Recently there has been growing interest in sensing by means of optical microring resonators in photonic integrated circuits that are fabricated in silicon-on-insulator (SOI) technology. Taillaert et al. [Proc. SPIE 6619, 661914 (2007)] proposed the use of a silicon-waveguide-based ring resonator as a strain gauge. However, the strong lateral confinement of the light in SOI waveguides and its corresponding modal dispersion where not taken into account. We present a theoretical understanding, as well as experimental results, of strain applied on waveguide-based microresonators, and find that the following effects play important roles: elongation of the racetrack length, modal dispersion of the waveguide, and the strain-induced change in effective refractive index. © 2012 Optical Society of America OCIS codes: 120.4880, 160.1050, 130.7408, 280.4788, 160.6000, 000.2190 Piezoresistive electronic strain gauges are frequently used in micromachined electromechanical systems (MEMS) [1]. Alternatively, all-optical systems can be used, and they have particular benefits, such as being insensitive to electromagnetic interference, not having the danger of initiating gas explosions with electric sparks, and allowing for high speed readout. Guo and co-workers employed an optical polymer microring resonator as an ultrasound sensor, in which the deformation of the resonator was measured by monitoring its shift in resonance frequencies [2,3]. Taillaert et al. [4] proposed the use of a silicon optical microring resonator as a strain gauge. Silicon-on-insulator (SOI) technology has emerged as a focus platform for integrated photonics, with complementary metal-oxide semiconductor (CMOS) production lines, opening the possibility of mass fabrication [5]. Silicon is the commonly used material in MEMS, and we have shown the possibility of micromachining postprocessing of SOI photonic integrated circuits [6]. Strong lateral confinement of the light due to the high refractive index contrast of SOI waveguides (Δn ≈ 2) allows for small device footprint, but also comes with high sensitivity to the exact behavior of the modes in the waveguide, e.g., strong modal dispersion [7,8]. Amemiya et al.[9] reported on the photoelastic effect in strained SOI ring resonators without, however, considering the modal effects, such as dispersion. In this Letter, we first derive a model explaining the effects that play a role when considering the influence of strain on photonic waveguides. Then, we characterize these effects with a novel mechanical setup providing a well-defined strain. We describe the important effects when a strain is applied to a ring resonator that has a racetracklike shape with circumference l, as depicted in Fig. 1. Light is coupled from a connecting waveguide to the racetrack waveguide by means of a multimode interference (MMI) coupler [10,11]. Having such a long racetrack allows us to neglect the effect of the bends and of the coupler. The transmitted spectrum at the output port of the connecting waveguide shows dips at the wavel...
Microscale strain gauges are widely used in micro electro-mechanical systems (MEMS) to measure strains such as those induced by force, acceleration, pressure or sound. We propose all-optical strain sensors based on micro-ring resonators to be integrated with MEMS. We characterized the strain-induced shift of the resonances of such devices. Depending on the width of the waveguide and the orientation of the silicon crystal, the linear wavelength shift per applied strain varies between 0.5 and 0.75 pm/microstrain for infrared light around 1550 nm wavelength. The influence of the increasing ring circumference is about three times larger than the influence of the change in waveguide effective index, and the two effects oppose each other. The strong dispersion in 220 nm high silicon sub-wavelength waveguides accounts for a decrease in sensitivity of a factor 2.2 to 1.4 for waveguide widths of 310 nm to 860 nm. These figures and insights are necessary for the design of strain sensors based on silicon waveguides.
The Gaia mission 1 will create an extraordinarily precise three-dimensional map of more than one billion stars in our Galaxy. The Gaia spacecraft 2
With the device dimensions moving towards the 1X node, the semiconductor industry is rapidly approaching the point where 10 nm defects become critical. Therefore, new methods for improving the yield are emerging, including inspection and review methods with sufficient resolution and throughput. Existing industrial tools cannot anymore fulfill these requirements for upcoming smaller and 3D features, since they are performing at the edge of their performance. Scanning probe microscopy (SPM) has the ability to accurately measure dimensions in the micrometer to nanometer scale. Examples of applications are surface roughness, channel height and width measurement, defect inspection in wafers, masks and flat panel displays. In most of these applications, the target area is very large, and, therefore, the throughput of the measurement plays an important role in the final production cost. Single SPM has never been able to compete with other inspection systems in terms of measurement speed, thus has not fulfilled the industry needs in throughput and cost. Further increase of the speed of the single SPM helps, but it still is far from the required throughput and, therefore, insufficient for high-volume manufacturing. Over the past three years, we have developed a revolutionary concept for a multiple miniaturized SPM heads system, which can inspect and measure many sites in parallel. The very high speed of each miniaturized SPM unit allow the user to scan many areas, each with the size of tens of micrometers, in a few seconds. This paper presents an overview of the technical developments and experimental results of the parallel SPM system for wafer and mask inspection.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.