bluuebunny/crossref_metadata_2025 huggingface dataset:
Dry Photopolymer Films for Computer Generated Middle Infrared Focusing Elements Fabrication
Authors: Boiko Yuri B. , Calixto Sergio
Published: February 2023

Fabrication of the relief focusing elements are known to include the illumination of light sensitive materials through computer generated /l/ multy-grey-level amplitude mask with corresponding amplitude function of the focusing element /2,3/. In this report the use of dry photopolymer films (see /4/) is discussed. The photopolymer films based on the acrylamide (monomer), polyvinylalcohol (binder), methylene blue (sensitizer) and triethanolamine (initiator) were prepared according to the procedure previously described /4/. The exposure set up used is shown on the fig.1. The photosensitive layer provided sensitivity in the 600-700 nm spectral region, so as a light source 1 the 3 00 Watt halogen lamp with the reflector 2 was used. The filter 3 absorbed the heat radiation to prevent the amplitude mask damaging. The parallel beam at the output was formed by lenses 4. Polymer layer 7 was placed on the glass substrate 8. The direct contact of polymer layer and amplitude mask 6 was provided by glass substrate 5. Polymer layer thickness was 100 μm.
Diffractive-refractive microlens arrays for beam permutation
Authors: Sauer Frank , Jahns Jürgen , Feldblum A. Y. , Nijander C. , Townsend W.
Published: February 2023

The combination of refractive with diffractive elements has already been demonstrated in 1966 [1] and has further been discussed by various authors (see for example [2]). In most cases, diffractive optics has been used to reduce chromatic aberrations of lens systems by making use of the opposite dispersion of diffractive and refractive optical elements. Recent developments in the fabrication of microoptical elements allow one to implement both refractive as well as diffractive microlenses by using lithographic techniques. For optical interconnection applications, the flexibility of lithographically fabricated diffractive optics is of interest for the implementation of beam permutation operations (see for example [3]).
Achromatic Fraunhofer and Fresnel diffraction patterns: theory and experiment
Authors: Andrés P. , Lancis J. , Furlan W.D. , Climent V.
Published: February 2023

The optical Fourier transform provided by an ideal achromatic Fourier transformer is located in a single Fraunhofer plane, but with the same magnification for each wavelength [1]. Similarly, an achromatic Fresnel diffraction pattern results from the in-plane superposition, with the same scale, of the incoherent monochromatic versions of a specific Fresnel pattern generated by the spectral components of the incident light.
Electromagnetic theory of X-ray gratings
Authors: Neviere M.
Published: February 2023

Diffracting and focusing elements become more and more popular in soft and hard X-ray spectral domain in view of achieving studies of spectroscopy, luminescence, photoemission, microscopy, etc … Concerning diffraction elements, i.e. gratings, two main types have to be distinguished. The first type consists of bare metallic gratings, usually gold or platinum coated, which cover a wide range of wavelength, from 6 A° to 1000 A°, and are classical gratings used under grazing incidence. As "classical gratings" with finite conductivity, their theory was already published [1, 2] at the beginning of the 1970's. However, due to the high number of propagating orders resulting from wavelength-to-groove-spacing ratio (λ/d) less than 1/100 or even 1/1000, the use of the Integral Theory was precluded in this spectral domain, at least with the computers available at that time. It is only in 1979 that we recognized [3] that due to the specificities of X-ray gratings, namely low groove-depth-to-groove spacing ratios (h/d) plus refractive indices close to unity, the coupling between the eigenmodes or diffracted orders was weak enough so that it was possible to get accurate results with the Differential Theory by truncating the Fourier series of the field to an order much less than the number of propagating orders. This discovery opened the X-ray domain to the use of electromagnetic theory of gratings, and since that time, the Differential Theory was used to study and optimize many X-ray gratings for Synchrotron Radiation Instrumentation and important space missions [4-5]. A computer software was recently developed in order to determine a given number of grating parameters (e.g. groove depth, incidence, groove spacing …) in order to optimize a desired efficiency in TE, TM polarization or natural light for a specified used. Spectacular agreement was found between theoretical predictions and measurements so that the diffraction of X-rays by a metallic grating can be considered as a well resolved problem. The modal method [6] developed in the mean time and used by several authors led to identical results with comparable computation time.
Highly improved convergence of the coupled-wave method for TM polarization and conical mountings
Authors: Lalanne Philippe , Morris G. Michael
Published: February 2023

Several methods exists to analyze grating diffraction problems by solving rigorously Maxwell's In some circumstances, all these methods suffer from some numerical instabilities and difficulties. We focus on a method originally derived from the integral method, namely the coupled-wave method (RCWA) formulated by Moharam and Gaylord1. This method is known to be slowly converging especially for TM polarization of metallic lamellar gratings. The slow convergence-rate has been analyzed in detail by Li and Haggans2. In this paper, we provide numerical evidence that the coupled-wave method is slowly converging for conical mounts of one-dimensional metallic grating. By reformulating the eigenproblem of the coupled-wave method, we provide numerical evidence that highly improved convergence-rates similar to the TE polarization case can be obtained for conical mounts. Of course, this result can be applied to the case of TM polarization for non-conical mounting, which is a particular case of the general conical mounting diffraction problem. We reveal that the origin of the slow convergence in the original RCWA method is not due to the use of Fourier expansions (as was argued by Li and Haggans), but to an inadequate formulation of the eigenproblem.
Aberration-corrected etched microlens arrays
Authors: Mersereau Keith , Nijander Casimir R. , Townsend Wesley P. , Feldblum Avi Y.
Published: February 2023

Refractive microlens arrays can be made through reactive ion etching of melted photoresist microlenses. We report fabrication of fused silica microlens arrays with reduced aberration by controlling the relative etch rates of silica and photoresist. An example is presented and implications are discussed.
An extensible, diffractive optic system for interconnecting opto-electronic device arrays
Authors: Morrison Rick L.
Published: February 2023

The melding of silicon electronic processing circuits with GaAs quantum well optical modulators and receivers provides the opportunity to significantly increase system communication throughput by virtue of integrated high-speed, free-space, optical channels as demonstrated in a recent experiment1. A second accomplishment of this experiment, the mounting of the optical platform in an electronics cabinet, illustrates the progress toward adapting the optical infrastructure to more traditional packaging schemes. The challenge of blending opto-electronic techniques into contemporary electronic architectures lies in further reducing the opto-mechanical system volume and cost.
Replication process with a 3D-amplitude/phase mask
Authors: Pawlowski Edgar
Published: February 2023

In the last years the interest in low-cost production techniques for integrated optics and diffractive optical elements (DOEs) has rapidly grown. Different methods like embossing, moulding and casting were reported [1,2,3,4]. This technologies are well established for the production of submicron grating structures, like moulded CDs and hot embossed holograms. However, all this methods are not suitable for materials like glasses (e.g. silica) or semiconductors (e.g. InP, GaAs). In order to overcome this problem, grayscale and halftone masks with different gray levels were proposed, were a serie of gray levels corresponds, after a optical lithography process, to different resist depths [5,6]. These structures were finally transferred by dry etching processes to the substrate material. In this paper we present a new 3D-structure replication technique for this wide range of optical and semiconductor materials and for high structure depths. Deep microrelief structures up to 10 μm or more and structures with very high lateral resolution (< 200 nm) can be replicated. Due to the 3D-amplitude/phase mask it is possible to suppress edge ringing by means of modulating the amplitude and the phase of the light. The fabrication process of the mask is based on repeated multi-steps of photolithographic and ion-beam-sputter-deposition techniques. An in situ monitoring system is used to control the optical thickness and the transmission of the mask structures.
Diffractive Optics in an Ultraviolet Satellite Attitude Sensor
Authors: Fritz T. A. , Pledger D. B. , Werner T. R.
Published: February 2023

Honeywell's Earth Reference Attitude Determination Sensor (ERADS) is a wide field of view ultraviolet imaging sensor for satellite attitude determination. The sensor was designed for small satellite applications1, where size, weight, and cost are the primary drivers. Use of the ultraviolet region of the spectrum provides a unique capability to simultaneously image stars, Earth's limb (day or night), and other celestial objects, and to tolerate the sun in the field of view. This is because the solar output is lower relative to the other objects of interest in this waveband, and eliminates the need for expensive and cumbersome sun shields. The field of view consists of a 10° annular region at 71° from axis, and a 10 degree center field. Higher accuracy attitude information is obtained from measurements of stellar location. The accuracy with which these measurements can be made is limited by the number of pixels on the focal plane, the blur spot dimensions, and the photon count rates. The detector array of the sensor was a megapixel CCD. The field of view of the sensor was effectively increased by making use of an array of six folding mirrors, and the field remapping effectively increased the pixel density in the area of interest. The optimal blur diameter for the centroiding algorithms proved to be the width of three pixels, if a photon rate of 50 per star for fourth magnitude stars could be maintained.
Pseudorandom Encoding of Fully Complex Modulation to Bi-Amplitude Phase Modulators
Authors: Cohn Robert W. , Liu Wenyao
Published: February 2023

Pseudorandom encoding is a statistically-based, pixel-by-pixel mapping of complex valued modulations onto modulators that do not produce all complex values.1 The resulting far-field diffraction pattern closely approximates that from the desired, but unimplementable, complex modulation. Since the methed is point-oriented, the desired complex modulation can be synthesized and encoded without resorting to time consuming constrained global optimizations e.g. simulated annealing,2 genetic,3 and Gerchberg Saxton4 algorithms. In addition to reducing design time, the resulting diffraction patterns can have reasonably high diffraction efficiencies and low levels of background noise.
Design of Resonant Grating Filters
Authors: Norton Scott M. , Morris G. Michael , Erdogan Turan
Published: February 2023

Resonant grating filters offer high-contrast, narrowband reflectivity and transmissivity for an incident plane wave. They differ from other optical filters in that they operate on the principle of resonance excitation, rather than a bragg-type or Fabry-Perot effect. The principle of resonance excitation has been equated with the excitation of a leaky waveguide mode.1 Connecting the resonance to a leaky mode excitation has led to new design principles for resonance grating filters. For instance, the ideal waveguide dispersion relation has been used to locate the position of the resonance in wavelength or angle.2 However, connecting resonant width to leaky waveguide excitation has largely been ignored. We will show how the waveguiding concept can be extended to give approximations to resonant width. This approach is based on three different models: homogeneous RCWA3, an approximate homogeneous modal analysis, and an approximate coupled-mode approach. Note, the term homogenous refers to solving the problem without the existence of an incident plane wave field.
Zeroth-Order Complex-Amplitude Modulation by Lamellar Surface Profiles
Authors: Kettunen Ville , Vahimaa Pasi , Turunen Jari , Honkanen Marko , Salminen Olli , Noponen Eero
Published: February 2023

In diffractive optics phase-only elements provide the highest diffraction efficiencies, but they also generate noise in the neighborhood of the signal window W. Moreover, this noise tends to be strongest in the immediate neighborhood of W. In many applications, such as space-invariant optical interconnection, one must suppress the noise from some given spatial-frequency frame around W. This can be accomplished with a phase-only modulating element, but it requires an effective increase of the size of W to include also the frame. Consequently the numerical complexity of performing the design increases considerably.
Subwavelength Diffractive Elements Fabricated in Semiconductor for 975 nm
Authors: Smith R.E. , Warren M.E. , Wendt J.R. , Vawter G.A.
Published: February 2023

Diffractive optical elements can be realized by fabricating surface relief structures with features shorter than the wavelength of light.1-4 These structure have the properties of homogeneous layers of material but with effective indexes of refraction determined by the duty cycle of the surface features. Lateral variations in those duty cycles lead to lateral gradients in refractive index and, potentially, surface elements with very high diffraction efficiencies.
Synthesis of fully continuous phase screens for tailoring the focal plane irradiance profiles
Authors: Dixit Sham , Feit Mike
Published: February 2023

In laser driven inertial confinement fusion systems, it is desirable to produce smooth focal plane intensity profiles [1]. Traditionally, binary random phase plates (RPPs) have been used to produce a focal plane irradiance profile which consists of a smooth Airy function shaped envelope and a superimposed fine scale speckle pattern. The speckle is smoothed by conduction smoothing in the laser produced plasma and/or by externally imposed temporal smoothing methods. Although easy to fabricate and use, the RPPs have very limited flexibility in producing arbitrary shaped irradiance profiles. In addition, the secondary maxima of the Airy profile lead to a 15% loss of the energy from the desired region in the focal plane. This loss of the laser energy requires the operation of the fusion lasers at higher energies thereby increasing their cost of operation. Additionally the scattered energy could also cause optical damage to detection equipment near the target.
Fabrication of large aperture kinoform phase plates in fused silica for smoothing focal plane intensity profiles
Authors: Rushford Mike , Dixit Sham , Thomas Ian , Perry Mike
Published: February 2023

In laser driven inertial confinement fusion systems, it is necessary to produce smooth focal plane intensity profiles [1]. The desired intensity distribution consists of a superGaussian envelope with a superimposed speckle on it. The speckle pattern is smoothed either by the plasma or by other temporal smoothing techniques. Binary random phase plates (RPPs) are inadequate for spatial smoothing as they lead to Airy function envelopes in the far-field and are only 84 % efficient. Furthermore RPPs also introduce large intensity modulations in the propagated intensity past the RPP which can potentially damage the optics downstream from the RPPs.
Speckle-free phase Fresnel holograms and beam shaping elements
Authors: Neto Luiz Gonçalves , Sheng Yunlong
Published: February 2023

Computer-generated holograms (CGH's) have proved effective as non-periodic diffractive elements for beam shaping. The elements are usually designed with the iterative algorithms based on the Gerchberg-Saxton Algorithm [1-3]. However, the initial random phase and the phase freedom in the image plane used in those algorithms introduce speckle noise in the reconstructed image [4]. Several techniques have been proposed for designing speckle-free CGH's.
A New Kind of Diffractive Phase Elements Applied to Wavelength Demultiplexing and Annular Focusing
Authors: Gu Benyuan , Zhang Guoqing , Dong Bizhen , Yang Guozhen
Published: February 2023

In recent years much effort has been devoted to the designs of diffractive optical elements (DOE’s) because of considerable progress in DOE microfabrication technology. In the previous papers various designs of DOE’s have been presented, these elements produce focal annuli for monochromatic illuminating system1, or implement wavelength demultiplexing and straight line or spot focusing.2-5
Z-Scan Measurement in Amorphous As2S3 Thin Film
Authors: Sohn Yeung Joon , Kwak Chong Hoon , Choe Ok Shik
Published: February 2023

Z-scan technique is very useful method for measuring the magnitude and the sign of the nonlinear refractive index due to its simple geometry and high sensitivity compared with nonlinear interferometry, degenerate four-wave mixing, nearly degenerate three-wave mixing, ellipse rotation, beam distortion measurement.[1, 2] With this technique the measurements and analysis for several nonlinear optical materials such as CS2, ZnSe, GaAs, CdTe had been succesfully acomplished by using high power pulse laser.[1-3] In this paper, we present a cw pump-probe z-scan method for determining the optical nonlinearity of an amorphous As2S3 thin film. In an amorphous chalcogenide As2S3, thin film the optical nonlinearity originates from the photostructural changes of the material by band gap illumination (bandgap energy of Eg ≃ 2.5eV corresponding to Ar-ion laser wavelength of 514nm), which results in photodarkening and photoanisotropy. These effects have been extensively investigated as holographic recording medium for optical information processing, polarization hologram and binary phase gratings such as Dammann grating.[4-6]
A Computational Model for Holographic Sensing
Authors: Bakker Ben
Published: February 2023

An existing analytical concept based on spectral decomposition has been developed more than hundred years ago, and is presently close to its limits in terms of performance and reliability, in particular, for complex samples. For molecules, a spectrum is a very complex pattern of sharp lines and continuous bands. So, in a classical spectrometer, detection is pruned to overlapping errors when two or more components of a sample have overlapping lines, and their separation is, generally, a non-unique problem. Indeed, a line can be assigned to, at least, two different transitions (in the same or different atom/molecules in a sample). Such an assignment based on line positions and transitions has limitations, and may not work at all for complex samples. As samples are getting more and more complex, the problem becomes increasingly intractable. In particular, algorithms and data processing to analyze complex spectra become very complex, require sophisticated peak analysis, etc. A mathematical "inversion" procedure for assignment and identification of components (species) also becomes unstable. That is, the current situation has all signs of a critical bottleneck, and requires an innovative approach. Meanwhile, selectivity is the first priority for many industries and applications. For instance, in the field of air toxics detection, the US EPA requires 189 components to be detected and regulated, and it is highly doubtful that any existing spectrometer is able to analyze reliably such a complex gaseous medium.
Measurement and Analysis of Compound Holographic Gratings of Amplitude and Phase
Authors: Wang Y. J. , Fiddy M. A. , Teng Y. Y. , Li G. , Pommet D. A. , Malley L.
Published: February 2023

Holograms recorded in silver halide thin films are transparent when the films are exposed to an inferference pattern of light, developed and bleached. This kind of hologram has been studied by many researchers and is usually called a phase hologram.1,2
GIRO gratings : a novel concept for mirrors with high reflectivity and polarisation selectivity
Authors: Dhoedt B. , Goeman S. , Demeulenaere B. , Baekelandt B. , De Zutter D. , Baets R.
Published: February 2023

In this paper, a novel solution is proposed to the problem dielectric mirrors with high reflectivity. The approach adopted is based on the use of a rectangular, one dimensional grating. It will be shown that these gratings can be designed such that they reflect more than 95 % of the incident optical power in a wide variety of material systems.
Array Generator Design for an Optical Analog-to-Digital Converter
Authors: Mait Joseph N. , Shoop Barry L.
Published: February 2023

Within the context of image processing, digital image halftoning is an important class of analog-to-digital (A/D) conversion. Halftoning can be thought of as an image compression technique whereby a continuous-tone, gray-scale image is printed or displayed using only binary-valued pixels. One method to achieve digital halftoning is error diffusion, wherein the error associated with a nonlinear quantization process is diffused within a local region. One of us (BLS) has developed a neural network architecture based on the mathematical foundation of the error diffusion algorithm that is called an error diffusion neural network [1]. The error diffusion neural network computes the halftoned image asymptotically faster than a conventional Hopfield-type neural network, provides full-rank connectivity across the entire image (other error diffusion techniques provide only local error diffusion), and, because of its parallel implementation, does not generate any artifacts commonly associated with sequential halftoning. Figure 1 is a representation of a smart-pixel-based architecture for an optical implementation of the error diffusion algorithm. The functionality required of the error diffusion neural network is implemented using gallium arsenide (GaAs) and aluminum gallium arsenide (AlGaAs) multiple quantum well modulators. The two-dimensional spatial distribution and intensity weighting required of the error diffusion filter is accomplished using a diffractive array generator. We report here on the design of the array generator.
Subwavelength Structured Narrow-band Integrated Optical Grating Filters
Authors: B Eric , Grann  , Holcomb David E. , Zuhr Raymond A. , Moharam M. G.
Published: February 2023

A unique type of narrow-band integrated optical filter is investigated based on embedding a subwavelength resonant grating structure within a planar waveguide. Current integrated narrow-band optical filters are limited by their size, density of devices that can be produced, overall performance, and ability to be actively altered for tuning and modulation purposes. In contrast, the integrated optical filters described in this work can have extremely narrow bandwidths - on the order of a few angstroms. Also, their compact size enables multiple filters to be integrated in a single high density device for signal routing or wavelength discrimination. Manipulating any of the resonant structure’s parameters will tune the output response of the filter, which can be used for modulation or switching applications.
Interference effects in diffractive beam shaping elements
Authors: Rossi Markus , Hessler Thomas
Published: February 2023

An increasing number of commercially available and proprietary design algorithms based on scalar or electromagnetic theory allow the calculation of a large variety of diffractive optical elements (DOEs) with excellent performance and high diffraction efficiencies. However, micro-structuring technologies used for the fabrication of DOEs have tolerances and limitations that reduce the measured diffraction efficiencies to below the theoretical values. For some applications not only the absolute value of the diffraction efficiency is of concern, but at least the same importance has to be paid to the spatial distribution and the optical effects of the stray light. Collimating and beam shaping elements are typical examples for the latter case. Due to interference effects with the "signal beam", very small amounts of stray light can already reduce the optical performance significantly, e.g. characterized by an irradiance uniformity. Especially for applications with beam shaping DOEs in micro-systems these effects get more critical since the short propagation lengths do not allow a complete separation of the desired and the stray light.
Symmetry of the field transmitted by periodic metallic grids
Authors: Sentenac A. , Maystre D.
Published: February 2023

The symmetry properties of the diffracted orders of gratings in the resonance domain are frequently used in diffractive optics [1]. For example, a beam-splitter element or star coupler (fan-out to N) is obtained with a grating that produces N equal-efficiencies diffraction orders. In general, those gratings are synthesized by using a parametric optimization algorithm combined to rigorous electromagnetic theory. Their shape is then precisely defined. However, in certain cases, the identity of the values of the transmitted efficiencies stems from simple considerations on the symmetry of the field at the bottom of the grid and it does not require drastic specifications on the motif of the grating. It is shown in [2] that lamellar perfectly conducting gratings produce two symmetric transmitted orders with equal amplitude if they are illuminated under -1 Littrow mounting and if the width a of the groove satisfies λ/2<n
g
a<λ in s-polarization and n
g
a <λ/2 in p-polarization, (where λ is the wavelength of the incident beam, n
g
is the refractive index of the material filling the groove, n
1
and n2 are the refractive indices of the superstrate and substrate, respectively, see Fig. 1).
Electromagnetic analysis of waveguide Bragg reflectors
Authors: Vahimaa Pasi , Turunen Jari
Published: February 2023

Bragg gratings are used extensively in fiber and integrated optics as,
e.g., input/output couplers and semiconductor-laser mirrors.
Typically these devices are analyzed using coupled-mode methods,which
are reasonably accurate at least for weakly modulated structures.
However, such methods can not model out-of-plane scattering or the
effect of grating irregularities. In this paper we model
distributed-feedback Bragg reflectors using a rigorous electromagnetic
formalism adapted from the theory of conventional gratings much as
described in Ref. 3. The method facilitates precise analysis of
practically any waveguide grating structure, even in the presence of
irregularities introduced, e.g., by fabrication errors.
Fabrication and Simulation of Blazed Gratings with Inherent Antireflection Structured Surfaces
Authors: Nikolajeff Fredrik , Heine Claus
Published: February 2023

Subwavelength structured surfaces can be used as very efficient antireflection (AR) coatings, narrowband filters or polarizing elements [1]. In industry, AR coatings and filters are typically produced by using thin-film techniques. Sub wavelength structures can avoid many of the problems encountered in thin-film approaches, and be replicated at low cost. Subwavelength structures also have the potential to be combined with micro-optical elements such as lenses, gratings or kinoforms. However, previous studies have either been focused on the analysis of pure subwavelength gratings [2] or micro-optical elements coated with thin films [3].
Vector-Based Analysis of Axially Symmetric and Conducting Diffractive Lenses
Authors: Prather Dennis W. , Shi Shouyuan , Mirotznik Mark S. , Mait Joseph N.
Published: February 2023

The analysis of diffractive lenses that have feature sizes comparable to the illumination wavelength require a rigorous, or vector-based, model of diffraction. However, most techniques presented in the literature for the vector-based analysis of such elements are limited to two-dimensional (2D), or cylindrical, lenses. In this paper we present a vector-based technique for the analysis of three-dimensional (3D), or spherical, diffractive lenses that are perfect electrical conductors (PEC).
Fabrication of microprisms for planar-optical interconnections using analog gray-scale lithography with high energy beam sensitive glass
Authors: Gimkiewicz Ch. , Hagedorn D. , Jahns J. , Kley E. B. , Thoma F.
Published: February 2023

Integrated planar free-space optics is a viable concept for building compact systems for interconnection and sensor applications. Micro-optical elements are integrated on a single substrate to guide the light signals traveling inside the substrate [1]. Optoelectronic devices are bonded on the substrate by hybrid integration techniques such as flip-chip bonding. For interconnection applications, vertical-cavity surface emitting laser diodes (VCSELs) are of particular interest as fast 2-D input arrays.
High Efficiency Binary Blazed Grating Waveguide Couplers
Authors: Watson Michael D. , Abushagur Mustafa A.G. , Ashley Paul R. , Cole Helen
Published: February 2023

Blazed grating features result in a modification to the Bragg which yields only a single output radiation mode (either substrate or cladding). [1]. Since blazing requires a triangular grating line shape, fabrication can be difficult. As a simplification, a discrete step approximation is often used to approximate a blazed structure. However, the discrete approximation requires multiple exposure steps making the fabrication process complex. The fabrication process can greatly simplified by approximating the blazed grating line shape by a periodic rectangular grating with a varying duty cycle [2]. Thus, the process used to fabricate periodic rectangular gratings can be used to fabricate the binary approximation of a blazed grating. Dividing the blazed grating structure into several (I), substructures, results in a substructure (i), each having a different discrete refractive index based on their location along the slope as shown in Figure 1.
Mass-transport gallium-phosphide refractive micro-lenses for diode array reconfiguration
Authors: Ballen T.A. , Leger J.R.
Published: February 2023

Laser diode arrays are useful for pumping of fiber and solid-state lasers due to their high power and narrow linewidth. In addition, multi-mode fibers offer a convenient method of transporting light for applications such as illumination and materials processing. However, the pumping geometry of end-pumped lasers or the waveguide shape of multi-mode fibers often does not match the diode array illumination pattern (approximately a line source). More efficient light-coupling is possible through a geometric transformation of the individual diode sources to more closely match the desired geometry1. In this paper mass-transport smoothing is used to fabricate arrays of off-axis aspheric refractive collimating lenses and prisms for efficient reconfiguration of a linear laser diode. The modeling and design of the aspheric lenses is described and the performance characteristics of a fabricated prism demonstrated.
Holographic Optical Element For A Dual Focus Optical Head
Authors: Komma Yoshiaki , Kuwamoto Shin-ichi , Aikou Hideki , Urairi Kenichiro , Yamagata Michihiro , Tanaka Yasuhiro
Published: February 2023

A high density optical disk format named DVD adopts a 0.6 mm disk to simultaneously use a high numerical aperture (NA) lens and gain tolerance of disk tilt.1 Because of the immense popularity of the CD format, it is important to playback the current widely used Compact Discs (CDs) on DVD format players. This requires an optical head that can read both conventional 1.2 mm disks and the new 0.6 mm disk. To read both disks with the same optical head, it is necessary to overcome spherical aberration caused by the difference in disk thickness.
Diffractive Optics in the Thomson Group
Authors: Rollin J. , Puech C. , Rogers P. J.
Published: February 2023

Two parameters govern the performance of a surface-relief diffractive:- the phase function, given by the radial positions of the diffractive steps, which provides a means for counterbalancing both chromatic aberration and spherochromatism;- the diffractive step heights, and the zone shapes between these steps, dictate the grating efficiency within a selected diffractive order.
Talbot array illuminators for high intensity compression ratios
Authors: Klaus Werner , Kodate Kashiko
Published: February 2023

The Talbot array illuminator (TAIL) is well known as an efficient diffractive optical element that transforms, in the near field, a spatially coherent monochromatic wave into a large number of bright spots. Its performance is generally measured in terms of the highest achievable intensity compression ratio, i.e., the maximum achievable ratio of the array illuminators grating cell area to the area of the bright spot (or spots) formed within the cell area.
Monte Carlo investigation of separation of two absorbers in topographic image
Authors: Kadoya Takuma , Moriwaki Eizo , Okada Eiji
Published: February 2023

Near infrared topographic imaging is an effective instrument to image brain-cortex activity. The image is reconstructed by changes in light intensity detected with multi-channel source-detector pairs. However, light scattering in tissue prevents us from improving the spatial resolution of the reconstructed image, hence it is important to evaluate the effect of scattering on the spatial resolution of the reconstructed image. In this study, separation of two absorbers in topographic image is investigated by Monte Carlo simulation to evaluate the spatial resolution of topographic imaging. Because of heterogeneity of tissue, especially presence of low scattering CSF layer affects the light propagation in the adult brain. The adult head model consists of three layers including a low scattering medium. In case where the separation of two absorbers is greater than the distance between adjacent measurment points, the two absorbers can be separated in the topographic image.
An estimation of the photon tomography resolution power using statistical simulation
Authors: Fomenko Viktor N. , Shvarts F. M. , Shvarts M. A.
Published: February 2023

The resolution power of photon tomography methods is an important characteristic and it is mainly determined by the photon trajectory uncertainty. To estimate this quantity we calculate the root-mean-square deviation of photon trajectories from the mean path, the initial and final space-time points of trajectory being fixed. We apply the Monte-Carlo procedure in order to calculate the photon-travel deviation variance. In this paper we confine ourselves to infinite isotropically scattering media.
Application of fluorescence-interference microscope for monitoring of dry weight dynamics and drug distribution within living cells
Authors: Levin Gennady G. , Bulygin Theodore V. , Kalinin Eugene V. , Vishnyakov Gennady N. , Goryainova Irene V.
Published: February 2023

The authors have proposed and tested the new type of the microscope with superimposed interference and fluorescence images of the living cell. The fluorescence image gives the information about the distribution of drugs in different parts of the cell. Interference microscopy technique allows implementing the quantitative analysis of a living transparent cell, for example, to measure dry cell weight and cell density spatial distribution. Interference microscopy makes possibility the observation cell vital activity at dynamics. Computer-aided processing of interferograms using phase shift technique, allows carrying out continuous (over 12 hours and more) monitoring of living cells quantitative parameters with time interval between measurements less than one minute. RMS error for dry weight of non-living fixed test object using this microscope is about 1%.
Dynamic Views of Living Cell Fine Structure Revealed by Birefringence Imaging
Authors: Oldenbourg Rudolf
Published: February 2023

We have been developing and applying a new type of polarized light microscope, the new "Pol-Scope", which dramatically enhances the unique capabilities of the traditional polarizing microscope. In living cells, without applying exogenous dyes or florescent labels, we have studied the dynamic organization of filamentous actin in neuronal growth cones and improved the efficiency of spindle imaging for in- vitro fertilization and enucleation procedures.
Full field OCT with thermal light
Authors: De Martino A. , Carrara D. , Drévillon B. , Schwartz L.
Published: February 2023

A very simple OCT system has been developed, based on a Linnik interferometric microscope with its reference mirror mounted on a piezoelectric translator. The geometrical extension of the optics allows efficient illumination of this device with a low power (3 W) light bulb, yielding full field interferometric images at 50 Hz acquisition rate with a fast CCD camera. Due to the very broad spectral width of the light source and camera response, an axial resolution better than 2 μm is easily achieved. Tomographic images of cell smears are shown.
Autocorrelation free spectral OCT techniques in eye imaging
Authors: Wojtkowski M. , Kowalczyk A. , Leitgeb R. , Fercher A.F.
Published: February 2023

Two improved spectral Optical Coherence Tomography (OCT) techniques: a differential and complex methods are compared with classical spectral OCT. Both methods enable to eliminate parasitical terms. Additionally the complex spectral OCT doubles the useful depth range. Ophthalmic applications of above-mentioned techniques are presented.
Three-dimensional structure of the lamina cribrosa of the living eye
Authors: Beuerman R. , Palkama A. , Reynaud J. , Nguyen N. , Kikuchi H. , Kalia R.
Published: February 2023

Visualization of the complex structure composed of oriented axons leaving the retina in a loose connective tissue matrix has been carried out in living tissue using white light confocal microscopy. Optical sections were acquired at normal and elevated intraocular pressures. A 3D model of the lamina was produced and techniques were developed to study the effects of intraocular pressure on the structural integrity of the lamina cribrosa.
Diagnosis of dental caries using Quantitative Light-induced Fluorescence
Authors: Amaechi Bennett T. , Higham Susan M.
Published: February 2023

Current dental diagnostic methods can detect caries but cannot quantify the mineral status of the lesion. Quantitative Light-induced Fluorescence (QLF) measures the percentage fluorescence radiance change of demineralised enamel with respect to surrounding sound enamel, and relates it directly to the amount of mineral lost during demineralisation. Demineralisation of teeth to produce caries-like lesions and the subsequent remineralisation of the lesions were monitored quantitatively and longitudinally with QLF. The influence of factors such as presence of plaque or saliva, lesion staining, lesion magnification, tooth thickness and developmental hypominerahsation, on the reproducibility of QLF imaging and analysis were investigated. Results showed that the integrated fluorescence change (hence the mineral loss) increased linearly with demineralisation time and decreased with increasing remineralisation time. Caries detection was limited by saliva or plaque, but enhanced by staining. QLF could not discriminate between developmental hypomineralisation and caries. Neither the variation in tooth thickness nor lesion magnification within the limit of a sharp image made a significant difference in QLF analysis. It was concluded that QLF could detect and quantitatively monitor the mineral changes in an incipient caries on a longitudinal basis, however detection may be limited by the presence of saliva or plaque and enhanced by staining.
An Optical Pathlength Meter for Near Infrared Spectroscopy
Authors: Tullis Iain D. C. , Delpy David T.
Published: February 2023

Many commercial clinical Near Infrared Spectroscopy (NIRS) instruments rely upon estimates of the optical pathlength of tissue based upon the optode spacing multiplied by an average differential pathlength factor(DPF) for the tissue under investigation. Significant variation in the published DPF is the major source of error in the NIRS data quantification. To reduce this error, an inexpensive, stand-alone, single wavelength, single frequency optical pathlength meter based on the homodyne phase method was constructed for clinical use with an existing NIRO 300 instrument (Hamamatsu Photonics KK). The construction and testing of the optical pathlength meter is discussed.
Time-Resolved Autofluorescence Spectroscopy of the Bronchial Mucosa for the Detection of Early Cancer: Clinical Results
Authors: Glanzmann Thomas M. , Uehlinger Pascal , Ballini Jean-Pierre , Radu Alexandre , Gabrecht Tanja , Monnier Philippe , van den Bergh Hubert , Wagnières Georges
Published: February 2023

Time-resolved measurements of endogenous tissue autofluorescence were carried out on the bronchial mucosa of 18 patients during endoscopy by the means of an optical fibre-based spectrometer. The objective was to assess the fluorescence lifetime as a new contrast parameter between normal and malignant tissue and to explain the origin of a previously observed contrast in fluorescence intensity. The intra- and interpatient variation of tissue autofluorescence intensity and decay on normal tissue was determined, with the outcome that a strong fluctuation in autofluorescence intensity but not in lifetime was observed on the normal tissue. Preliminary results were obtained by comparing fluorescence decays on normal mucosa and dysplasia/carcinoma in situ. No significant change in fluorescence decay nor in spectrum between 510 and 650 nm was found. Measurements in parallel with an endoscopic autofluorescence imaging device, on the other hand, indicated a contrast in intensity and spectrum on the same lesions. This suggests that the spectral contrast might be due to an enhanced blood concentration in deeper-lying layers of the lesion to which the optical fibre-based contact measurements are less sensitive. The difference in intensity might be due to a lower concentration in fluorophores or to the thickening of the epithelium in the neoplastic mucous membrane. However, no indication of fluorescence quenching in the upper layers of the mucous membrane was found as the reason for the reduced fluorescence intensity. The fluorescence decays showed a quite stable behaviour with three decay times of 6.9 ns, 2.0 ns and 0.2 ns in the spectral range between 430 and 680 nm. This can be an indication that there is one dominant fluorophore involved, the calculated decay times suggest that it might be elastin. However, a slight spectral dependence of the fluorescence decays lead to the presumption that there is a contribution from other fluorophores, probably flavins and NADH.
Clinical results with UV-excited autofluorescence spectroscopy in different organs
Authors: Stepp Herbert , Hohla Alexander
Published: February 2023

UV-excitation with 308 nm was applied clinically to normal and diseased tissues from the urinary bladder, the brain and the lungs. With a multifiber catheter, fluorescence spectra were recorded and evaluated using the most significant wavelength ratios. Correlation with histology showed the following sensitivities / specificities for the detection of malignant tissue: bladder 90% / 81%, brain 62% / 100%, lungs 80% / 76%. Compared to 5-ALA induced PPIX-fluorescence (bladder), a higher specificity was observed. The results obtained intraoperatively were compared with UV-imaging and spectroscopy on frozen tissue sections.
Influence of Strong Static Magnetic Field on Human Cancer HT 1080 Cells
Authors: Rodins Juris , Korhovs Vadims , Freivalds Talivaldis , Buikis Indulis , Ivanova Tatjana
Published: February 2023

The aim of this study was to investigate strong uniform magnetic field influence on the human cancer cells HT 1080. The cells were treated with magnetic field of intensity 1,16 Tesla and with anticance agent – cis-platinum 0.025 mg/ml or vincristinum 2-3 ng/ml. The intact and the treated cell samples were incubated in a medium with acridine orange (AO). The magnetic field after 15 minutes of influence significantly increased cytoplasmic red fluorescence. Increased AO accumulation in lysosomes suggested to cancer cell metabolic activity stimulation.
Separation of myoglobin and hemoglobin in isolated perfused pig heart
Authors: Rauh Robert , Hiller Michael , Trinks Tobias , Kessler Manfred
Published: February 2023

For the quantitative determination of hemoglobin concentration in heart muscle it is important to distinguish between myoglobin and hemoglobin, two dyes with very similar optical absorption properties. With an isolated perfused pig heart model and EMPHO II SSK we measured tissue spectra in the visible range before and after adding erythrocytes to the perfusate. By calculating light intensity differences we were able to show spatial hemoglobin distribution in heart muscle.
Effects of a superpulsed CO2 laser on human teeth
Authors: Murgo Dírian O. A. , Cerruti Blanche , Redígolo Marcela L. , Chavantes Maria C.
Published: February 2023

The effects of laser exposure on mineralized tissues like enamel have been explored for years as a technique to remove caries and for dental hard-tissue preparation. However the efficiency of this technique has been questioned. In this work, six freshly-extracted third molars were irradiated by a superpulse of CO2 laser, generally used in Transmyocardio Revascularization, and submitted to Scanning Electron Microscopy (SEM) analyzes. The cavities caused by laser irradiation on the dental tissues were analyzed considering its shape and depth. The CO2 superpulse presented a high efficiency in the removal of dental mass and no sign of carbonized tissue was found on the ablated surface. All cavities generated by laser irradiation presented a conic shape with average depth depending on energy density applied.
Antidiabetics and diuretics show phototoxicity in HaCaT cells
Authors: Selvaag Edgar , Petersen Anita B. , Gniadecki Robert , Thorn Tine , Wulf Hans Christian
Published: February 2023

The antidiabetics tolbutamide, glibenclamide, and glipizide, and the diuretics bendroflumethiazide, butizide, furosemide, hydrochlorothiazide, and trichlormethiazide were investigated for potential phototoxicity in the HaCaT cell line. The cells were incubated with the drugs and then exposed to UVA1 irradiation. The effects of the antioxidants L-ascorbic acid, and α-tocopherol on oxidative DNA damage were assessed. Bendroflumethiazide, furosemide, hydrochlorothiazide, trichlormethiazide, or tolbutamide induced dose-dependent phototoxicity. Cells incubated with bendroflumethiazide, tolbutamide, and glibenclamide, and irradiated with UVA1 demonstrated an increased oxidative DNA damage. Pre-treatment with L-ascorbic acid, or α-tocopherol, suppressed the UVA-induced DNA damage in cells incubated with 1 mM of bendroflumethiazide, furosemide, glibenclamide, glipizide, tolbutamide, and trichloromethiazide, further implying the involvement of reactive oxygen species in the phototoxic DNA damage. These results may indicate a link between phototoxic and photocancerogenic potential of the sulfonamide-derived oral antidiabetic and diuretic drugs, as it has previously been recognized for psoralen, chlorpromazine, and fluoroquinolones. Excessive exposure to UV light may be deleterious for patients treated with these drugs.
Nonlinear effects inside corneal tissue after fs-photodisruption
Authors: Heisterkamp Alexander , Ripken Tammo , Lubatschowski Holger , Welling Herbert , Drommer Wolfgang , Luetkefels E. , Mamom T. , Ertmer Wolfgang
Published: February 2023

In order to perform refractive surgery, fs-laser pulses were focussed into animal cornea. During histo-pathological analysis by light- and transmission-electron-microscopy new side effects of fs-photodisruption were found. Due to the high intensities at the focal region, self focussing followed by further nonlinear effects is observed, leading to streak formation inside the cornea and several micro-breakdowns on the sub-micron scale. The nature and origin of these streaks are further investigated.