Abstract:In this paper we report on the design, fabrication and characterization of terahertz (THz) bi-material sensors with metamaterial absorbers. MEMS fabrication-friendly SiO x and Al are used to maximize the bimetallic effect and metamaterial absorption at 3.8 THz, the frequency of a quantum cascade laser illumination source. Sensors with different configurations were fabricated and the measured absorption is near 100% and responsivity is around 1.2 deg/μW, which agree well with finite element simulations. The results indicate the potential of using these detectors to fabricate focal plane arrays for real time THz imaging.
Metamaterial absorbers with nearly 100% absorption in the terahertz (THz) spectral band have been designed and fabricated using a periodic array of aluminum (Al) squares and an Al ground plane separated by a thin silicon dioxide (SiO2) dielectric film. The entire structure is less than 1.6 mm thick making it suitable for the fabrication of microbolometers or bi-material sensors for THz imaging. Films with different dielectric layer thicknesses exhibited resonant absorption at 4.1, 4.2, and 4.5 THz with strengths of 98%, 95%, and 88%, respectively. The measured absorption spectra are in good agreement with simulations using finite element modeling.
Abstract. To increase the sensitivity of uncooled thermal sensors in the terahertz (THz) spectral range (1 to 10 THz), we investigated thin metamaterial layers exhibiting resonant absorption in this region. These metamaterial films are comprised of periodic arrays of aluminum (Al) squares and an Al ground plane separated by a thin silicon-rich silicon oxide (SiO x ) dielectric film. These standard MEMS materials are also suitable for fabrication of bi-material and microbolometer thermal sensors. Using SiO x instead of SiO 2 reduced the residual stress of the metamaterial film. Finite element simulations were performed to establish the design criteria for very thin films with high absorption and spectral tunability. Single-band structures with varying SiO x thicknesses, square size, and periodicity were fabricated and found to absorb nearly 100% at the designed frequencies between three and eight THz. Multiband absorbing structures were fabricated with two or three distinct peaks or a single-broad absorption band. Experimental results indicate that is possible to design very efficient thin THz absorbing films to match specific applications.
We report on fabrication and characterization of arrays of bimaterial microcantilevers and discuss their performance as uncooled infrared imagers. An optical readout was used to simultaneously measure deflections of all microcantilevers in the array. The fabricated arrays had an average noise equivalent temperature difference (NETD) and a response time of 1.5K and 6ms, respectively. Some microcantilevers in the array exhibited NETD values below 500mK, approaching our theoretical prediction of 151mK. A unique and valuable feature of the implemented approach is its straightforward scalability to higher resolution arrays, without progressively growing complexity and cost.
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