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Ng B.,Imperial College London | Ng B.,Data Storage Institute Singapore | Wu J.,National University of Singapore | Hanham S.M.,Imperial College London | And 6 more authors.
Advanced Optical Materials | Year: 2013

Spoof plasmon surfaces consisting of linear arrays of subwavelength grooves are proposed as a novel platform for THz sensing. The tightly confined spoof plasmons, coupled via an Otto prism setup, are sensitive to the refractive index of the dielectric filling the grooves. Phase jumps at spoof plasmon resonances are used as a readout response for refractive index sensing. An overall sensitivity of 0.49 THz RIU-1 with figures-of-merit as high as 49 are achieved. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Shan Y.,National Metrology Center | Clnia S.W.,National Metrology Center | Yan Y.K.,Standards and Calibration Laboratoiy SCL
CPEM Digest (Conference on Precision Electromagnetic Measurements) | Year: 2010

This paper describes the continuous development of NMC's microwave power sensor calibration system using the direct comparison transfer method. The system uncertainties are evaluated for the complex reflection coefficient inputs in terms of real and imaginary components and its magnitude and phase format following the internationally recommended guidelines. Monte Carlo method is also used to numerically check the distribution of the output quantities. The measurement results and the uncertainties in different methods are presented and discussed. ©2010 IEEE.


Xiao Z.,Nanyang Technological University | Xiao Z.,Institute of Microelectronics, Singapore | Luan F.,Nanyang Technological University | Liow T.-Y.,Institute of Microelectronics, Singapore | And 2 more authors.
Optics Letters | Year: 2012

In this Letter, we propose general optimization methods to design broadband high-efficiency grating couplers for planar waveguides. We attribute the coupling bandwidth to the mismatch of effective indices between the diffracted beam and the actual grating structure around the operation wavelength for fiber to waveguide excitation. The coupling bandwidth formula is deduced. A simple parameter-separate optimization procedure is proposed for general layered grating couplers for high coupling efficiency. Using our principle, we optimized a grating coupler for a horizontal slot waveguide operating at wavelength 1.55 μm for TM polarization. The grating coupler has 1 dB bandwidth of 60 nm and coupling efficiency of 65% with incident light from single-mode optical fiber (SMF) at 8°. © 2012 Optical Society of America.


Song J.H.,Institute of Microelectronics, Singapore | Zhang J.,Institute of Microelectronics, Singapore | Zhang J.,National Metrology Center | Zhang H.,Institute of Microelectronics, Singapore | And 2 more authors.
Optics Express | Year: 2011

We report a fully packaged silicon passive waveguide device designed for a tunable filter based on a ring-resonator. Polarization diversity circuits prevent polarization dependant issues in the silicon ring-resonator. For the device packaging, the YAG laser welding technique has been used for pigtailing both of the input and output fibers. Post welding misalignment was compensated by mechanical fine tuning using the seesaw effect via power monitoring. Packaging loss less than 1.5dB with respect to chip measurement has been achieved using 10 μm-curvature radius lensed fibers. In addition, the packaging process and the module performance are presented. © 2011 Optical Society of America.


Xiao Z.,Nanyang Technological University | Xiao Z.,Institute of Microelectronics, Singapore | Liow T.-Y.,Institute of Microelectronics, Singapore | Zhang J.,National Metrology Center | And 2 more authors.
Optics Express | Year: 2013

The bandwidth of planar waveguide grating couplers is theoretically investigated based on the rigorous grating theory. We observe that the bandwidth behavior is not only determined by the grating coupler intrinsic properties, but also affected by the fiber parameters such as position, beam waist and Numerical Aperture. The rigorous bandwidth formula is derived. By analyzing the formula, several practical guidelines are proposed for grating coupler design and fiber operation in order to achieve wideband performance. ©2012 Optical Society of America.


Wu T.Y.,National Metrology Center | Lu Y.L.,Nanyang Technological University
Measurement: Journal of the International Measurement Confederation | Year: 2015

Error analysis and uncertainty estimation for a millimeter-wave phase-shift measurement system at 325 GHz are presented. The measurement errors due to inductive voltage divider, receiver noise, phase drift, mismatch at test ports, gauge-block attenuator, leakage and repeatability have been identified and evaluated. The standard uncertainty of these error components have been estimated and combined to obtain the expanded uncertainty in phase-shift measurement. The differential phase-shift measurement uncertainty for a 0-60 dB WR-03 rotary vane attenuator is estimated to be 0.57-1.3° at 325 GHz. © 2014 Elsevier Ltd. All rights reserved.


Wu T.Y.,National Metrology Center
Electronics Letters | Year: 2012

A 220-325GHz millimetre-wave phase-shift measurement system is described. The differential phase-shift measurement uncertainty is estimated to be 0.58°-1.32° for a 0-60dB rotary vane attenuator (RVA) at 325GHz. The phase-shift of a WR-03 waveguide shim is measured as a line standard to verify the system. Measurement results of a WR-03 RVA are also presented. © 2012 The Institution of Engineering and Technology.


Wu T.Y.,National Metrology Center
Measurement: Journal of the International Measurement Confederation | Year: 2012

A dual-channel millimeter-wave attenuation measurement system from 75 GHz to 110 GHz using a heterodyne receiver is described. The millimeter-wave attenuation is derived from the voltage ratio at 5.02 kHz using an inductive voltage divider as a reference standard. The measurement uncertainties are estimated to be 0.015-0.030 dB for attenuation ranging from 0 dB to 70 dB at 110 GHz. Measurement results of a waveguide rotary vane attenuator with 0-70 dB attenuation steps at 110 GHz are presented. © 2012 Elsevier Ltd. All rights reserved.


Jing T.,National Metrology Center | Sim J.,National Metrology Center
CPEM Digest (Conference on Precision Electromagnetic Measurements) | Year: 2014

The AC-DC difference of an AC-DC transfer standard varies with its input voltage and ac frequencies. Its calibration may not necessarily cover all the voltage-frequency points for their possible uses in practice. This results in situations when there is no reference value to use such a transfer standard for calibrations at some voltage-frequency points. This paper analyses the principle structure of a transfer standard, shows the possibility of interpolating points based on calibrated ones, and presents the interpolation results performed in the National Metrology Centre (NMC). © 2014 IEEE.


Xu G.,National Metrology Center | Huang X.,National Metrology Center
Energy Procedia | Year: 2012

A multi-functional differential spectral responsivity (DSR) measurement system for primary calibration of the shortcircuit current (SCC) of reference solar cells with WPVS (World Photovoltaic Scale) design [1] is reported in this paper. Based on the dual beam principle, the system is able to measure DSR at different bias levels, spatial uniformity, linearity, temperature coefficient of the spectral responsivity of reference cells in the spectral range from 280 nm to 1200 nm. The measurement principle, system design and construction as well as the performance of the system are described in this work. An uncertainty ≤ 1% for SCC measurement is confirmed by experimental results. © 2012 Published by Elsevier Ltd.

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