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.
To explore the effect of the incident polarization on achieving polarization-controllable multifocal arrays (MFAs), the polarization-controllable MFAs generated by radially polarized (RP) and azimuthally polarized (AP) beams are compared in this work. Four phase filters for the numerical aperture (NA) of 0.80, 0.85, 0.90 and 0.95 are respectively designed to generate the polarization-controllable MFAs under the illumination of RP and AP beams. The intensity comparison demonstrates that the polarization-controllable MFAs generated by AP beams have the higher uniformity, smaller focal spots and more stable intensity distributions for the same NA. The polarization comparison demonstrates that the polarization properties of the polarization-controllable MFAs generated by AP beams are more consistent with the desired target. Therefore, the AP incident beam is the better choice to realize a polarization-controllable MFA by a phase filter.
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.
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.
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%.
Through modulating the Bessel–Gaussian radially polarized vector beam by the cosine synthesized filter under a reflection paraboloid mirror system with maximum focusing semi-angle of π/2 , arbitrary-length super-Gaussian optical needles are created with consistent beam size of 0.36λ (full width at half maximum) and the electric field being pure longitudinally polarized (polarization conversion efficiency greater than 99%). Numerical calculations show that the on-axis intensity distributions are super-Gaussian, and the peak-valley intensity fluctuations are all within 1% for 4λ , 6λ , 8λ , and 10λ long light needles. The method remarkably improves the nondiffraction beam quality, compared with the subwavelength Gaussian light needle, which is generated by a narrow-width annular paraboloid mirror. Such a light beam may suit potential applications in particle acceleration, optical trapping, and microscopy.
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.
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.
In order to study the validity of general focal length function in designing diffractive microlenses with long focal
depth, diffractive microlenses with different f-numbers are designed using general focal length function and their
focusing characteristics, such as real focal depth, real focal spot size, and diffractive efficiency, are investigated
using electromagnetic theory and boundary element method. Investigation results indicate that general focal
length function can be used to achieve long focal depth in designing diffractive microlenses, even twice over than
those of conventional diffractive microlenses with similar parameters.
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