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Waveguide dispersion curves identification at low-frequency using two actuators and phase perturbations
摘要： Dispersion curves of fluid-filled elastic-tubes are used for non-destructive measurement of material acoustic properties. The underlying physics leads to a singular numerical procedure when several modes or long-wavelength scenarios take part in the tube dynamics. The literature describes several methods to identify dispersion curves that require a large ratio of samples per length. Described is a method to enrich the amount of available information of an otherwise ill-posed problem, by multiple boundary phase perturbations at each excitation frequency. The method uses two actuators, one at either end of the waveguide to produce different relative phases, followed by a nonlinear model fitting procedure. Presented are a model-based derivation and experimental verification of the proposed approach on an air-filled elastic-tube. The latter shows the capability of the method to recover the dispersion curves even for very weak structural-acoustic coupling and at low frequencies. The portrayed scheme can be applied on various waveguides by using two actuators and only a single sensor, and hence makes dispersion curve estimation realistic in formerly inaccessible cases.
关键词： non-destructive measurement,phase perturbations,nonlinear model fitting,dispersion curves,acoustic properties,fluid-filled elastic-tubes
更新于2025-09-11 14:15:04
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A Method for Estimating the Filling Rate of the Mold Cavity in Nanoimprint Lithography
摘要： When the dimensions of a microelectronic structure decrease, high manufacturing costs are inevitable. A low cost and high throughput manufacturing technique for nanostructures is desired. Nanoimprint lithography involves patterning the resist through physical deformation by using a mold at nanoscale and has the potential to meet these expectations. Therefore, nanoimprint lithography has been extensively studied in recent years. Many real time measurements have been proposed for enhancing the yield of nanoimprint lithography. Among these measurements, the application of surface plasmon resonance has the advantage of quick, highly accurate analysis. In surface plasmon resonance application, the mold contains a gold ?lm for exciting surface plasmon resonance and an adhesion layer is applied to both sides of the gold ?lm to increase the lifespan of the mold. However, the effect of the geometric characteristics of the adhesive layer on the surface plasmon resonance spectrum and the mechanical strength of the mold has not been extensively studied. To improve the detection accuracy and reliability of the measurement, this study investigated the aforementioned effect. Analytical and experimental investigations con?rmed that the shape of the spectrum is in?uenced by the surface roughness and thickness of the titanium adhesion layer. To maintain the sharpness of the resonance dip, we suggest reducing the thickness of the titanium adhesion layer to below 6 nm and maintaining the surface roughness below 3 nm. Moreover, the proposed mold structure conforms to these requirements and is applied to estimate the ?lling rate. The measurement results demonstrate that the surface plasmon resonance spectrum is clearly affected by the mold ?lling. Speci?cally, the change in the surface plasmon resonance spectrum curve and resonance angle can indicate the quality of the imprinted pattern. This study demonstrates the effectiveness and high sensitivity of the proposed technique for estimating the ?lling rate of the mold cavity in nanoimprint lithography.
关键词： Nanoimprint Lithography (NIL),Surface Roughness,Filling Rate,Surface Plasmon Resonance (SPR),Non-Destructive Measurement
更新于2025-09-10 09:29:36