Accepted papers to appear in an upcoming issue
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Performance Evaluation of Metal Insulator Metal (MIM) SPR Optical Gas Sensor Under the Effect of Gaussian Beams
- received 12/18/2013; accepted 03/06/2014; posted 03/10/2014; Doc. ID 197963
- [full text: PDF (510) KB)]
- Abstract: In this work, the performance of a non-conventional IR Surface Plasmon Resonance SPR gas sensor structure based on the use of a Metal / Insulator / Metal MIM structure is studied. This MIM-based sensor structure gives an enhanced performance five times better than the conventional MI SPR optical gas sensors. The performance of the SPR gas sensors is studied under the effect of oblique incident Gaussian beams with different spot sizes and the performance enhancement of the MIM structure is confirmed for different spot sizes.
- (000.0000) General : General
- (310.0310) Thin films : Thin films
- (310.4165) Thin films : Multilayer design
- (280.4788) Remote sensing and sensors : Optical sensing and sensors
High precision topography measurement through accurate in-focus plane detection with hybrid digital holographic microscope and white light interferometer module
- received 09/24/2013; accepted 03/06/2014; posted 03/10/2014; Doc. ID 198186
- [full text: PDF (1309) KB)]
- Abstract: High precision topography measurement of micro-objects can be realized provided that the in-focus plane of an imaging system is very accurately determined. In common interferometric and holographic microscopy techniques there is no convenient tool for accurate detection of in-focus plane, which meaningfully limits the measurement accuracy. Therefore, in this paper we propose an effective in-focus plane determination technique for high precision topography measurements, which is based on white light interferometry. The proposed method consists of two main steps. Firstly, a calibration of the imaging system with an amplitude object is performed using a common autofocusing method, which allows for accurate localization of an in-focus plane position. Secondly, the position of the detected in-focus plane with respect to the imaging system is measured and used to accurately adjust a sample with the required precision for the measurement. The experimental validation of the proposed method is given for measurement of high numerical aperture microlenses with sub-wavelength accuracy.
- (120.2830) Instrumentation, measurement, and metrology : Height measurements
- (120.4820) Instrumentation, measurement, and metrology : Optical systems
- (090.1995) Holography : Digital holography
Sparse phase-stepping in two-dimensional X-ray phase contrast imaging
- received 03/05/2014; accepted 03/06/2014; posted 03/13/2014; Doc. ID 200589
- [full text: PDF (2637) KB)]
- Abstract: We have developed a sparse phase-stepping (SPS) method for X-ray Talbot-Lau interferometry, which first constructs a sparse phase-stepping intensity pattern of fewer images than the conventional phase-stepping (PS) method and then fills the data gap with neighboring pixels for phase retrieval. The SPS method is highly beneficial in practice since the fundamental difference in spatial resolution between the SPS and the PS methods becomes negligible due to the blur caused by an interferometer. The concept of the SPS method has been proved by the experiment using a small effective source size. Furthermore the experiment using a large effective source size has verified that in practical situations the SPS method can reduce the required number of images for phase retrieval and still offer the retrieved images with as high spatial resolution as the PS method.
- (070.6760) Fourier optics and signal processing : Talbot and self-imaging effects
- (100.5070) Image processing : Phase retrieval
- (120.2650) Instrumentation, measurement, and metrology : Fringe analysis
- (120.4120) Instrumentation, measurement, and metrology : Moire' techniques
- (120.5060) Instrumentation, measurement, and metrology : Phase modulation
- (340.7440) X-ray optics : X-ray imaging
Analysis of optical properties in injection molded and compression molded optical lenses
- received 01/13/2014; accepted 03/05/2014; posted 03/10/2014; Doc. ID 204260
- [full text: PDF (2148) KB)]
- Abstract: Numerical mold-flow simulations and experimental measurements for injection-molded lenses have been investigated in form accuracy on a two-cavity mold with various process conditions. First, form profiles of the molded lenses have been measured together with the corresponding simulated mold temperature distribution and displacement distribution of lens in z direction. Flow-through type layout of cooling channels has been devised for balance of mold temperature distribution in mold cavities with various parametric distances for assessments in uniformity of temperature distribution. Finally, a compression molding process is proposed for the post-process of birefringence relaxation as well as adequate form accuracy of lenses. In conclusions, optimization of process parameters to achieve good form accuracy in multi-cavity mold with symmetric geometry but non-uniform cooling condition is difficult. A good design of cooling channels plus optimized process conditions could provide uniform mold temperature distribution so that molded lenses in good qualities would be possible. Then, the profile deviation of lenses could be further compensated by profile geometry corrections. In conclusion, post-compression molding process could make birefringence-free plastic lenses with good form accuracy.
- (220.0220) Optical design and fabrication : Optical design and fabrication
- (220.1000) Optical design and fabrication : Aberration compensation
- (220.3630) Optical design and fabrication : Lenses
- (260.1440) Physical optics : Birefringence
(GT) Composition Optimization of Scintillating Rare-Earth Nanocrystals in Oxide Glass-Ceramics for Radiation Spectroscopy
- received 01/24/2014; accepted 03/05/2014; posted 03/13/2014; Doc. ID 205261
- [full text: PDF (1723) KB)]
- Abstract: Glass-ceramic nanocomposites comprising GdBr3/CeBr3 loaded sodium-aluminosilicate glasses in which scintillating crystallites are precipitated in-situ from a host glass matrix were studied. This materials system shows promise as an alternative to single crystal scintillators, with potential to be fabricated into a wide variety of sizes, shapes, and compositions. Batch compositions containing 15-18mol% GdBr3 and 3-4mol% CeBr3 were prepared and analyzed for photoluminescent light yield. Light yield peaked with rare-earth content of 15mol% GdBr3 and 4mol% CeBr3. Preliminary ceramization studies on this composition found that the precipitated phase more closely matched a Gd2O3-CeO2 mixture rather than the GdBr3(Ce) that was targeted.
- (160.2540) Materials : Fluorescent and luminescent materials
- (350.5610) Other areas of optics : Radiation
- (160.4236) Materials : Nanomaterials
Improvement in the synchronization between the radio frequency signal and the image detector in an acousto-optic tunable filter imaging spectrometer
- received 02/04/2014; accepted 03/04/2014; posted 03/04/2014; Doc. ID 205971
- [full text: PDF (955) KB)]
- Abstract: An improved synchronization between the radio frequency (RF) signal and the image detector in an acousto-optic tunable filter (AOTF) imaging spectrometer was proposed to optimize the power consumption and eliminate the image smear. The RF signal was controlled on and off alternatively to match the exposure of the image sensor. It reduced the RF power and rejected the light illumination on the image sensor in the interval of charge transfer. An experiment using a visible AOTF, a frame transfer charge-coupled device (CCD) camera and an incandescent lamp was conducted for demonstration. The average RF power decreased 7.6% and the image smear was eliminated.
- (040.1520) Detectors : CCD, charge-coupled device
- (230.1040) Optical devices : Acousto-optical devices
- (300.6190) Spectroscopy : Spectrometers
- (110.4234) Imaging systems : Multispectral and hyperspectral imaging
Validity of scalar diffraction theory and effective medium theory for analysis of a blazed grating microstructure at oblique incidence
- received 12/23/2013; accepted 03/03/2014; posted 03/05/2014; Doc. ID 203619
- [full text: PDF (589) KB)]
- Abstract: The range of the accuracy of scalar diffraction theory (SDT) and effective medium theory (EMT) for analyzing a blazed grating is quantitatively demonstrated by making a comparison of diffraction efficiencies calculated by the two simplified methods to exact results from Fourier modal method (FMM). It is found that, in our study, when the normalized period is more than fivefold wavelength of incident light at normal incidence and is more than about tenfold wavelength at larger incident angle, the SDT can be used to easily analyze effectively the transmittance characteristics of a blazed grating with the divergence less than 1%. Particularly, for zero order diffraction when the groove depth is less than threefold wavelength, the transmittance of the grating calculated by SDT with the refractive index 1.5 and the normalized period 5.0 agrees well with that of the FMM at normal incidence. But, for orders the validity of SDT is degraded than that for zero order. Generally, the deviation of the transmittances between the SDT and the FMM increases as the incident angle and refractive index augment. Furthermore, when the higher diffraction orders other than zero order are not to propagate, the EMT is valid to evaluate the transmittance of a blazed grating at normal incidence. Similarly, the error of the transmittances between the EMT and the FMM increases with the increase of the incident angle and refractive index. The effectiveness of the SDT and the EMT for analyzing a blazed grating in the range of the normalized period far more than and less than wavelength of incident light, respectively, is dependent on the parameters including the incident angle, refractive index, the normalized period and the normalized groove depth.
- (050.0050) Diffraction and gratings : Diffraction and gratings
- (050.1380) Diffraction and gratings : Binary optics
- (050.1960) Diffraction and gratings : Diffraction theory
- (050.2065) Diffraction and gratings : Effective medium theory
- (050.6624) Diffraction and gratings : Subwavelength structures
(ISA) Computationally efficient video restoration for Nyquist sampled imaging sensors combining an affine-motion based temporal Kalman filter and adaptive Wiener filter
- received 12/09/2013; accepted 03/03/2014; posted 03/07/2014; Doc. ID 202515
- [full text: PDF (3251) KB)]
- Abstract: In this paper we present a computationally efficient video restoration algorithm to address both blur and noise for a Nyquist sampled imaging system. The proposed method utilizes a temporal Kalman filter followed by a correlation-model based spatial adaptive wiener filter (AWF). The Kalman filter employs an affine background motion model and novel process-noise variance estimate. We also propose and demonstrate a new multi-delay temporal Kalman filter designed to more robustly treat local motion. The AWF is a spatial operation that performs deconvolution and adapts to the spatially-varying residual noise left in the Kalman filter stage. In image areas where the temporal Kalman filter is able to provide significant noise reduction, the AWF can be aggressive in its deconvolution. In other areas, where less noise reduction is achieved with the Kalman filter, the AWF balances the deconvolution with spatial noise reduction. In this way, the Kalman filter and AWF work together effectively, but without the computational burden of full joint spatio-temporal processing. We also propose a novel hybrid system that combines a temporal Kalman filter and BM3D processing. To illustrate the efficacy of the proposed methods, we test the algorithms on both simulated imagery and video collected with a visible camera.
- (100.1830) Image processing : Deconvolution
- (100.2000) Image processing : Digital image processing
- (100.3020) Image processing : Image reconstruction-restoration
A New Class of Resonator for Slab Waveguide Lasers
- received 12/18/2013; accepted 03/01/2014; posted 03/07/2014; Doc. ID 203097
- [full text: PDF (840) KB)]
- Abstract: We describe a new class of laser resonator, incorporating a feedback collimator, that provides feedback that is mode-matched onto a higher-order lateral mode of a slab waveguide laser. In addition, this same resonator, in outcoupling, converts the stabilized higher-order lateral mode into an essentially laterally collimated output beam with a width that exceeds twice the width of the laser-active region. This output beam should have excellent beam quality. Here, we develop the feedback collimator resonator design principles and describe both refractive and reflective versions. Finally, we compare the efficiencies and thresholds of a feedback collimator resonator and an angled-ridge resonator applied to a broad-ridge quantum cascade laser.
- (140.3410) Lasers and laser optics : Laser resonators
- (140.5960) Lasers and laser optics : Semiconductor lasers
- (230.7400) Optical devices : Waveguides, slab
- (140.5965) Lasers and laser optics : Semiconductor lasers, quantum cascade
Optical activities of large area SU8 micro-spirals fabricated by multi-beam holographic lithography
- received 11/18/2013; accepted 03/01/2014; posted 03/05/2014; Doc. ID 201321
- [full text: PDF (5452) KB)]
- Abstract: We report on the fabrication of large area micro-spirals in SU8 photoresist using a 6+1 beam holographic lithography (HL) technique involving the interference of six linearly polarized side beams and one circularly polarized central beam. In contrast to common photoresist-substrate (glass) configuration, the spirals are fabricated on substrate with a pre-cured thin SU8 photoresist. This SU8-SU8-glass configuration strengthens the attachment of the spirals to the substrate, and hence enhances the quality of the fabricated spirals. The fabricated SU8 mirco-spirals exhibit large optical activities with a polarization rotation close to 10 degrees and a circular dichroism of about 0.5 in the visible range. Our pre-cured substrate method could lift the limitations of the HL method in fabricating large and uniform micro- or nano-structures.
- (090.0090) Holography : Holography
- (350.0350) Other areas of optics : Other areas of optics
- (160.1585) Materials : Chiral media
- (160.5293) Materials : Photonic bandgap materials
Wafer based aberration metrology for lithographic systems using overlay measurements on targets imaged from phase-shift gratings
- received 01/10/2014; accepted 03/01/2014; posted 03/10/2014; Doc. ID 204555
- [full text: PDF (1377) KB)]
- Abstract: In this paper a new methodology is presented to derive the aberration state of a lithographic projection system from wafer metrology data. For this, new types of phase-shift gratings (PSG) are introduced, with special features that give rise to a simple linear relation between the PSG image displacement and the phase aberration function of the imaging system. By using the PSGs as the top-grating in a diffraction based overlay (DBO) stack, their displacement can be measured as an overlay error using a standard wafer metrology tool. In this way, the overlay error can be used as a measurand based on which the phase aberration function in the exit pupil of the lithographic system can be reconstructed. In practice, the overlay error is measured for a set of different PSG targets after which this information serves as input to a least-squares optimization problem that, upon solving, provides estimates for the Zernike coefficients describing the aberration state of the lithographic system. In addition to a detailed method description, this paper also deals with the additional complications that arise when the method is implemented experimentally and this leads to a number of model refinements and a required calibration step. Finally, the overall performance of the method is assessed through a number of experiments in which the aberration state of the lithographic system is intentionally de-tuned and subsequently estimated by the new method. These experiments show a remarkably good agreement, with an error smaller than 5mλ, between the requested aberrations, the aberrations measured by the on-tool aberration sensor and the results of the new wafer-based method.
- (050.0050) Diffraction and gratings : Diffraction and gratings
- (050.5080) Diffraction and gratings : Phase shift
- (120.0120) Instrumentation, measurement, and metrology : Instrumentation, measurement, and metrology
- (120.5050) Instrumentation, measurement, and metrology : Phase measurement
- (220.1010) Optical design and fabrication : Aberrations (global)
- (220.3740) Optical design and fabrication : Lithography
Frequency switched narrow linewidth microwave signal photonic generation based on a double-Brillouin-frequency spaced fiber laser
- received 12/19/2013; accepted 02/28/2014; posted 03/07/2014; Doc. ID 202963
- [full text: PDF (499) KB)]
- Abstract: A simple photonic approach to generate frequency switched microwave signal is proposed and experimentally demonstrated. In this scheme, a Brillouin fiber laser (BFL) with double-Brillouin-frequency spacing is used. The Brillouin ring configuration suppresses incoming Brillouin pump and even-order Stokes signals in the cavity. In addition, it also allows propagation of the odd-order Brillouin Stokes signals from configuration to output coupler. A dual-wavelength optical signal is heterodyned at the high-speed photo detector (PD) to produce a microwave signal. Frequency switched microwave signals, at 10.75GHz and 21.39 GHz respectively, can be obtained through adjusting polarization controller (PC) and loss of the variable optical attenuator (VOA). The experimental results show that the microwave signal exhibits high stability on frequency. The tunable frequency microwave signals can be further obtained by using a temperature controller and a tunable pump laser.
- (140.3510) Lasers and laser optics : Lasers, fiber
- (190.4370) Nonlinear optics : Nonlinear optics, fibers
- (190.5890) Nonlinear optics : Scattering, stimulated
Flat-top picosecond pulses generated by chirped spectral modulation from a high stability regenerative amplifier for pumping few-cycle OPCPA
- received 01/21/2014; accepted 02/28/2014; posted 03/04/2014; Doc. ID 204870
- [full text: PDF (720) KB)]
- Abstract: In this paper we present an optically synchronised regenerative amplifier able to produce flat-top temporal profile pulses for efficient pumping of a few-cycle optical parametric chirped pulse amplifier (OPCPA) system. We report on a comparative study of two methods for generating flat-top pump pulses using either controlled chirp and spectral shaping of the spectrum of the pulses seeding a regenerative amplifier or by intracavity spectral filtering. We show that gain narrowing and B-integral can be minimised in the cascaded nonlinear processes of the parametric amplifiers.
- (140.0140) Lasers and laser optics : Lasers and laser optics
- (140.3280) Lasers and laser optics : Laser amplifiers
- (140.3580) Lasers and laser optics : Lasers, solid-state
- (140.4480) Lasers and laser optics : Optical amplifiers
- (140.3518) Lasers and laser optics : Lasers, frequency modulated
Achieving high levels of color uniformity and optical efficiency for a wedge-shaped waveguide head-mounted display using a photopolymer
- received 01/16/2014; accepted 02/28/2014; posted 02/28/2014; Doc. ID 204879
- [full text: PDF (1123) KB)]
- Abstract: We developed a head-mounted display that achieved high levels of color uniformity and optical efficiency. The full-color holographic volume grating attached on the specially designed wedge-shaped waveguide head-mounted display system provided a 17° horizontal field of view. Theoretical analyses showed that the proposed waveguide resolved the problems of thickness and limited field of view. In this system, the holographic volume grating was recorded using a special sequential recording process on single photopolymer unit with 633 nm, 532 nm, and 473 nm wavelengths. The results confirm that the designed and fabricated waveguide can be employed in future commercial head-mounted displays.
- (090.2820) Holography : Heads-up displays
- (090.7330) Holography : Volume gratings
- (160.5470) Materials : Polymers
Coherent chirped pulse laser network in Mickelson phase conjugating configuration.
- received 12/06/2013; accepted 02/28/2014; posted 02/28/2014; Doc. ID 202702
- [full text: PDF (1162) KB)]
- Abstract: The mechanisms of nonlinear phase-locking of a large fiber amplifier array are analyzed. It is shown that Michelson phase conjugating configuration with double passage through array of fiber amplifiers have the definite advantages compared to one-way fiber array coupled in a Mach-Zehnder configuration. Regardless to amount of synchronized fiber amplifiers Michelson phase-conjugating interferometer is expected to do a perfect compensation of the phase-piston errors and collimation of backwardly amplified fiber beams on entrance/output beamsplitter. In both configurations the nonlinear transformation of the stretched pulse envelope due to gain saturation is capable to randomize the position of chirp inside envelope thus it may reduce the visibility of interference pattern at output beamsplitter. A certain advantages are inherent to the $sech$-form temporal envelope because of exponential precursor and self-similar propagation in gain medium. The Gaussian envelope is significantly compressed in a deep gain saturation regime and frequency chirp position inside pulse envelope is more deformed.
- (030.6140) Coherence and statistical optics : Speckle
- (060.2320) Fiber optics and optical communications : Fiber optics amplifiers and oscillators
- (140.3280) Lasers and laser optics : Laser amplifiers
- (190.5040) Nonlinear optics : Phase conjugation
- (320.1590) Ultrafast optics : Chirping
- (140.3298) Lasers and laser optics : Laser beam combining
A set of Sellmeier equations for GaS and GaSe and its applications to the nonlinear optics in GaSxSe1-x
- received 12/03/2013; accepted 02/27/2014; posted 02/28/2014; Doc. ID 202041
- [full text: PDF (365) KB)]
- Abstract: This paper reports a new set of Sellmeier equations for GaS and GaSe that provide excellent reproduction of the phase-matching conditions for second to sixth-harmonic generation of CO2 laser radiation at 10.5910 μm in GaS0.4Se0.6 at 20 ºC. In addition, this set of Sellmeier equations is found to reproduce well the phase-matching angles for second-harmonic generation of a Ti:Al2O3 laser-pumped BaB2O4 optical parametric generator at 2.14-2.9 μm and CO2 laser radiation at 9.2 (9.2007)-10.7(10.6746) μm measured by Kang et al. [Appl. Phys. B. 108, 545 (2012)] in GaS0.09Se0.91 and GaS0.41Se0.59.
- (160.4330) Materials : Nonlinear optical materials
- (190.0190) Nonlinear optics : Nonlinear optics
- (190.2620) Nonlinear optics : Harmonic generation and mixing
On the Optical Role of Randomness for Structured Surfaces
- received 01/02/2014; accepted 02/26/2014; posted 03/05/2014; Doc. ID 198272
- [full text: PDF (1306) KB)]
- Abstract: It has been known for years how random height variations of a repeated nano-scale structure can give rise to smooth angular color variations instead of the well-known diffraction pattern experienced if no randomization is present. However, until now there has not been published any papers giving an in-depth mathematical explanation on the mechanisms behind and how to design the randomness for a given application. This paper presents a mathematical framework for analyzing these random variations -- rigorously as well as intuitively.
- (030.1670) Coherence and statistical optics : Coherent optical effects
- (050.1960) Diffraction and gratings : Diffraction theory
- (240.6700) Optics at surfaces : Surfaces
- (330.1690) Vision, color, and visual optics : Color
- (290.5825) Scattering : Scattering theory
- (330.7326) Vision, color, and visual optics : Visual optics, modeling
Plasmonic metal-dielectric-metal stack structure with subwavelength metallic gratings for improving sensor sensitivity and signal quality
- received 12/13/2013; accepted 02/26/2014; posted 02/28/2014; Doc. ID 202989
- [full text: PDF (1248) KB)]
- Abstract: In this study, we investigated the performance improvement of a localized surface plasmon resonance (LSPR) biosensor by incorporating metal-dielectric-metal (MDM) stack structure and subwavelength metallic nanograting. The numerical results showed that the LSPR substrate with a MDM stack can provide not only a better sensitivity by more than 5 times but also a notably improved signal quality. While the gold nanogratings on a gold film leads to a broad and shallow reflectance curve inevitably, the presence of MDM stack can prevent propagating surface plasmons from being interfered by locally enhanced fields excited at the gold nanogratings, finally resulting in a strong and deep absorption band at resonance. Therefore, the proposed LSPR structure could potentially open a new possibility of the enhanced detection for monitoring biomolecular interactions of very low molecular weights.
- (240.6680) Optics at surfaces : Surface plasmons
- (310.0310) Thin films : Thin films
- (280.1415) Remote sensing and sensors : Biological sensing and sensors
A Loop-locked CPT Magnetometer Based on a Fiber Electro-Optic Modulator
- received 12/18/2013; accepted 02/26/2014; posted 02/28/2014; Doc. ID 203128
- [full text: PDF (486) KB)]
- Abstract: We have set up a CPT (Coherent Population Trapping) based magnetometer prototype with the D1 line of 87Rb atoms. The dichromatic light field is derived from a fiber electro-optic modulator (FEOM) connected to an external cavity laser diode (ECLD). A CPT resonance signal with 516 Hz linewidth is observed. By feeding back the derivative of the resonance curve to the FEOM with a PI controller, of which the voltage output is directly converted to the measured magnetic field intensity, the resonance peak is locked to the environmental magnetic field. The measurement data we have achieved is well matched with the data measured by a commercial fluxgate magnetometer within 2nT and the sensitivity is better than 8 pT/sqrt(Hz).
- (020.0020) Atomic and molecular physics : Atomic and molecular physics
- (020.1670) Atomic and molecular physics : Coherent optical effects
- (040.0040) Detectors : Detectors
- (120.4640) Instrumentation, measurement, and metrology : Optical instruments
- (230.2090) Optical devices : Electro-optical devices
Optical roughness BRDF model for Reverse Monte Carlo simulation of real material thermal radiation transfer
- received 12/18/2013; accepted 02/26/2014; posted 02/28/2014; Doc. ID 203345
- [full text: PDF (1059) KB)]
- Abstract: Optical roughness was introduced into the bi-directional reflectance distribution function (BRDF) model to simulate the reflectance characteristics of thermal radiation. The optical roughness BRDF model stemmed from the influence of mechanical roughness and wavelength on the ray reflectance calculation. This model was adopted to simulate real metal emissivity. The reverse Monte Carlo method was used to display the distribution of reflectance rays. The numerical simulations showed that the optical roughness BRDF model can calculate the wavelength effect on emissivity and simulate the real metal emissivity variance with incidence angles.
- (120.5700) Instrumentation, measurement, and metrology : Reflection
- (240.5770) Optics at surfaces : Roughness
- (290.1483) Scattering : BSDF, BRDF, and BTDF