JEOS:RP - Journal of the European Optical Society Rapid publications
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High-NA aberration retrieval with the extended Nijboer-Zernike vector diffraction theory - Erratum
Get PDFIn the paper â€High-NA aberration retrieval with the Extended Nijboer-Zernike vector diffraction theory†by S. van Haver, J.J.M. Braat, P. Dirksen and A.J.E.M. Janssen, published in J. Europ. Opt. Soc. Rap. Public. 1, 06004 (2006), some regrettable notation errors are present in Eq.(10), page 06004-3. In this Erratum, the correct expression is given
Slow light by means of coherent population oscillations: laser linewidth effects
Get PDFSeveral groups have recently reported the observation of slow light propagation speeds based on the process of coherent population oscillations (CPO) under conditions such that the laser line width exceeds the width of the CPO transparency window. We explain this apparently paradoxical result by noting that the CPO effect is sensitive only to intensity variations of the incident laser field that occur on time scales comparable to or shorter than the population relaxation time of the material medium. Laser linewidths are associated primarily with phase fluctuations or with intensity fluctuations on much shorter time scales
Effects of partial coherence on frequency combs
Get PDFWe give an analytical model to study the deviations from an ideal
frequency comb when the effects of random variations, from pulse
to pulse, in the amplitude, phase, shape, chirp, and timing jitter
are simultaneously taken into account. This model is consistent
with the previous experimental research and extends the
theoretical work on spectral line widths of mode-locked lasers
Design and fabrication of an all-dielectric grating with top-hat high diffraction efficiency over a broad spectral range
Get PDFBetween 98% and 100% flat top efficiency –1st order TE diffraction over a 40 nm wavelength range centered at 800 nm can be obtained by an all-dielectric grating structure where the corrugation is etched in a high index layer unlike in the state of the art. 98% maximum efficiency and a wide-band top-hat diffraction efficiency spectrum are demonstrated experimentally opening to high efficiency femtosecond pulse compression for high average power laser machining
Dyakonov--Tamm wave at the planar interface of a chiral sculptured thin film and an isotropic dielectric material
Get PDFSurface waves, named here as Dyakonov--Tamm waves, can exist at the planar interface of an isotropic dielectric material and a chiral sculptured thin film (STF). Due to the periodic nonhomogeneity of a chiral STF, the range of the refractive index of the isotropic material is smaller but the range of the propagation direction in the interface plane is much larger, in comparison to those for the existence of Dyakonov waves at the planar interface of an isotropic dielectric material and a columnar thin film
A Stokes-based spectro-polarimetric analysis of the amplified spontaneous emission in a semiconductor optical amplifier
Get PDFSemiconductor Optical Amplifiers (SOAs), key devices for future all-optical communication systems, are inherently polarisation-dependent, which is a major drawback for most networks applications. In spite of numerous studies carried out in order to design polarisation-insensitive structures, no complete spectro-polarimetric characterization of a SOA has been published so far. In particular, the spectral and polarimetric behaviour of the Amplified Spontaneous Emission (ASE), acting as a partly polarized broadband source, is of interest, since ASE draws from the same carrier reservoir as the amplified signal. In this paper, we present a full spectro-polarimetric characterization of ASE emitted from a commercial, strained-bulk SOA within the frame of the Stokes formalism. This formalism not only allows a determination of the degree of polarisation (DOP) of ASE directly from its Stokes vector, but also gives access to a full, spectrally resolved characterization of its polarized fraction with respect to the bias current applied to the SOA. The way the state of polarisation of that fraction is governed by the dependence of the material gain upon polarisation is spectrally resolved, quantified, and discussed. The same study is performed when a polarized signal is injected into the SOA
All-optical switch based on liquid-crystal infiltrated photonic bandgap fiber in transverse configuration
Get PDFWe demonstrate optically controlled switching in a photonic bandgap fiber filled with liquid crystal using transverse coupling geometry. Fiber samples made from silica and lead silicate are studied. For the latter one, a continuous and fairly flat operating range from 600 to 1700 nm was achieved. The insertion loss was 3 dB and the extinction ratio better than 20 dB
Visualization of paper structure by optical coherence tomography: Monte Carlo simulations and experimental study
Get PDFThis paper analyzes the capability of an optical coherence tomography (OCT) setup to visualize paper structure by comparing experimental and Monte Carlo (MC) simulated OCT images. In the experiments, we used an OCT setup at 910 nm with the coherence length of an SLD source of 7.5 mum. Several different refractive index matching agents were applied to paper samples to enhance the visualization of their inner structure. The obtained OCT images show improved contrast in inner structure and enhanced visualization depth. A set of corresponding simulations were then performed using a previously developed MC code. A multilayer paper sheet model with non-planar fiber-air interfaces was developed to characterize the paper samples. MC simulations were carried out to study the effect of the setup parameters on the obtained OCT images. A comparison with the experimental data shows that the developed model provides a satisfactory correspondence between simulated and experimental images
Energy and momentum flux in a high-numerical-aperture beam using the extended Nijboer-Zernike diffraction formalism
Get PDFWe describe the energy and momentum flux in the case of an aberrated optical imaging system with a high numerical aperture (NA). The approach is based on the extended Nijboer-Zernike diffraction theory, that, in its high-NA version, yields an accurate analytic representation of the electromagnetic field vectors in the focal region of imaging systems that suffer from aberrations and/or transmission defects. In an earlier publication, we have derived the electromagnetic energy density from the field vectors. In this paper, we expand our analysis to the energy flow (Poynting vector) and to the quantities related to the linear and angular momentum of the radiation. Several examples of the energy and momentum flow are presented. In particular, we show how the linear and angular momentum distribution in the focal region depend on the initial polarization state and on the parameters describing the wavefront shape of the converging beam. For the angular momentum flow, we show how the separation between spin and orbital momentum is modified when going from the paraxial case to a high-NA focused beam
Active microcavity and coupled cavities in one-dimensional photonic crystal
Get PDFThe propagation of light in one-dimensional SiO2-TiO2 coupled cavity photonic crystal is investigated. In particular the potential application in light amplification is proposed considering the small group velocity that characterizes the propagation at the edge of the resonance band due to the defects. Then, by means of a transfer-matrix method and a mode matching method code, an estimation of the photon lifetime and of the field intensity in a three-coupled cavity-photonic crystal is reported comparing it with those pertaining to a microcavity photonic crystal. This calculation allows us to underline the role of the light–matter interaction time with respect to that of the number of the active medium layers in the optical amplification