Multiple-beam Interference Research Articles

Java Applet Technology for Design Interference Optical Coating

Java is a high-level , third generation programming language were introduced Javaoptics Open Source Physics (OSP) as a new simulation for design one of the most important interference optical coating called antireflection coating. It is recent developments in deign thin-film coatings. (OSP) shows multiple beam interferences from a parallel dielectric thin film and the evolution of reflection factors. It is simple to use and efficiently also can serve educational purposes. The obtained results have been compared with needle method

Analytic method of studying defect mode of 1D doped phononic crystal

For the analytic study of the defect mode of 1D doped phononic crystal, the multiple-beam interference method and Bloh theorem are adopted, the analytical formula of defect mode is derived and the defect mode of 1D doped phononic crystal is studied. The varition law of defect mode is obtained. The method in freed from the weaknewes of other methods that cannot carry on the analysis of defect mode. The method is valid and accurate method of studying the defect mode of 1D doped phononic crystal.

Blue top-emitting organic light-emitting devices based on wide-angle interference enhancement and suppression of multiple-beam interference

Blue top-emitting organic light-emitting devices (TEOLEDs) based on blue phosphor iridium (III) bis[(4,6-difluorophenyl)-pyridinato-N,C 2′] picolinate (FIrpic) are demonstrated. Instead of using microcavity effects to obtain the blue top emission in conventional reports, the blue emission with a good chromaticity is achieved in this paper through the suppression of the multiple-beam interference by introducing a 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline light outcoupling layer onto the semitransparent Sm/Ag cathode. The electroluminescent performances of the blue emission is further improved based on the effective carrier transport and the consideration of the wide-angle interference at the emission peak of FIrpic with a maximum luminance of 8029 cd/m 2 and a luminous efficiency of 4.02 cd/A achieved at 14 V and 10 V, respectively. With a polarizer on the top cathode, a high pixel contrast ratio of 113:1 is realized under an ambient illumination of 140 lx and a pixel brightness of 1000 cd/m 2.

Interferometric lithography for nanoscale feature patterning: a comparative analysis between laser interference, evanescent wave interference, and surface plasmon interference

In this paper, we experimentally demonstrate and compare single-exposure multiple-beam interference lithography based on conventional laser interference, evanescent wave interference, and surface plasmon interference. The proposed two-beam and four-beam interference approaches are carried out theoretically and verified experimentally, employing the proposed configurations so as to realize the patterning of one- and two-dimensional periodic features on photoresists. A custom-fabricated grating is employed in the configuration in order to achieve two- and four-beam interference.

Reconstruction of refractive indices distribution in 3D using a single pattern of multiple-beam interference fringes for online investigation of necking phenomenon

A proposed model for reconstructing the refractive indices distribution in three dimensions is introduced. The reconstruction process requires a single multiple-beam interference pattern which facilitates online investigation of structural changes. In order to increase the accuracy of the measured refractive indices, fringe analysis was applied on the basis of the inverse interferogram principle proposed in this article. Verification of the modified technique was made using reconstructed noise-free interference patterns. The modified technique is helpful in studying the necking phenomenon observed during creep extension of polypropylene fibres. Refractive index distribution in 3D across the fibre was determined and the birefringence profile was calculated. Microinterferograms are given for illustration.

Determination of absolute size of fundus objects

Creating multiple beam interference fringes on the retina using the "retina fringe projector" (RFP) provides us with a scale which can be used to determine the absolute size of objects at the fundus. The procedure is tested on an model eye, the optical parameters of which are varied in order to simulate different refraction conditions. The RFP was used to determine the size of a known object at the model fundus; the result was then checked against the real value of the object. In a second series of measurements, the RFP fringes were included in fundus photos of 52 patients with varying levels of ametropia, taken at the University Eye Clinic in Jena using the FF450 fundus camera (manufacturer: Carl Zeiss Meditec AG) for diagnostic purposes. The distance between the fringes was determined using both the RFP and the Littmann method. The differences to the real value of the fundus size of a known object deviated on average by 1 to 2%, and always remained under 3% in the model eye. A very good correlation between RFP and Littmann methods results could be found in the clinical part of the study. The resulting deviations are below 2.5%. Integration of a RFP in a fundus camera permits measurement of absolute values of the retina, regardless of the type of observation or documentation. Knowing the real size of fundus objects holds a potential in many clinical classification scales of fundus objects such as drusen or vessels, or in optimizing photodynamic therapy spot size measurement.

The influence of lanthanum doping position in ultra-thin HfO 2 films for high-k gate dielectrics

Lanthanum dopant positioning at HfO 2 ultra-thin films was achieved by the co-sputtering method. The physical properties of graded doping HfO 2/HfLaO/p-Si and HfLaO/HfO 2/p-Si structures after 850 °C postannealing were compared. The thickness of the monolayer was analyzed by X-ray reflectivity and confirmed by the multiple beam interference model. The HfO 2 and silicate phases were characterized by X-ray diffraction patterns. It is found that crystallization depends on the ratio of stacked film thicknesses, and the HfLaO/HfO 2/Si structure has more silicate formation at the interface than the HfO 2/HfLaO/Si structure. Metal–insulator–semiconductor capacitors were fabricated. The electrical properties including leakage current, conduction mechanism, flatband voltage shift, and barrier height were studied.

Radius of curvature measurement of spherical smooth surfaces by multiple-beam interferometry in reflection

In this paper a method is presented to accurately measure the radius of curvature of different types of curved surfaces of different radii of curvatures of 38 000,18 000 and 8000 mm using multiple-beam interference fringes in reflection. The images captured by the digital detector were corrected by flat fielding method. The corrected images were analyzed and the form of the surfaces was obtained. A 3D profile for the three types of surfaces was obtained using Zernike polynomial fitting. Some sources of uncertainty in measurement were calculated by means of ray tracing simulations and the uncertainty budget was estimated within λ/40.

Large-Area, Near-Infrared (IR) Photonic Crystals with Colloidal Gold Nanoparticles Embedding

A polymeric composite material composed of colloidal gold nanoparticles (<10 nm) and SU8 has been utilized for the fabrication of large-area, high-definition photonic crystal. We have successfully fabricated near-infrared photonic crystal slabs from composite materials using a combination of multiple beam interference lithography and reactive ion etching processes. Doping of colloidal gold nanoparticles into the SU8 photopolymer results in a better definition of structural features and hence in the enhancement of the optical properties of the fabricated photonic crystals. A 2D air hole array of triangular symmetry with a hole-to-hole pitch of approximately 500 nm has been successfully fabricated in a large circular area of 1 cm diameter. Resonant features observed in reflectance spectra of our slabs are found to depend on the exposure time, and can be tuned over a range of near-infrared frequencies.

Distortion of optical feedback signals in microchip Nd:YAG lasers subjected to external multi-beam interference feedback

This paper proposes a theoretical analysis for the characteristics of an external cavity Nd:YAG laser with feedback of multiple-beam interference, which is induced by the multi-reentrance of the light from the external Fabry–Perot cavity. The theoretical model considers the multiple beam interference of the external Fabry–Perot cavity. It is found that the optical feedback signals are distorted to pulse waveforms instead of the sinusoidal ones in conventional feedback. The experimental results are in good agreement with the theoretical analysis. The obtained theoretical and experimental results can advance the development of a laser feedback interferometer.

Surface microtopography measurement of a standard flat surface by multiple-beam interference fringes at reflection

This paper describes a multiple-beam interferometry technique at reflection for measuring the microtopography of an optical flat nominally of λ/20. The measured value is the result of a piezoelectric phase shifting that made it possible to cover the area between the orders. The exposure area of the tested optical flat covered by the collimated laser beam is about 2 cm. The images captured by the digital detector were corrected using dark/flat field method. The uncertainty in the measurement due to incomplete parallelism of the incident beam and the inhomogeneity of the reflecting layers were calculated from the departure of the fringe position produced with a written ray tracing program. The uncertainty budget was estimated to be of the order of λ/40.

Multiple beam ring interference: A master curve for interference pattern design

A Master Curve, capable of describing all possible configurations, was deduced by using the so-called Wigner Distribution Function, for a cylindrically-symmetric array of interfering beams, of the type utilized nowadays for optical tweezers and multiple-beam interference optical cages.

Polarization-independent drop filters based on photonic crystal self-collimation ring resonators

We report here a polarization-independent drop filter (PIDF) based on a photonic crystal self-collimation ring resonator (SCRR). Despite of the large birefringence associated with the polarization-dependent dispersion properties, we demonstrate a PIDF based on multiple-beam interference theory and polarization peak matching (PPM) technique. The PIDF performance was also investigated based on finite-difference time-domain (FDTD) technique, with excellent agreement between the theory and the simulation. For the designed drop wavelength of 1550 nm, the polarization-independent free spectral range is about 36.1 nm, which covers the whole optical communication C-band window. The proposed PIDFs are highly desirable for applications in photonic integrated circuits (PICs).

Three-dimensional microfabrication of materials by femtosecond lasers for photonics applications

Femtosecond laser fabrication of three-dimensional structures for photonics applications is reviewed. Fabrication of photonic crystal structures by direct laser writing and holographic recording by multiple beam interference techniques are discussed. The physical mechanisms associated with structure formation and postfabrication are described. The advantages and limitations of various femtosecond laser microfabrication techniques for the preparation of photonic crystals and elements of microelectromechanical and micro-optofluidic systems are discussed.

A simple method for Bragg diffraction in volume holographic gratings

We discuss a simple beam interference approximation method for deriving the angular selectivity of diffraction in weakly modulated volume holographic gratings. The results obtained using the multiple beam interference model agree qualitatively with the results obtained from a physical optics treatment of the coupled-wave theory for volume holographic gratings.

Feasibility study of the application of radially polarized illumination to solid immersion lens-based near-field optics

We analyzed the behavior of the electric field in a focal plane consisting of a solid immersion lens (SIL), an air gap, and a measurement sample for radially polarized illumination in SIL-based near-field optics with an annular aperture. The analysis was based on the Debye diffraction integral and multiple beam interference. For SIL-based near-field optics whose NA is higher than unity, radially polarized light generates a smaller beam spot on the bottom surface of a SIL than circularly polarized light; however, the beam spot on the measurement sample is broadened with a more dominant transverse electric field. By introducing an annular aperture technique, it is possible to decrease the effects of the transverse electric field, and therefore the size of the beam spot on the measurement sample can be small. This analysis could have various applications in near-field optical storage, near-field microscopy, lithography at ultrahigh resolution, and other applications that use SILs for high resolution.

Ronchigram quantification via a non-complementary dark-space effect

We observe a non-complementary dark-space produced when two Ronchi-grams, at zero-phase and pi-phase, are overlapped and use these dark spaces to quantify Ronchi-grams. Diffraction and multiple beam interference effects narrow the Ronchi fringes created with a coherent point source illumination and prevent accurate determination of the geometrical fringe edges. The dark spaces created when the intensity of two Ronchi grams is added allow assessing the geometrical edge at the dark space middle providing a way to reduce measurement errors. We re-construct the wavefront deformation in a test beam with a 35-term Zernike polynomial.

Laser interference lithography for nanoscale structuring of materials: From laboratory to industry

Periodic structures are of increasing interest in many fields such as nanotechnology and biotechnology among others. Laser Interference Lithography (LIL) has been widely studied for the fabrication of periodic structures. However, a LIL tool for the nanoscale structuring of materials that can scale beyond laboratory prototypes into cost effective industrial processes is not yet defined. In this work, we describe a versatile and automatic high-power multiple beam interference lithography system design capable of overcoming the limitations of manual setups. Using this system, we have successfully processed photoresist samples on the whole surface of 3 in. silicon wafers, demonstrating the applicability of this prototype to a wide range of device fabrication.

Rapid prototyping of microstructured hydrogels via laser direct-write and laser interference photopolymerisation

We present recent results on fabrication of micrometre- and sub-micrometre-scale structures in polyethylene glycol diacrylate (PEG-DA), a biocompatible hydrogel, useful in biomedical applications. The hydrogel structures were fabricated using two laser-based techniques; laser direct-write photopolymerisation, and multiple-beam laser interference photopolymerisation using continuous wave, nanosecond pulsed and femtosecond pulsed lasers, with light wavelengths of 266 nm, 355 nm, 532 nm and 800 nm. Through these techniques, we demonstrated the ability to fabricate fine structures over large areas without the use of templates or masks. Such structures can be useful for a variety of applications including cell biological studies, tissue engineering and drug delivery.

Micro Fabry Perot light modulator for flat panel display

A new type of Fabry Perot light modulator for displays based on micro-electro-mechanical system technology is proposed. Multiple beam interference theory is used to design the modulator and analyze its characteristics. If Fabry Perot cavity length is one-quarter of the incident wavelength, the transmitted light is blocked by the modulator, and the modulator, which is illuminated from its backside, appears black. If the Fabry Perot cavity length is 0 or one-half of the incident wavelength, light may transmit the Fabry Perot modulator from its backside, and the modulator appears bright. Hence, the modulator may be used for flat panel displays. In this paper one Fabry Perot light modulator based on surface micromachining technology is introduced. The designed modulator has a contrast ratio of 150 and can theoretically be driven by a voltage of 2.4 V.