bluuebunny/crossref_metadata_2025 huggingface dataset:
A Wedge Made in an Artificial Dielectric
Authors: Giaconia C. , Torrini R. , Murad S. , Wilkinson C.D.W.
Published: February 2023

Conventional diffractive optical components require fabrication of an approximation to a surface shape and to achieve high efficiency, it is necessary to use multiple levels to build up the desired shape. For say 16 steps, four masking steps are required and each has to be accurately aligned. The overall process is time-consuming and does not have good yield. However the phase of the light can be controlled locally by using a series of slots of different widths provided these slots are narrow enough to avoid diffraction - thus forming an artificial dielectric. The key point is that the slots all have same depth and so only a single lithographic step is required.

We have designed artificial dielectric components using a hybrid technique that combines Rigorous Coupled Wave Theory (RCWA) and Effective Medium Theory (EMT). The model allows for the constraints imposed by fabrication (minimum linewidth and maximum aspect ratio of features) to be included automatically in the optimisation of the design. The first design is for a wedge, to be built in Gallium Arsenide for operation at a wavelength of 1.15 μm. The design has a theoretically diffraction efficiency greater than 90%.

The designed pattern is written in electron beam resist (PMMA) using a Leica Beamwriter. After development the pattern is transferred into an 100 nm thick layer of silicon oxide deposited by plasma enhanced chemical vapour deposition. This is then used as the masking layer in the transfer of the pattern into an epitaxial GaAs film on a GaAs substrate. The oxide layer is removed by wet etching prior to testing.

The wedge has an overall period of 2.3 μm and is divided into seven slots with a minimum linewidth of 70 nm. The etch depth is 740 nm. Initial devices gave a diffraction efficiency of greater than 80% - further details of the device performance will be given.
Arrays of infrared micropolarizers
Authors: Nordin Gregory P. , Meier Jeffrey T. , Deguzman Panfilo , Barbour Blair , Jones Michael W.
Published: February 2023

High spatial frequency metal gratings have long been recognized as an effective polarizer option for the infrared portion of the spectrum.1 Numerous applications can benefit from the development of arrays of such wire-grid polarizers in which subsets of the polarizers have arbitrary angular orientations. In this paper we describe the design and fabrication of an array of small aperture polarizers (i.e., micropolarizers) for the 3-5 μm wavelength range.
Micromachining for micro-optics
Authors: Wu Ming C.
Published: February 2023

We report on the application of the emerging micromachining technology for fabrication of micro-optics as well as its integration with microactuators for adaptive control and dynamic alignment.
Vector Radiation Coupling Method for High Efficiency and High Uniformity Lightguide
Authors: Shinohara Masayuki , Tei Masataka , Aoyama Shigeru , Takeuchi Masashi
Published: February 2023

Lightguides with LED light sources are becoming important components in the application of LCDs for mobile use, because of their thin structures and light weight. Unfortunately, conventional lightguides suffer from poor performance, such as a non-uniform brightness , and this results in poor image and a low efficiency which leads to high power consumption.
Diffractive optic power monitor for use with a VCSEL source
Authors: Fritz B. , Cox J.A , Werner T. , Gieske J.
Published: February 2023

Diffractive optical elements (DOE’s) were designed and fabricated to provide a means both for monitoring vertical-cavity-surface-emitting-laser(VCSEL) output power and for coupling the VCSEL output onto a fiber. The design put two DOE’s on opposite sides of a glass cover positioned over the VCSEL header/can. The power monitor DOE, located on the inner surface of the cover glass, operates in reflection and focuses ~2% of the emitted radiation into an annular ring centered on the VCSEL. Approximately 88% of the transmitted light is in the zero order and is available for focusing on to a fiber by a second DOE located on the back (outer) surface of the cans cover glass.
Laser printer scan lens with diffractive optics
Authors: McIntyre Kevin J. , Morris G. Michael , Dunn Susan , Rumsey Karen , Ossman Ken
Published: February 2023

A scan lens for a laser printer system consists of an F-θ lens and a scanning element, typically a polygon mirror. Due to mechanical wobble and facet-to-facet misalignment, a polygon mirror tends to steer the focused beam out of the intended scan line and therefore requires some form of optical compensation. The most common method1 makes use of anamorphic optical elements. Traditionally, lenses based on this approach contain either a toroidal surface or a reflective cylindrical field lens, both of which are relatively expensive. It is possible to use a diffractive surface to replace the need for either of these surface types. Non-toroidal hybrid scan lenses have been discussed previously2,3. These designs were limited to rotationally-symmetric geometries and therefore could not be used with polygon mirrors. This paper discusses the design, fabrication, and testing of a prototype diffractive scan lens for a 600 dpi laser printer system.
Hybrid optics in dual waveband infrared systems
Authors: Wood A. P. , Rogers P. J. , Conway P. B. , Manning P. A.
Published: February 2023

Diffractive optics in the form of hybrid elements manufactured by single point diamond turning are now well-established and widely used in both mid-wave and long-wave infrared optical systems. The fundamental advantages, based on the reduced element-count, can have a significant impact on cost, mass and overall complexity
Ring toric optics for optical data-storage applications
Authors: Descour Michael R. , Simon Daniel I.
Published: February 2023

Ring-toric lenses are optical elements of use in optical data storage as focus-error and track-error sensing elements.1,2
Short pulsed diode lasers as an excitation source for time-resolved fluorescence applications and confocal laser scanning microscopy in PDT
Authors: Kress Matthias , Meier Thomas , El-Tayeb Tarek Abd Allah , Kemkemer Ralf , Steiner Rudolf , Rück Angelika
Published: February 2023

This article describes a setup for subcellular time-resolved fluorescence spectroscopy and fluorescence lifetime measurements using a confocal laser scanning microscope in combination with a short pulsed diode laser for fluorescence excitation and specimen illumination. The diode laser emits pulses at 398 nm wavelength with 70 ps full width at half maximum (FWHM) duration. The diode laser can be run at a pulse repetition rate of 40 MHz down to single shot mode. For time resolved spectroscopy a spectrometer setup consisting of an Czerny Turner spectrometer and a MCP-gated and -intensified CCD camera was used. Subcellular fluorescence lifetime measurements were achieved using a time-correlated single photon counting (TCSPC) module instead of the spectrometer setup. The capability of the short pulsed diode laser for fluorescence imaging, fluorescence lifetime measurements and time-resolved spectroscopy in combination with laser scanning microscopy is demonstrated by fluorescence analysis of several photosensitizers on a single cell level.
A new dispersion compensation technique for Partial Coherence Interferometry (PCI) and Optical Coherence Tomography (OCT)
Authors: Fercher A. F. , Hitzenberger C. K. , Sticker M. , Zawadzki R. , Karamata B. , Lasser T.
Published: February 2023

In this paper a numerical a posteriori depth-variant dispersion compensation technique for PCI and OCT depth-scan signals is presented. This technique is based on numerical correlation of the depth-scan interferometer signal with a depth-variant kernel. Examples of dispersion compensated depth-scan signals obtained from microscope cover glasses are presented.
Numerical solution techniques to the time-dependent Maxwell for highly scattering media
Authors: Mandel S. , Menon S. , Harshawardhan W. , Su Q. , Grobe R.
Published: February 2023

We discuss how a spectral-domain method in combination with a split-operator technique can be used to calculate exact solutions of the time-dependent Maxwell We apply this technique to study the propagation of a light pulse through an inhomogeneous medium consisting of practically arbitrarily shaped dielectric and metallic materials.
Oxygenation Measurements with Optical Coherence Tomography
Authors: Faber Dirk J. , Mik Egbert G. , van der Meer Freek J. , Aalders Maurice C. G. , van Leeuwen Ton G.
Published: February 2023

The feasibility of using Optical Coherence Tomography (OCT) for oxygenation determination of whole blood was investigated on porcine blood samples. Our data show a sensitivity in the OCT spectral content to changes in oxygenation that qualitatively correspond to expectations based on the absorption spectra of oxidized hemoglobin and hemoglobin.
Multi-Photon Fluorescence Imaging through Biological Tissue and Image Reconstruction
Authors: Gan Xiaosong , Gu Min
Published: February 2023

In this paper, image formation under single-photon (1-p), two-photon (2-p) and three-photon (3-p) fluorescence imaging through turbid media which consist of different sized scatterers has been investigated in detail. It has been demonstrated that the size of scattering particles plays an important role in determining whether to use 1-p, 2-p, or 3-p excitation. For small scatterers, where Rayleigh scattering is dominant, multi-photon excitation provides significantly better resolution. Such improvement reduces dramatically for large scatterers, where Mie scattering becomes dominant. Another disadvantage of using multi-photon fluorescence excitation in highly scattered media is that penetration depth is limited by fast dropping of signal strength in deep tissue imaging. In this paper, we introduce a deconvolution method with a novel concept of the effective point spread function, which is effective in restoring the loss of imaging resolution caused by multiple scattering in a tissue medium.
Experimental demonstration of a fast analytical method for modeling photon propagation in diffusive media with arbitrary geometry
Authors: Ripoll Jorge , Ntziachristos Vasilis , Economou Eleftherios N.
Published: February 2023

Quantitative measurements of diffusive media, in spectroscopic or imaging mode, rely on the generation of appropriate forward solutions, independently on the inversion scheme employed. For complicated boundaries, the use of numerical methods is usually pursued due to implementation simplicity, but this results in great computational needs. Even though some analytical expressions are available, an analytical solution to the diffusion that deals with arbitrary volumes and boundaries is needed. We use here an analytical approximation, the Kirchhoff Approximation or the tangent-plane method, and put it to test with experimental data in a cylindrical geometry. We examine the experimental performance of the technique, as a function of the optical properties of the medium and demonstrate how it greatly speeds up the computation time when performing 3D reconstructions.
Study of laser induced normal human skin in vivo autofluorescence spectra
Authors: Fu S. , Chia C.T. , Lee P. , Krishnan S. M.
Published: February 2023

The results of the experimental investigation of laser induced autofluorescence (LIAF) spectra of normal human skin in vivo are presented. The autofluorescence (AF) spectra changes of skin in vivo during continuous exposure to 442nm Helium-Cadmium laser light are measured. 28 volunteers' arm and hand skin have been detected via non-invasive optical spectroscopy detection system. The methods explore the potentiality of the application of the LIAF technique in clinical skin disease diagnosis.
Application of low scattering photon correlation spectroscopy for blood monitoring
Authors: Meglinski Igor V. , Korolevich Alexander N. , Greenhalgh Douglas A.
Published: February 2023

Extension of the photon correlation spectroscopy (PCS) technique in low scattering regime was employed to the samples of whole blood studied. A few times scattered tight from a weak helium-neon laser beam incident on the cuvette with the blood sample was detected by a photo-multiplier, and both temporal intensity autocorrelation functions and power spectra were measured with digital autocorrelator and spectrum analyzer. The potentialities of the qualitative and quantitative determining of the structural characteristics of blood elements are demonstrated. To analyze the blood samples we propose to use the PCS technique extended for the transition regime of scattering from single to multiple. The studies made permits the use of the technique for thein vitroclinical blood testing.
Application of NIR spectroscopy in the assessment of diabetic foot disorders
Authors: Schleicher E. , Hampel U. , Freyer R.
Published: February 2023

Diabetic foot syndrome (DFS) is a common sequel of long-term diabetes mellitus. There is a urgent need of noninvasive, objective and quantitative diagnostic tools to assess tissue viability and perfusion for a successful therapy. NIR spectroscopy seems to be qualified to measure local capillary hemoglobin saturation of the outer extremities in patients with progressive diabetic disorders. We investigate how NIR spectroscopy can be applied to the assessment of diabetic foot problems such as neuropathy and angiopathy. Thereby we use spatially resolved spectroscopy in conjunction with a specially developed continuous-wave laser spectrometer. Comparison of intra- and interindividual measurements is expected to yield quantitative measures of local tissue viability which is a prerequisite for a successful therapy.
Optical body fat measurement might contribute to the search for a predictor of type-2 diabetes mellitus
Authors: Tafeit Erwin , Horejs Renate , Sudi Karl , Berg Aloys , Reibnegger Gilbert , Möller Reinhard
Published: February 2023

The optical device LIPOMETER allows for non-invasive, quick, precise and safe determination of subcutaneous fat distribution, so-called subcutaneous adipose tissue topography (SAT-Top).

Previously we showed how the high-dimensional SAT-Top information of women with type-2 diabetes mellitus (NIDDM) and a healthy control group can be analysed and represented in low-dimensional plots by applying special artificial neural networks (ANNs). Three top-down sorted subcutaneous adipose tissue compartments were determined (upper trunk, lower trunk, legs). NIDDM women provided significantly higher upper trunk obesity and significantly lower leg obesity ('apple' type), as compared with their healthy control group.

Now we apply these ANN results on SAT-Top measurements of young and healthy women, comparing their individual subcutaneous fat pattern to the body fat distribution of NIDDM women and to the „normal fat development" of healthy women. Some of these young and healthy women provide a subcutaneous fat distribution very similar to the SAT-Top results of NIDDM women, which might increase their risk for this disease later in life.
First experimental experience in adjuvant intraoperative photodynamic therapy (AIOPDT) in S117 sarcoma in mice
Authors: Winkler S , Prosst R.L. , Haase T , Chr Flechtenmacher , Stern J , Gahlen J.
Published: February 2023

The effectiveness of photodynamic therapy (PDT) as an adjuvant treatment for diverse malignant tumors has been investigated in numerous studies. The therapeutic success and extent of side effects of PDT is mainly determined by the applied photosensitizer (PS) and laser energy. Adjuvant intraoperative photodynamic therapy (AIOPDT) using the PS mTHPC (meso-Tetrahydroxyphenylchlorin) causes selective tumor cell death when combined with laser irradiation of a PS specific wavelength (652 nm). Our study proved AIOPDT as an efficient modality to significantly increase postoperative recurrence-free survival after R1/R2 resection of a subcutaneously implanted soft tissue sarcoma in mice. We used mTHPC in a dose of (0,3 mg/kg BW) and a laser light energy of 5 Joule (irradiation time: 50 seconds). First results showed an increase of postoperative recurrence-free survival (Median: 103 days) in 5 animals treated with AIOPDT compared to a control group of 7 animals (Median: 20 days). The tissue specific accumulation of mTHPC was determined by point spectrofluorometry and showed a 2.28 higher PS-accumulation in the tumor center, tumor bed (1.5) and overlying skin (3.8) compared to muscle tissue (1.0) as reference parameter. Our first experimental data recommend AIOPDT to be an efficient adjuvant method to prolonge recurrence-free survival after tumor resection.
Fluence rate effects in meta-tetra(hydroxyphenyl)chlorin (mTHPC) photosensitized HT29 multiceli tumor spheroids Comparative study with Colo26 spheroids
Authors: Maugain Estelle , Coutier Stéphanie , Bezdetnaya Lina N. , Marchai Sophie , Merlin Jean-Louis , Didelon Jacques , Guillemin François
Published: February 2023

The present study evaluates the impact of the fluence rate of red light irradiation (λ = 650 nm) on photodynamic efficacy in mTHPC-sensitized HT29 and Colo26 spheroids. Photocytotoxicity, computed as product of the cell yield and plating efficiency, increased progressively when the fluence rate was reduced from 90 to 30 mW cm-2 in both types of spheroids. The observed photocytotoxicity was mainly due to an immediate rather than a delayed cell death for HT29 spheroids. An opposite effect was observed for Colo26 spheroids. The plausible explanations could be the difference in penetration of mTHPC into the spheroids as well as their heterogeneous structure.
Testing of efficacy of photodynamic therapy with a new photosensitizer - a of chlorin e6 derivative (BLC 1010)
Authors: Stranadko E. Ph. , Riabov M.V. , N.VoIkova N. , Spaniol S. , Rauschning W. , Nifantiev N.E.
Published: February 2023

Efficacy of PDT with new chlorin e6 photosensitizer (BLC 1010) has been tested in 72 cancer patients. 44 patients (61 %) achieved a complete response and 39 % of the patients a partial response (28 patients, including 15 patients treated for palliation).

Rapid elimination of BLC 1010 from the organism solves the problem of skin phototoxicity encountered in PDT up to now. This property together with its high tumor to normal ratio makes it a promising photosensitizer for PDT. Further advantage is that portable diode lasers with proper wavelength are available.
Changes in transmission spectrum of human venous blood under action of low-intensity He-Ne laser or extracorporal UV irradiation
Authors: Minkovich V.P. , Starodumov A.N. , Marochkov A.V.
Published: February 2023

At present, foolproof methods are needed for control of low-power light biomedical effects. Transmission spectra of whole blood from 108 patients were recorded before and after action of low-intensity He-Ne laser and extracorporal UV irradiation. We have observed changes in the blood transmission spectrum caused by oxygen saturation changes in venous blood. It has shown that He-Ne laser irradiation more selectively acts to venous blood than extracorporal UV irradiation.
Low intensity lasers, modern tilling materials and bonding systems influence on mineral metabolism of hard dental tissues
Authors: Kunin A.A. , Yesaulenko I.E. , Zoibelmann M. , Pankova S.N. , Ippolitov Yu.A. , Oleinik O.I. , Popova T.A. , Koretskaya I.V. , Shumilovitch B.R. , Podolskaya E.E.
Published: February 2023

One of the main reasons of low quality filling is breaking Ca-P balance in hard tissues. Our research was done with the purpose of studying the influence of low intensity lasers, diodic radiation, the newest filling and bonding systems on the processes of mineral metabolism in hard dental tissues while filling a tooth. 250 patients having caries and its complications were examined and treated. Our complex research included: visual and instrumental examination, finding out the level of oral cavity hygiene, acid enamel biopsy, scanning electronic microscopy and X-ray spectrum microanalysis. Filling processes may produce a negative effect on mineral metabolism of hard dental tissues the latter is less pronounced when applying fluoride-containing filling materials with bonding systems. It has also been found that bonding dentin and enamel systems are designed for both a better filling adhesion (i.e. mechanical adhesion) and migration of useful microelements present in them by their sinking into hard dental tissues (i.e. chemical adhesion). Our research showed a positive influence of low intensity laser and diodic beams accompanying the use of modem filling and bonding systems on mineral metabolism of hard dental tissues.
Comparison of linear polarization degree in health and wounded rat skin
Authors: Ribeiro Martha S. , Freitas Anderson Z. , Silva Daniela F. T. , Zezell Denise M. , Pellegrini Cleusa M. R. , Costa Fabiano G. , Zorn Telma M. T.
Published: February 2023

Low-intensity laser therapy (LILT) with adequate wavelength, intensity, and dose can accelerate tissue repair. However, there is still disperse information about light characteristics. Several works indicate that laser polarization plays an important role on the wound healing process. This study was conducted to verify the degree of linear polarization in normal and pathological rat skin samples. Artificial burns about 6 mm in diameter were created with liquid N2 on the back of the animals. The degree of polarization was measured in normal and pathological skin samples. It was verified that linearly polarized light can survive in the superficial layers of skin and it can be more preserved in skin under pathological condition when compared with health skin. The present study supports the hypothesis that polarized laser radiation can be used to treat open wounds and improve the healing.
A neural network for photoplethysmographic respiratory rate monitoring
Authors: Johansson A.
Published: February 2023

The photoplethysmographic signal (PPG) includes respiratory components seen as frequency modulation of the heart rate (respiratory sinus arrhythmia, RSA), amplitude modulation of the cardiac pulse, and respiratory induced intensity variations (RIIV) in the PPG baseline. The aim of this study was to evaluate the accuracy of these components in determining respiratory rate, and to combine the components in a neural network for improved accuracy. The primary goal is to design a PPG ventilation monitoring system. PPG signals were recorded from 15 healthy subjects. From these signals, the systolic waveform, diastolic waveform, respiratory sinus arrhythmia, pulse amplitude and RIIV were extracted. By using simple algorithms, the rates of false positive and false negative detection of breaths were calculated for each of the five components in a separate analysis. Furthermore, a simple neural network (NN) was tried out in a combined pattern recognition approach. In the separate analysis, the error rates (sum of false positives and false negatives) ranged from 9.7% (pulse ampUtude) to 14.5% (systohc waveform). The corresponding value of the NN analysis was 9.5-9.6%.
Fourier interferometry with spectral fluorescence imaging for the study of mitochondrial distribution and function in living normal/malignant cells
Authors: Hirschberg Joseph G. , Kohen Elli , Kohen Cahide , Örnek Ceren , Berry John P.
Published: February 2023

The advantages of measuring both the excitation spectrum and emission spectrum of living cells’ fluorescence are reviewed together with interferometric methods. Mitochondria in yeast cells are described as examples of Biomedical methods, also including mammalian cells. Mitochondria in human hepatic cells, murine mast cells and human keratinocytes are shown using the vital stains DASPMI, Mitotracker Green and TMRE. An example in Biotechnology is the study of photosynthetic algae, used in the production of hydrogen.
Early events in plant hypersensitive response revealed by IR thermography
Authors: Boccara Martine , Boué Christine , De Paepe Rosine , Boccara Albert-Claude
Published: February 2023

Infrared thermography is used to reveal the establishment of Erwinia amylovora harpin-induced hypersensitive response (HR) in Nicotiana sylvestris leaves. We observed a decrease in temperature (1-2°C) in the harpin infiltrated zone, correlated with an increase in stomatal opening, strongly suggesting that the temperature decrease is due to higher transpiration rate. IRT experiments were conducted in a laboratory environment and could be widely applied for genotype screening and monitoring drug effects.
The use of dynamic speckle field space-time correlation function estimates for the direction and velocity determination of blood flow
Authors: Fedosov Ivan V. , Tuchin Valery V.
Published: February 2023

A method of flow direction and velocity determination using statistical properties of dynamic speckles is proposed. Two point detection of scattered light intensity fluctuations allows for slow flows velocity measuring and flow direction determination without incident beam frequency shifting and with using one focused incident beam. The space-time correlation functions estimated for two position of the incident beam waist allows for the flow space localization and the absolute flow velocity measuring. The described method has the principal advantages for the bioflow investigations in comparison of the traditional laser Doppler velocimetry.
Diagnostic applications of an opto-electronic device for high temporal resolution of erythrocytes sedimentation (ESR-graphy)
Authors: Voeikov Vladimir , Buravleva Ekaterina , Bulargina Yulia , Gurfinkel Yuri
Published: February 2023

An automatic device for high-temporal resolution of the process of erythrocytes sedimentation in blood was designed. The position of the boundary between red blood and plasma is registered each 30 sec in several pipettes simultaneously with ±10 mkm precision. Data are processed by a PC and presented as velocity-time curves (ESR-grams) and the curves describing time evolution of the boundary position. ESR-grams demonstrate non-monotonous character of erythrocytes sedimentation in blood. Blood of particular donor being in a stable physiological state taken on different days is characterized by similar ESR-grams. Pathological deviations from a normal physiological state are reflected in the shortening of duration of each process stage and increasing of average sedimentation rate. Intravenous infusion of some medical preparations may lead either to improving (prolonging of macrokinetic stages, decreasing of sedimentation rate), or to worsening of studied parameters depending on an individual. The low extent of blood dilution with saline in vitro lead as a rule to decreasing of sedimentation rate and improving of microkinetic parameters of the process. Adding of highly diluted hydrogen peroxide to blood samples of patients resulted in the improving of sedimentation kinetics. ESR-graphy may widen opportunities of practical medicine in diagnostics, prognostics and drug therapy.
Critical Illumination Condenser for EUV Projection Lithography
Authors: Cohen Simon J. , Seppala Lynn G.
Published: February 2023

A condenser system couples a radiation source to an imaging system. We have designed a critical illumination condenser system which meets the technical challenges of extreme ultraviolet projection lithography based on a ring field imaging system and a laser produced plasma source. The optical system, a three spherical mirror optical design, is capable of illuminating the extent of the mask plane by scanning either the primary mirror or the laser plasma source. This type of condenser optical design is sufficiently versatile to be employed with two distinct systems, one from Lawrence Livermore National Laboratory and one from AT&T/Sandia.
Simulation of Non-uniformities in Sources and Optics in Projection Printing
Authors: Lee Derek C. , Neureuther Andrew R.
Published: February 2023

The aerial image simulation program SPLAT has been generalized to explore the effects of multi­element source designs and possible problems from residual mirror reflectivity variations versus pupil position on image quality in projection x-ray lithography. To model wavefront attenuation, an optical transmission with apopdization (OTA) factor is introduced, which modifies the magnitude of the pupil function versus ray angle. The OTA is expanded in a Taylor series in polar coordinates. A radial OTA variation of 1- 0.25ρ2 which falls from 1.0 at the center of the lens to 0.75 at the lens edge, required small features to be oversized approximately by 8% to obtain the same image quality. To allow for irregularly shaped sources with non-uniform intensities, the source is represented over a square grid composed of many pixels. The source is defined using geometric primitives that can be assigned arbitrary intensity weights. Typical multiple element sources of the type proposed for EUV projection printing shows that the orientation of the feature with respect to the source has about a 5% effect. The generalization of the source non-uniformity modeling in SPLAT is also applicable to illumination studies in optical projection printing.
Experiments and Simulations of EUV Lithographic Resist Patterning at Wavelengths from 7 to 40 nm
Authors: Wood O. R. , Bjorkholm J. E. , Dreyer K. F. , Fetter L. , Himel M. D. , Freeman R. R. , Tennant D. M. , Griffith J. E. , Taylor G. N. , Waskiewicz W. K. , White D. L. , Windt D. L. , MacDowell A.A. , La Fontaine B. , Lum B. M. , R. A. , Neureuther  , Kortright J. B. , Gullikson E. M. , Nguyen K. B.
Published: February 2023

Both experiment and simulation of EUV lithographic resist patterning show that high resist absorption in the 7 to 40 nm wavelength region leads to unsatisfactory sidewall profiles in single-layer resists except at the shortest wavelengths.
Four-Mirror Ring-Field System for EUV Projection Lithography
Authors: Jewell Tanya E.
Published: February 2023

A four-mirror 4x reduction ring-field system for EUV projection lithography at 13.0 nm wavelength is described.
Defects in Coatings Deposited by Planar Magnetron Sputtering: Measurements with a Tencor Surfscan 6200
Authors: Nguyen Khanh B. , Resnick Paul , Draper Bruce , Mahl Paul , Underwood James H. , Chen Daniel , Denham Paul
Published: February 2023

Defect densities in coatings deposited by planar magnetron sputtering were measured with a Tencor
Surfscan 6200 laser particle detector. The measurements were performed on two sets of coatings - one
deposited in a research chamber at the Center for X-ray Optics (CXRO) at Lawrence Berkeley
Laboratories, the other deposited in a MTI Sypherline used for metal deposition in a class 1
cleanroom at the Microelectronics Development Laboratory (MDL) at Sandia National Laboratories.

For coatings deposited in the research chamber, as much as 90% of the defects counted were
particulates deposited during venting of the chamber. As a result, these defects were located on the
surface of the coatings and were removable by ultrasonic clean in de-ionized water. Of the remaining
defects on these coatings, as much as 75% of them were generated from inside the chamber during the
coating process. The average number of defects in 30 bilayers of Mo/Si was 20 cm-2 for
defects of sizes ≥ 0.5 µm latex-sphere-equivalent (LSE) diameter.

For coatings deposited in a clean chamber located in a class 1 cleanroom, the density of ≥ 0.5 µm LSE
diameter defects in a 1000 Å thick Si film was 0.2 cm-2. This is two orders of magnitude
fewer defects compared with coatings deposited in a research chamber. For ≥ 0.14 µm LSE diameter
defects, defect density was 7 cm-2. Defect density also increased with increased film
thickness.
Experience in EUV Photoemission with Multilayer Coated Optics
Authors: Cerrina Franco
Published: February 2023

Photoemission spectroscopy (PES) is a well -established experimental technique for the study of solids and surfaces. The essence of a PES experiment is to shine monochromatic radiation onto a sample and to measure the energy distribution of the photoemitted electrons. It provides a direct method for the determination of the filled electronic energy levels in a solid. The electron energy spectrum, the so-called energy distribution curve (EDC), contains features that can be associated with both the core levels and the valence-band density of states of the sample.
High Average Power Laser for EUV Lithography
Authors: Kania D. R. , Gaines D. P. , Hermann M. , Honig J. , Hostetler R. , Levesque R. , Sommargren G. E. , Spitzer R. C. , Vernon S. P.
Published: February 2023

We have demonstrated the operation of a high average power, all solid state laser and target system for EUV lithography. The laser operates at 1.06 µm with a pulse repetition rate of 200 Hz. Each pulse contains up to 400 mJ of energy and is less than 10 ns in duration. The EUV conversion efficiency measured with the laser is independent of the laser repetition rate. Operating at 200 Hz, the laser has been used for lithography using a 3 bounce Kohler illuminator.
Cryogenic Pellet Laser Plasma Source Targets
Authors: Kubiak Glenn D. , Krenz Kevin D. , Berger Kurt W. , Trucano Timothy G. , Fisher Paul W. , Gouge Michael J.
Published: February 2023

We have developed a new laser plasma cryogenic target scheme that achieves high conversion efficiency (CE), but produces no condensable target debris and low vaporized target gas loads. This scheme employs a solidified pellet of a rare gas, such as Xe, which is irradiated in free flight by a focused drive laser. The pellet is made small enough that gas loads produced following target vaporization are manageable, but large enough to fully intercept the laser energy at its focus. To assess the fundamental utility of cryogenic pellet targets, we have examined the conversion efficiency, extreme ultraviolet (EUV) spectroscopy, and fragmentation dynamics of Xe pellets irradiated with a 248 nm KrF laser.
Fabrication of MOS devices with extreme ultraviolet lithography
Authors: Nguyen K. B. , Cardinale G. F. , Tichenor D. A. , Kubiak G. D. , Berger K. , Ray-Chaudhuri A. K. , Perras Y. , Haney S. J. , Nissen R. , Krenz K. , Stulen R. H. , Fujioka H. , Hu C. , Bokor J. , Tennant D. M. , Fetter L. A.
Published: February 2023

This paper reports the first demonstration of MOS device fabrication using extreme ultraviolet lithography. The alignment strategy, mask layout, mask fabrication, and device characteristics will be reported.
Phase correcting layers in EUV imaging systems for microlithography
Authors: Braat Joseph
Published: February 2023

The requirements on the shape accuracy of reflecting surfaces in a projection system for EUV (extreme UV) microlithography are very severe. We propose the use of thin correcting layers with a strongly reduced optical contrast in the wavelength region of interest. These thin layers can be applied with relatively large tolerances to tune the reflecting mirror surface to its required shape. The application of such phase-correcting layers is useful too when defects on the reflecting reticle (mask) need to be repaired.
Extreme Ultraviolet 1:1 Ring-Field Lithography Machine
Authors: MacDowell A.A. , Shen Z. , Fujii K. , Bjorkholm J.E. , Freeman R.R. , Fetter L. , Taylor D.W. , Tennant D.M. , Eichner L. , Waskiewicz W.K. , White D.L. , Windt D.L. , Wood O.R. , Haney S. , Jewell T.
Published: February 2023

A 1X Offner Ring Field Extreme Ultraviolet lithography machine has been fabricated for use with 13.4nm radiation. Initial imaging results printed 75nm features but with low modulation. This initial work indicates that the optics suffer from a range of problems that we are trying to identify. These problems are typical of what a realistic EUV lithography machine will face.
Measuring the Effect of Scatter on the Performance of a Lithography System
Authors: La Fontaine B. , Daly T. P. , Chapman H. N. , Gaines D. P. , Stearns D. G. , Sweeney D. W. , Kania D. R.
Published: February 2023

The distribution of scattered light at the image plane of an extreme ultraviolet lithography (EUVL) system was measured, in situ. These measurements revealed a significant degradation of the modulation transfer function of the imaging optic, relative to its value in the absence of scattering.
Progress on an X-ray laser source at 135 A
Authors: McGeoch Malcolm
Published: February 2023

A repetitively pulsed fast plasma pinch has been used to generate strong emission on a number of transitions in highly ionized carbon, nitrogen, oxygen and neon, at a range of wavelengths between 95 and 350 Angstroms. The transitions are all fed by recombination during the expansion phase of the pinch. A typical starting geometry for the pinch is a helium-filled cylinder of diameter 2.5 cm and length 4 - 8 cm, containing approx 4 % propane, at a total pressure of 1 torr. The outside surface of the pinch cylinder is preionized using RF power before a longitudinal current of 200kA is initiated. The pinch reaches maximum compression and temperature after 150 nsec. The plasma column reaches a diameter of less than 400 microns. Its energy is 150 J and its temperature is estimated to be >100eV. Spectral lines are recorded axially on a 0.5 meter grazing incidence spectrometer. The strongest observed recombination line is from C V (1s2p - ls5d) at 175.67 Angstroms. It has a time-integrated intensity up to 11 times that of the helium II resonance line at 303.78 Angstroms. The latter line is radiatively trapped, representing the maximum brightness that the source can emit other than by the recombination mechanism. Other very strong lines include C VI (2p - 4d) at 134.99 Angstroms, of interest for EUV lithography. The identity of the strong spectral lines, their narrow width and their intensity are indicative of X-ray amplification. Preliminary length scaling shows an increase in intensity of 4x when the pinch length is doubled, from 4 cm to 8 cm.
Basic Technologies for Extreme Ultraviolet Lithography
Authors: Murakami Katsuhiko , Oshino Tetsuya , Shimizu Sumito , Wasa Wakana , Kondo Hiroyuki , Ohtani Masayuki , Kandaka Noriaki , Mashima Kiyoto , Nomura Kazushi
Published: February 2023

Research activities on the development of basic technologies for EUVL at Nikon, which include debris elimination of a laser plasma x-ray source, 3-mirror ring-field projection optics design, ring-field Köhler-critical illumination system design, asphere fabrication by partially corrective polishing, and electroplated reflection masks, are described.
Aspheric Surface Generation Requirements for Magnetorheological Finishing
Authors: Golini Don , Jacobs Steve , Zhou Yiyang , Fess Ed , Atwood Mark
Published: February 2023

A manufacturing system for grinding and polishing aspheres is under development at the Center for Optics Manufacturing (COM). Polishing is accomplished using the magnetorheological finishing (MRF) technique. MRF utilizes the unique properties of MR fluids to achieve high polishing removal rates. The fluid is carried through a magnetic field, in which its viscosity is increased by several orders of magnitude. The lens is polished in this viscous zone to optical quality. MRF is very effective at polishing high spatial frequency errors (microroughness) and at figuring global form errors (e.g. power), but has limitations for smoothing of mid-frequency errors. The work presented here will describe the problematic mid-spatial frequency regime, and use this a criteria for the aspheric grinding process.
Laser Enhanced Auto-Ionization and Dressed Resonances*
Authors: Eberly J.H. , Agassi D.
Published: February 2023

We describe the strong field dressing of atomic resonance states, and apply the dressed state description to the photo-excitation of an auto-ionizing resonance, including the effects of radiative and purely transverse line broadenings.
State to State Photochemistry of Glyoxal Using a Tunable VUV Laser For Product Detection
Authors: Hepburn John W. , Sivakumar N. , Houston Paul L.
Published: February 2023

In recent years there has been much interest in how the initial state of a reactant affects the products in a chemical process. In order to answer this question, systems are needed which permit state-selective preparation of the reactants and state-selective detection of the products. One of the few systems in which state-to-state processes have been studied is molecular predissociation, due to the structured absorption spectrum of the excited state, which is coupled to unimolecular dissociation channels. This paper will discuss recent progress in studying the state-to-state dynamics of glyoxal (CHO-CHO) predissociation.
Multiphoton Ionization of Benzene in Solution*
Authors: Siomos K. , Faidas H. , Christophorou L. G.
Published: February 2023

Two-photon absorption and excitation spectra of benzene in liquid and rigid solutions have been frequently reported.1 However, multiphoton ionization studies of benzene in liquid solution are limited and restricted to laser excitation wavelengths λexc ≲ 420 nm, which correspond to two-photon excitation energies hvexc ≳ 6 eV. Using a laser conductivity technique suitable for liquid-phase ionization investigations,2,3 we studied the multiphoton ionization spectrum of 10-3 mole dm-3 solutions of benzene in liquid n-pentane for hvexc ≲ 6 eV. We observed for the first time that the structure in the photocurrent versus hvexc (see Fig. 1) spectrum reflects the linearly polarized spectrum of the B2u-A1g transitions of benzene. Although we have not yet been able (due to the low intensity of our laser) to determine the order of the multiphoton ionization process, the spectrum in Fig. 1 is tentatively ascribed to a two-photon resonant three-photon ionization process. This spectrum is in excellent agreement with the two-photon excitation spectra reported by Friedrich et al.4
81Kr Detection Using Resonance Ionization Spectroscopy
Authors: Chen C. H. , Kramer S. D. , Allman S. L. , Hurst G. S.
Published: February 2023

The technique of resonance ionization spectroscopy (RIS) was extended to develop a means for counting individual atoms of a selected isotope of a noble gas. The experimental schematic is shown in Fig. 1. The concept for counting noble gas atoms with isotopic selectivity utilizes a laser for ionizing atoms of a selected atomic number (Z) and a mass spectrometer for atomic mass (A) selection. After atoms have been selectively ionized and mass selected, the ions are accelerated to 10 kV onto a Be-Cu target where they are implanted. The target will emit a pulse of several electrons which are detected by an electron multiplier. A four-wave mixing scheme was used to generate a 1165 Å beam with energy of 500 nJ/pulse. Thus, krypton atoms could be efficiently excited by resonant radiation and subsequently ionized. The use of a one-photon excitation step rather than a two-photon step also reduces the off-resonant multiphoton ionization background. An atom buncher was developed to enhance the probability that krypton atoms will be in the ionization laser beam at the time of the laser pulse, enabling a sample of 81Kr atoms to be counted in about 1 hr. Experimental data for counting 1000 atoms of 81Kr are shown in Fig. 2. The detection limit is believed to be less than 300 atoms of 81Kr.
Vacuum Ultraviolet Photoionization of Cold Molecular Beams: Single and Multiphoton Ionization and Photoelectron Spectroscopy
Authors: Miller John C. , Compton R. N.
Published: February 2023

A versatile apparatus for the study of vacuum ultraviolet (VUV) spectroscopy and photoionization of molecules has been developed. A pulsed, supersonic molecular beam is crossed with the focused beam of a pulsed dye laser or its doubled or tripled output. Ions are created by multiphoton ionization (MPI) with the fundamental beam (three to five photons), two-photon ionization using the doubled or tripled beam, or one-photon ionization with VUV. Use of a second laser for two-color experiments is also possible.
An XUV/VUV Free-Electron Laser Oscillator*
Authors: Goldstein John C. , Newnam Brian E. , Cooper Richard K. , Fraser John S.
Published: February 2023

A free-electron laser (FEL) oscillator driven by an rf linear accelerator (linac) appears feasible for the extreme- and vacuum-ultraviolet wavelength spectrum from 50 to 200 nm. The design of such a system is projected from the anticipated successful use of rf linacs at high peak currents (~100 A) in forthcoming FEL oscillator experiments at infrared and visible wavelengths by Los Alamos and Boeing/Mathematical Sciences Northwest. An important feature of the linac approach is that electrons pass through the undulator magnet only once, but their energy may be recovered in a separate decelerating structure and fed back into the primary accelerator. Another advantage is the option of unrestricted undulator length. The short pulse duration (10–40 ps) of the laser emission will find application in time-resolved experiments.
Extreme Ultraviolet and X-ray Emission and Amplification by Non-relativistic Electron Beams Traversing a Superlattice
Authors: Kaplan A. E. , Datta S.
Published: February 2023

Fast moving electrons emit FM waves when passing through a spatially periodic medium (resonant transition radiation). The wavelength λ of the radiation emitted at an angle θ with respect to the electron trajectory is determined by the formula

n
¯

(
λ
)

cos
θ
=

β

−
1

−
r
λ
/
ℓ

, where β = v/c is dimensionless speed at the electron,

n
¯

(
λ
)

is averaged refractive index of the system, r is an integer, and ℓ is the period of spatial modulation. It is conventionally assumed that ultra-relativistic beams are required to attain this kind of emission. We show that if the period ℓ is much shorter than a “mean” plasma wavelength of the medium, (which can be done by using solid-state superlattices with the spatial period 100–200Å), the critical kinetic energy turns out to be extremely low, and one can get a significant radiation in the range 10Å–300Å using non-relativistic beams with energies 70–300 KeV. The spontaneous radiation from the system has a conical structure with the emission wavelength changing with angle.
Mirrors for the Extreme Ultraviolet
Authors: Spiller Eberhard
Published: February 2023

High reflectivity normal incidence mirrors do not exist for wavelength λ < 1100 Å. There are no absorption-free dielectrics available which can protect a mirror from oxidation or can be incorporated into a loss-free multilayer. Furthermore the reflectivity of all materials decreases with decreasing wavelength to values around 1% at λ = 200 Å for the best materials. The reflectivity drops proportional to λ4 at still shorter wavelength with values less than 10−5 at λ = 50 Å. However, the loss in reflectivity from a single boundary can be compensated by using multilayer structure with many boundaries. Due to the absorption of all materials the coating designs differ from those used for visible light. Peak reflectivities of 20% or more can be obtained at nearly all wavelengths. The theoretically possible peak reflectivity increases with decreasing wavelengths and reaches very high values (R > 80%) around λ = 1 Å. Fabrication of normal incidence multilayer mirrors has concentrated on the wavelength region from λ = 50 - 250Å and peak reflectivities around R ≈ 25% have been obtained. The obtained results will be reviewed and the expected performance for other wavelengths will be discussed.
Direct Measurement of a Vacuum Ultraviolet Transition Oscillator Strength in Xenon
Authors: Kramer S. D. , Chen C. H. , Payne M. G. , Hurst G. S.
Published: February 2023

The oscillator strength, f, of the xenon 7s[3/2]1 state was directly measured by determining the phase matching condition for four-wave sum mixing in xenon-argon gas mixtures. The vacuum ultraviolet (VUV) mixing scheme for xenon is shown in Fig. 1.1 Optical mixing with a pair of pulsed dye lasers was used to produce the six-nsec long input beams at 252 and 1507 ma. The generated VUV output near 116.5 nm was tuned by varying the 1507 nm input. The VUV pulse energies of up to 1 μJ were measured using a separate nitric oxide ionization chamber.