Fabrication Of Frequency Selective Surface Research Articles

Design and fabrication of sub-terahertz filter using maskless femto second laser micromachining process

Anovel mask lessand rapid fabrication of frequency selective surface on the low-cost Copper/Polyimide substrate for sub-terahertz filter applications is discussed in this paper.The geometry of the unit cell is in hexagonal geometry with rectangular strips on its sides.The proposed frequency selective surface exhibits minimum reflection (S11) characteristics at 106.75 GHz. Parametric studies on the width of rectangular strip (W), periodicity of the unit cell (P), angle of incidence (θ) and thickness of copper layer (Ct)are conducted to demonstrate its effect on the transmission and reflection characteristics of the filter.A prototype of the proposed frequency selective surface is fabricated using femto second laser micromachining processand tested using Terahertz frequency domain spectroscopysystem. Measured and simulated results are compared where an agreeable correspondence is observed.

Fabrication of frequency-selective surface by picosecond laser direct writing

In this paper, a terahertz (THz) frequency-selective surface (FSS) is fabricated through picosecond (ps) laser direct writing on the silicon-based silver film. The time-domain spectroscopy (TDS) technique is used to test its electromagnetic modulation performance. Based on the finite-difference time-domain method, CST microwave studio 2016 was used to simulate its resonance characteristic. By optimizing the process parameters, the square ring structures on the FSS with the size error below 2% are fabricated. It is found that the center frequencies of the experimental and simulated resonance peaks are nearly both at 0.293 THz, and the transmission is about 0.01%. From the simulation results, when the size error is controlled below 2 μm, the resonant frequency shift is about 2.2 GHz. Combining the simulation and experimental results, if the size error of inner square is controlled below 2%, it has little effect on the THz metasurfaces’ modulation performance. By optimizing the laser scanning strategy and processing parameters, ps laser direct writing provides a new choice for the convenient fabrication of THz metamaterials.

Frequency selective surfaces design for a dual‐channel quasi‐optical system

ABSTRACTWith the renewed applications of millimeter wave technologies in remote sensing, radio astronomy, and quasi‐optical (QO) systems have been widely used in various radiometer systems. Frequency selective surface (FSS) is one of the key components in a QO system, functioning as frequency separation. For a practical FSS component, small insertion loss and narrow transition band from pass band to stop band are preferred to maintain signal level and reject out‐of‐band noise, respectively. In addition, the bandwidth is also a concerned parameter. In this article, perforated array is used for the design and fabrication of FSS for a dual‐channel QO system. The agreement between measurement and simulation is satisfactory. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2365–2369, 2014

THz Frequency Selective Surface Filters for Earth Observation Remote Sensing Instruments

The purpose of this paper is to review recent developments in the design and fabrication of Frequency Selective Surfaces (FSS) which operate above 300 GHz. These structures act as free space electromagnetic filters and as such provide passive remote sensing instruments with multispectral capability by separating the scene radiation into separate frequency channels. Significant advances in computational electromagnetics, precision micromachining technology and metrology have been employed to create state of the art FSS which enable high sensitivity receivers to detect weak molecular emissions at THz wavelengths. This new class of quasi-optical filter exhibits an insertion loss <;0.3 dB at 700 GHz and can be designed to operate independently of the polarization of the incident signals at oblique incidence. The paper concludes with a brief overview of two major technical advances which will greatly extend the potential applications of THz FSS.

Fabrication of frequency-selective surfaces using microlens projection photolithography

This letter describes the use of microlens projection photolithography (μLPL) for the fabrication of repetitive metallic micropatterns, and the application of these patterns as frequency-selective surfaces. Microlens projection photolithography uses an array of microlenses (diameter d=1–1000 micrometers) to project an array of images of an illuminated mask into photoresist. We converted these arrays into patterns in metals by electron beam evaporation and lift off. This technique can produce arrays over areas &amp;gt;10 cm2 with submicrometer feature sizes in a single exposure. We fabricated arrays of metallic micropatterns on substrates transparent to infrared radiation, and demonstrated that appropriate patterns acted as frequency-selective filters.

Analysis of scattering from frequency-selective surfaces in the infrared

A comparative theoretical and experimental analysis of scattering from a doubly periodic dielectric-mounted frequency-selective surface (FSS) in the mid-infrared (4–12 μm) is presented. The theoretical analysis involves the solution of an electric-field integral equation relating the induced current on the FSS in the presence of the dielectric mounting to the incident excitation field. The Green’s function in the presence of the dielectric layers is derived by using a simple spectral-domain technique. In modeling the FSS, the structure is assumed to be infinitesimally thin and is described by complex sheet resistance. Fabrication of FSS’s for use in the mid-infrared is possible by using photolithographic techniques. Experimental and theoretical results are presented for metallic (aluminum) rectangular patch arrays fabricated by reactive ion etching and lift-off processing, respectively, and a resistive (bismuth) patch array fabricated by lift-off processing. These structures exhibit a spectral band-stop characteristic in transmittance.