Three-beam Interference Research Articles

Self-compensated microstructure fiber optic sensor to detect high hydrogen concentration.

Dual-cavity microstructure fiber optic hydrogen sensor based on evaporated Pt/WO(3) film was proposed and experimentally explored in this paper, which provides a novel solution to detect high hydrogen concentration (10-30% H(2)). Dual-cavity microstructure fabricated by splicer is composed of an inner air-cavity and a collapsed photonic crystal fiber cavity. The proposed sensor has the advantages of miniature structure, stable configuration, low cost. Based on three-beam interference model and verification experiments, the compensation function to the fluctuation of light source and fiber loss is proved from the theoretical simulation and experimental investigation. The sensor has a short response time (1min), good repeatability and reliability. Besides, the change of temperature affects the response value of the hydrogen sensor, but the impact can be neglected in 10-30% H(2).

Discrete nonplanar reflections from an ultrashort pulse written volume Bragg grating.

In this Letter, we present a direct writing technique for two-dimensional periodic volume Bragg gratings (VBGs) in fused silica based on the phase mask technology, ultrashort laser pulses, and three-beam interference. An algorithm to predict the grating pattern and its diffraction behavior under collimated, spectral broad illumination is developed. The predicted data are in good agreement with the measurements.

Antireflection silicon structures with hydrophobic property fabricated by three-beam laser interference

This paper demonstrates antireflective structures on silicon wafer surfaces with hydrophobic property fabricated by three-beam laser interference. In this work, a three-beam laser interference system was set up to generate periodic micro–nano hole structures with hexagonal distributions. Compared with the existing technologies, the array of hexagonally-distributed hole structures fabricated by three-beam laser interference reveals a design guideline to achieve considerably low solar-weighted reflectance (SWR) in the wavelength range of 300–780nm. The resulting periodic hexagonally-distributed hole structures have shown extremely low SWR (1.86%) and relatively large contact angle (140°) providing with a self-cleaning capability on the solar cell surface.

偏振态对三光束激光干涉分布的影响

偏振态对三光束激光干涉分布的影响

Effects of azimuthal angles on laser interference lithography.

This paper discusses the effects of azimuthal angles on two-, three-, and four-beam laser interference. In two- or three-beam laser interference, periodic surface structures of lines or dots were obtained. In four-beam laser interference with the polarization mode of TE-TM-TE-TM, the modulation in a particular direction was formed and calculated. In the work, a He-Ne laser system was used to simulate two-, three-, and four-beam laser interference, and the interference pattern was detected by a CCD. A high-power Nd:YAG laser interference lithography system was set up to pattern silicon wafers. In the experiments, one azimuthal angle was changed every time to form interference patterns when polarization states were fixed and incident angles were equal. The experimental results have shown that the azimuthal angle affects the periods and feature sizes of the interference patterns and the fabricated surface structures, which are in accordance with the theoretical and computer simulation results.

Optical Properties of Electrically Tunable Two-Dimensional Photonic Lattice Structures Formed in a Holographic Polymer-Dispersed Liquid Crystal Film: Analysis and Experiment.

We report on theoretical and experimental investigations of optical wave propagations in two-dimensional photonic lattice structures formed in a holographic polymer-dispersed liquid crystal (HPDLC) film. In the theoretical analysis we employed the 2 × 2 matrix formulation and the statistical thermodynamics model to analyze the formation of anisotropic photonic lattice structures by holographic polymerization. The influence of multiple reflections inside an HPDLC film on the formed refractive index distribution was taken into account in the analysis. In the experiment we fabricated two-dimensional photonic lattice structures in an HPDLC film under three-beam interference holographic polymerization and performed optical measurements of spectral transmittances and wavelength dispersion. We also demonstrated the electrical control capability of the fabricated photonic lattice structure and its dependence on incident wave polarization. These measured results were compared with the calculated ones by means of photonic band and beam propagation calculations.

Direct periodic patterning of GaN-based light-emitting diodes by three-beam interference laser ablation

We report on the direct patterning of two-dimensional periodic structures in GaN-based light-emitting diodes (LEDs) through laser interference ablation for the fast and reliable fabrication of periodic micro- and nano-structures aimed at enhancing light output. Holes arranged in a two-dimensional hexagonal lattice array having an opening size of 500 nm, depth of 50 nm, and a periodicity of 1 μm were directly formed by three-beam laser interference without photolithography or electron-beam lithography processes. The laser-patterned LEDs exhibit an enhancement in light output power of 20% compared to conventional LEDs having a flat top surface without degradation of electrical and optical properties of the top p-GaN layer and the active region, respectively.

(Invited) Carrier Dynamics and Photon Management for Improvement in Quantum Efficiencies of GaN-Based Visible Light-Emitting Diodes

Data and analysis are presented employing several new methods to address carrier dynamics and photon management issues in order to improve internal quantum efficiency (IQE) and light-extraction efficiency (LEE) of GaN-based light-emitting diodes (LEDs). First, the roles of a new InAlN electron blocking layer (EBL) and hole transport among quantum wells (QWs) are discussed with a focus on the mitigation of efficiency droop at high current densities. While the origins of the efficiency droop remain to be controversial, currently suggested origins are all associated with carrier dynamics: the effect of the electron leakage being related to carrier confinement; hole transport to active region being pertinent to carrier injection and concentration in each QW, and Auger recombination becoming more dominant with increasing carrier density in each QW. The strategy for the improvement, therefore, includes (1) confining electrons in the active region as much as possible, (2) injecting holes into the active region as much as possible, (3) distributing the both carriers among QWs as uniformly as possible. In order to implement the strategies, we especially studied EBLs and hole injection and transport in the multiple QW (MQW) active region. The effects of the various EBLs on the efficiency droop was compared (Figure 1), showing the lowest efficiency droop ratio of ~18% for the LEDs with InAlN EBL due to better electron confining/blocking effect than the standard EBLs. Hole injection (into active region) and transport (across MQWs) are as important as electron confinement. Also, they are not inter-related. Uniform distributions of electrons and holes with the same concentration in each QW are a goal to effectively mitigate the efficiency droop. Whereas the uniform distribution of electrons among QWs is achieved without difficulties, that of hole is quite challenging. We employed triple-wavelength-emitting MQWs with different bandgap energies for the experimental evaluation of the hole distribution among MQWs (Figure 2), showing hole transport and resulting distribution of holes can be engineered by p-type layers. Secondly, new way of surface patterning is demonstrated. The periodic surface patterns having 2-dimensional hexagonal array were directly achieved by three-beam interference laser ablation technique without photolithography processes (Figure 3), resulting in improvement of LEE by ~20%. This new direct laser patterning also maintained ohmic behavior of contacts on p-type surface, unlike the case of the patterning using plasma dry etching.

(Invited) Carrier Dynamics and Photon Management for Improvement in Quantum Efficiencies of GaN-Based Visible Light-Emitting Diodes

Data and analysis are presented employing several new methods to address carrier dynamics and photon management issues in order to improve internal quantum efficiency and light-extraction efficiency of GaN-based light-emitting diodes. For the carrier dynamics, studied are the effects of a newly-developed InAlN electron blocking layer and a p-InGaN:Mg layer on electron blocking and hole transport through multiple-quantum well active region. Also, a new technique of direct surface patterning is demonstrated using three-beam interference laser ablation for efficient photon management.

Polarization-dependent enhanced photoluminescence and polarization-independent emission rate of quantum dots on gold elliptical nanodisc arrays.

We have fabricated gold (Au) elliptical nanodisc (ND) arrays via three-beam interference lithography and electron beam deposition of gold. The enhanced photoluminescence intensity and emission rate of quantum dots (QDs) near to the Au elliptical NDs have been studied by tuning the nearest distance between quantum dots and Au elliptical NDs. We found that the photoluminescence intensity is polarization-dependent with the degree of polarization being equal to that of the light extinction of the Au elliptical NDs, while the emission rate is polarization-independent. This is resulted from the plasmon-coupled emission via the coupling between the QD dipole and the plasmon nano-antenna. Our experiments fully confirm the evidence of the plasmophore concept proposed recently in the interaction of the QDs with metal nanoparticles.

Three-beam interference with circular polarization for structured illumination microscopy

Three-dimensional structured illumination microscopy (3D-SIM) is a wide-field technique that can provide doubled resolution and improved image contrast. In this work, we demonstrate a simple approach to 3D-SIM - using three-beam interference with circular polarization to generate the pattern of structured illumination, so that the modulation contrast is routinely maintained at all orientations without a complicated polarization rotator or mechanical motion. We derive the resultant intensity distribution of the interference pattern to confirm the modulation contrast independent of orientation, and compare the result with those using interfering beams of linear polarization. To evaluate the influence of the modulation contrast on imaging, we compare the simulated SIM images of 100-nm beads. Experimental results are presented to confirm the simulations. Our approach requires merely a λ/4-wave plate to alter the interfering beams from linear to circular polarization. This simplicity together with the use of a spatial light modulator to control the interference pattern facilitates the implementation of a 3D-SIM system and should broaden its application.

Funnel-structured TiO2 electrode for improved charge extraction in dye-sensitized solar cell

We here show that the current density and efficiency of dye-sensitized solar cell (DSSC) can be much enhanced by generating more bulky-structured funnels inside the typical TiO2 electrode. This approach is fundamentally based on the pulsed laser-induced desorption and melting of TiO2 nanoparticles. Three-beam interference was utilized to fabricate the periodic electrode structure. While the dye coverage was little influenced by this process because a small volume fraction of the electrode was converted into the bulky structure, the photoexcited electrons could be more effectively extracted owing to the prolonged diffusion length. As a result, the photocurrent density and efficiency of DSSCs were much improved. The enhancement of both factors was reliably ascertained by the multiple-cell characterization. The funnel cells exhibited an average short-circuit current density of 19.77mA/cm2 and an efficiency of 9.44%, while 17.30mA/cm2 and 8.27% were obtained from the reference cells.

Formation and morphological transformation of polarization singularities: hunting the monstar

The theoretical formalism and experimental measurements to form and transform between the three morphologies of the polarization singular patterns—star, lemon and monstar—are presented here. The monstar is statistically rare in isotropic random fields but its controllable realization is achieved by tuning the field anisotropy in three-beam interference.

High-throughput fabrication of large-scale highly ordered ZnO nanorod arrays via three-beam interference lithography

Download options Please wait... Supplementary files Supplementary information PDF (20044K) Article information DOI https://doi.org/10.1039/C3CE41558A Article type Communication Submitted 04 Aug 2013 Accepted 23 Aug 2013 First published 23 Aug 2013 Download Citation CrystEngComm, 2013,15, 8416-8421 BibTex EndNote MEDLINE ProCite ReferenceManager RefWorks RIS Permissions Request permissions High-throughput fabrication of large-scale highly ordered ZnO nanorod arrays via three-beam interference lithography X. Chen, X. Yan, Z. Bai, Y. Shen, Z. Wang, X. Dong, X. Duan and Y. Zhang, CrystEngComm, 2013, 15, 8416 DOI: 10.1039/C3CE41558A To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page. If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given. If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page. Read more about how to correctly acknowledge RSC content. Social activity Tweet Share Search articles by author Xiang Chen Xiaoqin Yan Zhiming Bai Yanwei Shen Zengze Wang Xianzi Dong Xuanming Duan Yue Zhang

Direct Laser Interference Patterning of tetrahedral amorphous carbon films for tribological applications

In this work, the influence of surface topography and micro structural changes on the tribological properties of tetrahedral amorphous carbon coatings (ta-C) structured using a holographic technique the direct laser interference pattering (DLIP) is investigated. By utilizing a nanosecond pulsed UV-laser (wavelength 355nm), both ablation and graphitization thresholds were determined as a function of the pulse number. Incubation effects for the ablation threshold (~205mJcm−2) were found to be negligible. However, for the graphitization of the film thresholds varying from 47 to 74mJcm−2 were observed depending on the number of laser pulses utilized (from 1 to 30) and thus obtaining an incubation factor of 1.13. Using two- and three-beam interference setups, dot- and line-like periodic arrays were fabricated. The tribological performance of these patterns was investigated under reciprocating sliding with a ball on disk method under non-lubricated conditions showing that coefficient of friction can be reduced from~0.089 (un-patterned) to~0.055 patterned ta-C (~30% reduction). The results can be explained based on the reduction of surface contact area combined with high hardness as well as the good intrinsic tribological properties of the ta-C films.

Parametric constraints in multi-beam interference

Multi-beam interference (MBI) represents a method of producing one-, two-, and three-dimensional submicron periodic optical-intensity distributions for applications including micro- and nano-electronics, photonic crystals, metamaterial, biomedical structures, optical trapping, and numerous other subwavelength structures. Accordingly, numerous optical configurations have been developed to implement MBI. However, these configurations typically provide limited ability to condition the key parameters of each interfering beam. Constraints on individual beam amplitudes and polarizations are systematically considered to understand their effects on lithographically useful MBI periodic patterning possibilities. A method for analyzing parametric constraints is presented and used to compare the optimized optical-intensity distributions for representative constrained systems. Case studies are presented for both square and hexagonal-lattices produced via three-beam interference. Results demonstrate that constraints on individual-beam polarizations significantly impact patterning possibilities and must be included in the systematic design of an MBI system.

Evaluation of optical parameters of quasi-parallel plates with single-frame interferogram analysis methods

The surface flatness of transparent plates is frequently tested in Fizeau and Twyman-Green interferometers. In case of quasi-parallel plates, however, a common problem is the additional reflection from the plate rear surface and three-beam interference is encountered. Our new method of deriving shape and optical thickness variations of the plate requires recording two interferograms: a two-beam interferogram without a reference beam and the three-beam interference one. The images are processed using single-frame techniques only. The proposed method does not require modification of a sample or sophisticated equipment and complicated data analysis. Full Text: PDF

Pattern-integrated interference lithography: single-exposure fabrication of photonic-crystal structures

Multibeam interference represents an approach for producing one-, two-, and three-dimensional periodic optical-intensity distributions with submicrometer features and periodicities. Accordingly, interference lithography (IL) has been used in a wide variety of applications, typically requiring additional lithographic steps to modify the periodic interference pattern and create integrated functional elements. In the present work, pattern-integrated interference lithography (PIIL) is introduced. PIIL is the integration of superposed pattern imaging with IL. Then a pattern-integrated interference exposure system (PIIES) is presented that implements PIIL by incorporating a projection imaging capability in a novel three-beam interference configuration. The purpose of this system is to fabricate, in a single-exposure step, a two-dimensional periodic photonic-crystal lattice with nonperiodic functional elements integrated into the periodic pattern. The design of the basic system is presented along with a model that simulates the resulting optical-intensity distribution at the system sample plane where the three beams simultaneously interfere and integrate a superposed image of the projected mask pattern. Appropriate performance metrics are defined in order to quantify the characteristics of the resulting photonic-crystal structure. These intensity and lattice-vector metrics differ markedly from the metrics used to evaluate traditional photolithographic imaging systems. Simulation and experimental results are presented that demonstrate the fabrication of example photonic-crystal structures in a single-exposure step. Example well-defined photonic-crystal structures exhibiting favorable intensity and lattice-vector metrics demonstrate the potential of PIIL for fabricating dense integrated optical circuits.

Pattern-integrated interference lithography instrumentation

Multi-beam interference (MBI) provides the ability to form a wide range of sub-micron periodic optical-intensity distributions with applications to a variety of areas, including photonic crystals (PCs), nanoelectronics, biomedical structures, optical trapping, metamaterials, and numerous subwavelength structures. Recently, pattern-integrated interference lithography (PIIL) was presented as a new lithographic method that integrates superposed pattern imaging with interference lithography in a single-exposure step. In the present work, the basic design and systematic implementation of a pattern-integrated interference exposure system (PIIES) is presented to realize PIIL by incorporating a projection imaging capability in a novel three-beam interference configuration. A fundamental optimization methodology is presented to model the system and predict MBI-patterning performance. To demonstrate the PIIL method, a prototype PIIES experimental configuration is presented, including detailed alignment techniques and experimental procedures. Examples of well-defined PC structures, fabricated with a PIIES prototype, are presented to demonstrate the potential of PIIL for fabricating dense integrated optical circuits, as well as numerous other subwavelength structures.

Block copolymer supramolecular assemblies hierarchically structured by three-beam interference laser ablation

We report the fabrication of hierarchical structures by combining bottom-up self-assembly of block copolymer supramolecular assemblies with top-down three-beam interference laser ablation methods. To fabricate the shorter length scale in the hierarchical structures, we use supramolecular assemblies (SMAs) of azobenzene compounds hydrogen bonded with poly(vinyl pyridine) blocks of polystyrene-block-poly(vinyl pyridine) block copolymers. The SMAs form phase separation nanostructures by solvent vapor annealing. The longer length scale of the hierarchical structures is fabricated by three-beam interference laser ablation on the phase separated nanostructures of the SMAs. The ablation process is induced by single laser shots with 35 ns pulse duration. Tuning of both length scales is feasible by changing the interference conditions and chemical composition of the SMAs, which enables efficient and straightforward fabrication of hierarchical photonic structures.