A special commercial optical module allows the reflection and transmission measurements to be made under exactly the same illumination and measurement conditions. We compare the index determination results obtained from two different single layer SiO2 samples, with high and low index glass substrates, respectively. We then determine the refractive index of SiO2 for a bi-layer design in which the first deposited layer is Ta2O5. The corresponding solutions are discussed and we show that the real part of the complex refractive index obtained for a bi-layer is slightly different to that found for a single layer investigation. When SiO2 is included inside a thin film stack, we propose the use of an index determination method in which a bi-layer is used for the real part of the complex refractive index, and single layer determination is used for the imaginary part of the refractive index in the UV range.

https://www.jeos.org/index.php/jeos_rp/article/download/13010/931

Refractive index determination of SiO2 layer in the UV/Vis/NIR range: spectrophotometric reverse engineering on single and bi-layer designs

One can increase the angular tolerance of resonant grating filters without modifying the spectral bandwidth by adding a second grating component parallel to the first one. The angular tolerance and the filter linewidth can be controlled by the designer in an independent way. Numerical results show that this property permits the use of waveguide-grating filters with standard collimated beams.

/pdf/increasing-the-angular-tolerance-of-resonant-grating-filters-411oo72j2h.pdf

Increasing the angular tolerance of resonant grating filters with doubly periodic structures.

Resonant grating filters are promising components for free-space narrowband filtering. Unfortunately, due to their weak angular tolerance, their performances are strongly deteriorated when they are illuminated with a standard collimated beam. Yet this problem can be overcome by resorting to a complex periodic pattern known as the doubly periodic grating [Lemarchand et al., Opt. Lett.23, 1149 (1998)]. We report what we believe to be the first experimental fabrication and characterization of a bidimensional doubly periodic grating filter. We obtained a 0.5 nm bandpass polarization independent reflection filter for telecom wavelengths (1520-1570 nm) that presents a transmittivity minimum of 18% with a standard incident collimated beam.

Fabien Lemarchand

Papers

Exploitation of multiple incidences spectrometric measurements for thin film reverse engineering

Refractive index determination of SiO2 layer in the UV/Vis/NIR range: spectrophotometric reverse engineering on single and bi-layer designs

Increasing the angular tolerance of resonant grating filters with doubly periodic structures.

Experimental demonstration of a narrowband, angular tolerant, polarization independent, doubly periodic resonant grating filter.

Comparison of different dispersion models for single layer optical thin film index determination