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Wang Y.,Nanyang Technological University | Goh W.L.,Nanyang Technological University | Chai K.T.-C.,Agency for Science, Technology and Research Singapore | Mu X.,Chongqing University | And 3 more authors.
Review of Scientific Instruments | Year: 2016

The parasitic effects from electromechanical resonance, coupling, and substrate losses were collected to derive a new two-port equivalent-circuit model for Lamb wave resonators, especially for those fabricated on silicon technology. The proposed model is a hybrid π-type Butterworth-Van Dyke (PiBVD) model that accounts for the above mentioned parasitic effects which are commonly observed in Lamb-wave resonators. It is a combination of interdigital capacitor of both plate capacitance and fringe capacitance, interdigital resistance, Ohmic losses in substrate, and the acoustic motional behavior of typical Modified Butterworth-Van Dyke (MBVD) model. In the case studies presented in this paper using two-port Y-parameters, the PiBVD model fitted significantly better than the typical MBVD model, strengthening the capability on characterizing both magnitude and phase of either Y11 or Y21. The accurate modelling on two-port Y-parameters makes the PiBVD model beneficial in the characterization of Lamb-wave resonators, providing accurate simulation to Lamb-wave resonators and oscillators. © 2016 Author(s).

Ho C.P.,National University of Singapore | Pitchappa P.,National University of Singapore | Lin Y.-S.,National University of Singapore | Huang C.-Y.,Tunghai University | And 2 more authors.
Applied Physics Letters | Year: 2014

We present the design, simulation, fabrication, and characterization of a continuously tunable Omega-ring terahertz metamaterial. The tunability of metamaterial is obtained by integrating microactuators into the metamaterial unit cell. Electrothermal actuation mechanism is used to provide higher tuning range, larger stroke, and enhanced repeatability. The maximum achieved tuning range for the resonant frequency is around 0.30 THz for the input power of 500mW. This shows the potential of using electrothermally actuated microactuators based tunable metamaterial design for application such as filters, absorbers, sensors, and spectral imagers. © 2014 AIP Publishing LLC.

Ho C.P.,National University of Singapore | Ho C.P.,Institute of Microelectronics, Singapore | Pitchappa P.,National University of Singapore | Pitchappa P.,Institute of Microelectronics, Singapore | And 5 more authors.
Optics Letters | Year: 2015

We demonstrate the design, fabrication, and characterization of a polycrystalline-silicon-based photonic crystal Fabry- Perot etalon, which is aimed to work in the mid-infrared wavelengths. The highly reflective mirrors required in a Fabry-Perot etalon are realized by freestanding polycrystalline- silicon-based photonic crystal membranes with etched circular air holes. A peak reflection of 96.4% is observed at 3.60 μm. We propose a monolithic CMOS-compatible fabrication process to configure two such photonic crystal mirrors to be in parallel to form a Fabry-Perot etalon; a filtered transmission centered at 3.51 μm is observed. The quality factor measured is around 300, which is significantly higher than in existing works. This creates the possibility of using such devices for high-resolution applications such as gas sensing and hyperspectral imaging. © 2015 Optical Society of America.

Zhou H.,National University of Singapore | Kropelnicki P.,Excelitas Technologies | Lee C.,National University of Singapore
Nanoscale | Year: 2015

Although significantly reducing the thermal conductivity of silicon nanowires has been reported, it remains a challenge to integrate silicon nanowires with structure materials and electrodes in the complementary metal-oxide-semiconductor (CMOS) process. In this paper, we investigated the thermal conductivity of nanometer-thick polycrystalline silicon (poly-Si) theoretically and experimentally. By leveraging the phonon-boundary scattering, the thermal conductivity of 52 nm thick poly-Si was measured as low as around 12 W mK-1 which is only about 10% of the value of bulk single crystalline silicon. The ZT of n-doped and p-doped 52 nm thick poly-Si was measured as 0.067 and 0.024, respectively, while most previously reported data had values of about 0.02 and 0.01 for a poly-Si layer with a thickness of 0.5 μm and above. Thermopile infrared sensors comprising 128 pairs of thermocouples made of either n-doped or p-doped nanometer-thick poly-Si strips in a series connected by an aluminium (Al) metal interconnect layer are fabricated using microelectromechanical system (MEMS) technology. The measured vacuum specific detectivity (D∗) of the n-doped and p-doped thermopile infrared (IR) sensors are 3.00 × 108 and 1.83 × 108 cm Hz1/2 W-1 for sensors of 52 nm thick poly-Si, and 5.75 × 107 and 3.95 × 107 cm Hz1/2 W-1 for sensors of 300 nm thick poly-Si, respectively. The outstanding thermoelectric properties indicate our approach is promising for diverse applications using ultrathin poly-Si technology. This journal is © The Royal Society of Chemistry.

Excelitas Technologies | Date: 2016-07-02

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