Single-mode Sensor Research Articles

Angular and polarization response of multimode sensors with resistive-grid absorbers.

High-sensitivity receiver systems with near-ideal polarization sensitivity are highly desirable for development of millimeter and submillimeter radio astronomy. Multimoded bolometers provide a unique solution to achieve such sensitivity, for which hundreds of single-mode sensors would otherwise be required. The primary concern in employing such multimoded sensors for polarimetery is the control of the polarization systematics. In this work, we examine the angular- and polarization-dependent absorption pattern of a thin resistive grid or membrane, which models an absorber used for a multimoded bolometer. The result shows that a freestanding thin resistive absorber with a surface resistivity of η/2, where η is the impedance of free space, attains a beam pattern with equal E- and H-plane responses, leading to zero cross-polarization. For a resistive-grid absorber, the condition is met when a pair of grids is positioned orthogonal to each other and both have a resistivity of η/2. When a reflective backshort termination is employed to improve absorption efficiency, the cross-polar level can be suppressed below -30 dB if acceptance angle of the sensor is limited to ≲60°. The small cross-polar systematics have even-parity patterns and do not contaminate the measurements of odd-parity polarization patterns, for which many of the recent instruments for cosmic microwave background are designed. Underlying symmetry that suppresses these cross-polar systematics is discussed in detail. The estimates and formalism provided in this work offer key tools in the design consideration of the instruments using the multimoded polarimeters.

Optimal self-referenced sensing using long- and short- range surface plasmons

Dual-mode surface-plasmon resonance (SPR) sensors use both long- and short- range surface plasmon waves to differentiate surface binding interactions from interfering bulk effects. We have optimized the design of these sensors for minimum surface limit of detection (LOD) using a Cramer-Rao lower bound for spectral shift estimation. Despite trade-offs between resonance width, minimum reflectivity, and sensitivity for the two modes, a range of reasonable design parameters provides nearly optimal performance. Experimental verification using biotin-streptavidin binding as a model system reveals that sensitivity and LOD for dual-mode sensors remains competitive with single-mode sensors while compensating for bulk effects.

Multimodal Industrial Inspection and Analysis

Diagnosis of complex engineering systems requires the use of multiple sensor sources to acquire information. In this paper we present a survey of multimodal data acquisition systems for nondestructive testing (NDT) and engineering analysis. We begin with a summary of the relative strengths and weaknesses of individual NDT modalities. Thereafter we present existing multimodal inspection hardware systems that use complementary NDT sensors. The advantages of such multimodal data acquisition over conventional single modality sensors in inspection and analysis are highlighted. Possible approaches to fuse complementary multimodal sensor data are discussed. We conclude with possible directions for the future development of multimodal inspection systems.

광기능성 폴리머 도파로형 자외선 센서의 제작 및 특성

Single-mode planar waveguide type UV sensor was fabricated using SU-8 and photochromic dye. Polymer waveguide was fabricated 10 µm width and 2 µm thickness for single-mode operation. The UV sensor had an absorbance with 0.0396~0.114 absorbance/mW respectively when the 5 mm sensing area was irradiated with UV for 3 sec. And sensor had a linear properties by sensing area variation. Proposed single-mode sensor had more excellent properties of UV sensitivity than other UV sensors.

Damage Localization on Two-Dimensional Structure Based on Wavelet Transform and Active Lamb Wave-Based Method

Damage characterization was carried out by comparing single mode sensor signals collected before and after the damage event. By subtracting the signals of both conditions from each other, a scatter signal is produced which can be used for damage localization. By using Gabor wavelet to analyze single mode Lamb wave recorded before damage and scatter signal, the difference of time-of-flight can be obtained. Combining with the ellipse technique, the localization experiment on fiberglass plate of dimension 100×100×2mm is completed.

Intrinsic single-mode fiber-optic pressure sensor

Development and calibration of a fiber-optic pressure single mode sensor are described. The sensor is based on the intrinsic properties of a communication grade single-mode optical fiber. A self-referencing double interferometer was used for interrogation of the signal. The sensing interferometer is based on a white light Michelson interferometer. The sensor was evaluated through measurement of high pressures applied to sand samples. Experimental results demonstrate the linearity of the system in the range 0 to 38.08 MPa with a resolution of 0.03 MPa.

Interferometric optical fiber dynamic mechanical sensors

The use of fiber optic interferometers for detecting dynamic mechanical parameters has matured significantly since the first reports on them appeared just about a decade ago. This paper will discuss the current state-of-the-art in this technology with particular emphasis on devices for measuring acoustic waves and dynamic structural strains. Contrasts will be discussed between two-fiber single mode sensors and the more recently developed single-fiber dual mode systems.