Infrared wire-grid polarizer with sol-gel zirconia grating

NASA Astrophysics Data System (ADS)

Yamada, Itsunari; Ishihara, Yoshiro

2017-05-01

The infrared wire-grid polarizer consisting of an Al grating, Si, and sol-gel derived zirconia grating film was fabricated by soft imprint process and Al shadow coating processes. A silicone mold was used because of its low surface energy, flexibility, and capability of transferring submicrosized patterns. As a result, the Al grating with a pitch of 400 nm and a depth of 100 nm was obtained on the zirconia grating film. The fabricated polarizer exhibited a polarization function with the TM transmittance greater than that of the Si substrate in the specific wavelength range of 3.6-8.5 μm, because the zirconia film acted as an antireflection film. The maximum value was 63% at a wavelength of 5.2 μm. This increment of the TM transmission spectrum results in interference within the zirconia film. Also, the extinction ratio exceeded almost 20 dB in the 3-8.8 μm wavelength range.

Two-dimensional designed fabrication of subwavelength grating HCG mirror on silicon-on-insulator

NASA Astrophysics Data System (ADS)

Huang, Shen-Che; Hong, Kuo-Bin; Lu, Tien-Chang; He, Sailing

2016-03-01

We designed and fabricated a two dimensional high contrast subwavelength grating (HCG) mirrors. The computer-aided software was employed to verify the structural parameters including grating periods and filling factors. From the optimized simulation results, the designed HCG structure has a wide reflection stopband (reflectivity (R) >90%) of over 200 nm, which centered at telecommunication wavelength. The optimized HCG mirrors were fabricated by electron beam lithography and inductively coupled plasma process technique. The experimental result was almost consistent with calculated data. This achievement should have an impact on numerous photonic devices helpful attribution to the integrated HCG VCSELs in the future.

LCD real-time mask technique for fabrication of arbitrarily shaped microstructure

NASA Astrophysics Data System (ADS)

Peng, Qinjun; Guo, Yongkang; Chen, Bo; Du, Jinglei; Xiang, Jinshan; Cui, Zheng

2002-04-01

A new technique to fabricate arbitrarily shaped microstructures by using LCD (liquid crystal display) real- time mask is reported in this paper. Its principle and design method are explained. Based on partial coherent imaging theory, the process to fabricate micro-axicon array and zigzag grating has been simulated. The experiment using a color LCD as real-time mask has been set up. Micro-axicon array and zigzag grating has been fabricated by the LCD real-time mask technique. The 3D surface relief structures were made on pan chromatic silver-halide sensitized gelatin (Kodak-131) with trypsinase etching. The pitch size of zigzag grating is 46.26micrometers . The caliber of axicon is 118.7micrometers , and the etching depth is 1.332micrometers .

Surface morphology of refractive-index waveguide gratings fabricated in polymer films

NASA Astrophysics Data System (ADS)

Dong, Yi; Song, Yan-fang; Ma, Lei; Gao, Fang-fang

2016-09-01

The characteristic modifications are reported on the surface of polymeric waveguide film in the process of volume- grating fabrication. The light from a mode-locked 76 MHz femtosecond laser with pulse duration of 200 fs and wavelength of 800 nm is focused normal to the surface of the sample. The surface morphology modifications are ascribed to a fact that surface swelling occurs during the process. Periodic micro-structure is inscribed with increasing incident power. The laser-induced swelling threshold on the grating, which is higher than that of two-photon initiated photo-polymerization (TPIP) (8 mW), is verified to be about 20 mW. It is feasible to enhance the surface smoothness of integrated optics devices for further encapsulation. The variation of modulation depth is studied for different values of incident power and scan spacing. Ablation accompanied with surface swelling appears when the power is higher. By optimizing the laser carving parameters, highly efficient grating devices can be fabricated.

Trapezoidal diffraction grating beam splitters in single crystal diamond

NASA Astrophysics Data System (ADS)

Kiss, Marcell; Graziosi, Teodoro; Quack, Niels

2018-02-01

Single Crystal Diamond has been recognized as a prime material for optical components in high power applications due to low absorption and high thermal conductivity. However, diamond microstructuring remains challenging. Here, we report on the fabrication and characterization of optical diffraction gratings exhibiting a symmetric trapezoidal profile etched into a single crystal diamond substrate. The optimized grating geometry diffracts the transmitted optical power into precisely defined proportions, performing as an effective beam splitter. We fabricate our gratings in commercially available single crystal CVD diamond plates (2.6mm x 2.6mm x 0.3mm). Using a sputter deposited hard mask and patterning by contact lithography, the diamond is etched in an inductively coupled oxygen plasma with zero platen power. The etch process effectively reveals the characteristic {111} diamond crystal planes, creating a precisely defined angled (54.7°) profile. SEM and AFM measurements of the fabricated gratings evidence the trapezoidal shape with a pitch of 3.82μm, depth of 170 nm and duty cycle of 35.5%. Optical characterization is performed in transmission using a 650nm laser source perpendicular to the sample. The recorded transmitted optical power as function of detector rotation angle shows a distribution of 21.1% in the 0th order and 23.6% in each +/-1st order (16.1% reflected, 16.6% in higher orders). To our knowledge, this is the first demonstration of diffraction gratings with trapezoidal profile in single crystal diamond. The fabrication process will enable beam splitter gratings of custom defined optical power distribution profiles, while antireflection coatings can increase the efficiency.

Sensitivity analysis and optimization method for the fabrication of one-dimensional beam-splitting phase gratings

PubMed Central

Pacheco, Shaun; Brand, Jonathan F.; Zaverton, Melissa; Milster, Tom; Liang, Rongguang

2015-01-01

A method to design one-dimensional beam-spitting phase gratings with low sensitivity to fabrication errors is described. The method optimizes the phase function of a grating by minimizing the integrated variance of the energy of each output beam over a range of fabrication errors. Numerical results for three 1x9 beam splitting phase gratings are given. Two optimized gratings with low sensitivity to fabrication errors were compared with a grating designed for optimal efficiency. These three gratings were fabricated using gray-scale photolithography. The standard deviation of the 9 outgoing beam energies in the optimized gratings were 2.3 and 3.4 times lower than the optimal efficiency grating. PMID:25969268

Fabrication and performance of efficient thin circular polarization gratings with Bragg properties using bulk photo-alignment of a liquid crystalline polymer

NASA Astrophysics Data System (ADS)

Sakhno, Oksana; Gritsai, Yuri; Sahm, Hagen; Stumpe, Joachim

2018-03-01

Thin circular polarization gratings, characterized by high diffraction efficiency and large, up to 42°, diffraction angles were created by polarization holography for the first time. The high efficiency of the gratings is the result of the specific properties of a photo-crosslinkable liquid crystalline polymer and a two-step photochemical/thermal processing procedure. A diffraction efficiency of up to 98% at 532 nm has been achieved for gratings with periods of 700 nm. In contrast to polarization gratings with larger periods these gratings exhibit Bragg properties. So one beam is either transmitted or diffracted depending on the direction of the circular polarization of the incident light, whereas the maximal diffraction efficiency is achieved only at the proper incident angle. The fabrication procedure consists of holographic exposure of the film at room temperature which provides the photo-selective cycloaddition of cinnamic ester groups. Upon subsequent thermal annealing above T g bulk photo-alignment of the LC polymer film occurs enhancing the optical anisotropy within the grating. The holographic patterning provides high spatial resolution, the arbitrary orientation of the LC director as well as high optical quality, thermal and chemical stability of the final gratings. Highly efficient symmetric and slanted circular polarization gratings were fabricated with the proposed technique.

Fabrication and testing of freestanding Si nanogratings for UV filtration on space-based particle sensors.

PubMed

Mukherjee, Pran; Zurbuchen, Thomas H; Guo, L Jay

2009-08-12

We demonstrate complete fabrication process integration and device performance of sturdy, self-supported transmission gratings in silicon. Gratings are patterned with nanoimprint lithography and aluminum liftoff on silicon-on-insulator wafers. Double-sided deep reactive ion etching (DRIE) creates freestanding 120 nm half-pitch gratings with 2000 nm depth and built-in 1 mm pitch bulk silicon support structures. Optical characterization demonstrates 10(-4) transmission of UV in the 190-250 nm band while a 25-30% geometric transparency allows particles to pass unimpeded for space plasma measurements.

Fabrication of micron and submicron gratings by using plasma treatment on the curved polydimethylsiloxane surfaces

NASA Astrophysics Data System (ADS)

Yang, Jiangtao; Tang, Jun; Guo, Hao; Liu, Wenyao; Shen, Chong; Liu, Jun; Qin, Li

2017-10-01

Here, a simple and low-cost fabrication strategy to efficiently construct well-ordered micron and submicron gratings on polymeric substrates by oxygen plasma treatment is reported. The Polydimethylsiloxane (PDMS) substrate is prepared on the polyethylene (PET) by spin-coating method, then the curved PDMS-PET substrates are processed in oxygen plasma. After appropriate surface treatment time in plasma the curved substrates are flattened, and well-ordered wrinkling shape gratings are obtained, due to the mechanical buckling instability. It is also demonstrated that changing the curvature radius of PDMS-PET substrates and the time of plasma treatment, the period of the wrinkling patterns and the amplitude of grating also change accordingly. It is found the period of the wrinkling patterns increased with the radius of curvature; while the amplitude decreased with that. It also shows good optical performance in transmittance diffraction testing experiments. Thus the well-ordered grating approach may further develop portable and economical applications and offer a valuable method to fabricate other optical micro strain gauges devices.

Waveguide silicon nitride grating coupler

NASA Astrophysics Data System (ADS)

Litvik, Jan; Dolnak, Ivan; Dado, Milan

2016-12-01

Grating couplers are one of the most used elements for coupling of light between optical fibers and photonic integrated components. Silicon-on-insulator platform provides strong confinement of light and allows high integration. In this work, using simulations we have designed a broadband silicon nitride surface grating coupler. The Fourier-eigenmode expansion and finite difference time domain methods are utilized in design optimization of grating coupler structure. The fully, single etch step grating coupler is based on a standard silicon-on-insulator wafer with 0.55 μm waveguide Si3N4 layer. The optimized structure at 1550 nm wavelength yields a peak coupling efficiency -2.6635 dB (54.16%) with a 1-dB bandwidth up to 80 nm. It is promising way for low-cost fabrication using complementary metal-oxide- semiconductor fabrication process.

Fabrication of locally micro-structured fiber Bragg gratings by fs-laser machining

NASA Astrophysics Data System (ADS)

Dutz, Franz J.; Stephan, Valentin; Marchi, Gabriele; Koch, Alexander W.; Roths, Johannes; Huber, Heinz P.

2018-06-01

Here, we describe a method for producing locally micro-structured fiber Bragg gratings (LMFGB) by fs-laser machining. This technique enables the precise and reproducible ablation of cladding material to create circumferential grooves inside the claddings of optical fibers. From initial ablation experiments we acquired optimized process parameters. The fabricated grooves were located in the middle of uniform type I fiber Bragg gratings. LMFBGs with four different groove widths of 48, 85, 135 and 205 μ { {m}} were produced. The grooves exhibited constant depths of about 30 μ {m} and steep sidewall angles. With the combination of micro-structures and fiber Bragg gratings, fiber optic sensor elements with enhanced functionalities can be achieved.

Advanced Fibre Bragg Grating and Microfibre Bragg Grating Fabrication Techniques

NASA Astrophysics Data System (ADS)

Chung, Kit Man

Fibre Bragg gratings (FBGs) have become a very important technology for communication systems and fibre optic sensing. Typically, FBGs are less than 10-mm long and are fabricated using fused silica uniform phase masks which become more expensive for longer length or non-uniform pitch. Generally, interference UV laser beams are employed to make long or complex FBGs, and this technique introduces critical precision and control issues. In this work, we demonstrate an advanced FBG fabrication system that enables the writing of long and complex gratings in optical fibres with virtually any apodisation profile, local phase and Bragg wavelength using a novel optical design in which the incident angles of two UV beams onto an optical fibre can be adjusted simultaneously by moving just one optical component, instead of two optics employed in earlier configurations, to vary the grating pitch. The key advantage of the grating fabrication system is that complex gratings can be fabricated by controlling the linear movements of two translation stages. In addition to the study of advanced grating fabrication technique, we also focus on the inscription of FBGs written in optical fibres with a cladding diameter of several ten's of microns. Fabrication of microfibres was investigated using a sophisticated tapering method. We also proposed a simple but practical technique to filter out the higher order modes reflected from the FBG written in microfibres via a linear taper region while the fundamental mode re-couples to the core. By using this technique, reflection from the microfibre Bragg grating (MFBG) can be effectively single mode, simplifying the demultiplexing and demodulation processes. MFBG exhibits high sensitivity to contact force and an MFBG-based force sensor was also constructed and tested to investigate their suitability for use as an invasive surgery device. Performance of the contact force sensor packaged in a conforming elastomer material compares favourably to one of the best-performing commercial contact force sensors in catheterization applications. The proposed sensor features extremely high sensitivity up to 1.37-mN, miniature size (2.4-mm) that meets standard specification, excellent linearity, low hysteresis, and magnetic resonance imaging compatibility.

Curved VPH gratings for novel spectrographs

NASA Astrophysics Data System (ADS)

Clemens, J. Christopher; O'Donoghue, Darragh; Dunlap, Bart H.

2014-07-01

The introduction of volume phase holographic (VPH) gratings into astronomy over a decade ago opened new possibilities for instrument designers. In this paper we describe an extension of VPH grating technology that will have applications in astronomy and beyond: curved VPH gratings. These devices can disperse light while simultaneously correcting aberrations. We have designed and manufactured two different kinds of convex VPH grating prototypes for use in off-axis reflecting spectrographs. One type functions in transmission and the other in reflection, enabling Offnerstyle spectrographs with the high-efficiency and low-cost advantages of VPH gratings. We will discuss the design process and the tools required for modelling these gratings along with the recording layout and process steps required to fabricate them. We will present performance data for the first convex VPH grating produced for an astronomical spectrograph.

A novel method to fabricate silicon tubular gratings with broadband antireflection and super-hydrophobicity.

PubMed

Gao, Yang; Shi, Tielin; Tan, Xianhua; Liao, Guanglan

2014-06-01

We have developed a novel method to fabricate micro/nano structure based on the coherent diffraction lithography, and acquired periodic silicon tubular gratings with deep nano-scale tapered profiles at the top part. The optical properties of these tubular gratings were similar to an effective gradient-index antireflective surface, resulting in a broadband antireflective combining super-hydrophobic behavior. The mechanism of the method was simulated by rigorous coupled wave analysis algorithms. Then coherent diffraction lithography by use of suitable mask, in which periodic micro-scale circular opaque patters were distributed, was realized on the traditional aligner. Due to coherent diffraction, we obtained enough light intensity for photoresist exposure under the center of the opaque area in the mask together with transparent areas. The tapered line profiles and hollow photoresist gratings over large areas could be fabricated on the silicon wafer after development. The dry etching process was carried out, and high aspect ratio silicon tubular gratings with deep tapered profiles at the top were fabricated. The optical property and wettability of the structure were verified, proving that the proposed method and obtained micro/nano structure provide application potential in the future.

Fabrication update on critical-angle transmission gratings for soft x-ray grating spectrometers

NASA Astrophysics Data System (ADS)

Heilmann, Ralf K.; Bruccoleri, Alex; Mukherjee, Pran; Yam, Jonathan; Schattenburg, Mark L.

2011-09-01

Diffraction grating-based, wavelength dispersive high-resolution soft x-ray spectroscopy of celestial sources promises to reveal crucial data for the study of the Warm-Hot Intergalactic Medium, the Interstellar Medium, warm absorption and outflows in Active Galactic Nuclei, coronal emission from stars, and other areas of interest to the astrophysics community. Our recently developed critical-angle transmission (CAT) gratings combine the advantages of the Chandra high and medium energy transmission gratings (low mass, high tolerance of misalignments and figure errors, polarization insensitivity) with those of blazed reflection gratings (high broad band diffraction efficiency, high resolution through use of higher diffraction orders) such as the ones on XMM-Newton. Extensive instrument and system configuration studies have shown that a CAT grating-based spectrometer is an outstanding instrument capable of delivering resolving power on the order of 5,000 and high effective area, even with a telescope point-spread function on the order of many arc-seconds. We have fabricated freestanding, ultra-high aspect-ratio CAT grating bars from silicon-on-insulator wafers using both wet and dry etch processes. The 200 nm-period grating bars are supported by an integrated Level 1 support mesh, and a coarser external Level 2 support mesh. The resulting grating membrane is mounted to a frame, resulting in a grating facet. Many such facets comprise a grating array that provides light-weight coverage of large-area telescope apertures. Here we present fabrication results on the integration of CAT gratings and the different high-throughput support mesh levels and on membrane-frame bonding. We also summarize recent x-ray data analysis of 3 and 6 micron deep wet-etched CAT grating prototypes.

Core-to-core uniformity improvement in multi-core fiber Bragg gratings

NASA Astrophysics Data System (ADS)

Lindley, Emma; Min, Seong-Sik; Leon-Saval, Sergio; Cvetojevic, Nick; Jovanovic, Nemanja; Bland-Hawthorn, Joss; Lawrence, Jon; Gris-Sanchez, Itandehui; Birks, Tim; Haynes, Roger; Haynes, Dionne

2014-07-01

Multi-core fiber Bragg gratings (MCFBGs) will be a valuable tool not only in communications but also various astronomical, sensing and industry applications. In this paper we address some of the technical challenges of fabricating effective multi-core gratings by simulating improvements to the writing method. These methods allow a system designed for inscribing single-core fibers to cope with MCFBG fabrication with only minor, passive changes to the writing process. Using a capillary tube that was polished on one side, the field entering the fiber was flattened which improved the coverage and uniformity of all cores.

Properties of Chirped Grating Lenses in Optical Waveguides.

DTIC Science & Technology

1984-10-01

the design, the materials and the fabrication q process. In this report, we will summarize the research results obtained at UCSD on the fundamental...limitations of their performance in efficiency, angular field of view and F-number caused by diffraction, materials properties and fabrication techniques... material index, the grating groove pattern in both the transverse and the longitudinal direction and the profile of the grooves can all be varied, while in

Analysis of grating doublets for achromatic beam-splitting

PubMed Central

Pacheco, Shaun; Milster, Tom; Liang, Rongguang

2015-01-01

Achromatic beam-splitting grating doublets are designed for both continuous phase and binary phase gratings. By analyzing the sensitivity to lateral shifts between the two grating layers, it is shown that continuous-profile grating doublets are extremely difficult to fabricate. Achromatic grating doublets that have profiles with a constant first spatial derivative are significantly more resistant to lateral shifts between grating layers, where one design case showed a 17 times improvement in performance. Therefore, binary phase, multi-level phase, and blazed grating doublets perform significantly better than continuous phase grating doublets in the presence of a lateral shift between two grating layers. By studying the sensitivity to fabrication errors in the height of both grating layers, one grating layer height can be adjusted to maintain excellent performance over a large wavelength range if the other grating layer is fabricated incorrectly. It is shown in one design case that the performance of an achromatic Dammann grating doublet can be improved by a factor of 215 if the heights of the grating layers are chosen to minimize the performance change in the presence of fabrication errors. PMID:26368261

Double sided grating fabrication for high energy X-ray phase contrast imaging

DOE PAGES

Hollowell, Andrew E.; Arrington, Christian L.; Finnegan, Patrick; ...

2018-04-19

State of the art grating fabrication currently limits the maximum source energy that can be used in lab based x-ray phase contrast imaging (XPCI) systems. In order to move to higher source energies, and image high density materials or image through encapsulating barriers, new grating fabrication methods are needed. In this work we have analyzed a new modality for grating fabrication that involves precision alignment of etched gratings on both sides of a substrate, effectively doubling the thickness of the grating. Furthermore, we have achieved a front-to-backside feature alignment accuracy of 0.5 µm demonstrating a methodology that can be appliedmore » to any grating fabrication approach extending the attainable aspect ratios allowing higher energy lab based XPCI systems.« less

Double sided grating fabrication for high energy X-ray phase contrast imaging

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hollowell, Andrew E.; Arrington, Christian L.; Finnegan, Patrick

State of the art grating fabrication currently limits the maximum source energy that can be used in lab based x-ray phase contrast imaging (XPCI) systems. In order to move to higher source energies, and image high density materials or image through encapsulating barriers, new grating fabrication methods are needed. In this work we have analyzed a new modality for grating fabrication that involves precision alignment of etched gratings on both sides of a substrate, effectively doubling the thickness of the grating. Furthermore, we have achieved a front-to-backside feature alignment accuracy of 0.5 µm demonstrating a methodology that can be appliedmore » to any grating fabrication approach extending the attainable aspect ratios allowing higher energy lab based XPCI systems.« less

Fabrication of Polymer Optical Fibre (POF) Gratings

PubMed Central

Luo, Yanhua; Yan, Binbin; Zhang, Qijin; Peng, Gang-Ding; Wen, Jianxiang; Zhang, Jianzhong

2017-01-01

Gratings inscribed in polymer optical fibre (POF) have attracted remarkable interest for many potential applications due to their distinctive properties. This paper overviews the current state of fabrication of POF gratings since their first demonstration in 1999. In particular we summarize and discuss POF materials, POF photosensitivity, techniques and issues of fabricating POF gratings, as well as various types of POF gratings. PMID:28273844

A grating coupler with a trapezoidal hole array for perfectly vertical light coupling between optical fibers and waveguides

NASA Astrophysics Data System (ADS)

Mizutani, Akio; Eto, Yohei; Kikuta, Hisao

2017-12-01

A grating coupler with a trapezoidal hole array was designed and fabricated for perfectly vertical light coupling between a single-mode optical fiber and a silicon waveguide on a silicon-on-insulator (SOI) substrate. The grating coupler with an efficiency of 53% was computationally designed at a 1.1-µm-thick buried oxide (BOX) layer. The grating coupler and silicon waveguide were fabricated on the SOI substrate with a 3.0-µm-thick BOX layer by a single full-etch process. The measured coupling efficiency was 24% for TE-polarized light at 1528 nm wavelength, which was 0.69 times of the calculated coupling efficiency for the 3.0-µm-thick BOX layer.

Fabrication of precise aperiodic multichannel fibre Bragg grating filters for spectral line suppression in hydrogenated standard telecommunications fibre.

PubMed

Gbadebo, Adenowo A; Turitsyna, Elena G; Williams, John A R

2018-01-22

We demonstrate the design and fabrication of multichannel fibre Bragg gratings (FBGs) with aperiodic channel spacings. These will be suitable for the suppression of specific spectral lines such as OH emission lines in the near infrared (NIR) which degrade ground based astronomical imaging. We discuss the design process used to meet a given specification and the fabrication challenges that can give rise to errors in the final manufactured device. We propose and demonstrate solutions to meet these challenges.

Fabrication and characterization of one-dimensional multilayer gratings for nanoscale microscope calibration

NASA Astrophysics Data System (ADS)

Wang, Xingrui; Zhao, Yang; Liu, Jie; Chen, Jie; Li, Tongbao; Cheng, Xinbin

2016-09-01

One-dimensional multilayer gratings were prepared by four steps. A periodic Si/SiO2 multilayer was firstly deposited on Si substrate using a magnetron sputtering coating process. Then, the multilayer was been bonded and split into small pieces by diamond wire cutting. The side-wall of the cut sample was subsequently grinded and polished until the surface roughness was less than 1nm. Finally, the SiO2 layers were selective etched using hydrofluoric acid to form the grating structure. In the above steps, special attentions were given to optimize the etching processes to achieve a uniform and smooth grating pattern. Transmission electron microscope (TEM) was used to characterize the multilayer gratings. The pitch size of the grating was evaluated by an offline image analysis algorithm and optimized processes are discussed.

Birefringence Bragg Binary (3B) grating, quasi-Bragg grating and immersion gratings

NASA Astrophysics Data System (ADS)

Ebizuka, Noboru; Morita, Shin-ya; Yamagata, Yutaka; Sasaki, Minoru; Bianco, Andorea; Tanabe, Ayano; Hashimoto, Nobuyuki; Hirahara, Yasuhiro; Aoki, Wako

2014-07-01

A volume phase holographic (VPH) grating achieves high angular dispersion and very high diffraction efficiency for the first diffraction order and for S or P polarization. However the VPH grating could not achieve high diffraction efficiency for non-polarized light at a large diffraction angle because properties of diffraction efficiencies for S and P polarizations are different. Furthermore diffraction efficiency of the VPH grating extinguishes toward a higher diffraction order. A birefringence binary Bragg (3B) grating is a thick transmission grating with optically anisotropic material such as lithium niobate or liquid crystal. The 3B grating achieves diffraction efficiency up to 100% for non-polarized light by tuning of refractive indices for S and P polarizations, even in higher diffraction orders. We fabricated 3B grating with liquid crystal and evaluated the performance of the liquid crystal grating. A quasi-Bragg (QB) grating, which consists long rectangle mirrors aligned in parallel precisely such as a window shade, also achieves high diffraction efficiency toward higher orders. We fabricated QB grating by laminating of silica glass substrates and glued by pressure fusion of gold films. A quasi-Bragg immersion (QBI) grating has smooth mirror hypotenuse and reflector array inside the hypotenuse, instead of step-like grooves of a conventional immersion grating. An incident beam of the QBI grating reflects obliquely at a reflector, then reflects vertically at the mirror surface and reflects again at the same reflector. We are going to fabricate QBI gratings by laminating of mirror plates as similar to fabrication of the QB grating. We will also fabricate silicon and germanium immersion gratings with conventional step-like grooves by means of the latest diamond machining methods. We introduce characteristics and performance of these gratings.

Multi-wavelength VCSEL arrays using high-contrast gratings

NASA Astrophysics Data System (ADS)

Haglund, Erik; Gustavsson, Johan S.; Sorin, Wayne V.; Bengtsson, Jörgen; Fattal, David; Haglund, Àsa; Tan, Michael; Larsson, Anders

2017-02-01

The use of a high-contrast grating (HCG) as the top mirror in a vertical-cavity surface-emitting laser (VCSEL) allows for setting the resonance wavelength by the grating parameters in a post-epitaxial growth fabrication process. Using this technique, we demonstrate electrically driven multi-wavelength VCSEL arrays at 980 nm wavelength. The VCSELs are GaAs-based and the suspended GaAs HCGs were fabricated using electron-beam lithography, dry etching and selective removal of an InGaP sacrificial layer. The air-coupled cavity design enabled 4-channel arrays with 5 nm wavelength spacing and sub-mA threshold currents thanks to the high HCG reflectance.

Photoelectrochemical fabrication of spectroscopic diffraction gratings, phase 2

NASA Technical Reports Server (NTRS)

Rauh, R. David; Carrabba, Michael M.; Li, Jianguo; Cartland, Robert F.; Hachey, John P.; Mathew, Sam

1990-01-01

This program was directed toward the production of Echelle diffraction gratings by a light-driven, electrochemical etching technique (photoelectrochemical etching). Etching is carried out in single crystal materials, and the differential rate of etching of the different crystallographic planes used to define the groove profiles. Etching of V-groove profiles was first discovered by us during the first phase of this project, which was initially conceived as a general exploration of photoelectrochemical etching techniques for grating fabrication. This highly controllable V-groove etching process was considered to be of high significance for producing low pitch Echelles, and provided the basis for a more extensive Phase 2 investigation.

Conversion between EIT and Fano spectra in a microring-Bragg grating coupled-resonator system

NASA Astrophysics Data System (ADS)

Zhang, Zecen; Ng, Geok Ing; Hu, Ting; Qiu, Haodong; Guo, Xin; Wang, Wanjun; Rouifed, Mohamed Saïd; Liu, Chongyang; Wang, Hong

2017-08-01

A conversion between the electromagnetically induced transparency (EIT) transmission and Fano transmission is theoretically and experimentally demonstrated in an all-pass microring-Bragg grating (APMR-BG) coupled-resonator system. In this work, the coupling between the two resonators (the microring resonator and the Fabry-Perot resonator formed by two Bragg gratings) gives rise to the EIT and Fano transmissions. The resonant status strongly depends on the round-trip attenuation of the microring and the coupling strength. By tuning the coupling strength, the EIT and Fano transmissions can be controlled and converted. The device performance has been theoretically calculated and analyzed with a specially developed numerical model based on the transfer matrix method. The APMR-BG coupled-resonator systems with different gap widths were designed, fabricated, and characterized on a silicon-on-insulator (SOI) platform. The conversion of resonance was experimentally observed and verified. In addition, this on-chip system has the advantage of a small footprint, and the fabrication process is compatible with the planar waveguide fabrication process.

Design and fabrication of label-free biochip using a guided mode resonance filter with nano grating structures by injection molding process.

PubMed

Cho, E; Kim, B; Choi, S; Han, J; Jin, J; Han, J; Lim, J; Heo, Y; Kim, S; Sung, G Y; Kang, S

2011-01-01

This paper introduces technology to fabricate a guided mode resonance filter biochip using injection molding. Of the various nanofabrication processes that exist, injection molding is the most suitable for the mass production of polymer nanostructures. Fabrication of a nanograting pattern for guided mode resonance filters by injection molding requires a durable metal stamp, because of the high injection temperature and pressure. Careful consideration of the optimized process parameters is also required to achieve uniform sub-wavelength gratings with high fidelity. In this study, a metallic nanostructure pattern to be used as the stamp for the injection molding process was fabricated using electron beam lithography, a UV nanoimprinting process, and an electroforming process. A one-dimensional nanograting substrate was replicated by injection molding, during which the process parameters were controlled. To evaluate the geometric quality of the injection molded nanograting patterns, the surface profile of the fabricated nanograting for different processing conditions was analyzed using an atomic force microscope and a scanning electron microscope. Finally, to demonstrate the feasibility of the proposed process for fabricating guided mode resonance filter biochips, a high-refractive-index material was deposited on the polymer nanograting and its guided mode resonance characteristics were analyzed.

Fabrication and Characterization of Tilted Fiber Optic Bragg Grating Filters over Various Wavelengths

NASA Technical Reports Server (NTRS)

Grant, Joseph; Jackson, Kurt V.; Wang, Y.; Sharma, A.; Burdine, Robert V. (Technical Monitor)

2002-01-01

Fiber Optic Bragg Grating taps are fabricated and characterized at various wavelengths using a modified Talbot interferometric technique. Gratings are fabricated by tilting the photosensitive fiber to angles up to 45 degrees w.r.t. the writing angle. Diffraction characteristics of the tilted grating is monitored in first and second orders.

Fabrication and characterization of W/B4C lamellar multilayer grating and NbC/Si multilayer phase-shift reflector

NASA Astrophysics Data System (ADS)

Pradhan, P. C.; Bhartiya, S.; Singh, A.; Majhi, A.; Gome, A.; Dhawan, R.; Nayak, M.; Sahoo, P. K.; Rai, S. K.; Reddy, V. R.

2017-08-01

We present fabrication and structural analysis of two different multilayer grating structures. W/B4C based lamellar multilayer grating (LMG) was studied for high resolution monochomator application near soft x-ray region ( 1.5 keV). Whereas NbC/Si based multilayer phase-shift reflector (MPR) was studied for high reflection at normal incidence near Si L-edge ( 99 eV) and simultaneously to suppress the unwanted vacuum ultraviolet / infrared radiation. The grating patterns of different periods down to D = 10 micron were fabricated on Si substrates by using photolithography, and multilayers (MLs) of different periodicity (d = 10 to 2 nm) and number of layer pairs (15 to 100) were coated using sputtering techniques by optimizing the process parameters. The LMG and MPR samples are characterized by x-ray reflectivity (XRR) and atomic force microscopy (AFM) measurements. XRR results show successive higher order Bragg peaks that reveal a well-defined vertical periodic structure in LMG, MPR and ML structures. The lateral periodicity of the grating and depth of the rectangular groves were analyzed using AFM. The AFM results show good quality of lateral periodic structures in terms of groove profile. The effect of the process parameters on the microstructure (both on vertical and lateral patterns) of ML, LMG and MPR were analyzed.

Line spread functions of blazed off-plane gratings operated in the Littrow mounting

NASA Astrophysics Data System (ADS)

DeRoo, Casey T.; McEntaffer, Randall L.; Miles, Drew M.; Peterson, Thomas J.; Marlowe, Hannah; Tutt, James H.; Donovan, Benjamin D.; Menz, Benedikt; Burwitz, Vadim; Hartner, Gisela; Allured, Ryan; Smith, Randall K.; Günther, Ramses; Yanson, Alex; Vacanti, Giuseppe; Ackermann, Marcelo

2016-04-01

Future soft x-ray (10 to 50 Å) spectroscopy missions require higher effective areas and resolutions to perform critical science that cannot be done by instruments on current missions. An x-ray grating spectrometer employing off-plane reflection gratings would be capable of meeting these performance criteria. Off-plane gratings with blazed groove facets operating in the Littrow mounting can be used to achieve excellent throughput into orders achieving high resolutions. We have fabricated two off-plane gratings with blazed groove profiles via a technique that uses commonly available microfabrication processes, is easily scaled for mass production, and yields gratings customized for a given mission architecture. Both fabricated gratings were tested in the Littrow mounting at the Max Planck Institute for Extraterrestrial Physics (MPE) PANTER x-ray test facility to assess their performance. The line spread functions of diffracted orders were measured, and a maximum resolution of 800±20 is reported. In addition, we also observe evidence of a blaze effect from measurements of relative efficiencies of the diffracted orders.

Deformable silicone grating fabricated with a photo-imprinted polymer mold

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yamada, Itsunari, E-mail: yamada.i@e.usp.ac.jp; Nishii, Junji; Saito, Mitsunori

A tunable transmission grating was fabricated by molding a silicone elastomer (polydimethylsiloxane). Its optical characteristics were then evaluated during compression. For fabrication, a glass plate with a photoimprinted polymer grating film was used as a mold. Both the grating period and diffraction transmittance of the molded elastomer were functions of the compressive stress. The grating period changed from 3.02 to 2.86 μm during compressing the elastomer in the direction perpendicular to the grooves.

3D nanomolding and fluid mixing in micromixers with micro-patterned microchannel walls.

PubMed

Farshchian, Bahador; Amirsadeghi, Alborz; Choi, Junseo; Park, Daniel S; Kim, Namwon; Park, Sunggook

2017-01-01

Microfluidic devices where the microchannel walls were decorated with micro and nanostructures were fabricated using 3D nanomolding. Using 3D molded microfluidic devices with microchannel walls decorated with microscale gratings, the fluid mixing behavior was investigated through experiments and numerical simulation. The use of microscale gratings in the micromixer was predicated by the fact that large obstacles in a microchannel enhances the mixing performance. Slanted ratchet gratings on the channel walls resulted in a helical flow along the microchannel, thus increasing the interfacial area between fluids and cutting down the diffusion length. Increasing the number of walls decorated with continuous ratchet gratings intensified the strength of the helical flow, enhancing mixing further. When ratchet gratings on the surface of the top cover plate were aligned in a direction to break the continuity of gratings from the other three walls, a stack of two helical flows was formed one above each other. This work concludes that the 3D nanomolding process can be a cost-effective tool for scaling-up the fabrication of microfluidic mixers with improved mixing efficiencies.Graphical abstractIn this paper we show that a micromixer with patterned walls can be fabricated using 3D nanomolding and solvent-assisted bonding to manipulate the flow patterns to improve mixing.

An analysis of the surface-normal coupling efficiency of a metal grating coupler embedded in a Scotch tape optical waveguide

NASA Astrophysics Data System (ADS)

Barrios, Carlos Angulo; Canalejas-Tejero, Víctor

2017-01-01

The coupling efficiency at normal incidence of recently demonstrated aluminum grating couplers integrated in flexible Scotch tape waveguides has been analyzed theoretically and experimentally. Finite difference time domain (FDTD) and rigorously coupled wave analysis (RCWA) methods have been used to optimize the dimensions (duty cycle and metal thickness) of Scotch tape-embedded 1D Al gratings for maximum coupling at 635 nm wavelength. Good dimension and tape refractive index tolerances are predicted. FDTD simulations reveal the incident beam width and impinging position (alignment) values that avoid rediffraction and thus maximize the coupling efficiency. A 1D Al diffraction grating integrated into a Scotch tape optical waveguide has been fabricated and characterized. The fabrication process, based on pattern transfer, has been optimized to allow complete Al grating transfer onto the Scotch tape waveguide. A maximum coupling efficiency of 20% for TM-polarized normal incidence has been measured, which is in good agreement with the theoretical predictions. The measured coupling efficiency is further increased up to 28% for TM polarization under oblique incidence. Temperature dependence measurements have been also achieved and related to the simulations results and fabrication procedure.

An update on X-ray reflection gratings developed for future missions

NASA Astrophysics Data System (ADS)

Miles, Drew

2018-01-01

X-ray reflection gratings are a key technology being studied for future X-ray spectroscopy missions, including the Lynx X-ray mission under consideration for the 2020 Decadal Survey. We present an update on the status of X-ray reflection gratings being developed at Penn State University, including current fabrication techniques and mass-replication processes and the latest diffraction efficiency results and resolving power measurements. Individual off-plane X-ray reflection gratings have exceeded the current Lynx requirements for both effective area and resolving power. Finally, we discuss internal projects that will advance the technology readiness level of these gratings.

Application of Notched Long-Period Fiber Grating Based Sensor for CO2 Gas Sensing

NASA Astrophysics Data System (ADS)

Wu, Chao-Wei; Chiang, Chia-Chin

2016-01-01

An inductively coupled plasma etching process to fabricate notched long-period fiber gratings for CO2 gas sensing is proposed in this article. In the gas sensing test, the 15% mixed CO2 gas was used for characterization of CO2 adsorption by the amine-modified nanoporous silica foams of the notched long-period fiber grating sensor. The results shows the spectra were changed with the CO2 gas flow within 13 min. During the absorption process, the transmission of the resonant dip was decreased by 2.884 dB. Therefore, the proposed notched long-period fiber grating gas sensor shows good performance and is suitable as a gas sensor for monitoring the CO2 adsorption process.

3D nanomolding and fluid mixing in micromixers with micro-patterned microchannel walls

NASA Astrophysics Data System (ADS)

Farshchian, Bahador; Amirsadeghi, Alborz; Choi, Junseo; Park, Daniel S.; Kim, Namwon; Park, Sunggook

2017-03-01

Microfluidic devices where the microchannel walls were decorated with micro and nanostructures were fabricated using 3D nanomolding. Using 3D molded microfluidic devices with microchannel walls decorated with microscale gratings, the fluid mixing behavior was investigated through experiments and numerical simulation. The use of microscale gratings in the micromixer was predicated by the fact that large obstacles in a microchannel enhances the mixing performance. Slanted ratchet gratings on the channel walls resulted in a helical flow along the microchannel, thus increasing the interfacial area between fluids and cutting down the diffusion length. Increasing the number of walls decorated with continuous ratchet gratings intensified the strength of the helical flow, enhancing mixing further. When ratchet gratings on the surface of the top cover plate were aligned in a direction to break the continuity of gratings from the other three walls, a stack of two helical flows was formed one above each other. This work concludes that the 3D nanomolding process can be a cost-effective tool for scaling-up the fabrication of microfluidic mixers with improved mixing efficiencies.[Figure not available: see fulltext.

X-ray/VUV transmission gratings for astrophysical and laboratory applications

NASA Technical Reports Server (NTRS)

Schattenburg, M. L.; Anderson, E. H.; Smith, Henry I.

1990-01-01

This paper describes the techniques used to fabricate deep-submicron-period transmission gratings for astrophysical and laboratory applications, with special attention given to the major steps involved in the transmission grating fabrication. These include the holographic lithography procedure used to pattern the master transmission grating, the fabrication of X-ray mask, the X-ray lithography step used to transfer the X-ray mask pattern into a substrate, and the electroplating of the substrate to form the final grating pattern. The various ways in which transmission gratings can be used in X-ray and VUV spectroscopy are discussed together with some examples of experiments reported in the literature.

Corrugated grating on organic multilayer Bragg reflector

NASA Astrophysics Data System (ADS)

Jaquet, Sylvain; Scharf, Toralf; Herzig, Hans Peter

2007-08-01

Polymeric multilayer Bragg structures are combined with diffractive gratings to produce artificial visual color effects. A particular effect is expected due to the angular reflection dependence of the multilayer Bragg structure and the dispersion caused by the grating. The combined effects can also be used to design particular filter functions and various resonant structures. The multilayer Bragg structure is fabricated by spin-coating of two different low-cost polymer materials in solution on a cleaned glass substrate. These polymers have a refractive index difference of about 0.15 and permit multilayer coatings without interlayer problems. Master gratings of different periods are realized by laser beam interference and replicated gratings are superimposed on the multilayer structure by soft embossing in a UV curing glue. The fabrication process requires only polymer materials. The obtained devices are stable and robust. Angular dependent reflection spectrums for the visible are measured. These results show that it is possible to obtain unexpected reflection effects. A rich variety of color spectra can be generated, which is not possible with a single grating. This can be explained by the coupling of transmission of grating orders and the Bragg reflection band. A simple model permits to explain some of the spectral vs angular dependence of reflected light.

Polymer waveguide grating sensor integrated with a thin-film photodetector

PubMed Central

Song, Fuchuan; Xiao, Jing; Xie, Antonio Jou; Seo, Sang-Woo

2014-01-01

This paper presents a planar waveguide grating sensor integrated with a photodetector (PD) for on-chip optical sensing systems which are suitable for diagnostics in the field and in-situ measurements. III–V semiconductor-based thin-film PD is integrated with a polymer based waveguide grating device on a silicon platform. The fabricated optical sensor successfully discriminates optical spectral characteristics of the polymer waveguide grating from the on-chip PD. In addition, its potential use as a refractive index sensor is demonstrated. Based on a planar waveguide structure, the demonstrated sensor chip may incorporate multiple grating waveguide sensing regions with their own optical detection PDs. In addition, the demonstrated processing is based on a post-integration process which is compatible with silicon complementary metal-oxide semiconductor (CMOS) electronics. Potentially, this leads a compact, chip-scale optical sensing system which can monitor multiple physical parameters simultaneously without need for external signal processing. PMID:24466407

Large MOEMS diffraction grating results providing an EC-QCL wavelength scan of 20%

NASA Astrophysics Data System (ADS)

Grahmann, Jan; Merten, André; Herrmann, Andreas; Ostendorf, Ralf; Bleh, Daniela; Drabe, Christian; Kamenz, Jörg

2015-02-01

Experimental results of a large scanning grating with a diameter of 5mm and 1 kHz scan frequency are discussed. An optical diffraction grating is fabricated on a mirror single crystal silicon plate to scan the first diffraction order in the MIR-wavelength range over a quantum cascade laser facet. Special emphasis is on the development of the grating technology module to integrate it with high accuracy and reproducibility into the IPMS AME75 process flow. The principle EC-QCL setup with the scanning grating is described and first measurement results concerning laser output power and tuning range are presented.

On-chip broadband spectral filtering using planar double high-contrast grating reflectors

NASA Astrophysics Data System (ADS)

Horie, Yu; Arbabi, Amir; Faraon, Andrei

2015-02-01

We propose a broadband free-space on-chip spectrometer based on an array of integrated narrowband filters consisting of Fabry-Perot resonators formed by two high-contrast grating (HCG) based reflectors separated by a low-index thin layer with a fixed cavity thickness. Using numerical simulations, broadband tunability of resonance wavelengths was achieved only by changing the in-plane grating parameters such as period or duty cycle of HCGs while the substrate geometry was kept fixed. Experimentally, the HCG reflectors were fabricated on silicon on insulator (SOI) substrates and high reflectivity was measured, fabrication process for the proposed double HCG-based narrowband filter array was developed. The filtering function that can be spanned over a wide range of wavelengths was measured.

Fabrication of rippled surfaces for diffraction gratings by plastic deformation of platinum foils and metallic glasses

NASA Astrophysics Data System (ADS)

Korsukov, V. E.; Malygin, G. A.; Korsukova, M. M.; Nyapshaev, I. A.; Obidov, B. A.

2015-12-01

Thin platinum foils and metallic glass ribbons with a fractal surface consisting of different-scale unidirectionally oriented ripples have been fabricated using special thermoplastic processing. The general fractal dimension of the rippled surface and dimensions along and across the ripples have been measured. The optical spectra of a PRK-4 lamp using rippled Pt(111) foils as reflective diffraction gratings have been determined. A model describing the mechanism of the formation of surface unidirectional fractal structures during deformation has been proposed.

Diffraction efficiency of plasmonic gratings fabricated by electron beam lithography using a silver halide film

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sudheer,, E-mail: sudheer@rrcat.gov.in, E-mail: sudheer.rrcat@gmail.com; Tiwari, P.; Srivastava, Himanshu

2016-07-28

The silver nanoparticle surface relief gratings of ∼10 μm period are fabricated using electron beam lithography on the silver halide film substrate. Morphological characterization of the gratings shows that the period, the shape, and the relief depth in the gratings are mainly dependent on the number of lines per frame, the spot size, and the accelerating voltage of electron beam raster in the SEM. Optical absorption of the silver nanoparticle gratings provides a broad localized surface plasmon resonance peak in the visible region, whereas the intensity of the peaks depends on the number density of silver nanoparticles in the gratings. Themore » maximum efficiency of ∼7.2% for first order diffraction is observed for the grating fabricated at 15 keV. The efficiency is peaking at 560 nm with ∼380 nm bandwidth. The measured profiles of the diffraction efficiency for the gratings are found in close agreement with the Raman-Nath diffraction theory. This technique provides a simple and efficient method for the fabrication of plasmonic nanoparticle grating structures with high diffraction efficiency having broad wavelength tuning.« less

Fabrication of Achromatic Infrared Wave Plate by Direct Imprinting Process on Chalcogenide Glass

NASA Astrophysics Data System (ADS)

Yamada, Itsunari; Yamashita, Naoto; Tani, Kunihiko; Einishi, Toshihiko; Saito, Mitsunori; Fukumi, Kouhei; Nishii, Junji

2012-07-01

An achromatic infrared wave plate was fabricated by forming a subwavelength grating on the chalcogenide glass using direct imprint lithography. A low toxic chalcogenide glass (Sb-Ge-Sn-S system) substrate was imprinted with a grating of 1.63-µm depth, a fill factor of 0.7, and 3-µm period using glassy carbon as a mold at 253 °C and 3.8 MPa. Phase retardation of the element reached around 30° at 8.5-10.5 µm wavelengths, and the transmittance exceeded that of a flat substrate over 8 µm wavelength. Fabrication of the mid-infrared wave plate is thereby less expensive than that of conventional crystalline wave plates.

Tunable resonance-domain diffraction gratings based on electrostrictive polymers.

PubMed

Axelrod, Ramon; Shacham-Diamand, Yosi; Golub, Michael A

2017-03-01

Critical combination of high diffraction efficiency and large diffraction angles can be delivered by resonance-domain diffractive optics with high aspect ratio and wavelength-scale grating periods. To advance from static to electrically tunable resonance-domain diffraction grating, we resorted to its replication onto 2-5 μm thick P(VDF-TrFE-CFE) electrostrictive ter-polymer membranes. Electromechanical and optical computer simulations provided higher than 90% diffraction efficiency, a large continuous deflection range exceeding 20°, and capabilities for adiabatic spatial modulation of the grating period and slant. A prototype of the tunable resonance-domain diffraction grating was fabricated in a soft-stamp thermal nanoimprinting process, characterized, optically tested, and provided experimental feasibility proof for the tunable sub-micron-period gratings on electrostrictive polymers.

NASA Astrophysics Data System (ADS)

Schattenburg, Mark

Development of a Critical Angle Transmission Grating Spectrometer With APRA and SAT support, MIT has developed a unique blazed soft x-ray diffraction grating called the critical-angle transmission (CAT) grating. This device combines the high diffraction efficiency and resolving power of blazed reflection gratings with the low mass, low power, compact packaging and simple alignment of transmission gratings. We have shown that a spectrometer based on CAT gratings represents a huge leap forward in instrument scientific performance compared to previous missions, leading to much increased collecting area and spectral resolving power, which in turn results in orders-ofmagnitude improvement in figures-of-merit for emission and absorption line spectroscopy. MIT proposes to bring CAT x-ray grating spectrometer (CATXGS) technology to a higher Technology Readiness Level (TRL). We will increase fabrication yield and grating performance, and develop bonding techniques for grating membranes and alignment techniques for grating arrays. We will build and test robust grating arrays for space deployment, and perform thorough environmental testing. We are very close to achieving TRL4 and ready to move on to TRL5, which we can achieve within the period covered by this proposal. Our rapid progress over the last year was made possible by significant prior investments in our infrastructure, but further progress will require further investments. Since 2007 we have - with NASA support - demonstrated the CAT grating principle, and prototypes of increasing quality and size have verified theoretical predictions, putting the technology at a solid TRL3. Recent NASA and MIT investments in fabrication and metrology infrastructure has been justified by our rapid progress during the last year: the fabrication of practically defect-free CAT gratings with record diffraction efficiency, the demonstration of extended bandpass CAT gratings using conformal deposition of thin metal films via atomic layer deposition (ALD), and the demonstration of record-setting resolving power for an XGS on the order of R = 10,000, which exceeds the requirements for all currently proposed mission concepts. Grating fabrication still consumes the lion's share of our efforts and time. In order to maintain momentum and continue progress towards TRL5 in an efficient manner we need to improve our fabrication infrastructure further to accelerate grating fabrication and increase yield, so we can devote more resources to the new work required for reaching TRL5.

Polarization-independent broadband dielectric bilayer gratings for spectral beam combining system

NASA Astrophysics Data System (ADS)

Li, Linxin; Liu, Quan; Chen, Junming; Wang, Leilei; Jin, Yunxia; Yang, Yifeng; Shao, Jianda

2017-02-01

We report on a polarization-independent all-dielectric trapezoidal bilayer grating with broadband and high diffraction efficiency. The bilayer trapezoidal grating ridge on a reflector consists of an HfO2 layer and a SiO2 layer. The theoretical -1st order efficiencies of the grating are more than 95% with wavelength range from 1010 nm to 1080 nm for both TE and TM polarizations. The fabrication tolerances depending on the HfO2 and SiO2 layer grating ridge depths are enough to obtain the designed grating using current craft. The fabricated grating with exceeding 94% efficiency from 1000 nm to 1085 nm measured by a non-polarization laser has been fabricated and applied in a spectral beam combining external cavity to combine eight beams into one beam output with 10.77 kW.

Polarization-selective infrared bandpass filter based on a two-layer subwavelength metallic grating

NASA Astrophysics Data System (ADS)

Hohne, Andrew J.; Moon, Benjamin; Baumbauer, Carol L.; Gray, Tristan; Dilts, James; Shaw, Joseph A.; Dickensheets, David L.; Nakagawa, Wataru

2017-08-01

We present the design, fabrication, and characterization of a polarization-selective infrared bandpass filter based on a two-layer subwavelength metallic grating for use in polarimetric imaging. Gold nanowires were deposited via physical vapor deposition (PVD) onto a silicon surface relief grating that was patterned using electron beam lithography (EBL) and fabricated using standard silicon processing techniques. Optical characterization with a broad-spectrum tungsten halogen light source and a grating spectrometer showed normalized peak TM transmission of 53% with a full-width at half-maximum (FWHM) of 122 nm, which was consistent with rigorous coupled-wave analysis (RCWA) simulations. Simulation results suggested that device operation relied on suppression of the TM transmission caused by surface plasmon polariton (SPP) excitation at the gold-silicon interface and an increase in TM transmission caused by a Fabry-Perot (FP) resonance in the cavity between the gratings. TE rejection occurred at the initial air/gold interface. We also present simulation results of an improved design based on a two-dielectric grating where two different SPP resonances allowed us to improve the shape of the passband by suppressing the side lobes. This newer design resulted in improved side-band performance and increased peak TM transmission.

Application of holographic sub-wavelength diffraction gratings for monitoring of kinetics of bioprocesses

NASA Astrophysics Data System (ADS)

Tamulevičius, Tomas; Šeperys, Rimas; Andrulevičius, Mindaugas; Kopustinskas, Vitoldas; Meškinis, Šarūnas; Tamulevičius, Sigitas; Mikalayeva, Valeryia; Daugelavičius, Rimantas

2012-09-01

In this work we present a refractive index (RI) sensor based on a sub-wavelength holographic diffraction grating. The sensor chip was fabricated by dry etching of the finely spaced (d = 428 nm) diffraction grating in SiOx doped diamond like carbon (DLC) film. It is shown that employing a fabricated sensor chip, and using the proposed method of analysis of data, one can inspect kinetics of processes in liquids occurring in the vicinity of the grating surface. The method is based on the spectral composition analysis of polarized polychromatic light reflected from the sub-wavelength diffraction grating. The RI measurement system was tested with different model liquid analytes including 25 wt.%, 50 wt.% sugar water solutions, 10 °C, 50 °C distilled water, also Gram-positive bacteria Bacillus subtilis interaction with ion-permeable channels forming antibiotic gramicidin D and a murolytic enzyme lysozyme. Analysis of the data set of specular reflection spectra enabled us to follow the kinetics of the RI changes in the analyte with millisecond resolution. Detectable changes in the effective RI were not worse than Δn = 10-4.

Curved grating fabrication techniques for concentric-circle grating, surface-emitting semiconductor lasers

NASA Technical Reports Server (NTRS)

Jordan, Rebecca H.; King, Oliver; Wicks, Gary W.; Hall, Dennis G.; Anderson, Erik H.; Rooks, Michael J.

1993-01-01

We describe the fabrication and operational characteristics of a novel, surface-emitting semiconductor laser that makes use of a concentric-circle grating to both define its resonant cavity and to provide surface emission. A properly fabricated circular grating causes the laser to operate in radially inward- and outward-going circular waves in the waveguide, thus, introducing the circular symmetry needed for the laser to emit a beam with a circular cross-section. The basic circular-grating-resonator concept can be implemented in any materials system; an AlGaAs/GaAs graded-index, separate confinement heterostructure (GRINSCH), single-quantum-well (SQW) semiconductor laser, grown by molecular beam epitaxy (MBE), was used for the experiments discussed here. Each concentric-circle grating was fabricated on the surface of the AlGaAs/GaAs semiconductor laser. The circular pattern was first defined by electron-beam (e-beam) lithography in a layer of polymethylmethacrylate (PMMA) and subsequently etched into the semiconductor surface using chemically-assisted (chlorine) ion-beam etching (CAIBE). We consider issues that affect the fabrication and quality of the gratings. These issues include grating design requirements, data representation of the grating pattern, and e-beam scan method. We provide examples of how these techniques can be implemented and their impact on the resulting laser performance. A comparison is made of the results obtained using two fundamentally different electron-beam writing systems. Circular gratings with period lambda = 0.25 microns and overall diameters ranging from 80 microns to 500 microns were fabricated. We also report our successful demonstration of an optically pumped, concentric-circle grating, semiconductor laser that emits a beam with a far-field divergence angle that is less than one degree. The emission spectrum is quite narrow (less than 0.1 nm) and is centered at wavelength lambda = 0.8175 microns.

[Technology Development for X-Ray Reflection for the Constellation-X Reflection Grating Spectrometer (RGS)

NASA Technical Reports Server (NTRS)

Schattenburg, Mark L.

2003-01-01

This Grant covers MIT support for the technology development of x-ray reflection gratings for the Constellation-X Reflection Grating Spectrometer (RGS). Since the start of the Grant MIT has extended its previously-developed patterning and super-smooth, blazed grating fabrication technology to ten-times smaller grating periods and ten-times larger blaze angles to demonstrate feasibility and performance in the off-plane grating geometry. In the past year we successfully developed several nanoimprint grating replication methods that achieved very high fidelity replication of master silicon gratings. Grating geometry on the nano and macro scales were faithfully replicated, demonstrating the viability of the process for manufacturing the thousands of gratings required for the RGS. We also successfully developed an improved metrology truss for holding test grating substrates during metrology. The flatness goal of grating substrates is under 500 nm. In the past, grating holders would cause non-repeatable distortion of >> 500 nm to the substrates due to friction and gravity sag. The new holder has a repeatability of under 50 nm which is adequate for the proposed RGS grating substrates.

An investigation for the development of an integrated optical data preprocessor

NASA Technical Reports Server (NTRS)

Verber, C. M.; Vahey, D. W.; Kenan, R. P.; Wood, V. E.; Hartman, N. F.; Chapman, C. M.

1978-01-01

The successful fabrication and demonstration of an integrated optical circuit designed to perform a parallel processing operation by utilizing holographic subtraction to simultaneously compare N analog signal voltages with N predetermined reference voltages is summarized. The device alleviates transmission, storage and processing loads of satellite data systems by performing, at the sensor site, some preprocessing of data taken by remote sensors. Major accomplishments in the fabrication of integrated optics components include: (1) fabrication of the first LiNbO3 waveguide geodesic lens; (2) development of techniques for polishing TIR mirrors on LiNbO3 waveguides; (3) fabrication of high efficiency metal-over-photoresist gratings for waveguide beam splitters; (4) demonstration of high S/N holographic subtraction using waveguide holograms; and (5) development of alignment techniques for fabrication of integrated optics circuits. Important developments made in integrated optics are the discovery and suggested use of holographic self-subtraction in LiNbO3, development of a mathematical description of the operating modes of the preprocessor, and the development of theories for diffraction efficiency and beam quality of two dimensional beam defined gratings.

Electrodeposition of Gold to Conformally Fill High Aspect Ratio Nanometric Silicon Grating Trenches: A Comparison of Pulsed and Direct Current Protocols

PubMed Central

Znati, Sami A.; Chedid, Nicholas; Miao, Houxun; Chen, Lei; Bennett, Eric E.; Wen, Han

2016-01-01

Filling high-aspect-ratio trenches with gold is a frequent requirement in the fabrication of x-ray optics as well as micro-electronic components and other fabrication processes. Conformal electrodeposition of gold in sub-micron-width silicon trenches with an aspect ratio greater than 35 over a grating area of several square centimeters is challenging and has not been described in the literature previously. A comparison of pulsed plating and constant current plating led to a gold electroplating protocol that reliably filled trenches for such structures. PMID:27042384

GaSb-based single-mode distributed feedback lasers for sensing (Conference Presentation)

NASA Astrophysics Data System (ADS)

Gupta, James A.; Bezinger, Andrew; Lapointe, Jean; Poitras, Daniel; Aers, Geof C.

2017-02-01

GaSb-based tunable single-mode diode lasers can enable rapid, highly-selective and highly-sensitive absorption spectroscopy systems for gas sensing. In this work, single-mode distributed feedback (DFB) laser diodes were developed for the detection of various trace gases in the 2-3.3um range, including CO2, CO, HF, H2S, H2O and CH4. The lasers were fabricated using an index-coupled grating process without epitaxial regrowth, making the process significantly less expensive than conventional DFB fabrication. The devices are based on InGaAsSb/AlGaAsSb separate confinement heterostructures grown on GaSb by molecular beam epitaxy. DFB lasers were produced using a two step etch process. Narrow ridge waveguides were first defined by optical lithography and etched into the semiconductor. Lateral gratings were then defined on both sides of the ridge using electron-beam lithography and etched to produce the index-grating. Effective index modeling was used to optimize the ridge width, etch depths and the grating pitch to ensure single-lateral-mode operation and adequate coupling strength. The effective index method was further used to simulate the DFB laser emission spectrum, based on a transfer matrix model for light transmission through the periodic structure. The fabricated lasers exhibit single-mode operation which is tunable through the absorption features of the various target gases by adjustment of the drive current. In addition to the established open-path sensing applications, these devices have great potential for optoelectronic integrated gas sensors, making use of integrated photodetectors and possibly on-chip Si photonics waveguide structures.

Design and fabrication of directional diffractive device on glass substrate for multiview holographic 3D display

NASA Astrophysics Data System (ADS)

Su, Yanfeng; Cai, Zhijian; Liu, Quan; Zou, Wenlong; Guo, Peiliang; Wu, Jianhong

2018-01-01

Multiview holographic 3D display based on the nano-grating patterned directional diffractive device can provide 3D images with high resolution and wide viewing angle, which has attracted considerable attention. However, the current directional diffractive device fabricated on the photoresist is vulnerable to damage, which will lead to the short service life of the device. In this paper, we propose a directional diffractive device on glass substrate to increase its service life. In the design process, the period and the orientation of the nano-grating at each pixel are carefully calculated accordingly by the predefined position of the viewing zone, and the groove parameters are designed by analyzing the diffraction efficiency of the nano-grating pixel on glass substrate. In the experiment, a 4-view photoresist directional diffractive device with a full coverage of pixelated nano-grating arrays is efficiently fabricated by using an ultraviolet continuously variable spatial frequency lithography system, and then the nano-grating patterns on the photoresist are transferred to the glass substrate by combining the ion beam etching and the reactive ion beam etching for controlling the groove parameters precisely. The properties of the etched glass device are measured under the illumination of a collimated laser beam with a wavelength of 532nm. The experimental results demonstrate that the light utilization efficiency is improved and optimized in comparison with the photoresist device. Furthermore, the fabricated device on glass substrate is easier to be replicated and of better durability and practicability, which shows great potential in the commercial applications of 3D display terminal.

Novel thermal annealing methodology for permanent tuning polymer optical fiber Bragg gratings to longer wavelengths.

PubMed

Pospori, A; Marques, C A F; Sagias, G; Lamela-Rivera, H; Webb, D J

2018-01-22

The Bragg wavelength of a polymer optical fiber Bragg grating can be permanently shifted by utilizing the thermal annealing method. In all the reported fiber annealing cases, the authors were able to tune the Bragg wavelength only to shorter wavelengths, since the polymer fiber shrinks in length during the annealing process. This article demonstrates a novel thermal annealing methodology for permanently tuning polymer optical fiber Bragg gratings to any desirable spectral position, including longer wavelengths. Stretching the polymer optical fiber during the annealing process, the period of Bragg grating, which is directly related with the Bragg wavelength, can become permanently longer. The methodology presented in this article can be used to multiplex polymer optical fiber Bragg gratings at any desirable spectral position utilizing only one phase-mask for their photo-inscription, reducing thus their fabrication cost in an industrial setting.

Multiple Optical Traps with a Single-Beam Optical Tweezer Utilizing Surface Micromachined Planar Curved Grating

NASA Astrophysics Data System (ADS)

Kuo, Ju-Nan; Chen, Kuan-Yu

2010-11-01

In this paper, we present a single-beam optical tweezer integrated with a planar curved diffraction grating for microbead manipulation. Various curvatures of the surface micromachined planar curved grating are systematically investigated. The planar curved grating was fabricated using multiuser micro-electro-mechanical-system (MEMS) processes (MUMPs). The angular separation and the number of diffracted orders were determined. Experimental results indicate that the diffraction patterns and curvature of the planar curved grating are closely related. As the curvature of the planar curved grating increases, the vertical diffraction angle increases, resulting in the strip patterns of the planar curved grating. A single-beam optical tweezer integrated with a planar curved diffraction grating was developed. We demonstrate a technique for creating multiple optical traps from a single laser beam using the developed planar curved grating. The strip patterns of the planar curved grating that resulted from diffraction were used to trap one row of polystyrene beads.

Using a micro-molding process to fabricate polymeric wavelength filters

NASA Astrophysics Data System (ADS)

Chuang, Wei-Ching; Lee, An-Chen; Ho, Chi-Ting

2008-08-01

A procedure for fabricating a high aspect ratio periodic structure on a UV polymer at submicron order using holographic interferometry and molding processes is described. First, holographic interferometry using a He-Cd (325 nm) laser was used to create the master of the periodic line structure on an i-line sub-micron positive photoresist film. A 20 nm nickel thin film was then sputtered on the photoresist. The final line pattern on a UV polymer was obtained from casting against the master mold. Finally, a SU8 polymer was spun on the polymer grating to form a planar waveguide or a channel waveguide. The measurement results show that the waveguide length could be reduced for the waveguide having gratings with a high aspect ratio.

Design and fabrication of inverted rib waveguide Bragg grating

NASA Astrophysics Data System (ADS)

Huang, Cheng-Sheng; Wang, Wei-Chih

2009-03-01

A polymeric SU8 rib waveguide Bragg grating filterfabricated using reactive ion etching (RIE) and solvent assisted microcontact molding (SAMIM) is presented. SAMIM is one kind of soft lithography. The technique is unique in which that a composite hPDMS/PDMS stamp was used to transfer the grating pattern onto an inverted SU8 rib waveguide system. The composite grating stamp can be used repeatedly several times with degradation. Using this stamp and inverter rib waveguide structure, the Bragg grating filter fabrication can be significantly simplified.

Fabrication of the polarization independent spectral beam combining grating

NASA Astrophysics Data System (ADS)

Liu, Quan; Jin, Yunxia; Wu, Jianhong; Guo, Peiliang

2016-03-01

Owing to damage, thermal issues, and nonlinear optical effects, the output power of fiber laser has been proven to be limited. Beam combining techniques are the attractive solutions to achieve high-power high-brightness fiber laser output. The spectral beam combining (SBC) is a promising method to achieve high average power output without influencing the beam quality. A polarization independent spectral beam combining grating is one of the key elements in the SBC. In this paper the diffraction efficiency of the grating is investigated by rigorous coupled-wave analysis (RCWA). The theoretical -1st order diffraction efficiency of the grating is more than 95% from 1010nm to 1080nm for both TE and TM polarizations. The fabrication tolerance is analyzed. The polarization independent spectral beam combining grating with the period of 1.04μm has been fabricated by holographic lithography - ion beam etching, which are within the fabrication tolerance.

Multilayer dielectric diffraction gratings

DOEpatents

Perry, Michael D.; Britten, Jerald A.; Nguyen, Hoang T.; Boyd, Robert; Shore, Bruce W.

1999-01-01

The design and fabrication of dielectric grating structures with high diffraction efficiency used in reflection or transmission is described. By forming a multilayer structure of alternating index dielectric materials and placing a grating structure on top of the multilayer, a diffraction grating of adjustable efficiency, and variable optical bandwidth can be obtained. Diffraction efficiency into the first order in reflection varying between 1 and 98 percent has been achieved by controlling the design of the multilayer and the depth, shape, and material comprising the grooves of the grating structure. Methods for fabricating these gratings without the use of ion etching techniques are described.

Multilayer dielectric diffraction gratings

DOEpatents

Perry, M.D.; Britten, J.A.; Nguyen, H.T.; Boyd, R.; Shore, B.W.

1999-05-25

The design and fabrication of dielectric grating structures with high diffraction efficiency used in reflection or transmission is described. By forming a multilayer structure of alternating index dielectric materials and placing a grating structure on top of the multilayer, a diffraction grating of adjustable efficiency, and variable optical bandwidth can be obtained. Diffraction efficiency into the first order in reflection varying between 1 and 98 percent has been achieved by controlling the design of the multilayer and the depth, shape, and material comprising the grooves of the grating structure. Methods for fabricating these gratings without the use of ion etching techniques are described. 7 figs.

Research directed toward improved echelles for the ultraviolet. [large space teslescope spectrographs

NASA Technical Reports Server (NTRS)

1977-01-01

Low frequency gratings obtainable with present technology, can meet the grating-efficiency design goals for potential space telescope spectrographs. Gratings made with changes in the three specific parameters: the ruling tool profile, the coating material, and the lubricants used during the ruling process were compared. A series of coatings and test gratings were fabricated and were examined for surface smoothness with a Nomarski differential interference microscope and an electron microsocope. Photomicrographs were obtained to show the difference in smoothness of the various coatings and rulings. Efficiency measurements were made for those test rulings that showed good groove characteristics: smoothness, proper ruling depth, and absence of defects (e.g., streaks, feathered edges and rough sides). Higher grating efficiency should be correlated with the degree of smoothness of both the coating and the grating groove.

The potential of diffraction grating for spatial applications

NASA Astrophysics Data System (ADS)

Jourlin, Y.; Parriaux, O.; Pigeon, F.; Tischenko, A. V.

2017-11-01

Diffraction gratings are know, and have been fabricated for more than one century. They are now making a come back for two reasons: first, because they are now better understood which leads to the efficient exploitation of what was then called their "anomalies"; secondly, because they are now fabricable by means of the modern manufacturing potential of planar technologies. Novel grating can now perform better than conventional gratings, and address new application fields which were not expected to be theirs. This is the case of spatial applications where they can offer multiple optical functions, low size, low weight and mechanical robustness. The proposed contribution will briefly discuss the use of gratings for spatial applications. One of the most important applications is in the measurement of displacement. Usual translation and rotation sensors are bulky devices, which impose a system breakdown leading to cumbersome and heavy assemblies. We are proposing a miniaturized version of the traditional moving grating technique using submicron gratings and a specific OptoASIC which enables the measurement function to be non-obtrusively inserted into light and compact electro-mechanical systems. Nanometer resolution is possible with no compromise on the length of the measurement range. Another family of spatial application is in the field of spectrometers where new grating types allow a more flexible processing of the optical spectrum. Another family of applications addresses the question of inter-satellite communications: the introduction of gratings in laser cavities or in the laser mirrors enables the stabilization of the emitted polarization, the stabilization of the frequency as well as wide range frequency sweeping without mobile parts.

Optimization of nonbinary slanted surface-relief gratings as high-efficiency broadband couplers for light guides.

PubMed

Bai, Benfeng; Laukkanen, Janne; Kuittinen, Markku; Siitonen, Samuli

2010-10-01

We propose and investigate the use of slanted surface-relief gratings with nonbinary profiles as high-efficiency broadband couplers for light guides. First, a Chandezon-method-based rigorous numerical formulation is presented for modeling the slanted gratings with overhanging profiles. Then, two typical types of slanted grating couplers--a sinusoidal one and a trapezoidal one--are studied and optimized numerically, both exhibiting a high coupling efficiency of over 50% over the full band of white LED under the normal illumination of unpolarized light. Reasonable structural parameters with nice tolerance have been obtained for the optimized designs. It is found that the performance of the couplers depends little on the grating profile shape, but primarily on the grating period and the slant angle of the ridge. The underlying mechanism is analyzed by the equivalence rules of gratings, which provide useful guidelines for the design and fabrication of the couplers. Preliminary investigation has been performed on the fabrication and replication of the slanted overhanging grating couplers, which shows the feasibility of fabrication with mature microfabrication techniques and the perspective for mass production.

Feasibility evaluation of a neutron grating interferometer with an analyzer grating based on a structured scintillator.

PubMed

Kim, Youngju; Kim, Jongyul; Kim, Daeseung; Hussey, Daniel S; Lee, Seung Wook

2018-03-01

We introduce an analyzer grating based on a structured scintillator fabricated by a gadolinium oxysulfide powder filling method for a symmetric Talbot-Lau neutron grating interferometer. This is an alternative way to analyze the Talbot self-image of a grating interferometer without using an absorption grating to block neutrons. Since the structured scintillator analyzer grating itself generates the signal for neutron detection, we do not need an additional scintillator screen as an absorption analyzer grating. We have developed and tested an analyzer grating based on a structured scintillator in our symmetric Talbot-Lau neutron grating interferometer to produce high fidelity absorption, differential phase, and dark-field contrast images. The acquired images have been compared to results of a grating interferometer utilizing a typical absorption analyzer grating with two commercial scintillation screens. The analyzer grating based on the structured scintillator enhances interference fringe visibility and shows a great potential for economical fabrication, compact system design, and so on. We report the performance of the analyzer grating based on a structured scintillator and evaluate its feasibility for the neutron grating interferometer.

Feasibility evaluation of a neutron grating interferometer with an analyzer grating based on a structured scintillator

NASA Astrophysics Data System (ADS)

Kim, Youngju; Kim, Jongyul; Kim, Daeseung; Hussey, Daniel. S.; Lee, Seung Wook

2018-03-01

We introduce an analyzer grating based on a structured scintillator fabricated by a gadolinium oxysulfide powder filling method for a symmetric Talbot-Lau neutron grating interferometer. This is an alternative way to analyze the Talbot self-image of a grating interferometer without using an absorption grating to block neutrons. Since the structured scintillator analyzer grating itself generates the signal for neutron detection, we do not need an additional scintillator screen as an absorption analyzer grating. We have developed and tested an analyzer grating based on a structured scintillator in our symmetric Talbot-Lau neutron grating interferometer to produce high fidelity absorption, differential phase, and dark-field contrast images. The acquired images have been compared to results of a grating interferometer utilizing a typical absorption analyzer grating with two commercial scintillation screens. The analyzer grating based on the structured scintillator enhances interference fringe visibility and shows a great potential for economical fabrication, compact system design, and so on. We report the performance of the analyzer grating based on a structured scintillator and evaluate its feasibility for the neutron grating interferometer.

Moiré phase-shifted fiber Bragg gratings in polymer optical fibers

NASA Astrophysics Data System (ADS)

Min, Rui; Marques, Carlos; Bang, Ole; Ortega, Beatriz

2018-03-01

We demonstrate a simple way to fabricate phase-shifted fiber Bragg grating in polymer optical fibers as a narrowband transmission filter for a variety of applications at telecom wavelengths. The filters have been fabricated by overlapping two uniform fiber Bragg gratings with slightly different periods to create a Moiré grating with only two pulses (one pulse is 15 ns) of UV power. Experimental characterization of the filter is provided under different conditions where the strain and temperature sensitivities were measured.

Nearly amorphous Mo-N gratings for ultimate resolution in extreme ultraviolet interference lithography

NASA Astrophysics Data System (ADS)

Wang, L.; Kirk, E.; Wäckerlin, C.; Schneider, C. W.; Hojeij, M.; Gobrecht, J.; Ekinci, Y.

2014-06-01

We present fabrication and characterization of high-resolution and nearly amorphous Mo1 - xNx transmission gratings and their use as masks for extreme ultraviolet (EUV) interference lithography. During sputter deposition of Mo, nitrogen is incorporated into the film by addition of N2 to the Ar sputter gas, leading to suppression of Mo grain growth and resulting in smooth and homogeneous thin films with a negligible grain size. The obtained Mo0.8N0.2 thin films, as determined by x-ray photoelectron spectroscopy, are characterized to be nearly amorphous using x-ray diffraction. We demonstrate a greatly reduced Mo0.8N0.2 grating line edge roughness compared with pure Mo grating structures after e-beam lithography and plasma dry etching. The amorphous Mo0.8N0.2 thin films retain, to a large extent, the benefits of Mo as a phase grating material for EUV wavelengths, providing great advantages for fabrication of highly efficient diffraction gratings with extremely low roughness. Using these grating masks, well-resolved dense lines down to 8 nm half-pitch are fabricated with EUV interference lithography.

Enhancement of Light Absorption in Silicon Nanowire Photovoltaic Devices with Dielectric and Metallic Grating Structures.

PubMed

Park, Jin-Sung; Kim, Kyoung-Ho; Hwang, Min-Soo; Zhang, Xing; Lee, Jung Min; Kim, Jungkil; Song, Kyung-Deok; No, You-Shin; Jeong, Kwang-Yong; Cahoon, James F; Kim, Sun-Kyung; Park, Hong-Gyu

2017-12-13

We report the enhancement of light absorption in Si nanowire photovoltaic devices with one-dimensional dielectric or metallic gratings that are fabricated by a damage-free, precisely aligning, polymer-assisted transfer method. Incorporation of a Si 3 N 4 grating with a Si nanowire effectively enhances the photocurrents for transverse-electric polarized light. The wavelength at which a maximum photocurrent is generated is readily tuned by adjusting the grating pitch. Moreover, the electrical properties of the nanowire devices are preserved before and after transferring the Si 3 N 4 gratings onto Si nanowires, ensuring that the quality of pristine nanowires is not degraded during the transfer. Furthermore, we demonstrate Si nanowire photovoltaic devices with Ag gratings using the same transfer method. Measurements on the fabricated devices reveal approximately 27.1% enhancement in light absorption compared to that of the same devices without the Ag gratings without any degradation of electrical properties. We believe that our polymer-assisted transfer method is not limited to the fabrication of grating-incorporated nanowire photovoltaic devices but can also be generically applied for the implementation of complex nanoscale structures toward the development of multifunctional optoelectronic devices.

Fabrication of Long Period Gratings by Periodically Removing the Coating of Cladding-Etched Single Mode Optical Fiber Towards Optical Fiber Sensor Development.

PubMed

Ascorbe, Joaquin; Corres, Jesus M; Del Villar, Ignacio; Matias, Ignacio R

2018-06-07

Here, we present a novel method to fabricate long period gratings using standard single mode optical fibers (SMF). These optical devices were fabricated in a three-step process, which consisted of etching the SMF, then coating it with a thin-film and, the final step, which involved removing sections of the coating periodically by laser ablation. Tin dioxide was chosen as the material for this study and it was sputtered using a pulsed DC sputtering system. Theoretical simulations were performed in order to select the appropriate parameters for the experiments. The responses of two different devices to different external refractive indices was studied, and the maximum sensitivity obtained was 6430 nm/RIU for external refractive indices ranging from 1.37 to 1.39.

Infrared wire-grid polarizer with sol-gel antireflection films on both sides

NASA Astrophysics Data System (ADS)

Yamada, Itsunari; Ishihara, Yoshiro

2017-12-01

We fabricated an infrared wire-grid polarizer with the high transverse magnetic (TM) polarization transmittance and high extinction ratio by soft imprint lithography, sol-gel method, and Al shadow coating processes. A zilconia film was coated on Si substrate by using sol-gel method and spin coating method. Then, sol-gel zirconia grating was formed on the back side using imprinting using a silicone mold. The polarizer was produced by depositing Al obliquely on the grating. The TM transmittance of the fabricated element was greater than 80% at a wavelength of 4.8 μm. The sol-gel zilconia films acted as antireflection films. The extinction ratio exceeded 26 dB at its wavelength.

Initial Trial using Embedded Fibre Bragg Gratings for Distributed Strain Monitoring in a Shape Adaptive Composite Foil

DTIC Science & Technology

2012-02-01

available for interrogation. Although commercially available fibre Bragg grating ( FBG ) sensors have emerged in the marketplace over the past decade...the results from a preliminary trial investigating the feasibility of using embedded FBG arrays in a shape adaptive composite foil to characterise...The response from the FBG sensors was also monitored during fabrication of the foil during the resin infusion and curing stages of the process

Refractive index engineering of high performance coupler for compact photonic integrated circuits

NASA Astrophysics Data System (ADS)

Liu, Lu; Zhou, Zhiping

2017-04-01

High performance couplers are highly desired in many applications, but the design is limited by nearly unchangeable material refractive index. To tackle this issue, refractive index engineering method is investigated, which can be realized by subwavelength grating. Subwavelength gratings are periodical structures with pitches small enough to locally synthesize the refractive index of photonic waveguides, which allows direct control of optical profile as well as easier fabrication process. This review provides an introduction to the basics of subwavelength structures and pay special attention to the design strategies of some representative examples of subwavelength grating devices, including: edge couplers, fiber-chip grating couplers, directional couplers and multimode interference couplers. Benefited from the subwavelength grating which can engineer the refractive index as well as birefringence and dispersion, these devices show better performance when compared to their conventional counterparts.

Volume gratings and welding of glass/plastic by femtosecond laser direct writing

NASA Astrophysics Data System (ADS)

Watanabe, Wataru

2018-01-01

Femtosecond laser direct writing is used to fabricate diffractive optical elements in three dimensions and to weld glass and/or plastic. In this paper, we review volume gratings in plastics and welding of glass/plastic by femtosecond laser direct writing. Volume gratings were embedded inside polymethyl methacrylate (PMMA) by femtosecond laser pulses. The diffraction efficiency of the gratings increased after fabrication and reached the maximum. After an initial slow decrease within first several days after the fabrication, the efficiency increased again. This phenomena was called regeneration of the grating. We also demonstrate welding of PMMA by dendrite pattern using femtosecond laser pulses. Laser pulses are focused at the interface of two PMMA substrates with an air gap and melted materials in laser-irradiated region spread within a gap of the substrates and dendrite morphology of melted PMMA was observed outside the laser irradiated area. Finally, we show welding of glass/plastic and metal.

Comparison between high- and zero-contrast gratings as VCSEL mirrors

NASA Astrophysics Data System (ADS)

Liu, Anjin; Zheng, Wanhua; Bimberg, Dieter

2017-04-01

This study presents a comparison between high-contrast gratings (HCGs) and zero-contrast gratings (ZCGs) for high-speed vertical-cavity surface-emitting lasers (VCSELs). Both types of gratings exhibit high reflectivities beyond 99.5% due to the destructive interference at the output plane, but the HCG has a broader high reflectivity band. The HCG has a lower reflection delay time and smaller energy penetration length than the ZCG. The HCG has poorer mode selectivity for the VCSEL than the ZCG. The fabrication of the ZCG is less complex but with tight fabrication tolerances.

Nano-indentation and laser-induced damage testing in optical multilayer-dielectric gratings [Nanomechanics and laser-induced damage in optical multilayer dielectric gratings

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mehrotra, K.; Corning Research & Development Corp., Coming, NY; Taylor, B. N.

Here, we demonstrate how a nanomechanical test can be used to generate metrics to complement laser-induced–damage testing (LIDT) measurements and show that differences in optical performance of the gratings (arising from changes in cleaning process and/or fabrication methods) can be related to their mechanical reliability. Data are presented on LIDT measurements in diffractive gratings of silica deposited on optical multilayers. The nano-indentation response of the diffraction gratings is measured in a new mode that allows for the extraction of a measurable metric characterizing the brittleness of the gratings, as well as their ductility. We show that lower LIDT’s are positivelymore » correlated with an increased grating brittleness, and therefore identify a nanomechanical approach to describe LIDT’s. We present extensive numerical simulations of nano-indentation tests and identify different deformation modes including stretching, shear concentration, and bending as precursors to mechanical failure in the nano-indentation test. The effects of geometrical inhomogeneities on enhanced stress generation in these gratings are specifically examined and addressed.« less

Nano-indentation and laser-induced damage testing in optical multilayer-dielectric gratings [Nanomechanics and laser-induced damage in optical multilayer dielectric gratings

DOE PAGES

Mehrotra, K.; Corning Research & Development Corp., Coming, NY; Taylor, B. N.; ...

2017-03-16

Here, we demonstrate how a nanomechanical test can be used to generate metrics to complement laser-induced–damage testing (LIDT) measurements and show that differences in optical performance of the gratings (arising from changes in cleaning process and/or fabrication methods) can be related to their mechanical reliability. Data are presented on LIDT measurements in diffractive gratings of silica deposited on optical multilayers. The nano-indentation response of the diffraction gratings is measured in a new mode that allows for the extraction of a measurable metric characterizing the brittleness of the gratings, as well as their ductility. We show that lower LIDT’s are positivelymore » correlated with an increased grating brittleness, and therefore identify a nanomechanical approach to describe LIDT’s. We present extensive numerical simulations of nano-indentation tests and identify different deformation modes including stretching, shear concentration, and bending as precursors to mechanical failure in the nano-indentation test. The effects of geometrical inhomogeneities on enhanced stress generation in these gratings are specifically examined and addressed.« less

Nearly amorphous Mo-N gratings for ultimate resolution in extreme ultraviolet interference lithography.

PubMed

Wang, L; Kirk, E; Wäckerlin, C; Schneider, C W; Hojeij, M; Gobrecht, J; Ekinci, Y

2014-06-13

We present fabrication and characterization of high-resolution and nearly amorphous Mo1 - xNx transmission gratings and their use as masks for extreme ultraviolet (EUV) interference lithography. During sputter deposition of Mo, nitrogen is incorporated into the film by addition of N2 to the Ar sputter gas, leading to suppression of Mo grain growth and resulting in smooth and homogeneous thin films with a negligible grain size. The obtained Mo0.8N0.2 thin films, as determined by x-ray photoelectron spectroscopy, are characterized to be nearly amorphous using x-ray diffraction. We demonstrate a greatly reduced Mo0.8N0.2 grating line edge roughness compared with pure Mo grating structures after e-beam lithography and plasma dry etching. The amorphous Mo0.8N0.2 thin films retain, to a large extent, the benefits of Mo as a phase grating material for EUV wavelengths, providing great advantages for fabrication of highly efficient diffraction gratings with extremely low roughness. Using these grating masks, well-resolved dense lines down to 8 nm half-pitch are fabricated with EUV interference lithography.

Diffraction grating-based sensing optofluidic device for measuring the refractive index of liquids.

PubMed

Calixto, Sergio; Bruce, Neil C; Rosete-Aguilar, Martha

2016-01-11

We describe a simple and versatile optical sensing device for measuring refractive index of liquids. The sensor consists of a sinusoidal relief grating in a glass cell. Device calibration is done by pouring in the cell different liquids of known refractive indices. Each time a liquid is poured first order intensity is measured. The fabrication process and testing of the prototype device is described. An application in the measurement of temperature is also presented.

Pressure sensitivity of dual resonant long-period gratings written in boron co-doped optical fiber

NASA Astrophysics Data System (ADS)

Smietana, Mateusz; Bock, Wojtek J.; Mikulic, Predrag; Chen, Jiahua; Wisniewski, Roland

2011-05-01

The paper presents a pressure sensor based on a long-period grating (LPG) written in boron co-doped photosensitive fiber and operating at the phase-matching turning point. It is shown that the pressure sensitivity can be tuned by varying the UV exposure time during the LPG fabrication process. The achieved pressure sensitivity can reach over 1 nm•bar-1, and is at least four times higher than for previously presented gratings working away from the double-resonance regime. In terms of intensity-based measurement, the sensitivity at the turning point can reach 0.212 dB•bar-1.

Optical-fiber-to-waveguide coupling using carbon-dioxide-laser-induced long-period fiber gratings.

PubMed

Bachim, Brent L; Ogunsola, Oluwafemi O; Gaylord, Thomas K

2005-08-15

Optical fibers are expected to play a role in chip-level and board-level optical interconnects because of limitations on the bandwidth and level of integration of electrical interconnects. Therefore, methods are needed to couple optical fibers directly to waveguides on chips and on boards. We demonstrate optical-fiber-to-waveguide coupling using carbon-dioxide laser-induced long-period fiber gratings (LPFGs). Such gratings can be written in standard fiber and offer wavelength multiplexing-demultiplexing performance. The coupler fabrication process and the characterization apparatus are presented. The operation and the wavelength response of a LPFG-based optical-fiber-to-waveguide directional coupler are demonstrated.

CMOS-Compatible Fabrication for Photonic Crystal-Based Nanofluidic Structure.

PubMed

Peng, Wang; Chen, Youping; Ai, Wu; Zhang, Dailin; Song, Han; Xiong, Hui; Huang, Pengcheng

2017-12-01

Photonic crystal (PC)-based devices have been widely used since 1990s, while PC has just stepped into the research area of nanofluidic. In this paper, photonic crystal had been used as a complementary metal oxide semiconductors (CMOS) compatible part to create a nanofluidic structure. A nanofluidic structure prototype had been fabricated with CMOS-compatible techniques. The nanofluidic channels were sealed by direct bonding polydimethylsiloxane (PDMS) and the periodic gratings on photonic crystal structure. The PC was fabricated on a 4-in. Si wafer with Si 3 N 4 as the guided mode layer and SiO 2 film as substrate layer. The higher order mode resonance wavelength of PC-based nanofluidic structure had been selected, which can confine the enhanced electrical field located inside the nanochannel area. A design flow chart was used to guide the fabrication process. By optimizing the fabrication device parameters, the periodic grating of PC-based nanofluidic structure had a high-fidelity profile with fill factor at 0.5. The enhanced electric field was optimized and located within the channel area, and it can be used for PC-based nanofluidic applications with high performance.

Reflectance spectra characteristics from an SPR grating fabricated by nano-imprint lithography technique for biochemical nanosensor applications

NASA Astrophysics Data System (ADS)

Setiya Pradana, Jalu; Hidayat, Rahmat

2018-04-01

In this paper, we report our research work on developing a Surface Plasmon Resonance (SPR) element with sub-micron (hundreds of nanometers) periodicity grating structure. This grating structure was fabricated by using a simple nano-imprint lithography technique from an organically siloxane polymers, which was then covered by nanometer thin gold layer. The formed grating structure was a very well defined square-shaped periodic structure. The measured reflectance spectra indicate the SPR wave excitation on this grating structure. For comparison, the simulations of reflectance spectra have been also carried out by using Rigorous Coupled-Wave Analysis (RCWA) method. The experimental results are in very good agreement with the simulation results.

Terahertz bandwidth photonic Hilbert transformers based on synthesized planar Bragg grating fabrication.

PubMed

Sima, Chaotan; Gates, J C; Holmes, C; Mennea, P L; Zervas, M N; Smith, P G R

2013-09-01

Terahertz bandwidth photonic Hilbert transformers are proposed and experimentally demonstrated. The integrated device is fabricated via a direct UV grating writing technique in a silica-on-silicon platform. The photonic Hilbert transformer operates at bandwidths of up to 2 THz (~16 nm) in the telecom band, a 10-fold greater bandwidth than any previously reported experimental approaches. Achieving this performance requires detailed knowledge of the system transfer function of the direct UV grating writing technique; this allows improved linearity and yields terahertz bandwidth Bragg gratings with improved spectral quality. By incorporating a flat-top reflector and Hilbert grating with a waveguide coupler, an ultrawideband all-optical single-sideband filter is demonstrated.

SU8 inverted-rib waveguide Bragg grating filter.

PubMed

Huang, Cheng-Sheng; Wang, Wei-Chih

2013-08-01

A polymeric SU8 inverted-rib waveguide Bragg grating filter fabricated using reactive ion etching (RIE) and solvent assisted microcontact molding (SAMIM) is presented. SAMIM is one kind of soft lithography. The technique is unique in that a composite hard-polydimethysiloxane/polydimethysiloxane stamp is used to transfer the grating pattern onto an inverted SU8 rib waveguide system. The composite grating stamp can be used repeatedly several times without degradation. Using this stamp and inverter-rib waveguide structure, the Bragg grating filter fabrication can be significantly simplified. The experiment result shows an attenuation dip in the transmission spectra, with a value of -7 dBm at 1550 nm for a grating with a period of 0.492 μm on an inverted-rib waveguide with 6.6 μm width and 4 μm height.

L-shaped fiber-chip grating couplers with high directionality and low reflectivity fabricated with deep-UV lithography.

PubMed

Benedikovic, Daniel; Alonso-Ramos, Carlos; Pérez-Galacho, Diego; Guerber, Sylvain; Vakarin, Vladyslav; Marcaud, Guillaume; Le Roux, Xavier; Cassan, Eric; Marris-Morini, Delphine; Cheben, Pavel; Boeuf, Frédéric; Baudot, Charles; Vivien, Laurent

2017-09-01

Grating couplers enable position-friendly interfacing of silicon chips by optical fibers. The conventional coupler designs call upon comparatively complex architectures to afford efficient light coupling to sub-micron silicon-on-insulator (SOI) waveguides. Conversely, the blazing effect in double-etched gratings provides high coupling efficiency with reduced fabrication intricacy. In this Letter, we demonstrate for the first time, to the best of our knowledge, the realization of an ultra-directional L-shaped grating coupler, seamlessly fabricated by using 193 nm deep-ultraviolet (deep-UV) lithography. We also include a subwavelength index engineered waveguide-to-grating transition that provides an eight-fold reduction of the grating reflectivity, down to 1% (-20  dB). A measured coupling efficiency of -2.7  dB (54%) is achieved, with a bandwidth of 62 nm. These results open promising prospects for the implementation of efficient, robust, and cost-effective coupling interfaces for sub-micrometric SOI waveguides, as desired for large-volume applications in silicon photonics.

Fabricating waveguide Bragg gratings (WBGs) in bulk materials using ultrashort laser pulses

NASA Astrophysics Data System (ADS)

Ams, Martin; Dekker, Peter; Gross, Simon; Withford, Michael J.

2017-01-01

Optical waveguide Bragg gratings (WBGs) can be created in transparent materials using femtosecond laser pulses. The technique is conducted without the need for lithography, ion-beam fabrication methods, or clean room facilities. This paper reviews the field of ultrafast laser-inscribed WBGs since its inception, with a particular focus on fabrication techniques, WBG characteristics, WBG types, and WBG applications.

Sub-wavelength grating structure on the planar waveguide (Conference Presentation)

NASA Astrophysics Data System (ADS)

Qing-Song, Zhu; Sheng-Hui, Chen

2016-10-01

Making progress in recent years, with the technology of the grating, the grating period can be reduced to shrink the size of the light coupler on a waveguide. The working wavelength of the light coupler can be in the range from the near-infrared to visible. In this study , we used E-gun evaporation system with ion-beam-assisted deposition system to fabricate bottom cladding (SiO2), guiding layer (Ta2O5) and Distributed Bragg Reflector(DBR) of the waveguide on the silicon substrate. Electron-beam lithography is used to make sub-wavelength gratings and reflector grating on the planar waveguide which is a coupling device on the guiding layer. The best fabrication parameters were analyzed to deposit the film. The exposure and development times also influenced to fabricate the grating quality. The purpose is to reduce the device size and enhance coupling efficiency which maintain normal incidence of the light . We designed and developed the device using the Finite-Difference Time-Domain (FDTD) method. The grating period, depth, fill factor, film thickness, Distributed Bragg Reflector(DBR) numbers and reflector grating period have been discussed to enhance coupling efficiency and maintained normal incidence of the light. According to the simulation results, when the wavelength is 1300 nm, the coupling grating period is 720 nm and the Ta2O5 film is 460 nm with 360 nm of reflector grating period and 2 layers of Distributed Bragg Reflector, which had the optimum coupling efficiency and normal incidence angle. In the measurement, We successfully measured the TE wave coupling efficiency of the photoresist grating coupling device.

Fiber facet gratings for high power fiber lasers

NASA Astrophysics Data System (ADS)

Vanek, Martin; Vanis, Jan; Baravets, Yauhen; Todorov, Filip; Ctyroky, Jiri; Honzatko, Pavel

2017-12-01

We numerically investigated the properties of diffraction gratings designated for fabrication on the facet of an optical fiber. The gratings are intended to be used in high-power fiber lasers as mirrors either with a low or high reflectivity. The modal reflectance of low reflectivity polarizing grating has a value close to 3% for TE mode while it is significantly suppressed for TM mode. Such a grating can be fabricated on laser output fiber facet. The polarizing grating with high modal reflectance is designed as a leaky-mode resonant diffraction grating. The grating can be etched in a thin layer of high index dielectric which is sputtered on fiber facet. We used refractive index of Ta2O5 for such a layer. We found that modal reflectance can be close to 0.95 for TE polarization and polarization extinction ratio achieves 18 dB. Rigorous coupled wave analysis was used for fast optimization of grating parameters while aperiodic rigorous coupled wave analysis, Fourier modal method and finite difference time domain method were compared and used to compute modal reflectance of designed gratings.

Dopants concentration effects on the wavelength shift of long-period fiber gratings used as liquid level detectors

NASA Astrophysics Data System (ADS)

Mao, Barerem-Melgueba; Zhou, Bin

2011-12-01

Two liquid level sensors based on different long-period fiber gratings are proposed and compared. The long-period gratings have the same characteristics (length, grating period) but are fabricated in different optical fibers (photosensitive B-Ge codoped optical fibers with different dopants concentrations). The principle of this type of sensor is based on the refractive index sensitivity of long-period fiber gratings. By monitoring the resonant wavelength shifts of a given attenuation band, one can measure the immersed lengths of long-period fiber gratings and then the liquid level. The levels of two different solutions are measured. The maximum shift (7.69 nm) of the investigated resonance wavelength was observed in LPG1 (fabricated in Fibercore PS1250/1500). By controlling the fiber dopants concentrations one can improve the readouts of a fiber-optic liquid level sensor based on long-period fiber gratings.

Optical devices combining an organic semiconductor crystal with a two-dimensional inorganic diffraction grating

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kitazawa, Takenori; Yamao, Takeshi, E-mail: yamao@kit.ac.jp; Hotta, Shu

2016-02-01

We have fabricated optical devices using an organic semiconductor crystal as an emission layer in combination with a two-dimensional (2D) inorganic diffraction grating used as an optical cavity. We formed the inorganic diffraction grating by wet etching of aluminum-doped zinc oxide (AZO) under a 2D cyclic olefin copolymer (COC) diffraction grating used as a mask. The COC diffraction grating was fabricated by nanoimprint lithography. The AZO diffraction grating was composed of convex prominences arranged in a triangular lattice. The organic crystal placed on the AZO diffraction grating indicated narrowed peaks in its emission spectrum under ultraviolet light excitation. These aremore » detected parallel to the crystal plane. The peaks were shifted by rotating the optical devices around the normal to the crystal plane, which reflected the rotational symmetries of the triangular lattice through 60°.« less

Research directed toward improved echelles for the ultraviolet

NASA Technical Reports Server (NTRS)

1977-01-01

Research was undertaken to demonstrate that improved efficiencies for low frequency gratings are obtainable with the careful application of present technology. The motivation for the study was the desire to be assured that the grating-efficiency design goals for potential Space Telescope spectrographs can be achieved. The work was organized to compare gratings made with changes in the three specific parameters: the ruling tool profile, the coating material, and the lubricants used during the ruling process. A series of coatings and test gratings were fabricated and were examined for surface smoothness with a Nomarski Differential Interference Microscope and an electron microscope. Photomicrographs were obtained to show the difference in smoothness of the various coatings and rulings. Efficiency measurements were made for those test rulings that showed good groove characteristics: smoothness, proper ruling depth, and absence of defects. The intuitive feeling that higher grating efficiency should be correlated with the degree of smoothness of both the coating and the grating is supported by the results.

Fabricating Blazed Diffraction Gratings by X-Ray Lithography

NASA Technical Reports Server (NTRS)

Mouroulis, Pantazis; Hartley, Frank; Wilson, Daniel

2004-01-01

Gray-scale x-ray lithography is undergoing development as a technique for fabricating blazed diffraction gratings. As such, gray-scale x-ray lithography now complements such other grating-fabrication techniques as mechanical ruling, holography, ion etching, laser ablation, laser writing, and electron-beam lithography. Each of these techniques offers advantages and disadvantages for implementing specific grating designs; no single one of these techniques can satisfy the design requirements for all applications. Gray-scale x-ray lithography is expected to be advantageous for making gratings on steeper substrates than those that can be made by electron-beam lithography. This technique is not limited to sawtooth groove profiles and flat substrates: various groove profiles can be generated on arbitrarily shaped (including highly curved) substrates with the same ease as sawtooth profiles can be generated on flat substrates. Moreover, the gratings fabricated by this technique can be made free of ghosts (spurious diffraction components attributable to small spurious periodicities in the locations of grooves). The first step in gray-scale x-ray lithography is to conformally coat a substrate with a suitable photoresist. An x-ray mask (see Figure 1) is generated, placed between the substrate and a source of collimated x-rays, and scanned over the substrate so as to create a spatial modulation in the exposure of the photoresist. Development of the exposed photoresist results in a surface corrugation that corresponds to the spatial modulation and that defines the grating surface. The grating pattern is generated by scanning an appropriately shaped x-ray area mask along the substrate. The mask example of Figure 1 would generate a blazed grating profile when scanned in the perpendicular direction at constant speed, assuming the photoresist responds linearly to incident radiation. If the resist response is nonlinear, then the mask shape can be modified to account for the nonlinearity and produce a desired groove profile. An example of grating grooves generated by this technique is shown in Figure 2. A maximum relative efficiency of 88 percent has been demonstrated.

Realization of back-side heterogeneous hybrid III-V/Si DBR lasers for silicon photonics

NASA Astrophysics Data System (ADS)

Durel, Jocelyn; Ferrotti, Thomas; Chantre, Alain; Cremer, Sébastien; Harduin, Julie; Bernabé, Stéphane; Kopp, Christophe; Boeuf, Frédéric; Ben Bakir, Badhise; Broquin, Jean-Emmanuel

2016-02-01

In this paper, the simulation, design and fabrication of a back-side coupling (BSC) concept for silicon photonics, which targets heterogeneous hybrid III-V/Si laser integration is presented. Though various demonstrations of a complete SOI integration of passive and active photonic devices have been made, they all feature multi-level planar metal interconnects, and a lack of integrated light sources. This is mainly due to the conflict between the need of planar surfaces for III-V/Si bonding and multiple levels of metallization. The proposed BSC solution to this topographical problem consists in fabricating lasers on the back-side of the Si waveguides using a new process sequence. The devices are based on a hybrid structure composed of an InGaAsP MQW active area and a Si-based DBR cavity. The emitted light wavelength is accordable within a range of 20 nm around 1.31μm thanks to thermal heaters and the laser output is fiber coupled through a Grating Coupler (GC). From a manufacturing point of view, the BSC approach provides not only the advantages of allowing the use of a thin-BOX SOI instead of a thick one; but it also shifts the laser processing steps and their materials unfriendly to CMOS process to the far back-end areas of fabrication lines. Moreover, aside from solving technological integration issues, the BSC concept offers several new design opportunities for active and passive devices (heat sink, Bragg gratings, grating couplers enhanced with integrated metallic mirrors, tapers…). These building boxes are explored here theoretically and experimentally.

Development of a wavelength tunable filter using MEMS technology

NASA Astrophysics Data System (ADS)

Liu, Junting

Microelectromechanical systems (MEMS) for optical applications have received intensive attention in recent years because of their potential applications in optical telecommunication. Traditional wavelength division multiplexing (WDM) offers high capacity but requires the fabrication of selective add-drop filters. MEMS technology offers an effective way to fabricate these components at low cost. This thesis presents the development of a device that tunes the Bragg wavelength by coupling into the evanescent field of the grating. A Bragg grating is a periodic perturbation of the refractive index along a fiber or a periodic perturbation of the structure of a planar waveguide. The Bragg wavelength can be tuned by changing the degree to which a dielectric slab couples into the evanescent field. The result is a change in the effective index of the grating, and thus a change in the wavelength that which it reflects. In this thesis Bragg gratings were successfully written into an optical fiber using phase mask technique. Mechanical polishing was used to side-polish the fiber and remove cladding to expose the core. Grating structures were also fabricated in planar waveguide using E-beam writing and dry etching. In order to achieve the smoothest possible morphology of the waveguide, plasma dry etching of transparent substrates was studied in great detail. It is found that the pre-etch cleaning procedure greatly influences the ability to obtain a smooth etched surface. Upper limits of evanescent field tuning were investigated by applying different index liquids such as D. I. water and index matching oils or by positioning different dielectric materials such as glass and silicon close to the grating. Planar waveguides were found to be more sensitive to effective index change. Two kinds of computer simulation were carried out to understand the mode profile and to estimate the value of effective index of planar waveguide under "dry" and "wet" conditions. The first one used an average depth of grating approximation. The second explicitly considered the corrugated structure of the waveguide. Results of both simulations were compared with the experimental results in order to find the proper simulation approach. The fiber or planar waveguide gratings were "device" integrated and their pro and cons were compared. Devices using an optical fiber employed a microactuator driven by electrothermal vibromotor to change the degree of coupling between fiber and "tuning block". Device using planar waveguides used an electrostatic force actuated membrane, flip-chip mounted atop the waveguide. All devices were fabricated using polysilicon surface micromachining processes. I concluded that devices driven by electrostatic force were easier to actuate and their integration with waveguide less challenging.

SWS grating for UV band filter by nano-imprint

NASA Astrophysics Data System (ADS)

Lin, Jian-Shian; Liao, Ke-Hao; Chen, Chang-Tai; Lai, Chieh-Lung; Ko, Cheng-Hao

2009-05-01

Regarding to researches on manufacturing process, the fabrication of nano structures on SWS (subwavelength structured) grating are mainly produced by photo lithography. We find that UV light transmission efficiency of PET film significantly drops 50% when we put nano structures on the surface of material. In this paper, we add nano structures on the surface of PET film and create a UV band filter. Decent optical filtering effects can be achieved by combining the characteristics of PET materials with nano structures on their surfaces.

Binary-Phase Fourier Gratings for Nonuniform Array Generation

NASA Technical Reports Server (NTRS)

Keys, Andrew S.; Crow, Robert W.; Ashley, Paul R.

2003-01-01

We describe a design method for a binary-phase Fourier grating that generates an array of spots with nonuniform, user-defined intensities symmetric about the zeroth order. Like the Dammann fanout grating approach, the binary-phase Fourier grating uses only two phase levels in its grating surface profile to generate the final spot array. Unlike the Dammann fanout grating approach, this method allows for the generation of nonuniform, user-defined intensities within the final fanout pattern. Restrictions governing the specification and realization of the array's individual spot intensities are discussed. Design methods used to realize the grating employ both simulated annealing and nonlinear optimization approaches to locate optimal solutions to the grating design problem. The end-use application driving this development operates in the near- to mid-infrared spectrum - allowing for higher resolution in grating specification and fabrication with respect to wavelength than may be available in visible spectrum applications. Fabrication of a grating generating a user-defined nine spot pattern is accomplished in GaAs for the near-infrared. Characterization of the grating is provided through the measurement of individual spot intensities, array uniformity, and overall efficiency. Final measurements are compared to calculated values with a discussion of the results.

Monitoring the fabrication of tapered optical fibres

NASA Astrophysics Data System (ADS)

Mullaney, K.; Correia, R.; Staines, S. E.; James, S. W.; Tatam, R. P.

2017-04-01

A variety of optical methods to enhance the process of making optical fibre tapers are explored. A thermal camera was used to both refine the alignment of the optical components and optimize the laser power profile during the tapering process. The fibre transmission was measured to verify that the tapers had the requisite optical characteristics while the strain experienced by the fibre while tapering was assessed using an optical fibre Bragg grating. Using these techniques, adiabatic tapers were fabricated with a 2% insertion loss.

Miniaturized diffraction based interferometric distance measurement sensor

NASA Astrophysics Data System (ADS)

Kim, Byungki

In this thesis, new metrology hardware is designed, fabricated, and tested to provide improvements over current MEMS metrology. The metrology system is a micromachined scanning interferometer (muSI) having a sub-nm resolution in a compact design. The proposed microinterferometer forms a phase sensitive diffraction grating with interferomeric sensitivity, while adding the capability of better lateral resolution by focusing the laser to a smaller spot size. A detailed diffraction model of the microinterferometer was developed to simulate the device performance and to suggest the location of photo detectors for integrated optoelectronics. A particular device is fabricated on a fused silica substrate using aluminum to form the deformable diffraction grating fingers and AZ P4620 photo resist (PR) for the microlens. The details of the fabrication processes are presented. The structure also enables optoelectronics to be integrated so that the interferometer with photo detectors can fit in an area that is 1 mm x 1 mm. The scanning results using a fixed grating muSI demonstrated that it could measure vibration profile as well as static vertical (less than a half wave length) and lateral dimension of MEMS. The muSI, which is integrated with photo diodes, demonstrated its operation by scanning a cMUT. The PID control has been tested and resulted in improvement in scanned images. The integrated muSI demonstrated that the deformable grating could be used to tune the measurement keep the interferometer in quadrature for highest sensitivity.

Textured micrometer scale templates as light managing fabrication platform for organic solar cells

DOEpatents

Chaudhary, Sumit; Ho, Kai-Ming; Park, Joong-Mok; Nalwa, Kanwar Singh; Leung, Wai Y.

2016-07-26

A three-dimensional, microscale-textured, grating-shaped organic solar cell geometry. The solar cells are fabricated on gratings to give them a three-dimensional texture that provides enhanced light absorption. Introduction of microscale texturing has a positive effect on the overall power conversion efficiency of the devices. This grating-based solar cell having a grating of pre-determined pitch and height has shown improved power-conversion efficiency over a conventional flat solar cell. The improvement in efficiency is accomplished by homogeneous coverage of the grating with uniform thickness of the active layer, which is attributed to a sufficiently high pitch and low height of the underlying gratings. Also the microscale texturing leads to suppressed reflection of incident light due to the efficient coupling of the incident light into modes that are guided in the active layer.

Wet-chemical fabrication of a single leakage-channel grating coupler

NASA Astrophysics Data System (ADS)

Weisenbach, Lori; Zelinski, Brian J. J.; Roncone, Ronald L.; Burke, James J.

1995-04-01

We demonstrate the fabrication of a unique optical device, the single leakage-channel grating coupler, using sol-gel techniques. Design specifications are outlined to establish the material criteria for the sol-gel compositions. Material choice and preparation are described. We evaluate the characteristics and performance of the single leakage-channel grating coupler by comparing the predicted and the measured branching ratios. The branching ratio of the solution-derived device is within 3% of the theoretically predicted value.

Embedded high-contrast distributed grating structures

DOEpatents

Zubrzycki, Walter J.; Vawter, Gregory A.; Allerman, Andrew A.

2002-01-01

A new class of fabrication methods for embedded distributed grating structures is claimed, together with optical devices which include such structures. These new methods are the only known approach to making defect-free high-dielectric contrast grating structures, which are smaller and more efficient than are conventional grating structures.

Long-period fiber grating fabricated by 800 nm femtosecond laser pulses

NASA Astrophysics Data System (ADS)

Zhang, Yani; Xi, Yaru; Liu, Sicong; Jiang, Peng; Zhao, Ya; Xu, Qiang

2018-02-01

In this paper, the long period fiber gratings (LPFGs) in standard SMF-28 telecommunication fibers without hydrogen loading were inscribed by using point-to-point direct writing method of femtosecond laser pulses with pulse duration of 100 fs, repetition rate of 1kHz and a central wavelength of 800 nm. The LPFGs with different spectral characteristics were fabricated by adjusting grating period, grating length and duty ratio. The results show that the resonant peak wavelengths shift to the long-wave direction with the increase of the grating length increasing. The variations of duty ratio will lead to the generation of resonance rejection band of LPFGs from singlepeak to multi-peak plus lesser out-of-band loss.

Experimental demonstration of a multi-wavelength distributed feedback semiconductor laser array with an equivalent chirped grating profile based on the equivalent chirp technology.

PubMed

Li, Wangzhe; Zhang, Xia; Yao, Jianping

2013-08-26

We report, to the best of our knowledge, the first realization of a multi-wavelength distributed feedback (DFB) semiconductor laser array with an equivalent chirped grating profile based on equivalent chirp technology. All the lasers in the laser array have an identical grating period with an equivalent chirped grating structure, which are realized by nonuniform sampling of the gratings. Different wavelengths are achieved by changing the sampling functions. A multi-wavelength DFB semiconductor laser array is fabricated and the lasing performance is evaluated. The results show that the equivalent chirp technology is an effective solution for monolithic integration of a multi-wavelength laser array with potential for large volume fabrication.

Transmission grating spectroscopy and the Advanced X-ray Astrophysics Facility (AXAF)

NASA Technical Reports Server (NTRS)

Schattenburg, M. L.; Canizares, C. R.; Dewey, D.; Levine, A. M.; Markert, T. H.

1988-01-01

The use of transmission gratings with grazing-incidence telescopes in celestial X-ray astrononmy is reviewed. The basic properties of transmission grating spectrometers and the use of 'phased' gratings to enhance the diffraction efficiency are outlined. The fabrication of the gratings is examined, giving special attention to the AXAF High Energy Transmission Grating. The performance of finite-period thick gratings is briefly discussed, and the performance of the transmission grating spectrometers planned for SPECTROSAT and AXAF are examined.

Polycrystalline PLZT/ITO Ceramic Electro-Optic Phase Gratings: Electro- Optically Reconfigurable Diffractive Devices for Free-Space and In-Wafer Interconnects

DTIC Science & Technology

1994-09-01

free-space and waveguide interconnects is investigated through the fabrication, testing and modeling of polycrystalline PLZT/ITO ceramic electro - optic phase...only gratings. PLZT Diffraction grating, Electro - optic diffraction grating, Optical switching, Optical interconnects, Reconfigurable interconnect

Planar techniques for fabricating X-ray diffraction gratings and zone plates

NASA Technical Reports Server (NTRS)

Smith, H. I.; Anderson, E. H.; Hawryluk, A. M.; Schattenburg, M. L.

1984-01-01

The state of current planar techniques in the fabrication of Fresnel zone plates and diffraction gratings is reviewed. Among the fabrication techniques described are multilayer resist techniques; scanning electron beam lithography; and holographic lithography. Consideration is also given to: X-ray lithography; ion beam lithography; and electroplating. SEM photographs of the undercut profiles obtained in a type AZ 135OB photoresistor by holographic lithography are provided.

Large area fabrication of plasmonic nanoparticle grating structure by conventional scanning electron microscope

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sudheer,, E-mail: sudheer@rrcat.gov.in; Tiwari, P.; Rai, V. N.

Plasmonic nanoparticle grating (PNG) structure of different periods has been fabricated by electron beam lithography using silver halide based transmission electron microscope film as a substrate. Conventional scanning electron microscope is used as a fabrication tool for electron beam lithography. Optical microscope and energy dispersive spectroscopy (EDS) have been used for its morphological and elemental characterization. Optical characterization is performed by UV-Vis absorption spectroscopic technique.

[Development of Nanotechnology for X-Ray Astronomy Instrumentation

NASA Technical Reports Server (NTRS)

Schattenburg, Mark L.

2004-01-01

This Research Grant provides support for development of nanotechnology for x-ray astronomy instrumentation. MIT has made significant progress in several development areas. In the last year we have made considerable progress in demonstrating the high-fidelity patterning and replication of x-ray reflection gratings. We developed a process for fabricating blazed gratings in silicon with extremely smooth and sharp sawtooth profiles, and developed a nanoimprint process for replication. We also developed sophisticated new fixturing for holding thin optics during metrology without causing distortion. We developed a new image processing algorithm for our Shack-Hartmann tool that uses Zernike polynomials. This has resulted in much more accurate and repeatable measurements on thin optics.

One-step sol-gel imprint lithography for guided-mode resonance structures.

PubMed

Huang, Yin; Liu, Longju; Johnson, Michael; C Hillier, Andrew; Lu, Meng

2016-03-04

Guided-mode resonance (GMR) structures consisting of sub-wavelength periodic gratings are capable of producing narrow-linewidth optical resonances. This paper describes a sol-gel-based imprint lithography method for the fabrication of submicron 1D and 2D GMR structures. This method utilizes a patterned polydimethylsiloxane (PDMS) mold to fabricate the grating coupler and waveguide for a GMR device using a sol-gel thin film in a single step. An organic-inorganic hybrid sol-gel film was selected as the imprint material because of its relatively high refractive index. The optical responses of several sol-gel GMR devices were characterized, and the experimental results were in good agreement with the results of electromagnetic simulations. The influence of processing parameters was investigated in order to determine how finely the spectral response and resonant wavelength of the GMR devices could be tuned. As an example potential application, refractometric sensing experiments were performed using a 1D sol-gel device. The results demonstrated a refractive index sensitivity of 50 nm/refractive index unit. This one-step fabrication process offers a simple, rapid, and low-cost means of fabricating GMR structures. We anticipate that this method can be valuable in the development of various GMR-based devices as it can readily enable the fabrication of complex shapes and allow the doping of optically active materials into sol-gel thin film.

Fabrication of Fiber-Optic Tilted Bragg Grating Filter in 40 nm Range with A Single Phase Mask

NASA Technical Reports Server (NTRS)

Grant, Joseph; Wang, Y.; Sharma, A.; Burdine, Robert V. (Technical Monitor)

2002-01-01

Fiber-optic Bragg grating filters are fabricated with a range of Bragg wavelength between 1296 and 1336 nm, using a single phase mask. 30 mW of continuous-wave light at 244 nm is used from a frequency-doubled argon-ion laser having an intracavity etalon. Gratings are fabricated by tilting the photosensitive fiber with respect to the phase mask up to an angle of 15 degrees. The variation of Bragg wavelength with the fiber-tilt is explained with a simple formula. High spatial coherence of 244 nm light makes it possible to displace the fiber as much as 6 mm in front of the phase mask and tilt the fiber by as much as 15 degrees. This results in nearly constant band-width and near 100% reflectively for all gratings throughout the 40 nm range.

Fabrication of high aspect ratio TiO{sub 2} and Al{sub 2}O{sub 3} nanogratings by atomic layer deposition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shkondin, Evgeniy, E-mail: eves@fotonik.dtu.dk; Takayama, Osamu; Lavrinenko, Andrei V.

The authors report on the fabrication of TiO{sub 2} and Al{sub 2}O{sub 3} nanostructured gratings with an aspect ratio of up to 50. The gratings were made by a combination of atomic layer deposition (ALD) and dry etch techniques. The workflow included fabrication of a Si template using deep reactive ion etching followed by ALD of TiO{sub 2} or Al{sub 2}O{sub 3}. Then, the template was etched away using SF{sub 6} in an inductively coupled plasma tool, which resulted in the formation of isolated ALD coatings, thereby achieving high aspect ratio grating structures. SF{sub 6} plasma removes silicon selectively withoutmore » any observable influence on TiO{sub 2} or Al{sub 2}O{sub 3}, thus revealing high selectivity throughout the fabrication. Scanning electron microscopy was used to analyze every fabrication step. Due to nonreleased stress in the ALD coatings, the top parts of the gratings were observed to bend inward as the Si template was removed, thus resulting in a gradual change in the pitch value of the structures. The pitch on top of the gratings is 400 nm, and it gradually reduces to 200 nm at the bottom. The form of the bending can be reshaped by Ar{sup +} ion beam etching. The chemical purity of the ALD grown materials was analyzed by x-ray photoelectron spectroscopy. The approach presented opens the possibility to fabricate high quality optical metamaterials and functional nanostructures.« less

Magnetoresistance and magnetization in submicron ferromagnetic gratings

NASA Astrophysics Data System (ADS)

Shearwood, C.; Blundell, S. J.; Baird, M. J.; Bland, J. A. C.; Gester, M.; Ahmed, H.; Hughes, H. P.

1994-05-01

A technique for engineering micron and submicron scale structures from magnetic films of transition metals has been developed using a combination of electron- and ion-beam lithography enabling high-quality arrays of submicron magnetic Fe wires to be fabricated. This process can be used to fabricate novel devices from a variety of metal combinations which would not be possible by the usual liftoff metallization method. The structure and magnetic properties are reported of an epitaxial 25 nm Fe(001)/GaAs(001) film and the wire gratings which are fabricated from it. The width of the wires in the grating is 0.5 μm for all structures studied, but the separation of each wire is varied in the range 0.5 to 16 μm. An artificially induced shape anisotropy field of around 1 kG, consistent with a magnetostatic calculation, was observed for all separations studied. The field dependence of the magneto-optic Kerr effect and magnetoresistance (MR) data is consistent with a twisted magnetization configuration across the width of the sample beneath saturation for transverse applied fields. In this case, the detailed form of the field dependence of the MR is strikingly modified from that observed in the continuous film and is consistent with coherent rotation of the magnetization.

Excitation of surface electromagnetic waves in a graphene-based Bragg grating

PubMed Central

Sreekanth, Kandammathe Valiyaveedu; Zeng, Shuwen; Shang, Jingzhi; Yong, Ken-Tye; Yu, Ting

2012-01-01

Here, we report the fabrication of a graphene-based Bragg grating (one-dimensional photonic crystal) and experimentally demonstrate the excitation of surface electromagnetic waves in the periodic structure using prism coupling technique. Surface electromagnetic waves are non-radiative electromagnetic modes that appear on the surface of semi-infinite 1D photonic crystal. In order to fabricate the graphene-based Bragg grating, alternating layers of high (graphene) and low (PMMA) refractive index materials have been used. The reflectivity plot shows a deepest, narrow dip after total internal reflection angle corresponds to the surface electromagnetic mode propagating at the Bragg grating/air boundary. The proposed graphene based Bragg grating can find a variety of potential surface electromagnetic wave applications such as sensors, fluorescence emission enhancement, modulators, etc. PMID:23071901

Excitation of surface electromagnetic waves in a graphene-based Bragg grating.

PubMed

Sreekanth, Kandammathe Valiyaveedu; Zeng, Shuwen; Shang, Jingzhi; Yong, Ken-Tye; Yu, Ting

2012-01-01

Here, we report the fabrication of a graphene-based Bragg grating (one-dimensional photonic crystal) and experimentally demonstrate the excitation of surface electromagnetic waves in the periodic structure using prism coupling technique. Surface electromagnetic waves are non-radiative electromagnetic modes that appear on the surface of semi-infinite 1D photonic crystal. In order to fabricate the graphene-based Bragg grating, alternating layers of high (graphene) and low (PMMA) refractive index materials have been used. The reflectivity plot shows a deepest, narrow dip after total internal reflection angle corresponds to the surface electromagnetic mode propagating at the Bragg grating/air boundary. The proposed graphene based Bragg grating can find a variety of potential surface electromagnetic wave applications such as sensors, fluorescence emission enhancement, modulators, etc.

Fast tunable blazed MEMS grating for external cavity lasers

NASA Astrophysics Data System (ADS)

Tormen, Maurizio; Niedermann, Philippe; Hoogerwerf, Arno; Shea, Herbert; Stanley, Ross

2017-11-01

Diffractive MEMS are interesting for a wide range of applications, including displays, scanners or switching elements. Their advantages are compactness, potentially high actuation speed and in the ability to deflect light at large angles. We have designed and fabricated deformable diffractive MEMS grating to be used as tuning elements for external cavity lasers. The resulting device is compact, has wide tunability and a high operating speed. The initial design is a planar grating where the beams are free-standing and attached to each other using leaf springs. Actuation is achieved through two electrostatic comb drives at either end of the grating. To prevent deformation of the free-standing grating, the device is 10 μm thick made from a Silicon on Insulator (SOI) wafer in a single mask process. At 100V a periodicity tuning of 3% has been measured. The first resonant mode of the grating is measured at 13.8 kHz, allowing high speed actuation. This combination of wide tunability and high operating speed represents state of the art in the domain of tunable MEMS filters. In order to improve diffraction efficiency and to expand the usable wavelength range, a blazed version of the deformable MEMS grating has been designed. A key issue is maintaining the mechanical properties of the original device while providing optically smooth blazed beams. Using a process based on anisotropic KOH etching, blazed gratings have been obtained and preliminary characterization is promising.

Fabrication of three-dimensional polymer quadratic nonlinear grating structures by layer-by-layer direct laser writing technique

NASA Astrophysics Data System (ADS)

Bich Do, Danh; Lin, Jian Hung; Diep Lai, Ngoc; Kan, Hung-Chih; Hsu, Chia Chen

2011-08-01

We demonstrate the fabrication of a three-dimensional (3D) polymer quadratic nonlinear (χ(2)) grating structure. By performing layer-by-layer direct laser writing (DLW) and spin-coating approaches, desired photobleached grating patterns were embedded in the guest--host dispersed-red-1/poly(methylmethacrylate) (DR1/PMMA) active layers of an active-passive alternative multilayer structure through photobleaching of DR1 molecules. Polyvinyl-alcohol and SU8 thin films were deposited between DR1/PMMA layers serving as a passive layer to separate DR1/PMMA active layers. After applying the corona electric field poling to the multilayer structure, nonbleached DR1 molecules in the active layers formed polar distribution, and a 3D χ(2) grating structure was obtained. The χ(2) grating structures at different DR1/PMMA nonlinear layers were mapped by laser scanning second harmonic (SH) microscopy, and no cross talk was observed between SH images obtained from neighboring nonlinear layers. The layer-by-layer DLW technique is favorable to fabricating hierarchical 3D polymer nonlinear structures for optoelectronic applications with flexible structural design.

Fabrication of three-dimensional polymer quadratic nonlinear grating structures by layer-by-layer direct laser writing technique.

PubMed

Do, Danh Bich; Lin, Jian Hung; Lai, Ngoc Diep; Kan, Hung-Chih; Hsu, Chia Chen

2011-08-10

We demonstrate the fabrication of a three-dimensional (3D) polymer quadratic nonlinear (χ(2)) grating structure. By performing layer-by-layer direct laser writing (DLW) and spin-coating approaches, desired photobleached grating patterns were embedded in the guest-host dispersed-red-1/poly(methylmethacrylate) (DR1/PMMA) active layers of an active-passive alternative multilayer structure through photobleaching of DR1 molecules. Polyvinyl-alcohol and SU8 thin films were deposited between DR1/PMMA layers serving as a passive layer to separate DR1/PMMA active layers. After applying the corona electric field poling to the multilayer structure, nonbleached DR1 molecules in the active layers formed polar distribution, and a 3D χ(2) grating structure was obtained. The χ(2) grating structures at different DR1/PMMA nonlinear layers were mapped by laser scanning second harmonic (SH) microscopy, and no cross talk was observed between SH images obtained from neighboring nonlinear layers. The layer-by-layer DLW technique is favorable to fabricating hierarchical 3D polymer nonlinear structures for optoelectronic applications with flexible structural design.

Gratings Fabricated on Flat Surfaces and Reproduced on Non-Flat Substrates

NASA Technical Reports Server (NTRS)

Content, David; Iazikov, Dmitri; Mossberg, Thomas W.; Greiner, Christopher M.

2009-01-01

A method has been developed for fabricating gratings on flat substrates, and then reproducing the groove pattern on a curved (concave or convex) substrate and a corresponding grating device. First, surface relief diffraction grating grooves are formed on flat substrates. For example, they may be fabricated using photolithography and reactive ion etching, maskless lithography, holography, or mechanical ruling. Then, an imprint of the grating is made on a deformable substrate, such as plastic, polymer, or other materials using thermoforming, hot or cold embossing, or other methods. Interim stamps using electroforming, or other methods, may be produced for the imprinting process or if the same polarity of the grating image is required. The imprinted, deformable substrate is then attached to a curved, rigid substrate using epoxy or other suitable adhesives. The imprinted surface is facing away from the curved rigid substrate. As an alternative fabrication method, after grating is imprinted on the deformable substrate as described above, the grating may be coated with thin conformal conductive layer (for example, using vacuum deposition of gold). Then the membrane may be mounted over an opening in a pressured vessel in a manner of a membrane on a drum, grating side out. The pressure inside of the vessel may be changed with respect to the ambient pressure to produce concave or convex membrane surface. The shape of the opening may control the type of the surface curvature (for example, a circular opening would create spherical surface, oval opening would create toroidal surface, etc.). After that, well-known electroforming methods may be used to create a replica of the grating on the concave or convex membrane. For example, the pressure vessel assembly may be submerged into an electro-forming solution and negative electric potential applied to the metal coated membrane using an insulated wire. Positive electric potential may be then applied to a nickel or other metal plate submerged into the same solution. Metal ions would transfer from the plate through the solution into the membrane, producing high fidelity metal replica of the grating on the membrane. In one variation, an adhesive may be deposited on the deformable substrate, and then cured without touching the rigid, curved substrate. Edges of the deformable substrate may be attached to the rigid substrate to ensure uniform deformation of the deformable substrate. The assembly may be performed in vacuum, and then taken out to atmospheric pressure conditions to ensure that no air is trapped between the deformable and rigid substrates. Alternatively, a rigid surface with complementary curvature to the rigid substrate may be used to ensure uniform adhesion of the deformable substrate to the rigid substrate. Liquid may be applied to the surface of the deformable substrate to uniformly distribute pressure across its surface during the curing or hardening of the adhesive, or the film may be pressed into the surface using a deformable object or surface. After the attachment is complete, the grooves may be coated with reflective or dielectric layers to improve diffraction efficiency.

Nanointaglio fabrication of optical lipid multilayer diffraction gratings with applications in biosensing

NASA Astrophysics Data System (ADS)

Lowry, Troy Warren

The dynamic self-organization of lipids in biological systems is a highly regulated process that enables the compartmentalization of living systems at microscopic and nanoscopic levels. Exploiting the self-organization and innate biofunctionality of lyotropic liquid crystalline phospholipids, a novel nanofabrication process called "nanointaglio" was invented in order to rapidly and scalably integrate lipid nanopatterns onto the surface. The work presented here focuses on using nanointaglio fabricated lipid diffraction micro- and nanopatterns for the development of new sensing and bioactivity studies. The lipids are patterned as diffraction gratings for sensor functionality. The lipid multilayer gratings operate as nanomechanical sensor elements that are capable of transducing molecular binding to fluid lipid multilayers into optical signals in a label free manner due to shape changes in the lipid nanostructures. To demonstrate the label free detection capabilities, lipid nanopatterns are shown to be suitable for the integration of chemically different lipid multilayer gratings into a sensor array capable of distinguishing vapors by means of an optical nose. Sensor arrays composed of six different lipid formulations are integrated onto a surface and their optical response to three different vapors (water, ethanol and acetone) in air as well as pH under water is monitored as a function of time. Principal component analysis of the array response results in distinct clustering, indicating the suitability of the arrays for distinguishing these analytes. Importantly, the nanointaglio process used is capable of producing lipid gratings out of different materials with sufficiently uniform heights for the fabrication of an optical nose. A second main application is demonstrated for the study of membrane binding proteins. Although in vitro methods for assaying the catalytic activity of individual enzymes are well established, quantitative methods for assaying the kinetics of supramolecular remodeling such as vesicle formation from planar lipid bilayers or multilayers are needed to understand cellular self-organization. Presented next is a nanointaglio based method for quantitative measurements of lipid-protein interactions and its suitability for quantifying the membrane binding, inflation, and budding activity of the membrane-remodeling protein Sar1. Optical diffraction gratings composed of lipids are printed on surfaces using nanointaglio, resulting in lipid multilayer gratings. Exposure of lipid multilayer gratings to Sar1 results in the inflation of lipid multilayers into unilamellar structures, the kinetics of which can be detected in a label-free manner by monitoring the diffraction of white light through an optical microscope. Local variations in lipid multilayer volume on the surface can be used to vary substrate availability in a microarray format, allowing kinetic and thermodynamic data to be obtained from a single experiment without the need for varying enzyme concentration. A quantitative model is developed and fits to the data allow measurements of both binding affinity (KD) and kinetics (kon and koff). Importantly, this assay is uniquely capable of quantifying membrane remodeling. Upon Sar1 induced inflation of single bilayers from surface supported multilayers, the semi-cylindrical grating lines are observed to remodel into semi-spherical buds when a critical radius of curvature equal to 300 nm is reached, which is explained in terms of a Rayleigh type instability.

Temperature sensing through long period fiber gratings mechanically induced on tapered optical fibers.

PubMed

Pulido-Navarro, María Guadalupe; Escamilla-Ambrosio, Ponciano Jorge; Marrujo-García, Sigifredo; Álvarez-Chávez, José Alfredo; Martínez-Piñón, Fernando

2017-07-01

In this work the feasibility of employing two well-known techniques already used on designing optical fiber sensors is explored. The first technique employed involves monomode tapered fibers, which were fabricated using a taper machine designed, built, and implemented in our laboratory. This implementation greatly reduced the costs and fabrication time allowing us to produce the desired taper length and transmission conditions. The second technique used fiber Bragg gratings, which we decided to have mechanically induced and for that reason we devised and produced our own mechanical gratings with the help of a computer numerical control tool. This grating had to be fabricated with aluminum to withstand temperatures of up to 600°C. When light traveling through an optical fiber reaches a taper it couples into the cladding layer and comes back into the core when the taper ends. In the same manner, when the light encounters gratings in the fiber, it couples to the cladding modes, and when the gratings end, the light couples back into the core. For our experimentation, the tapering machine was programmed to fabricate single-mode tapers with 3 cm length, and the mechanically induced gratings characteristics were 5 cm length, and had a period of 500 μm and depth of the period of 300 μm. For the conducting tests, the tapered fiber is positioned in between two aluminum slabs, one grooved and the other plane. These two blocks accomplish the mechanically induced long period grating (LPG); the gratings on the grooved plaque are imprinted on the taper forming the period gratings. An optical spectrum analyzer is used to observe the changes on the transmission spectrum as the temperature varies from 20°C to 600°C. The resultant attenuation peak wavelength in the transmission spectrum shifts up to 8 nm, which is a higher shift compared to what has been reported using nontapered fibers. As the temperature increases there is no longer a shift, but there is significant power loss. Such a characteristic can be used as well for sensing applications.

High-directionality fiber-chip grating coupler with interleaved trenches and subwavelength index-matching structure.

PubMed

Benedikovic, Daniel; Alonso-Ramos, Carlos; Cheben, Pavel; Schmid, Jens H; Wang, Shurui; Xu, Dan-Xia; Lapointe, Jean; Janz, Siegfried; Halir, Robert; Ortega-Moñux, Alejandro; Wangüemert-Pérez, J Gonzalo; Molina-Fernández, Iñigo; Fédéli, Jean-Marc; Vivien, Laurent; Dado, Milan

2015-09-15

We present the first experimental demonstration of a new fiber-chip grating coupler concept that exploits the blazing effect by interleaving the standard full (220 nm) and shallow etch (70 nm) trenches in a 220 nm thick silicon layer. The high directionality is obtained by controlling the separation between the deep and shallow trenches to achieve constructive interference in the upward direction and destructive interference toward the silicon substrate. Utilizing this concept, the grating directionality can be maximized independent of the bottom oxide thickness. The coupler also includes a subwavelength-engineered index-matching region, designed to reduce the reflectivity at the interface between the injection waveguide and the grating. We report a measured fiber-chip coupling efficiency of -1.3  dB, the highest coupling efficiency achieved to date for a surface grating coupler in a 220 nm silicon-on-insulator platform fabricated in a conventional dual-etch process without high-index overlays or bottom mirrors.

Embedded fiber Bragg grating sensors for true temperature monitoring in Nb3Sn superconducting magnets for high energy physics

NASA Astrophysics Data System (ADS)

Chiuchiolo, A.; Bajas, H.; Bajko, M.; Consales, M.; Giordano, M.; Perez, J. C.; Cusano, A.

2016-05-01

The luminosity upgrade of the Large Hadron Collider (HL-LHC) planned at the European Organization for Nuclear Research (CERN) requires the development of a new generation of superconducting magnets based on Nb3Sn technology. The instrumentation required for the racetrack coils needs the development of reliable sensing systems able to monitor the magnet thermo-mechanical behavior during its service life, from the coil fabrication to the magnet operation. With this purpose, Fiber Bragg Grating (FBG) sensors have been embedded in the coils of the Short Model Coil (SMC) magnet fabricated at CERN. The FBG sensitivity to both temperature and strain required the development of a solution able to separate mechanical and temperature effects. This work presents for the first time a feasibility study devoted to the implementation of an embedded FBG sensor for the measurement of the "true" temperature in the impregnated Nb3Sn coil during the fabrication process.

Economic fabrication of a novel hybrid planar Grating/Fresnel lens for miniature spectrometers.

PubMed

Zhou, Qian; Li, Xinghui; Geng, Menglin; Hu, Haifei; Ni, Kai; Zhong, Lunchao; Yan, Peng; Wang, Xiaohao

2018-03-05

We propose a new technique to fabricate a highly specialized optical element, a hybrid planar Grating/Fresnel lens (G-Fresnel), which is particularly useful to improve or enable more-affordable miniature/portable spectrometers. Both the Fresnel and the grating surface are fabricated simultaneously by sandwiching soft PDMS between a hard grating and a pre-replicated negative Fresnel surface. Several adhesion reduction techniques are also investigated that help improve both fabrication and cost efficiency (by reducing the solidification time) as well as the lifetime of the mold. Alignment errors are systematically analyzed, and their effects on the G-Fresnel lens evaluated. A compact fabrication platform was built, which is smaller than a volume of 160☓140☓106 mm 3 to fit into a conventional vacuum drying oven, for the fabrication of a G-Fresnel lens with a diameter of 25.4 mm, an equivalent focal length of 25 mm, and a blazed grating pattern with 600 lines/mm spacing. The solidification time was reduced to 2 hours thanks to the improved adhesion reduction technique that permits a PDMS drying-temperature as high as 65 °C. The fabricated G-Fresnel lens was evaluated with regard to both geometrical fabrication precision and optical performance. The measured results, using a step gauge and atomic force microscopy, confirm that this replication technique produces high-quality replicates of the master surface-profile. Furthermore, a prototype spectrometer that uses a G-Fresnel lens was built and evaluated. The spectrometer fits within a volume of about 100 mm☓50 mm☓30 mm, and it operates across a wide wavelength spectrum (450 nm to 650 nm). Both the calculation based on the optical software ZEMAX and the experimental measurements are consistent and confirm that the spectrometer with the G-Fresnel lens can provide a spectral resolution of better than 1.2nm.

X-Ray Spectrometer For ROSAT II (SPECTROSAT)

NASA Astrophysics Data System (ADS)

Predehl, Peter; Brauninger, Heinrich

1986-01-01

The objective transmission grating was one of the earliest inventions in the field of X-ray astronomy and has been incorporated into Skylab, HERO-P, and EXOTAT. In recent years there have been advances in grating technology and spectrometer design. A high precision mechanical ruling and replication process for manufacturing large self-supporting transmission gratings has been developed by an industrial manufacturer in cooperation with the Max-Planck-Institute (MPI). Theoretical analyses have determined the optimum configuration of the grating facets and the grating surface in order to correct third order aberations and obtain maximum resolving power. We have verified experimentally that the predicted efficiencies may be achieved. In addition, an experimental study of large grating assemblies for space telescopes was made in industry with scientific guidance by MPI. Main objectives of this study were the determination of mechanical loads during launch, as well as the design, construction and fabrication of a representative model of a ROSAT grating ring. Performancy studies including instrument pro-perties as well as the simulated radiation from hot plasmas have shown the ability of SPECTROSAT to perform high efficiency, high resolution line-spectroscopy on a wide variety of cosmic X-ray sources.

Investigation of Structural Properties of Carbon-Epoxy Composites Using Fiber-Bragg Gratings

NASA Technical Reports Server (NTRS)

Grant, J.; Kaul, R.; Taylor, S.; Jackson, K.; Sharma, A.; Burdine, Robert V. (Technical Monitor)

2002-01-01

Fiber Bragg-gratings are embedded in carbon-epoxy laminates as well as bonded on the surface of cylindrical structures fabricated out of such composites. Structural properties of such composites is investigated. The measurements include stress-strain relation in laminates and Poisson's ratio in several specimens with varying orientation of the optical fiber Bragg-sensor with respect to the carbon fiber in an epoxy matrix. Additionally, Bragg gratings are bonded on the surface of cylinders fabricated out of carbon-epoxy composites and longitudinal and hoop strain on the surface is measured.

New ultraportable display technology and applications

NASA Astrophysics Data System (ADS)

Alvelda, Phillip; Lewis, Nancy D.

1998-08-01

MicroDisplay devices are based on a combination of technologies rooted in the extreme integration capability of conventionally fabricated CMOS active-matrix liquid crystal display substrates. Customized diffraction grating and optical distortion correction technology for lens-system compensation allow the elimination of many lenses and systems-level components. The MicroDisplay Corporation's miniature integrated information display technology is rapidly leading to many new defense and commercial applications. There are no moving parts in MicroDisplay substrates, and the fabrication of the color generating gratings, already part of the CMOS circuit fabrication process, is effectively cost and manufacturing process-free. The entire suite of the MicroDisplay Corporation's technologies was devised to create a line of application- specific integrated circuit single-chip display systems with integrated computing, memory, and communication circuitry. Next-generation portable communication, computer, and consumer electronic devices such as truly portable monitor and TV projectors, eyeglass and head mounted displays, pagers and Personal Communication Services hand-sets, and wristwatch-mounted video phones are among the may target commercial markets for MicroDisplay technology. Defense applications range from Maintenance and Repair support, to night-vision systems, to portable projectors for mobile command and control centers.

Design, Fabrication and Characterization of Micro Opto-Electro-Mechanical Systems.

DTIC Science & Technology

1995-12-01

interference problems (see Fig. 3-6). Improvements in the lithography of the MCNC process would allow for grating spaces of less than 2 gm and therefore...A micro-spectrometer has been fabricated using LIGA, an acronym for lithography , electroforming, and micromolding (the acronym came from the German...location for test samples and an adjustable mirror. The beams are brought back together to form an interference pattern. At an observation screen the

Femtosecond laser-inscribed fiber Bragg gratings for strain monitoring in power cables of offshore wind turbines.

PubMed

Burgmeier, Jörg; Schippers, Wolfgang; Emde, Nico; Funken, Peter; Schade, Wolfgang

2011-05-01

A fiber Bragg grating sensor system used for monitoring the effects of strain on the power cable of an offshore wind turbine is presented. The Bragg grating structure was inscribed into coated nonphotosensitive standard telecommunication fibers using an IR femtosecond laser and the point-by-point writing technique. Because of the presence of the protective coating of the fiber, the mechanical stability of the resultant sensor device is better than that of a sensor consisting of a bare fiber. A system containing this sensing element was to our knowledge for the first time successfully installed and tested in an offshore wind turbine prototype (REpower 6M, REpower Systems, AG, Germany) in February 2010, near Ellhöft (Germany). The fabrication process of the fiber Bragg gratings, measurement results of the online monitoring, and a comparison between the sensor signal and commonly used sensing techniques are presented.

A packaged, low-cost, robust optical fiber strain sensor based on small cladding fiber sandwiched within periodic polymer grating.

PubMed

Chiang, Chia-Chin; Li, Chein-Hsing

2014-06-02

In the present study, a novel packaged long-period fiber grating (PLPFG) strain sensor is first presented. The MEMS process was utilized to fabricate the packaged optical fiber strain sensor. The sensor structure consisted of etched optical fiber sandwiched between two layers of thick photoresist SU-8 3050 and then packaged with poly (dimethylsiloxane) (PDMS) polymer material to construct the PLPFG strain sensor. The PDMS packaging material was used to prevent the glue effect, wherein glue flows into the LPFG structure and reduces coupling strength, in the surface bonding process. Because the fiber grating was packaged with PDMS material, it was effectively protected and made robust. The resonance attenuation dip of PLPFG grows when it is loading. This study explored the size effect of the grating period and fiber diameter of PLPFG via tensile testing. The experimental results found that the best strain sensitivity of the PLPFG strain sensor was -0.0342 dB/με, and that an R2 value of 0.963 was reached.

[Development of X-ray Reflection Grating Technology for the Constellation-X Mission

NASA Technical Reports Server (NTRS)

Schattenburg, Mark L.

2005-01-01

This Grant supports MIT technology development of x-ray reflection gratings for the Constellation-X Reflection Grating Spectrometer (RGS). Since the start of the Grant MIT has extended its previously-developed patterning and super-smooth, blazed grating fabrication technology to ten-times smaller grating periods and ten-times larger blaze angles to demonstrate feasibility and performance in the off-plane grating geometry. In the past year we have focused our efforts on extending our Nanoruler grating fabrication tool to enable it to perform variable-period scanning-beam interference lithography (VP-SBIL). This new capability required extensive optical and mechanical improvements to the system. The design phase of this work is largely completed and key components are now on order and assembly has begun. Over the next several months the new VP-SBIL Nanoruler system will be completed and testing begun. We have also demonstrated a new technique for patterning gratings using the Nanoruler called Doppler mode, which will be important for patterning the radial groove gratings for the RGS using the new VP-SBIL system. Flat and thin grating substrates will be critical for the RGS. In the last year we demonstrated a new technique for flattening thin substrates using magneto-rheologic fluid polishing (MRF) and achieved 2 arcsecond flatness with a 0.5 mm-thick substrate-a world's record. This meets the Con X requirement for grating substrate flatness.

One-Dimensional Photonic Crystal Superprisms

NASA Technical Reports Server (NTRS)

Ting, David

2005-01-01

Theoretical calculations indicate that it should be possible for one-dimensional (1D) photonic crystals (see figure) to exhibit giant dispersions known as the superprism effect. Previously, three-dimensional (3D) photonic crystal superprisms have demonstrated strong wavelength dispersion - about 500 times that of conventional prisms and diffraction gratings. Unlike diffraction gratings, superprisms do not exhibit zero-order transmission or higher-order diffraction, thereby eliminating cross-talk problems. However, the fabrication of these 3D photonic crystals requires complex electron-beam substrate patterning and multilayer thin-film sputtering processes. The proposed 1D superprism is much simpler in structural complexity and, therefore, easier to design and fabricate. Like their 3D counterparts, the 1D superprisms can exhibit giant dispersions over small spectral bands that can be tailored by judicious structure design and tuned by varying incident beam direction. Potential applications include miniature gas-sensing devices.

Dispersion flattened single etch-step waveguide based on subwavelength grating

NASA Astrophysics Data System (ADS)

Jafari, Zeinab; Zarifkar, Abbas

2017-06-01

A novel subwavelength-grating-assisted (SWG-assisted) waveguide is proposed for dispersion flattening. Tuning the refractive index, which is a powerful tool in dispersion engineering, can be carried out through adjusting the properties of the SWG regions. It is particularly beneficial for controlling the flattened dispersion bandwidth. This will also eliminate the need for integration of other less compatible materials with silicon. Moreover, the SWG-assisted waveguide can be easily fabricated through a single etch-step process. By engineering the structural parameters of the waveguide, an ultra-flat dispersion profile with a total dispersion variation of 10 (ps/nm/km) over a wide bandwidth of 1615 nm is obtained. The possibility of bandwidth expansion, the fabrication friendly design, and the flattened dispersion profile of the proposed waveguide make it promising for wideband nonlinear applications.

Multi-parameter fiber optic sensors based on fiber random grating

NASA Astrophysics Data System (ADS)

Xu, Yanping; Zhang, Mingjiang; Lu, Ping; Mihailov, Stephen; Bao, Xiaoyi

2017-04-01

Two novel configurations of multi-parameter fiber-optic sensing systems based on the fiber random grating are reported. The fiber random grating is fabricated through femtosecond laser induced refractive index modification over a 10cm standard telecom single mode fiber. In one configuration, the reflective spectrum of the fiber random grating is directly detected and a wavelength-division spectral cross-correlation algorithm is adopted to extract the spectral shifts for simultaneous measurement of temperature, axial strain, and surrounding refractive index. In the other configuration, a random fiber ring laser is constructed by incorporating the random feedback from the random grating. Numerous polarization-dependent spectral filters are formed along the random grating and superimposed to provide multiple lasing lines with high signal-to-noise ratio up to 40dB, which enables a high-fidelity multi-parameter sensing scheme by monitoring the spectral shifts of the lasing lines. Without the need of phase mask for fabrication and with the high physical strength, the random grating based sensors are much simpler and more compact, which could be potentially an excellent alternative for liquid medical sample sensing in biomedical and biochemical applications.

Blazed vector grating liquid crystal cells with photocrosslinkable polymeric alignment films fabricated by one-step polarizer rotation method

NASA Astrophysics Data System (ADS)

Kawai, Kotaro; Kuzuwata, Mitsuru; Sasaki, Tomoyuki; Noda, Kohei; Kawatsuki, Nobuhiro; Ono, Hiroshi

2014-12-01

Blazed vector grating liquid crystal (LC) cells, in which the directors of low-molar-mass LCs are antisymmetrically distributed, were fabricated by one-step exposure of an empty glass cell inner-coated with a photocrosslinkable polymer LC (PCLC) to UV light. By adopting a LC cell structure, twisted nematic (TN) and homogeneous (HOMO) alignments were obtained in the blazed vector grating LC cells. Moreover, the diffraction efficiency of the blazed vector grating LC cells was greatly improved by increasing the thickness of the device in comparison with that of a blazed vector grating with a thin film structure obtained in our previous study. In addition, the diffraction efficiency and polarization states of ±1st-order diffracted beams from the resultant blazed vector grating LC cells were controlled by designing a blazed pattern in the alignment films, and these diffraction properties were well explained on the basis of Jones calculus and the elastic continuum theory of nematic LCs.

Holographic Gratings for Optical Processing

NASA Technical Reports Server (NTRS)

Kukhtarev, Nickolai

2002-01-01

Investigation of astronomical objects and tracking of man-made space objects lead to generation of huge amount of information for optical processing. Traditional big-size optical elements (such as optical telescopes) have a tendency for increasing aperture size in order to improve sensitivity. This tendency leads to increasing of weight and costs of optical systems and stimulate search for the new, more adequate technologies. One approach to meet these demands is based on developing of holographic optical elements using new polymeric materials. We have investigated possibility to use new material PQ-PMMA (phenantrenequinone-doped PMMA (Polymethyl Methacrylate)) for fabrication of highly selective optical filters and fast spatial-temporal light modulators. This material was originally developed in Russia and later was tested in CalTech as a candidate material for optical storage. Our theoretical investigation predicts the possibility of realization of fast spatial and temporal light modulation, using volume reflection-type spectral filter. We have developed also model of holographic-grating recording in PQ-PMMA material, based on diffusional amplification. This mechanism of recording allow to receive high diffraction efficiency during recording of reflection-type volume holographic grating (holographic mirror). We also investigated recording of dynamic gratings in the photorefractive crystals LiNbO3 (LN) for space-based spectroscopy and for adaptive correction of aberrations in the telescope's mirrors. We have shown, that specific 'photogalvanic' mechanism of holographic grating recording in LN allow to realize recording of blazed gratings for volume and surface gratings. Possible applications of dynamic gratings in LN for amplification of images, transmitted through an imaging fiber guide was also demonstrated.

Dense periodical patterns in photonic devices: Technology for fabrication and device performance

NASA Astrophysics Data System (ADS)

Chandramohan, Sabarish

For the fabrication, focused ion beam parameters are investigated to successfully fabricate dense periodical patterns, such as gratings, on hard transition metal nitride such as zirconium nitride. Transition metal nitrides such as titanium nitride and zirconium nitride have recently been studied as alternative materials for plasmonic devices because of its plasmonic resonance in the visible and near-infrared ranges, material strength, CMOS compatibility and optical properties resembling gold. Coupling of light on the surface of these materials using sub-micrometer gratings gives additional capabilities for wider applications. Here we report the fabrication of gratings on the surface of zirconium nitride using gallium ion 30keV dual beam focused ion beam. Scanning electron microscope imaging and atomic force microscope profiling is used to characterize the fabricated gratings. Appropriate values for FIB parameters such as ion beam current, magnification, dwell time and milling rate are found for successful milling of dense patterns on zirconium nitride. For the device performance, a real-time image-processing algorithm is developed to enhance the sensitivity of an optical miniature spectrometer. The novel approach in this design is the use of real-time image-processing algorithm to average the image intensity along the arc shaped images registered by the monochromatic inputs on the CMOS image sensor. This approach helps to collect light from the entire arc and thus enhances the sensitivity of the device. The algorithm is developed using SiTiO2 planar waveguide. The accuracy of the mapping from x-pixel number scale of the CMOS image sensor to the wavelength spectra of the miniature spectrometer is demonstrated by measuring the spectrum of a known LED source using a conventional desktop spectrometer and comparing it with the spectrum measured by the miniature spectrometer. The sensitivity of miniature spectrometer is demonstrated using two methods. In the first method, the input laser power is attenuated to 0.1 nW and the spectra is measured using the miniature spectrometer. Even at low input power of 0.1nW, the spectrum of monochromatic inputs is observed well above the noise level. Second method is by quantitative analysis, which measures the absorption of CdSeS/ZnS quantum dots drop casted between the gratings of Ta2O5 planar single-mode waveguide. The expected guided mode attenuation introduced by monolayer of quantum dots is found to be approximately 11 times above the highest noise level from the absorption measurements. Thus, the miniature spectrometer is capable of detecting the signal from the noise level even with the absorption introduced by monolayer of quantum dots.

Reflection color filters of the three primary colors with wide viewing angles using common-thickness silicon subwavelength gratings.

PubMed

Kanamori, Yoshiaki; Ozaki, Toshikazu; Hane, Kazuhiro

2014-10-20

We fabricated reflection color filters of the three primary colors with wide viewing angles using silicon two-dimensional subwavelength gratings on the same quartz substrate. The grating periods were 400, 340, and 300 nm for red, green, and blue filters, respectively. All of the color filters had the same grating thickness of 100 nm, which enabled simple fabrication of a color filter array. Reflected colors from the red, green, and blue filters under s-polarized white-light irradiation appeared in the respective colors at incident angles from 0 to 50°. By rigorous coupled-wave analysis, the dimensions of each color filter were designed, and the calculated reflectivity was compared with the measured reflectivity.

Relative humidity sensor based on surface plasmon resonance of D-shaped fiber with polyvinyl alcohol embedding Au grating

NASA Astrophysics Data System (ADS)

Yan, Haitao; Han, Daofu; Li, Ming; Lin, Bo

2017-01-01

This paper presents the design, fabrication, and characterization of a D-shaped fiber coated with polyvinyl alcohol (PVA) embedding an Au grating-based relative humidity (RH) sensor. The Au grating is fabricated on a D-shaped fiber to match the wave-vector and excite the surface plasmon, and the PVA is embedded in the Au grating as a sensitive cladding film. The refractive index of PVA changes with the ambient humidity. Measurements in a controlled environment show that the RH sensor can achieve a sensitivity of 5.4 nm per relative humidity unit in the RH range from 0% to 70% RH. Moreover, the surface plasmon resonance can be realized and used for RH sensing at the C band of optical fiber communication instead of the visible light band due to the metallic grating microstructure on the D-shaped fiber.

Blazed vector gratings fabricated using photosensitive polymer liquid crystals and control of polarization diffraction

NASA Astrophysics Data System (ADS)

Ono, Hiroshi; Kuzuwata, Mitsuru; Sasaki, Tomoyuki; Noda, Kohei; Kawatsuki, Nobuhiro

2014-03-01

The blazed vector grating possessing antisymmetric distributions of the birefringence were fabricated by exposing the line-focused linearly polarized ultraviolet light on the photosensitive polymer liquid crystals. The polarization states of the diffraction beams can be highly and widely controlled by designing the blazed structures, and the diffraction properties were well-explained by Jones calculus.

Efficient fabrication method of nano-grating for 3D holographic display with full parallax views.

PubMed

Wan, Wenqiang; Qiao, Wen; Huang, Wenbin; Zhu, Ming; Fang, Zongbao; Pu, Donglin; Ye, Yan; Liu, Yanhua; Chen, Linsen

2016-03-21

Without any special glasses, multiview 3D displays based on the diffractive optics can present high resolution, full-parallax 3D images in an ultra-wide viewing angle. The enabling optical component, namely the phase plate, can produce arbitrarily distributed view zones by carefully designing the orientation and the period of each nano-grating pixel. However, such 3D display screen is restricted to a limited size due to the time-consuming fabricating process of nano-gratings on the phase plate. In this paper, we proposed and developed a lithography system that can fabricate the phase plate efficiently. Here we made two phase plates with full nano-grating pixel coverage at a speed of 20 mm²/mins, a 500 fold increment in the efficiency when compared to the method of E-beam lithography. One 2.5-inch phase plate generated 9-view 3D images with horizontal-parallax, while the other 6-inch phase plate produced 64-view 3D images with full-parallax. The angular divergence in horizontal axis and vertical axis was 1.5 degrees, and 1.25 degrees, respectively, slightly larger than the simulated value of 1.2 degrees by Finite Difference Time Domain (FDTD). The intensity variation was less than 10% for each viewpoint, in consistency with the simulation results. On top of each phase plate, a high-resolution binary masking pattern containing amplitude information of all viewing zone was well aligned. We achieved a resolution of 400 pixels/inch and a viewing angle of 40 degrees for 9-view 3D images with horizontal parallax. In another prototype, the resolution of each view was 160 pixels/inch and the view angle was 50 degrees for 64-view 3D images with full parallax. As demonstrated in the experiments, the homemade lithography system provided the key fabricating technology for multiview 3D holographic display.

Fabrication et applications des reseaux de Bragg ultra-longs

NASA Astrophysics Data System (ADS)

Gagne, Mathieu

This thesis presents the principal accomplishments realized during the PhD project. The thesis is presented by publication format and is a collection of four published articles having fiber Bragg gratings as a central theme. First achieved in 1978, UV writing of fiber Bragg gratings is nowadays a common and mature technology being present in both industry and academia. The property of reflecting light guided by optical fibers lead to diverse applications in telecommunication, lasers as well as several types of sensors. The conventional fabrication technique is generally based on the use of generally expensive phase masks which determine the obtained characteristics of the fiber Bragg grating. The fiber being photosensitive at those wavelengths, a periodic pattern can be written into it. The maximal length, the period, the chirp, the index contrast and the apodisation are all characteristics that depend on the phase mask. The first objective of the research project is to be able to go beyond this strong dependance on the phase mask without deteriorating grating quality. This is what really sets apart the technique presented in this thesis from other long fiber Bragg grating fabrication techniques available in the literature. The fundamental approach to obtain ultra long fiber Bragg gratings of arbitrary profile is to replace the scheme of scanning a UV beam across a phase mask to expose a fixed fiber by a scheme where the UV beam and phase mask are fixed and where the fiber is moving instead. To obtain a periodic index variation, the interference pattern itself must be synchronized with the moving fiber. Two variations of this scheme were implanted: the first one using electro-optical phase modulator placed in each arm of a Talbot interferometer and the second one using a phase mask mounted on a piezo electric actuator. A new scheme that imparts fine movements of the interferometer is also implemented for the first time and showed to be essential to achieve high quality ultra long fiber Bragg gratings. High quality theory matching ultra long fiber Bragg gratings up to 1 meter long are obtained for the first time. The possibility of fabricating high quality ultra long fiber Bragg grating of more than 10 cm (approximately the maximal phase mask length) opens a variety of new applications otherwise impossible with short fiber Bragg grating technology. Ultra long fiber Bragg gratings have unique characteristics such as high reflectivity, high dispersion and ultra narrow bandwidth. Those characteristics can be used to do advanced signal processing, non linear propagation experiments, distributed feedback fiber lasers and dispersion compensator for telecommunication or optical tomography. The second objective of this project is to use these ultra-long fiber Bragg gratings as an optical cavity for fiber lasers. Alot of research in the past years have been concentrated on those lasers, particularly on distributed feedback fiber lasers where the gratings spans all the gain media. A new random fiber laser configuration is presented. It is based on passive or active insertion of phase shifts along the Bragg grating to obtained a phenomenon called light localization which is the optical equivalent of Anderson localization. This complex wave phenomenon has the unique property to mimic the reflection of a uniform photonic crystal with the random diffusion of light among the elements of a random media. Being commonly obtained in fine powders which must respect a certain set of rules, the realization of 1D structures is vastly simplified in optical fibers. Two random fiber laser schemes based on light localization, one using erbium dopant and the other one Raman scattering, are demonstrated for the first time and compared to traditional distributed feedback fiber lasers.

Inverse design of near unity efficiency perfectly vertical grating couplers

NASA Astrophysics Data System (ADS)

Michaels, Andrew; Yablonovitch, Eli

2018-02-01

Efficient coupling between integrated optical waveguides and optical fibers is essential to the success of integrated photonics. While many solutions exist, perfectly vertical grating couplers which scatter light out of a waveguide in the direction normal to the waveguide's top surface are an ideal candidate due to their potential to reduce packaging complexity. Designing such couplers with high efficiency, however, has proven difficult. In this paper, we use electromagnetic inverse design techniques to optimize a high efficiency two-layer perfectly vertical silicon grating coupler. Our base design achieves a chip-to-fiber coupling efficiency of over 99% (-0.04 dB) at 1550 nm. Using this base design, we apply subsequent constrained optimizations to achieve vertical couplers with over 96% efficiency which are fabricable using a 65 nm process.

High-contrast grating hollow-core waveguide splitter applied to optical phased array

NASA Astrophysics Data System (ADS)

Zhao, Che; Xue, Ping; Zhang, Hanxing; Chen, Te; Peng, Chao; Hu, Weiwei

2014-11-01

A novel hollow-core (HW) Y-branch waveguide splitter based on high-contrast grating (HCG) is presented. We calculated and designed the HCG-HW splitter using Rigorous Coupled Wave Analysis (RCWA). Finite-different timedomain (FDTD) simulation shows that the splitter has a broad bandwidth and the branching loss is as low as 0.23 dB. Fabrication is accomplished with standard Silicon-On-Insulator (SOI) process. The experimental measurement results indicate its good performance on beam splitting near the central wavelength λ = 1550 nm with a total insertion loss of 7.0 dB.

Ultra-long-period grating as a novel tool for multi-wavelength ultrafast photonics

NASA Astrophysics Data System (ADS)

Guo, Bo; Yang, Wen-Lei

2017-10-01

Here, we demonstrate the six-wavelength mode-locking and hybrid mode-locking operation in an erbium-doped fiber laser (EDFL) with an ultra-long-period grating (ULPG) by properly adjusting the pump power and the cavity parameters. The ULPG is fabricated by using the fused biconical method with a GPX-3000 glass processing system. Study found that, the ULPG exhibits dual-function, that is, mode-locker and multiwavelength filter. Our finding implies that apart from its fantastic sensing application, the ULPG may also possess attractive nonlinear optical property for ultrafast photonics.

Tailored Fano resonance and localized electromagnetic field enhancement in Ag gratings

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Zhaozhu; Klopf, J. Michael; Wang, Lei

Metallic gratings can support Fano resonances when illuminated with EM radiation, and their characteristic reflectivity versus incident angle lineshape can be greatly affected by the surrounding dielectric environment and the grating geometry. By using conformal oblique incidence thin film deposition onto an optical grating substrate, it is possible to increase the grating amplitude due to shadowing effects, thereby enabling tailoring of the damping processes and electromagnetic field couplings of the Fano resonances, hence optimizing the associated localized electric field intensity. To investigate these effects we compare the optical reflectivity under resonance excitation in samples prepared by oblique angle deposition (OAD)more » and under normal deposition (ND) onto the same patterned surfaces. We observe that by applying OAD method, the sample exhibits a deeper and narrower reflectivity dip at resonance than that obtained under ND. This can be explained in terms of a lower damping of Fano resonance on obliquely deposited sample and leads to a stronger localized electric field. This approach opens a fabrication path for applications where tailoring the electromagnetic field induced by Fano resonance can improve the figure of merit of specific device characteristics, e.g. quantum efficiency (QE) in grating-based metallic photocathodes.« less

Tailored Fano resonance and localized electromagnetic field enhancement in Ag gratings

DOE PAGES

Li, Zhaozhu; Klopf, J. Michael; Wang, Lei; ...

2017-03-14

Metallic gratings can support Fano resonances when illuminated with EM radiation, and their characteristic reflectivity versus incident angle lineshape can be greatly affected by the surrounding dielectric environment and the grating geometry. By using conformal oblique incidence thin film deposition onto an optical grating substrate, it is possible to increase the grating amplitude due to shadowing effects, thereby enabling tailoring of the damping processes and electromagnetic field couplings of the Fano resonances, hence optimizing the associated localized electric field intensity. To investigate these effects we compare the optical reflectivity under resonance excitation in samples prepared by oblique angle deposition (OAD)more » and under normal deposition (ND) onto the same patterned surfaces. We observe that by applying OAD method, the sample exhibits a deeper and narrower reflectivity dip at resonance than that obtained under ND. This can be explained in terms of a lower damping of Fano resonance on obliquely deposited sample and leads to a stronger localized electric field. This approach opens a fabrication path for applications where tailoring the electromagnetic field induced by Fano resonance can improve the figure of merit of specific device characteristics, e.g. quantum efficiency (QE) in grating-based metallic photocathodes.« less

Stimulated Brillouin scattering in ultra-long distributed feedback Bragg gratings in standard optical fiber.

PubMed

Loranger, Sébastien; Lambin-Iezzi, Victor; Wahbeh, Mamoun; Kashyap, Raman

2016-04-15

Distributed feedback (DFB) fiber Bragg gratings (FBG) are widely used as narrow-band filters and single-mode cavities for lasers. Recently, a nonlinear generation has been shown in 10-20 cm DFB gratings in a highly nonlinear fiber. First, we show in this Letter a novel fabrication technique of ultra-long DFBs in a standard fiber (SMF-28). Second, we demonstrate nonlinear generation in such gratings. A particular inscription technique was used to fabricate all-in-phase ultra-long FBG and to implement reproducible phase shift to form a DFB mode. We demonstrate stimulated Brillouin scattering (SBS) emission from this DFB mode and characterize the resulting laser. It seems that such a SBS based DFB laser stabilizes a pump's jittering and reduces its linewidth.

Cylinder and metal grating polarization beam splitter

NASA Astrophysics Data System (ADS)

Yang, Junbo; Xu, Suzhi

2017-08-01

We propose a novel and compact metal grating polarization beam splitter (PBS) based on its different reflected and transmitted orders. The metal grating exhibits a broadband high reflectivity and polarization dependence. The rigorous coupled wave analysis is used to calculate the reflectivity and the transmitting spectra and optimize the structure parameters to realize the broadband PBS. The finite-element method is used to calculate the field distribution. The characteristics of the broadband high reflectivity, transmitting and the polarization dependence are investigated including wavelength, period, refractive index and the radius of circle grating. When grating period d = 400 nm, incident wavelength λ = 441 nm, incident angle θ = 60° and radius of circle d/5, then the zeroth reflection order R0 = 0.35 and the transmission zeroth order T0 = 0.08 for TE polarization, however, T0 = 0.34 and R0 = 0.01 for TM mode. The simple fabrication method involves only single etch step and good compatibility with complementary metal oxide semiconductor technology. PBS designed here is particularly suited for optical communication and optical information processing.

Steering and filtering white light with resonant waveguide gratings

NASA Astrophysics Data System (ADS)

Quaranta, Giorgio; Basset, Guillaume; Martin, Olivier J. F.; Gallinet, Benjamin

2017-08-01

A novel thin-film single-layer structure based on resonant waveguide gratings (RWGs) allows to engineer selective color filtering and steering of white light. The unit cell of the structure consists of two adjacent finite-length and cross-talking RWGs, where the former acts as in-coupler and the latter acts as out-coupler. The structure is made by only one nano-imprint lithography replication and one thin film layer deposition, making it fully compatible with up-scalable fabrication processes. We characterize a fabricated optical security element designed to work with the flash and the camera of a smartphone in off-axis light steering configuration, where the pattern is revealed only by placing the smartphone in the proper position. Widespread applications are foreseen in a variety of fields, such as multifocal or monochromatic lenses, solar cells, biosensors, security devices and seethrough optical combiners for near-eye displays.

Spatial light modulator array with heat minimization and image enhancement features

DOEpatents

Jain, Kanti [Briarcliff Manor, NY; Sweatt, William C [Albuquerque, NM; Zemel, Marc [New Rochelle, NY

2007-01-30

An enhanced spatial light modulator (ESLM) array, a microelectronics patterning system and a projection display system using such an ESLM for heat-minimization and resolution enhancement during imaging, and the method for fabricating such an ESLM array. The ESLM array includes, in each individual pixel element, a small pixel mirror (reflective region) and a much larger pixel surround. Each pixel surround includes diffraction-grating regions and resolution-enhancement regions. During imaging, a selected pixel mirror reflects a selected-pixel beamlet into the capture angle of a projection lens, while the diffraction grating of the pixel surround redirects heat-producing unused radiation away from the projection lens. The resolution-enhancement regions of selected pixels provide phase shifts that increase effective modulation-transfer function in imaging. All of the non-selected pixel surrounds redirect all radiation energy away from the projection lens. All elements of the ESLM are fabricated by deposition, patterning, etching and other microelectronic process technologies.

Sensing characteristics of long period gratings in hollow core fiber fabricated via electrode arc discharge

NASA Astrophysics Data System (ADS)

Iadicicco, Agostino; Cutolo, A.; Campopiano, Stefania

2014-05-01

This paper reports on the fabrication of Long Period Gratings (LPGs) in hollow-core air-silica photonic bandgap fibers (HC-PCFs) by using pressure assisted Electrode Arc Discharge (EAD) technique. In particular, the fabrication procedure relies on the combined use of EAD step, to locally heat the HC fiber, and of a static pressure (slightly higher than the external one) inside the fiber holes, to modify the holes. Here, the experimental fabrication of LPG prototypes with different periods and lengths are discussed. And, the sensitivity of LPGs in HC-PCF to environmental parameters such as strain, temperature and static pressure are presented and discussed.

Soft X-ray holographic grating beam splitter including a double frequency grating for interferometer pre-alignment.

PubMed

Liu, Ying; Tan, Xin; Liu, Zhengkun; Xu, Xiangdong; Hong, Yilin; Fu, Shaojun

2008-09-15

Grating beam splitters have been fabricated for soft X-ray Mach- Zehnder interferometer using holographic interference lithography. The grating beam splitter consists of two gratings, one works at X-ray laser wavelength of 13.9 nm with the spatial frequency of 1000 lines/mm as the operation grating, the other works at visible wavelength of 632.8 nm for pre-aligning the X-ray interferometer with the spatial frequency of 22 lines/mm as the pre-alignment grating. The two gratings lie vertically on the same substrate. The main feature of the beam splitter is the use of low-spatial- frequency beat grating of a holographic double frequency grating as the pre-alignment grating of the X-ray interferometer. The grating line parallelism between the two gratings can be judged by observing the diffraction patterns of the pre-alignment grating directly.

Highly angular dependent high-contrast grating mirror and its application for transverse-mode control of VCSELs

NASA Astrophysics Data System (ADS)

Inoue, Shunya; Kashino, Junichi; Matsutani, Akihiro; Ohtsuki, Hideo; Miyashita, Takahiro; Koyama, Fumio

2014-09-01

We report on the design and fabrication of a highly angular dependent high contrast grating (HCG) mirror. The modeling and experiment on amorphous-Si/SiO2 HCG clearly show the large angular dependence of reflectivity, which enables single transverse-mode operations of large-area VCSELs. We fabricate 980 nm VCSELs with the angular dependent HCG functioning as a spatial frequency filter. We obtained the single transverse mode operation of the fabricated device in contrast to conventional VCSELs with semiconductor multilayer mirrors.

Grating-coupled surface plasmon enhanced short-circuit current in organic thin-film photovoltaic cells.

PubMed

Baba, Akira; Aoki, Nobutaka; Shinbo, Kazunari; Kato, Keizo; Kaneko, Futao

2011-06-01

In this study, we demonstrate the fabrication of grating-coupled surface plasmon resonance (SPR) enhanced organic thin-film photovoltaic cells and their improved photocurrent properties. The cell consists of a grating substrate/silver/P3HT:PCBM/PEDOT:PSS structure. Blu-ray disk recordable substrates are used as the diffraction grating substrates on which silver films are deposited by vacuum evaporation. P3HT:PCBM films are spin-coated on silver/grating substrates. Low conductivity PEDOT:PSS/PDADMAC layer-by-layer ultrathin films deposited on P3HT:PCBM films act as the hole transport layer, whereas high conductivity PEDOT:PSS films deposited by spin-coating act as the anode. SPR excitations are observed in the fabricated cells upon irradiation with white light. Up to a 2-fold increase in the short-circuit photocurrent is observed when the surface plasmon (SP) is excited on the silver gratings as compared to that without SP excitation. The finite-difference time-domain simulation indicates that the electric field in the P3HT:PCBM layer can be increased using the grating-coupled SP technique. © 2011 American Chemical Society

Fabrication of large area plasmonic nanoparticle grating structure on silver halide based transmission electron microscope film and its application as a surface enhanced Raman spectroscopy substrate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sudheer,, E-mail: sudheer@rrcat.gov.in; Tiwari, P.; Singh, M. N.

The plasmonic responses of silver nanoparticle grating structures of different periods made on silver halide based electron microscope film are investigated. Raster scan of the conventional scanning electron microscope (SEM) is used to carry out electron beam lithography for fabricating the plasmonic nanoparticle grating (PNG) structures. Morphological characterization of the PNG structures, carried out by the SEM and the atomic force microscope, indicates that the depth of the groove decreases with a decrease in the grating period. Elemental characterization performed by the energy dispersive spectroscopy and the x-ray diffraction shows the presence of nanoparticles of silver in the PNG grating.more » The optical characterization of the gratings shows that the localized surface plasmon resonance peak shifts from 366 to 378 nm and broadens with a decrease in grating period from 10 to 2.5 μm. The surface enhanced Raman spectroscopy of the Rhodamine-6G dye coated PNG structure shows the maximum enhancement by two orders of magnitude in comparison to the randomly distributed silver nanoparticles having similar size and shape as the PNG structure.« less

Optical temperature sensing on flexible polymer foils

NASA Astrophysics Data System (ADS)

Sherman, Stanislav; Xiao, Yanfen; Hofmann, Meike; Schmidt, Thomas; Gleissner, Uwe; Zappe, Hans

2016-04-01

In contrast to established semiconductor waveguide-based or glass fiber-based integrated optical sensors, polymerbased optical systems offer tunable material properties, such as refractive index or viscosity, and thus provide additional degrees of freedom for sensor design and fabrication. Of particular interest in sensing applications are fully-integrated optical waveguide-based temperature sensors. These typically rely on Bragg gratings which induce a periodic refractive index variation in the waveguide so that a resonant wavelength of the structure is reflected.1,2 With broad-band excitation, a dip in the spectral output of the waveguide is thus generated at a precisely-defined wavelength. This resonant wavelength depends on the refractive index of the waveguide and the grating period, yet both of these quantities are temperature dependent by means of the thermo-optic effect (change in refractive index with temperature) and thermal expansion (change of the grating period with temperature). We show the design and fabrication of polymer waveguide-integrated temperature sensors based on Bragggratings, fabricated by replication technology on flexible PMMA foil substrates. The 175 μm thick foil serves as lower cladding for a polymeric waveguide fabricated from a custom-made UV-crosslinkable co-monomer composition. The fabrication of the grating structure includes a second replication step into a separate PMMA-foil. The dimensions of the Bragg-gratings are determined by simulations to set the bias point into the near infrared wavelength range, which allows Si-based detectors to be used. We present design considerations and performance data for the developed structures. The resulting sensor's signal is linear to temperature changes and shows a sensitivity of -306 nm/K, allowing high resolution temperature measurements.

Extended asymmetric-cut multilayer X-ray gratings.

PubMed

Prasciolu, Mauro; Haase, Anton; Scholze, Frank; Chapman, Henry N; Bajt, Saša

2015-06-15

The fabrication and characterization of a large-area high-dispersion blazed grating for soft X-rays based on an asymmetric-cut multilayer structure is reported. An asymmetric-cut multilayer structure acts as a perfect blazed grating of high efficiency that exhibits a single diffracted order, as described by dynamical diffraction throughout the depth of the layered structure. The maximum number of grating periods created by cutting a multilayer deposited on a flat substrate is equal to the number of layers deposited, which limits the size of the grating. The size limitation was overcome by depositing the multilayer onto a substrate which itself is a coarse blazed grating and then polish it flat to reveal the uniformly spaced layers of the multilayer. The number of deposited layers required is such that the multilayer thickness exceeds the step height of the substrate structure. The method is demonstrated by fabricating a 27,060 line pairs per mm blazed grating (36.95 nm period) that is repeated every 3,200 periods by the 120-μm period substrate structure. This preparation technique also relaxes the requirements on stress control and interface roughness of the multilayer film. The dispersion and efficiency of the grating is demonstrated for soft X-rays of 13.2 nm wavelength.

Wideband two-port beam splitter of a binary fused-silica phase grating.

PubMed

Wang, Bo; Zhou, Changhe; Feng, Jijun; Ru, Huayi; Zheng, Jiangjun

2008-08-01

The usual beam splitter of multilayer-coated film with a wideband spectrum is not easy to achieve. We describe the realization of a wideband transmission two-port beam splitter based on a binary fused-silica phase grating. To achieve high efficiency and equality in the diffracted 0th and -1st orders, the grating profile parameters are optimized using rigorous coupled-wave analysis at a wavelength of 1550 nm. Holographic recording and the inductively coupled plasma dry etching technique are used to fabricate the fused-silica beam splitter grating. The measured efficiency of (45% x 2) = 90% diffracted into the both orders can be obtained with the fabricated grating under Littrow mounting. The physical mechanism of such a wideband two-port beam splitter grating can be well explained by the modal method based on two-beam interference of the modes excited by the incident wave. With the high damage threshold, low coefficient of thermal expansion, and wideband high efficiency, the presented beam splitter etched in fused silica should be a useful optical element for a variety of practical applications.

Fabrication of SiC membrane HCG blue reflector using nanoimprint lithography

NASA Astrophysics Data System (ADS)

Lai, Ying-Yu; Matsutani, Akihiro; Lu, Tien-Chang; Wang, Shing-Chung; Koyama, Fumio

2015-02-01

We designed and fabricated a suspended SiC-based membrane high contrast grating (HCG) reflectors. The rigorous coupled-wave analysis (RCWA) was employed to verify the structural parameters including grating periods, grating height, filling factors and air-gap height. From the optimized simulation results, the designed SiC-based membrane HCG has a wide reflection stopband (reflectivity (R) <90%) of 135 nm for the TE polarization, which centered at 480 nm. The suspended SiC-based membrane HCG reflectors were fabricated by nanoimprint lithography and two-step etching technique. The corresponding reflectivity was measured by using a micro-reflectivity spectrometer. The experimental results show a high reflectivity (R<90%), which is in good agreement with simulation results. This achievement should have an impact on numerous III-N based photonic devices operating in the blue wavelength or even ultraviolet region.

Technological processes of grating light valve as diffractive spatial light modulator in laser phototypesetting system

NASA Astrophysics Data System (ADS)

Zhang, Wei; Geng, Yu; Hou, Changlun; Yang, Guoguang; Bai, Jian

2008-11-01

Grating Light Valve (GLV) is a kind of optics device based on Micro-Opto-Electro-Mechanical System (MOEMS) technology, utilizing diffraction principle to switch, attenuate and modulate light. In this paper, traditional GLV device's structure and its working principle are illuminated, and a kind of modified GLV structure is presented, with details introduction of the fabrication technology. The GLV structure includes single crystal silicon substrate, silicon dioxide isolating layer, aluminum layer of fixed ribbons and silicon nitride of movable ribbons. In the fabrication, lots of techniques are adopted, such as low-pressure chemical vapor deposition (LPCVD), photolithography, etching and evaporation. During the fabrication processes, Photolithography is a fundamental and fatal technology, which determines etching result and GLV quality. Some methods are proposed through repeated experiments, to improve etching result greatly and guide the practical application. This kind of GLV device can be made both small and inexpensively, and has been tested to show proper range of actuation under DC bias, with good performance. The GLV device also has merits such as low cost, simple technology, high fill ratio and low driving voltage. It can properly be well used and match the demands of high light power needed in laser phototypesetting system, as a high-speed, high-resolution light modulator.

A novel method for fabrication of continuous-relief optical elements

NASA Astrophysics Data System (ADS)

Guo, Xiaowei; Du, Jinglei; Chen, Mingyong; Ma, Yanqin; Zhu, Jianhua; Peng, Qinjun; Guo, Yongkang; Du, Chunlei

2005-08-01

A novel method for the fabrication of continuous micro-optical components is presented in this paper. It employs a computer controlled spatial-light-modulator (SLM) as a switchable projection mask and silver-halide sensitized gelatin (SHSG) as recording material. By etching SHSG with enzyme solution, the micro-optical components with relief modulation can be generated through special processing procedures. The principles of digital SLM-based lithography and enzyme etching SHSG are discussed in detail, and microlens arrays, micro axicon-lens arrays and gratings with good profile were achieved. This method is simple, cheap and the aberration in processing procedures can be in-situ corrected in the step of designing mask, so it is a practical method to fabricate continuous profile for low-volume production.

Active phase correction of high resolution silicon photonic arrayed waveguide gratings

DOE PAGES

Gehl, M.; Trotter, D.; Starbuck, A.; ...

2017-03-10

Arrayed waveguide gratings provide flexible spectral filtering functionality for integrated photonic applications. Achieving narrow channel spacing requires long optical path lengths which can greatly increase the footprint of devices. High index contrast waveguides, such as those fabricated in silicon-on-insulator wafers, allow tight waveguide bends which can be used to create much more compact designs. Both the long optical path lengths and the high index contrast contribute to significant optical phase error as light propagates through the device. Thus, silicon photonic arrayed waveguide gratings require active or passive phase correction following fabrication. We present the design and fabrication of compact siliconmore » photonic arrayed waveguide gratings with channel spacings of 50, 10 and 1 GHz. The largest device, with 11 channels of 1 GHz spacing, has a footprint of only 1.1 cm 2. Using integrated thermo-optic phase shifters, the phase error is actively corrected. We present two methods of phase error correction and demonstrate state-of-the-art cross-talk performance for high index contrast arrayed waveguide gratings. As a demonstration of possible applications, we perform RF channelization with 1 GHz resolution. In addition, we generate unique spectral filters by applying non-zero phase offsets calculated by the Gerchberg Saxton algorithm.« less

Active phase correction of high resolution silicon photonic arrayed waveguide gratings.

PubMed

Gehl, M; Trotter, D; Starbuck, A; Pomerene, A; Lentine, A L; DeRose, C

2017-03-20

Arrayed waveguide gratings provide flexible spectral filtering functionality for integrated photonic applications. Achieving narrow channel spacing requires long optical path lengths which can greatly increase the footprint of devices. High index contrast waveguides, such as those fabricated in silicon-on-insulator wafers, allow tight waveguide bends which can be used to create much more compact designs. Both the long optical path lengths and the high index contrast contribute to significant optical phase error as light propagates through the device. Therefore, silicon photonic arrayed waveguide gratings require active or passive phase correction following fabrication. Here we present the design and fabrication of compact silicon photonic arrayed waveguide gratings with channel spacings of 50, 10 and 1 GHz. The largest device, with 11 channels of 1 GHz spacing, has a footprint of only 1.1 cm². Using integrated thermo-optic phase shifters, the phase error is actively corrected. We present two methods of phase error correction and demonstrate state-of-the-art cross-talk performance for high index contrast arrayed waveguide gratings. As a demonstration of possible applications, we perform RF channelization with 1 GHz resolution. Additionally, we generate unique spectral filters by applying non-zero phase offsets calculated by the Gerchberg Saxton algorithm.

Parameter-tolerant design of high contrast gratings

NASA Astrophysics Data System (ADS)

Chevallier, Christyves; Fressengeas, Nicolas; Jacquet, Joel; Almuneau, Guilhem; Laaroussi, Youness; Gauthier-Lafaye, Olivier; Cerutti, Laurent; Genty, Frédéric

2015-02-01

This work is devoted to the design of high contrast grating mirrors taking into account the technological constraints and tolerance of fabrication. First, a global optimization algorithm has been combined to a numerical analysis of grating structures (RCWA) to automatically design HCG mirrors. Then, the tolerances of the grating dimensions have been precisely studied to develop a robust optimization algorithm with which high contrast gratings, exhibiting not only a high efficiency but also large tolerance values, could be designed. Finally, several structures integrating previously designed HCGs has been simulated to validate and illustrate the interest of such gratings.

Numerical Approach to Modeling and Characterization of Refractive Index Changes for a Long-Period Fiber Grating Fabricated by Femtosecond Laser

PubMed Central

Saad, Akram; Cho, Yonghyun; Ahmed, Farid; Jun, Martin Byung-Guk

2016-01-01

A 3D finite element model constructed to predict the intensity-dependent refractive index profile induced by femtosecond laser radiation is presented. A fiber core irradiated by a pulsed laser is modeled as a cylinder subject to predefined boundary conditions using COMSOL5.2 Multiphysics commercial package. The numerically obtained refractive index change is used to numerically design and experimentally fabricate long-period fiber grating (LPFG) in pure silica core single-mode fiber employing identical laser conditions. To reduce the high computational requirements, the beam envelope method approach is utilized in the aforementioned numerical models. The number of periods, grating length, and grating period considered in this work are numerically quantified. The numerically obtained spectral growth of the modeled LPFG seems to be consistent with the transmission of the experimentally fabricated LPFG single mode fiber. The sensing capabilities of the modeled LPFG are tested by varying the refractive index of the surrounding medium. The numerically obtained spectrum corresponding to the varied refractive index shows good agreement with the experimental findings. PMID:28774060

Numerical Approach to Modeling and Characterization of Refractive Index Changes for a Long-Period Fiber Grating Fabricated by Femtosecond Laser.

PubMed

Saad, Akram; Cho, Yonghyun; Ahmed, Farid; Jun, Martin Byung-Guk

2016-11-21

A 3D finite element model constructed to predict the intensity-dependent refractive index profile induced by femtosecond laser radiation is presented. A fiber core irradiated by a pulsed laser is modeled as a cylinder subject to predefined boundary conditions using COMSOL5.2 Multiphysics commercial package. The numerically obtained refractive index change is used to numerically design and experimentally fabricate long-period fiber grating (LPFG) in pure silica core single-mode fiber employing identical laser conditions. To reduce the high computational requirements, the beam envelope method approach is utilized in the aforementioned numerical models. The number of periods, grating length, and grating period considered in this work are numerically quantified. The numerically obtained spectral growth of the modeled LPFG seems to be consistent with the transmission of the experimentally fabricated LPFG single mode fiber. The sensing capabilities of the modeled LPFG are tested by varying the refractive index of the surrounding medium. The numerically obtained spectrum corresponding to the varied refractive index shows good agreement with the experimental findings.

Nano-optomechanical characterization of surface-plasmon-based tunable filter integrated with comb-drive actuator

NASA Astrophysics Data System (ADS)

Honma, H.; Mitsudome, M.; Ishida, M.; Sawada, K.; Takahashi, K.

2017-03-01

We report a tunable plasmonic color filter consisting of a metamaterial periodic grating and microelectromechanical systems (MEMS) actuator. An aluminum subwavelength grating is integrated with electrostatic comb-drive actuators to expand the metal subwavelength period, which allows continuous control of the excitation wavelength of surface plasmons (SPs). We develop a batch fabrication process by employing a liftoff technique using an electron beam resist altered by the electron dose depending on different aspect ratios (length/width) for various components such as the subwavelength grating, nanohinge flexural suspensions, and comb fingers. We successfully demonstrate a continuous shift in the excitation wavelength over the 514-635 nm range by nanopitch expansion. The design margin of the grating period for SP excitation is evaluated by comparing the experimental pitch variation and theoretically calculated values. The resonance frequency of the tunable filter is optically measured to be approximately 10 kHz. The optically and mechanically obtained values agree well with the theory of electrostatic actuation and finite-difference time-domain simulation.

Lipid Multilayer Grating Arrays Integrated by Nanointaglio for Vapor Sensing by an Optical Nose

PubMed Central

Lowry, Troy W.; Prommapan, Plengchart; Rainer, Quinn; Van Winkle, David; Lenhert, Steven

2015-01-01

Lipid multilayer gratings are recently invented nanomechanical sensor elements that are capable of transducing molecular binding to fluid lipid multilayers into optical signals in a label free manner due to shape changes in the lipid nanostructures. Here, we show that nanointaglio is suitable for the integration of chemically different lipid multilayer gratings into a sensor array capable of distinguishing vapors by means of an optical nose. Sensor arrays composed of six different lipid formulations are integrated onto a surface and their optical response to three different vapors (water, ethanol and acetone) in air as well as pH under water is monitored as a function of time. Principal component analysis of the array response results in distinct clustering indicating the suitability of the arrays for distinguishing these analytes. Importantly, the nanointaglio process used here is capable of producing lipid gratings out of different materials with sufficiently uniform heights for the fabrication of an optical nose. PMID:26308001

Multi-parameter optimization of monolithic high-index contrast grating reflectors

NASA Astrophysics Data System (ADS)

Marciniak, Magdalena; Gebski, Marcin; Dems, Maciej; Wasiak, Michał; Czyszanowski, Tomasz

2016-03-01

Conventional High-index Contrast Gratings (HCG) consist of periodically distributed high refractive index stripes surrounded by low index media. Practically, such low/high index stack can be fabricated in several ways however low refractive index layers are electrical insulators of poor thermal conductivities. Monolithic High-index Contrast Gratings (MHCGs) overcome those limitations since they can be implemented in any material with a real refractive index larger than 1.75 without the need of the combination of low and high refractive index materials. The freedom of use of various materials allows to provide more efficient current injection and better heat flow through the mirror, in contrary to the conventional HCGs. MHCGs can simplify the construction of VCSELs, reducing their epitaxial design to monolithic wafer with carrier confinement and active region inside and etched stripes on both surfaces in post processing. We present numerical analysis of MHCGs using a three-dimensional, fully vectorial optical model. We investigate possible designs of MHCGs using multidimensional optimization of grating parameters for different refractive indices.

60-nm-thick basic photonic components and Bragg gratings on the silicon-on-insulator platform.

PubMed

Zou, Zhi; Zhou, Linjie; Li, Xinwan; Chen, Jianping

2015-08-10

We demonstrate integrated basic photonic components and Bragg gratings using 60-nm-thick silicon-on-insulator strip waveguides. The ultra-thin waveguides exhibit a propagation loss of 0.61 dB/cm and a bending loss of approximately 0.015 dB/180° with a 30 μm bending radius (including two straight-bend waveguide junctions). Basic structures based on the ultra-thin waveguides, including micro-ring resonators, 1 × 2 MMI couplers, and Mach-Zehnder interferometers are realized. Upon thinning-down, the waveguide effective refractive index is reduced, making the fabrication of Bragg gratings possible using the standard 248-nm deep ultra-violet (DUV) photolithography process. The Bragg grating exhibits a stopband width of 1 nm and an extinction ratio of 35 dB, which is practically applicable as an optical filter or a delay line. The transmission spectrum can be thermally tuned via an integrated resistive micro-heater formed by a heavily doped silicon slab beside the waveguide.

Demountable connection for polymer optical fiber grating sensors

NASA Astrophysics Data System (ADS)

Abang, Ada; Webb, David J.

2012-08-01

The authors fabricated a demountable Ferrule connector/Physical contact connection between silica fiber and a polymer optical fiber (POF) containing a fiber Bragg grating. The use of a connector for POF grating sensors eliminates the limitations of ultraviolet glued connections and increases the ease with which the devices can be applied to real-world measurement tasks.

[Integration design and diffraction characteristics analysis of prism-grating-prism].

PubMed

He, Tian-Bo; Bayanheshig; Li, Wen-Hao; Kong, Peng; Tang, Yu-Guo

2014-01-01

Prism-grating-prism (PGP) module is the important dispersing component in the hyper spectral imager. In order to effectively predict the distribution of diffraction efficiency of the whole PGP component and its diffraction characteristics before fabrication, a method of the PGP integration design is proposed. From the point of view of the volume phase holographic grating (VPHG) design, combined with the restrictive correlation between the various parameters of prisms and grating, we compiled the analysis software for calculating the whole PGP's diffraction efficiency. Furthermore, the effects of the structure parameters of prisms and grating on the PGP's diffraction characteristics were researched in detail. In particular we discussed the Bragg wavelength shift behaviour of the grating and a broadband PGP spectral component with high diffraction efficiency was designed for the imaging spectrometers. The result of simulation indicated that the spectral bandwidth of the PGP becomes narrower with the dispersion coefficient of prism 1 material decreasing; Bragg wavelength shift characteristics broaden the bandwidth of VPHG both spectrally and angularly, higher angular selectivity is desirable for selection requirements of the prism 1 material, and it can be easily tuned to achieve spectral bandwidth suitable for imaging PGP spectrograph; the vertex angle of prism 1, the film thickness and relative permittivity modulation of the grating have a significant impact on the distribution of PGP's diffraction efficiency, so precision control is necessary when fabrication. The diffraction efficiency of the whole PGP component designed by this method is no less than 50% in the wavelength range from 400 to 1000 nm, the specific design parameters have been given in this paper that have a certain reference value for PGP fabrication.

Robust optimization of a tandem grating solar thermal absorber

NASA Astrophysics Data System (ADS)

Choi, Jongin; Kim, Mingeon; Kang, Kyeonghwan; Lee, Ikjin; Lee, Bong Jae

2018-04-01

Ideal solar thermal absorbers need to have a high value of the spectral absorptance in the broad solar spectrum to utilize the solar radiation effectively. Majority of recent studies about solar thermal absorbers focus on achieving nearly perfect absorption using nanostructures, whose characteristic dimension is smaller than the wavelength of sunlight. However, precise fabrication of such nanostructures is not easy in reality; that is, unavoidable errors always occur to some extent in the dimension of fabricated nanostructures, causing an undesirable deviation of the absorption performance between the designed structure and the actually fabricated one. In order to minimize the variation in the solar absorptance due to the fabrication error, the robust optimization can be performed during the design process. However, the optimization of solar thermal absorber considering all design variables often requires tremendous computational costs to find an optimum combination of design variables with the robustness as well as the high performance. To achieve this goal, we apply the robust optimization using the Kriging method and the genetic algorithm for designing a tandem grating solar absorber. By constructing a surrogate model through the Kriging method, computational cost can be substantially reduced because exact calculation of the performance for every combination of variables is not necessary. Using the surrogate model and the genetic algorithm, we successfully design an effective solar thermal absorber exhibiting a low-level of performance degradation due to the fabrication uncertainty of design variables.

Nanoimprinted polymer lasers with threshold below 100 W/cm2 using mixed-order distributed feedback resonators.

PubMed

Wang, Yue; Tsiminis, Georgios; Kanibolotsky, Alexander L; Skabara, Peter J; Samuel, Ifor D W; Turnbull, Graham A

2013-06-17

Organic semiconductor lasers were fabricated by UV-nanoimprint lithography with thresholds as low as 57 W/cm(2) under 4 ns pulsed operation. The nanoimprinted lasers employed mixed-order distributed feedback resonators, with second-order gratings surrounded by first-order gratings, combined with a light-emitting conjugated polymer. They were pumped by InGaN LEDs to produce green-emitting lasers, with thresholds of 208 W/cm(2) (102 nJ/pulse). These hybrid lasers incorporate a scalable UV-nanoimprint lithography process, compatible with high-performance LEDs, therefore we have demonstrated a coherent, compact, low-cost light source.

New method of writing long-period fiber gratings using high-frequency CO2 laser

NASA Astrophysics Data System (ADS)

Guo, Gao-Ran; Song, Ying; Zhang, Wen-Tao; Jiang, Yue; Li, Fang

2016-11-01

In the paper, the Long period fiber gratings (LPFG) were fabricated in a single-mode fiber using a high frequency CO2 laser system with the point-to-point technique. The experimental setup consists of a CO2 laser controlling system, a focusing system located at a motorized linear stage, a fiber alignment stage, and an optical spectrum analyzer to monitor the transmission spectrum of the LPFG. The period of the LPFG is precisely inscribed by periodically turning on/off the laser shutter while the motorized linear stage is driven to move at a constant speed. The efficiency of fiber writing process is improved.

Gratings for synchrotron and FEL beamlines: a project for the manufacture of ultra-precise gratings at Helmholtz Zentrum Berlin.

PubMed

Siewert, F; Löchel, B; Buchheim, J; Eggenstein, F; Firsov, A; Gwalt, G; Kutz, O; Lemke, St; Nelles, B; Rudolph, I; Schäfers, F; Seliger, T; Senf, F; Sokolov, A; Waberski, Ch; Wolf, J; Zeschke, T; Zizak, I; Follath, R; Arnold, T; Frost, F; Pietag, F; Erko, A

2018-01-01

Blazed gratings are of dedicated interest for the monochromatization of synchrotron radiation when a high photon flux is required, such as, for example, in resonant inelastic X-ray scattering experiments or when the use of laminar gratings is excluded due to too high flux densities and expected damage, for example at free-electron laser beamlines. Their availability became a bottleneck since the decommissioning of the grating manufacture facility at Carl Zeiss in Oberkochen. To resolve this situation a new technological laboratory was established at the Helmholtz Zentrum Berlin, including instrumentation from Carl Zeiss. Besides the upgraded ZEISS equipment, an advanced grating production line has been developed, including a new ultra-precise ruling machine, ion etching technology as well as laser interference lithography. While the old ZEISS ruling machine GTM-6 allows ruling for a grating length up to 170 mm, the new GTM-24 will have the capacity for 600 mm (24 inch) gratings with groove densities between 50 lines mm -1 and 1200 lines mm -1 . A new ion etching machine with a scanning radiofrequency excited ion beam (HF) source allows gratings to be etched into substrates of up to 500 mm length. For a final at-wavelength characterization, a new reflectometer at a new Optics beamline at the BESSY-II storage ring is under operation. This paper reports on the status of the grating fabrication, the measured quality of fabricated items by ex situ and in situ metrology, and future development goals.

Spherical grating spectrometers

NASA Astrophysics Data System (ADS)

O'Donoghue, Darragh; Clemens, J. Christopher

2014-07-01

We describe designs for spectrometers employing convex dispersers. The Offner spectrometer was the first such instrument; it has almost exclusively been employed on satellite platforms, and has had little impact on ground-based instruments. We have learned how to fabricate curved Volume Phase Holographic (VPH) gratings and, in contrast to the planar gratings of traditional spectrometers, describe how such devices can be used in optical/infrared spectrometers designed specifically for curved diffraction gratings. Volume Phase Holographic gratings are highly efficient compared to conventional surface relief gratings; they have become the disperser of choice in optical / NIR spectrometers. The advantage of spectrometers with curved VPH dispersers is the very small number of optical elements used (the simplest comprising a grating and a spherical mirror), as well as illumination of mirrors off axis, resulting in greater efficiency and reduction in size. We describe a "Half Offner" spectrometer, an even simpler version of the Offner spectrometer. We present an entirely novel design, the Spherical Transmission Grating Spectrometer (STGS), and discuss exemplary applications, including a design for a double-beam spectrometer without any requirement for a dichroic. This paradigm change in spectrometer design offers an alternative to all-refractive astronomical spectrometer designs, using expensive, fragile lens elements fabricated from CaF2 or even more exotic materials. The unobscured mirror layout avoids a major drawback of the previous generation of catadioptric spectrometer designs. We describe laboratory measurements of the efficiency and image quality of a curved VPH grating in a STGS design, demonstrating, simultaneously, efficiency comparable to planar VPH gratings along with good image quality. The stage is now set for construction of a prototype instrument with impressive performance.

Investigation of optical information for a single micro grating device combined with MATA by SMart process

NASA Astrophysics Data System (ADS)

Tsai, Chien-Chung; Huang, Yi-Chao; Yang, Tsa-Hsien; Chen, Jen-Chieh

2006-01-01

The concentric circles type and saw-tooth type of micro grating device based upon the diffraction theory are proposed in this study. The geometry dimension of micro optical device is 200 × 200 μm2, the interval of grating is 4 μm, and the depth is 0.75 μm. The Micro Array Thermal Actuator, MATA, is applied to drive the micro grating device, and the pre-elevating structure is designed to lift the micro grating device by the residual stress of polysilicon combined with metal. The micro grating device is fabricated by Surface Micromachining for applications and research technology platform, SMart, common process. The incident ray of He-Ne laser focused by a lens which focal length is 250 mm is applied to be the light source for the experiment, and then analyzes the optical information of the outgoing ray. From the experimental results, the basic optical features are examined based upon the concentric circles type and saw-tooth type of micro grating device, respectively. The outgoing ray angle of central spot is 60° in theory. The measurements are 59.475° for the concentric circles type and 59.88° for the saw-tooth type. The outgoing ray angle of the first stripe is 46.9° in theory, and 46.81° for the concentric circles type and 46.67° for the saw-tooth type are measured from the experiment. The variation of outgoing ray angle is smaller than 1% compared the measurement results with theory of diffraction on the central spot and first stripe characteristics. The work successfully demonstrates the micro grating device with highly accurate performance by the verification of optical information. All of the efforts will be contributed to Controlled Blazed Diffraction micro grating device, CBDMG, and that will be the main device of Integrate Opto-Electronics applied on display to develop in the future.

Design and fabrication of bilayer metallic nanowire polarizers and color filters based on surface plasmon and waveguide mode resonances

NASA Astrophysics Data System (ADS)

Ye, Zhicheng; Zheng, Jun; Zhang, Chenchen; Sun, Shu

2011-12-01

Optical responses in Bi-layer metallic nanowire grating are investigated. There are two kinds of Surface Plasmon resonances: lateral propagating Surface Plasmon waveguide modes excited by the diffraction of the grating which lead to dips in transmission; Surface Plasmon resonance between the slits of the grating, which leads to high extinction ration of TM to TE transmission. With simultaneous resonances, a compacted device of integrated color filter and polarizer can be achieved. In order to improve the transmission of TM light, an undercut structure is proposed. The mechanism of the enhancement is analyzed. Bi-layer metallic nanowire gratings are fabricated by laser interference lithography and subsequent E-beam deposition. The measured transmission and reflection spectra confirmed the theoretical and numerical simulations. The results will have wide potential applications in Displays, Optical communication, and integrated Optics.

Immersion Gratings for Infrared High-resolution Spectroscopy

NASA Astrophysics Data System (ADS)

Sarugaku, Yuki; Ikeda, Yuji; Kobayashi, Naoto; Kaji, Sayumi; Sukegawa, Takashi; Sugiyama, Shigeru; Nakagawa, Takao; Arasaki, Takayuki; Kondo, Sohei; Nakanishi, Kenshi; Yasui, Chikako; Kawakita, Hideyo

2016-10-01

High-resolution spectroscopy in the infrared wavelength range is essential for observations of minor isotopologues, such as HDO for water, and prebiotic organic molecules like hydrocarbons/P-bearing molecules because numerous vibrational molecular bands (including non-polar molecules) are located in this wavelength range. High spectral resolution enables us to detect weak lines without spectral line confusion. This technique has been widely used in planetary sciences, e.g., cometary coma (H2O, CO, and organic molecules), the martian atmosphere (CH4, CO2, H2O and HDO), and the upper atmosphere of gas giants (H3+ and organic molecules such as C2H6). Spectrographs with higher resolution (and higher sensitivity) still have a potential to provide a plenty of findings. However, because the size of spectrographs scales with the spectral resolution, it is difficult to realize it.Immersion grating (IG), which is a diffraction grating wherein the diffraction surface is immersed in a material with a high refractive index (n > 2), provides n times higher spectral resolution compared to a reflective grating of the same size. Because IG reduces the size of spectrograph to 1/n compared to the spectrograph with the same spectral resolution using a conventional reflective grating, it is widely acknowledged as a key optical device to realize compact spectrographs with high spectral resolution.Recently, we succeeded in fabricating a CdZnTe immersion grating with the theoretically predicted diffraction efficiency by machining process using an ultrahigh-precision five-axis processing machine developed by Canon Inc. Using the same technique, we completed a practical germanium (Ge) immersion grating with both a reflection coating on the grating surface and the an AR coating on the entrance surface. It is noteworthy that the wide wavelength range from 2 to 20 um can be covered by the two immersion gratings.In this paper, we present the performances and the applications of the immersion gratings, including the development of a long-NIR (2-5um) high-resolution (R=80,000) spectrograph with Ge-immersion grating, VINROUGE, which is a prototype for the TMT MIR instrument.

Chirped circular dielectric gratings for near-unity collection efficiency from quantum emitters in bulk diamond

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zheng, Jiabao; Liapis, Andreas C.; Chen, Edward H.

Effcient collection of fluorescence from nitrogen vacancy (NV) centers in diamond underlies the spin-dependent optical read-out that is necessary for quantum information processing and enhanced sensing applications. The optical collection effciency from NVs within diamond substrates is limited primarily due to the high refractive index of diamond and the non-directional dipole emission. Here we introduce a light collection strategy based on chirped, circular dielectric gratings that can be fabricated on a bulk diamond substrate to redirect an emitter’s far-field radiation pattern. Using a genetic optimization algorithm, these grating designs achieve 98.9% collection effciency for the NV zero-phonon emission line, collectedmore » from the back surface of the diamond with an objective of aperture 0.9. Across the broadband emission spectrum of the NV (600-800 nm), the chirped grating achieves 82.2% collection e ciency into a numerical aperture of 1.42, corresponding to an oil immersion objective again on the back side of the diamond. Our proposed bulk-dielectric grating structures are applicable to other optically active solid state quantum emitters in high index host materials.« less

Chirped circular dielectric gratings for near-unity collection efficiency from quantum emitters in bulk diamond

DOE PAGES

Zheng, Jiabao; Liapis, Andreas C.; Chen, Edward H.; ...

2017-12-13

Effcient collection of fluorescence from nitrogen vacancy (NV) centers in diamond underlies the spin-dependent optical read-out that is necessary for quantum information processing and enhanced sensing applications. The optical collection effciency from NVs within diamond substrates is limited primarily due to the high refractive index of diamond and the non-directional dipole emission. Here we introduce a light collection strategy based on chirped, circular dielectric gratings that can be fabricated on a bulk diamond substrate to redirect an emitter’s far-field radiation pattern. Using a genetic optimization algorithm, these grating designs achieve 98.9% collection effciency for the NV zero-phonon emission line, collectedmore » from the back surface of the diamond with an objective of aperture 0.9. Across the broadband emission spectrum of the NV (600-800 nm), the chirped grating achieves 82.2% collection e ciency into a numerical aperture of 1.42, corresponding to an oil immersion objective again on the back side of the diamond. Our proposed bulk-dielectric grating structures are applicable to other optically active solid state quantum emitters in high index host materials.« less

Surface holograms for sensing application

NASA Astrophysics Data System (ADS)

Zawadzka, M.; Naydenova, I.

2018-01-01

Surface gratings with periodicity of 2 μm and amplitude in the range of 175 and 240 nm were fabricated in a plasticized polyvinylchloride doped with a metalloporphyrin (ZnTPP), via a single laser pulse holographic ablation process. The effect of the laser pulse energy on the profiles of the fabricated surface structure was investigated. The sensing capabilities of the fabricated diffractive structures towards amines (triethylamine, diethylamine) and pyridine vapours were then explored; the holographic structures were exposed to the analyte vapours and changes in the intensity of the diffracted light were monitored in real time at 473 nm. It was demonstrated that surface structures, fabricated in a polymer doped with a metalloporphyrin which acts as analyte receptor, have a potential in sensing application.

Enhanced Raman scattering in porous silicon grating.

PubMed

Wang, Jiajia; Jia, Zhenhong; Lv, Changwu

2018-03-19

The enhancement of Raman signal on monocrystalline silicon gratings with varying groove depths and on porous silicon grating were studied for a highly sensitive surface enhanced Raman scattering (SERS) response. In the experiment conducted, porous silicon gratings were fabricated. Silver nanoparticles (Ag NPs) were then deposited on the porous silicon grating to enhance the Raman signal of the detective objects. Results show that the enhancement of Raman signal on silicon grating improved when groove depth increased. The enhanced performance of Raman signal on porous silicon grating was also further improved. The Rhodamine SERS response based on Ag NPs/ porous silicon grating substrates was enhanced relative to the SERS response on Ag NPs/ porous silicon substrates. Ag NPs / porous silicon grating SERS substrate system achieved a highly sensitive SERS response due to the coupling of various Raman enhancement factors.

Design and fabrication of a polarization-independent two-port beam splitter.

PubMed

Feng, Jijun; Zhou, Changhe; Zheng, Jiangjun; Cao, Hongchao; Lv, Peng

2009-10-10

We design and manufacture a fused-silica polarization-independent two-port beam splitter grating. The physical mechanism of this deeply etched grating can be shown clearly by using the simplified modal method with consideration of corresponding accumulated phase difference of two excited propagating grating modes, which illustrates that the binary-phase fused-silica grating structure depends little on the incident wavelength, but mainly on the ratio of groove depth to grating period and the ratio of incident wavelength to grating period. These analytic results would also be very helpful for wavelength bandwidth analysis. The exact grating profile is optimized by using the rigorous coupled-wave analysis. Holographic recording technology and inductively coupled plasma etching are used to manufacture the fused-silica grating. Experimental results agree well with the theoretical values.

Dual-function beam splitter of a subwavelength fused-silica grating.

PubMed

Feng, Jijun; Zhou, Changhe; Zheng, Jiangjun; Cao, Hongchao; Lv, Peng

2009-05-10

We present the design and fabrication of a novel dual-function subwavelength fused-silica grating that can be used as a polarization-selective beam splitter. For TM polarization, the grating can be used as a two-port beam splitter at a wavelength of 1550 nm with a total diffraction efficiency of 98%. For TE polarization, the grating can function as a high-efficiency grating, and the diffraction efficiency of the -1st order is 95% under Littrow mounting. This dual-function grating design is based on a simplified modal method. By using the rigorous coupled-wave analysis, the optimum grating parameters can be determined. Holographic recording technology and inductively coupled plasma etching are used to manufacture the fused-silica grating. Experimental results are in agreement with the theoretical values.

Monitoring techniques for the manufacture of tapered optical fibers.

PubMed

Mullaney, Kevin; Correia, Ricardo; Staines, Stephen E; James, Stephen W; Tatam, Ralph P

2015-10-01

The use of a range of optical techniques to monitor the process of fabricating optical fiber tapers is investigated. Thermal imaging was used to optimize the alignment of the optical system; the transmission spectrum of the fiber was monitored to confirm that the tapers had the required optical properties and the strain induced in the fiber during tapering was monitored using in-line optical fiber Bragg gratings. Tapers were fabricated with diameters down to 5 μm and with waist lengths of 20 mm using single-mode SMF-28 fiber.

Polymer planar waveguide Bragg gratings: fabrication, characterization, and sensing applications

NASA Astrophysics Data System (ADS)

Rosenberger, M.; Hessler, S.; Pauer, H.; Girschikofsky, M.; Roth, G. L.; Adelmann, B.; Woern, H.; Schmauss, B.; Hellmann, R.

2017-02-01

In this contribution, we give a comprehensive overview of the fabrication, characterization, and application of integrated planar waveguide Bragg gratings (PPBGs) in cyclo-olefin copolymers (COC). Starting with the measurement of the refractive index depth profile of integrated UV-written structures in COC by phase shifting Mach-Zehnder- Interferometry, we analyze the light propagation using numerical simulations. Furthermore, we show the rapid fabrication of humidity insensitive polymer waveguide Bragg gratings in cyclo-olefin copolymers and discuss the influence of the UV-dosage onto the spectral characteristics and the transmission behavior of the waveguide. Based on these measurements we exemplify that our Bragg gratings exhibit a reflectivity of over 99 % and are highly suitable for sensing applications. With regard to a negligible affinity to absorb water and in conjunction with high temperature stability these polymer devices are ideal for mechanical deformation sensing. Since planar structures are not limited to tensile but can also be applied for measuring compressive strain, we manufacture different functional devices and corroborate their applicability as optical sensors. Exemplarily, we highlight a temperature referenced PPBG sensor written into a femtosecond-laser cut tensile test geometry for tensile and compressive strain sensing. Furthermore, a flexible polymer planar shape sensor is presented.

Experimental verification of the rainbow trapping effect in adiabatic plasmonic gratings

PubMed Central

Gan, Qiaoqiang; Gao, Yongkang; Wagner, Kyle; Vezenov, Dmitri; Ding, Yujie J.; Bartoli, Filbert J.

2011-01-01

We report the experimental observation of a trapped rainbow in adiabatically graded metallic gratings, designed to validate theoretical predictions for this unique plasmonic structure. One-dimensional graded nanogratings were fabricated and their surface dispersion properties tailored by varying the grating groove depth, whose dimensions were confirmed by atomic force microscopy. Tunable plasmonic bandgaps were observed experimentally, and direct optical measurements on graded grating structures show that light of different wavelengths in the 500–700-nm region is “trapped” at different positions along the grating, consistent with computer simulations, thus verifying the “rainbow” trapping effect. PMID:21402936

Surface relief and refractive index gratings patterned in chalcogenide glasses and studied by off-axis digital holography.

PubMed

Cazac, V; Meshalkin, A; Achimova, E; Abashkin, V; Katkovnik, V; Shevkunov, I; Claus, D; Pedrini, G

2018-01-20

Surface relief gratings and refractive index gratings are formed by direct holographic recording in amorphous chalcogenide nanomultilayer structures As 2 S 3 -Se and thin films As 2 S 3 . The evolution of the grating parameters, such as the modulation of refractive index and relief depth in dependence of the holographic exposure, is investigated. Off-axis digital holographic microscopy is applied for the measurement of the photoinduced phase gratings. For the high-accuracy reconstruction of the wavefront (amplitude and phase) transmitted by the fabricated gratings, we used a computational technique based on the sparse modeling of phase and amplitude. Both topography and refractive index maps of recorded gratings are revealed. Their separated contribution in diffraction efficiency is estimated.

Integrated optic head for sensing a two-dimensional displacement of a grating scale

NASA Astrophysics Data System (ADS)

Ura, Shogo; Endoh, Toshiaki; Suhara, Toshiaki; Nishihara, Hiroshi

1996-11-01

An integrated optic sensor head was proposed for sensing a two-dimensional displacement of a scale consisting of crossed gratings. Two interferometers, crossing each other, are constructed by the integration of two pairs of linearly focusing grating couplers (LFGC's) and two pairs of photodiodes (PD's) on a Si substrate. Four beams radiated by the LFGC's from the sensor head overlap on the grating scale, and the beams are diffracted by the grating scale and interfere on the PD's. The period of the interference signal variation is just half of the scale grating period. The device was designed and fabricated with a grating scale of 3.2- mu m period, and the sensing principle was experimentally confirmed.

X-ray verification of an optically aligned off-plane grating module

NASA Astrophysics Data System (ADS)

Donovan, Benjamin D.; McEntaffer, Randall L.; Tutt, James H.; DeRoo, Casey T.; Allured, Ryan; Gaskin, Jessica A.; Kolodziejczak, Jeffery J.

2018-01-01

Off-plane x-ray reflection gratings are theoretically capable of achieving high resolution and high diffraction efficiencies over the soft x-ray bandpass, making them an ideal technology to implement on upcoming x-ray spectroscopy missions. To achieve high effective area, these gratings must be aligned into grating modules. X-ray testing was performed on an aligned grating module to assess the current optical alignment methods. Results indicate that the grating module achieved the desired alignment for an upcoming x-ray spectroscopy suborbital rocket payload with modest effective area and resolving power. These tests have also outlined a pathway towards achieving the stricter alignment tolerances of future x-ray spectrometer payloads, which require improvements in alignment metrology, grating fabrication, and testing techniques.

D-shaped fiber grating refractive index sensor induced by an ultrashort pulse laser.

PubMed

Liao, Changrui; Wang, Qiao; Xu, Lei; Liu, Shen; He, Jun; Zhao, Jing; Li, Zhengyong; Wang, Yiping

2016-03-01

The fabrication of fiber Bragg gratings was here demonstrated using ultrashort pulse laser point-by-point inscription. This is a very convenient means of creating fiber Bragg gratings with different grating periods and works by changing the translation speed of the fiber. The laser energy was first optimized in order to improve the spectral properties of the fiber gratings. Then, fiber Bragg gratings were formed into D-shaped fibers for use as refractive index sensors. A nonlinear relationship was observed between the Bragg wavelength and liquid refractive index, and a sensitivity of ∼30  nm/RIU was observed at 1.450. This shows that D-shaped fiber Bragg gratings might be used to develop promising biochemical sensors.

High-Performance, Large Format Surfaces for Surface-Enhanced Raman Spectroscopy: Increasing the Accessibility of an Analytical Platform

NASA Astrophysics Data System (ADS)

Kanipe, Katherine Nicole

Although surface-enhanced Raman spectroscopy (SERS) is a spectroscopic technique with unusually high sensitivity and molecular specificity, few practical analytical applications have been implemented that take advantage of its power. Based on what is understood about SERS from the experimental and theoretical research of the past forty years, we developed a few well-defined design principles on the basis of which a reliable and reproducibly manufacturable SERS-active substrate could be fabricated that is highly enhancing, highly uniform, stable, and based on a broad range of metals so that various chemical processes could be probed. Finally, we restricted ourselves to using only readily scalable fabrication techniques. The resulting SERS-active device was a metal over silica, two-dimensional nano-grating that was shown to produce enhancements of ˜107 when compared to a smooth surface of the same metal. This SERS substrate also shows unprecedented signal uniformity over square centimeters, and is fabricated using commonly-available foundry-based approaches exclusively. Initially, we explored the properties of a gold-coated substrates in which a first-order grating resonance due to long-range symmetry is augmented by a local resonance due to the individual core-shell grating elements. The SERS properties of such grating systems were systematically studied as a function of various structural parameters such as the grating pitch, the inter-element gap and the thickness of the metal layer. The most enhancing substrates were found to have a grating parameter with a radiative, rather than evanescent, first-order resonance; a sufficiently small gap between nearest neighbor grating elements to produce near-field interactions; and a gold layer whose thickness was larger than the electronic mean-free-path of the conduction electrons, so as to ensure a high conductivity for the metal layer to sustain strong surface plasmons. We applied these same architectural principles to metals other than gold, and concluded that every workable metal (and virtually any material with sufficiently high electrical conductivity) when appropriately nanostructured, has the potential to be an efficient SERS substrate. The use of materials for SERS beyond silver and gold, has significant advantages, most importantly, allowing SERS to be used to study the surface chemistry and catalysis taking place on metals with more interesting chemistries than those of Au and Ag. Additionally, SERS substrates can be fabricated from high natural abundance, low cost materials. This was illustrated by producing SERS substrates using copper, aluminum, and nickel in addition to silver and gold which were used as benchmarks. All five metals were found to yield high SERS intensities. The variation of the SERS enhancement among them is ascribed mainly to local field effects, with the (larger) grating-based enhancement making an approximately equivalent contribution to the SERS enhancement of the five metals. This conclusion is supported by local electric field simulations. The utility of these new grating-based SERS substrates was demonstrated by implementing them in chemical analysis in both aqueous and gas phases for which, for example, we were able to readily detect opioids such as fentanyl and morphine at concentrations as low as less than one part per billion. Additionally, we have made good progress toward integration of this substrate architecture into a microfluidic channel for a higher degree of sample workup and control.

Miniaturized imaging spectrometer based on Fabry-Perot MOEMS filters and HgCdTe infrared focal plane arrays

NASA Astrophysics Data System (ADS)

Velicu, S.; Buurma, C.; Bergeson, J. D.; Kim, Tae Sung; Kubby, J.; Gupta, N.

2014-05-01

Imaging spectrometry can be utilized in the midwave infrared (MWIR) and long wave infrared (LWIR) bands to detect, identify and map complex chemical agents based on their rotational and vibrational emission spectra. Hyperspectral datasets are typically obtained using grating or Fourier transform spectrometers to separate the incoming light into spectral bands. At present, these spectrometers are large, cumbersome, slow and expensive, and their resolution is limited by bulky mechanical components such as mirrors and gratings. As such, low-cost, miniaturized imaging spectrometers are of great interest. Microfabrication of micro-electro-mechanicalsystems (MEMS)-based components opens the door for producing low-cost, reliable optical systems. We present here our work on developing a miniaturized IR imaging spectrometer by coupling a mercury cadmium telluride (HgCdTe)-based infrared focal plane array (FPA) with a MEMS-based Fabry-Perot filter (FPF). The two membranes are fabricated from silicon-oninsulator (SOI) wafers using bulk micromachining technology. The fixed membrane is a standard silicon membrane, fabricated using back etching processes. The movable membrane is implemented as an X-beam structure to improve mechanical stability. The geometries of the distributed Bragg reflector (DBR)-based tunable FPFs are modeled to achieve the desired spectral resolution and wavelength range. Additionally, acceptable fabrication tolerances are determined by modeling the spectral performance of the FPFs as a function of DBR surface roughness and membrane curvature. These fabrication non-idealities are then mitigated by developing an optimized DBR process flow yielding high-performance FPF cavities. Zinc Sulfide (ZnS) and Germanium (Ge) are chosen as the low and the high index materials, respectively, and are deposited using an electron beam process. Simulations are presented showing the impact of these changes and non-idealities in both a device and systems level.

Deformation analysis of MEMS structures by modified digital moiré methods

NASA Astrophysics Data System (ADS)

Liu, Zhanwei; Lou, Xinhao; Gao, Jianxin

2010-11-01

Quantitative deformation analysis of micro-fabricated electromechanical systems is of importance for the design and functional control of microsystems. In this paper, two modified digital moiré processing methods, Gaussian blurring algorithm combined with digital phase shifting and geometrical phase analysis (GPA) technique based on digital moiré method, are developed to quantitatively analyse the deformation behaviour of micro-electro-mechanical system (MEMS) structures. Measuring principles and experimental procedures of the two methods are described in detail. A digital moiré fringe pattern is generated by superimposing a specimen grating etched directly on a microstructure surface with a digital reference grating (DRG). Most of the grating noise is removed from the digital moiré fringes, which enables the phase distribution of the moiré fringes to be obtained directly. Strain measurement result of a MEMS structure demonstrates the feasibility of the two methods.

High-Average-Power Diffraction Pulse-Compression Gratings Enabling Next-Generation Ultrafast Laser Systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alessi, D.

Pulse compressors for ultrafast lasers have been identified as a technology gap in the push towards high peak power systems with high average powers for industrial and scientific applications. Gratings for ultrashort (sub-150fs) pulse compressors are metallic and can absorb a significant percentage of laser energy resulting in up to 40% loss as well as thermal issues which degrade on-target performance. We have developed a next generation gold grating technology which we have scaled to the petawatt-size. This resulted in improvements in efficiency, uniformity and processing as compared to previous substrate etched gratings for high average power. This new designmore » has a deposited dielectric material for the grating ridge rather than etching directly into the glass substrate. It has been observed that average powers as low as 1W in a compressor can cause distortions in the on-target beam. We have developed and tested a method of actively cooling diffraction gratings which, in the case of gold gratings, can support a petawatt peak power laser with up to 600W average power. We demonstrated thermo-mechanical modeling of a grating in its use environment and benchmarked with experimental measurement. Multilayer dielectric (MLD) gratings are not yet used for these high peak power, ultrashort pulse durations due to their design challenges. We have designed and fabricated broad bandwidth, low dispersion MLD gratings suitable for delivering 30 fs pulses at high average power. This new grating design requires the use of a novel Out Of Plane (OOP) compressor, which we have modeled, designed, built and tested. This prototype compressor yielded a transmission of 90% for a pulse with 45 nm bandwidth, and free of spatial and angular chirp. In order to evaluate gratings and compressors built in this project we have commissioned a joule-class ultrafast Ti:Sapphire laser system. Combining the grating cooling and MLD technologies developed here could enable petawatt laser systems to operate at 50kW average power.« less

Complex apodized Bragg grating filters without circulators in silicon-on-insulator.

PubMed

Simard, Alexandre D; LaRochelle, Sophie

2015-06-29

Bragg gratings operating in reflection are versatile filters that are an important building block of photonic circuits but, so far, their use has been limited due to the absence of CMOS compatible integrated circulators. In this paper, we propose to introduce two identical Bragg gratings in the arms of a Mach-Zehnder interferometer built with multimode interference 2 x 2 couplers to provide a reflective filter without circulator. We show that this structure has unique properties that significantly reduce phase noise distortions, avoid the need for thermal phase tuning, and make it compatible with complex apodization functions implemented through superposition apodization. We experimentally demonstrate several Bragg grating filters with high quality reflection spectra. For example, we successfully fabricated a 4 nm dispersion-less square-shaped filter having a sidelobe suppression ratio better than 15 dB and an in-band phase response with a group delay standard deviation of 2.0 ps. This result will enable the fabrication of grating based narrowband reflective filters having sharp spectral responses, which represents a major improvement in the filtering capability of the silicon platform.

Autostereoscopic three-dimensional display by combining a single spatial light modulator and a zero-order nulled grating

NASA Astrophysics Data System (ADS)

Su, Yanfeng; Cai, Zhijian; Liu, Quan; Lu, Yifan; Guo, Peiliang; Shi, Lingyan; Wu, Jianhong

2018-04-01

In this paper, an autostereoscopic three-dimensional (3D) display system based on synthetic hologram reconstruction is proposed and implemented. The system uses a single phase-only spatial light modulator to load the synthetic hologram of the left and right stereo images, and the parallax angle between two reconstructed stereo images is enlarged by a grating to meet the split angle requirement of normal stereoscopic vision. To realize the crosstalk-free autostereoscopic 3D display with high light utilization efficiency, the groove parameters of the grating are specifically designed by the rigorous coupled-wave theory for suppressing the zero-order diffraction, and then the zero-order nulled grating is fabricated by the holographic lithography and the ion beam etching. Furthermore, the diffraction efficiency of the fabricated grating is measured under the illumination of a laser beam with a wavelength of 532 nm. Finally, the experimental verification system for the proposed autostereoscopic 3D display is presented. The experimental results prove that the proposed system is able to generate stereoscopic 3D images with good performances.

Soft x-ray transmission grating spectrometer for X-ray Surveyor and smaller missions with high resolving power

NASA Astrophysics Data System (ADS)

Heilmann, Ralf K.; Bruccoleri, Alexander; Schattenburg, Mark; Kolodziejczak, jeffery; Gaskin, Jessica; O'Dell, Stephen L.

2017-01-01

A number of high priority subjects in astrophysics are addressed by a state-of-the-art soft x-ray grating spectrometer, e.g. the role of Active Galactic Nuclei in galaxy and star formation, characterization of the WHIM and the “missing baryon” problem, characterization of halos around the Milky Way and nearby galaxies, and stellar coronae and surrounding winds and disks. An Explorer-scale, large-area (A > 1,000 cm2), high resolving power (R > 3,000) soft x-ray grating spectrometer is highly feasible based on Critical-Angle Transmission (CAT) grating technology, even for telescopes with angular resolution of 5-10 arcsec. Significantly higher performance could be provided by a CAT grating spectrometer on an X-ray-Surveyor-type mission (A > 4,000 cm2, R > 5,000). CAT gratings combine advantages of blazed reflection gratings (high efficiency, use of higher orders) with those of transmission gratings (low mass, relaxed alignment tolerances and temperature requirements, transparent at higher energies) with minimal mission resource requirements. Blazing is achieved through grazing-incidence reflection off the smooth silicon grating bar sidewalls. Silicon is well matched to the soft x-ray band, and 30% absolute diffraction efficiency has been acheived with clear paths for further improvement. CAT gratings with sidewalls made of high-Z elements allow extension of blazing to higher energies and larger dispersion angles, enabling higher resolving power at shorter wavelengths. X-ray data from CAT gratings coated with a thin layer of platinum using atomic layer deposition demonstrate efficient blazing to higher energies and much larger blaze angles than possible with silicon alone. Measurements of the resolving power of a breadboard CAT grating spectrometer consisting of a Wolter-I slumped-glass focusing optic from GSFC and CAT gratings, taken at the MSFC Stray Light Facility, have demonstrated resolving power > 10,000. Thus currently fabricated CAT gratings are compatible with the most advanced grating spectrometer instrument designs for future soft x-ray spectroscopy missions. We will review the most recent CAT grating fabrication and x-ray test results.

Photonic Hilbert transformers based on laterally apodized integrated waveguide Bragg gratings on a SOI wafer.

PubMed

Bazargani, Hamed Pishvai; Burla, Maurizio; Chrostowski, Lukas; Azaña, José

2016-11-01

We experimentally demonstrate high-performance integer and fractional-order photonic Hilbert transformers based on laterally apodized Bragg gratings in a silicon-on-insulator technology platform. The sub-millimeter-long gratings have been fabricated using single-etch electron beam lithography, and the resulting HT devices offer operation bandwidths approaching the THz range, with time-bandwidth products between 10 and 20.

Recent developments in the fabrication of infrared fiber Bragg gratings

NASA Astrophysics Data System (ADS)

Busse, Lynda; Florea, Catalin; Shaw, Brandon; Sanghera, Jas; Nguyen, Vinh; Chin, Geoff; Aggarwal, Ishwar

2012-02-01

We report on the study of adding metal dopants in chalcogenide glasses to enhance the photosensitivity of the fiber core versus cladding compositions, with goal to enable high reflectivity gratings in infrared-transmitting fibers. Results for the optical and thermal properties of these glasses will be presented, as well as for gratings formation in the glasses using various writing wavelengths for the different doped compositions.

Near-infrared light-controlled tunable grating based on graphene/elastomer composites

NASA Astrophysics Data System (ADS)

Wang, Fei; Jia, Shuhai; Wang, Yonglin; Tang, Zhenhua

2018-02-01

A near-infrared (nIR) light actuated tunable transmission optical grating based on graphene nanoplatelet (GNP)/polydimethylsiloxane (PDMS) and PDMS is proposed. A simple fabrication protocol is studied that allows integration of the grating with the actuation mechanism; both components are made from soft elastomers, and this ensure the tunability and the light-driven operation of the grating. The resulting grating structure demonstrates continuous period tunability of 2.7% under an actuation power density of 220 mW cm-2 within a period of 3 s and also demonstrates a time-independent characteristic. The proposed infrared activated grating can be developed for wireless remote light splitting in bio/chemical sensing and optical telecommunications applications.

Real-time gray-scale photolithography for fabrication of continuous microstructure

NASA Astrophysics Data System (ADS)

Peng, Qinjun; Guo, Yongkang; Liu, Shijie; Cui, Zheng

2002-10-01

A novel real-time gray-scale photolithography technique for the fabrication of continuous microstructures that uses a LCD panel as a real-time gray-scale mask is presented. The principle of design of the technique is explained, and computer simulation results based on partially coherent imaging theory are given for the patterning of a microlens array and a zigzag grating. An experiment is set up, and a microlens array and a zigzag grating on panchromatic silver halide sensitized gelatin with trypsinase etching are obtained.

Narrowband resonant transmitter

DOEpatents

Hutchinson, Donald P.; Simpson, Marcus L.; Simpson, John T.

2004-06-29

A transverse-longitudinal integrated optical resonator (TLIR) is disclosed which includes a waveguide, a first and a second subwavelength resonant grating in the waveguide, and at least one photonic band gap resonant structure (PBG) in the waveguide. The PBG is positioned between the first and second subwavelength resonant gratings. An electro-optic waveguide material may be used to permit tuning the TLIR and to permit the TLIR to perform signal modulation and switching. The TLIR may be positioned on a bulk substrate die with one or more electronic and optical devices and may be communicably connected to the same. A method for fabricating a TLIR including fabricating a broadband reflective grating is disclosed. A method for tuning the TLIR's transmission resonance wavelength is also disclosed.

Transverse-longitudinal integrated resonator

DOEpatents

Hutchinson, Donald P [Knoxville, TN; Simpson, Marcus L [Knoxville, TN; Simpson, John T [Knoxville, TN

2003-03-11

A transverse-longitudinal integrated optical resonator (TLIR) is disclosed which includes a waveguide, a first and a second subwavelength resonant grating in the waveguide, and at least one photonic band gap resonant structure (PBG) in the waveguide. The PBG is positioned between the first and second subwavelength resonant gratings. An electro-optic waveguide material may be used to permit tuning the TLIR and to permit the TLIR to perform signal modulation and switching. The TLIR may be positioned on a bulk substrate die with one or more electronic and optical devices and may be communicably connected to the same. A method for fabricating a TLIR including fabricating a broadband reflective grating is disclosed. A method for tuning the TLIR's transmission resonance wavelength is also disclosed.

Hyperspectral imaging with deformable gratings fabricated with metal-elastomer nanocomposites

NASA Astrophysics Data System (ADS)

Potenza, Marco A. C.; Nazzari, Daniele; Cremonesi, Llorenç; Denti, Ilaria; Milani, Paolo

2017-11-01

We report the fabrication and characterization of a simple and compact hyperspectral imaging setup based on a stretchable diffraction grating made with a metal-polymer nanocomposite. The nanocomposite is produced by implanting Ag clusters in a poly(dimethylsiloxane) film by supersonic cluster beam implantation. The deformable grating has curved grooves and is imposed on a concave cylindrical surface, thus obtaining optical power in two orthogonal directions. Both diffractive and optical powers are obtained by reflection, thus realizing a diffractive-catoptric optical device. This makes it easier to minimize aberrations. We prove that, despite the extended spectral range and the simplified optical scheme, it is actually possible to work with a traditional CCD sensor and achieve a good spectral and spatial resolution.

Zonal wavefront sensing using a grating array printed on a polyester film

NASA Astrophysics Data System (ADS)

Pathak, Biswajit; Kumar, Suraj; Boruah, Bosanta R.

2015-12-01

In this paper, we describe the development of a zonal wavefront sensor that comprises an array of binary diffraction gratings realized on a transparent sheet (i.e., polyester film) followed by a focusing lens and a camera. The sensor works in a manner similar to that of a Shack-Hartmann wavefront sensor. The fabrication of the array of gratings is immune to certain issues associated with the fabrication of the lenslet array which is commonly used in zonal wavefront sensing. Besides the sensing method offers several important advantages such as flexible dynamic range, easy configurability, and option to enhance the sensing frame rate. Here, we have demonstrated the working of the proposed sensor using a proof-of-principle experimental arrangement.

Highly efficient color filter array using resonant Si3N4 gratings.

PubMed

Uddin, Mohammad Jalal; Magnusson, Robert

2013-05-20

We demonstrate the design and fabrication of a highly efficient guided-mode resonant color filter array. The device is designed using numerical methods based on rigorous coupled-wave analysis and is patterned using UV-laser interferometric lithography. It consists of a 60-nm-thick subwavelength silicon nitride grating along with a 105-nm-thick homogeneous silicon nitride waveguide on a glass substrate. The fabricated device exhibits blue, green, and red color response for grating periods of 274, 327, and 369 nm, respectively. The pixels have a spectral bandwidth of ~12 nm with efficiencies of 94%, 96%, and 99% at the center wavelength of blue, green, and red color filter, respectively. These are higher efficiencies than reported in the literature previously.

Silicon-based optoelectronics: Monolithic integration for WDM

NASA Astrophysics Data System (ADS)

Pearson, Matthew Richard T.

2000-10-01

This thesis details the development of enabling technologies required for inexpensive, monolithic integration of Si-based wavelength division multiplexing (WDM) components and photodetectors. The work involves the design and fabrication of arrayed waveguide grating demultiplexers in silicon-on-insulator (SOI), the development of advanced SiGe photodetectors capable of photodetection at 1.55 mum wavelengths, and the development of a low cost fabrication technique that enables the high volume production of Si-based photonic components. Arrayed waveguide grating (AWG) demultiplexers were designed and fabricated in SOI. The fabrication of AWGs in SOI has been reported in the literature, however there are a number of design issues specific to the SOI material system that can have a large effect on device performance and design, and have not been theoretically examined in earlier work. The SOI AWGs presented in this thesis are the smallest devices of this type reported, and they exhibit performance acceptable for commercial applications. The SiGe photodetectors reported in the literature exhibit extremely low responsivities at wavelengths near 1.55 mum. We present the first use of three dimensional growth modes to enhance the photoresponse of SiGe at 1.55 mum wavelengths. Metal semiconductor-metal (MSM) photodetectors were fabricated using this undulating quantum well structure, and demonstrate the highest responsivities yet reported for a SiGe-based photodetector at 1.55 mum. These detectors were monolithically integrated with low-loss SOI waveguides, enabling integration with nearly any Si-based passive WDM component. The pursuit of inexpensive Si-based photonic components also requires the development of new manufacturing techniques that are more suitable for high volume production. This thesis presents the development of a low cost fabrication technique based on the local oxidation of silicon (LOCOS), a standard processing technique used for Si integrated circuits. This process is developed for both SiGe and SOI waveguides, but is shown to be commercially suitable only for SOI waveguide devices. The technique allows nearly any Si microelectronics fabrication facility to begin manufacturing optical components with minimal change in processing equipment or techniques. These enabling technologies provide the critical elements for inexpensive, monolithic integration in a Si-based system.

Research on pressure tactile sensing technology based on fiber Bragg grating array

NASA Astrophysics Data System (ADS)

Song, Jinxue; Jiang, Qi; Huang, Yuanyang; Li, Yibin; Jia, Yuxi; Rong, Xuewen; Song, Rui; Liu, Hongbin

2015-09-01

A pressure tactile sensor based on the fiber Bragg grating (FBG) array is introduced in this paper, and the numerical simulation of its elastic body was implemented by finite element software (ANSYS). On the basis of simulation, fiber Bragg grating strings were implanted in flexible silicone to realize the sensor fabrication process, and a testing system was built. A series of calibration tests were done via the high precision universal press machine. The tactile sensor array perceived external pressure, which is demodulated by the fiber grating demodulation instrument, and three-dimension pictures were programmed to display visually the position and size. At the same time, a dynamic contact experiment of the sensor was conducted for simulating robot encountering other objects in the unknown environment. The experimental results show that the sensor has good linearity, repeatability, and has the good effect of dynamic response, and its pressure sensitivity was 0.03 nm/N. In addition, the sensor also has advantages of anti-electromagnetic interference, good flexibility, simple structure, low cost and so on, which is expected to be used in the wearable artificial skin in the future.

Surface Modified Long Period Fiber Grating Sensor for Rapid Detection of Aspergillus Niger Fungal Spores

NASA Astrophysics Data System (ADS)

Gambhir, Monika; Gupta, Shilpi; John, Priya; Mahakud, Ramakanta; Kumar, Jitendra; Prakash, Om

2018-03-01

We present development of a compact and label-free sensor based on the surface modification of copper vapor laser fabricated long period fiber gratings for detection of airborne Aspergillus niger (A. niger) fungal spores. Surface of sensors were functionalized with monoclonal glucose oxidases IgG1 for target-specific covalent binding. In process of functionalization and binding of 103 cfu/ml of pathogenic A. niger fungal spores, notable shorter wave transition in resonance wavelength from 1562.93 nm to 1555.97 nm, and significant reduction in peak loss from 61.72 dB to 57.48 dB were recorded. The implementation was cost effective and yielded instantaneous results.

Deep-etched sinusoidal polarizing beam splitter grating.

PubMed

Feng, Jijun; Zhou, Changhe; Cao, Hongchao; Lv, Peng

2010-04-01

A sinusoidal-shaped fused-silica grating as a highly efficient polarizing beam splitter (PBS) is investigated based on the simplified modal method. The grating structure depends mainly on the ratio of groove depth to grating period and the ratio of incident wavelength to grating period. These ratios can be used as a guideline for the grating design at different wavelengths. A sinusoidal-groove PBS grating is designed at a wavelength of 1310 nm under Littrow mounting, and the transmitted TM and TE polarized waves are mainly diffracted into the zeroth order and the -1st order, respectively. The grating profile is optimized by using rigorous coupled-wave analysis. The designed PBS grating is highly efficient (>95.98%) over the O-band wavelength range (1260-1360 nm) for both TE and TM polarizations. The sinusoidal grating can exhibit higher diffraction efficiency, larger extinction ratio, and less reflection loss than the rectangular-groove PBS grating. By applying wet etching technology on the rectangular grating, which was manufactured by holographic recording and inductively coupled plasma etching technology, the sinusoidal grating can be approximately fabricated. Experimental results are in agreement with theoretical values.

The Marshall Grazing Incidence X-ray Spectrometer

NASA Astrophysics Data System (ADS)

Kobayashi, Ken; Winebarger, Amy R.; Savage, Sabrina; Champey, Patrick; Cheimets, Peter N.; Hertz, Edward; Bruccoleri, Alexander R.; Golub, Leon; Ramsey, Brian; Ranganathan, Jaganathan; Marquez, Vanessa; Allured, Ryan; Parker, Theodore; Heilmann, Ralf K.; Schattenburg, Mark L.

2017-08-01

The Marshall Grazing Incidence X-ray Spectrometer (MaGIXS) is a NASA sounding rocket instrument designed to obtain spatially resolved soft X-ray spectra of the solar atmosphere in the 6-24 Å (0.5-2.0 keV) range. The instrument consists of a single shell Wolter Type-I telescope, a slit, and a spectrometer comprising a matched pair of grazing incidence parabolic mirrors and a planar varied-line space diffraction grating. The instrument is designed to achieve a 50 mÅ spectral resolution and 5 arcsecond spatial resolution along a +/-4-arcminute long slit, and launch is planned for 2019. We report on the status and our approaches for fabrication and alignment for this novel optical system. The telescope and spectrometer mirrors are replicated nickel shells, and are currently being fabricated at the NASA Marshall Space Flight Center. The diffraction grating is currently under development by the Massachusetts Institute of Technology (MIT); because of the strong line spacing variation across the grating, it will be fabricated through e-beam lithography.

Silicon Nitride Grating Coupler with Flexible Bandwidth Incorporating a Serially Concatenated Multimode Interference Filter

NASA Astrophysics Data System (ADS)

Kim, Woo-Ju; Lee, Hak-Soon; Lee, Sang-Shin

2012-04-01

A compact silicon nitride grating coupler with flexible bandwidth was demonstrated taking advantage of a basic grating integrated with a serially connected multistage multimode interference (MMI) filter. The spectral response could be tailored by varying the order of the MMI filter, without affecting the basic grating structure. The dependence of the spectral response of the proposed device on the order of the MMI stage was thoroughly investigated. As regards the fabricated grating coupler with a four-stage MMI filter, the observed spectral bandwidth was efficiently altered from 53 to 21 nm in the ˜1550 nm spectral band.

Coaxial cable Bragg grating assisted microwave coupler.

PubMed

Huang, Jie; Wei, Tao; Fan, Jun; Xiao, Hai

2014-01-01

This paper reports a microwave coupler based on two parallel coaxial cable Bragg gratings fabricated by drilling U-grooves across the cables at periodic distance along the cable direction. Electromagnetic field couplings between two cables were observed at discrete frequencies through both near and far ends detections. The coupling frequency and strength can be precisely controlled by varying the grating period and length. The coupling bandwidth may also be controlled through specific grating design. The device physics was also described through transfer matrix which matched well with the experimental results.

Orientation-Dependent Displacement Sensor Using an Inner Cladding Fiber Bragg Grating.

PubMed

Yang, Tingting; Qiao, Xueguang; Rong, Qiangzhou; Bao, Weijia

2016-09-11

An orientation-dependent displacement sensor based on grating inscription over a fiber core and inner cladding has been demonstrated. The device comprises a short piece of multi-cladding fiber sandwiched between two standard single-mode fibers (SMFs). The grating structure is fabricated by a femtosecond laser side-illumination technique. Two well-defined resonances are achieved by the downstream both core and cladding fiber Bragg gratings (FBGs). The cladding resonance presents fiber bending dependence, together with a strong orientation dependence because of asymmetrical distribution of the "cladding" FBG along the fiber cross-section.

High-Power Single-Mode 2.65-micron InGaAsSb/AlInGaAsSb Diode Lasers

NASA Technical Reports Server (NTRS)

Frez, Clifford F.; Briggs, Ryan M.; Forouhar, Siamak; Borgentun, Carl E.; Gupta, James

2013-01-01

Central to the advancement of both satellite and in-situ science are improvements in continuous-wave and pulsed infrared laser systems coupled with integrated miniaturized optics and electronics, allowing for the use of powerful, single-mode light sources aboard both satellite and unmanned aerial vehicle platforms. There is a technological gap in supplying adequate laser sources to address the mid-infrared spectral window for spectroscopic characterization of important atmospheric gases. For high-power applications between 2 to 3 micron, commercial laser technologies are unsuitable because of limitations in output power. For instance, existing InP-based laser systems developed for fiber-based telecommunications cannot be extended to wavelengths longer than 2 micron. For emission wavelengths shorter than 3 micron, intersubband devices, such as infrared quantum cascade lasers, become inefficient due to band-offset limitations. To date, successfully demonstrated singlemode GaSb-based laser diodes emitting between 2 and 3 micron have employed lossy metal Bragg gratings for distributed- feedback coupling, which limits output power due to optical absorption. By optimizing both the quantum well design and the grating fabrication process, index-coupled distributed-feedback 2.65-micron lasers capable of emitting in excess of 25 mW at room temperature have been demonstrated. Specifically, lasers at 3,777/cm (2.65 micron) have been realized to interact with strong absorption lines of HDO and other isotopologues of H2O. With minor modifications of the optical cavity and quantum well designs, lasers can be fabricated at any wavelength within the 2-to-3-micron spectral window with similar performance. At the time of this reporting, lasers with this output power and wavelength accuracy are not commercially available. Monolithic ridge-waveguide GaSb lasers were fabricated that utilize secondorder lateral Bragg gratings to generate single-mode emission from InGaAsSb/ AlInGaAsSb multi-quantum well structures. The device fabrication utilizes etched index-coupled gratings in the top AlGaAsSb cladding of the laser chip along the ridge waveguide, whereas commercial lasers that emit close to this wavelength include loss-coupled metal gratings that limit the output power of the laser. Semiconductor-laser-based spectrometers can be used to replace gas sensors currently used in industry and government. With the availability of high-power laser sources at mid-infrared wavelengths, sensors can target strong fundamental gas absorption lines to maximize instrument sensitivity.

Simulation Studies of the Dielectric Grating as an Accelerating and Focusing Structure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Soong, Ken; Peralta, E.A.; Byer, R.L.

A grating-based design is a promising candidate for a laser-driven dielectric accelerator. Through simulations, we show the merits of a readily fabricated grating structure as an accelerating component. Additionally, we show that with a small design perturbation, the accelerating component can be converted into a focusing structure. The understanding of these two components is critical in the successful development of any complete accelerator. The concept of accelerating electrons with the tremendous electric fields found in lasers has been proposed for decades. However, until recently the realization of such an accelerator was not technologically feasible. Recent advances in the semiconductor industry,more » as well as advances in laser technology, have now made laser-driven dielectric accelerators imminent. The grating-based accelerator is one proposed design for a dielectric laser-driven accelerator. This design, which was introduced by Plettner, consists of a pair of opposing transparent binary gratings, illustrated in Fig. 1. The teeth of the gratings serve as a phase mask, ensuring a phase synchronicity between the electromagnetic field and the moving particles. The current grating accelerator design has the drive laser incident perpendicular to the substrate, which poses a laser-structure alignment complication. The next iteration of grating structure fabrication seeks to monolithically create an array of grating structures by etching the grating's vacuum channel into a fused silica wafer. With this method it is possible to have the drive laser confined to the plane of the wafer, thus ensuring alignment of the laser-and-structure, the two grating halves, and subsequent accelerator components. There has been previous work using 2-dimensional finite difference time domain (2D-FDTD) calculations to evaluate the performance of the grating accelerator structure. However, this work approximates the grating as an infinite structure and does not accurately model a realizable structure. In this paper, we will present a 3-dimensional frequency-domain simulation of both the infinite and the finite grating accelerator structure. Additionally, we will present a new scheme for a focusing structure based on a perturbation of the accelerating structure. We will present simulations of this proposed focusing structure and quantify the quality of the focusing fields.« less

Fabrication of digital rainbow holograms and 3-D imaging using SEM based e-beam lithography.

PubMed

Firsov, An; Firsov, A; Loechel, B; Erko, A; Svintsov, A; Zaitsev, S

2014-11-17

Here we present an approach for creating full-color digital rainbow holograms based on mixing three basic colors. Much like in a color TV with three luminescent points per single screen pixel, each color pixel of initial image is presented by three (R, G, B) distinct diffractive gratings in a hologram structure. Change of either duty cycle or area of the gratings are used to provide proper R, G, B intensities. Special algorithms allow one to design rather complicated 3D images (that might even be replacing each other with hologram rotation). The software developed ("RainBow") provides stability of colorization of rotated image by means of equalizing of angular blur from gratings responsible for R, G, B basic colors. The approach based on R, G, B color synthesis allows one to fabricate gray-tone rainbow hologram containing white color what is hardly possible in traditional dot-matrix technology. Budgetary electron beam lithography based on SEM column was used to fabricate practical examples of digital rainbow hologram. The results of fabrication of large rainbow holograms from design to imprinting are presented. Advantages of the EBL in comparison to traditional optical (dot-matrix) technology is considered.

Theoretical modeling and design of photonic structures in zeolite nanocomposites for gas sensing. Part I: surface relief gratings.

PubMed

Cody, D; Naydenova, I

2017-12-01

The suitability of holographic structures fabricated in zeolite nanoparticle-polymer composite materials for gas sensing applications has been investigated. Theoretical modeling of the sensor response (i.e., change in hologram readout due to a change in refractive index modulation or thickness as a result of gas adsorption) of different sensor designs was carried out using Raman-Nath theory and Kogelnik's coupled wave theory. The influence of a range of parameters on the sensor response of holographically recorded surface and volume photonic grating structures has been studied, namely the phase difference between the diffracted and probe beam introduced by the grating, grating geometry, thickness, spatial frequency, reconstruction wavelength, and zeolite nanoparticle refractive index. From this, the optimum fabrication conditions for both surface and volume holographic gas sensor designs have been identified. Here, in part I, results from theoretical modeling of the influence of design on the sensor response of holographically inscribed surface relief structures for gas sensing applications is reported.

Fabrication of high aspect grating using bonded substrate for X-ray refraction imaging by Talbot-Lau interferometer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tada, Takuji; Murakoshi, Dai; Ishii, Hiroyasu

2012-07-31

In order to improve the image quality of X-ray refraction images using a Talbot-Lau interferometer, we have been attempting to fabricate gratings with high aspect ratio. In our attempt, deep grooves of grating structure were channeled on a Si substrate bonded by Au diffusion bonding method, and the grooves were filled with Au where the Au layer used for the bonding Si substrate was acting as a seed layer of Au electroplating. From the results of a visibility measurement and a cross sectional SEM image, it was confirmed that the grooves with a pitch of 5.8 {mu}m and a depthmore » of 100 {mu}m could be successfully filled with Au over a large area of 72 Multiplication-Sign 80 mm{sup 2}. Using this grating, the X-ray refraction images for the cartilage of a knee joint of a livestock pig could be obtained where SPS method was employed for the single-shot image acquisition.« less

Inverse design of near unity efficiency perfectly vertical grating couplers.

PubMed

Michaels, Andrew; Yablonovitch, Eli

2018-02-19

Efficient coupling between integrated optical waveguides and optical fibers is essential to the success of silicon photonics. While many solutions exist, perfectly vertical grating couplers that scatter light out of a waveguide in the direction normal to the waveguide's top surface are an ideal candidate due to their potential to reduce packaging complexity. Designing such couplers with high efficiencies, however, has proven difficult. In this paper, we use inverse electromagnetic design techniques to optimize a high efficiency two-layer perfectly vertical silicon grating coupler. Our base design achieves a chip-to-fiber coupling efficiency of 99.2% (-0.035 dB) at 1550 nm. Using this base design as a starting point, we run subsequent constrained optimizations to realize vertical couplers with coupling efficiencies over 96% and back reflections of less than -40 dB which can be fabricated using 65 nm-resolution lithography. These results demonstrate a new path forward for designing fabrication-tolerant ultra high efficiency grating couplers.

Mode-splitting of a non-polarizing guided mode resonance filter by substrate overetching effect

NASA Astrophysics Data System (ADS)

Saleem, Muhammad Rizwan; Honkanen, Seppo; Turunen, Jari

2014-03-01

We investigate substrate overetch effect on resonance properties of sub-wavelength titanium oxide (TiO2) Guided Mode Resonance Filters (TiO2-GMRFs). The TiO2-GMRF is designed and fabricated to possess a non-polarizing behavior, which is strongly dependent on substrate (fused silica) overetch depth. For non-polarizing gratings at resonance, TE- and TM-modes have the same propagation constants. However, an overetch substrate effect results in splitting of the degenerate modes, which is studied theoretically and experimentally. The TiO2-SiO2 GMRFs are designed by Fourier Modal method (FMM) based on the rigorous calculation of electromagnetic diffraction theory at a designed wavelength of 850 nm. The TiO2-SiO2 gratings are fabricated by Atomic Layer Deposition (ALD), Electron Beam Lithography (EBL), and Reactive Ion Etching (RIE), and they are subsequently characterized structurally by Scanning Electron Microscopy (SEM) and optically by a spectroscopic ellipsometer. Several grating samples are fabricated by gradually increasing the overetch depth into fused silica and measuring the extent of TE- and TM-mode-splitting. A close agreement between the calculated and experimentally measured resonance wavelength spectral shift is found to describe the mode splitting of non-polarizing gratings.

Grism and immersion grating for space telescope

NASA Astrophysics Data System (ADS)

Ebizuka, Noboru; Oka, Kiko; Yamada, Akiko; Ishikawa, Mami; Kashiwagi, Masako; Kodate, Kashiko; Hirahara, Yasuhiro; Sato, Shuji; Kawabata, Koji S.; Wakaki, Moriaki; Morita, Shin-ya; Simizu, Tomoyuki; Yin, Shaohui; Omori, Hitoshi; Iye, Masanori

2017-11-01

The grism is a versatile dispersion element for an astronomical instrument ranging from ultraviolet to infrared. Major benefit of using a grism in a space application, instead of a reflection grating, is the size reduction of optical system because collimator and following optical elements could locate near by the grism. The surface relief (SR) grism is consisted a transmission grating and a prism, vertex angle of which is adjusted to redirect the diffracted beam straight along the direct vision direction at a specific order and wavelength. The volume phase holographic (VPH) grism consists a thick VPH grating sandwiched between two prisms, as specific order and wavelength is aligned the direct vision direction. The VPH grating inheres ideal diffraction efficiency on a higher dispersion application. On the other hand, the SR grating could achieve high diffraction efficiency on a lower dispersion application. Five grisms among eleven for the Faint Object Camera And Spectrograph (FOCAS) of the 8.2m Subaru Telescope with the resolving power from 250 to 3,000 are SR grisms fabricated by a replication method. Six additional grisms of FOCAS with the resolving power from 3,000 to 7,000 are VPH grisms. We propose "Quasi-Bragg grism" for a high dispersion spectroscopy with wide wavelength range. The germanium immersion grating for instance could reduce 1/64 as the total volume of a spectrograph with a conventional reflection grating since refractive index of germanium is over 4.0 from 1.6 to 20 μm. The prototype immersion gratings for the mid-InfraRed High dispersion Spectrograph (IRHS) are successfully fabricated by a nano-precision machine and grinding cup of cast iron with electrolytic dressing method.

Zonal wavefront sensing using a grating array printed on a polyester film

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pathak, Biswajit; Boruah, Bosanta R., E-mail: brboruah@iitg.ernet.in; Kumar, Suraj

2015-12-15

In this paper, we describe the development of a zonal wavefront sensor that comprises an array of binary diffraction gratings realized on a transparent sheet (i.e., polyester film) followed by a focusing lens and a camera. The sensor works in a manner similar to that of a Shack-Hartmann wavefront sensor. The fabrication of the array of gratings is immune to certain issues associated with the fabrication of the lenslet array which is commonly used in zonal wavefront sensing. Besides the sensing method offers several important advantages such as flexible dynamic range, easy configurability, and option to enhance the sensing framemore » rate. Here, we have demonstrated the working of the proposed sensor using a proof-of-principle experimental arrangement.« less

Reflective diffractive beam splitter for laser interferometers.

PubMed

Fahr, Stephan; Clausnitzer, Tina; Kley, Ernst-Bernhard; Tünnermann, Andreas

2007-08-20

The first realization of a reflective 50/50 beam splitter based on a dielectric diffraction grating suitable for high-power laser interferometers is reported. The beam splitter is designed to operate at a wavelength of 1064 nm and in s polarization. To minimize the performance degradation of the device that is due to fabrication fluctuations, during the design process special attention was paid to achieve high fabrication tolerances especially of groove width and depth. Applying this beam splitter to high-power laser interferometers, such as future gravitational wave detectors, will avoid critical thermal lensing effects and allow for the free choice of substrate materials.

Toroidal Variable-Line-Space Gratings: The Good, the Bad and The Ugly

NASA Technical Reports Server (NTRS)

West, Edward A.; Kobayashi, Ken; Cirtain, Jonathan; Gary, Allen; Davis, John; Reader, Joseph

2009-01-01

Toroidal variable-line-space (VLS) gratings are an important factor in the design of an efficient VUV solar telescope that will measure the CIV (155nm) and MgII (280nm) emissions lines in the Sun's transition region. In 1983 Kita and Harada described spherical VLS gratings but the technology to commercially fabricate these devices is a recent development, especially for toroidal surfaces. This paper will describe why this technology is important in the development of the Solar Ultraviolet Magnetograph Investigation (SUMI) sounding rocket program (the good), the delays due to the conversion between the TVLS grating design and the optical fabrication (the bad), and finally the optical testing, alignment and tolerancing of the gratings (the ugly). The Solar Ultraviolet Magnetograph Investigation, SUMI, has been reported in several papers since this program began in 2000. The emphasis of this paper is to describe SUMI's Toroidal Variable-Line-Space (TVLS) gratings. These gratings help SUMI meet its scientific goals which require both high spectral resolution and high optical efficiency for magnetic field measurements in the vacuum ultraviolet wavelength band of the solar spectrum (the good). Unfortunately, the technology readiness level of these gratings has made their implementation difficult, especially for a sounding rocket payload (the bad). Therefore, this paper emphasizes the problems and solutions that were developed to use these gratings in SUMI (the ugly). Section 2 contains a short review of the scientific goals of SUMI and why this mission is important in the understanding of the 3D structure of the magnetic field on the Sun. The flight hardware that makes up the SUMI payload is described in Section 3 with emphasis on those components that affect the TVLS gratings. Section 4 emphasizes the alignment, testing and optical modeling that were developed to optimize the performance of these gratings.

Laterally coupled distributed feedback lasers emitting at 2 μm with quantum dash active region and high-duty-cycle etched semiconductor gratings

NASA Astrophysics Data System (ADS)

Papatryfonos, Konstantinos; Saladukha, Dzianis; Merghem, Kamel; Joshi, Siddharth; Lelarge, Francois; Bouchoule, Sophie; Kazazis, Dimitrios; Guilet, Stephane; Le Gratiet, Luc; Ochalski, Tomasz J.; Huyet, Guillaume; Martinez, Anthony; Ramdane, Abderrahim

2017-02-01

Single-mode diode lasers on an InP(001) substrate have been developed using InAs/In0.53Ga0.47As quantum dash (Qdash) active regions and etched lateral Bragg gratings. The lasers have been designed to operate at wavelengths near 2 μm and exhibit a threshold current of 65 mA for a 600 μm long cavity, and a room temperature continuous wave output power per facet >5 mW. Using our novel growth approach based on the low ternary In0.53Ga0.47As barriers, we also demonstrate ridge-waveguide lasers emitting up to 2.1 μm and underline the possibilities for further pushing the emission wavelength out towards longer wavelengths with this material system. By introducing experimentally the concept of high-duty-cycle lateral Bragg gratings, a side mode suppression ratio of >37 dB has been achieved, owing to an appreciably increased grating coupling coefficient of κ ˜ 40 cm-1. These laterally coupled distributed feedback (LC-DFB) lasers combine the advantage of high and well-controlled coupling coefficients achieved in conventional DFB lasers, with the regrowth-free fabrication process of lateral gratings, and exhibit substantially lower optical losses compared to the conventional metal-based LC-DFB lasers.

All-silicon nanorod-based Dammann gratings.

PubMed

Li, Zile; Zheng, Guoxing; He, Ping'An; Li, Song; Deng, Qiling; Zhao, Jiangnan; Ai, Yong

2015-09-15

Established diffractive optical elements (DOEs), such as Dammann gratings, whose phase profile is controlled by etching different depths into a transparent dielectric substrate, suffer from a contradiction between the complexity of fabrication procedures and the performance of such gratings. In this Letter, we combine the concept of geometric phase and phase modulation in depth, and prove by theoretical analysis and numerical simulation that nanorod arrays etched on a silicon substrate have a characteristic of strong polarization conversion between two circularly polarized states and can act as a highly efficient half-wave plate. More importantly, only by changing the orientation angles of each nanorod can the arrays control the phase of a circularly polarized light, cell by cell. With the above principle, we report the realization of nanorod-based Dammann gratings reaching diffraction efficiencies of 50%-52% in the C-band fiber telecommunications window (1530-1565 nm). In this design, uniform 4×4 spot arrays with an extending angle of 59°×59° can be obtained in the far field. Because of these advantages of the single-step fabrication procedure, accurate phase controlling, and strong polarization conversion, nanorod-based Dammann gratings could be utilized for various practical applications in a range of fields.

M-shaped grating by nanoimprinting: a replicable, large-area, highly active plasmonic surface-enhanced Raman scattering substrate with nanogaps.

PubMed

Zhu, Zhendong; Bai, Benfeng; Duan, Huigao; Zhang, Haosu; Zhang, Mingqian; You, Oubo; Li, Qunqing; Tan, Qiaofeng; Wang, Jia; Fan, Shoushan; Jin, Guofan

2014-04-24

Plasmonic nanostructures separated by nanogaps enable strong electromagnetic-field confinement on the nanoscale for enhancing light-matter interactions, which are in great demand in many applications such as surface-enhanced Raman scattering (SERS). A simple M-shaped nanograting with narrow V-shaped grooves is proposed. Both theoretical and experimental studies reveal that the electromagnetic field on the surface of the M grating can be pronouncedly enhanced over that of a grating without such grooves, due to field localization in the nanogaps formed by the narrow V grooves. A technique based on room-temperature nanoimprinting lithography and anisotropic reactive-ion etching is developed to fabricate this device, which is cost-effective, reliable, and suitable for fabricating large-area nanostructures. As a demonstration of the potential application of this device, the M grating is used as a SERS substrate for probing Rhodamine 6G molecules. Experimentally, an average SERS enhancement factor as high as 5×10⁸ has been achieved, which verifies the greatly enhanced light-matter interaction on the surface of the M grating over that of traditional SERS surfaces. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Monolithic integration of an InP-based 4 × 25 GHz photodiode array to an O-band arrayed waveguide grating demultiplexer

NASA Astrophysics Data System (ADS)

Ye, Han; Han, Qin; Lv, Qianqian; Pan, Pan; An, Junming; Yang, Xiaohong

2017-12-01

We demonstrate the monolithic integration of a uni-traveling carrier photodiode array with a 4 channel, O-band arrayed waveguide grating demultiplexer on the InP platform by the selective area growth technique. An extended coupling layer at the butt-joint is adopted to ensure both good fabrication compatibility and high photodiode quantum efficiency of 77%. The fabricated integrated chip exhibits a uniform bandwidth over 25 GHz for each channel and a crosstalk below -22 dB.

Mode-routed fiber-optic add-drop filter

NASA Technical Reports Server (NTRS)

Moslehi, Behzad (Inventor); Black, Richard James (Inventor); Shaw, Herbert John (Inventor)

2000-01-01

New elements mode-converting two-mode grating and mode-filtering two-mode coupler are disclosed and used as elements in a system for communications, add-drop filtering, and strain sensing. Methods of fabrication for these new two-mode gratings and mode-filtering two-mode couplers are also disclosed.

Refractive index and temperature sensitivity characteristics of a micro-slot fiber Bragg grating.

PubMed

Saffari, Pouneh; Yan, Zhijun; Zhou, Kaiming; Zhang, Lin

2012-07-10

Fabrication and characterization of a UV inscribed fiber Bragg grating (FBG) with a micro-slot liquid core is presented. Femtosecond (fs) laser patterning/chemical etching technique was employed to engrave a micro-slot with dimensions of 5.74 μm(h)×125 μm(w)×1388.72 μm(l) across the whole grating. The device has been evaluated for refractive index (RI) and temperature sensitivities and exhibited distinctive thermal response and RI sensitivity beyond the detection limit of reported fiber gratings. This structure has not just been RI sensitive, but also maintained the robustness comparing with the bare core FBGs and long-period gratings with the partial cladding etched off.

Grating scattering BRDF and imaging performances: A test survey performed in the frame of the flex mission

NASA Astrophysics Data System (ADS)

Harnisch, Bernd; Deep, Atul; Vink, Ramon; Coatantiec, Claude

2017-11-01

Key components in optical spectrometers are the gratings. Their influence on the overall infield straylight of the spectrometer depends not only on the technology used for grating fabrication but also on the potential existence of ghost images caused by irregularities of the grating constant. For the straylight analysis of spectrometer no general Bidirectional Reflectance Distribution Function (BRDF) model of gratings exist, as it does for optically smooth surfaces. These models are needed for the determination of spectrometer straylight background and for the calculation of spectrometer out of band rejection performances. Within the frame of the Fluorescence Earth Explorer mission (FLEX), gratings manufactured using different technologies have been investigated in terms of straylight background and imaging performance in the used diffraction order. The gratings which have been investigated cover a lithographically written grating, a volume Bragg grating, two holographic gratings and an off-the-shelf ruled grating. In this paper we present a survey of the measured bidirectional reflectance/transmittance distribution function and the determination of an equivalent surface micro-roughness of the gratings, describing the scattering of the grating around the diffraction order. This is specifically needed for the straylight modeling of the spectrometer.

Fabrication of Extremely Short Length Fiber Bragg Gratings for Sensor Applications

NASA Technical Reports Server (NTRS)

Wu, Meng-Chou; Rogowski, Robert S.; Tedjojuwono, Ken K.

2002-01-01

A new technique and a physical model for writing extremely short length Bragg gratings in optical fibers have been developed. The model describes the effects of diffraction on the spatial spectra and therefore, the wavelength spectra of the Bragg gratings. Using an interferometric technique and a variable aperture, short gratings of various lengths and center wavelengths were written in optical fibers. By selecting the related parameters, the Bragg gratings with typical length of several hundred microns and bandwidth of several nanometers can be obtained. These short gratings can be apodized with selected diffraction patterns and hence their broadband spectra have a well-defined bell shape. They are suitable for use as miniaturized distributed strain sensors, which have broad applications to aerospace research and industry as well.

Single-Mode, Distributed Feedback Interband Cascade Lasers

NASA Technical Reports Server (NTRS)

Frez, Clifford F. (Inventor); Borgentun, Carl E. (Inventor); Briggs, Ryan M. (Inventor); Bagheri, Mahmood (Inventor); Forouhar, Siamak (Inventor)

2016-01-01

Single-mode, distributed feedback interband cascade lasers (ICLs) using distributed-feedback gratings (e.g., lateral Bragg gratings) and methods of fabricating such ICLs are provided. The ICLs incorporate distributed-feedback gratings that are formed above the laser active region and adjacent the ridge waveguide (RWG) of the ICL. The ICLs may incorporate a double-ridge system comprising an optical confinement structure (e.g., a RWG) disposed above the laser active region that comprises the first ridge of the double ridge system, a DFB grating (e.g., lateral Bragg grating) disposed above the laser active region and adjacent the optical confinement structure, and an electric confinement structure that passes at least partially through the laser active region and that defines the boundary of the second ridge comprises and the termination of the DFB grating.

High Precision 2-D Grating Groove Density Measurement

NASA Astrophysics Data System (ADS)

Zhang, Ningxiao; McEntaffer, Randall; Tedesco, Ross

2017-08-01

Our research group at Penn State University is working on producing X-ray reflection gratings with high spectral resolving power and high diffraction efficiency. To estimate our fabrication accuracy, we apply a precise 2-D grating groove density measurement to plot groove density distributions of gratings on 6-inch wafers. In addition to plotting a fixed groove density distribution, this method is also sensitive to measuring the variation of the groove density simultaneously. This system can reach a measuring accuracy (ΔN/N) of 10-3. Here we present this groove density measurement and some applications.

Diffractive optical elements on non-flat substrates using electron beam lithography

NASA Technical Reports Server (NTRS)

Maker, Paul D. (Inventor); Muller, Richard E. (Inventor); Wilson, Daniel W. (Inventor)

2002-01-01

The present disclosure describes a technique for creating diffraction gratings on curved surfaces with electron beam lithography. The curved surface can act as an optical element to produce flat and aberration-free images in imaging spectrometers. In addition, the fabrication technique can modify the power structure of the grating orders so that there is more energy in the first order than for a typical grating. The inventors noticed that by using electron-beam lithography techniques, a variety of convex gratings that are well-suited to the requirements of imaging spectrometers can be manufactured.

Long-period fibre grating writing with a slit-apertured femtosecond laser beam (λ = 1026 nm)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dostovalov, A V; Wolf, A A; Babin, S A

We report on long-period grating (LPG) writing in a standard telecom fibre, SMF-28e+, via refractive index modification by femtosecond pulses. A method is proposed for grating writing with a slit-apertured beam, which enables one to produce LPGs with reduced background losses and a resonance peak markedly stronger than that in the case of grating writing with a Gaussian beam. The method can be used to fabricate LPGs for use as spectral filters of fibre lasers and sensing elements of sensor systems. (fibre and integrated-optical structures)

Orientation-Dependent Displacement Sensor Using an Inner Cladding Fiber Bragg Grating

PubMed Central

Yang, Tingting; Qiao, Xueguang; Rong, Qiangzhou; Bao, Weijia

2016-01-01

An orientation-dependent displacement sensor based on grating inscription over a fiber core and inner cladding has been demonstrated. The device comprises a short piece of multi-cladding fiber sandwiched between two standard single-mode fibers (SMFs). The grating structure is fabricated by a femtosecond laser side-illumination technique. Two well-defined resonances are achieved by the downstream both core and cladding fiber Bragg gratings (FBGs). The cladding resonance presents fiber bending dependence, together with a strong orientation dependence because of asymmetrical distribution of the “cladding” FBG along the fiber cross-section. PMID:27626427

Mask fabrication and its applications to extreme ultra-violet diffractive optics

NASA Astrophysics Data System (ADS)

Cheng, Yang-Chun

Short-wavelength radiation around 13nm of wavelength (Extreme Ultra-Violet, EUV) is being considered for patterning microcircuits, and other electronic chips with dimensions in the nanometer range. Interferometric Lithography (IL) uses two beams of radiation to form high-resolution interference fringes, as small as half the wavelength of the radiation used. As a preliminary step toward manufacturing technology, IL can be used to study the imaging properties of materials in a wide spectral range and at nanoscale dimensions. A simple implementation of IL uses two transmission diffraction gratings to form the interference pattern. More complex interference patterns can be created by using different types of transmission gratings. In this thesis, I describe the development of a EUV lithography system that uses diffractive optical elements (DOEs), from simple gratings to holographic structures. The exposure system is setup on a EUV undulator beamline at the Synchrotron Radiation Center, in the Center for NanoTechnology clean room. The setup of the EUV exposure system is relatively simple, while the design and fabrication of the DOE "mask" is complex, and relies on advanced nanofabrication techniques. The EUV interferometric lithography provides reliable EUV exposures of line/space patterns and is ideal for the development of EUV resist technology. In this thesis I explore the fabrication of these DOE for the EUV range, and discuss the processes I have developed for the fabrication of ultra-thin membranes. In addition, I discuss EUV holographic lithography and generalized Talbot imaging techniques to extend the capability of our EUV-IL system to pattern arbitrary shapes, using more coherent sources than the undulator. In a series of experiments, we have demonstrated the use of a soft X-ray (EUV) laser as effective source for EUV lithography. EUV-IL, as implemented at CNTech, is being used by several companies and research organizations to characterize photoresist materials.

Fabrication of flexible oriented magnetic thin films with large in-plane uniaxial anisotropy by roll-to-roll nanoimprint lithography

NASA Astrophysics Data System (ADS)

Thantirige, Rukshan M.; John, Jacob; Pradhan, Nihar R.; Carter, Kenneth R.; Tuominen, Mark T.

2016-06-01

Here, we report wafer scale fabrication of densely packed Fe nanostripe-based magnetic thin films on a flexible substrate and their magnetic anisotropy properties. We find that Fe nanostripes exhibit large in-plane uniaxial anisotropy and nearly square hysteresis loops with energy products (BHmax) exceeding 3 MGOe at room temperature. High density Fe nanostripes were fabricated on 70 nm flexible polyethylene terephthalate (PET) gratings, which were made by a roll-to-roll (R2R) UV nanoimprint lithography technique. We observed large in-plane uniaxial anisotropies along the long dimension of nanostripes that can be attributed to the shape. Temperature dependent hysteresis measurements confirm that the magnetization reversal is driven by non-coherent rotation reversal processes.

Rapid and high throughput fabrication of high temperature stable structures through PDMS transfer printing

NASA Astrophysics Data System (ADS)

Hohenberger, Erik; Freitag, Nathan; Korampally, Venumadhav

2017-07-01

We report on a facile and low cost fabrication approach for structures—gratings and enclosed nanochannels, through simple solution processed chemistries in conjunction with nanotransfer printing techniques. The ink formulation primarily consisting of an organosilicate polymeric network with a small percentage of added 3-aminopropyl triethoxysilane crosslinker allows one to obtain robust structures that are not only stable towards high temperature processing steps as high as 550 °C but also exhibit exceptional stability against a host of organic solvent washes. No discernable structure distortion was observed compared to the as-printed structures (room temperature processed) when printed structures were subjected to temperatures as high as 550 °C. We further demonstrate the applicability of this technique towards the fabrication of more complex nanostructures such as enclosed channels through a double transfer method, leveraging the exceptional room temperature cross-linking ability of the printed structures and their subsequent resistance to dissolution in organic solvent washes. The exceptional temperature and physico-chemical stability of the nanotransfer printed structures makes this a useful fabrication tool that may be applied as is, or integrated with conventional lithographic techniques for the large area fabrication of functional nanostructures and devices.

Adaptive optics high-resolution IR spectroscopy with silicon grisms and immersion gratings

NASA Astrophysics Data System (ADS)

Ge, Jian; McDavitt, Daniel L.; Chakraborty, Abhijit; Bernecker, John L.; Miller, Shane

2003-02-01

The breakthrough of silicon immersion grating technology at Penn State has the ability to revolutionize high-resolution infrared spectroscopy when it is coupled with adaptive optics at large ground-based telescopes. Fabrication of high quality silicon grism and immersion gratings up to 2 inches in dimension, less than 1% integrated scattered light, and diffraction-limited performance becomes a routine process thanks to newly developed techniques. Silicon immersion gratings with etched dimensions of ~ 4 inches are being developed at Penn State. These immersion gratings will be able to provide a diffraction-limited spectral resolution of R = 300,000 at 2.2 micron, or 130,000 at 4.6 micron. Prototype silicon grisms have been successfully used in initial scientific observations at the Lick 3m telescope with adaptive optics. Complete K band spectra of a total of 6 T Tauri and Ae/Be stars and their close companions at a spectral resolution of R ~ 3000 were obtained. This resolving power was achieved by using a silicon echelle grism with a 5 mm pupil diameter in an IR camera. These results represent the first scientific observations conducted by the high-resolution silicon grisms, and demonstrate the extremely high dispersing power of silicon-based gratings. New discoveries from this high spatial and spectral resolution IR spectroscopy will be reported. The future of silicon-based grating applications in ground-based AO IR instruments is promising. Silicon immersion gratings will make very high-resolution spectroscopy (R > 100,000) feasible with compact instruments for implementation on large telescopes. Silicon grisms will offer an efficient way to implement low-cost medium to high resolution IR spectroscopy (R ~ 1000-50000) through the conversion of existing cameras into spectrometers by locating a grism in the instrument's pupil location.

Optical high temperature sensor based on fiber Bragg grating

NASA Astrophysics Data System (ADS)

Zhang, Bowei

The aim of this thesis is to fabricate a fiber Bragg grating (FBG) temperature sensor that is capable to measure temperatures in excess of 1100°C. For this purpose, two topics have been studied and investigated during this project. One of them is the development of a high temperature resistant molecular-water induced FBGs; and the other is to investigate the effect of microwave-irradiation on the hydrogen-loaded FBG. The molecular-water induced FBGs are different from the other types of FBG. In these devices the refractive index is modulated by the periodic changes of molecular-water concentration within the grating. The device was developed using thermal annealing technology based on hydrogen-load FBG. Thermal stability of these devices was studied by measuring the grating reflectivity from room temperature to 1000°C. The stability of the device was tested by examining the FBG reflectivity for a period of time at certain temperatures. The results show that these devices are extremely stable at temperatures in excess of 1000°C. The hydroxyl concentration in the grating has been also investigated during this thesis. Based on the knowledge of hydroxyl groups inside FBG, a microwave treatment was designed to increase the hydroxyl concentration in the FBG area. The results show that the molecular-water induced grating, which was fabricated using microwave radiated hydrogen-loaded FBI, are stable at temperatures above 1100°C.

Fabricating fiber Bragg gratings with two phase masks based on reconstruction-equivalent-chirp technique.

PubMed

Gao, Liang; Chen, Xiangfei; Xiong, Jintian; Liu, Shengchun; Pu, Tao

2012-01-30

Based on reconstruction-equivalent-chirp (REC) technique, a novel solution for fabricating low-cost long fiber Bragg gratings (FBGs) with desired properties is proposed and initially studied. A proof-of-concept experiment is demonstrated with two conventional uniform phase masks and a submicron-precision translation stage, successfully. It is shown that the original phase shift (OPS) caused by phase mismatch of the two phase masks can be compensated by the equivalent phase shift (EPS) at the ±1st channels of sampled FBGs, separately. Furthermore, as an example, a π phase-shifted FBG of about 90 mm is fabricated by using these two 50mm-long uniform phase masks based on the presented method.

Imaging Grating Spectrometer (I-GRASP) for Solar Soft X-Ray Spectral Measurements in Critically Under-Observed 0.5 - 7 nm Spectral Range

NASA Astrophysics Data System (ADS)

Didkovsky, L. V.; Wieman, S. R.; Chao, W.; Woods, T. N.; Jones, A. R.; Thiemann, E.; Mason, J. P.

2016-12-01

We discuss science and technology advantages of the Imaging Grating Spectrometer (I-GRASP) based on a novel transmission diffracting grating (TDG) made possible by technology for fabricating Fresnel zone plates (ZPs) developed at the Lawrence Berkeley National Laboratory (LBNL). Older version TDGs with 200 nm period available in the 1990s became a proven technology for providing 21 years of regular measurements of solar EUV irradiance. I-GRASP incorporates an advanced TDG with a grating period of 50 nm providing four times better diffraction dispersion than the 200 nm period gratings used in the SOHO/CELIAS/SEM, the SDO/EVE/ESP flight spectrophotometers, and the EVE/SAM sounding rocket channel. Such new technology for the TDG combined with a back-illuminated 2000 x 1504 CMOS image sensor with 7 micron pixels, will provide spatially-and-spectrally resolved images and spectra from individual Active Regions (ARs) and solar flares with high (0.15 nm) spectral resolution. Such measurements are not available in the spectral band from about 2 to 6 nm from existing or planned spectrographs and will be significantly important to study ARs and solar flare temperatures and dynamics, to improve existing spectral models, e.g. CHIANTI, and to better understand processes in the Earth's atmosphere processes. To test this novel technology, we have proposed to the NASA LCAS program an I-GRASP version for a sounding rocket flight to increase the TDG TRL to a level appropriate for future CubeSat projects.

Distributed Feedback Laser Based on Single Crystal Perovskite

NASA Astrophysics Data System (ADS)

Sun, Shang; Xiao, Shumin; Song, Qinghai

2017-06-01

We demonstrate a single crystal perovskite based, with grating-structured photoresist on top, highly polarized distributed feedback laser. A lower laser threshold than the Fabry-Perot mode lasers from the same single crystal CH3NH3PbBr3 microplate was obtained. Single crystal CH3NH3PbBr3 microplates was synthesized with one-step solution processed precipitation method. Once the photoresist on top of the microplate was patterned with electron beam, the device was realized. This one-step fabrication process utilized the advantage of single crystal to the greatest extend. The ultra-low defect density in single crystalline microplate offer an opportunity for lower threshold lasing action compare with poly-crystal perovskite films. In the experiment, the lasing action based on the distributed feedback grating design was found with lower threshold and higher intensity than the Fabry-Perot mode lasers supported by the flat facets of the same microplate.

X-ray grating interferometry at photon energies over 180 keV

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ruiz-Yaniz, M., E-mail: maite.ruiz-yaniz@esrf.fr; Lehrstuhl für Biomedizinische Physik, Physik-Department and Institut für Medizintechnik, Technische Universität München, James-Franck-Str. 1, 85748 Garching; Koch, F.

2015-04-13

We report on the implementation and characterization of grating interferometry operating at an x-ray energy of 183 keV. With the possibility to use this technique at high x-ray energies, bigger specimens could be studied in a quantitative way. Also, imaging strongly absorbing specimens will benefit from the advantages of the phase and dark-field signals provided by grating interferometry. However, especially at these high photon energies the performance of the absorption grating becomes a key point on the quality of the system, because the grating lines need to keep their small width of a couple of micrometers and exhibit a greater heightmore » of hundreds of micrometers. The performance of high aspect ratio absorption gratings fabricated with different techniques is discussed. Further, a dark-field image of an alkaline multicell battery highlights the potential of high energy x-ray grating based imaging.« less

Compact silicon diffractive sensor: design, fabrication, and prototype.

PubMed

Maikisch, Jonathan S; Gaylord, Thomas K

2012-07-01

An in-plane constant-efficiency variable-diffraction-angle grating and an in-plane high-angular-selectivity grating are combined to enable a new compact silicon diffractive sensor. This sensor is fabricated in silicon-on-insulator and uses telecommunications wavelengths. A single sensor element has a micron-scale device size and uses intensity-based (as opposed to spectral-based) detection for increased integrability. In-plane diffraction gratings provide an intrinsic splitting mechanism to enable a two-dimensional sensor array. Detection of the relative values of diffracted and transmitted intensities is independent of attenuation and is thus robust. The sensor prototype measures refractive index changes of 10(-4). Simulations indicate that this sensor configuration may be capable of measuring refractive index changes three or four orders of magnitude smaller. The characteristics of this sensor type make it promising for lab-on-a-chip applications.

Modeling and simulation of blazed grating based on MEMS scanning micro-mirror for NIR micro-spectrometer

NASA Astrophysics Data System (ADS)

Zhou, Ying; Wen, Zhiyu; Yang, Tingyan; Lei, Hongjie

2015-11-01

Near infrared micro-spectrometer (NIRMS) as a vital detection equipment for various elements has been investigated over the last few years. Traditional MEMS NIRMS employs CCD array detectors for NIR spectrum collection and this leads to higher fabrication cost. In this paper, to ensure the higher diffraction efficiency as well as lower fabrication cost, a novel blazed grating based on MEMS scanning micro-mirror (SMM) is proposed. By our design method, the NIRMS needs only one single InGaAs detector photo diode to collect NIR spectrum and ensure the high diffraction efficiency. Our results show that the diffraction efficiency of the blazed grating is almost 50% and the peak value reaches to 90% in the range of 900-2,100 nm while the optical scanning angle is 14.2°.

A Sliding-Mode Triboelectric Nanogenerator with Chemical Group Grated Structure by Shadow Mask Reactive Ion Etching.

PubMed

Shang, Wanyu; Gu, Guang Qin; Yang, Feng; Zhao, Lei; Cheng, Gang; Du, Zu-Liang; Wang, Zhong Lin

2017-09-26

The sliding-mode triboelectric nanogenerator (S-TENG) with grated structure has important applications in energy harvest and active sensors; however its concavo-convex structure leads to large frictional resistance and abrasion. Here, we developed a S-TENG with a chemical group grated structure (S-TENG-CGG), in which the triboelectric layer's triboelectric potential has a positive-negative alternating charged structure. The triboelectric layer of the S-TENG-CGG was fabricated through a reactive ion etching process with a metal shadow mask with grated structure. In the etched region, the nylon film, originally positively charged as in friction with stainless steel, gained opposite triboelectric potential and became negatively charged because of the change of surface functional groups. The output signals of the S-TENG-CGG are alternating and the frequency is determined by both the segment numbers and the moving speed. The applications of the S-TENG-CGG in the charging capacitor and driving calculator are demonstrated. In the S-TENG-CGG, since there is no concavo-convex structure, the frictional resistance and abrasion are largely reduced, which enhances its performances in better stability and longer working time.

Phyllotactic arrangements of optical elements

NASA Astrophysics Data System (ADS)

Horacek, M.; Meluzin, P.; Kratky, S.; Matejka, M.; Kolarik, V.

2017-05-01

Phyllotaxy studies arrangements of biological entities, e.g. a placement of seeds in the flower head. Vogel (1979) presented a phyllotactic model based on series of seeds ordered along a primary spiral. This arrangement allows each seed to occupy the same area within a circular flower head. Recently, a similar arrangement of diffraction primitives forming a planar relief diffractive structure was presented. The planar relief structure was used for benchmarking and testing purposes of the electron beam writer patterning process. This contribution presents the analysis of local periods and azimuths of optical phyllotactic arrangements. Two kinds of network characteristic triangles are introduced. If the discussed planar structure has appropriate size and density, diffraction of the incoming light creates characteristic a phyllotactic diffraction pattern. Algorithms enabling the analysis of such behavior were developed and they were validated by fabricated samples of relief structures. Combined and higher diffraction orders are also analyzed. Different approaches enabling the creation of phyllotactic diffractive patterns are proposed. E-beam lithography is a flexible technology for various diffraction gratings origination. The e-beam patterning typically allows for the creation of optical diffraction gratings in the first diffraction order. Nevertheless, this technology enables also more complex grating to be prepared, e.g. blazed gratings and zero order gratings. Moreover, the mentioned kinds of gratings can be combined within one planar relief structure. The practical part of the presented work deals with the nano patterning of such structures by using two different types of the e-beam pattern generators.

A direction detective asymmetrical twin-core fiber curving sensor

NASA Astrophysics Data System (ADS)

An, Maowei; Geng, Tao; Yang, Wenlei; Zeng, Hongyi; Li, Jian

2015-10-01

Long period fiber gratings (LPFGs), which can couple the core mode to the forward propagating cladding modes of a fiber and have the advantage of small additional loss, no backward reflection, small size, which is widely used in optical fiber sensors and optical communication systems. LPFG has different fabricating methods, in order to write gratings on the twin-core at the same time effectively, we specially choose electric heating fused taper system to fabricate asymmetric dual-core long period fiber grating, because this kind of method can guarantee the similarity of gratings on the twin cores and obtain good geometric parameters of LPFG, such as cycle, cone waist. Then we use bending test platform to conduct bending test for each of the core of twin-core asymmetric long period fiber grating. Experiments show that: the sensitivity of asymmetrical twin-core long period fiber grating's central core under bending is -5.47nm·m, while the sensitivity of asymmetric twin-core long period fiber grating partial core changed with the relative position of screw micrometer. The sensitivity at 0°, 30°, 90° direction is -4.22nm·m, -9.84nm·m, -11.44nm·m respectively. The experiment results strongly demonstrate the properties of rim sensing of asymmetrical twin-core fiber gratings which provides the possibility of simultaneously measuring the bending magnitude and direction and solving the problem of cross sensing when multi-parameter measuring. In other words, we can detect temperature and bend at the same time by this sensor. As our knowledge, it is the first time simultaneously measuring bend and temperature using this structure of fiber sensors.

Diffractive Optical Elements for Spectral Imaging

NASA Technical Reports Server (NTRS)

Wilson, D.; Maker, P.; Muller, R.; Mourolis, P.; Descour, M.; Volin, C.; Dereniak, E.

2000-01-01

Diffractive optical elements fabricated on flat and non-flat substrates frequently act as dispersive elements in imaging spectrometers. We describe the design and electron-beam fabrication of blazed and computer-generated-hologram gratings for slit and tomographic imaging spectrometer.

Diffractive Optical Elements for Spectral Imaging

NASA Technical Reports Server (NTRS)

Wilson, D.; Maker, P.; Muller, R.; Maker, P.; Mouroulis, P.; Descour, M.; Volin, C.; Dereniak, E.

2000-01-01

Diffractive optical elements fabricated on flat and non-flat substrates frequently act as dispersive elements in imaging spectrometers. We describe the design and electron-beam fabrication of blazed and computer-generated-hologram gratings for slit and tomographic imaging spectrometers.

Temperature and strain characterization of long period gratings in air guiding fiber

NASA Astrophysics Data System (ADS)

Iadicicco, Agostino; Cutolo, Antonello; Cusano, Andrea; Campopiano, Stefania

2013-05-01

This paper reports on the fabrication of Long Period Gratings (LPGs) in hollow-core air-silica photonic bandgap fibers by using pressure assisted Electrode Arc Discharge (EAD) technique. In particular, the fabrication procedure relies on the combined use of EAD step, to locally heat the HC fiber, and of a static pressure (slightly higher than the external one) inside the fiber holes, to modify the holes. This procedure permits to preserve the holey structure of the host fiber avoiding any hole collapsing and it enables a local effective refractive index change due to the size and shape modifications of core and cladding holes. Periodically repeated EAD treatments permit the fabrication of LPGs based devices in hollow core optical fibers enabling new functionalities hitherto not possible. Here, the experimental fabrication of LPG prototypes with different periods and lengths are discussed. And, the HC-LPGs sensitivity to environmental parameters such as strain and temperature are investigated.

Annealing dynamics of waveguide Bragg gratings: evidence of femtosecond laser induced colour centres.

PubMed

Dekker, P; Ams, M; Marshall, G D; Little, D J; Withford, M J

2010-02-15

There is still significant speculation regarding the nature of femtosecond laser induced index change in bulk glasses with colour centre formation and densification the main candidates. In the work presented here, we fabricated waveguide Bragg gratings in doped and undoped phosphate glasses and use these as a diagnostic for monitoring subtle changes in the induced refractive index during photo- and thermal annealing experiments. Reductions in grating strengths during such experiments were attributed to the annihilation of colour centres.

Study of silicon strip waveguides with diffraction gratings and photonic crystals tuned to a wavelength of 1.5 µm

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barabanenkov, M. Yu., E-mail: barab@iptm.ru; Vyatkin, A. F.; Volkov, V. T.

2015-12-15

Single-mode submicrometer-thick strip waveguides on silicon-on-insulator substrates, fabricated by silicon-planar-technology methods are considered. To solve the problem of 1.5-µm wavelength radiation input-output and its frequency filtering, strip diffraction gratings and two-dimensional photonic crystals are integrated into waveguides. The reflection and transmission spectra of gratings and photonic crystals are calculated. The waveguide-mode-attenuation coefficient for a polycrystalline silicon waveguide is experimentally estimated.

Fabrication of large diffractive optical elements in thick film on a concave lens surface.

PubMed

Xie, Yongjun; Lu, Zhenwu; Li, Fengyou

2003-05-05

We demonstrate experimentally the technique of fabricating large diffractive optical elements (DOEs) in thick film on a concave lens surface (mirrors) with precise alignment by using the strategy of double exposure. We adopt the method of double exposure to overcome the difficulty of processing thick photoresist on a large curved substrate. A uniform thick film with arbitrary thickness on a concave lens can be obtained with this technique. We fabricate a large concentric circular grating with a 10-ìm period on a concave lens surface in film with a thickness of 2.0 ìm after development. It is believed that this technique can also be used to fabricate larger DOEs in thicker film on the concave or convex lens surface with precise alignment. There are other potential applications of this technique, such as fabrication of micro-optoelectromechanical systems (MOEMS) or microelectromechanical systems (MEMS) and fabrication of microlens arrays on a large concave lens surface or convex lens surface with precise alignment.

Fabrication and characterization of a deep ultraviolet wire grid polarizer with a chromium-oxide subwavelength grating.

PubMed

Asano, Kosuke; Yokoyama, Satoshi; Kemmochi, Atsushi; Yatagai, Toyohiko

2014-05-01

A wire grid polarizer comprised of chromium oxide is designed for a micro-lithography system using an ArF excimer laser. Optical properties for some material candidates are calculated using a rigorous coupled-wave analysis. The chromium oxide wire grid polarizer with a 90 nm period is fabricated by a double-patterning technique using KrF lithography and dry etching. The extinction ratio of the grating is greater than 20 dB (100:1) at a wavelength of 193 nm. Differences between the calculated and experimental results are discussed.

Highly controllable ICP etching of GaAs based materials for grating fabrication

NASA Astrophysics Data System (ADS)

Weibin, Qiu; Jiaxian, Wang

2012-02-01

Highly controllable ICP etching of GaAs based materials with SiCl4/Ar plasma is investigated. A slow etching rate of 13 nm/min was achieved with RF1 D 10 W, RF2 D 20 W and a high ratio of Ar to SiCl4 flow. First order gratings with 25 nm depth and 140 nm period were fabricated with the optimal parameters. AFM analysis indicated that the RMS roughness over a 10 × 10 μm2 area was 0.3 nm, which is smooth enough to regrow high quality materials for devices.

Copper Doped Methylene Blue Sensitized Poly(vinyl alcohol)-Acrylamide Films for Stable Diffraction Efficiency

NASA Astrophysics Data System (ADS)

John, Beena Mary; Joseph, Rani; Sreekumar, K.; Sudha Kartha, C.

2006-11-01

Copper doped methylene blue sensitized poly(vinyl alcohol) (MBPVA)-acrylamide films were fabricated to improve the storage life of recorded gratings. The films were fabricated using gravity settling method and the copper chloride concentration was optimized as 3.18× 10-3 mol/l for a dye concentration of 6.2× 10-4 mol/l. The gratings recorded on the optimized film constitution could be stored for months with stable diffraction efficiency (24%) without any chemical or thermal fixing techniques. The resolution of the material is found to be unaffected with the addition of copper chloride.

Long-period grating fabricated by periodically tapering standard single-mode fiber.

PubMed

Shao, Li-Yang; Zhao, Jian; Dong, Xinyong; Tam, H Y; Lu, C; He, Sailing

2008-04-01

We fabricated an asymmetric long-period grating (LPG) by periodically tapering a section of standard single-mode fiber using a resistive filament heating. The LPG exhibits large peak transmission attenuation of -30.31 dB with only 22 periods in a 1.0 cm long optical fiber and possesses unique characteristics for sensing applications. The bending and strain sensitivities are 1.74 nm m and 1.11 pm/mu epsilon, respectively. The polarization dependent loss is large, up to 11.65 dB, which is caused by an asymmetric index profile in the cross section of the tapered LPG.

Spectrally-Narrowed Emissions from Organic Crystals Having a One-Dimensional Grating on Their Surface.

PubMed

Yamamoto, Hiroyuki; Obara, Keiji; Higashihara, Shohei; Obama, Yuki; Yamao, Takeshi; Hotta, Shu

2016-04-01

We have succeeded in directly engraving one-dimensional diffraction gratings on the surface of organic semiconducting oligomer crystals by using focused ion beam (FIB) lithography and laser ablation (LA) methods. The FIB method enabled us to shape the gratings with varying periods down to ~150 nm. With the LA method a large-area grating with a ~500-nm period was readily accessible. All the above crystals indicated spectrally-narrowed emission (SNE) lines even in the case of shallow groove depths ~2-4 nm. In particular, we definitively observed the SNE pertinent to the first-order diffraction with the crystal having the diffraction grating of a 148.3-nm average period. The present results indicate utility of the built-in gratings that can directly be fabricated on the surface of the crystals.

Optically transduced MEMS magnetometer

DOEpatents

Nielson, Gregory N; Langlois, Eric

2014-03-18

MEMS magnetometers with optically transduced resonator displacement are described herein. Improved sensitivity, crosstalk reduction, and extended dynamic range may be achieved with devices including a deflectable resonator suspended from the support, a first grating extending from the support and disposed over the resonator, a pair of drive electrodes to drive an alternating current through the resonator, and a second grating in the resonator overlapping the first grating to form a multi-layer grating having apertures that vary dimensionally in response to deflection occurring as the resonator mechanically resonates in a plane parallel to the first grating in the presence of a magnetic field as a function of the Lorentz force resulting from the alternating current. A plurality of such multi-layer gratings may be disposed across a length of the resonator to provide greater dynamic range and/or accommodate fabrication tolerances.

Optimal design and evaluation of a color separation grating using rigorous coupled wave analysis

NASA Astrophysics Data System (ADS)

Nagayoshi, Mayumi; Oka, Keiko; Klaus, Werner; Komai, Yuki; Kodate, Kashiko

2006-02-01

In recent years, the technology which separates white light into the three primary colors of Red (R), Green (G) and Blue (B) and adjusts each optical intensity and composites R, G and B to display various colors is required in the development and spread of color visual equipments. Various color separation devices have been proposed and have been put to practical use in color visual equipments. We have focused on a small and light grating-type device which has the possibility of reduction in cost and large-scale production and generates only the three primary colors of R, G and B so that a high saturation level can be obtained. To perform a rigorous analysis and design of color separation gratings, our group has developed a program that is based on the Rigorous Coupled Wave Analysis (RCWA). We then calculated the parameters to obtain a diffraction efficiency of higher than 70% and the color gamut of about 70%. We will report on the design, fabrication and evaluation of color separation gratings that have been optimized for fabrication by laser drawing.

Design and fabrication of a metamaterial gradient index diffraction grating at infrared wavelengths.

PubMed

Tsai, Yu-Ju; Larouche, Stéphane; Tyler, Talmage; Lipworth, Guy; Jokerst, Nan M; Smith, David R

2011-11-21

We demonstrate the design, fabrication and characterization of an artificially structured, gradient index metamaterial with a linear index variation of Δn ~ 3.0. The linear gradient profile is repeated periodically to form the equivalent of a blazed grating, with the gradient occurring across a spatial distance of 61 μm. The grating, which operates at a wavelength of 10.6 μm, is composed of non-resonant, progressively modified "I-beam" metamaterial elements and approximates a linear phase shift gradient using 61 distinguishable phase levels. The grating structure consists of four layers of lithographically patterned metallic I-beam elements separated by dielectric layers of SiO(2). The index gradient is confirmed by comparing the measured magnitudes of the -1, 0 and +1 diffracted orders to those obtained from full wave simulations incorporating all material properties of the metals and dielectrics of the structures. The large index gradient has the potential to enable compact infrared diffractive and gradient index optics, as well as more exotic transformation optical media. © 2011 Optical Society of America

Real-time sensing of optical alignment

NASA Technical Reports Server (NTRS)

Stier, Mark T.; Wissinger, Alan B.

1988-01-01

The Large Deployable Reflector and other future segmented optical systems may require autonomous, real-time alignment of their optical surfaces. Researchers have developed gratings located directly on a mirror surface to provide interferometric sensing of the location and figure of the mirror. The grating diffracts a small portion of the incident beam to a diffractive focus where the designed diagnostics can be performed. Mirrors with diffraction gratings were fabricated in two separate ways. The formation of a holographic grating over the entire surface of a mirror, thereby forming a Zone Plate Mirror (ZPM) is described. Researchers have also used computer-generated hologram (CGH) patches for alignment and figure sensing of mirrors. When appropriately illuminated, a grid of patches spread over a mirror segment will yield a grid of point images at a wavefront sensor, with the relative location of the points providing information on the figure and location of the mirror. A particular advantage of using the CGH approach is that the holographic patches can be computed, fabricated, and replicated on a mirror segment in a mass production 1-g clean room environment.

Graphene electrodes for lithium-niobate electro-optic devices.

PubMed

Chang, Zeshan; Jin, Wei; Chiang, Kin Seng

2018-04-15

We propose and demonstrate the use of graphene electrodes for lithium-niobate electro-optic (EO) devices to exempt the need of incorporating a buffer layer between the waveguide and the electrodes. Using graphene electrodes, our experimental mode converter, based on an EO-generated long-period grating in a LiNbO 3 waveguide, shows a reduction in the half-π voltage by almost three times, compared with the conventional electrode design using metal. With the buffer layer exempted, the device fabrication process is also significantly simplified. The use of graphene electrodes is an effective approach to enhancing the efficiency of EO devices and, at the same time, reducing their fabrication cost.

Femtosecond laser-induced periodic structure adjustments based on electron dynamics control: from subwavelength ripples to double-grating structures.

PubMed

Shi, Xuesong; Jiang, Lan; Li, Xin; Wang, Sumei; Yuan, Yanping; Lu, Yongfeng

2013-10-01

This study proposes a method for adjusting subwavelength ripple periods and the corresponding double-grating structures formed on fused silica by designing femtosecond laser pulse trains based on localized transient electron density control. Four near-constant period ranges of 190-490 nm of ripples perpendicular to the polarization are obtained by designing pulse trains to excite and modulate the surface plasmon waves. In the period range of 350-490 nm, the double-grating structure is fabricated in one step, which is probably attributable to the grating-assisted enhanced energy deposition and subsequent thermal effects.

Holographic Reflection Filters in Photorefractive LiNbO3 Channel Waveguides

NASA Astrophysics Data System (ADS)

Kip, Detlef; Hukriede, Joerg

Permanent refractive-index gratings in waveguide devices are of considerable interest for optical communication systems that make use of the high spectral selectivity of holographic filters, e.g. dense wavelength division multiplexing (DWDM) or narrow-bandwidth mirrors for integrated waveguide lasers in LiNbO3. Other possible applications include grating couplers and optical sensors. In this contribution we investigate such holographic wavelength filters in Fe- and Cu-doped LiNbO3 channel waveguides. Permanent refractive-index gratings are generated by thermal fixing of holograms in the waveguides. The samples are fabricated by successive in-diffusion of Ti stripes and thin layers of either Fe or Cu. After high-temperature recording with green light, refractive-index changes up to δ, ~10^-4 for infrared light ( 1.55,m) are obtained, resulting in a reflection efficiency well above 99% for a 15 mm-long grating. Several gratings for different wavelengths can be superimposed in the same sample, which may enable the fabrication of more complex filters, laser mirrors or optical sensors. By changing the sample temperature the reflection wavelength can be tuned by thermal expansion of the grating, and wavelength filters can be switched on and off by applying moderate voltages using the electro-optic effect. Furthermore, we report on a new thermal fixing mechanism that does not need any additional development by homogeneous light illumination and therefore does not suffer from the non-vanishing dark conductivity of the material.

Optical fiber endface biosensor based on resonances in dielectric waveguide gratings

NASA Astrophysics Data System (ADS)

Wawro, Debra D.; Tibuleac, Sorin; Magnusson, Robert; Liu, Hanli

2000-05-01

A new fiber optic sensor integrating dielectric diffraction gratings and thin films on optical fiber endfaces is prosed for biomedical sensing applications. This device utilizes a resonant dielectric waveguide grating structure fabricated on an optical fiber endface to probe reactions occurring in a sensing layer deposited on its surface. The operation of this sensor is based upon a fundamental resonance effect that occurs in waveguide gratings. An incident broad- spectrum signal is guided within an optical fiber and is filtered to reflect or transmit a desired spectral band by the diffractive thin film structure on its endface. Slight changes in one or more parameters of the waveguide grating, such as refractive index or thickness, can result in a responsive shift of the reflected or transmitted spectral peak that can be detected with spectroscopic instruments. This new sensor concept combines improved sensitivity and accuracy with attractive features found separately in currently available fiber optic sensors, such as large dynamic range, small sensing proximity, real time operation, and remote sensing. Diffractive elements of this type consisting of a photoresist grating on a Si3N4 waveguide have been fabricated on multimode optical fiber endfaces with 100 micrometers cores. Preliminary experimental tests using a tunable Ti:sapphire laser indicate notches of 18 percent in the transmission spectrum of the fiber endface guided-mode resonance devices. A theoretical analysis of the device performance capabilities is presented and applied to evaluate the feasibility and potential advantages of this bioprobe.

Subwavelength Gold Grating as Polarizers Integrated with InP-Based InGaAs Sensors.

PubMed

Wang, Rui; Li, Tao; Shao, Xiumei; Li, Xue; Huang, Xiaqi; Shao, Jinhai; Chen, Yifang; Gong, Haimei

2015-07-08

There are currently growing needs for polarimetric imaging in infrared wavelengths for broad applications in bioscience, communications and agriculture, etc. Subwavelength metallic gratings are capable of separating transverse magnetic (TM) mode from transverse electric (TE) mode to form polarized light, offering a reliable approach for the detection in polarization way. This work aims to design and fabricate subwavelength gold gratings as polarizers for InP-based InGaAs sensors in 1.0-1.6 μm. The polarization capability of gold gratings on InP substrate with pitches in the range of 200-1200 nm (fixed duty cycle of 0.5) has been systematically studied by both theoretical modeling with a finite-difference time-domain (FDTD) simulator and spectral measurements. Gratings with 200 nm lines/space in 100-nm-thick gold have been fabricated by electron beam lithography (EBL). It was found that subwavelength gold gratings directly integrated on InP cannot be applied as good polarizers, because of the existence of SPP modes in the detection wavelengths. An effective solution has been found by sandwiching the Au/InP bilayer using a 200 nm SiO2 layer, leading to significant improvement in both TM transmission and extinction ratio. At 1.35 μm, the improvement factors are 8 and 10, respectively. Therefore, it is concluded that the Au/SiO2/InP trilayer should be a promising candidate of near-infrared polarizers for the InP-based InGaAs sensors.

Diffraction efficiency of radially-profiled off-plane reflection gratings

NASA Astrophysics Data System (ADS)

Miles, Drew M.; Tutt, James H.; DeRoo, Casey T.; Marlowe, Hannah; Peterson, Thomas J.; McEntaffer, Randall L.; Menz, Benedikt; Burwitz, Vadim; Hartner, Gisela; Laubis, Christian; Scholze, Frank

2015-09-01

Future X-ray missions will require gratings with high throughput and high spectral resolution. Blazed off-plane reflection gratings are capable of meeting these demands. A blazed grating profile optimizes grating efficiency, providing higher throughput to one side of zero-order on the arc of diffraction. This paper presents efficiency measurements made in the 0.3 - 1.5 keV energy band at the Physikalisch-Technische Bundesanstalt (PTB) BESSY II facility for three holographically-ruled gratings, two of which are blazed. Each blazed grating was tested in both the Littrow configuration and anti-Littrow configuration in order to test the alignment sensitivity of these gratings with regard to throughput. This paper outlines the procedure of the grating experiment performed at BESSY II and discuss the resulting efficiency measurements across various energies. Experimental results are generally consistent with theory and demonstrate that the blaze does increase throughput to one side of zero-order. However, the total efficiency of the non-blazed, sinusoidal grating is greater than that of the blazed gratings, which suggests that the method of manufacturing these blazed profiles fails to produce facets with the desired level of precision. Finally, evidence of a successful blaze implementation from first diffraction results of prototype blazed gratings produce via a new fabrication technique at the University of Iowa are presented.

Holographic rugate structures for x-ray optics applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jannson, T.; Savant, G.

1990-03-19

Physical Optics Corporation (POC) has proposed and investigated a novel approach to x-ray optics during this DOE-sponsored three-year program, based on our well-established technologies in volume holography and holographic materials. With these technologies, a majority of conventional XUV optical elements, such as uniform and nonuniform gratings/multilayers, lenses, slanted (non-Snellian) mirrors, Fresnel zone-plates, concentrators/collimators, beam splitters, Fabry-Perot etalons, and binary optical elements, can be fabricated using a unified, low cost process. Furthermore, volume holography offer nonconventional optical elements, such as x-ray holographic optical elements (HOEs) with any desirable wavefront formation characteristics and multiple gratings multiplexed in the same volume to performmore » different operations for different wavelengths, that are difficult or even impossible to produce with the existing technologies.« less

Nanoimprinted ultrafine line and space nanogratings for liquid crystal alignment.

PubMed

Liu, Yan Jun; Loh, Wei Wei; Leong, Eunice Sok Ping; Kustandi, Tanu Suryadi; Sun, Xiao Wei; Teng, Jing Hua

2012-11-23

Ultrafine 50 nm line and space nanogratings were fabricated using nanoimprint lithography, and were further used as an alignment layer for liquid crystals. The surface morphologies of the nanogratings were characterized and their surface energies were estimated through the measurement of the contact angles for two different liquids. Experimental results show that the surface energies of the nanogratings are anisotropic: the surface free energy towards the direction parallel to the grating lines is higher than that in the direction perpendicular to the grating lines. Electro-optical characteristics were tested from a twisted nematic liquid crystal cell, which was assembled using two identical nanogratings. Experimental results show that such a kind of nanograting is promising as an alternative to the conventional rubbing process for liquid crystal alignment.

Plasmonic structure: fiber grating formed by gold nanorods on a tapered fiber.

PubMed

Trevisanutto, J O; Linhananta, A; Das, G

2016-12-15

The authors demonstrated the fabrication of a fiber Bragg grating-like plasmonic nanostructure on the surface of a tapered optical fiber using gold nanorods (GNRs). A multimode optical fiber with core and cladding diameters of 105 and 125 μm, respectively, was used to make a tapered fiber using a dynamic etching process. The tip diameter was ∼100  nm. Light from a laser was coupled to the untapered end of the fiber, which produced a strong evanescent field around the tapered section of the fiber. The gradient force due to the evanescent field trapped the GNRs on the surface of the tapered fiber. The authors explored possible causes of the GNR distribution. The plasmonic structure will be a good candidate for sensing based on surface enhanced Raman scattering.

Astronomical large Ge immersion grating by Canon

NASA Astrophysics Data System (ADS)

Sukegawa, Takashi; Suzuki, Takeshi; Kitamura, Tsuyoshi

2016-07-01

Immersion grating is a powerful optical device for thee infrared high-resolution spectroscope. Germanium (GGe) is the best material for a mid-infrared immersion grating because of Ge has very large reflective index (n=4.0). On the other hands, there is no practical Ge immersion grating under 5umm use. It was very difficult for a fragile IR crystal to manufacture a diffraction grating precisely. Our original free-forming machine has accuracy of a few nano-meter in positioning and stability. We already fabricated the large CdZnTe immersion grating. (Sukegawa et al. (2012), Ikeda et al. (2015)) Wee are developing Ge immersion grating that can be a good solution for high-resolution infrared spectroscopy with the large ground-based/space telescopes. We succeeded practical Ge immersion grating with the grooved area off 75mm (ruled direction) x 119mm (grove width) and the blaze angle of 75 degrees. Our astronomical large Ge immersion grating has the grooved area of 155mm (ruled direction) x 41mmm (groove width) and groove pitch off 91.74um. We also report optical performance of astronomical large Ge immersion grating with a metal coating on the diffraction surface.

Some Improvements in H-PDLCs

NASA Technical Reports Server (NTRS)

Crawford, Gregory P.; Li, Liuliu

2005-01-01

Some improvements have been made in the formulation of holographically formed polymer-dispersed liquid crystals (H-PDLCs) and in the fabrication of devices made from these materials, with resulting improvements in performance. H-PDLCs are essentially volume Bragg gratings. Devices made from H-PDLCs function as electrically switchable reflective filters. Heretofore, it has been necessary to apply undesirably high drive voltages in order to switch H-PDLC devices. Many scientific papers on H-PDLCs and on the potential utility of H-PDLC devices for display and telecommunication applications have been published. However, until now, little has been published about improving quality control in synthesis of H-PDLCs and fabrication of H-PDLC devices to minimize (1) spatial nonuniformities within individual devices, (2) nonuniformities among nominally identical devices, and (3) variations in performance among nominally identical devices. The improvements reported here are results of a research effort directed partly toward solving these quality-control problems and partly toward reducing switching voltages. The quality-control improvements include incorporation of a number of process controls to create a relatively robust process, such that the H-PDLC devices fabricated in this process are more nearly uniform than were those fabricated in a prior laboratory-type process. The improved process includes ultrasonic mixing, ultrasonic cleaning, the use of a micro dispensing technique, and the use of a bubble press.

[Computer aided design and manufacture of the porcelain fused to metal crown].

PubMed

Nie, Xin; Cheng, Xiaosheng; Dai, Ning; Yu, Qing; Hao, Guodong; Sun, Quanping

2009-04-01

In order to satisfy the current demand for fast and high-quality prosthodontics, we have carried out a research in the fabrication process of the porcelain fused to metal crown on molar with CAD/CAM technology. Firstly, we get the data of the surface mesh on preparation teeth through a 3D-optical grating measuring system. Then, we reconstruct the 3D-model crown with the computer-aided design software which was developed by ourselves. Finally, with the 3D-model data, we produce a metallic crown on a high-speed CNC carving machine. The result has proved that the metallic crown can match the preparation teeth ideally. The fabrication process is reliable and efficient, and the restoration is precise and steady in quality.

Experimental Demonstration of a Highly Efficient Fan-out Polarization Grating

PubMed Central

Wan, Chenhao; Chen, Jian; Tang, Xiahui; Zhan, Qiwen

2016-01-01

Highly efficient fan-out elements are crucial in coherent beam combining architectures especially in coupled laser resonators where the beam passes through the fan-out element twice per round trip. Although the theoretical efficiency is usually less than 86%, the Dammann gratings are ubiquitously utilized in a variety of types of coherent beam combining systems due to the facile design and fabrication. In the current paper, we experimentally demonstrate a highly efficient fan-out polarization grating. It is the first time to our knowledge that all the three space-variant parameters of a polarization grating are simultaneously optimized to achieve the function of multi-beam splitting. Besides the high fan-out efficiency, the ability to control the polarization states of individual split beams is another advantage of this polarization grating. The novel polarization grating is promising to find applications in laser beam combining systems. PMID:28008972

Inscription of first order fiber Bragg gratings in sapphire fibers by 400 nm femtosecond laser pulses

NASA Astrophysics Data System (ADS)

Elsmann, Tino; Habisreuther, Tobias; Graf, Albrecht; Rothhardt, Manfred; Bartelt, Hartmut

2013-05-01

We demonstrate the inscription of fiber Bragg gratings in single crystalline sapphire using the second harmonic of a Ti:Sa-amplified femtosecond laser system. With the laser wavelength of 400 nm first order gratings were fabricated. The interferometric inscription was performed out using the Talbot interferometer. This way, not only single gratings but also multiplexed sensor arrays were realized. For evaluating of the sensor signals an adapted multimodal interrogation setup was build up, because the sapphire fiber is an extreme multimodal air clad fiber. Due to the multimodal reflection spectrum, different peak functions have been tested to evaluate the thermal properties of the grating. The temperature sensors were tested for high temperature applications up to 1200°C with a thermal sensitivity in the order of 25 pm/K which is more than the doubled of that one reached with Bragg gratings in conventional silica fibers.

Direct writing of large-area plasmonic photonic crystals using single-shot interference ablation.

PubMed

Pang, Zhaoguang; Zhang, Xinping

2011-04-08

We report direct writing of metallic photonic crystals (MPCs) through a single-shot exposure of a thin film of colloidal gold nanoparticles to the interference pattern of a single UV laser pulse before a subsequent annealing process. This is defined as interference ablation, where the colloidal gold nanoparticles illuminated by the bright interference fringes are removed instantly within a timescale of about 6 ns, which is actually the pulse length of the UV laser, whereas the gold nanoparticles located within the dark interference fringes remain on the substrate and form grating structures. This kind of ablation has been proven to have a high spatial resolution and thus enables successful fabrication of waveguided MPC structures with the optical response in the visible spectral range. The subsequent annealing process transforms the grating structures consisting of ligand-covered gold nanoparticles into plasmonic MPCs. The annealing temperature is optimized to a range from 250 to 300 °C to produce MPCs of gold nanowires with a period of 300 nm and an effective area of 5 mm in diameter. If the sample of the spin-coated gold nanoparticles is rotated by 90° after the first exposure, true two-dimensional plasmonic MPCs are produced through a second exposure to the interference pattern. Strong plasmonic resonance and its coupling with the photonic modes of the waveguided MPCs verifies the success of this new fabrication technique. This is the simplest and most efficient technique so far for the construction of large-area MPC devices, which enables true mass fabrication of plasmonic devices with high reproducibility and high success rate.

Direct writing of large-area plasmonic photonic crystals using single-shot interference ablation

NASA Astrophysics Data System (ADS)

Pang, Zhaoguang; Zhang, Xinping

2011-04-01

We report direct writing of metallic photonic crystals (MPCs) through a single-shot exposure of a thin film of colloidal gold nanoparticles to the interference pattern of a single UV laser pulse before a subsequent annealing process. This is defined as interference ablation, where the colloidal gold nanoparticles illuminated by the bright interference fringes are removed instantly within a timescale of about 6 ns, which is actually the pulse length of the UV laser, whereas the gold nanoparticles located within the dark interference fringes remain on the substrate and form grating structures. This kind of ablation has been proven to have a high spatial resolution and thus enables successful fabrication of waveguided MPC structures with the optical response in the visible spectral range. The subsequent annealing process transforms the grating structures consisting of ligand-covered gold nanoparticles into plasmonic MPCs. The annealing temperature is optimized to a range from 250 to 300 °C to produce MPCs of gold nanowires with a period of 300 nm and an effective area of 5 mm in diameter. If the sample of the spin-coated gold nanoparticles is rotated by 90° after the first exposure, true two-dimensional plasmonic MPCs are produced through a second exposure to the interference pattern. Strong plasmonic resonance and its coupling with the photonic modes of the waveguided MPCs verifies the success of this new fabrication technique. This is the simplest and most efficient technique so far for the construction of large-area MPC devices, which enables true mass fabrication of plasmonic devices with high reproducibility and high success rate.

Multi-tap complex-coefficient incoherent microwave photonic filters based on optical single-sideband modulation and narrow band optical filtering.

PubMed

Sagues, Mikel; García Olcina, Raimundo; Loayssa, Alayn; Sales, Salvador; Capmany, José

2008-01-07

We propose a novel scheme to implement tunable multi-tap complex coefficient filters based on optical single sideband modulation and narrow band optical filtering. A four tap filter is experimentally demonstrated to highlight the enhanced tuning performance provided by complex coefficients. Optical processing is performed by the use of a cascade of four phase-shifted fiber Bragg gratings specifically fabricated for this purpose.

Periodical rocking long period gratings in PANDA fibers for high temperature and refractive index sensing

NASA Astrophysics Data System (ADS)

Jin, Wa; Bi, Wei-hong; Fu, Xing-hu; Fu, Guang-wei

2017-09-01

We report periodical rocking long period gratings (PR-LPGs) in PANDA fibers fabricated with CO2 laser. The PR-LPGs achieve very high coupling efficiency of 19 dB with 12 periods and a 3.5° twist angle in just one scanning cycle, which is much more effective than the conventional CO2 laser fabrication technique. This type of LPGs exhibits polarization-selective resonance dips which demonstrate different sensitivities to environmental parameters. The high temperature and external refractive index sensitivities are measured simultaneously, so it can be used as a wavelength-selective polarization filter and sensor.

Fiber optic micro sensor for the measurement of tendon forces

PubMed Central

2012-01-01

A fiber optic sensor developed for the measurement of tendon forces was designed, numerically modeled, fabricated, and experimentally evaluated. The sensor incorporated fiber Bragg gratings and micro-fabricated stainless steel housings. A fiber Bragg grating is an optical device that is spectrally sensitive to axial strain. Stainless steel housings were designed to convert radial forces applied to the housing into axial forces that could be sensed by the fiber Bragg grating. The metal housings were fabricated by several methods including laser micromachining, swaging, and hydroforming. Designs are presented that allow for simultaneous temperature and force measurements as well as for simultaneous resolution of multi-axis forces. The sensor was experimentally evaluated by hydrostatic loading and in vitro testing. A commercial hydraulic burst tester was used to provide uniform pressures on the sensor in order to establish the linearity, repeatability, and accuracy characteristics of the sensor. The in vitro experiments were performed in excised tendon and in a dynamic gait simulator to simulate biological conditions. In both experimental conditions, the sensor was found to be a sensitive and reliable method for acquiring minimally invasive measurements of soft tissue forces. Our results suggest that this sensor will prove useful in a variety of biomechanical measurements. PMID:23033868

High resolution on-chip optical filter array based on double subwavelength grating reflectors

DOE PAGES

Horie, Yu; Arbabi, Amir; Han, Seunghoon; ...

2015-11-05

An optical filter array consisting of vertical narrow-band Fabry-Pèrot (FP) resonators formed by two highly reflective high contrast subwavelength grating mirrors is reported. The filters are designed to cover a wide range of operation wavelengths ( Δλ/λ=5%) just by changing the in-plane grating parameters while the device thickness is maintained constant. In conclusion, operation in the telecom band with transmission efficiencies greater than 40% and quality factors greater than 1,000 are measured experimentally for filters fabricated on the same substrate.

Electro-optical tunable waveguide embedded multiscan Bragg gratings in lithium niobate by direct femtosecond laser writing.

PubMed

Kroesen, Sebastian; Horn, Wolfgang; Imbrock, Jörg; Denz, Cornelia

2014-09-22

optical tunable Bragg gratings in lithium niobate fabricated by direct femtosecond laser writing. The hybrid design that consists of a circular type-II waveguide and a multiscan type-I Bragg grating exhibits low loss ordinary and extraordinary polarized guiding as well as narrowband reflections in the c-band of optical communications. High bandwidth tunability of more than a peak width and nearly preserved electro-optic coefficients of r(13) = 7.59 pm V(-1) and r(33) = 23.21 pm V(-1) are demonstrated.

High resolution on-chip optical filter array based on double subwavelength grating reflectors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Horie, Yu; Arbabi, Amir; Han, Seunghoon

An optical filter array consisting of vertical narrow-band Fabry-Pèrot (FP) resonators formed by two highly reflective high contrast subwavelength grating mirrors is reported. The filters are designed to cover a wide range of operation wavelengths ( Δλ/λ=5%) just by changing the in-plane grating parameters while the device thickness is maintained constant. In conclusion, operation in the telecom band with transmission efficiencies greater than 40% and quality factors greater than 1,000 are measured experimentally for filters fabricated on the same substrate.

Fabrication of Fiber Optic Grating Apparatus and Method

NASA Technical Reports Server (NTRS)

Wang, Ying (Inventor); Sharma, Anup (Inventor); Grant, Joseph (Inventor)

2005-01-01

An apparatus and method for forming a Bragg grating on an optical fiber using a phase mask to diffract a beam of coherent energy and a lens combined with a pair of mirrors to produce two symmetrical virtual point sources of coherent energy in the plane of the optical fiber. The two virtual light sources produce an interference pattern along the optical fiber. In a further embodiment, the period of the pattern and therefore the Bragg wavelength grating applied to the fiber is varied with the position of the optical fiber relative the lens.

Serial number coding and decoding by laser interference direct patterning on the original product surface for anti-counterfeiting.

PubMed

Park, In-Yong; Ahn, Sanghoon; Kim, Youngduk; Bae, Han-Sung; Kang, Hee-Shin; Yoo, Jason; Noh, Jiwhan

2017-06-26

Here, we investigate a method to distinguish the counterfeits by patterning multiple reflective type grating directly on the surface of the original product and analyze the serial number from its rotation angles of diffracted fringes. The micro-sized gratings were fabricated on the surface of the material at high speeds by illuminating the interference fringe generated by passing a high-energy pulse laser through the Fresnel biprism. In addition, analysis of the grating's diffraction fringes was performed using a continuous wave laser.

Optical and x-ray alignment approaches for off-plane reflection gratings

NASA Astrophysics Data System (ADS)

Allured, Ryan; Donovan, Benjamin D.; DeRoo, Casey T.; Marlowe, Hannah R.; McEntaffer, Randall L.; Tutt, James H.; Cheimets, Peter N.; Hertz, Edward; Smith, Randall K.; Burwitz, Vadim; Hartner, Gisela; Menz, Benedikt

2015-09-01

Off-plane reflection gratings offer the potential for high-resolution, high-throughput X-ray spectroscopy on future missions. Typically, the gratings are placed in the path of a converging beam from an X-ray telescope. In the off-plane reflection grating case, these gratings must be co-aligned such that their diffracted spectra overlap at the focal plane. Misalignments degrade spectral resolution and effective area. In-situ X-ray alignment of a pair of off-plane reflection gratings in the path of a silicon pore optics module has been performed at the MPE PANTER beamline in Germany. However, in-situ X-ray alignment may not be feasible when assembling all of the gratings required for a satellite mission. In that event, optical methods must be developed to achieve spectral alignment. We have developed an alignment approach utilizing a Shack-Hartmann wavefront sensor and diffraction of an ultraviolet laser. We are fabricating the necessary hardware, and will be taking a prototype grating module to an X-ray beamline for performance testing following assembly and alignment.

Hybrid III-V on Si grating as a broadband reflector and a high-Q resonator

NASA Astrophysics Data System (ADS)

Chung, Il-Sug; Taghizadeh, Alireza; Park, Gyeong Cheol

2016-03-01

Hybrid grating (HG) with a high-refractive-index cap layer added onto a high contrast grating (HCG), can provide a high reflectance close 100 % over a broader wavelength range than HCGs, or work as a ultrahigh quality (Q) factor resonator. The reflection and resonance properties of HGs have been investigated and the mechanisms leading to these properties are discussed. A HG reflector sample integrating a III-V cap layer with InGaAlAs quantum wells onto a Si grating has been fabricated and its reflection property has been characterized. The HG-based lasers have a promising prospect for silicon photonics light source or high-speed laser applications.

Integrated otpical monitoring of MEMS for closed-loop control

NASA Astrophysics Data System (ADS)

Dawson, Jeremy M.; Wang, Limin; McCormick, W. B.; Rittenhouse, S. A.; Famouri, Parviz F.; Hornak, Lawrence A.

2003-01-01

Robust control and failure assessment of MEMS employed in physically demanding, mission critical applications will allow for higher degrees of quality assurance in MEMS operation. Device fault detection and closed-loop control require detailed knowledge of the operational states of MEMS over the lifetime of the device, obtained by a means decoupled from the system. Preliminary through-wafer optical monitoring research efforts have shown that through-wafer optical probing is suitable for characterizing and monitoring the behavior of MEMS, and can be implemented in an integrated optical monitoring package for continuous in-situ device monitoring. This presentation will discuss research undertaken to establish integrated optical device metrology for closed-loop control of a MUMPS fabricated lateral harmonic oscillator. Successful linear closed-loop control results using a through-wafer optical microprobe position feedback signal will be presented. A theoretical optical output field intensity study of grating structures, fabricated on the shuttle of the resonator, was performed to improve the position resolution of the optical microprobe position signal. Through-wafer microprobe signals providing a positional resolution of 2 μm using grating structures will be shown, along with initial binary Fresnel diffractive optical microelement design layout, process development, and testing results. Progress in the design, fabrication, and test of integrated optical elements for multiple microprobe signal delivery and recovery will be discussed, as well as simulation of device system model parameter changes for failure assessment.

Design and characterization of a hybrid-integrated MEMS scanning grating spectrometer

NASA Astrophysics Data System (ADS)

Grüger, Heinrich; Knobbe, Jens; Pügner, Tino; Schenk, Harald

2013-03-01

Grating spectrometer, like the well-established Czerny-Turner, are based on an optical design consisting of several components. Typically at least two slits, two mirrors, the grating stage and a detector are required. There has been much work to reduce this effort, setups using only one mirror (Ebert - Fastie) or the replacement of the entrance slit through the use of thin optical fibers as well as integrated electronic detector arrays instead of a moving grating and an exit slit and single detector device have been applied. Reduced effort comes along with performance limitations: Either the optical resolution or throughput is affected or the use of the system is limited to the availability of detectors arrays with reasonable price. Components in micro opto electro mechanical systems (MOEMS-) technology and spectroscopic systems based thereon have been developed to improve this situation. Miniaturized scanning gratings fabricated on bonded silicon on insulator (BSOI-) wafers were used to design grating spectrometer for the near infrared requiring single detectors only. Discrete components offer flexibility but also need for adjustment of two mirrors, grating stage, fiber mount and the detector with its slit and optionally a second slit in the entrance area. Further development leads towards the integration of the slits into the MOEMS chip, thus less effort for adjustment. Flexibility might be reduced as adjustments of the optical design or grating spacing would require a new chip with own set of masks. Nevertheless if extreme miniaturization is desired this approach seems to be promising. Besides this, high volume production might be able for a comparable low price. A new chip was developed offering grating, two slits and a cavity for the detector chip. The optical design was adjusted to a planar arrangement of grating and slits. A detector buried in a chip cavity required a new mounting strategy. Other optical components were optimized and fabricated then the systems was assembled with electronics and software adjusted to the new design including some new features like integrated position sensors. A first test of systems to grant function of all components is presented. Further work will be aimed at improved performance like higher resolution and lower SNR.

Femtosecond laser fabrication of long period fiber gratings and applications in refractive index sensing

NASA Astrophysics Data System (ADS)

Li, Benye; Jiang, Lan; Wang, Sumei; Tsai, Hai-Lung; Xiao, Hai

2011-11-01

An improved point-by-point inscription method is proposed to fabricate long period fiber gratings (LPFGs) by using a laser operating at 800 nm with 35 fs duration pulses. The sensitivity to misalignment between the core and the focus is reduced by scanning a rectangular part on the fiber. LPFGs with an attenuation depth of 20 dB are achieved within the wavelength range of 1465-1575 nm. Characterization of the temperature sensitivity and thermal stability of the LPFGs is presented. A 5.6 nm wavelength shift and a 1.2 dB decrease in the attenuation peak are observed following heat treatment at 600 °C for 4 h. The fabricated LPFGs are used as refractive index sensors. The effect of heat treatment on the response of the LPFGs to refractive index changes is also studied.

High-energy x-ray grating-based phase-contrast radiography of human anatomy

NASA Astrophysics Data System (ADS)

Horn, Florian; Hauke, Christian; Lachner, Sebastian; Ludwig, Veronika; Pelzer, Georg; Rieger, Jens; Schuster, Max; Seifert, Maria; Wandner, Johannes; Wolf, Andreas; Michel, Thilo; Anton, Gisela

2016-03-01

X-ray grating-based phase-contrast Talbot-Lau interferometry is a promising imaging technology that has the potential to raise soft tissue contrast in comparison to conventional attenuation-based imaging. Additionally, it is sensitive to attenuation, refraction and scattering of the radiation and thus provides complementary and otherwise inaccessible information due to the dark-field image, which shows the sub-pixel size granularity of the measured object. Until recent progress the method has been mainly limited to photon energies below 40 keV. Scaling the method to photon energies that are sufficient to pass large and spacious objects represents a challenging task. This is caused by increasing demands regarding the fabrication process of the gratings and the broad spectra that come along with the use of polychromatic X-ray sources operated at high acceleration voltages. We designed a setup that is capable to reach high visibilities in the range from 50 to 120 kV. Therefore, spacious and dense parts of the human body with high attenuation can be measured, such as a human knee. The authors will show investigations on the resulting attenuation, differential phase-contrast and dark-field images. The images experimentally show that X-ray grating-based phase-contrast radiography is feasible with highly absorbing parts of the human body containing massive bones.

A MEMS torsion magnetic sensor with reflective blazed grating integration

NASA Astrophysics Data System (ADS)

Long, Liang; Zhong, Shaolong

2016-07-01

A novel magnetic sensor based on a permanent magnet and blazed grating is presented in this paper. The magnetic field is detected by measuring the diffracted wavelength of the blazed grating which is changed by the torsion motion of a torsion sensitive micro-electromechanical system (MEMS) structure with a permanent magnet attached. A V-shape grating structure is obtained by wet etching on a (1 0 0) SOI substrate. When the magnet is magnetized in different directions, the in-plane or out-of-plane magnetic field is detected by a sensor. The MEMS magnetic sensor with a permanent magnet is fabricated after analytical design and bulk micromachining processes. The magnetic-sensing capability of the sensor is tested by fiber-optic detection system. The result shows the sensitivities of the in-plane and out-of-plane magnetic fields are 3.6 pm μT-1 and 5.7 pm μT-1, respectively. Due to utilization of the permanent magnet and fiber-optic detection, the sensor shows excellent capability of covering the high-resolution detection of low-frequency signals. In addition, the sensitive direction of the magnetic sensor can be easily switched by varying the magnetized direction of the permanent magnet, which offers a simple way to achieve tri-axis magnetic sensor application.

Entrained-flow gasifier and fluidized-bed combustor temperature monitoring using arrays of fs-IR written fiber Bragg gratings

NASA Astrophysics Data System (ADS)

Walker, Robert B.; Ding, Huimin; Coulas, David; Grobnic, Dan; Mihailov, Stephen J.; Duchesne, Marc A.; Hughes, Robin W.; McCalden, David J.; Burchat, Ryan

2015-09-01

Femtosecond written fiber Bragg gratings, have shown great potential for sensing in extreme environments. This paper discusses the fabrication and deployment of several fs-IR written FBG arrays, for monitoring main-spool skin temperatures of an entrained-flow gasifier, as well as the internal temperature gradient of a fluidized bed combustor.

Molecular imprinted polymer-coated optical fiber sensor for the identification of low molecular weight molecules.

PubMed

Lépinay, Sandrine; Ianoul, Anatoli; Albert, Jacques

2014-10-01

A biomimetic optical probe for detecting low molecular weight molecules (maltol, 3-hydroxy-2-methyl-4H-pyran-4-one, molecular weight of 126.11 g/mol), was designed, fabricated, and characterized. The sensor couples a molecular imprinted polymer (MIP) and the Bragg grating refractometry technology into an optical fiber. The probe is fabricated first by inscribing tilted grating planes in the core of the fiber, and then by photopolymerization to immobilize a maltol imprinted MIP on the fiber cladding surface over the Bragg grating. The sensor response to the presence of maltol in different media is obtained by spectral interrogation of the fiber transmission signal. The results showed that the limit of detection of the sensor reached 1 ng/mL in pure water with a sensitivity of 6.3 × 10(8)pm/M. The selectivity of the sensor against other compounds and its reusability were also studied experimentally. Finally, the unambiguous detection of concentrations as little as 10nM of maltol in complex media (real food samples) by the MIP-coated tilted fiber Bragg grating sensor was demonstrated. Copyright © 2014 Elsevier B.V. All rights reserved.

Photopatterned surface relief gratings in azobenzene-amorphous polycarbonate thin films

NASA Astrophysics Data System (ADS)

Vollmann, Morten; Getek, Peter; Olear, Kellie; Combs, Cody; Campos, Benjamin; Witkowski, Edmund; Cain, Erin; McGee, David

Photoinduced orientation of azobenzene chromophores in polymeric host materials has been broadly explored for optical processing applications. Illumination of the chromophore with polarized light rotates the trans isomer perpendicular to the polarization, resulting in spatially modulated birefringence. The photoinduced anisotropy may also drive mass transport, with surface relief patterns being observed in a wide variety of systems. Here we report photoinduced birefringence in a guest-host system of Disperse Red 1- amorphous polycarbonate (DR1-APC). Birefringence was induced with a 490 nm laser and probed at 633 nm, with typical values of Δn = 0.01 in 2 micron thick films. Illumination of DR1-APC with intensity and/or polarization gratings also resulted in sinusoidal surface relief patterns with periodicity 1- 3 micron as controlled by the interbeam crossing angle of the 490 nm writing beams; the surface modulation was +/- 20 nm as measured by atomic force microscopy. Photopatterned DR1-APC is advantageous for applications given the ease of thin-film fabrication and the high glass transition temperature of APC, resulting in robust optically-induced surface gratings. We acknowledge support from NSF-DMR Award No. 1138416.

High-efficiency spectral purity filter for EUV lithography

DOEpatents

Chapman, Henry N [Livermore, CA

2006-05-23

An asymmetric-cut multilayer diffracts EUV light. A multilayer cut at an angle has the same properties as a blazed grating, and has been demonstrated to have near-perfect performance. Instead of having to nano-fabricate a grating structure with imperfections no greater than several tens of nanometers, a thick multilayer is grown on a substrate and then cut at an inclined angle using coarse and inexpensive methods. Effective grating periods can be produced this way that are 10 to 100 times smaller than those produced today, and the diffraction efficiency of these asymmetric multilayers is higher than conventional gratings. Besides their ease of manufacture, the use of an asymmetric multilayer as a spectral purity filter does not require that the design of an EUV optical system be modified in any way, unlike the proposed use of blazed gratings for such systems.

Low-loss, submicron chalcogenide integrated photonics with chlorine plasma etching

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chiles, Jeff; Malinowski, Marcin; Rao, Ashutosh

A chlorine plasma etching-based method for the fabrication of high-performance chalcogenide-based integrated photonics on silicon substrates is presented. By optimizing the etching conditions, chlorine plasma is employed to produce extremely low-roughness etched sidewalls on waveguides with minimal penalty to propagation loss. Using this fabrication method, microring resonators with record-high intrinsic Q-factors as high as 450 000 and a corresponding propagation loss as low as 0.42 dB/cm are demonstrated in submicron chalcogenide waveguides. Furthermore, the developed chlorine plasma etching process is utilized to demonstrate fiber-to-waveguide grating couplers in chalcogenide photonics with high power coupling efficiency of 37% for transverse-electric polarized modes.

Effect of AZO deposition on antireflective property of Si subwavelength grating structures

NASA Astrophysics Data System (ADS)

Leem, J. W.; Song, Y. M.; Lee, Y. T.; Yu, J. S.

2011-12-01

We investigate the effect of the aluminum-doped zinc oxide (AZO) deposition on the fabricated Si SWG structure on its antireflection characteristics for solar cell applications. The Si SWGs with the two-dimensional periodic nanostructure are fabricated by using holographic lithography and subsequent ICP etching process in SiCl4 plasma. For the antireflection analysis of AZO thin-film on the Si SWG structure, the optical reflectivity is measured experimentally. The maxima reflectance and its oscillation of the structure are significantly decreased on average than those of AZO thin-film on Si substrate over a wide wavelength range of 300-1100 nm, indicating average reflectance less than 4.5% with the maxima of <10%.

Application of a Fiber Optic Distributed Strain Sensor System to Woven E-Glass Composite

NASA Technical Reports Server (NTRS)

Anastasi, Robert F.; Lopatin, Craig

2001-01-01

A distributed strain sensing system utilizing a series of identically written Bragg gratings along an optical fiber is examined for potential application to Composite Armored Vehicle health monitoring. A vacuum assisted resin transfer molding process was used to fabricate a woven fabric E-glass/composite panel with an embedded fiber optic strain sensor. Test samples machined from the panel were mechanically tested in 4-point bending. Experimental results are presented that show the mechanical strain from foil strain gages comparing well to optical strain from the embedded sensors. Also, it was found that the distributed strain along the sample length was consistent with the loading configuration.

Phase-Shifted Eccentric Core Fiber Bragg Grating Fabricated by Electric Arc Discharge for Directional Bending Measurement.

PubMed

Ouyang, Yang; Liu, Jianxia; Xu, Xiaofeng; Zhao, Yujia; Zhou, Ai

2018-04-11

A phase-shifted eccentric core fiber Bragg grating (PS-ECFBG) fabricated by electric arc discharge (EAD) is presented and demonstrated. It is composed of a fraction of eccentric core fiber fusion spliced in between two pieces of commercial single mode fibers, where a PS-FBG was written. The EAD in this work could flexibly change the amount of phase-shift by changing the discharge number or discharge duration. Because of the offset location of the eccentric core and the ultra-narrow resonant peak of the PS-ECFBG, it has a higher accuracy for measuring the directional bend. The elongation and compression of the eccentric core keep the magnitude of phase shift still unchanged during the bending process. The bending sensitivities of the PS-ECFBG at two opposite most sensitive directions are 57.4 pm/m -1 and -51.5 pm/m -1 , respectively. Besides, the PS-ECFBG has the potential to be a tunable narrow bandpass filter, which has a wider bi-directional adjustable range because of the bending responses. The strain and temperature sensitivities of the PS-ECFBG are experimentally measured as well, which are 0.70 pm/με and 8.85 pm/°C, respectively.

Innovative diffraction gratings for high-resolution resonant inelastic soft x-ray scattering spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Voronov, D.L.; Warwick, T.; Gullikson, E. M.

2016-07-27

High-resolution Resonant Inelastic X-ray Scattering (RIXS) requires diffraction gratings with very exacting characteristics. The gratings should provide both very high dispersion and high efficiency which are conflicting requirements and extremely challenging to satisfy in the soft x-ray region for a traditional grazing incidence geometry. To achieve high dispersion one should increase the groove density of a grating; this however results in a diffraction angle beyond the critical angle range and results in drastic efficiency loss. The problem can be solved by use of multilayer coated blazed gratings (MBG). In this work we have investigated the diffraction characteristics of MBGs viamore » numerical simulations and have developed a procedure for optimization of grating design for a multiplexed high resolution imaging spectrometer for RIXS spectroscopy to be built in sector 6 at the Advanced Light Source (ALS). We found that highest diffraction efficiency can be achieved for gratings optimized for 4{sup th} or 5{sup th} order operation. Fabrication of such gratings is an extremely challenging technological problem. We present a first experimental prototype of these gratings and report its performance. High order and high line density gratings have the potential to be a revolutionary new optical element that should have great impact in the area of soft x-ray RIXS.« less

Chiral fiber sensors

NASA Astrophysics Data System (ADS)

Kopp, Victor I.; Churikov, Victor M.; Singer, Jonathan; Neugroschl, Daniel; Genack, Azriel Z.

2010-04-01

We have fabricated a variety of chiral fiber sensors by twisting one or more standard or custom optical fibers with noncircular or nonconcentric core as they pass though a miniature oven. The resulting structures are as stable as the glass material and can be produced with helical pitch ranging from microns to hundreds of microns. The polarization selectivity of the chiral gratings is determined by the geometry of the fiber cross section. Single helix structures are polarization insensitive, while double helix gratings interact only with a single optical polarization component. Both single and double helix gratings may function as a fiber long period grating, coupling core and cladding modes or as a diffraction grating scattering light from the fiber core out of the fiber. The resulting dips in the transmission spectrum are sensitive to fiber elongation, twist and temperature, and (in the case of the long period gratings) to the refractive index of the surrounding medium. The suitability of chiral gratings for sensing temperature, elongation, twist and liquid levels will be discussed. Gratings made of radiation sensitive glass can be used to measure the cumulative radiation dose, while gratings made of radiation-hardened glass are suitable for stable sensing of the environment in nuclear power plants. Excellent temperature stability up to 900°C is found in pure silica chiral diffraction grating sensors.

Diffraction Gratings for High-Intensity Laser Applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Britten, J

The scattering of light into wavelength-dependent discrete directions (orders) by a device exhibiting a periodic modulation of a physical attribute on a spatial scale similar to the wavelength of light has been the subject of study for over 200 years. Such a device is called a diffraction grating. Practical applications of diffraction gratings, mainly for spectroscopy, have been around for over 100 years. The importance of diffraction gratings in spectroscopy for the measurement of myriad properties of matter can hardly be overestimated. Since the advent of coherent light sources (lasers) in the 1960's, applications of diffraction gratings in spectroscopy havemore » further exploded. Lasers have opened a vast application space for gratings, and apace, gratings have enabled entirely new classes of laser systems. Excellent reviews of the history, fundamental properties, applications and manufacturing techniques of diffraction gratings up to the time of their publication can be found in the books by Hutley (1) and more recently Loewen and Popov (2). The limited scope of this chapter can hardly do justice to such a comprehensive subject, so the focus here will be narrowly limited to characteristics required for gratings suitable for high-power laser applications, and methods to fabricate them. A particular area of emphasis will be on maximally-efficient large-aperture gratings for short-pulse laser generation.« less

Fiber Bragg Grating Sensors toward Structural Health Monitoring in Composite Materials: Challenges and Solutions

PubMed Central

Kinet, Damien; Mégret, Patrice; Goossen, Keith W.; Qiu, Liang; Heider, Dirk; Caucheteur, Christophe

2014-01-01

Nowadays, smart composite materials embed miniaturized sensors for structural health monitoring (SHM) in order to mitigate the risk of failure due to an overload or to unwanted inhomogeneity resulting from the fabrication process. Optical fiber sensors, and more particularly fiber Bragg grating (FBG) sensors, outperform traditional sensor technologies, as they are lightweight, small in size and offer convenient multiplexing capabilities with remote operation. They have thus been extensively associated to composite materials to study their behavior for further SHM purposes. This paper reviews the main challenges arising from the use of FBGs in composite materials. The focus will be made on issues related to temperature-strain discrimination, demodulation of the amplitude spectrum during and after the curing process as well as connection between the embedded optical fibers and the surroundings. The main strategies developed in each of these three topics will be summarized and compared, demonstrating the large progress that has been made in this field in the past few years. PMID:24763215

Micro-optomechanical trampoline resonators

NASA Astrophysics Data System (ADS)

Pepper, Brian; Kleckner, Dustin; Sonin, Petro; Jeffrey, Evan; Bouwmeester, Dirk

2011-03-01

Recently, micro-optomechanical devices have been proposed for implementation of experiments ranging from non-demolition measurements of phonon number to creation of macroscopic quantum superpositions. All have strenuous requirements on optical finesse, mechanical quality factor, and temperature. We present a set of devices composed of dielectric mirrors on Si 3 N4 trampoline resonators. We describe the fabrication process and present data on finesse and quality factor. The authors gratefully acknowledge support from NSF PHY-0804177 and Marie Curie EXT-CT-2006-042580.

A Preliminary Research on the Development of the Hard X-Ray Imaging Telescope

NASA Astrophysics Data System (ADS)

Zheng, C. X.; Cai, M. S.; Hu, Y. M.; Huang, Y. Y.; Gong, Y. Z.

2014-03-01

Since the 1860s, astronomers have explored a new field with the discovery of X-ray. Instead of the conventional imaging technique by using mirrors or lens, which can not work in the high-energy bands, direct imaging, coded aperture, and Fourier transform are used for the high-energy imaging. It can be implemented in various hardware configurations, among which the spatial modulation collimator are widely used. We adopt the grating collimator based on Fourier transform that is discussed in detail. This paper makes an investigation on the fabrication process of grating. The key components of the hard X-ray telescope based on the spatial modulation are developed, which contains 8 CsI-detector modules, 8-channel shaping amplifiers, and data acquisition system. The preliminary test results of readout electronics system are obtained.

Free-standing GaN grating couplers and rib waveguide for planar photonics at telecommunication wavelength

NASA Astrophysics Data System (ADS)

Liu, Qifa; Wang, Wei

2018-01-01

Gallium Nitride (GaN) free-standing planar photonic device at telecommunication wavelength based on GaN-on-silicon platform was presented. The free-standing structure was realized by particular double-side fabrication process, which combining GaN front patterning, Si substrate back releasing and GaN slab etching. The actual device parameters were identified via the physical characterizations employing scanning electron microscope (SEM), atomic force microscope (AFM) and reflectance spectra testing. High coupling efficiency and good light confinement properties of the gratings and rib waveguide at telecommunication wavelength range were verified by finite element method (FEM) simulation. This work illustrates the potential of new GaN photonic structure which will enable new functions for planar photonics in communication and sensing applications, and is favorable for the realization of integrated optical circuit.

Plasmonic Antenna Coupling for QWIPs

NASA Technical Reports Server (NTRS)

Hong, John

2007-01-01

In a proposed scheme for coupling light into a quantum-well infrared photodetector (QWIP), an antenna or an array of antennas made of a suitable metal would be fabricated on the face of what would otherwise be a standard QWIP. This or any such coupling scheme is required to effect polarization conversion: Light incident perpendicularly to the face is necessarily polarized in the plane of the face, whereas, as a matter of fundamental electrodynamics and related quantum selection rules, light must have a non-zero component of perpendicular polarization in order to be absorbed in the photodetection process. In a prior coupling scheme, gratings in the form of surface corrugations diffract normally gles, thereby imparting some perpendicular polarization. Unfortunately, the corrugation- fabrication process increases the overall nonuniformity of a large QWIP array. The proposed scheme is an alternative to the use of surface corrugations.

Theoretical and experimental investigation of 'grating' type photovoltaic cells

NASA Technical Reports Server (NTRS)

Loferski, J. J.; Crisman, E. E.; Armitage, W.; Chen, L. Y.

1974-01-01

The fabrication procedure and properties of 'grating' cells made by forming a fine grating pattern of aluminum alloyed into n-silicon wafers are described. The finest grating lines achieved in the cells described were 5 microns; the smallest spacing was about 15 microns. The best temperature for alloying was found to be about 600 C, a bit above the Si-Al eutectic temperature (576 C). The short-circuit current obtained from the best of these cells exposed to 100 mW/sq cm of (simulated air mass zero) illumination was at least equal to that obtained from conventional diffused cells, but their open-circuit voltage was lower. Their quantum yield was strongly blue-shifted; it was flat from 4000 to 8500 A.

Compact eccentric long period grating with improved sensitivity in low refractive index region.

PubMed

Shen, Fangcheng; Zhou, Kaiming; Gordon, Neil; Zhang, Lin; Shu, Xuewen

2017-07-10

We demonstrate a compact eccentric long period grating with enhanced sensitivity in low refractive index region. With a period designed at 15 µm for coupling light to high order cladding modes, the grating is more sensitive to surrounding refractive index in low refractive index region. The intrinsically low coupling coefficients for those high order cladding modes are significantly improved with the eccentric localized inscription induced by the femtosecond laser. The fabricated grating is compact with a length of 4.05 mm, and exhibits an average sensitivity of ~505 nm/RIU in low refractive index region (1.3328-1.3544). The proposed principle can also work in other refractive index region with a proper choice of the resonant cladding modes.

Subwavelength structured surfaces and their applications

NASA Technical Reports Server (NTRS)

Raguin, Daniel H.; Morris, G. Michael

1993-01-01

The term subwavelength structured (SWS) surface describes any surface that contains a subwavelength-period grating or gratings. The grating may be of any type provided the period is sufficiently fine so that, unlike conventional gratings, no diffraction orders propagate other than the zeroth orders. Because of the fine periods involved, the fabrication of such surfaces for applications in the visible and infrared portions of the spectral regime have only recently been considered. With refinements in holographic procedures and the push of the semiconductor industry for submicron lithography, production of SWS surfaces is becoming increasingly viable. The topics covered include the following: analytic approaches to analyze SWS surfaces, 1D periodic stratification and effective medium theory, design of waveplates using form birefringence, and 2D binary antireflection structured surfaces.

Fabrication of fiber Bragg gratings in embedded-core hollow optical fiber

NASA Astrophysics Data System (ADS)

Mao, Guopei; Sun, Bo; Yuan, Tingting; Zhong, Xing; Shi, Jinhui; Guan, Chunying; Yuan, Libo

2015-07-01

A novel Bragg fiber grating (FBG) in an embedded-core hollow optical fiber (ECHOF) has been proposed and experimentally demonstrated. The high-quality FBG fabricated with phase-mask technique by using 248 nm ultraviolet laser, has a resonant wavelength of ~943.1 nm and a dip of ~24.2 dB. Subsequently, the dependences of the resonant peak on the temperature and the axial strain were studied. Experimental results show that the temperature and axial stain sensitivity are 6.5 pm/°С and 1.1 pm/μɛ, respectively. In addition, a 0.03 nm shift of the transmission dip can be obtained when the polarization state changes from X polarization to Y polarization.

Infrared Wire-Grid Polarizer with Antireflection Structure by Imprinting on Both Sides

NASA Astrophysics Data System (ADS)

Yamada, Itsunari; Yamashita, Naoto; Tani, Kunihiko; Einishi, Toshihiko; Saito, Mitsunori; Fukumi, Kouhei; Nishii, Junji

2012-08-01

We fabricated infrared wire-grid polarizers with an antireflection (AR) grating structure by the simultaneous imprinting on both sides of a low-toxicity chalcogenide glass (Sb-Ge-Sn-S system). Silicon carbide and glassy carbon plates were used as molds for the direct glass imprinting. A wire-grid polarizer of 100-nm-thick was produced by depositing Al obliquely on the grating. Although the transmittance of the chalcogenide glass substrate was 62-66% in the 8.5-10.5 µm wavelength range, the transverse magnetic (TM) transmittance of the fabricated element became higher than 70% owing to the AR structure. The extinction ratio was larger than 20 dB at 11 µm wavelength.

Photonic bandpass filter characteristics of multimode SOI waveguides integrated with submicron gratings.

PubMed

Sah, Parimal; Das, Bijoy Krishna

2018-03-20

It has been shown that a fundamental mode adiabatically launched into a multimode SOI waveguide with submicron grating offers well-defined flat-top bandpass filter characteristics in transmission. The transmitted spectral bandwidth is controlled by adjusting both waveguide and grating design parameters. The bandwidth is further narrowed down by cascading two gratings with detuned parameters. A semi-analytical model is used to analyze the filter characteristics (1500  nm≤λ≤1650  nm) of the device operating in transverse-electric polarization. The proposed devices were fabricated with an optimized set of design parameters in a SOI substrate with a device layer thickness of 250 nm. The pass bandwidth of waveguide devices integrated with single-stage gratings are measured to be ∼24  nm, whereas the device with two cascaded gratings with slightly detuned periods (ΔΛ=2  nm) exhibits a pass bandwidth down to ∼10  nm.

Multi-channel polarized thermal emitter

DOEpatents

Lee, Jae-Hwang; Ho, Kai-Ming; Constant, Kristen P

2013-07-16

A multi-channel polarized thermal emitter (PTE) is presented. The multi-channel PTE can emit polarized thermal radiation without using a polarizer at normal emergence. The multi-channel PTE consists of two layers of metallic gratings on a monolithic and homogeneous metallic plate. It can be fabricated by a low-cost soft lithography technique called two-polymer microtransfer molding. The spectral positions of the mid-infrared (MIR) radiation peaks can be tuned by changing the periodicity of the gratings and the spectral separation between peaks are tuned by changing the mutual angle between the orientations of the two gratings.

Flattop wideband wavelength converters based on cascaded sum and difference-frequency generation using step-chirped gratings

NASA Astrophysics Data System (ADS)

Tehranchi, Amirhossein; Kashyap, Raman

2011-03-01

We investigate the role of step-chirped gratings (SCG) for flattening of conversion efficiency response and enhancing the pump bandwidth in cascaded sum and difference frequency generation (SFG + DFG) with a large pump wavelength difference. To obtain a flat response with maximum efficiency, using SCG instead of uniform grating with the same length, the appropriate critical period shifts are presented for the reasonable number of sections and chirp steps feasible for fabrication. Furthermore, it is shown that adding the section numbers for SCG structure increases the pump bandwidth.

Recording polarization gratings with a standing spiral wave

NASA Astrophysics Data System (ADS)

Vernon, Jonathan P.; Serak, Svetlana V.; Hakobyan, Rafik S.; Aleksanyan, Artur K.; Tondiglia, Vincent P.; White, Timothy J.; Bunning, Timothy J.; Tabiryan, Nelson V.

2013-11-01

A scalable and robust methodology for writing cycloidal modulation patterns of optical axis orientation in photosensitive surface alignment layers is demonstrated. Counterpropagating circularly polarized beams, generated by reflection of the input beam from a cholesteric liquid crystal, direct local surface orientation in a photosensitive surface. Purposely introducing a slight angle between the input beam and the photosensitive surface normal introduces a grating period/orientation that is readily controlled and templated. The resulting cycloidal diffractive waveplates offer utility in technologies requiring diffraction over a broad range of angles/wavelengths. This simple methodology of forming polarization gratings offers advantages over conventional fabrication techniques.

Distributed Sensing of Carbon-Epoxy Composites and Filament Wound Pressure Vessels Using Fiber-Bragg Gratings

NASA Technical Reports Server (NTRS)

Grant, J.; Kaul, R.; Taylor, S.; Myer, G.; Jackson, K.; Osei, A.; Sharma, A.

2003-01-01

Multiple Fiber Bragg-gratings are embedded in carbon-epoxy laminates as well as in composite wound pressure vessel. Structural properties of such composites are investigated. The measurements include stress-strain relation in laminates and Poisson's ratio in several specimens with varying orientation of the optical fiber Bragg-sensor with respect to the carbon fiber in an epoxy matrix. Additionally, fiber Bragg gratings are bonded on the surface of these laminates and cylinders fabricated out of carbon-epoxy composites and multiple points are monitored and compared for strain measurements at several locations.

High-temperature sustainability of strong fiber Bragg gratings written into Sb-Ge-codoped photosensitive fiber: decay mechanisms involved during annealing.

PubMed

Shen, Yonghang; He, Jinglei; Sun, Tong; Grattan, Kenneth T V

2004-03-15

An antimony--germanium- (Sb--Ge-) codoped fiber specially designed for the fabrication of fiber Bragg gratings (FBGs) with high temperature sustainability has been developed. The photosensitivity and the high-temperature sustainability of FBGs that have been written into this fiber were tested. The results obtained showed that the FBG written into this fiber has a very high temperature sustainability of 900 degrees C. A decay mechanism that involves cation hopping is presented to explain the observed high temperature sustainability of the grating written into this fiber.

Refraction effects in soft x-ray multilayer blazed gratings.

PubMed

Voronov, D L; Salmassi, F; Meyer-Ilse, J; Gullikson, E M; Warwick, T; Padmore, H A

2016-05-30

A 2500 lines/mm Multilayer Blazed Grating (MBG) optimized for the soft x-ray wavelength range was fabricated and tested. The grating coated with a W/B₄C multilayer demonstrated a record diffraction efficiency in the 2nd blazed diffraction order in the energy range from 500 to 1200 eV. Detailed investigation of the diffraction properties of the grating demonstrated that the diffraction efficiency of high groove density MBGs is not limited by the normal shadowing effects that limits grazing incidence x-ray grating performance. Refraction effects inherent in asymmetrical Bragg diffraction were experimentally confirmed for MBGs. The refraction affects the blazing properties of the MBGs and results in a shift of the resonance wavelength of the gratings and broadening or narrowing of the grating bandwidth depending on diffraction geometry. The true blaze angle of the MBGs is defined by both the real structure of the multilayer stack and by asymmetrical refraction effects. Refraction effects can be used as a powerful tool in providing highly efficient suppression of high order harmonics.

Recent and emerging applications of holographic photopolymers and nanocomposites

NASA Astrophysics Data System (ADS)

Naydenova, Izabela; Kotakonda, Pavani; Jallapuram, Raghavendra; Babeva, Tsvetanka; Mintova, S.; Bade, Denis; Martin, Suzanne; Toal, Vincent

2010-11-01

Sensing applications of holograms may be based on effects such as change in the spacing of the recorded fringes in a holographic diffraction grating in the presence of an analyte so that the direction of the diffracted laser light changes, or, in the case of a white light reflection grating, the wavelength of the diffracted light changes. An example is a reflection grating which swells in the presence of atmospheric moisture to indicate relative humidity by a change is the colour of the diffracted light. These devices make use of the photopolymer's ability to absorb moisture. In a more versatile approach one can add inorganic nanoparticles to the photopolymer composition. These nanoparticles have refractive indices that are different from that of the bulk photopolymer. During the holographic recording of diffraction gratings, the polymerisation and accompanying diffusion processes cause redistribution of the nanoparticles enhancing the holographic diffraction efficiency. Zeolite nanoparticles have the form of hollow cages enabling them to trap analyte molecules of appropriate sizes. The refractive index of the nanoparticle-analyte combination is normally different from that of the nanoparticles alone and this alters the refractive index modulation of the recorded grating, leading to a change in diffraction efficiency and hence of the strength of the diffracted light signal. Yet another approach makes use of a principle which we call dye deposition holography. The analyte is labelled using a dye which acts as a photosensitiser for the polymerisation process. When the analyte labeled is deposited on a layer containing the other photopolymer components photopolymerisation can take place. If the illumination is in the form of an interference pattern, a diffraction grating is formed, in the region where dye has been deposited. In this way the formation of a holographic diffraction grating itself becomes a sensing action with the potential for extremely high signal to noise ratio. The method also allows fabrication of photonic devices by direct writing, using photosensitising dye, of structures such as Fresnel zone plate lenses and waveguides onto the photopolymer layer followed by exposure to spatially uniform light. Our work on HDS is concerned with enhancing the diffraction efficiency of user selected very weak diffraction gratings by illumination with a single beam at the Bragg angle. Light in the illuminating beam is coupled into the diffracted beam and the two interfere to enhance the grating strength. In this way grating diffraction efficiency can be raised above a threshold so that a binary zero can be changed to binary one. A large number of identical weak holographic gratings may be multiplexed into the recording medium at the manufacturing stage, for user selection at the data recording stage. In this way consumer HDS systems could be made much more simply and cheaply than at present.

Suppressing Ghost Diffraction in E-Beam-Written Gratings

NASA Technical Reports Server (NTRS)

Wilson, Daniel; Backlund, Johan

2009-01-01

A modified scheme for electron-beam (E-beam) writing used in the fabrication of convex or concave diffraction gratings makes it possible to suppress the ghost diffraction heretofore exhibited by such gratings. Ghost diffraction is a spurious component of diffraction caused by a spurious component of grating periodicity as described below. The ghost diffraction orders appear between the main diffraction orders and are typically more intense than is the diffuse scattering from the grating. At such high intensity, ghost diffraction is the dominant source of degradation of grating performance. The pattern of a convex or concave grating is established by electron-beam writing in a resist material coating a substrate that has the desired convex or concave shape. Unfortunately, as a result of the characteristics of electrostatic deflectors used to control the electron beam, it is possible to expose only a small field - typically between 0.5 and 1.0 mm wide - at a given fixed position of the electron gun relative to the substrate. To make a grating larger than the field size, it is necessary to move the substrate to make it possible to write fields centered at different positions, so that the larger area is synthesized by "stitching" the exposed fields.

A novel 3D deformation measurement method under optical microscope for micro-scale bulge-test

NASA Astrophysics Data System (ADS)

Wu, Dan; Xie, Huimin

2017-11-01

A micro-scale 3D deformation measurement method combined with optical microscope is proposed in this paper. The method is based on gratings and phase shifting algorithm. By recording the grating images before and after deformation from two symmetrical angles and calculating the phases of the grating patterns, the 3D deformation field of the specimen can be extracted from the phases of the grating patterns. The proposed method was applied to the micro-scale bulge test. A micro-scale thermal/mechanical coupling bulge-test apparatus matched with the super-depth microscope was exploited. With the gratings fabricated onto the film, the deformed morphology of the bulged film was measured reliably. The experimental results show that the proposed method and the exploited bulge-test apparatus can be used to characterize the thermal/mechanical properties of the films at micro-scale successfully.

Hybrid grating reflectors: Origin of ultrabroad stopband

NASA Astrophysics Data System (ADS)

Park, Gyeong Cheol; Taghizadeh, Alireza; Chung, Il-Sug

2016-04-01

Hybrid grating (HG) reflectors with a high-refractive-index cap layer added onto a high contrast grating (HCG) provide a high reflectance close to 100% over a broader wavelength range than HCGs. The combination of a cap layer and a grating layer brings a strong Fabry-Perot (FP) resonance as well as a weak guided mode (GM) resonance. Most of the reflected power results from the FP resonance, while the GM resonance plays a key role in achieving a reflectance close to 100% as well as broadening the stopband. An HG sample with 7 InGaAlAs quantum wells included in the cap layer has been fabricated by directly wafer-bonding a III-V cap layer onto a Si grating layer. Its reflection property has been characterized. This heterogeneously integrated HG reflector may allow for a hybrid III-V on Si laser to be thermally efficient, which has promising prospects for silicon photonics light sources and high-speed operation.

A Wafer-Bonded, Floating Element Shear-Stress Sensor Using a Geometric Moire Optical Transduction Technique

NASA Technical Reports Server (NTRS)

Horowitz, Stephen; Chen, Tai-An; Chandrasekaran, Venkataraman; Tedjojuwono, Ken; Cattafesta, Louis; Nishida, Toshikazu; Sheplak, Mark

2004-01-01

This paper presents a geometric Moir optical-based floating-element shear stress sensor for wind tunnel turbulence measurements. The sensor was fabricated using an aligned wafer-bond/thin-back process producing optical gratings on the backside of a floating element and on the top surface of the support wafer. Measured results indicate a static sensitivity of 0.26 microns/Pa, a resonant frequency of 1.7 kHz, and a noise floor of 6.2 mPa/(square root)Hz.

Flexible organic light-emitting diodes with enhanced light out-coupling efficiency fabricated on a double-sided nanotextured substrate.

PubMed

Luo, Yu; Wang, Chunhui; Wang, Li; Ding, Yucheng; Li, Long; Wei, Bin; Zhang, Jianhua

2014-07-09

High-efficiency organic light-emitting diodes (OLEDs) have generated tremendous research interest. One of the exciting possibilities of OLEDs is the use of flexible plastic substrates, which unfortunately have a mismatching refractive index compared with the conventional ITO anode and the air. To unlock the light loss on flexible plastic, we report a high-efficiency flexible OLED directly fabricated on a double-sided nanotextured polycarbonate substrate by thermal nanoimprint lithography. The template for the nanoimprint process is a replicate from a silica arrayed with nanopillars and fabricated by ICP etching through a SiO2 colloidal spheres mask. It has been shown that with the internal quasi-periodical scattering gratings the efficiency enhancement can reach 50% for a green light OLED, and with an external antireflection structure, the normal transmittance is increased from 89% to 94% for paraboloid-like pillars. The OLED directly fabricated on the double-sided nanotextured polycarbonate substrate has reached an enhancing factor of ∼2.8 for the current efficiency.

Design and fabrication of an elliptical micro-lens array with grating for laser safety

NASA Astrophysics Data System (ADS)

Li, L. H.; Wu, B. Q.; Chan, C. Y.; Lee, W. B.; Dong, L. H.

2015-10-01

With the enormous expansion of laser usage in medicine, industry and research, all facilities must formulate and adhere to specific safety methods that appropriately address user protection. The protective ellipticalal microstructure with grating is a novel technology which can provide the principal means of ensuring against ocular injury, and must be worn at all times during laser operation. On the basis of Fresnel's law and the diffractive law, Solidworks and Lighttools software are applied to design the elliptical micro-lens array and correspondent grating. The height of the microstructure is 100um and its period is 3mm. The period of grating is 5um. It is shown that the amount of emergent light of a specific wavelength (1064nm) can reflect more than 40° from the incident light through simulation, while the incident light is perpendicular to the microstructure. The fabrication adopts the ultra-precision single point diamond method and injection molding method. However, it is found in the test that the surface roughness has a serious effect on the angle between the emergent and incident light. As a result, the element can reflect the vertical incidence beam into a tilted emergent beam with a certain angular degree , as well as protecting users from laser damage injures.

Design and optimization of a volume-phase holographic grating for simultaneous use with red, green, and blue light using unpolarized light.

PubMed

Mahamat, Adoum H; Narducci, Frank A; Schwiegerling, James

2016-03-01

Volume-phase holographic (VPH) gratings have been designed for use in many areas of science and technology, such as optical communication, optical imaging, and astronomy. In this paper, the design of a volume-phase holographic grating, simultaneously optimized to operate in the red, green, and blue wavelengths, is presented along with a study of its fabrication tolerances. The grating is optimized to produce 98% efficiency at λ=532  nm and at least 75% efficiency in the region between 400 and 700 nm, when the incident light is unpolarized. The optimization is done for recording in dichromated gelatin with a thickness of 12 μm, an average refractive index of 1.5, and a refractive index modulation of 0.022.

A fast response hydrogen sensor with Pd metallic grating onto a fiber's end-face

NASA Astrophysics Data System (ADS)

Yan, Haitao; Zhao, Xiaoyan; Zhang, Chao; Li, Qiu-Ze; Cao, Jingxiao; Han, Dao-Fu; Hao, Hui; Wang, Ming

2016-01-01

We demonstrated an integrated hydrogen sensor with Pd metallic grating fabricated on a fiber end-face. The grating consists of three thin metal layers in stacks, Au, WO3 and Pd. The WO3 is used as a waveguide layer between the Pd and Au layer. The Pd layer is etched by using a focused ion beam (FIB) method, forming a Pd metallic grating with period of 450 nm. The sensor is experimentally exposed to hydrogen gas environment. Changing the concentration from 0% to 4% which is the low explosive limit (LEL), the resonant wavelength measured from the reflection experienced 28.10 nm spectral changes in the visible range. The results demonstrated that the sensor is sensitive for hydrogen detection and it has fast response and low temperature effect.

Low energy X-ray grating interferometry at the Brazilian Synchrotron

NASA Astrophysics Data System (ADS)

Koch, F. J.; O'Dowd, F. P.; Cardoso, M. B.; Da Silva, R. R.; Cavicchioli, M.; Ribeiro, S. J. L.; Schröter, T. J.; Faisal, A.; Meyer, P.; Kunka, D.; Mohr, J.

2017-06-01

Grating based X-ray differential phase contrast imaging has found a large variety of applications in the last decade. Different types of samples call for different imaging energies, and efforts have been made to establish the technique all over the spectrum used for conventional X-ray imaging. Here we present a two-grating interferometer working at 8.3 keV, implemented at the bending magnet source of the IMX beamline of the Brazilian Synchrotron Light Laboratory. The low design energy is made possible by gratings fabricated on polymer substrates, and makes the interferometer mainly suited to the investigation of light and thin samples. We investigate polymer microspheres filled with Fe2O3 nanoparticles, and find that these particles give rise to a significant visibility reduction due to small angle scattering.

Bio-inspired Fabrication of Complex Hierarchical Structure in Silicon.

PubMed

Gao, Yang; Peng, Zhengchun; Shi, Tielin; Tan, Xianhua; Zhang, Deqin; Huang, Qiang; Zou, Chuanping; Liao, Guanglan

2015-08-01

In this paper, we developed a top-down method to fabricate complex three dimensional silicon structure, which was inspired by the hierarchical micro/nanostructure of the Morpho butterfly scales. The fabrication procedure includes photolithography, metal masking, and both dry and wet etching techniques. First, microscale photoresist grating pattern was formed on the silicon (111) wafer. Trenches with controllable rippled structures on the sidewalls were etched by inductively coupled plasma reactive ion etching Bosch process. Then, Cr film was angled deposited on the bottom of the ripples by electron beam evaporation, followed by anisotropic wet etching of the silicon. The simple fabrication method results in large scale hierarchical structure on a silicon wafer. The fabricated Si structure has multiple layers with uniform thickness of hundreds nanometers. We conducted both light reflection and heat transfer experiments on this structure. They exhibited excellent antireflection performance for polarized ultraviolet, visible and near infrared wavelengths. And the heat flux of the structure was significantly enhanced. As such, we believe that these bio-inspired hierarchical silicon structure will have promising applications in photovoltaics, sensor technology and photonic crystal devices.

Fabrication of micro-optical components using femtosecond oscillator pulses

NASA Astrophysics Data System (ADS)

Rodrigues, Vanessa R. M.; Ramachandran, Hema; Chidangil, Santhosh; Mathur, Deepak

2017-06-01

With a penchant for integrated photonics and miniaturization, the fabrication of micron sized optical elements using precision laser pulse management is drawing attention due to the possibility of minimizing tolerances for collateral material damage. The work presented here deals with the design, fabrication and characterization of a range of diffractive optics - gratings, grids and Fresnel zone plates - on transparent and metallic samples. Their low volume, light weight, transmission bandwidth, high damage threshold and flexible design make them suited for replacing conventional refractive optical elements. Our one-step, mask-less, 3-D laser direct writing process is a green fabrication technique which is in stark contrast to currently popular Photo-lithography based micro-structuring. Our method provides scope for modifications on the surface as well as within the bulk of the material. The mechanism involved in the fabrication of these optics on transparent and thin metallic substrates differ from each other. Our studies show that both amplitude and phase versions of micro-structures were achieved successfully with performances bearing 98% accuracy vis-a-vis theoretical expectations.

Cross-fiber Bragg grating transducer

NASA Technical Reports Server (NTRS)

Albin, Sacharia (Inventor); Zheng, Jianli (Inventor); Lavarias, Arnel (Inventor)

2000-01-01

A transducer has been invented that uses specially-oriented gratings in waveguide a manner that allows the simultaneous measurement of physical phenomena (such as shear force, strain and temperature) in a single sensing element. The invention has a highly sensitive, linear response and also has directional sensitivity with regard to strain. The transducer has a waveguide with a longitudinal axis as well as two Bragg gratings. The transducer has a first Bragg grating associated with the waveguide that has an angular orientation .theta..sub.a relative to a perpendicular to the longitudinal axis such that 0.degree.<.theta..sub.a <.theta..sub.max. The second Bragg grating is associated with the waveguide in such a way that the angular orientation .theta..sub.b of the grating relative to a perpendicular to the longitudinal axis is (360.degree.-.theta..sub.max)<.theta..sub.b <360.degree.. The first Bragg grating can have a periodicity .LAMBDA..sub.a and the second Bragg grating can have a periodicity .LAMBDA..sub.b such that the periodicity .LAMBDA..sub.a of the first Bragg grating does not equal the periodicity .LAMBDA..sub.b of the second Bragg grating. The angle of the gratings can be such that .theta..sub.a =360.degree.-.theta..sub.b. The waveguide can assume a variety of configurations, including an optical fiber, a rectangular waveguide and a planar waveguide. The waveguide can be fabricated of a variety of materials, including silica and polymer material.

Optical spatial differentiator based on subwavelength high-contrast gratings

NASA Astrophysics Data System (ADS)

Dong, Zhewei; Si, Jiangnan; Yu, Xuanyi; Deng, Xiaoxu

2018-04-01

An optical spatial differentiator based on subwavelength high-contrast gratings (HCGs) is proposed experimentally. The spatial differentiation property of the subwavelength HCG is analyzed by calculating its spatial spectral transfer function based on the periodic waveguide theory. By employing the FDTD solutions, the performance of the subwavelength HCG spatial differentiator was investigated numerically. The subwavelength HCG differentiator with the thickness at the nanoscale was fabricated on the quartz substrate by electron beam lithography and Bosch deep silicon etching. Observed under an optical microscope with a CCD camera, the spatial differentiation of the incident field profile was obtained by the subwavelength HCG differentiator in transmission without Fourier lens. By projecting the images of slits, letter "X," and a cross on the subwavelength HCG differentiator, edge detections of images were obtained in transmission. With the nanoscale HCG structure and simple optical implementation, the proposed optical spatial differentiator provides the prospects for applications in optical computing systems and parallel data processing.

Designing Plasmonic Materials and Optical Metasurfaces for Light Manipulation and Optical Sensing

NASA Astrophysics Data System (ADS)

Chen, Wenxiang

Metamaterials are artificial materials designed to create optical properties that do not exist in nature. They are assemblies of subwavelength structures that are tailored in size, shape, composition, and orientation to realize the desired property. Metamaterials are promising for applications in diverse areas: optical filters, lenses, holography, sensors, photodetectors, photovoltaics, photocatalysts, medical devices, and many more, because of their excellent abilities in bending, absorbing, enhancing and blocking light. However, the practical use of metamaterials is challenged by the lack of plasmonic materials with proper permittivity for different applications and the slow and expensive fabrication methods available to pattern sub-wavelength structures. We have also only touched the surface in exploring the innovative uses of metamaterials to solve world problems. In this thesis, we study the fundamental optical properties of metamaterial building blocks by designing material permittivity. We continuously tune the interparticle distance in colloidal Au nanocrystal (NC) solids via the partial ligand exchange process. Then we combine top-down nanoimprint lithography with bottom-up assembly of colloidal NCs to develop a large-area, low-cost fabrication method for subwavelength nanostructures. Via this method, we fabricate and characterize nano-antenna arrays of different sizes and demonstrate metasurface quarter wave-plates of different bandwidth, and compare their performances with simulation results. We also integrate the metasurfaces with chemically- and mechanically-responsive polymers for strong-signal sensing. In the first design, we combine ultrathin plasmonic nanorods with hydrogel to fabricate optical moisture sensors for agricultural use. In the second application, we design mechanically tunable Au grating resonances on a polydimethylsiloxane (PDMS) substrate. The dimensions of Au grating are carefully engineered to achieve a hybridized, ultrasharp, and ultrasensitive resonance peak.

Large area nano-patterning /writing on gold substrate using dip - pen nanolithography (DPN)

NASA Astrophysics Data System (ADS)

Saini, Sudhir Kumar; Vishwakarma, Amit; Agarwal, Pankaj B.; Pesala, Bala; Agarwal, Ajay

2014-10-01

Dip Pen Nanolithography (DPN) is utilized to pattern large area (50μmX50μm) gold substrate for application in fabricating Nano-gratings. For Nano-writing 16-MHA ink coated AFM tip was prepared using double dipping procedure. Gold substrate is fabricated on thermally grown SiO2 substrate by depositing ˜5 nm titanium layer followed by ˜30nm gold using DC pulse sputtering. The gratings were designed using period of 800nm and 25% duty cycle. Acquired AFM images indicate that as the AFM tip proceeds for nano-writing, line width decreases from 190nm to 100nm. This occurs probably due to depreciation of 16-MHA molecules in AFM tip as writing proceeds.

E-beam generated holographic masks for optical vector-matrix multiplication

NASA Technical Reports Server (NTRS)

Arnold, S. M.; Case, S. K.

1981-01-01

An optical vector matrix multiplication scheme that encodes the matrix elements as a holographic mask consisting of linear diffraction gratings is proposed. The binary, chrome on glass masks are fabricated by e-beam lithography. This approach results in a fairly simple optical system that promises both large numerical range and high accuracy. A partitioned computer generated hologram mask was fabricated and tested. This hologram was diagonally separated outputs, compact facets and symmetry about the axis. The resultant diffraction pattern at the output plane is shown. Since the grating fringes are written at 45 deg relative to the facet boundaries, the many on-axis sidelobes from each output are seen to be diagonally separated from the adjacent output signals.

Replication of Holograms with Corn Syrup by Rubbing

PubMed Central

Mejias-Brizuela, Nildia Y.; Olivares-Pérez, Arturo; Ortiz-Gutiérrez, Mauricio

2012-01-01

Corn syrup films are used to replicate holograms in order to fabricate micro-structural patterns without the toxins commonly found in photosensitive salts and dyes. We use amplitude and relief masks with lithographic techniques and rubbing techniques in order to transfer holographic information to corn syrup material. Holographic diffraction patterns from holographic gratings and computer Fourier holograms fabricated with corn syrup are shown. We measured the diffraction efficiency parameter in order to characterize the film. The versatility of this material for storage information is promising. Holographic gratings achieved a diffraction efficiency of around 8.4% with an amplitude mask and 36% for a relief mask technique. Preliminary results using corn syrup as an emulsion for replicating holograms are also shown in this work.

Dynamic evolution of the spectrum of long-period fiber Bragg gratings fabricated from hydrogen-loaded optical fiber by ultraviolet laser irradiation.

PubMed

Fujita, Keio; Masuda, Yuji; Nakayama, Keisuke; Ando, Maki; Sakamoto, Kenji; Mohri, Jun-pei; Yamauchi, Makoto; Kimura, Masanori; Mizutani, Yasuo; Kimura, Susumu; Yokouchi, Takashi; Suzaki, Yoshifumi; Ejima, Seiki

2005-11-20

Long-period fiber Bragg gratings fabricated by exposure of hydrogen-loaded fiber to UV laser light exhibit large-scale dynamic evolution for approximately two weeks at room temperature. During this time two distinct features show up in their spectrum: a large upswing in wavelength and a substantial deepening of the transmission minimum. The dynamic evolution of the transmission spectrum is explained quantitatively by use of Malo's theory of UV-induced quenching [Electron. Lett. 30, 442 (1994)] followed by refilling of hydrogen in the fiber core and the theory of hydrogen diffusion in the fiber material. The amount of hydrogen quenched by the UV irradiation is 6% of the loaded hydrogen.

Selective Photophysical Modification on Light-Emitting Polymer Films for Micro- and Nano-Patterning

PubMed Central

Zhang, Xinping; Liu, Feifei; Li, Hongwei

2016-01-01

Laser-induced cross-linking in polymeric semiconductors was utilized to achieve micro- and nano-structuring in thin films. Single- and two-photon cross-linking processes led to the reduction in both the refractive index and thickness of the polymer films. The resultant photonic structures combine the features of both relief- and phase-gratings. Selective cross-linking in polymer blend films based on different optical response of different molecular phases enabled “solidification” of the phase-separation scheme, providing a stable template for further photonic structuring. Dielectric and metallic structures are demonstrated for the fabrication methods using cross-linking in polymer films. Selective cross-linking enables direct patterning into polymer films without introducing additional fabrication procedures or additional materials. The diffraction processes of the emission of the patterned polymeric semiconductors may provide enhanced output coupling for light-emitting diodes or distributed feedback for lasers. PMID:28773248

Modeling and Observations of Phase-Mask Trapezoidal Profiles with Grating-Fiber Image Reproduction

NASA Technical Reports Server (NTRS)

Lyons, Donald R.; Lindesay, James V.; Lee, Hyung R.; Ndlela, Zolili U.; Thompso, Erica J.

2000-01-01

We report on an investigation of the trapezoidal design and fabrication defects in phase masks used to produce Bragg reflection gratings in optical fibers. We used a direct visualization technique to examine the nonuniformity of the interference patterns generated by several phase masks. Fringe patterns from the phase masks are compared with the analogous patterns resulting from two-beam interference. Atomic force microscope imaging of the actual phase gratings that give rise to anomalous fringe patterns is used to determine input parameters for a general theoretical model. Phase masks with pitches of 0.566 and 1.059 microns are modeled and investigated.

Holographic assembly of semiconductor CdSe quantum dots in polymer for volume Bragg grating structures with diffraction efficiency near 100%

NASA Astrophysics Data System (ADS)

Liu, Xiangming; Tomita, Yasuo; Oshima, Juro; Chikama, Katsumi; Matsubara, Koutatsu; Nakashima, Takuya; Kawai, Tsuyoshi

2009-12-01

We report on the fabrication of centimeter-size transmission Bragg gratings in semiconductor CdSe quantum dots dispersed 50 μm thick photopolymer films. This was done by holographic assembly of CdSe quantum dots in a photopolymerizable monomer blend. Periodic patterning of CdSe quantum dots in polymer was confirmed by a fluorescence microscope and confocal Raman imaging. The diffraction efficiency from the grating of 1 μm spacing was near 100% in the green with 0.34 vol % CdSe quantum dots, giving the refractive index modulation as large as 5.1×10-3.

Shift-bonded resonance-domain diffraction gratings.

PubMed

Axelrod, Ramon; Shacham-Diamand, Yosi; Golub, Michael

2016-10-20

Resonance-domain-transmission diffractive optics with grating periods comparable to those of the illumination wavelength offers large angles of light deflection and nearly 100% Bragg diffraction efficiency. Optical design preferences for nearly normal incidence can be met by proper choice for the slant of the diffraction grooves relative to the substrate. However, straightforward fabrication of the slanted submicron high-aspect-ratio grooves is challenging. In this paper, optical performance comparable to that of the slanted grooves was achieved by an alternative solution of bonding two half-height symmetrical gratings with a lateral shift and an optional small longitudinal spacing. Results of design, nanofabrication, and optical testing are presented.

All-fiber mode converter based on superimposed long period fiber gratings

NASA Astrophysics Data System (ADS)

Xue, Yan-ru; Bi, Wei-hong; Jin, Wa; Tian, Peng-fei; Jiang, Peng; Liu, Qiang; Jin, Yun

2018-03-01

In this paper, a novel broadband all-fiber mode converter is proposed and experimentally demonstrated. Through writing a pair of superimposed long period fiber gratings (SLPFGs) in tow-mode fiber (TMF) with a CO2 laser, the mode converter can realize the conversion from LP01 to LP11 owing to the phase matching condition. Numerical and experimental results show that the bandwidth of this mode converter is 3 times broader than that of a single grating converter. The converter has low loss, high coupling efficiency, small size and is easy to fabricate, so it can be widely used in mode-division multiplexing.

Single-order, subwavelength resonant nanograting as a uniformly hot substrate for surface-enhanced Raman spectroscopy.

PubMed

Deng, Xuegong; Braun, Gary B; Liu, Sheng; Sciortino, Paul F; Koefer, Bob; Tombler, Thomas; Moskovits, Martin

2010-05-12

The surface-enhanced Raman spectroscopy (SERS) activity and the optical reflectance of a subwavelength gold nanograting fabricated entirely using top down technologies on silicon wafers are presented. The grating consists of 120 nm gold cladding on top of parallel silica nanowires constituting the grating's lines, with gaps between nanowires <10 nm wide at their narrowest point. The grating produces inordinately intense SERS and shows very strong polarization dependence. Reflectance measurements for the optimized grating indicate that (when p-polarization is used and at least one of the incident electric field components lies across the grating lines) the reflectance drops to <1% at resonance, indicating that essentially all of the radiant energy falling on the surface is coupled into the grating. The SERS intensity and the reflectance at resonance anticorrelate predicatively, suggesting that reflectance measurements can provide a nondestructive, wafer-level test of SERS efficacy. The SERS performance of the gratings is very uniform and reproducible. Extensive measurements on samples cut from both the same wafer and from different wafers, produce a SERS intensity distribution function that is similar to that obtained for ordinary Raman measurements carried out at multiple locations on a polished (100) silicon wafer.

Instrument and method for focusing X-rays, gamma rays and neutrons

DOEpatents

Smither, Robert K.

1984-01-01

A crystal diffraction instrument or diffraction grating instrument with an improved crystalline structure or grating spacing structure having a face for receiving a beam of photons or neutrons and diffraction planar spacing or grating spacing along that face with the spacing increasing progressively along the face to provide a decreasing Bragg diffraction angle for a monochromatic radiation and thereby increasing the usable area and acceptance angle. The increased planar spacing for the diffraction crystal is provided by the use of a temperature differential across the crystalline structure, by assembling a plurality of crystalline structures with different compositions, by an individual crystalline structure with a varying composition and thereby a changing planar spacing along its face, and by combinations of these techniques. The increased diffraction grating element spacing is generated during the fabrication of the diffraction grating by controlling the cutting tool that is cutting the grooves or controlling the laser beam, electron beam or ion beam that is exposing the resist layer, etc. It is also possible to vary this variation in grating spacing by applying a thermal gradient to the diffraction grating in much the same manner as is done in the crystal diffraction case.

Instrument and method for focusing x rays, gamma rays, and neutrons

DOEpatents

Smither, R.K.

1982-03-25

A crystal-diffraction instrument or diffraction-grating instrument is described with an improved crystalline structure or grating spacing structure having a face for receiving a beam of photons or neutrons and diffraction planar spacing or grating spacing along that face with the spacing increasing progressively along the face to provide a decreasing Bragg diffraction angle for a monochromatic radiation and thereby increasing the usable area and acceptance angle. The increased planar spacing for the diffraction crystal is provided by the use of a temperature differential across the line structures with different compositions, by an individual crystalline structure with a varying composition and thereby a changing planar spacing along its face, and by combinations of these techniques. The increased diffraction grating element spacing is generated during the fabrication of the diffraction grating by controlling the cutting tool that is cutting the grooves or controlling the laser beam, electron beam, or ion beam that is exposing the resist layer, etc. It is also possible to vary this variation in grating spacing by applying a thermal gradient to the diffraction grating in much the same manner as is done in the crystal-diffraction case.

Enhanced Photocurrent Generation from Bacteriorhodopsin Photocells Using Grating-Structured Transparent Conductive Oxide Electrodes.

PubMed

Kaji, Takahiro; Kasai, Katsuyuki; Haruyama, Yoshihiro; Yamada, Toshiki; Inoue, Shin-Ichiro; Tominari, Yukihiro; Ueda, Rieko; Terui, Toshifumi; Tanaka, Shukichi; Otomo, Akira

2016-04-01

We fabricated a grating-structured electrode made of indium-doped zinc oxide (IZO) with a high refractive index (approximately 2) for a bacteriorhodopsin (bR) photocell. We investigated the photocurrent characteristics of the bR photocell and demonstrated that the photocurrent values from the bR/IZO electrode with the grating structure with a grating period of 340 nm were more than 3.5-4 times larger than those without the grating structure. The photocurrent enhancement was attributed to the resonance effect due to light coupling to the grating structure as well as the scattering effect based on the experimental results and analysis using the photonic band structure determined using finite-difference time-domain (FDTD) simulations. The refractive index of the bR film in electrolyte solution (1.40) used in the FDTD simulations was estimated by analyzing the extinction peak wavelength of 20-nm gold colloids in the bR film. Our results indicate that the grating- or photonic-crystal-structured transparent conductive oxide (TCO) electrodes can increase the light use efficiency of various bR devices such as artificial photosynthetic devices, solar cells, and light-sensing devices.

Flexible fabrication of multi-scale integrated 3D periodic nanostructures with phase mask

NASA Astrophysics Data System (ADS)

Yuan, Liang Leon

Top-down fabrication of artificial nanostructures, especially three-dimensional (3D) periodic nanostructures, that forms uniform and defect-free structures over large area with the advantages of high throughput and rapid processing and in a manner that can further monolithically integrate into multi-scale and multi-functional devices is long-desired but remains a considerable challenge. This thesis study advances diffractive optical element (DOE) based 3D laser holographic nanofabrication of 3D periodic nanostructures and develops new kinds of DOEs for advanced diffracted-beam control during the fabrication. Phase masks, as one particular kind of DOE, are a promising direction for simple and rapid fabrication of 3D periodic nanostructures by means of Fresnel diffraction interference lithography. When incident with a coherent beam of light, a suitable phase mask (e.g. with 2D nano-grating) can create multiple diffraction orders that are inherently phase-locked and overlap to form a 3D light interference pattern in the proximity of the DOE. This light pattern is typically recorded in photosensitive materials including photoresist to develop into 3D photonic crystal nanostructure templates. Two kinds of advanced phase masks were developed that enable delicate phase control of multiple diffraction beams. The first exploits femtosecond laser direct writing inside fused silica to assemble multiple (up to nine) orthogonally crossed (2D) grating layers, spaced on Talbot planes to overcome the inherent weak diffraction efficiency otherwise found in low-contrast volume gratings. A systematic offsetting of orthogonal grating layers to establish phase offsets over 0 to pi/2 range provided precise means for controlling the 3D photonic crystal structure symmetry between body centered tetragonal (BCT) and woodpile-like tetragonal (wTTR). The second phase mask consisted of two-layered nanogratings with small sub-wavelength grating periods and phase offset control. That was designed with isotropic properties attractive for generating a complete photonic band gap (PBG). An isolation layer was used between adjacent polymer layers to offer a reversal coating for sample preparation of scanning electron microscopy (SEM) imaging and top surface planarization. Electron beam lithography has been employed to fabricate a multi-level nano-grating phase mask that produces a diamond-like 3D nanostructure via phase mask lithography, promising for creating photonic crystal (PC) templates that can be inverted with high-index materials and form a complete PBG at telecommunication wavelengths. A laser scanning holographic method for 3D exposure in thick photoresist is introduced that combines the unique advantages of large area 3D holographic interference lithography (HIL) with the flexible patterning of laser direct writing to form both micro- and nano-structures in a single exposure step. Phase mask interference patterns accumulated over multiple overlapping scans are shown to stitch seamlessly and form highly uniform 3D nanostructure with beam size scaled to small 200 microm diameter. Further direct-write holography demonstrates monolithical writing of multi-scale lab-on-a-chip with multiple functionalities including on-chip integrated fluorescence. Various 3D periodic nanostructures are demonstrated over a 15 mmx15 mm area, through full 40 microm photoresist thickness and with uniform structural and optical properties revealed by focused ion beam (FIB) milling, SEM imaging and stopband measures. The lateral and axial periods scale from respective 1500 nm to 570 nm and 9.2 microm to 1.2 microm to offer a Gamma-Z stopband at 1.5 microm. Overall, laser scanning is presented as a facile means to embed 3D PC nanostructure within microfluidic channels for integration into an optofluidic lab-on-chip, demonstrating a new laser HIL writing approach for creating multi-scale integrated microsystems.

(HEL MRI) 3D Meta Optics for High Energy Lasers

DTIC Science & Technology

2016-09-13

based metal-oxide nano- hair structures for optical vortex generation," Opt. Express 23, 19056-19065 (2015) 15. Li, Yuan, Zeyu Zhang, Wenzhe Li, Jerome...Indumathi Raghu Srimathi, Aaron J. Pung, Yuan Li, Raymond C. Rumpf, and Eric G. Johnson, "Fabrication of metal-oxide nano- hairs for effective index...Grating Based Optical Nano- Hairs Using ALD Nano- Patterning Subwavelength gratings (SWGs) based artificial dielectric elements are used to obtain the

High-efficiency fiber-to-chip grating couplers realized using an advanced CMOS-compatible silicon-on-insulator platform.

PubMed

Vermeulen, D; Selvaraja, S; Verheyen, P; Lepage, G; Bogaerts, W; Absil, P; Van Thourhout, D; Roelkens, G

2010-08-16

A new generation of Silicon-on-Insulator fiber-to-chip grating couplers which use a silicon overlay to enhance the directionality and thereby the coupling efficiency is presented. Devices are realized on a 200 mm wafer in a CMOS pilot line. The fabricated fiber couplers show a coupling efficiency of -1.6 dB and a 3 dB bandwidth of 80 nm.

The evaluation of a deformable diffraction grating for a stigmatic EUV spectroheliometer

NASA Technical Reports Server (NTRS)

Timothy, J. G.

1987-01-01

A high-efficiency, extreme ultraviolet (EUV) imaging spectrometer is constructed and tested. The spectrometer employs a concave toroidal grating illuminated at normal incidence in a Rowland circle mounting and has only one reflecting surface. The toroidal grating has been fabricated by a new technique employing an elastically-deformable sub-master grating replicated in a spherical form and then mechanically distorted to produce the desired aspect ratio of the toroidal surface for stigmatic imaging over the selected wavelength range. The fixed toroidal grating used in the spectrometer is then replicated from this surface. Photographic tests and initial photoelectric tests with a two-dimensional, pulse-counting detector system verify the image quality of the toroidal grating at wavelengths near 600 A. The results of these tests and the basic designs of two instruments which could employ the imaging spectrometer for astrophysical investigations in space are described; i.e., a high-resolution EUV spectroheliometer for studies of the solar chromosphere, transition region, and corona; and an EUV spectroscopic telescope for studies of non-solar objects.

Large-area full field x-ray differential phase-contrast imaging using 2D tiled gratings

NASA Astrophysics Data System (ADS)

Schröter, Tobias J.; Koch, Frieder J.; Kunka, Danays; Meyer, Pascal; Tietze, Sabrina; Engelhardt, Sabine; Zuber, Marcus; Baumbach, Tilo; Willer, Konstantin; Birnbacher, Lorenz; Prade, Friedrich; Pfeiffer, Franz; Reichert, Klaus-Martin; Hofmann, Andreas; Mohr, Jürgen

2017-06-01

Grating-based x-ray differential phase-contrast imaging (DPCI) is capable of acquiring information based on phase-shift and dark-field signal, in addition to conventional x-ray absorption-contrast. Thus DPCI gives an advantage to investigate composite materials with component wise similar absorption properties like soft tissues. Due to technological challenges in fabricating high quality gratings over a large extent, the field of view (FoV) of the imaging systems is limited to a grating area of a couple of square centimeters. For many imaging applications (e.g. in medicine), however, a FoV that ranges over several ten centimeters is needed. In this manuscript we propose to create large area gratings of theoretically any extent by assembling a number of individual grating tiles. We discuss the precision needed for alignment of each microstructure tile in order to reduce image artifacts and to preserve minimum 90% of the sensitivity obtainable with a monolithic grating. To achieve a reliable high precision alignment a semiautomatic assembly system consisting of a laser autocollimator, a digital microscope and a force sensor together with positioning devices was built. The setup was used to tile a first four times four analyzer grating with a size of 200 mm  ×  200 mm together with a two times two phase grating. First imaging results prove the applicability and quality of the tiling concept.

Stratified Volume Diffractive Optical Elements as Low-Mass Coherent Lidar Scanners

NASA Technical Reports Server (NTRS)

Chambers, Diana M.; Nordin, Gregory P.; Kavaya, Michael J.

1999-01-01

Transmissive scanning elements for coherent laser radar systems are typically optical wedges, or prisms, which deflect the lidar beam at a specified angle and are then rotated about the instrument optical axis to produce a scan pattern. The wedge is placed in the lidar optical system subsequent to a beam-expanding telescope, implying that it has the largest diameter of any element in the system. The combination of the wedge diameter and asymmetric profile result in the element having very large mass and, consequently, relatively large power consumption required for scanning. These two parameters, mass and power consumption, are among the instrument requirements which need to be minimized when designing a lidar for a space-borne platform. Reducing the scanner contributions in these areas will have a significant effect on the overall instrument specifications, Replacing the optical wedge with a diffraction grating on the surface of a thin substrate is a straight forward approach with potential to reduce the mass of the scanning element significantly. For example, the optical wedge that will be used for the SPAce Readiness Coherent Lidar Experiment (SPARCLE) is approximately 25 cm in diameter and is made from silicon with a wedge angle designed for 30 degree deflection of a beam operating at approx. 2 micrometer wavelength. The mass of this element could be reduced by a factor of four by instead using a fused silica substrate, 1 cm thick, with a grating fabricated on one of the surfaces. For a grating to deflect a beam with a 2 micrometer wavelength by 30 degrees, a period of approximately 4 micrometers is required. This is small enough that fabrication of appropriate high efficiency blazed or multi-phase level diffractive optical gratings is prohibitively difficult. Moreover, bulk or stratified volume holographic approaches appear impractical due to materials limitations at 2 micrometers and the need to maintain adequate wavefront quality. In order to avoid the difficulties encountered in these approaches, we have developed a new type of high-efficiency grating which we call a Stratified Volume Diffractive Optical Element (SVDOE). The features of the gratings in this approach can be easily fabricated using standard photolithography and etching techniques and the materials used in the grating can be chosen specifically for a given application, In this paper we will briefly discuss the SVDOE technique and will present an example design of a lidar scanner using this approach. We will also discuss performance predictions for the example design.

Holographic patterning of organic-inorganic photopolymerizable nanocomposites

NASA Astrophysics Data System (ADS)

Sakhno, Oksana V.; Goldenberg, Leonid M.; Smirnova, Tatiana N.; Stumpe, J.

2009-09-01

We present here novel easily processible organic-inorganic nanocomposites suitable for holographic fabrication of diffraction optical elements (DOE). The nanocomposites are based on photocurable acrylate monomers and inorganic nanoparticles (NP). The compatibility of inorganic NP with monomers was achieved by capping the NP surface with proper organic shells. Surface modification allows to introduce up to 50wt.% of inorganic NP in organic media. Depending on the NP nature (metal oxides, phosphates, semiconductors, noble metals) and their properties, the materials for both efficient DOE and multifunctional elements can be designed. Organic-inorganic composites prepared have been successfully used for the effective inscription of periodic volume refractive index structures using the holographic photopolymerization method. The nanocomposite preparation procedure, their properties and optical performance of holographic gratings are reported. The use of functional NP makes it possible to obtain effective holographic gratings having additional physical properties such as light-emission or NLO. Some examples of such functional polymer-NP structures and their possible application fields are presented. The combination of easy photo-patterning of soft organic compounds with physical properties of inorganic materials in new nanocomposites and the flexibility of the holographic patterning method allow the fabrication of mono- and multifunctional one- and multi-dimensional passive or active optical and photonic elements.

Study on fabrication technology of silicon-based silica array waveguide grating

NASA Astrophysics Data System (ADS)

Sun, Yanjun; Dong, Lianhe; Leng, Yanbing

2009-05-01

Array waveguide grating (AWG) is an important plane optical element in dense wavelength division multiplex/demultiplex system. There are many virtue, channel quantity larger,lower loss, lower crosstalk, size smaller and high reliability etc. This article describs AWG fabrication technics utilizing IC(Integrated Circles) techniques, based on sixteen channel Silicon-Based Silica Array Waveguide Grating, put emphasis on discussing doping and deposition of waveguide core film,technics theory and interrelated parameter condition of photoetch and ion etching. Experiment result indicates that it depens on electrode structure, energy of radio-frequency electrode gas component, pressure ,flowing speed and substrate temperature by CVD depositing film .During depositing waveguide film by PE-CVD, the silicon is not reacted, When temperature becomes lower,it is reacted and it is easy to realize the control of film thickness and time with a result of film thickness uniformity reaching about 4% after optimizing deposition parameter and condition. We get the result of high etching speed rate, outline zoom, and side frame smooth by photoresist/Cr multiple mask and optimizing etching technics.

X-ray/EUV optics for astronomy, microscopy, polarimetry, and projection lithography; Proceedings of the Meeting, San Diego, CA, July 9-13, 1990

NASA Technical Reports Server (NTRS)

Hoover, Richard B. (Editor); Walker, Arthur B. C., Jr. (Editor)

1991-01-01

Topics discussed in this issue include the fabrication of multilayer X-ray/EUV coatings; the design, characterization, and test of multilayer X-ray/EUV coatings; multilayer X-ray/EUV monochromators and imaging microscopes; X-ray/EUV telescopes; the test and calibration performance of X-ray/EUV instruments; XUV/soft X-ray projection lithography; X-ray/EUV space observatories and missions; X-ray/EUV telescopes for solar research; X-ray/EUV polarimetry; X-ray/EUV spectrographs; and X-ray/EUV filters and gratings. Papers are presented on the deposition-controlled uniformity of multilayer mirrors, interfaces in Mo/Si multilayers, the design and analysis of an aspherical multilayer imaging X-ray microscope, recent developments in the production of thin X-ray reflecting foils, and the ultraprecise scanning technology. Consideration is also given to an active sun telescope array, the fabrication and performance at 1.33 nm of a 0.24-micron-period multilayer grating, a cylindrical proportional counter for X-ray polarimetry, and the design and analysis of the reflection grating arrays for the X-Ray Multi-Mirror Mission.

High-resolution compact spectrometer based on a custom-printed varied-line-spacing concave blazed grating.

PubMed

Chen, Jianwei; Chen, Wang; Zhang, Guodong; Lin, Hui; Chen, Shih-Chi

2017-05-29

We present the modeling, design and characterization of a compact spectrometer, achieving a resolution better than 1.5 nm throughout the visible spectrum (360-825 nm). The key component in the spectrometer is a custom-printed varied-line-space (VLS) concave blazed grating, where the groove density linearly decreases from the center of the grating (530 g/mm) at a rate of 0.58 nm/mm to the edge (528 g/mm). Parametric models have been established to deterministically link the system performance with the VLS grating design parameters, e.g., groove density, line-space varying rate, and to minimize the system footprint. Simulations have been performed in ZEMAX to confirm the results, indicating a 15% enhancement in system resolution versus common constant line-space (CLS) gratings. Next, the VLS concave blazed grating is fabricated via our vacuum nanoimprinting system, where a polydimethylsiloxane (PDMS) stamp is non-uniformly expanded to form the varied-line-spacing pattern from a planar commercial grating master (600 g/mm) for precision imprinting. The concave blazed grating is measured to have an absolute diffraction efficiency of 43%, higher than typical holographic gratings (~30%) used in the commercial compact spectrometers. The completed compact spectrometer contains only one optical component, i.e., the VLS concave grating, as well as an entrance slit and linear photodetector array, achieving a footprint of 11 × 11 × 3 cm 3 , which makes it the most compact and resolving (1.46 nm) spectrometer of its kind.

Diffraction study of duty-cycle error in ferroelectric quasi-phase-matching gratings with Gaussian beam illumination

NASA Astrophysics Data System (ADS)

Dwivedi, Prashant Povel; Kumar, Challa Sesha Sai Pavan; Choi, Hee Joo; Cha, Myoungsik

2016-02-01

Random duty-cycle error (RDE) is inherent in the fabrication of ferroelectric quasi-phase-matching (QPM) gratings. Although a small RDE may not affect the nonlinearity of QPM devices, it enhances non-phase-matched parasitic harmonic generations, limiting the device performance in some applications. Recently, we demonstrated a simple method for measuring the RDE in QPM gratings by analyzing the far-field diffraction pattern obtained by uniform illumination (Dwivedi et al. in Opt Express 21:30221-30226, 2013). In the present study, we used a Gaussian beam illumination for the diffraction experiment to measure noise spectra that are less affected by the pedestals of the strong diffraction orders. Our results were compared with our calculations based on a random grating model, demonstrating improved resolution in the RDE estimation.

Multi-resonance peaks fiber Bragg gratings based on largely-chirped structure

NASA Astrophysics Data System (ADS)

Chen, Chao; Zhang, Xuan-Yu; Wei, Wei-Hua; Chen, Yong-Yi; Qin, Li; Ning, Yong-Qiang; Yu, Yong-Sen

2018-04-01

A composite fiber Bragg grating (FBG) with multi-resonance peaks (MRPs) has been realized by using femtosecond (fs) laser point-by-point inscription in single-mode fiber. This device contains a segment of largely-chirped gratings with the ultrahigh chirp coefficients and a segment of uniform high-order gratings. The observed MRPs are distributed in an ultra-broadband wavelength range from 1200 nm to 1700 nm in the form of quasi-period or multi-peak-group. For the 8th-order MRPs-FBG, we studied the axial strain and high-temperature sensing characteristics of different resonance peaks experimentally. Moreover, we have demonstrated a multi-wavelength fiber lasers with three-wavelength stable output by using a 9th-order MRPs-FBG as the wavelength selector. This work is significant for the fabrication and functionalization of FBGs with complicated spectra characteristics.

Wide-field-of-view nanoscale Bragg liquid crystal polarization gratings

NASA Astrophysics Data System (ADS)

Xiang, Xiao; Kim, Jihwan; Escuti, Michael J.

2018-02-01

Here, we demonstrate a liquid crystal (LC) polymer Bragg polarization grating (PG) with large angular band- width and high efficiency in transmission-mode for 532 nm wavelength and 400 nm period. The field-of-view (FOV ) is increased significantly while preserving high diffraction efficiency by realizing a monolithic grating comprising two different slants. Using rigorous coupled-wave analysis simulation, we identified a structure with 48° FOV and 70% average first-order efficiency. We then experimentally fabricated and characterized the grating with a photo-aligned LC polymer network, also known as reactive mesogens. We measured 40° FOV and nearly 80% average diffraction efficiency. With this broadened and fairly uniform angular response, this wide FOV Bragg PG is a compelling option for large deflection-angle applications, including near-eye display in augmented reality systems, waveguide based illumination, and beam steering.

Design of a holographic waveguide with L configuration

NASA Astrophysics Data System (ADS)

Xiang, Guangxin-Xin; Li, Wen-Qiang

2016-10-01

In order to decrease the complexity to design and manufacture the turning grating of the configuration with one reflecting surface, an L-shape two-dimension extended configuration with single plate is given in the paper. This configuration consists of one specular reflecting surface and three holographic gratings two in which periods and the groove orientations are totally same, which makes gratings design and fabrication easier. According to the calculation and analysis to the optical path of configuration, the dimension of the turning grating is no larger than 40mm×30mm. The simulation result demonstrates the display configuration is reasonable and correct and can realize the display effect with 30°×30° field of view and Φ30mm large exit pupil. This configuration can be applied to an Augmented Reality Display (AR) or a Head-Mounted Display (HMD).

Narrow-stripe broad-area lasers with distributed-feedback surface gratings as brilliant sources for high power spectral beam combining systems

NASA Astrophysics Data System (ADS)

Decker, J.; Crump, P.; Fricke, J.; Wenzel, H.; Maaβdorf, A.; Erbert, G.; Tränkle, G.

2014-03-01

Laser systems based on spectral beam combining (SBC) of broad-area (BA) diode lasers are promising tools for material processing applications. However, the system brightness is limited by the in-plane beam param- eter product, BPP, of the BA lasers, which operate with a BPP of < 3mm-mrad. The EU project BRIDLE (www.bridle.eu) is developing novel diode laser sources for such systems, and several technological advances are sought. For increased system brightness and optimal ber-coupling the diode lasers should operate with reduced BPP and vertical far eld angle (95% power content), μV 95. The resulting diode lasers are fabricated as mini- bars for reduced assembly costs. Gratings are integrated into the mini-bar, with each laser stripe emitting at a different wavelength. In this way, each emitter can be directed into a single bre via low-cost dielectric filters. Distributed-feedback narrow-stripe broad-area (DFB-NBA) lasers are promising candidates for these SBC sys- tems. We review here the design process and performance achieved, showing that DFB-NBA lasers with stripe width, W = 30 μm, successfully cut of higher-order lateral modes, improving BPP. Uniform, surface-etched, 80th-order Bragg gratings are used, with weak gratings essential for high e ciency. To date, such DFB-NBA sources operate with < 50% effciency at output power, Pout < 6 W, with BPP < 1.8 mm-mrad and offV 95 36 . The emission wavelength is about 970 nm and the spectral width is < 0.7 nm (95% power). The BPP is half that of a DFB-BA lasers with W = 90 um. We conclude with a review of options for further performance improvements.

A glucose concentration and temperature sensor based on long period fiber gratings induced by electric-arc discharge

NASA Astrophysics Data System (ADS)

Du, Chao; Wang, Qi

2017-10-01

As one of the key parameters in biological and chemical reactions, glucose concentration objectively reflects the characteristics of reactions, so the real-time monitoring of glucose concentration is important in the field of biochemical. Meanwhile, the influence from temperature should be considered. The fiber sensors have been studied extensively for decades due to the advantages of small size, immunity to electromagnetic interference and high sensitivity, which are suitable for the application of biochemical sensing. A long period fiber grating (LPFG) sensor induced by electric-arc discharge has been fabricated and demonstrated for simultaneous measurement of glucose concentration and temperature. The proposed sensor was fabricated by inscribing a sing mode fiber (SMF) with periodic electric-arc discharge technology. During the fabrication process, the electric-arc discharge technology was produced by a commercial fusion splicer, and the period of inscribed LPFG was determined by the movement of translation stages. A serials of periodic geometrical deformations would be formed in SMF after the fabrication, and the discharge intensity and discharge time can be adjusted though the fusion splicer settings screen. The core mode can be coupled into the cladding modes at certain wavelength when they satisfy the phase-matching conditions, and there will be several resonance dips in the transmission spectrum in LPFG. The resonance dips formed by the coupling between cladding modes and core mode have different sensitivity responses, so the simultaneous measurement for multi-parameter can be realized by monitoring the wavelength shifts of the resonance dips. Compared with the LPFG based on conventional SMF, the glucose concentration sensitivity has been obviously enhanced by etching the cladding with hydrofluoric acid solution. Based on the independent measured results, a dual-parameter measurement matrix has been built for signal demodulation. Because of the easy fabrication, low cost, small size and high sensitivity, the sensor is promising to be used for the biochemical sensing field where simultaneous measurement of glucose concentration and temperature is required.

Enabling laboratory EUV research with a compact exposure tool

NASA Astrophysics Data System (ADS)

Brose, Sascha; Danylyuk, Serhiy; Tempeler, Jenny; Kim, Hyun-su; Loosen, Peter; Juschkin, Larissa

2016-03-01

In this work we present the capabilities of the designed and realized extreme ultraviolet laboratory exposure tool (EUVLET) which has been developed at the RWTH-Aachen, Chair for the Technology of Optical Systems (TOS), in cooperation with the Fraunhofer Institute for Laser Technology (ILT) and Bruker ASC GmbH. Main purpose of this laboratory setup is the direct application in research facilities and companies with small batch production, where the fabrication of high resolution periodic arrays over large areas is required. The setup can also be utilized for resist characterization and evaluation of its pre- and post-exposure processing. The tool utilizes a partially coherent discharge produced plasma (DPP) source and minimizes the number of other critical components to a transmission grating, the photoresist coated wafer and the positioning system for wafer and grating and utilizes the Talbot lithography approach. To identify the limits of this approach first each component is analyzed and optimized separately and relations between these components are identified. The EUV source has been optimized to achieve the best values for spatial and temporal coherence. Phase-shifting and amplitude transmission gratings have been fabricated and exposed. Several commercially available electron beam resists and one EUV resist have been characterized by open frame exposures to determine their contrast under EUV radiation. Cold development procedure has been performed to further increase the resist contrast. By analyzing the exposure results it can be demonstrated that only a 1:1 copy of the mask structure can be fully resolved by the utilization of amplitude masks. The utilized phase-shift masks offer higher 1st order diffraction efficiency and allow a demagnification of the mask structure in the achromatic Talbot plane.

Hybrid grating reflectors: Origin of ultrabroad stopband

DOE Office of Scientific and Technical Information (OSTI.GOV)

Park, Gyeong Cheol; Taghizadeh, Alireza; Chung, Il-Sug, E-mail: ilch@fotonik.dtu.dk

2016-04-04

Hybrid grating (HG) reflectors with a high-refractive-index cap layer added onto a high contrast grating (HCG) provide a high reflectance close to 100% over a broader wavelength range than HCGs. The combination of a cap layer and a grating layer brings a strong Fabry-Perot (FP) resonance as well as a weak guided mode (GM) resonance. Most of the reflected power results from the FP resonance, while the GM resonance plays a key role in achieving a reflectance close to 100% as well as broadening the stopband. An HG sample with 7 InGaAlAs quantum wells included in the cap layer hasmore » been fabricated by directly wafer-bonding a III-V cap layer onto a Si grating layer. Its reflection property has been characterized. This heterogeneously integrated HG reflector may allow for a hybrid III-V on Si laser to be thermally efficient, which has promising prospects for silicon photonics light sources and high-speed operation.« less

Influence of Passivation Layers for Metal Grating-Based Quantum Well Infrared Photodetectors

NASA Astrophysics Data System (ADS)

Liu, Dong; Fu, Yong-Qi; Yang, Le-Chen; Zhang, Bao-Shun; Li, Hai-Jun; Fu, Kai; Xiong, Min

2012-06-01

To improve absorption of quantum well infrared photodetectors (QWIPs), a coupling layer with metallic grating is designed and fabricated above the quantum well. The metal grating is composed of 100 nm Au film on top, and a 20-nm Ti thin layer between the Au film and the sapphire substrate is coated as an adhesion/buffer layer. To protect the photodetector from oxidation and to decrease leakage, a SiO2 film is deposited by means of plasma-enhanced chemical vapor deposition. A value of about 800 nm is an optimized thickness for the SiO2 applied in the metallic grating-based mid-infrared QWIP. In addition, a QWIP passivation layer is studied experimentally. The results demonstrate that the contribution from the layer is positive for metal grating coupling with the quantum well. The closer the permittivity of the two dielectric layers (SiO2 and the passivation layers), and the closer the two transmission peaks, the greater the QWIP enhancement will be.

Efficiency calibration of the first multilayer-coated holographic ion-etched flight grating for a sounding rocket high-resolution spectrometer.

PubMed

Kowalski, M P; Barbee, T W; Heidemann, K F; Gursky, H; Rife, J C; Hunter, W R; Fritz, G G; Cruddace, R G

1999-11-01

We have fabricated the four flight gratings for a sounding rocket high-resolution spectrometer using a holographic ion-etching technique. The gratings are spherical (4000-mm radius of curvature), large (160 mm x 90 mm), and have a laminar groove profile of high density (3600 grooves/mm). They have been coated with a high-reflectance multilayer of Mo/Si. Using an atomic force microscope, we examined the surface characteristics of the first grating before and after multilayer coating. The average roughness is approximately 3 A rms after coating. Using synchrotron radiation, we completed an efficiency calibration map over the wavelength range 225-245 A. At an angle of incidence of 5 degrees and a wavelength of 234 A, the average efficiency in the first inside order is 10.4 +/- 0.5%, and the derived groove efficiency is 34.8 +/- 1.6%. These values exceed all previously published results for a high-density grating.

A Near-Infrared Spectrometer Based on Novel Grating Light Modulators

PubMed Central

Wei, Wei; Huang, Shanglian; Wang, Ning; Jin, Zhu; Zhang, Jie; Chen, Weimin

2009-01-01

A near-infrared spectrometer based on novel MOEMS grating light modulators is proposed. The spectrum detection method that combines a grating light modulator array with a single near-infrared detector has been applied. Firstly, optics theory has been used to analyze the essential principles of the proposed spectroscopic sensor. Secondly, the grating light modulators have been designed and fabricated by micro-machining technology. Finally, the principles of this spectroscopic sensor have been validated and its key parameters have been tested by experiments. The result shows that the spectral resolution is better than 10 nm, the wavelength deviation is less than 1 nm, the deviation of the intensity of peak wavelength is no more than 0.5%, the driving voltage of grating light modulators array device is below 25 V and the response frequency of it is about 5 kHz. With low cost, satisfactory precision, portability and other advantages, the spectrometer should find potential applications in food safety and quality monitoring, pharmaceutical identification and agriculture product quality classification. PMID:22574065

A near-infrared spectrometer based on novel grating light modulators.

PubMed

Wei, Wei; Huang, Shanglian; Wang, Ning; Jin, Zhu; Zhang, Jie; Chen, Weimin

2009-01-01

A near-infrared spectrometer based on novel MOEMS grating light modulators is proposed. The spectrum detection method that combines a grating light modulator array with a single near-infrared detector has been applied. Firstly, optics theory has been used to analyze the essential principles of the proposed spectroscopic sensor. Secondly, the grating light modulators have been designed and fabricated by micro-machining technology. Finally, the principles of this spectroscopic sensor have been validated and its key parameters have been tested by experiments. The result shows that the spectral resolution is better than 10 nm, the wavelength deviation is less than 1 nm, the deviation of the intensity of peak wavelength is no more than 0.5%, the driving voltage of grating light modulators array device is below 25 V and the response frequency of it is about 5 kHz. With low cost, satisfactory precision, portability and other advantages, the spectrometer should find potential applications in food safety and quality monitoring, pharmaceutical identification and agriculture product quality classification.

Photoalignment and resulting holographic vector grating formation in composites of low molecular weight liquid crystals and photoreactive liquid crystalline polymers

NASA Astrophysics Data System (ADS)

Sasaki, Tomoyuki; Shoho, Takashi; Goto, Kohei; Noda, Kohei; Kawatsuki, Nobuhiro; Ono, Hiroshi

2015-08-01

Polarization holographic gratings were formed in liquid crystal (LC) cells fabricated from a mixture of low molecular weight nematic LC and a photoreactive liquid crystalline polymer (PLCP) with 4-(4-methoxycinnamoyloxy)biphenyl side groups. The diffraction properties of the gratings were analyzed using theoretical models which were determined based on the polarization patterns of the polarization holography. The results demonstrated that vector gratings comprised of periodic orientation distributions of the LC molecule were induced in the cells based on the axis-selective photoreaction of the PLCP. The vector gratings were erased by applying a sufficiently high voltage to the cells and then were reformed with no hysteresis after the voltage was removed. This phenomenon suggested that the PLCP molecules were stabilized based on the axis-selective photocrosslink reaction and that the LC molecules were aligned by the photocrosslinked PLCP. This LC composite with axis-selective photoreactivity is useful for various optical applications, because of their stability, transparency, and response to applied voltage.

Normal incidence spectrophotometer using high density transmission grating technology and highly efficiency silicon photodiodes for absolute solar EUV irradiance measurements

NASA Technical Reports Server (NTRS)

Ogawa, H. S.; Mcmullin, D.; Judge, D. L.; Korde, R.

1992-01-01

New developments in transmission grating and photodiode technology now make it possible to realize spectrometers in the extreme ultraviolet (EUV) spectral region (wavelengths less than 1000 A) which are expected to be virtually constant in their diffraction and detector properties. Time dependent effects associated with reflection gratings are eliminated through the use of free standing transmission gratings. These gratings together with recently developed and highly stable EUV photodiodes have been utilized to construct a highly stable normal incidence spectrophotometer to monitor the variability and absolute intensity of the solar 304 A line. Owing to its low weight and compactness, such a spectrometer will be a valuable tool for providing absolute solar irradiance throughout the EUV. This novel instrument will also be useful for cross-calibrating other EUV flight instruments and will be flown on a series of Hitchhiker Shuttle Flights and on SOHO. A preliminary version of this instrument has been fabricated and characterized, and the results are described.

Recent Developments in Fiber Optics Humidity Sensors.

PubMed

Ascorbe, Joaquin; Corres, Jesus M; Arregui, Francisco J; Matias, Ignacio R

2017-04-19

A wide range of applications such as health, human comfort, agriculture, food processing and storage, and electronic manufacturing, among others, require fast and accurate measurement of humidity. Sensors based on optical fibers present several advantages over electronic sensors and great research efforts have been made in recent years in this field. The present paper reports the current trends of optical fiber humidity sensors. The evolution of optical structures developed towards humidity sensing, as well as the novel materials used for this purpose, will be analyzed. Well-known optical structures, such as long-period fiber gratings or fiber Bragg gratings, are still being studied towards an enhancement of their sensitivity. Sensors based on lossy mode resonances constitute a platform that combines high sensitivity with low complexity, both in terms of their fabrication process and the equipment required. Novel structures, such as resonators, are being studied in order to improve the resolution of humidity sensors. Moreover, recent research on polymer optical fibers suggests that the sensitivity of this kind of sensor has not yet reached its limit. Therefore, there is still room for improvement in terms of sensitivity and resolution.

Recent Developments in Fiber Optics Humidity Sensors

PubMed Central

Ascorbe, Joaquin; Corres, Jesus M.; Arregui, Francisco J.; Matias, Ignacio R.

2017-01-01

A wide range of applications such as health, human comfort, agriculture, food processing and storage, and electronic manufacturing, among others, require fast and accurate measurement of humidity. Sensors based on optical fibers present several advantages over electronic sensors and great research efforts have been made in recent years in this field. The present paper reports the current trends of optical fiber humidity sensors. The evolution of optical structures developed towards humidity sensing, as well as the novel materials used for this purpose, will be analyzed. Well-known optical structures, such as long-period fiber gratings or fiber Bragg gratings, are still being studied towards an enhancement of their sensitivity. Sensors based on lossy mode resonances constitute a platform that combines high sensitivity with low complexity, both in terms of their fabrication process and the equipment required. Novel structures, such as resonators, are being studied in order to improve the resolution of humidity sensors. Moreover, recent research on polymer optical fibers suggests that the sensitivity of this kind of sensor has not yet reached its limit. Therefore, there is still room for improvement in terms of sensitivity and resolution. PMID:28422074

A green-color portable waveguide eyewear display system

NASA Astrophysics Data System (ADS)

Xia, Lingbo; Xu, Ke; Wu, Zhengming; Hu, Yingtian; Li, Zhenzhen; Wang, Yongtian; Liu, Juan

2013-08-01

Waveguide display systems are widely used in various display fields, especially in head mounted display. Comparing with the traditional head mounted display system, this device dramatically reduce the size and mass. However, there are still several fatal problems such as high scatting, the cumbersome design and chromatic aberration that should be solved. We designed and fabricated a monochromatic portable eyewear display system consist of a comfortable eyewear device and waveguide system with two holographic gratings located on the substrate symmetrically. We record the gratings on the photopolymer medium with high efficiency and wavelength sensitivity. The light emitting from the micro-display is diffracted by the grating and trapped in the glass substrate by total internal reflection. The relationship between the diffraction efficiency and exposure value is studied and analyzed, and we fabricated the gratings with appropriate diffraction efficiency in a optimization condition. To avoid the disturbance of the stray light, we optimize the waveguide system numerically and perform the optical experiments. With this system, people can both see through the waveguide to obtain the information outside and catch the information from the micro display. After considering the human body engineering and industrial production, we design the structure in a compact and portable way. It has the advantage of small-type configuration and economic acceptable. It is believe that this kind of planar waveguide system is a potentially replaceable choice for the portable devices in future mobile communications.

An acousto-optic sensor based on resonance grating waveguide structure

PubMed Central

Xie, Antonio Jou; Song, Fuchuan; Seo, Sang-Woo

2014-01-01

This paper presents an acousto-optic (AO) sensor based on resonance grating waveguide structure. The sensor is fabricated using elastic polymer materials to achieve a good sensitivity to ultrasound pressure waves. Ultrasound pressure waves modify the structural parameters of the sensor and result in the optical resonance shift of the sensor. This converts into a light intensity modulation. A commercial ultrasound transducer at 20 MHz is used to characterize a fabricated sensor and detection sensitivity at different optical source wavelength within a resonance spectrum is investigated. Practical use of the sensor at a fixed optical source wavelength is presented. Ultimately, the geometry of the planar sensor structure is suitable for two-dimensional, optical pressure imaging applications such as pressure wave detection and mapping, and ultrasound imaging. PMID:25045203

Temperature and refractive index measurements using long-period fiber gratings fabricated by femtosecond laser

NASA Astrophysics Data System (ADS)

Yu, Yongqin; Zheng, Jiarong; Yi, Kai; Ruan, Shuangchen; Du, Chenlin; Huang, Jianhui; Zhong, Wansheng

2011-12-01

Long period fiber gratings (LPFGs) with different periods in the standard single mode fiber were fabricated, using laser direct writing method, by femtosecond laser pulses with pulse width of 200 fs and the repetition rate of 250 kHz at a center wavelength of 800 nm in air. Comparative with bare LPFG in temperature sensor, LPFG had been encapsulated using large coefficient of thermal expansion of epoxy polymer and Aluminum to enhance the temperature sensitivity. The results showed that the temperature sensitivity of encapsulated LPFG was 2 times than that of bare LPFG. In addition, we also researched the relationship between resonant wavelength and surrounding refractive index (SRI) when LPFG immersed in refractive index of solution of different index at 20 degree Celsius.

Vectorial strain gauge method using single flexible orthogonal polydimethylsiloxane gratings

NASA Astrophysics Data System (ADS)

Guo, Hao; Tang, Jun; Qian, Kun; Tsoukalas, Dimitris; Zhao, Miaomiao; Yang, Jiangtao; Zhang, Binzhen; Chou, Xiujian; Liu, Jun; Xue, Chenyang; Zhang, Wendong

2016-03-01

A vectorial strain gauge method using a single sensing element is reported based on the double-sided polydimethylsiloxane (PDMS) Fraunhofer diffraction gratings structures. Using O2 plasma treatment steps, orthogonal wrinkled gratings were fabricated on both sides of a pre-strained PDMS film. Diffracted laser spots from this structure have been used to experimentally demonstrate, that any applied strain can be quantitatively characterized in both the x and y directions with an error of less than 0.6% and with a gauge factor of approximately 10. This simple and low cost technology which is completely different from the traditional vectorial strain gauge method, can be applied to surface vectorial strain measurement and multi-axis integrated mechanical sensors.

In-line metrology for roll-to-roll UV assisted nanoimprint lithography using diffractometry

NASA Astrophysics Data System (ADS)

Kreuzer, Martin; Whitworth, Guy L.; Francone, Achille; Gomis-Bresco, Jordi; Kehagias, Nikolaos; Sotomayor-Torres, Clivia M.

2018-05-01

We describe and discuss the optical design of a diffractometer to carry out in-line quality control during roll-to-roll nanoimprinting. The tool measures diffractograms in reflection geometry, through an aspheric lens to gain fast, non-invasive information of any changes to the critical dimensions of target grating structures. A stepwise tapered linear grating with constant period was fabricated in order to detect the variation in grating linewidth through diffractometry. The minimum feature change detected was ˜40 nm to a precision of 10 nm. The diffractometer was then integrated with a roll-to-roll UV assisted nanoimprint lithography machine to gain dynamic measurements in situ.

Compact beam splitters with deep gratings for miniature photonic integrated circuits: design and implementation aspects.

PubMed

Chen, Chin-Hui; Klamkin, Jonathan; Nicholes, Steven C; Johansson, Leif A; Bowers, John E; Coldren, Larry A

2009-09-01

We present an extensive study of an ultracompact grating-based beam splitter suitable for photonic integrated circuits (PICs) that have stringent density requirements. The 10 microm long beam splitter exhibits equal splitting, low insertion loss, and also provides a high extinction ratio in an integrated coherent balanced receiver. We further present the design strategies for avoiding mode distortion in the beam splitter and discuss optimization of the widths of the detectors to improve insertion loss and extinction ratio of the coherent receiver circuit. In our study, we show that the grating-based beam splitter is a competitive technology having low fabrication complexity for ultracompact PICs.

Self-aligned grating couplers on template-stripped metal pyramids via nanostencil lithography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Klemme, Daniel J.; Johnson, Timothy W.; Mohr, Daniel A.

2016-05-23

We combine nanostencil lithography and template stripping to create self-aligned patterns about the apex of ultrasmooth metal pyramids with high throughput. Three-dimensional patterns such as spiral and asymmetric linear gratings, which can couple incident light into a hot spot at the tip, are presented as examples of this fabrication method. Computer simulations demonstrate that spiral and linear diffraction grating patterns are both effective at coupling light to the tip. The self-aligned stencil lithography technique can be useful for integrating plasmonic couplers with sharp metallic tips for applications such as near-field optical spectroscopy, tip-based optical trapping, plasmonic sensing, and heat-assisted magneticmore » recording.« less

Ultra compact triplexing filters based on SOI nanowire AWGs

NASA Astrophysics Data System (ADS)

Jiashun, Zhang; Junming, An; Lei, Zhao; Shijiao, Song; Liangliang, Wang; Jianguang, Li; Hongjie, Wang; Yuanda, Wu; Xiongwei, Hu

2011-04-01

An ultra compact triplexing filter was designed based on a silicon on insulator (SOI) nanowire arrayed waveguide grating (AWG) for fiber-to-the-home FTTH. The simulation results revealed that the design performed well in the sense of having a good triplexing function. The designed SOI nanowire AWGs were fabricated using ultraviolet lithography and induced coupler plasma etching. The experimental results showed that the crosstalk was less than -15 dB, and the 3 dB-bandwidth was 11.04 nm. The peak wavelength output from ports a, c, and b were 1455, 1510 and 1300 nm, respectively, which deviated from our original expectations. The deviation of the wavelength is mainly caused by 45 nm width deviation of the arrayed waveguides during the course of the fabrication process and partly caused by material dispersion.

Nanoimprinted photonic crystal color filters for solar-powered reflective displays.

PubMed

Cho, Eun-Hyoung; Kim, Hae-Sung; Sohn, Jin-Seung; Moon, Chang-Youl; Park, No-Cheol; Park, Young-Pil

2010-12-20

A novel concept for reflective displays that uses two-dimensional photonic crystals with subwavelength gratings is introduced. A solar-powered reflective display with photonic crystal color filters was analyzed by a theoretical approach. We fabricated the photonic crystal color filters on a glass substrate by using low-cost nanoimprint lithography and multi-scan excimer laser annealing to produce RGB color filters through a single patterning process. The theoretical and experimental results show that the color filters have high reflectance and angular tolerance, which was qualitatively confirmed by chromaticity coordination analysis.

A Micromachined Geometric Moire Interferometric Floating-Element Shear Stress Sensor

NASA Technical Reports Server (NTRS)

Horowitz, S.; Chen, T.; Chandrasekaran, V.; Tedjojuwono, K.; Nishida, T.; Cattafesta, L.; Sheplak, M.

2004-01-01

This paper presents the development of a floating-element shear stress sensor that permits the direct measurement of skin friction based on geometric Moir interferometry. The sensor was fabricated using an aligned wafer-bond/thin-back process producing optical gratings on the backside of a floating element and on the top surface of the support wafer. Experimental characterization indicates a static sensitivity of 0.26 microns/Pa, a resonant frequency of 1.7 kHz, and a noise floor of 6.2 mPa/(square root)Hz.

Electrically-programmable diffraction grating

DOEpatents

Ricco, Antonio J.; Butler, Michael A.; Sinclair, Michael B.; Senturia, Stephen D.

1998-01-01

An electrically-programmable diffraction grating. The programmable grating includes a substrate having a plurality of electrodes formed thereon and a moveable grating element above each of the electrodes. The grating elements are electrostatically programmable to form a diffraction grating for diffracting an incident beam of light as it is reflected from the upper surfaces of the grating elements. The programmable diffraction grating, formed by a micromachining process, has applications for optical information processing (e.g. optical correlators and computers), for multiplexing and demultiplexing a plurality of light beams of different wavelengths (e.g. for optical fiber communications), and for forming spectrometers (e.g. correlation and scanning spectrometers).

The re-flight of the Colorado high-resolution Echelle stellar spectrograph (CHESS): improvements, calibrations, and post-flight results

NASA Astrophysics Data System (ADS)

Hoadley, Keri; France, Kevin; Kruczek, Nicholas; Fleming, Brian; Nell, Nicholas; Kane, Robert; Swanson, Jack; Green, James; Erickson, Nicholas; Wilson, Jacob

2016-07-01

In this proceeding, we describe the scientific motivation and technical development of the Colorado High- resolution Echelle Stellar Spectrograph (CHESS), focusing on the hardware advancements and testing supporting the second flight of the payload (CHESS-2). CHESS is a far ultraviolet (FUV) rocket-borne instrument designed to study the atomic-to-molecular transitions within translucent cloud regions in the interstellar medium (ISM). CHESS is an objective f/12.4 echelle spectrograph with resolving power > 100,000 over the band pass 1000 - 1600 Å. The spectrograph was designed to employ an R2 echelle grating with "low" line density. We compare the FUV performance of experimental echelle etching processes (lithographically by LightSmyth, Inc. and etching via electron-beam technology by JPL Microdevices Laboratory) with traditional, mechanically-ruled gratings (Bach Research, Inc. and Richardson Gratings). The cross-dispersing grating, developed and ruled by Horiba Jobin-Yvon, is a holographically-ruled, "low" line density, powered optic with a toroidal surface curvature. Both gratings were coated with aluminum and lithium fluoride (Al+LiF) at Goddard Space Flight Center (GSFC). Results from final efficiency and reflectivity measurements for the optical components of CHESS-2 are presented. CHESS-2 utilizes a 40mm-diameter cross-strip anode readout microchannel plate (MCP) detector fabricated by Sensor Sciences, Inc., to achieve high spatial resolution with high count rate capabilities (global rates 1 MHz). We present pre-flight laboratory spectra and calibration results. CHESS-2 launched on 21 February 2016 aboard NASA/CU sounding rocket mission 36.297 UG. We observed the intervening ISM material along the sightline to epsilon Per and present initial characterization of the column densities, temperature, and kinematics of atomic and molecular species in the observation.

Design and experiment of spectrometer based on scanning micro-grating integrating with angle sensor

NASA Astrophysics Data System (ADS)

Biao, Luo; Wen, Zhi-yu

2014-01-01

A compact, low cost, high speed, non-destructive testing NIR (near infrared) spectrometer optical system based on MOEMS grating device is developed. The MOEMS grating works as the prismatic element and wavelength scanning element in our optical system. The MOEMS grating enables the design of compact grating spectrometers capable of acquiring full spectra using a single detector element. This MOEMS grating is driven by electromagnetic force and integrated with angle sensor which used to monitored deflection angle while the grating working. Comparing with the traditional spectral system, there is a new structure with a single detector and worked at high frequency. With the characteristics of MOEMS grating, the structure of the spectrometer system is proposed. After calculating the parameters of the optical path, ZEMAX optical software is used to simulate the system. According the ZEMAX output file of the 3D model, the prototype is designed by SolidWorks rapidly, fabricated. Designed for a wavelength range between 800 nm and 1500 nm, the spectrometer optical system features a spectral resolution of 16 nm with the volume of 97 mm × 81.7 mm × 81 mm. For the purpose of reduce modulated effect of sinusoidal rotation, spectral intensity of the different wavelength should be compensated by software method in the further. The system satisfies the demand of NIR micro-spectrometer with a single detector.

Distributed feedback InGaN/GaN laser diodes

NASA Astrophysics Data System (ADS)

Slight, Thomas J.; Watson, Scott; Yadav, Amit; Grzanka, Szymon; Stanczyk, Szymon; Docherty, Kevin E.; Rafailov, Edik; Perlin, Piotr; Najda, Steve; Leszczyński, Mike; Kelly, Anthony E.

2018-02-01

We have realised InGaN/GaN distributed feedback laser diodes emitting at a single wavelength in the 42X nm wavelength range. Laser diodes based on Gallium Nitride (GaN) are useful devices in a wide range of applications including atomic spectroscopy, data storage and optical communications. To fully exploit some of these application areas there is a need for a GaN laser diode with high spectral purity, e.g. in atomic clocks, where a narrow line width blue laser source can be used to target the atomic cooling transition. Previously, GaN DFB lasers have been realised using buried or surface gratings. Buried gratings require complex overgrowth steps which can introduce epi-defects. Surface gratings designs, can compromise the quality of the p-type contact due to dry etch damage and are prone to increased optical losses in the grating regions. In our approach the grating is etched into the sidewall of the ridge. Advantages include a simpler fabrication route and design freedom over the grating coupling strength.Our intended application for these devices is cooling of the Sr+ ion and for this objective the laser characteristics of SMSR, linewidth, and power are critical. We investigate how these characteristics are affected by adjusting laser design parameters such as grating coupling coefficient and cavity length.

Image grating metrology using phase-stepping interferometry in scanning beam interference lithography

NASA Astrophysics Data System (ADS)

Li, Minkang; Zhou, Changhe; Wei, Chunlong; Jia, Wei; Lu, Yancong; Xiang, Changcheng; Xiang, XianSong

2016-10-01

Large-sized gratings are essential optical elements in laser fusion and space astronomy facilities. Scanning beam interference lithography is an effective method to fabricate large-sized gratings. To minimize the nonlinear phase written into the photo-resist, the image grating must be measured to adjust the left and right beams to interfere at their waists. In this paper, we propose a new method to conduct wavefront metrology based on phase-stepping interferometry. Firstly, a transmission grating is used to combine the two beams to form an interferogram which is recorded by a charge coupled device(CCD). Phase steps are introduced by moving the grating with a linear stage monitored by a laser interferometer. A series of interferograms are recorded as the displacement is measured by the laser interferometer. Secondly, to eliminate the tilt and piston error during the phase stepping, the iterative least square phase shift method is implemented to obtain the wrapped phase. Thirdly, we use the discrete cosine transform least square method to unwrap the phase map. Experiment results indicate that the measured wavefront has a nonlinear phase around 0.05 λ@404.7nm. Finally, as the image grating is acquired, we simulate the print-error written into the photo-resist.

Tunable dual-band nearly perfect absorption based on a compound metallic grating

NASA Astrophysics Data System (ADS)

Gao, Hua; Zheng, Zhi-Yuan; Feng, Juan

2017-02-01

Traditional metallic gratings and novel metamaterials are two basic kinds of candidates for perfect absorption. Comparatively speaking, metallic grating is the preferred choice for the same absorption effect because it is structurally simpler and more convenient to fabricate. However, to date, most of the perfect absorption effects achieved based on metamaterials are also available using an metallic grating except the tunable dual(multi)-band perfect absorption. To fill this gap, in this paper, by adding subgrooves on the rear surface as well as inside the grating slits to a free-standing metallic grating, tunable dual-band perfect absorption is also obtained for the first time. The grooves inside the slits is to tune the frequency of the Cavity Mode(CM) resonance which enhances the transmission and suppresses the reflectance simultaneously. The grooves on the rear surface give rise to the phase resonance which not only suppresses the transmission but also reinforces the reflectance depression effect. Thus, when the phase resonance and the frequency tunable CM resonance occur together, transmission and reflection can be suppressed simultaneously, dual-band nearly perfect absorption with tunable frequencies is obtained. To our knowledge, this perfect absorption phenomenon is achieved for the first time in a designed metallic grating structure.

Scanning moiré and spatial-offset phase-stepping for surface inspection of structures

NASA Astrophysics Data System (ADS)

Yoneyama, S.; Morimoto, Y.; Fujigaki, M.; Ikeda, Y.

2005-06-01

In order to develop a high-speed and accurate surface inspection system of structures such as tunnels, a new surface profile measurement method using linear array sensors is studied. The sinusoidal grating is projected on a structure surface. Then, the deformed grating is scanned by linear array sensors that move together with the grating projector. The phase of the grating is analyzed by a spatial offset phase-stepping method to perform accurate measurement. The surface profile measurements of the wall with bricks and the concrete surface of a structure are demonstrated using the proposed method. The change of geometry or fabric of structures and the defects on structure surfaces can be detected by the proposed method. It is expected that the surface profile inspection system of tunnels measuring from a running train can be constructed based on the proposed method.

Metallic layer-by-layer photonic crystals for linearly-polarized thermal emission and thermophotovoltaic device including same

DOEpatents

Lee, Jae-Hwang; Ho, Kai-Ming; Constant, Kristen P.

2016-07-26

Metallic thermal emitters consisting of two layers of differently structured nickel gratings on a homogeneous nickel layer are fabricated by soft lithography and studied for polarized thermal radiation. A thermal emitter in combination with a sub-wavelength grating shows a high extinction ratio, with a maximum value close to 5, in a wide mid-infrared range from 3.2 to 7.8 .mu.m, as well as high emissivity up to 0.65 at a wavelength of 3.7 .mu.m. All measurements show good agreement with theoretical predictions. Numerical simulations reveal that a high electric field exists within the localized air space surrounded by the gratings and the intensified electric-field is only observed for the polarizations perpendicular to the top sub-wavelength grating. This result suggests how the emissivity of a metal can be selectively enhanced at a certain range of wavelengths for a given polarization.

Optical superimposed vortex beams generated by integrated holographic plates with blazed grating

NASA Astrophysics Data System (ADS)

Zhang, Xue-Dong; Su, Ya-Hui; Ni, Jin-Cheng; Wang, Zhong-Yu; Wang, Yu-Long; Wang, Chao-Wei; Ren, Fei-Fei; Zhang, Zhen; Fan, Hua; Zhang, Wei-Jie; Li, Guo-Qiang; Hu, Yan-Lei; Li, Jia-Wen; Wu, Dong; Chu, Jia-Ru

2017-08-01

In this paper, we demonstrate that the superposition of two vortex beams with controlled topological charges can be realized by integrating two holographic plates with blazed grating. First, the holographic plate with blazed grating was designed and fabricated by laser direct writing for generating well-separated vortex beam. Then, the relationship between the periods of blazed grating and the discrete angles of vortex beams was systemically investigated. Finally, through setting the discrete angle and different revolving direction of the holographic plates, the composite fork-shaped field was realized by the superposition of two vortex beams in a particular position. The topological charges of composite fork-shaped field (l = 1, 0, 3, and 4) depend on the topological charges of compositional vortex beams, which are well agreed with the theoretical simulation. The method opens up a wide range of opportunities and possibilities for applying in optical communication, optical manipulations, and photonic integrated circuits.

Fused silica GRISMs manufactured by hydrophilic direct bonding at moderate heating

NASA Astrophysics Data System (ADS)

Kalkowski, G.; Grabowski, K.; Harnisch, G.; Flügel-Paul, T.; Zeitner, U.; Risse, S.

2017-12-01

For high-resolution spectroscopy in space, GRISM elements—obtained by patterning gratings onto a prism surface—find increasing applications. We report on GRISM manufacturing by joining the individual functional elements—prisms and gratings—to suitable components by the technology of hydrophilic direct bonding. Fused silica was used as a substrate material and binary gratings were fabricated by standard e-beam lithography and dry etching. Alignment of the grating dispersion direction to the prism angle was realized by passive adjustment on dedicated bonding gear matched to the substrate geometry. Materials adapted bonds of high transmission, stiffness, and strength were obtained after heat treatment at temperatures of about 200 °C in vacuum. Examples for bonding uncoated as well as coated grating surfaces are given. The results illustrate the great potential of hydrophilic glass direct bonding for manufacturing transmission optics to be used in space or other heavy duty applications.

Weakly modulated silicon-dioxide-cladding gratings for silicon waveguide Fabry-Pérot cavities.

PubMed

Grote, Richard R; Driscoll, Jeffrey B; Biris, Claudiu G; Panoiu, Nicolae C; Osgood, Richard M

2011-12-19

We show by theory and experiment that silicon-dioxide-cladding gratings for Fabry-Pérot cavities on silicon-on-insulator channel ("wire") waveguides provide a low-refractive-index perturbation, which is required for several important integrated photonics components. The underlying refractive index perturbation of these gratings is significantly weaker than that of analogous silicon gratings, leading to finer control of the coupling coefficient κ. Our Fabry-Pérot cavities are designed using the transfer-matrix method (TMM) in conjunction with the finite element method (FEM) for calculating the effective index of each waveguide section. Device parameters such as coupling coefficient, κ, Bragg mirror stop band, Bragg mirror reflectivity, and quality factor Q are examined via TMM modeling. Devices are fabricated with representative values of distributed Bragg reflector lengths, cavity lengths, and propagation losses. The measured transmission spectra show excellent agreement with the FEM/TMM calculations.

Development of Interference Lithography Capability Using a Helium Cadmium Ultraviolet Multimode Laser for the Fabrication of Sub-Micron-Structured Optical Materials

DTIC Science & Technology

2011-03-01

into separate parts, transmitted into different directions , and then recombined upon a surface to produce interference. The concern with this type of...photoresist (PR), is a radiation sensitive compound that is classified as positive or negative, depending on how it responds to radiation . Each is designed...emerging waves, and are referred to as diffraction gratings. Upon reflection from these kinds of gratings, light scattered from the periodic surface

Tunable Far Infrared Semiconductor Sources.

DTIC Science & Technology

1984-01-01

plasmons in Si-MOS4 hot electron transport in Si-MOS-devices a , ABSTR ACT (Coathwe st e verse 8641 It ut’.weemY dmd ideti ty by block tnmber) {fhe...After baking at 900C for 20 minutes the photoresist was -17- exposed for 8 seconds on the SUss-MJB3-contact lithography machine. To obtain grating...could fabricate Al gratings with 1.5 am - periods on Si-MOSFETs and GaAs-samples by optical contact lithography and lift-off metallization. Fig. 8 shows

Durable silver thin film coating for diffraction gratings

DOEpatents

Wolfe, Jesse D [Discovery Bay, CA; Britten, Jerald A [Oakley, CA; Komashko, Aleksey M [San Diego, CA

2006-05-30

A durable silver film thin film coated non-planar optical element has been developed to replace Gold as a material for fabricating such devices. Such a coating and resultant optical element has an increased efficiency and is resistant to tarnishing, can be easily stripped and re-deposited without modifying underlying grating structure, improves the throughput and power loading of short pulse compressor designs for ultra-fast laser systems, and can be utilized in variety of optical and spectrophotometric systems, particularly high-end spectrometers that require maximized efficiency.

The Characteristics in the Sensitivity of Microfiber Fabry-Perot Interferometric Transducers

NASA Astrophysics Data System (ADS)

Wang, Xiuxin; Li, Zhangyong; Lin, Jinzhao; Wang, Wei; Tian, Yin; Pang, Yu

2018-01-01

We inscribe a Fabry-Perot (FP) resonator in the microfiber utilizing the 193-nm UV exposure and the phase mask technique. Some new characteristics in contrast to the conventional counterparts are measured, which are attributed to the index change in the grating and the dispersion of the effective grating length, respectively. The FP spectral dependencies on external strain, temperature, and refractive index are investigated. Our fabricated structures can have potential of acting as ultrasonic transducers and photo acoustic imaging.

Highly sensitive long-period fiber-grating strain sensor with low temperature sensitivity

NASA Astrophysics Data System (ADS)

Wang, Yi-Ping; Xiao, Limin; Wang, D. N.; Jin, Wei

2006-12-01

A long-period fiber-grating sensor with a high strain sensitivity of -7.6 pm/μɛ and a low temperature sensitivity of 3.91 pm/°C is fabricated by use of focused CO2 laser beam to carve periodic grooves on a large- mode-area photonic crystal fiber. Such a strain sensor can effectively reduce the cross-sensitivity between strain and temperature, and the temperature-induced strain error obtained is only 0.5 μɛ/°C without using temperature compensation.

INTELLIGENT MONITORING SYSTEM WITH HIGH TEMPERATURE DISTRIBUTED FIBEROPTIC SENSOR FOR POWER PLANT COMBUSTION PROCESSES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kwang Y. Lee; Stuart S. Yin; Andre Boheman

2004-12-26

The objective of the proposed work is to develop an intelligent distributed fiber optical sensor system for real-time monitoring of high temperature in a boiler furnace in power plants. Of particular interest is the estimation of spatial and temporal distributions of high temperatures within a boiler furnace, which will be essential in assessing and controlling the mechanisms that form and remove pollutants at the source, such as NOx. The basic approach in developing the proposed sensor system is three fold: (1) development of high temperature distributed fiber optical sensor capable of measuring temperatures greater than 2000 C degree with spatialmore » resolution of less than 1 cm; (2) development of distributed parameter system (DPS) models to map the three-dimensional (3D) temperature distribution for the furnace; and (3) development of an intelligent monitoring system for real-time monitoring of the 3D boiler temperature distribution. Under Task 1, improvement was made on the performance of in-fiber grating fabricated in single crystal sapphire fibers, test was performed on the grating performance of single crystal sapphire fiber with new fabrication methods, and the fabricated grating was applied to high temperature sensor. Under Task 2, models obtained from 3-D modeling of the Demonstration Boiler were used to study relationships between temperature and NOx, as the multi-dimensionality of such systems are most comparable with real-life boiler systems. Studies show that in boiler systems with no swirl, the distributed temperature sensor may provide information sufficient to predict trends of NOx at the boiler exit. Under Task 3, we investigate a mathematical approach to extrapolation of the temperature distribution within a power plant boiler facility, using a combination of a modified neural network architecture and semigroup theory. The 3D temperature data is furnished by the Penn State Energy Institute using FLUENT. Given a set of empirical data with no analytic expression, we first develop an analytic description and then extend that model along a single axis.« less

Post-exposed fiber Bragg gratings

NASA Astrophysics Data System (ADS)

Miller, Gary A.

This thesis explains the development and characterization of a novel technique to fabricate weak fiber Bragg gratings for highly specific multi-element sensor arrays. This method, termed the "rescan technique," involves re-exposing a local region of a grating to fringeless ultraviolet light to "trim" unwanted portions of the reflection spectrum. The spectral effects that result from a rescan can only be adequately described by inventing the concept of a three-dimensional index growth surface, where induced index is a function of both the writing intensity and the exposure time. Using this information, it is possible to predict the spectral response of a rescanned grating using a numerical model. For our model, we have modified the piecewise-uniform approach to include coefficients within the coupled-mode formulism that imitate the same scattering properties as the actual grating. By taking high accuracy measurements of the refractive index change in germanosilicate fiber, we have created the necessary 3D map of photoinduced index to accurately model gratings and their post-exposure spectra. We will also demonstrate that optical fiber exhibits what we call "exposure history"; the final index change in a region depends on the previous exposures conditions.

Critical-angle transmission grating technology development for high resolving power soft x-ray spectrometers on Arcus and Lynx

NASA Astrophysics Data System (ADS)

Heilmann, Ralf K.; Bruccoleri, Alexander R.; Song, Jungki; Kolodziejczak, Jeffery; Gaskin, Jessica A.; O'Dell, Stephen L.; Cheimetz, Peter; Hertz, Edward; Smith, Randall K.; Burwitz, Vadim; Hartner, Gisela; La Caria, Marlis-Madeleine; Schattenburg, Mark L.

2017-08-01

Soft x-ray spectroscopy with high resolving power (R = λ/Δλ) and large effective area (A) addresses numerous unanswered science questions about the physical laws that lead to the structure of our universe. In the soft x-ray band R > 1000 can currently only be achieved with diffraction grating-based spectroscopy. Criticalangle transmission (CAT) gratings combine the advantages of blazed reflection gratings (high efficiency, use of higher diffraction orders) with those of conventional transmission gratings (relaxed alignment tolerances and temperature requirements, transparent at higher energies, low mass), resulting in minimal mission resource requirements, while greatly improving figures of merit. Diffraction efficiency > 33% and R > 10, 000 have been demonstrated for CAT gratings. Last year the technology has been certified at Technology Readiness Level 4 based on a probe class mission concept. The Explorer-scale (A > 450 cm2 , R > 2500) grating spectroscopy Arcus mission can be built with today's CAT grating technology and has been selected in the current Explorer round for a Phase A concept study. Its figure of merit for the detection of weak absorption lines will be an order of magnitude larger than current instruments on Chandra and XMM-Newton. Further CAT grating technology development and improvements in the angular resolution of x-ray optics can provide another order of magnitude improvement in performance, as is envisioned for the X-ray Surveyor/Lynx mission concept currently under development for input into the 2020 Decadal Survey. For Arcus we have tested CAT gratings in a spectrometer setup in combination with silicon pore optics (SPO) and obtained resolving power results that exceed Arcus requirements before and after environmental testing of the gratings. We have recently fabricated the largest (32 mm x 32 mm) CAT gratings to date, and plan to increase grating size further. We mounted two of these large gratings to frames and aligned them in the roll direction using a laser-based technique. Simultaneous x-ray illumination of both gratings with an SPO module demonstrated that we can exceed Arcus grating-to-grating alignment requirements without x rays.

Electrically-programmable diffraction grating

DOEpatents

Ricco, A.J.; Butler, M.A.; Sinclair, M.B.; Senturia, S.D.

1998-05-26

An electrically-programmable diffraction grating is disclosed. The programmable grating includes a substrate having a plurality of electrodes formed thereon and a moveable grating element above each of the electrodes. The grating elements are electrostatically programmable to form a diffraction grating for diffracting an incident beam of light as it is reflected from the upper surfaces of the grating elements. The programmable diffraction grating, formed by a micromachining process, has applications for optical information processing (e.g. optical correlators and computers), for multiplexing and demultiplexing a plurality of light beams of different wavelengths (e.g. for optical fiber communications), and for forming spectrometers (e.g. correlation and scanning spectrometers). 14 figs.

Multi-parameter measurements using optical fibre long period gratings for indoor air quality monitoring

NASA Astrophysics Data System (ADS)

Hromadka, J.; Korposh, S.; Partridge, M. C.; James, S.; Davis, F.; Crump, D.; Lee, S.-W.; Tatam, R. P.

2017-04-01

An array of three long period gratings (LPGs) fabricated in a single optical fibre and multiplexed in the wavelength domain was used to measure simultaneously temperature, relative humidity (RH) and volatile organic compounds (VOCs). Each LPG sensor was designed to optimize its response to a desired measurand. The LPGs were fabricated with periods such that they operated at or near the phase matching turning point. The sensors were calibrated in the laboratory and the simultaneous measurement of the key indoor air quality parameters was undertaken in laboratory and office environments. It was demonstrated successfully that the data produced by the LPG sensor array under real conditions was in a good agreement with that produced by commercially available sensors. Further, the potential application of fibre optic sensors for VOCs detection at high levels has been demonstrated.

All-Fiber Dual-Parameter Sensor Based on Cascaded Long Period Fiber Grating Pair Fabricated by Femtosecond Laser and CO2 Laser

NASA Astrophysics Data System (ADS)

Zhang, Wen; Hao, Jiaqi; Lou, Xiaoping; Dong, Mingli; Zhu, Lianqing

2018-03-01

An all-fiber dual-parameter sensor based on cascaded long period grating pair fabricated by femtosecond laser and CO2 laser has been proposed and realized both theoretically and experimentally. The resonant wavelengths of LPFGs are 1557.80 nm and 1590.88 nm. In the strain range of 0-400 με, strain sensitivities are -7.2 pm/με for C-LPFG and -1.6 pm/με for F-LPFG. In the temperature range of 30-70°C, temperature sensitivities are -41.1 pm/°C for C-LPFG and -21.2 pm/°C for F-LPFG. By analyzing the resonant wavelength characterization, the proposed sensor can be efficiently used for dual-parameters measurement with promising application prospect and great research reference value.

Measuring In-Plane Displacements with Variable Sensitivity Using Diffractive Optic Interferometry

NASA Technical Reports Server (NTRS)

Shepherd, Robert L.; Gilbert, John A.; Cole, Helen J.; Ashley, Paul R.

1998-01-01

This paper introduces a method called diffractive optic interferometry (DOI) which allows in-plane displacement components to be measured with variable sensitivity. DOI relies on binary optical elements fabricated as phase-type Dammann gratings which produce multiple diffraction orders of nearly equal intensity. Sensitivity is varied by combining the different wavefronts produced by a conjugate pair of these binary optical elements; a transmission element is used to produce several illumination beams while a reflective element, replicated on the surface of a specimen, provides the reference for the undeformed state. The steps taken to design and fabricate these binary optical elements are described. The specimen grating is characterized, and tested on a disk subjected to diametrical compression. Overall, the results are excellent, with experimental data agreeing to within a few percent of the theoretical predictions.

Deformed ellipsoidal diffraction grating blank

NASA Technical Reports Server (NTRS)

Decew, Alan E., Jr.

1994-01-01

The Deformed Ellipsoidal Grating Blank (DEGB) is the primary component in an ultraviolet spectrometer. Since one of the major concerns for these instruments is throughput, significant efforts are made to reduce the number of components and subsequently reflections. Each reflection results in losses through absorption and scattering. It is these two sources of photon loss that dictated the requirements for the DEGB. The first goal is to shape the DEGB in such a way that the energy at the entrance slit is focused as well as possible on the exit slit. The second goal is to produce a surface smooth enough to minimize the photon loss due to scattering. The program was accomplished in three phases. The first phase was the fabrication planning. The second phase was the actual fabrication and initial testing. The last phase was the final testing of the completed DEGB.

Laser recrystallization and inscription of compositional microstructures in crystalline SiGe-core fibres

PubMed Central

Coucheron, David A.; Fokine, Michael; Patil, Nilesh; Breiby, Dag Werner; Buset, Ole Tore; Healy, Noel; Peacock, Anna C.; Hawkins, Thomas; Jones, Max; Ballato, John; Gibson, Ursula J.

2016-01-01

Glass fibres with silicon cores have emerged as a versatile platform for all-optical processing, sensing and microscale optoelectronic devices. Using SiGe in the core extends the accessible wavelength range and potential optical functionality because the bandgap and optical properties can be tuned by changing the composition. However, silicon and germanium segregate unevenly during non-equilibrium solidification, presenting new fabrication challenges, and requiring detailed studies of the alloy crystallization dynamics in the fibre geometry. We report the fabrication of SiGe-core optical fibres, and the use of CO2 laser irradiation to heat the glass cladding and recrystallize the core, improving optical transmission. We observe the ramifications of the classic models of solidification at the microscale, and demonstrate suppression of constitutional undercooling at high solidification velocities. Tailoring the recrystallization conditions allows formation of long single crystals with uniform composition, as well as fabrication of compositional microstructures, such as gratings, within the fibre core. PMID:27775066

Laser recrystallization and inscription of compositional microstructures in crystalline SiGe-core fibres

NASA Astrophysics Data System (ADS)

Coucheron, David A.; Fokine, Michael; Patil, Nilesh; Breiby, Dag Werner; Buset, Ole Tore; Healy, Noel; Peacock, Anna C.; Hawkins, Thomas; Jones, Max; Ballato, John; Gibson, Ursula J.

2016-10-01

Glass fibres with silicon cores have emerged as a versatile platform for all-optical processing, sensing and microscale optoelectronic devices. Using SiGe in the core extends the accessible wavelength range and potential optical functionality because the bandgap and optical properties can be tuned by changing the composition. However, silicon and germanium segregate unevenly during non-equilibrium solidification, presenting new fabrication challenges, and requiring detailed studies of the alloy crystallization dynamics in the fibre geometry. We report the fabrication of SiGe-core optical fibres, and the use of CO2 laser irradiation to heat the glass cladding and recrystallize the core, improving optical transmission. We observe the ramifications of the classic models of solidification at the microscale, and demonstrate suppression of constitutional undercooling at high solidification velocities. Tailoring the recrystallization conditions allows formation of long single crystals with uniform composition, as well as fabrication of compositional microstructures, such as gratings, within the fibre core.

Manipulating the assembly of perovskites onto soft nanoimprinted titanium dioxide templates.

PubMed

Baca, Alfred J; Roberts, M Joseph; Stenger-Smith, John; Baldwin, Lawrence

2018-06-22

Soft nanoimprinted titanium dioxide (TiO 2 ) substrates decorated with methylammonium lead halide perovskite (MAPbI 3 ) crystals were fabricated by controlling the perovskite precursor concentration and volume during spin coat processing combined with the use of hydrophobic TiO 2 templates. The patterned growth was demonstrated with different perovskite crystallization methods. We investigated and successfully demonstrated the controlled assembly of two MAPbI 3 nanomaterials, one a nanocomposite formed between the perovskite and a hole conducting polymer poly(2,5-bis(N-methyl-N-hexylamino)phenylene vinylene) (BAMPPV), and a second formed from perovskite crystals using common solution based MAPbI 3 growth methods (1-step and 2-step processing). Both types of MAPbI 3 crystals were fabricated on hydrophobic TiO 2 nanotemplates composed of nanowells or grating patterns. Patterned areas as large as 100 μm × 100 μm were achieved. We examined and characterized the substrates using atomic force microscopy, scanning electron microscopy, x-ray diffraction, and energy dispersive spectroscopy. We present the optical properties (i.e. fluorescence and transmission) of soft nanoimprinted nanowells decorated with perovskites demonstrating the successful synthesis of MAPbI 3 perovskite nanocrystals. As an example of their use, we demonstrate a two terminal device and show photocurrent response of a perovskite patterned micro-grating. Our method is a nondestructive approach to nanopatterning perovskites, and produces patterned arrays that maintain their photo-electric properties. The results presented herein suggests an attractive route to developing nanopatterned and small area perovskite substrates for applications in photovoltaics, x-ray sensing/detection, image sensor arrays, and others.

Manipulating the assembly of perovskites onto soft nanoimprinted titanium dioxide templates

NASA Astrophysics Data System (ADS)

Baca, Alfred J.; Roberts, M. Joseph; Stenger-Smith, John; Baldwin, Lawrence

2018-06-01

Soft nanoimprinted titanium dioxide (TiO2) substrates decorated with methylammonium lead halide perovskite (MAPbI3) crystals were fabricated by controlling the perovskite precursor concentration and volume during spin coat processing combined with the use of hydrophobic TiO2 templates. The patterned growth was demonstrated with different perovskite crystallization methods. We investigated and successfully demonstrated the controlled assembly of two MAPbI3 nanomaterials, one a nanocomposite formed between the perovskite and a hole conducting polymer poly(2,5-bis(N-methyl-N-hexylamino)phenylene vinylene) (BAMPPV), and a second formed from perovskite crystals using common solution based MAPbI3 growth methods (1-step and 2-step processing). Both types of MAPbI3 crystals were fabricated on hydrophobic TiO2 nanotemplates composed of nanowells or grating patterns. Patterned areas as large as 100 μm × 100 μm were achieved. We examined and characterized the substrates using atomic force microscopy, scanning electron microscopy, x-ray diffraction, and energy dispersive spectroscopy. We present the optical properties (i.e. fluorescence and transmission) of soft nanoimprinted nanowells decorated with perovskites demonstrating the successful synthesis of MAPbI3 perovskite nanocrystals. As an example of their use, we demonstrate a two terminal device and show photocurrent response of a perovskite patterned micro-grating. Our method is a nondestructive approach to nanopatterning perovskites, and produces patterned arrays that maintain their photo-electric properties. The results presented herein suggests an attractive route to developing nanopatterned and small area perovskite substrates for applications in photovoltaics, x-ray sensing/detection, image sensor arrays, and others.

[INVITED] Tilted fiber grating mechanical and biochemical sensors

NASA Astrophysics Data System (ADS)

Guo, Tuan; Liu, Fu; Guan, Bai-Ou; Albert, Jacques

2016-04-01

The tilted fiber Bragg grating (TFBG) is a new kind of fiber-optic sensor that possesses all the advantages of well-established Bragg grating technology in addition to being able to excite cladding modes resonantly. This device opens up a multitude of opportunities for single-point sensing in hard-to-reach spaces with very controllable cross-sensitivities, absolute and relative measurements of various parameters, and an extreme sensitivity to materials external to the fiber without requiring the fiber to be etched or tapered. Over the past five years, our research group has been developing multimodal fiber-optic sensors based on TFBG in various shapes and forms, always keeping the device itself simple to fabricate and compatible with low-cost manufacturing. This paper presents a brief review of the principle, fabrication, characterization, and implementation of TFBGs, followed by our progress in TFBG sensors for mechanical and biochemical applications, including one-dimensional TFBG vibroscopes, accelerometers and micro-displacement sensors; two-dimensional TFBG vector vibroscopes and vector rotation sensors; reflective TFBG refractometers with in-fiber and fiber-to-fiber configurations; polarimetric and plasmonic TFBG biochemical sensors for in-situ detection of cell, protein and glucose.

Single resonance monolithic Fabry-Perot filters formed by volume Bragg gratings and multilayer dielectric mirrors

NASA Astrophysics Data System (ADS)

Lumeau, Julien; Koc, Cihan; Mokhun, Oleksiy; Smirnov, Vadim; Lequime, Michel; Glebov, Leonid B.

2012-02-01

High efficiency reflecting volume Bragg gratings (VBGs) recorded in PTR glass plates have shown un-preceded performances that make them very good candidates for narrowband spectral filtering with sub-nanometer spectral widths. However, decreasing the bandwidth to value below 30-50 pm is very challenging as it requires increasing the thickness of the RBG to more than 15-20 mm. To overcome this limitation, we propose a new approach which is a monolithic Fabry-Perot cavity which consists from a reflecting VBG with a multilayer dielectric mirror (MDM) deposited on its surface. A VBG with a grating vector perpendicular to its surface and a MDM produce a Fabry-Perot resonator with a single transmission band inside of the reflection spectrum of the VBG. We present a theoretical description of this new class of filters that allow achieving a single ultra-narrowband resonance associated with several hundred nanometers rejection band. Then we show the methods for designing and fabricating such filter. Finally, we present the steps that we followed in order to fabricate a first prototype for 852 nm and 1062 nm region that demonstrates a 30 pm bandwidth, 90+% transmission at resonance and a good agreement with theoretical simulation.

Integration of hybrid silicon lasers and electroabsorption modulators.

PubMed

Sysak, Matthew N; Anthes, Joel O; Bowers, John E; Raday, Omri; Jones, Richard

2008-08-18

We present an integration platform based on quantum well intermixing for multi-section hybrid silicon lasers and electroabsorption modulators. As a demonstration of the technology, we have fabricated discrete sampled grating DBR lasers and sampled grating DBR lasers integrated with InGaAsP/InP electroabsorption modulators. The integrated sampled grating DBR laser-modulators use the as-grown III-V bandgap for optical gain, a 50 nm blue shifted bandgap for the electrabosprtion modulators, and an 80 nm blue shifted bandgap for low loss mirrors. Laser continuous wave operation up to 45 ?C is achieved with output power >1.0 mW and threshold current of <50 mA. The modulator bandwidth is >2GHz with 5 dB DC extinction.

TiO2 surface functionalization of COC based planar waveguide Bragg gratings for refractive index sensing

NASA Astrophysics Data System (ADS)

Rosenberger, M.; Girschikofsky, M.; Förthner, M.; Belle, S.; Rommel, M.; Frey, L.; Schmauss, B.; Hellmann, R.

2018-01-01

We demonstrate the applicability of a planar waveguide Bragg grating in cyclo-olefin copolymer (COC) for refractive index sensing. The polymer planar waveguide Bragg grating fabricated using a single writing step technique is coated with a high-index layer of titanium dioxide (TiO2) leading to a distinct birefringence. This in turn results in the splitting of the Bragg reflection into two distinct Bragg wavelengths, which strongly differ regarding their refractive index sensitivities. Where one wavelength is only slightly affected by the ambient refractive index, the second Bragg peak shows a strong sensitivity. Furthermore, we investigate the temperature behaviour of the functionalized sensor and discuss it with respect to applications in refractive index sensing.

Preparation for B4C/Mo2C multilayer deposition of alternate multilayer gratings with high efficiency in the 0.5-2.5 keV energy range

NASA Astrophysics Data System (ADS)

Choueikani, Fadi; Delmotte, Franck; Bridou, Françoise; Lagarde, Bruno; Mercere, Pascal; Otero, Edwige; Ohresser, Philippe; Polack, François

2013-03-01

This paper presents a study of B4C/Mo2C multilayers mirrors with the aim of using it in the achievement of Alternate MultiLayer (AML) grating. Such component allows a high efficiency in the 500-2500 eV energy range for the DEIMOS beamline. Multilayers were deposited on silicon substrate. They are characterized by reflectometry under grazing incidence. Numerical adjustments were performed with a model of two layers in the period without any interfacial. A prototype of AML grating was fabricated and characterized. The efficiency of the first order of diffraction was worth 15% at 1700 eV.

Thin film solar cell design based on photonic crystal and diffractive grating structures.

PubMed

Mutitu, James G; Shi, Shouyuan; Chen, Caihua; Creazzo, Timothy; Barnett, Allen; Honsberg, Christiana; Prather, Dennis W

2008-09-15

In this paper we present novel light trapping designs applied to multiple junction thin film solar cells. The new designs incorporate one dimensional photonic crystals as band pass filters that reflect short light wavelengths (400 - 867 nm) and transmit longer wavelengths(867 -1800 nm) at the interface between two adjacent cells. In addition, nano structured diffractive gratings that cut into the photonic crystal layers are incorporated to redirect incoming waves and hence increase the optical path length of light within the solar cells. Two designs based on the nano structured gratings that have been realized using the scattering matrix and particle swarm optimization methods are presented. We also show preliminary fabrication results of the proposed devices.

Simultaneous measurement of absolute strain and differential strain based on fiber Bragg grating Fabry-Perot sensor

NASA Astrophysics Data System (ADS)

Wang, Kuiru; Wang, Bo; Yan, Binbin; Sang, Xinzhu; Yuan, Jinhui; Peng, Gang-Ding

2013-10-01

We present a fiber Bragg grating Fabry-Perot (FBG-FP) sensor using the fast Fourier transform (FFT) demodulation for measuring the absolute strain and differential strain simultaneously. The amplitude and phase characteristics of Fourier transform spectrum have been studied. The relation between the amplitude of Fourier spectrum and the differential strain has been presented. We fabricate the fiber grating FP cavity sensor, and carry out the experiment on the measurement of absolute strain and differential strain. Experimental results verify the demodulation method, and show that this sensor has a good accuracy in the scope of measurement. The demodulating method can expand the number of multiplexed sensors combining with wavelength division multiplexing and time division multiplexing.

GaInAsP/InP lateral-current-injection distributed feedback laser with a-Si surface grating.

PubMed

Shindo, Takahiko; Okumura, Tadashi; Ito, Hitomi; Koguchi, Takayuki; Takahashi, Daisuke; Atsumi, Yuki; Kang, Joonhyun; Osabe, Ryo; Amemiya, Tomohiro; Nishiyama, Nobuhiko; Arai, Shigehisa

2011-01-31

We fabricated a novel lateral-current-injection-type distributed feedback (DFB) laser with amorphous-Si (a-Si) surface grating as a step to realize membrane lasers. This laser consists of a thin GaInAsP core layer grown on a semi-insulating InP substrate and a 30-nm-thick a-Si surface layer for DFB grating. Under a room-temperature continuous-wave condition, a low threshold current of 7.0 mA and high efficiency of 43% from the front facet were obtained for a 2.0-μm stripe width and 300-μm cavity length. A small-signal modulation bandwidth of 4.8 GHz was obtained at a bias current of 30 mA.

Incorporation of wavelength selective devices into waveguides with applications to a miniature spectrometer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stallard, B. R.; Kaushik, S.; Hadley, G. R.

1996-02-01

This report pertains to a Laboratory Directed Research and Development project which was funded for FY94 and FY95. The goal was to develop building blocks for small, cheap sensors that use optical spectroscopy as a means of detecting chemical analytes. Such sensors can have an impact on a wide variety of technologies, such as: industrial process control, environmental monitors, chemical analysis in medicine, and automotive monitors. We describe work in fabricating and demonstrating a waveguide/grating device that can serve as the wavelength dispersive component in a miniature spectrometer. Also, we describe the invention and modeling of a new way tomore » construct an array of optical interference filters using sub-wavelength lithography to tune the index of refraction of a fixed Fabry-Perot cavity. Next we describe progress in more efficiently calculating the fields in grating devices. Finally we present the invention of a new type of near field optical probe, applicable to scanning microscopy or optical data storage, which is based on a circular grating constructed in a waveguide. This result diverges from the original goal of the project but is quite significant in that it promises to increase the data storage capacity of CD-ROMs by 10 times.« less

Recent progress in design and hybridization of planar grating-based transceivers

NASA Astrophysics Data System (ADS)

Bidnyk, S.; Pearson, M.; Balakrishnan, A.; Gao, M.

2007-06-01

We report on recent progress in simulations, physical layout, fabrication and hybridization of planar grating-based transceivers for passive optical networks (PONs). Until recently, PON transceivers have been manufactured using bulk micro-optical components. Today, advancements in modeling and simulation techniques has made it possible to design complex elements in the same silica-on silicon PLC platform and create an alternative platform for manufacturing of bi-directional transceivers. In our chips we simulated an integrated chip that monolithically combined planar reflective gratings and cascaded Mach-Zehnder interferometers. We used a combination of the finite element method and beam propagation method to model cascaded interferometers with enhanced coupling coefficients. Our simulations show that low-diffraction order planar reflective gratings, designed for small incidence and reflection angles, possess the required dispersion strength to meet the PON specifications. Subsequently, we created structures for passive alignment and hybridized photodetectors and lasers. We believe that advancements in simulation of planar lightwave circuits with embedded planar reflective gratings will result in displacement of the thin-film filters (TFFs) technology in many applications that require a high degree of monolithic and hybrid integration.

Investigation of Grating-Assisted Trimodal Interferometer Biosensors Based on a Polymer Platform.

PubMed

Liang, Yuxin; Zhao, Mingshan; Wu, Zhenlin; Morthier, Geert

2018-05-10

A grating-assisted trimodal interferometer biosensor is proposed and numerically analyzed. A long period grating coupler, for adjusting the power between the fundamental mode and the second higher order mode, is investigated, and is shown to act as a conventional directional coupler for adjusting the power between the two arms. The trimodal interferometer can achieve maximal fringe visibility when the powers of the two modes are adjusted to the same value by the grating coupler, which means that a better limit of detection can be expected. In addition, the second higher order mode typically has a larger evanescent tail than the first higher order mode in bimodal interferometers, resulting in a higher sensitivity of the trimodal interferometer. The influence of fabrication tolerances on the performance of the designed interferometer is also investigated. The power difference between the two modes shows inertia to the fill factor of the grating, but high sensitivity to the modulation depth. Finally, a 2050 2π/RIU (refractive index unit) sensitivity and 43 dB extinction ratio of the output power are achieved.

Enhanced light extraction from a GaN-based green light-emitting diode with hemicylindrical linear grating structure.

PubMed

Jin, Yuanhao; Yang, Fenglei; Li, Qunqing; Zhu, Zhendong; Zhu, Jun; Fan, Shoushan

2012-07-02

Significant enhancement in the light output from GaN-based green light-emitting diodes (LEDs) was achieved with a hemicylindrical grating structure on the top layer of the diodes. The grating structure was first optimized by the finite-difference time-domain (FDTD) method, which showed that the profile of the grating structure was critical for light extraction efficiency. It was found that the transmission efficiency of the 530 nm light emitted from the inside of the GaN LED increased for incidence angles between 23.58° and 60°. Such a structure was fabricated by electron-beam lithography and an etching method. The light output power from the LED was increased approximately 4.7 times compared with that from a conventional LED. The structure optimization is the key to the great increase in transmission efficiency. Furthermore, the light emitted from the edge of the LED units could be collected and extracted by the grating structures in adjacent LED units, thus enhancing the performance of the whole LED chip.

Composites

NASA Astrophysics Data System (ADS)

Taylor, John G.

The Composites market is arguably the most challenging and profitable market for phenolic resins aside from electronics. The variety of products and processes encountered creates the challenges, and the demand for high performance in critical operations brings value. Phenolic composite materials are rendered into a wide range of components to supply a diverse and fragmented commercial base that includes customers in aerospace (Space Shuttle), aircraft (interiors and brakes), mass transit (interiors), defense (blast protection), marine, mine ducting, off-shore (ducts and grating) and infrastructure (architectural) to name a few. For example, phenolic resin is a critical adhesive in the manufacture of honeycomb sandwich panels. Various solvent and water based resins are described along with resin characteristics and the role of metal ions for enhanced thermal stability of the resin used to coat the honeycomb. Featured new developments include pultrusion of phenolic grating, success in RTM/VARTM fabricated parts, new ballistic developments for military vehicles and high char yield carbon-carbon composites along with many others. Additionally, global regional market resin volumes and sales are presented and compared with other thermosetting resin systems.

Fiber Bragg grating sensors in harsh environments: considerations and industrial monitoring applications

NASA Astrophysics Data System (ADS)

Méndez, Alexis

2017-06-01

Over the last few years, fiber optic sensors (FOS) have seen an increased acceptance and widespread use in industrial sensing and in structural monitoring in civil, aerospace, marine, oil & gas, composites and other applications. One of the most prevalent types in use today are fiber Bragg grating (FBG) sensors. Historically, FOS have been an attractive solution because of their EM immunity and suitability for use in harsh environments and rugged applications with extreme temperatures, radiation exposure, EM fields, high voltages, water contact, flammable atmospheres, or other hazards. FBG sensors have demonstrated that can operate reliably in many different harsh environment applications but proper type and fabrication process are needed, along with suitable packaging and installation procedure. In this paper, we review the impact that external factors and environmental conditions play on FBG's performance and reliability, and describe the appropriate sensor types and protection requirements suitable for a variety of harsh environment applications in industrial furnaces, cryogenic coolers, nuclear plants, maritime vessels, oil & gas wells, aerospace crafts, automobiles, and others.

Light refocusing with up-scalable resonant waveguide gratings in confocal prolate spheroid arrangements

NASA Astrophysics Data System (ADS)

Quaranta, Giorgio; Basset, Guillaume; Benes, Zdenek; Martin, Olivier J. F.; Gallinet, Benjamin

2018-01-01

Resonant waveguide gratings (RWGs) are thin-film structures, where coupled modes interfere with the diffracted incoming wave and produce strong angular and spectral filtering. The combination of two finite-length and impedance matched RWGs allows the creation of a passive beam steering element, which is compatible with up-scalable fabrication processes. Here, we propose a design method to create large patterns of such elements able to filter, steer, and focus the light from one point source to another. The method is based on ellipsoidal mirrors to choose a system of confocal prolate spheroids where the two focal points are the source point and observation point, respectively. It allows finding the proper orientation and position of each RWG element of the pattern, such that the phase is constructively preserved at the observation point. The design techniques presented here could be implemented in a variety of systems, where large-scale patterns are needed, such as optical security, multifocal or monochromatic lenses, biosensors, and see-through optical combiners for near-eye displays.

Force sensing micro-forceps with integrated fiber Bragg grating for vitreoretinal surgery

NASA Astrophysics Data System (ADS)

He, Xingchi; Balicki, Marcin A.; Kang, Jin U.; Gehlbach, Peter L.; Handa, James T.; Taylor, Russell H.; Iordachita, Iulian I.

2012-01-01

Vitreoretinal surgery is a technically demanding ophthalmologic discipline. One of the main technical challenges in vitreoretinal surgery is the lack of force sensing since the surgical maneuvers fall below the human sensory threshold. Previously, a 2-degree-of-freedom (DOF) force sensing instrument with a surgical pick was developed and tested. However, a more commonly used instrument for vitreoretinal surgery is the forceps, with which a surgeon can easily grasp and delaminate the scar tissue. We have designed, fabricated and calibrated a novel 20-gauge (Ga) microsurgical instrument with a 2-DOF force sensing forceps. Three fiber Bragg grating (FBG) sensors are integrated into the customized AlconTM forceps tip. The redundant sensor configuration provides good compensation for temperature-related drift. The calibration data show that the tool can provide a force resolution of 0.25 mN. In order to test the functionality and performance, the forceps was evaluated in inner shell membrane peeling experiments with chicken embryos as well as in in-vivo rabbit experiments. The instrument has demonstrated the capability of being applied in the clinical environment, with consistent force measurements. The force exerted in inner shell membrane peeling is from 6.07 to 34.65 mN. The development of the 2-DOF force sensing micro-forceps has shown that the fabrication process is feasible and reliable, and it can be used to develop a future 3-DOF force sensing tool.

Near perfect light trapping in 2D metal nanotrench gratings and its application for sensing (Conference Presentation)

NASA Astrophysics Data System (ADS)

Guo, Junpeng; Guo, Hong; Li, Zhitong

2016-09-01

In this work, a 2D metallic nano-trench array was fabricated on gold metal surface by using an e-beam lithography patterning and etching process. Optical reflectance from the device was measured at oblique angles of incidence for TE and TM polarization. Near perfect light trapping was observed at different wavelengths for TE and TM polarization at oblique angle of incidence. As angle of incidence increases, light trapping wavelength has a red-shift for TM polarization and blue shift for TE polarization. The fabricated nano-trench device was also investigated for chemical sensor application. It was found that by varying the angle of incidence, the sensitivity changes with opposite trends for TE and TM polarization. Sensor sensitivity increases for TM polarization and decreases for TE polarization with increase of the oblique incident angle.

Continuously tunable solution-processed organic semiconductor DFB lasers pumped by laser diode.

PubMed

Klinkhammer, Sönke; Liu, Xin; Huska, Klaus; Shen, Yuxin; Vanderheiden, Sylvia; Valouch, Sebastian; Vannahme, Christoph; Bräse, Stefan; Mappes, Timo; Lemmer, Uli

2012-03-12

The fabrication and characterization of continuously tunable, solution-processed distributed feedback (DFB) lasers in the visible regime is reported. Continuous thin film thickness gradients were achieved by means of horizontal dipping of several conjugated polymer and blended small molecule solutions on cm-scale surface gratings of different periods. We report optically pumped continuously tunable laser emission of 13 nm in the blue, 16 nm in the green and 19 nm in the red spectral region on a single chip respectively. Tuning behavior can be described with the Bragg-equation and the measured thickness profile. The laser threshold is low enough that inexpensive laser diodes can be used as pump sources.

One-dimensional photonic crystals for code-division multiple access

NASA Astrophysics Data System (ADS)

Wang, Shamino Yuanliang

One-dimensional photonic crystals exhibit reduced group velocity and huge dispersion at their rejection band edge frequencies. Therefore they are natural candidates as optical delay lines, dispersion compensators, and pulse reshapers. Using wavelength tunable pulses spectrally sliced from a mode-locked fiber laser, the transmission mode measurement was performed in the time domain with single picosecond resolution. Group delays and dispersion were measured with an autocorrelator as an ultrafast optical detector and cross-correlator. Our experimental results agree qualitatively with the theoretical and simulation predictions. A maximum group delay of 10 ps for a commercial 3 mm long uniform fiber Bragg grating and that of 22.6 ps for a research laboratory fabricated 1 cm grating were measured, corresponding to a group velocity 66% of the speed of light in bare fiber. We have also demonstrated in the overlap transmission region of a grating pair both gratings contribute to the group delay while the group velocity dispersion was canceled, resulting in additive delay in transmission with minimal pulse reshaping. This compound grating configuration was further expanded as specially designed grating sequence encoders and decoders in matched filter CDMA. The transmitter grating sequence temporally stretched the input pulse into a long time scale low peak intensity pseudorandom noise, while the conjugate grating sequence in the receiver performed pulse reconstruction and data recovery. A temporal FWHM contrast ratio of 2.5 and a peak intensity contrast ratio of 10 between the correctly and incorrectly decoded signals were achieved. Armed with more sophisticated grating designs we believe this would be a powerful solution to CDMA orthogonal code requirements.

Fiber Bragg grating fabrication for the implementation of sensors in the electronics and optoelectronics laboratory at BUAP

NASA Astrophysics Data System (ADS)

Bracamontes Rodríguez, Y. E.; Beltrán Pérez, G.; Castillo Mixcóatl, J.; Muñoz Aguirre, S.

2011-09-01

Fiber Bragg gratings (FBG) are important optical devices since they have been quite successful not only in the field of communications but also in sensor systems and optical fiber lasers. In the sensors area they are generally used as detection elements for different physical parameters such as temperature, strain, flow, etc. In the electronics and optoelectronics laboratory at Benemérita Universidad Autónoma de Puebla (LEyO-BUAP), there are already experimental setups of sensors as well as laser systems, where FBGs are fundamental elements for their adequate performance. However, these FBGs are commercial devices and they present limited characteristics in their transmission profiles, bandwidth and reflectivity. On the other hand, in some occasions, the delivery time from the fabricant to the customer is quite long. Therefore, it is important for LEyO to implement a system to fabricate this kind of devices, which would mean LEyO independence in the technological development. In this work, results of FBGs fabrication based on the phase mask technique are presented. Such mask is optimized for UV and it has a period of 1060 nm. A Nd:YAG pulsed laser with a 5 ns pulse length and an energy of 40 mJ was used as the UV source employing the 4th harmonic generation to obtain a 266 nm wavelength. Ge-doped fiber was used to fabricate the devices.

Passive and active sol-gel materials and devices

NASA Astrophysics Data System (ADS)

Andrews, Mark P.; Najafi, S. Iraj

1997-07-01

This paper examines sol-gel materials for photonics in terms of partnerships with other material contenders for processing optical devices. The discussion in four sections identifies semiconductors, amorphous and crystalline inorganic dielectrics, and amorphous and crystalline organic dielectrics as strategic agents in the rapidly evolving area of materials and devices for data communications and telecommunications. With Zyss, we trace the hierarchical lineage that connects molecular hybridization (chemical functionality), through supramolecular hybridization (collective properties and responses), to functional hybridization (device and system level constructs). These three concepts thread their way through discussions of the roles sol-gel glasses might be anticipated to assume in a photonics marketplace. We assign a special place to glass integrated optics and show how high temperature consolidated sol-gel derived glasses fit into competitive glass fabrication technologies. Low temperature hybrid sol-gel glasses that combine attractive features of organic polymers and inorganic glasses are considered by drawing on examples of our own new processes for fabricating couplers, power splitters, waveguides and gratings by combining chemical synthesis and sol-gel processing with simple photomask techniques.

Long-period fiber phase grating devices

NASA Astrophysics Data System (ADS)

Stegall, David Brian

In recent years, the explosive growth of the internet has virtually surpassed the limits of the global communications infrastructure. As a result, the fiber- optic communications industry is spearheading research and development to transmit information at ever increasing rates and over longer distances. The industry faces several obstacles to improving the performance of these systems. One problem is dispersion, which manifests at faster transmission rates when pulse spreading and distortion scramble the signal. Furthermore, high transmission powers needed for longer distances introduce deleterious optical nonlinearity phenomenon. Several waveguide and bulk devices have been implemented to address these issues, but each have shortcomings. Many of these problems and challenges have also impacted other fiber-optic industries, such as sensor systems. Long- period optical fiber gratings pose simple solutions to these problems and offer novel applications previously impractical through any other means. In this dissertation, research is presented in which modeling and fabrication of long-period gratings is improved over existing techniques by incorporating the effects of waveguide dispersion. An arbitrary dispersion also can be introduced into a long-period grating intentionally and a theoretical examination is made relating the chirp of a long-period grating and the resulting dispersion. In addition, several device applications such as a biological sensor and the concept of an actively controlled transmission spectrum of a long-period grating are explored. Finally, multiple in-series Bragg and long- period gratings are investigated for novel device configurations.

New ways in creating pixelgram images

NASA Astrophysics Data System (ADS)

Malureanu, Radu; Di Fabrizio, Enzo

2006-09-01

Since the diffraction gratings were invented, their use in various security systems has been exploited. Their big advantage is the low production cost and, in the same time, the difficulty of replicating them. Most of the nowadays security systems are using those gratings to prove their originality. They can be seen on all the CDs, DVDs, most of the major credit cards and even on the wine bottles. In this article we present a new way of making such gratings without changing the production steps but generating an even more difficult to be replicated item. This new way consists not only in changing the grating period so that various false colours can be seen, but also their orientation so that for a complete check of the grating it should be seen under a certain solid angle. In the same time, one can also keep the possibility to change the grating period so this way various colours can be seen for each angle variation. By combining these two techniques (changing period and changing the angle ones) one can indeed create different images for each view angle and thus increasing the security of the object. In the same time, as can be seen, from the fabrication point of view no further complications appear. The production steps are identical, the only difference being the pattern. The resolution of the grating is not increased necessarily so neither from this point of view will complications appear.

All-fiber optical filter with an ultranarrow and rectangular spectral response.

PubMed

Zou, Xihua; Li, Ming; Pan, Wei; Yan, Lianshan; Azaña, José; Yao, Jianping

2013-08-15

Optical filters with an ultranarrow and rectangular spectral response are highly desired for high-resolution optical/electrical signal processing. An all-fiber optical filter based on a fiber Bragg grating with a large number of phase shifts is designed and fabricated. The measured spectral response shows a 3 dB bandwidth of 650 MHz and a rectangular shape factor of 0.513 at the 25 dB bandwidth. This is the narrowest rectangular bandpass response ever reported for an all-fiber filter, to the best of our knowledge. The filter has also the intrinsic advantages of an all-fiber implementation.

Si-based optical I/O for optical memory interface

NASA Astrophysics Data System (ADS)

Ha, Kyoungho; Shin, Dongjae; Byun, Hyunil; Cho, Kwansik; Na, Kyoungwon; Ji, Hochul; Pyo, Junghyung; Hong, Seokyong; Lee, Kwanghyun; Lee, Beomseok; Shin, Yong-hwack; Kim, Junghye; Kim, Seong-gu; Joe, Insung; Suh, Sungdong; Choi, Sanghoon; Han, Sangdeok; Park, Yoondong; Choi, Hanmei; Kuh, Bongjin; Kim, Kichul; Choi, Jinwoo; Park, Sujin; Kim, Hyeunsu; Kim, Kiho; Choi, Jinyong; Lee, Hyunjoo; Yang, Sujin; Park, Sungho; Lee, Minwoo; Cho, Minchang; Kim, Saebyeol; Jeong, Taejin; Hyun, Seokhun; Cho, Cheongryong; Kim, Jeong-kyoum; Yoon, Hong-gu; Nam, Jeongsik; Kwon, Hyukjoon; Lee, Hocheol; Choi, Junghwan; Jang, Sungjin; Choi, Joosun; Chung, Chilhee

2012-01-01

Optical interconnects may provide solutions to the capacity-bandwidth trade-off of recent memory interface systems. For cost-effective optical memory interfaces, Samsung Electronics has been developing silicon photonics platforms on memory-compatible bulk-Si 300-mm wafers. The waveguide of 0.6 dB/mm propagation loss, vertical grating coupler of 2.7 dB coupling loss, modulator of 10 Gbps speed, and Ge/Si photodiode of 12.5 Gbps bandwidth have been achieved on the bulk-Si platform. 2x6.4 Gbps electrical driver circuits have been also fabricated using a CMOS process.

Study of the injection molding of a polarizing beam splitter.

PubMed

Jose de Carvalho, Edson; Braga, Edmundo da Silva; Cescato, Lucila H

2006-01-01

We describe the replication of a relief grating that behaves like a polarizing beam splitter by injection molding. Measurements of the grating master, nickel shim, and replica, performed by atomic force microscopy, allow establishing a limit for the injection molding technique (currently used in CD fabrication) to aspect ratios of approximately 0.15. Although this limit strongly reduces the diffraction efficiency of the elements as well as their polarizing properties, extinction ratios of approximately 10:1 were measured for the replicas in a large range of wavelengths.

Hidden Gratings in Holographic Liquid Crystal Polymer-Dispersed Liquid Crystal Films.

PubMed

De Sio, Luciano; Lloyd, Pamela F; Tabiryan, Nelson V; Bunning, Timothy J

2018-04-18

Dynamic diffraction gratings that are hidden in the field-off state are fabricated utilizing a room-temperature photocurable liquid crystal (LC) monomer and nematic LC (NLC) using holographic photopolymerization techniques. These holographic LC polymer-dispersed LCs (HLCPDLCs) are hidden because of the refractive index matching between the LC polymer and the NLC regions in the as-formed state (no E-field applied). Application of a moderate E-field (5 V/μm) generates a refractive index mismatch because of the NLC reorientation (along the E-field) generating high-diffraction efficiency transmission gratings. These dynamic gratings are characterized by morphological, optical, and electrooptical techniques. They exhibit a morphology made of oriented LC polymer regions (containing residual NLC) alternating with a two-phase region of an NLC and LC polymer. Unlike classic holographic polymer-dispersed LC gratings formed with a nonmesogenic monomer, there is index matching between the as-formed alternating regions of the grating. These HLCPDLCs exhibit broad band and high diffraction efficiency (≈90%) at the Bragg angle, are transparent to white light across the visible range because of the refractive index matching, and exhibit fast response times (1 ms). The ability of HLCPDLCs not to consume electrical power in the off state opens new possibilities for the realization of energy-efficient switchable photonic devices.

Distributed feedback lasers

NASA Technical Reports Server (NTRS)

Ladany, I.; Andrews, J. T.; Evans, G. A.

1988-01-01

A ridge waveguide distributed feedback laser was developed in InGaAsP. These devices have demonstrated CW output powers over 7 mW with threshold currents as low as 60 mA at 25 C. Measurements of the frequency response of these devices show a 3 dB bandwidth of about 2 GHz, which may be limited by the mount. The best devices have a single mode spectra over the entire temperature range tested with a side mode suppression of about 20 dB in both CW and pulsed modes. The design of this device, including detailed modeling of the ridge guide structure, effective index calculations, and a discussion of the grating configuration are presented. Also, the fabrication of the devices is presented in some detail, especially the fabrication of and subsequent growth over the grating. In addition, a high frequency fiber pigtailed package was designed and tested, which is a suitable prototype for a commercial package.

Study of gain-coupled distributed feedback laser based on high order surface gain-coupled gratings

NASA Astrophysics Data System (ADS)

Gao, Feng; Qin, Li; Chen, Yongyi; Jia, Peng; Chen, Chao; Cheng, LiWen; Chen, Hong; Liang, Lei; Zeng, Yugang; Zhang, Xing; Wu, Hao; Ning, Yongqiang; Wang, Lijun

2018-03-01

Single-longitudinal-mode, gain-coupled distributed feedback (DFB) lasers based on high order surface gain-coupled gratings are achieved. Periodic surface metal p-contacts with insulated grooves realize gain-coupled mechanism. To enhance gain contrast in the quantum wells without the introduction of effective index-coupled effect, groove length and depth were well designed. Our devices provided a single longitudinal mode with the maximum CW output power up to 48.8 mW/facet at 971.31 nm at 250 mA without facet coating, 3dB linewidth (<3.2 pm) and SMSR (>39 dB). Optical bistable characteristic was observed with a threshold current difference. Experimentally, devices with different cavity lengths were contrasted on power-current and spectrum characteristics. Due to easy fabrication technique and stable performance, it provides a method of fabricating practical gain-coupled distributed feedback lasers for commercial applications.

Metallic-packaging fiber Bragg grating sensor based on ultrasonic welding for strain-insensitive temperature measurement

NASA Astrophysics Data System (ADS)

Zhu, Lianqing; Yang, Runtao; Zhang, Yumin; Dong, Mingli; Lou, Xiaoping

2018-04-01

In this paper, a metallic-packaging fiber Bragg grating temperature sensor characterized by a strain insensitive design is demonstrated. The sensor is fabricated by the one-step ultrasonic welding technique using type-II fiber Bragg grating combined with an aluminum alloy substrate. Finite element analysis is used to perform theoretical evaluation. The result of the experiment illustrates that the metallic-packaging temperature sensor is insensitive to longitudinal strain. The sensor's temperature sensitivity is 36 pm/°C over the range of 50-110 °C, with the correlation coefficient (R2) being 0.999. The sensor's temporal response is 40 s at a sudden temperature change from 21 °C to 100 °C. The proposed sensor can be applied on reliable and precise temperature measurement.

Slow-light, band-edge waveguides for tunable time delays.

PubMed

Povinelli, M; Johnson, Steven; Joannopoulos, J

2005-09-05

We propose the use of slow-light, band-edge waveguides for compact, integrated, tunable optical time delays. We show that slow group velocities at the photonic band edge give rise to large changes in time delay for small changes in refractive index, thereby shrinking device size. Figures of merit are introduced to quantify the sensitivity, as well as the accompanying signal degradation due to dispersion. It is shown that exact calculations of the figures of merit for a realistic, three-dimensional grating structure are well predicted by a simple quadratic-band model, simplifying device design. We present adiabatic taper designs that attain <0.1% reflection in short lengths of 10 to 20 times the grating period. We show further that cascading two gratings compensates for signal dispersion and gives rise to a constant tunable time delay across bandwidths greater than 100GHz. Given typical loss values for silicon-on-insulator waveguides, we estimate that gratings can be designed to exhibit tunable delays in the picosecond range using current fabrication technology.

Fabrication High Resolution Metrology Target By Step And Repeat Method

NASA Astrophysics Data System (ADS)

Dusa, Mircea

1983-10-01

Based on the photolithography process generally used to generate high resolution masks for semiconductor I.C.S, we found a very useful industrial application of laser technology.First, we have generated high resolution metrology targets which are used in industrial measurement laser interferometers as difra.ction gratings. Secondi we have generated these targets using step and repeat machine, with He-Ne laser interferometer controlled state, as a pattern generator, due to suitable computer programming.Actually, high resolution metrology target, means two chromium plates, one of which is called the" rule" the other one the "vernier". In Fig.1 we have the configuration of the rule and the vernier. The rule has a succesion of 3 μM lines generated as a difraction grating on a 4 x 4 inch chromium blank. The vernier has several exposed fields( areas) having 3 - 15 μm lines, fields placed on very precise position on the chromium blank surface. High degree of uniformity, tight CD tolerances, low defect density required by the targets, creates specialised problems during processing. Details of the processing, together with experimental results will be presented. Before we start to enter into process details, we have to point out that the dimensional requirements of the reticle target, are quite similar or perhaps more strict than LSI master casks. These requirements presented in Fig.2.

Simple, monolithic optical element for forward-viewing spectrally encoded endoscopy (Conference Presentation)

NASA Astrophysics Data System (ADS)

Do, Dukho; Kang, Dongkyun; Ikuta, Mitsuhiro; Tearney, Guillermo J.

2016-03-01

Spectrally encoded endoscopy (SEE) is a miniature endoscopic technology that can acquire images of internal organs through a hair-thin probe. While most previously described SEE probes have been side viewing, forward-view (FV)-SEE is advantageous in certain clinical applications as it provides more natural navigation of the probe and has the potential to provide a wider field of view. Prior implementations of FV-SEE used multiple optical elements that increase fabrication complexity and may diminish the robustness of the device. In this paper, we present a new design that uses a monolithic optical element to realize FV-SEE imaging. The optical element is specially designed spacer, fabricated from a 500-μm-glass rod that has a mirror surface on one side and a grating stamped on its distal end. The mirror surface is used to change the incident angle on the grating to diffract the shortest wavelength of the spectrum so that it is parallel to the optical axis. Rotating the SEE optics creates a circular FV-SEE image. Custom-designed software processes FV-SEE images into circular images, which are displayed in real-time. In order to demonstrate this new design, we have constructed the FV-SEE optical element using a 1379 lines/mm diffraction grating. When illuminated with a source with a spectral bandwidth of 420-820 nm, the FV-SEE optical element provides 678 resolvable points per line. The imaging performance of the FV-SEE device was tested by imaging a USAF resolution target. SEE images showed that this new approach generates high quality images in the forward field with a field of view of 58°. Results from this preliminary study demonstrate that we can realize FV-SEE imaging with simple, monolithic, miniature optical element. The characteristics of this FV-SEE configuration will facilitate the development of robust miniature endoscopes for a variety of medical imaging applications.

Signal intensity enhancement of laser ablated volume holograms

NASA Astrophysics Data System (ADS)

Versnel, J. M.; Williams, C.; Davidson, C. A. B.; Wilkinson, T. D.; Lowe, C. R.

2017-11-01

Conventional volume holographic gratings (VHGs) fabricated in photosensitive emulsions such as gelatin containing silver salts enable the facile visualization of the holographic image in ambient lighting. However, for the fabrication of holographic sensors, which require more defined and chemically-functionalised polymer matrices, laser ablation has been introduced to create the VHGs and thereby broaden their applications, although the replay signal can be challenging to detect in ambient lighting. When traditional photochemical bleaching solutions used to reduce light scattering and modulate refractive index within the VHG are applied to laser ablated volume holographic gratings, these procedures decrease the holographic peak intensity. This is postulated to occur because both light and dark fringes contain a proportion of metal particles, which upon solubilisation are converted immediately to silver iodide, yielding no net refractive index modulation. This research advances a hypothesis that the reduced intensity of holographic replay signals is linked to a gradient of different sized metal particles within the emulsion, which reduces the holographic signal and may explain why traditional bleaching processes result in a reduction in intensity. In this report, a novel experimental protocol is provided, along with simulations based on an effective medium periodic 1D stack, that offers a solution to increase peak signal intensity of holographic sensors by greater than 200%. Nitric acid is used to etch the silver nanoparticles within the polymer matrix and is thought to remove the smaller particles to generate more defined metal fringes containing a soluble metal salt. Once the grating efficiency has been increased, this salt can be converted to a silver halide, to modulate the refractive index and increase the intensity of the holographic signal. This new protocol has been tested in a range of polymer chemistries; those containing functional groups that help to stabilize the metal nanoparticles within the matrix yield more intense holographic signals as the integrity of the fringe is more protected with increasing metal solubility.

DUV phase mask for 100 nm period grating printing

NASA Astrophysics Data System (ADS)

Jourlin, Y.; Bourgin, Y.; Reynaud, S.; Parriaux, O.; Talneau, A.; Karvinen, P.; Passilly, N.; Zain, A. Md.; De La Rue, R. M.

2008-04-01

Whereas microelectronic lithography is heading to the 32 nm node and discussing immersion and double-patterning strategies, there is much which can be done with the 45 nm node in microoptics for white light processing. For instance, one of the most demanding applications in terms of achievable period is the LCD lossless polarizer, which can transmit the TM polarization and reflect the TE polarization evenly all through the visible spectrum - provided that a 1D metal grid of 100 nm period can be fabricated. The manufacture of such polarizing panels cannot resort to the step & repeat cameras of microelectronics since the substrates are too large, too thin, too wavy and full of contaminants. There is therefore a need for specific fabrication techniques. It is one of these techniques that a subgroup of partners belonging to two of the Networks of Excellence of the European Community, NEMO and ePIXnet, have decided to explore together.

[Reliability of three dimensional resin model by rapid prototyping manufacturing and digital modeling].

PubMed

Zeng, Fei-huang; Xu, Yuan-zhi; Fang, Li; Tang, Xiao-shan

2012-02-01

To describe a new technique for fabricating an 3D resin model by 3D reconstruction and rapid prototyping, and to analyze the precision of this method. An optical grating scanner was used to acquire the data of silastic cavity block , digital dental cast was reconstructed with the data through Geomagic Studio image processing software. The final 3D reconstruction was saved in the pattern of Stl. The 3D resin model was fabricated by fuse deposition modeling, and was compared with the digital model and gypsum model. The data of three groups were statistically analyzed using SPSS 16.0 software package. No significant difference was found in gypsum model,digital dental cast and 3D resin model (P>0.05). Rapid prototyping manufacturing and digital modeling would be helpful for dental information acquisition, treatment design, appliance manufacturing, and can improve the communications between patients and doctors.

Fiber-Optic Gratings for Lidar Measurements of Water Vapor

NASA Technical Reports Server (NTRS)

Vann, Leila B.; DeYoung, Russell J.

2006-01-01

Narrow-band filters in the form of phase-shifted Fabry-Perot Bragg gratings incorporated into optical fibers are being developed for differential-absorption lidar (DIAL) instruments used to measure concentrations of atmospheric water vapor. The basic idea is to measure the relative amounts of pulsed laser light scattered from the atmosphere at two nearly equal wavelengths, one of which coincides with an absorption spectral peak of water molecules and the other corresponding to no water vapor absorption. As part of the DIAL measurement process, the scattered light is made to pass through a filter on the way to a photodetector. Omitting other details of DIAL for the sake of brevity, what is required of the filter is to provide a stop band that: Surrounds the water-vapor spectral absorption peaks at a wavelength of 946 nm, Has a spectral width of at least a couple of nanometers, Contains a pass band preferably no wider than necessary to accommodate the 946.0003-nm-wavelength water vapor absorption peak [which has 8.47 pm full width at half maximum (FWHM)], and Contains another pass band at the slightly shorter wavelength of 945.9 nm, where there is scattering of light from aerosol particles but no absorption by water molecules. Whereas filters used heretofore in DIAL have had bandwidths of =300 pm, recent progress in the art of fiber-optic Bragg-grating filters has made it feasible to reduce bandwidths to less than or equal to 20 pm and thereby to reduce background noise. Another benefit of substituting fiber-optic Bragg-grating filters for those now in use would be significant reductions in the weights of DIAL instruments. Yet another advantage of fiber-optic Bragg-grating filters is that their transmission spectra can be shifted to longer wavelengths by heating or stretching: hence, it is envisioned that future DIAL instruments would contain devices for fine adjustment of transmission wavelengths through stretching or heating of fiber-optic Bragg-grating filters nominally designed and fabricated to have transmission wavelengths that, in the absence of stretching, would be slightly too short.

High sensitivity long-period grating-based temperature monitoring using a wide wavelength range to 2.2 μm

NASA Astrophysics Data System (ADS)

Venugopalan, Thillainathan; Yeo, Teck L.; Sun, Tong; Grattan, Kenneth T. V.

2006-12-01

Temperature effects on the various cladding modes of a long-period grating (LPG) fabricated in B-Ge co-doped fibre have been investigated to create a high sensitivity measurement device. The temperature sensitivities of the attenuation bands of the LPG over the wavelength region 1.2-2.2 μm, for a grating with a 330 μm period, were obtained by monitoring the wavelength shift of each attenuation band, with a temperature increment of 20 °C, over the range from 23 °C to 140 °C. The attenuation band appearing over the 1.8-2.0 μm wavelength range has shown a nearly five times higher temperature sensitivity than that of lower order modes, and thus it shows significant promise for fibre optic temperature sensor applications.

Fabrication and Calibration of FORTIS

NASA Technical Reports Server (NTRS)

Fleming, Brian T.; McCandliss, Stephan R.; Kaiser, Mary Elizabeth; Kruk, Jeffery; Feldman, Paul D.; Kutyrev, Alexander S.; Li, Mary J.; Rapchun, David A.; Lyness, Eric; Moseley, S. H.;

Fabrication and calibration of FORTIS

NASA Astrophysics Data System (ADS)

Fleming, Brian T.; McCandliss, Stephan R.; Kaiser, Mary Elizabeth; Kruk, Jeffery; Feldman, Paul D.; Kutyrev, Alexander S.; Li, Mary J.; Rapchun, David A.; Lyness, Eric; Moseley, S. H.; Siegmund, Oswald; Vallerga, John; Martin, Adrian

2011-09-01

The Johns Hopkins University sounding rocket group is entering the final fabrication phase of the Far-ultraviolet Off Rowland-circle Telescope for Imaging and Spectroscopy (FORTIS); a sounding rocket borne multi-object spectro-telescope designed to provide spectral coverage of 43 separate targets in the 900 - 1800 Angstrom bandpass over a 30' x 30' field-of- view. Using "on-the-fly" target acquisition and spectral multiplexing enabled by a GSFC microshutter array, FORTIS will be capable of observing the brightest regions in the far-UV of nearby low redshift (z ~ 0.002 - 0.02) star forming galaxies to search for Lyman alpha escape, and to measure the local gas-to-dust ratio. A large area (~ 45 mm x 170 mm) microchannel plate detector built by Sensor Sciences provides an imaging channel for targeting flanked by two redundant spectral outrigger channels. The grating is ruled directly onto the secondary mirror to increase efficiency. In this paper, we discuss the recent progress made in the development and fabrication of FORTIS, as well as the results of early calibration and characterization of our hardware, including mirror/grating measurements, detector performance, and early operational tests of the microshutter arrays.

Narrowband 1.5-{mu}m Bragg filter based on a polymer waveguide with a laser-written refractive-index grating

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sokolov, Viktor I; Panchenko, Vladislav Ya; Seminogov, V N

We report the fabrication of narrowband frequency-selective filters for the 1.5-{mu}m telecom window, which include a single-mode polymer waveguide with a submicron Bragg grating inscribed by a helium-cadmium laser. The filters have a reflectance R > 98 % and a nearly rectangular reflection band with a bandwidth {Delta}{lambda}{approx}0.4nm. They can be used as components of optical multiplexers/demultiplexers for combining and separating signals in high-speed dense wavelength-division multiplexed optical fibre communication systems. (laser components)

Optical Signal Processing: Poisson Image Restoration and Shearing Interferometry

NASA Technical Reports Server (NTRS)

Hong, Yie-Ming

1973-01-01

Optical signal processing can be performed in either digital or analog systems. Digital computers and coherent optical systems are discussed as they are used in optical signal processing. Topics include: image restoration; phase-object visualization; image contrast reversal; optical computation; image multiplexing; and fabrication of spatial filters. Digital optical data processing deals with restoration of images degraded by signal-dependent noise. When the input data of an image restoration system are the numbers of photoelectrons received from various areas of a photosensitive surface, the data are Poisson distributed with mean values proportional to the illuminance of the incoherently radiating object and background light. Optical signal processing using coherent optical systems is also discussed. Following a brief review of the pertinent details of Ronchi's diffraction grating interferometer, moire effect, carrier-frequency photography, and achromatic holography, two new shearing interferometers based on them are presented. Both interferometers can produce variable shear.

Fabrication of resonant patterns using thermal nano-imprint lithography for thin-film photovoltaic applications.

PubMed

Khaleque, Tanzina; Svavarsson, Halldor Gudfinnur; Magnusson, Robert

2013-07-01

A single-step, low-cost fabrication method to generate resonant nano-grating patterns on poly-methyl-methacrylate (PMMA; plexiglas) substrates using thermal nano-imprint lithography is reported. A guided-mode resonant structure is obtained by subsequent deposition of thin films of transparent conductive oxide and amorphous silicon on the imprinted area. Referenced to equivalent planar structures, around 25% and 45% integrated optical absorbance enhancement is observed over the 450-nm to 900-nm wavelength range in one- and two-dimensional patterned samples, respectively. The fabricated elements provided have 300-nm periods. Thermally imprinted thermoplastic substrates hold potential for low-cost fabrication of nano-patterned thin-film solar cells for efficient light management.

Simultaneous RGB lasing from a single-chip polymer device.

PubMed

Yamashita, Kenichi; Takeuchi, Nobutaka; Oe, Kunishige; Yanagi, Hisao

2010-07-15

This Letter describes the fabrication and operation of a single-chip white-laser device. The laser device has a multilayered structure consisting of three laser layers. Each laser layer comprises polymer claddings and a waveguide core doped with organic dye. In each laser layer, grating corrugations were fabricated by UV-nanoimprint lithography that act as distributed-feedback cavity structures. Under optical pumping, lasing output with red, green, and blue colors was simultaneously obtained from the sample edge.

Ultra-sensitive wide dynamic range temperature sensor based on in-fiber Lyot interferometer

NASA Astrophysics Data System (ADS)

Nikbakht, Hamed; Poorghdiri Isfahani, Mohamad Hosein; Latifi, Hamid

2017-04-01

An in-fiber Lyot interferometer for temperature measurement is presented. The sensor utilizes high temperature-dependence of the birefringence in Panda polarization maintaining fibers to achieve high resolution in temperature measurements. Temperature variation modulates the phase difference between the polarization modes propagating in different modes of the Panda fiber. The Lyot interferometer produces a spectrum which varies with the phase difference. Therefore, by monitoring this spectrum a high resolution of 0.003°C was achieved. A fiber Bragg grating is added to the setup to expand its dynamic range. This sensor does not need complicated fabrication process and can be implemented in many applications.

Research Studies on Advanced Optical Module/Head Designs for Optical Data Storage

NASA Technical Reports Server (NTRS)

1992-01-01

Preprints are presented from the recent 1992 Optical Data Storage meeting in San Jose. The papers are divided into the following topical areas: Magneto-optical media (Modeling/design and fabrication/characterization/testing); Optical heads (holographic optical elements); and Optical heads (integrated optics). Some representative titles are as follow: Diffraction analysis and evaluation of several focus and track error detection schemes for magneto-optical disk systems; Proposal for massively parallel data storage system; Transfer function characteristics of super resolving systems; Modeling and measurement of a micro-optic beam deflector; Oxidation processes in magneto-optic and related materials; and A modal analysis of lamellar diffraction gratings in conical mountings.

Graphene as discharge layer for electron beam lithography on insulating substrate

NASA Astrophysics Data System (ADS)

Liu, Junku; Li, Qunqing; Ren, Mengxin; Zhang, Lihui; Chen, Mo; Fan, Shoushan

2013-09-01

Charging of insulating substrates is a common problem during Electron Beam lithography (EBL), which deflects the beam and distorts the pattern. A homogeneous, electrically conductive, and transparent graphene layer is used as a discharge layer for EBL processes on insulating substrates. The EBL resolution is improved compared with the metal discharge layer. Dense arrays of holes with diameters of 50 nm and gratings with line/space of 50/30 nm are obtained on quartz substrate. The pattern placement errors and proximity effect are suppressed over a large area and high quality complex nanostructures are fabricated using graphene as a conductive layer.

Inorganic-organic nanocomposites for optical coatings

NASA Astrophysics Data System (ADS)

Schmidt, Helmut K.; Krug, Herbert; Sepeur-Zeitz, Bernhard; Geiter, Elisabeth

1997-10-01

The fabrication of nanoparticles by the sol-gel process and their use in polymeric or sol-gel-derived inorganic-organic composite matrices opens up interesting possibilities for designing new optical materials. Two different routes have been chosen for preparing optical nanocomposites: The first is the so-called 'in situ route,' where the nanoparticles are synthesized in a liquid mixture from Zr-alkoxides in a polymerizable system and diffractive gratings were produced by embossing uncured film. The second is the 'separate' preparation route, where a sterically stabilized dry nanoboehmite powder was completely redispersed in an epoxy group-containing matrix and hard coatings with optical quality on polycarbonate were prepared.

Effect of etching parameters on antireflection properties of Si subwavelength grating structures for solar cell applications

NASA Astrophysics Data System (ADS)

Leem, J. W.; Song, Y. M.; Lee, Y. T.; Yu, J. S.

2010-09-01

Silicon (Si) subwavelength grating (SWG) structures were fabricated on Si substrates by holographic lithography and subsequent inductively coupled plasma (ICP) etching process using SiCl4 with or without Ar addition for solar cell applications. To ensure a good nanosized pattern transfer into the underlying Si layer, the etch selectivity of Si over the photoresist mask is optimized by varying the etching parameters, thus improving antireflection characteristics. For antireflection analysis of Si SWG surfaces, the optical reflectivity is measured experimentally and it is also calculated theoretically by a rigorous coupled-wave analysis. The reflectance depends on the height, period, and shape of two-dimensional periodic Si subwavelength structures, correlated with ICP etching parameters. The optimized Si SWG structure exhibits a dramatic decrease in optical reflection of the Si surface over a wide angle of incident light ( θ i ), i.e. less than 5% at wavelengths of 300-1100 nm, leading to good wide-angle antireflection characteristics (i.e. solar-weighted reflection of 1.7-4.9% at θ i <50°) of Si solar cells.

Analysis of holographic polymer-dispersed liquid crystals (HPDLCs) for tunable low frequency diffractive optical elements recording

NASA Astrophysics Data System (ADS)

Fernández, R.; Gallego, S.; Márquez, A.; Francés, J.; Martínez, F. J.; Pascual, I.; Beléndez, A.

2018-02-01

Holographic polymer dispersed liquid crystals (HPDLCs) are the result of the optimization of the photopolymer fabrication techniques. They are made by recording in a photopolymerization induced phase separation process (PIPS) in which the liquid crystal molecules diffuse to dark zones in the diffraction grating originated. Thanks to the addition of liquid crystal molecules to the composition, this material has a dynamic behavior by reorientation of the liquid crystal molecules applying an electrical field. In this sense, it is possible to use this material to make dynamic devices. In this work, we study the behavior of this material working in low frequencies with different spatial periods of blazed gratings, a sharp profile whose recording is possible thanks to the addition of a Holoeye LCoS-Pluto spatial light modulator with a resolution of 1920 × 1080 pixels (HD) and a pixel size of 8 × 8 μm2. This device allows us to have an accurate and dynamic control of the phase and amplitude of the recording beam.

Visual gas sensors based on dye thin films and resonant waveguide gratings

NASA Astrophysics Data System (ADS)

Davoine, L.; Schnieper, M.; Barranco, A.; Aparicio, F. J.

2011-05-01

A colorimetric sensor that provides a direct visual indication of chemical contamination was developed. The detection is based on the color change of the reflected light after exposure to a gas or a liquid. The sensor is a combination of a chemically sensitive dye layer and a subwavelength grating structure. To enhance the perception of color change, a reference area sealed under a non-contaminated atmosphere is used and placed next to the sensor. The color change is clearly visible by human eyes. The device is based on photonic resonant effects; the visible color is a direct reflection of some incoming light, therefore no additional supplies are needed. This makes it usable as a standalone disposable sensor. The dye thin film is deposited by Plasma enhanced chemical vapor deposition (PECVD) on top of the subwavelength structure. The latter is made by combining a replication process of a Sol-Gel material and a thin film deposition. Lowcost fabrication and compatibility with environments where electricity cannot be used make this device very attractive for applications in hospitals, industries, with explosives and in traffic.

Ultrahigh-Temperature Regeneration of Long Period Gratings (LPGs) in Boron-Codoped Germanosilicate Optical Fibre

PubMed Central

Liu, Wen; Cook, Kevin; Canning, John

2015-01-01

The regeneration of UV-written long period gratings (LPG) in boron-codoped germanosilicate “W” fibre is demonstrated and studied. They survive temperatures over 1000 °C. Compared with regenerated FBGs fabricated in the same type of fibre, the evolution curves of LPGs during regeneration and post-annealing reveal even more detail of glass relaxation. Piece-wise temperature dependence is observed, indicating the onset of a phase transition of glass in the core and inner cladding at ~500 °C and ~250 °C, and the melting of inner cladding between 860 °C and 900 °C. An asymmetric spectral response with increasing and decreasing annealing temperature points to the complex process dependent material system response. Resonant wavelength tuning by adjusting the dwell temperature at which regeneration is undertaken is demonstrated, showing a shorter resonant wavelength and shorter time for stabilisation with higher dwell temperatures. All the regenerated LPGs are nearly strain-insensitive and cannot be tuned by applying loads during annealing as done for regenerated FBGs. PMID:26307991

Reflection Grating Array Associated with the Reflection Grating Spectrometer Developed by the Space Research Organization of the Netherlands for the X-ray Multi-Mirror Mission (XMM)

NASA Technical Reports Server (NTRS)

Kahn, Steven M.

2001-01-01

The University of California, Berkeley (UCB) served as the Principal Investigator institution for the United States participation in the development of the Reflection Grating Spectrometer (RGS) which included the design, development, fabrication, and testing of the Reflection Grating Assembly (RGA). UCB was assisted in this role by the Lawrence Livermore National Laboratory and Columbia University who provided the primary facilities, materials, services and personnel necessary to complete the development. UC Berkeley's Dr. Steven Kahn provided the technical and scientific oversight for the design. development and testing of the RGA units by monitoring the performance of the units at various stages in their development. Dr. Kahn was also the primary contact with the Space Research Organization of the Netherlands (SRON) and represented the RGA development at all SRON and European Space Agency (ESA) reviews of the RGA status. In accordance with the contract, the team designed and developed novel optical technology to meet the unique requirements of the RGS. The ESA XMM-Newton Mission carries two identical Reflection Grating Spectrometers (RGS) behind two of its three nested sets of Wolter I type mirrors. The instrument allows high-resolution measurements in the soft X-ray range (6 to 38 angstroms or 2.1 to 0.3 keV) with a maximum effective area of about 140 sq cm at 15 angstroms. Its design is optimized for the detection of the K-shell transitions of carbon, nitrogen, oxygen, neon, magnesium, and silicon. as well as the L shell transitions of iron. The RGA itself consists of two units. A structure for each unit was designed to hold up to 220 gratings. In its final configuration, one unit holds 182 gratings and the second hold 181 gratings.

Fast and Scalable Fabrication of Microscopic Optical Surfaces and its Application for Optical Interconnect Devices

NASA Astrophysics Data System (ADS)

Summitt, Christopher Ryan

The use of optical interconnects is a promising solution to the increasing demand for high speed mass data transmission used in integrated circuits as well as device to device data transfer applications. For the purpose, low cost polymer waveguides are a popular choice for routing signal between devices due to their compatibility with printed circuit boards. In optical interconnect, coupling from an external light source to such waveguides is a critical step, thus a variety of couplers have been investigated such as grating based couplers [1,2], evanescent couplers [3], and embedded mirrors [4-6]. These couplers are inherently micro-optical components which require fast and scalable fabrication for mass production with optical quality surfaces/structures. Low NA laser direct writing has been used for fast fabrication of structures such as gratings and Fresnel lenses using a linear laser direct writing scheme, though the length scale of such structures are an order of magnitude larger than the spot size of the focused laser of the tool. Nonlinear writing techniques such as with 2-photon absorption offer increased write resolution which makes it possible to fabricate sub-wavelength structures as well as having a flexibility in feature shape. However it does not allow a high speed fabrication and in general are not scalable due to limitations of speed and area induced by the tool's high NA optics. To overcome such limitations primarily imposed by NA, we propose a new micro-optic fabrication process which extends the capabilities of 1D, low NA, and thus fast and scalable, laser direct writing to fabricate a structure having a length scale close to the tool's spot size, for example, a mirror based and 45 degree optical coupler with optical surface quality. The newly developed process allows a high speed fabrication with a write speed of 2600 mm²/min by incorporating a mask based lithography method providing a blank structure which is critical to creating a 45 degree slope to form the coupler surface. In this method, instead of using an entire exposure in a pixelated manner, only a portion of the Gaussian profile is used, allowing a reduced surface roughness and better control of the surface shape than previously possible with this low NA beam. The surface figure of the mirror is well controlled below 0.04 waves in root-mean-square (RMS) at 1.55 mum wavelength, with mirror angle of 45+/-1 degrees. The coupling efficiency is evaluated using a set of polymer waveguides fabricated on the same substrate as the complete proof of concept device. Device insertion loss was measured using a custom built optical test station and a detailed loss analysis was completed to characterize the optical coupling efficiency of the mirror. Surface roughness and angle were also experimentally confirmed. This process opens up a pathway towards large volume fabrication of free-form and high aspect ratio optical components which have not yet pursued, along with well-defined optical structures on a single substrate. In this dissertation, in Chapter 1, we provide an overview of optical surface fabrication in conjunction with current state of the art on fabrication of free form surfaces in macro and microscopic length scale. The need for optical interconnects is introduced and fabrication methods of micro-optical couplers are reviewed in Chapter 2. In Chapter 3, the complete fabrication process of a mirror based coupler is presented including a custom alignment procedure. In Chapter 4, we provide the integration procedure of the optical couplers with waveguides. In Chapter 5, the alignment of two-lithographic methods is discussed. In Chapter 6, we provide the fabrication procedure used for the waveguides. In Chapter 7, the experimental evaluation and testing of the optical coupler is described. We present a custom test station used for angle verification and optical coupler efficiency measurement. In Chapter 8, a detailed loss analysis of the device is presented including suggestions for future reductions in loss. Conclusions and future work considerations are addressed in Chapter 9.

Research and design on orthogonal diffraction grating-based 3D nanometer displacement sensor

NASA Astrophysics Data System (ADS)

Liu, Baoshuai; Yuan, Yibao; Yin, Zhehao

2017-10-01

This study concerns an orthogonal diffraction grating-based nanometer displacement sensor. In this study, we performed calculation of displacements in the XYZ directions. In the optical measured path part, we used a two-dimensional orthogonal motion grating and a two-dimensional orthogonal reference grating with the pitch of 0.5um to measure the displacement of XYZ in three directions by detecting ±1st diffraction fringes. The self-collimated structure of the grating greatly extended the Z-axis range. We also simulated the optical path of the sensor with ZEMAX software and verified the feasibility of the scheme. For signal subdivision and processing, we combined large number counting (completed grating line) with small number counting (digital subdivision), realizing high multiples of subdivision of grating interference signals. We used PC to process the interference fringes and greatly improved the processing speed. In the scheme, the theoretical multiples of subdivision could reach 1024 with 10-bit AD conversion, but the actual multiples of subdivision was limited by the quality of the grating interference signals. So we introduced an orthogonal compensation circuit and a filter circuit to improve the signal quality.