Table of contents

A new method devised for solving the three-dimensional (3D) atmospheric refraction problem is presented. It considers the situation when the origin and the end of the refracted beam are given (boundary value problem) and is based on Fermat's variational principle. Original points of the method are the 3D geometry with ellipsoidal Earth, no sampling of exo-atmospheric beam and treatment of mirage effects.

The method is first described and great care is given to the particular case of grazing incidence yielding mirages. In contrast, the case of exo-atmospheric paths (satellite links) is optimized by using a variable integration step, large outside and small inside the atmosphere. Validation is then performed by comparison with numerical and analytical models in the case of astronomical refraction and with MODTRAN 3.5 in the case of terrestrial refraction. The influence of the Earth's oblateness is shown to modify the refraction angle by 1.3% in absolute magnitude. Consistency is also checked with the direct method where the origin, direction of sight and distance are specified (initial value problem).

In a companion paper (Berton, Part II) the influence of significant parameters such as observer and target distance and altitude, vertical profiles of temperature, pressure and humidity, wavelength and sampling step will be analysed in detail. The accuracy of the refractive index formula will also be tested.

In contrast to previous two-dimensional coated photonic crystals, in this paper we propose a left-handed one that is made of dielectric tubes arranged in a close-packed hexagonal lattice. Without metallic cores, this structure is low-loss and convenient to fabricate. Negative refraction and its resulting focusing are investigated by dispersion characteristic analysis and numerical simulation of the field pattern. With proper modification at the interface, the image is improved. With better isotropy than that with noncircular rods, planoconcave lenses made by dielectric tubes focus a Gaussian beam exactly at R/|n−1|.

The two-photon-induced excited state intramolecular proton transfer (ESIPT) process of 2-(2^'-hydroxyphenyl) benzothiazole (HBT) in cyclohexane solution has been investigated. We focus on the calculation of the two-photon absorption (TPA) coefficient and nonlinear refraction index of HBT, and the theoretical computational results are in good agreement with the experimental ones. By establishing the ESIPT kinetic model for HBT based on TPA, the TPA cross section is obtained. The numerical results show that HBT exhibits a rather large TPA cross section compared with that of 2-(2^'-hydroxyphenyl)benzoxazole (HBO) reported previously. Therefore, HBT is a promising TPA material and is worthy of further research.

We propose that the operational wavelength of waveguided Si-based photonic integrated circuits and optoelectronic integrated circuits can be extended beyond the 1.55 µm telecom range into the wide infrared from 1.55 to 100 µm. The Si rib-membrane waveguide offers low-loss transmission from 1.2 to 6 µm and from 24 to 100 µm. This waveguide, which is compatible with Si microelectronics manufacturing, is constructed from silicon-on-insulator by etching away the oxide locally beneath the rib. Alternatively, low-loss waveguiding from 1.9 to 14.7 µm is assured by employing a crystal Ge rib grown directly upon the Si substrate. The Si-based hollow-core waveguide is an excellent device that minimizes loss due to silicon's 6–24 µm multi-phonon absorption. Here the rectangular air-filled core is surrounded by SiGe/Si multi-layer anti-resonant or Bragg claddings. The hollow channel offers less than 1.7 dB cm⁻¹ loss from 1.2 to 100 µm.

Methods to derive aerosol optical depth in the UV spectral range from ground-based remote-sensing stations equipped with Brewer spectrophotometers have been recently developed. In this study a modified Langley plot method has been implemented to retrieve aerosol optical depth from direct sun Brewer measurements. The method uses measurements over an extended range of atmospheric airmasses obtained with two different neutral density filters, and accounts for short-term variations of total ozone, derived from the same direct sun observations. The improved algorithm has been applied to data collected with a Brewer mark IV, operational in Rome, Italy, and with a Brewer mark III, operational in Lampedusa, Italy, in the Mediterranean. The efficiency of the improved algorithm has been tested comparing the number of determinations of the extraterrestrial constant against those obtained with a standard Langley plot procedure. The improved method produces a larger number of reliable Langley plots, allowing for a better statistical characterization of the extraterrestrial constant and a better study of its temporal variability. The values of aerosol optical depth calculated in Rome and Lampedusa compare well with simultaneous determinations in the 416–440 nm interval derived from MFRSR and CIMEL measurements.

A systematic rigorous matrix method based on generalized transmission line (TL) modelling for the full-vectorial analysis of the guided modes of multilayer planar lossy anisotropic optical waveguides is developed. By means of the proposed method, complex propagation constants and mode field distributions of the propagating modes of planar waveguides with an arbitrary finite number of layers made of arbitrarily oriented anisotropic media are determined. The mode coupling and conversion phenomenon in a biaxial slab waveguide is demonstrated and a mode labelling scheme based on the polarization of the allowable plane waves in anisotropic media is proposed.

Transverse electromagnetic (TEM) modes are studied in circular negative-refractive-index waveguides. Such modes can be supported, if the dielectric permittivities and magnetic permeabilities of the core and cladding are equal in absolute value and differ in sign. We reveal a number of unusual properties of TEM modes in the fibre, such as zero total energy flux and the existence of a wave with homogeneous field distribution in the core. The possibility of zero group velocity dispersion is investigated as well.

Rigorous solutions of the Maxwell equations describing propagation invariant optical fields are presented in general; the elements for their specific applications to the Bessel, Mathieu and Weber families are also provided. Electric and magnetic transverse modes, and several polarization state solutions, are constructed; the connections between them are explicitly established. Their respective energy densities and Poynting vectors are also evaluated, in order to exhibit their propagation invariant nature. The experience with Bessel beams allows us to recognize that vector modes exhibit new and important features compared with the corresponding scalar fields; the results of this work constitute a first step towards the analysis of the dynamical properties of vector Mathieu and Weber beams.

For the first time, all-dielectric planar chiral metamaterials consisting of arrays of silicon nitride gammadions on fused silica substrates have been fabricated, and shown to be capable of inducing large changes to the polarization states of transmitted light in a manner that is dependent on the two-dimensional chirality of the microstructured silicon nitride film. The polarization response is found to reverse for opposite enantiomers, and also for the same enantiomer when it is illuminated from opposite sides of the structure. In addition, the polarization states of the various diffracted beams are found to be non-reversible. These structures therefore appear to display elements of non-reciprocal behaviour. The polarization responses of complementary designs, different chiral geometries and various silicon nitride film thicknesses have also been studied. As a result we conclude that multiple reflections within the patterned silicon nitride layer play an important role in defining the mechanism by which these structures are able to modify the polarization states of diffracted light.

A numerical calculation method for the optical trapping force which is appropriate for single lensed fibre trapping (SLFT) is proposed. The piconewton optical trapping forces on a yeast cell in SLFT as a function of the position along two horizontal orthogonal axes are measured experimentally by static and dynamic methods, respectively. The order of magnitude and the characteristics of the theoretical trapping force curve calculated by our method are the same as those of the experimental measurement curve. The theoretical and experimental results for the angle of inclination of the fibre probe also coincide with each other.

A novel double-pass forward L-band erbium-doped superfluorescent fibre source (SFS) with a segment of unpumped fibre between the reflector and the wavelength division multiplexing (WDM) coupler is presented. The effects of the fibre length arrangement on the output characteristics of the L-band SFS are simulated. The spectral bandwidth is broadened and the conversion efficiency is enhanced by optimizing the fibre length ratio of the unpumped section to the total erbium-doped fibre. A broadband L-band SFS is obtained experimentally, with a 3 dB bandwidth of 46 nm, a power ripple less than 1 dB, and an output power of 23.6 mW.

We have observed laser induced birefringence in optically isotropic glasses as well as in Nd:YAG crystal using polarized pulses of wavelength 1.06 µm and duration 100 ps with an intensity near 10⁹ W cm⁻². The laser used in the experiment was a Nd:YAG oscillator–amplifier system. The change in the material induced by the laser was not a permanent change but existed for as long as the laser pulse lasted. We observed conoscopic patterns when the laser was passed through glass or the Nd:YAG crystal. These patterns are typically seen when light is passed through birefringent materials kept between a polarizer and analyser. This observation immediately suggests that the glass or the crystal possesses optical birefringence. This birefringence is demonstrated in fused silica glass, Nd:glass and Nd:YAG crystal. The circular symmetric conoscopic patterns show that the optic axis is formed along the direction of laser propagation. The laser induced birefringence depended on the laser intensity and we characterized the magnitude of this change by measuring the output pulse at the end of the crossed polarizer.

In this paper, the design of a resonant cavity enhanced photodetector, working at 1.55 µm and based on silicon technology, is reported. The photon absorption is due to the internal photoemission effect over the Schottky barrier at the metal–silicon interface. The photodetector is composed of a silicon layer in between multiple layers of Si–SiO₂, as a bottom mirror, and a thin Au film and dielectric coating, as a top mirror.

In order to estimate the quantum efficiency, we take advantage of the analytical formulation of the internal photoemission effect (Fowler theory) and its extension for thin films, while for the optical analysis of the device, used to calculate mirror reflectivities and active layer absorptance, a numerical method based on the transfer matrix method has been implemented. Our numerical results prove a significant enhancement of the efficiency obtained at resonant wavelengths by a very thin absorbing layer.

Material parameters, which include the complex index of refraction, (n,k), and surface roughness, are needed to determine passive long wave infrared (LWIR) polarimetric radiance. A single scatter microfacet bi-direction reflectance distribution function (BRDF) is central to the energy conserving (EC) model which determines emitted and reflected polarized surface radiance. Model predictions are compared to LWIR polarimetric data. An ellipsometry approach is described for finding an effective complex index of refraction or (n,k) averaged over the 8.5–9.5 µm wavelength range. The reflected S₃/S₂ ratios, where S₂ and S₃ are components of the Stokes (Born and Wolf 1975 Principles of Optics (London: Pergamon) p 30) vector, are used to determine (n,k). An imaging polarimeter with a rotating retarder is utilized to measure the Stokes vector. Effective (n,k) and two EC optical roughness parameters are presented for roughened glass and several unprepared, typical outdoor materials including metals and paints. A two parameter slope distribution function is introduced which is more flexible in modelling the source reflected intensity profiles or BRDF data than one parameter Cauchy or Gaussian distributions (Jordan et al 1996 Appl. Opt.35 3585–90; Priest and Meier 2002 Opt. Eng.41 992). The glass results show that the (n,k) needed to model polarimetric emission and scatter differ from that for a smooth surface and that surface roughness reduces the degree of linear polarization.

The bubbles in sea water are mostly coated with a layer of oil, of which the effect on scattered light has usually been ignored in previous studies. This paper aims to propose an equation of scattering intensity by coated bubbles in water, based on geometrical optics theories. During the research, a PC was used to generate a two-dimensional curve that models the angular distribution of scattered intensity, namely the volume scattering function (VSF), by a coated bubble with a diameter larger than 200 µm. The curve reveals the far-field characteristics of light scattered by the coated bubble, as well as the refractive rays that have the main influence on the scattering intensity. It is seen from the simulation results that the scattering intensity distribution of an uncoated bubble and a coated bubble are very similar. But the oil layer weakens the forward scattering effect of the coated bubble while it strengthens the backward scattering effect.