Here, the disparity in metal surface roughness and its impact on loss is investigated for the integrated interconnection of optoelectronic devices fabricated by wafer-level multilayer metal-air-dielectric additive-manufacturing technology. The metal surface roughness and its influence on integrated interconnect transmission loss was analyzed. According to the different contact materials and post-treatment technique, a variety of metal surface models were established. The metal surface roughness of the fabricated samples was measured, and the influence of the micro-machining process was verified. Meanwhile, micro-coaxial transmission lines are employed as the research object to validate the mechanism of surface roughness affecting transmission loss. The measured results of the transmission line samples are well consistent with the finite element simulation results by considering the actual metal roughness.
Traditional infrared lenses cannot meet the requirements of planarization and lightweight of infrared optical systems due to their large volume and mass. An infrared metasurface with almost zero thickness can control the incident beam’s amplitude, phase and polarization arbitrarily, which make it possible to circumvent these limitations. However, no metasurface has been designed to realize sub-diffraction focusing in the long-wave infrared band. In this article, a longwave infrared meta spiral zone plate (LWIR-MSZP) is designed, which converts the incident linearly polarized beam to an azimuthally polarized beam and focuses the latter into a sub-diffraction solid spot. The designed LWIR-MSZP works at a wavelength of 10.6 μm and has a diameter of 480 μm and numerical aperture (NA) of 0.8. The simulated full width at half maximum (FWHM) and depth of focus (DOF) of the focal spot are 0.6λ and 2.24λ, respectively. The simulated efficiency is 24.04%. The proposed design procedure greatly simplifies the long-wave infrared sub-diffractive focusing optical system and complements the technical gap to achieve sub-diffractive focusing in long-wave infrared using a metasurface. To make it further, the all-silicon meta-atom employed in this work has the advantage of low cost once semiconductor fabrication techniques are introduced. We believe that this result can be applied to the related fields of super-resolution imaging and laser processing in long-wave infrared band.
Orbital angular momentum (OAM) of an optical vortex has attracted great interest from the scientific community due to its significant values in high-capacity optical communications such as mode or wavelength division multiplexer/demultiplexer. Although several configurations have been developed to demultiplex an optical vortex, the multiwavelength high-order optical vortex (HOOV) demultiplexer remains elusive due to lack of effective control technologies. In this study, we present the design, fabrication, and test of metasurface optical elements for multiwavelength HOOV demultiplexing based on optical gyrator transformation transformations in the visible light range. Its realization in a metasurface form enables the combined measurement of OAM, the radial index p, and wavelength using a single optical component. Each wavelength channel HOOV can be independently converted to a high-order Hermitian–Gaussian beam mode, and each of the OAM beams is demultiplexed at the converter output. Furthermore, we extend the scheme to realize encoding of the three-digit gray code by controlling the wavelength or polarization state. Experimental results obtained at three wavelengths in the visible band exhibit good agreement with the numerical modeling. With the merits of ultracompact device size, simple optical configuration, and HOOV recognition ability, our approach may provide great potential applications in photonic integrated devices and systems for high-capacity and demultiplex-channel OAM communication.
A novel two-dimensional reflective grating encoder is introduced. The optical encoder is developed by a binary amplitude reflective scale grating and a two-dimensional slit displacement sensor, which is fabricated by MEMS technology. Based on Talbot effort, the proposed method can achieve millimetric measurement with high accuracy, where the displacement difference within 0.1% and 0.2% for 1 mm and 20 mm measurement, respectively. By using the eight-segment data division program, the proposed method can easily distinguish 1 μm displacement measurement. Furthermore, in measurement speed tests, the proposed method can reach the movement speed about 5000 μm/s. The experimental results showed the proposed method can achieve high resolution, high speed and long-range measurement, which is potential in the industries and workshops application.
The measurement of spindle radial error motion is achieved based on target trajectory tracking (TTT). Error analysis of TTT method is performed in this paper. Target trajectory doesn’t contain information about axial error motion. The tilt error motion is included in the target trajectory. However, the tilt error motion is small enough to be ignored. The roundness error of the target trajectory is assessed to obtain the radial error motion of the spindle. The experimental results confirm that the proposed method can be applied to measure the radial error motion of a high-speed spindle having a maximum rotational speed of 6000r/m.
Head mounted displays (HMD) showed huge market potential in recent years. In these techniques, vergenceaccommodation conflict (VAC) is a fundamental problem which makes viewers feel discomfort and fatigue. To overcome this limitation, researchers proposed many solutions including Maxwellian view displays, vari-focal plane displays, multifocal plane displays, integral imaging-based displays, and computational multilayer displays. These techniques can enable correct or nearly correct focus cues, however, they failed to achieve both high image fresh rate and high lateral resolution with a compact architecture. In this paper, we propose a compact birefringent-based virtual reality (BVR) HMD with correct focus cues by spatially projecting the input images onto four depth planes. In the BVR, two stacked liquid crystal displays (LCDs) provide two axially separated input images in an additive fashion. We set a liquid crystal panel behind the LCDs to modulate the polarization of the emitting light from the LCDs pixel-wise. After that, a birefringent lens and an eyepiece project the modulated light onto four depth planes at 0D, 1D, 2D, and 3D. To minimize the astigmatism of the system, we employ a birefringent doublet with orthogonal optic axes and use an eyepiece to suppress the overall aberration. Comparing to the existing techniques, the proposed BVR mitigates the VAC problem with a compact architecture. Moreover, because there is no temporal multiplexing and lateral resolution sacrifice, the BVR can easily achieve high image refresh rate and high lateral resolution. Herein, we present the optical design of the BVR and characterize its performance in Zemax.
The convergence of recent advances in optical fabrication and digital processing yields a generation of imaging technology—light-field (LF) cameras which bridge the realms of applied mathematics, optics, and high-performance computing. Herein for the first time, we introduce the paradigm of LF imaging into laryngoscopy. The resultant probe can image the three-dimensional shape of vocal folds within a single camera exposure. Furthermore, to improve the spatial resolution, we developed an image fusion algorithm, providing a simple solution to a long-standing problem in LF imaging.
A fast and precise registration method for multi-image snapshot Fourier transform imaging spectroscopy is proposed. This method accomplishes registration of an image array using the positional relationship between homologous points in the subimages, which are obtained offline by preregistration. Through the preregistration process, the registration problem is converted to the problem of using a registration matrix to interpolate subimages. Therefore, the hardware interpolation of graphics processing unit (GPU) texture memory, which has speed advantages for its parallel computing, can be used to significantly enhance computational efficiency. Compared to a central processing unit, GPU performance showed ∼27 times acceleration in registration efficiency.
This study demonstrates an easy way to change surface characteristics, the water contact angle on styrene based shape memory polymer (SMP) surface alters before and after cracking formation and recovery. The contact angle of water on the original SMP surface is about 85 degree, after coating with Al and then kneading from side face at glass transition temperature Tg, cracking appeared both on Al film and SMP; cooling down and removing the Al film, cracks remain on SMP surface while the contact angle reduced to about 25 degree. When reheated above Tg, the cracks disappeared, and the contact angle go back to about 85 degree. The thin Al film bonded on SMP surface was coated by spurting, that constrains the deformation of SMP. Heating above Tg, there are complex interactions between soft SMP and hard metal film under kneading. The thin metal film cracked first with the considerable deformation of soft polymer, whereafter, the polymer was ripped by the metal cracks thus polymer cracked as well. Cracks on SMP can be fixed cooling down Tg, while reheated, cracks shrinking and the SMP recovers to its original smooth surface. Surface topography changed dramatically while chemical composition showed no change during the deformation and recovery cycle, as presented by SEM and EDS. Furthermore, the wetting cycle is repeatable. This facile method can be easily extended to the hydropobicity/hydrophilicity modification of other stimuli-responsive polymers and put forward many potential applications, such as microfluidic switching and molecule capture and release.
A grating encoder, which is composed of two equal periodic planar gratings, is proposed for measuring wide range three-axis displacements with nanometric resolution. In the optical reading system, one grating works as a reference planar grating, while another one is a scale planar grating. The grating encoder records the x- and y-axis displacement information in terms of the grating period, while it records the z-axis displacement information in terms of both the wavelength of the laser and the grating period. In this scheme, the gratings and other optical elements satisfy the Littrow configuration. The positions and the size of the detected interference zones are almost constant when the scale grating moves along the z-axis with respect to the optical reading system. Therefore, the measurement range is greatly enhanced in the z-axis direction. When the wavelength of the laser is 632.8 nm and the scale grating with period 8 μm is 100×100 mm2, the measured maximal z-axis displacement of the proposed encoder is 1263 mm theoretically.
Fourier-transform imaging spectrometers are rapidly developed due to their extensive use in industrial monitoring, target detection, and chemical identification. Static Fourier-transform imaging spectrometer (SFIS) containing a birefringent interferometer is one of the most popular directions due to its inherent robustness. However, the SFIS suffers from its low achievable signal-to-noise ratio (SNR) because of the restriction of incident angle. Meanwhile, in applications, the SNR is perhaps the most important factor to determine the usefulness of an instrument. In this paper, we report here a Static Fourier-transform imaging spectrometer based on differential structure (SFIS-DS) in the 400-800nm wavelength range with a high SNR. As in electronic system, the differential structure can double optical efficiency and strongly restrain common mode error in the SFIS-DS. And the differential structure described here is also available for any instruments containing a birefringent interferometer. However, the drawback of the SFIS-DS is that the two images obtained by the two differential channels need precise registration which can be overcome by a sub-pixel spatial registration algorithm. The experimental results indicate the SFIS-DS can increase the SNR by no less than 40%.
Free volume theory and a model of polymerization kinetics are introduced to predict and analyze the curing shrinkage and kinetic parameters of an acrylate-based ultraviolet-embossing resist. Curing shrinkage tests have been designed and performed to verify the accuracy of the model. The experimental results are in good agreement with the simulated results of the conversion behavior. The reaction coefficients of polymerization predicted by this model are essentially correct when compared to the classical experimental values. Moreover, the dynamic shrinkage during polymerization determined experimentally matches the simulated result predicted by our model.
Micro lens array used in parallel laser direct writing process is fabricated with UV imprinting and dry etching. Experiment results show that the relief of fabrication result is confirmed with that of original stamp. And the optical character test experiments show that the focused spot array under both writing laser and focusing test laser is similar. And the single spot profile under both writing laser and focusing test laser is also similar.
The effects of parameters of Bessel-Gaussian beam on the focusing characteristics are investigated in lens system with high numerical aperture. The maximal intensity shifts from focal spot in the case of larger value of parameters of BG beam. Meanwhile, the lateral resolution is increasing with the increase of value of parameters. The effect of parameters of Bessel-Gaussian beam on the achievement of optical needle is also explored. Obviously, the value of parameters is most important to obtain optical needle.
Hot embossing is an effective way to achieve high-quality Microstructures at low cost. At present papers, the effects of
geometry and shear on filling profile and polymer deformation have studied through experiments or computations. In
this paper, the parameters on different polymer deformation modes: single peak, dual peak and embossing stage have
researched. Especially it is referred that the mainly reasons of embossing stage phenomenon are the ratio of cavity width
to height 2w/hi, the ratio of cavity width to tool width w/(w+s), and shear thinning. In addition, the temperature variation
of polymer due to internal friction has discussed with evolution of imprint speed. And the simulation results prove a
better coincidence with experiments.
Rapidly expanding of millimeter wave communication has made Ka-band filter fabrication to gain more and more attention from the researcher. Described in this paper is a high quality UV-lithographic process for making high aspect ratio parts of a coaxial Ka band dual mode filter using an ultra-thick SU-8 photoresist layer, which has a potential application in LMDS systems. Due to the strict requirements on the perpendicular geometry of the filter parts, the microfabrication research work has been concentrated on modifying the SU-8 UV-lithographical process to improve the vertical angle of sidewalls and high aspect ratio. Based on the study of the photoactive property of ultra-thick SU-8 layers, an optimized prebake time has been found for obtaining the minimum UV absorption by SU-8. The optimization principle has been tested using a series of experiments of UV-lithography on different prebake times, and proved effective. An optimized SU-8 UV-lithographical process has been developed for the fabrication of thick layer filter structures. During the test fabrication, microstructures with aspect ratio as high as 40 have been produced in 1000 mm ultra-thick SU-8 layers using the standard UV-lithography equipment. The sidewall angles are controlled between 85~90 degrees. The high quality SU-8 structures will then be used as positive moulds for producing copper structures using electroforming process. The microfabication process presented in this paper suits the proposed filter well. It also reveals a good potential for volume production of high quality RF devices.
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