We study enhancement of fluorescence of molecular species bound within metallic nanocavities. An electromangetic model of dipole radiation within a nanocavity shows an increase in radiative output consistent with experimental yield estimates and also verifies the strong fluorescence isolation from species lying outside the nanocavity.
In this paper, we study the linear and nonlinear responses of 1-D photonic bandgap (PBG) structures. We show that, the nonlinear interaction can be greatly enhanced by the use of Kerr defect modes in a 1D dielectric photonic crystal structure, such as low-intensity bistability and multistability, and by optimizing the design of the layer sequence. 1-D PBG structure can also be promising candidate as low-intensity nonlinear phase shifter. Nonlinear z-scan measurements of a 3-cavity thin-film PBG sample show that the nonlinearity is enhanced over the native material by a factor over 30, while maintaining a bandwidth greater than 1T Hz, which is great for all-optical switching.
We study enhancement of fluorescence of molecular species bound within metallic nanocavities. These nanostructures possess a number of desirable properties for real-time microarrays, such as localization of excitation light within the nanocavities, strong isolation from fluorescence produced by unbound species,and an apparent increase in fluorescence yield for bound species. Experimental measurements show a nearly a factor of 2 increase in excitation intensity within the nanocavities, and factor of 6 increase in yield. A simple electromangetic model of a dipole within a nanocavity shows an increase in radiative output consistent with our yield estimates and also verifies the strong fluorescence isolation from species lying outside the nanocavity.
We describe the basis for an affinity biosensor platform in which enhanced fluorescence transduction occurs through the optical excitation of molecules located within metallic nanocavities. These nanocavities are about 200 nm in diameter and are arranged in a periodic or random two-dimensional (2D) arrays, which are fabricated in 70 nm-thick gold films by e-beam lithography using negative e-beam resist. The experimental results show that both periodic and randomly placed metallic nanoapertures can be used to enhance the output of a fluorescing molecular monolayer by more than a factor of 10.
Dynamic geometric parameter measurement plays an important role in most industries. Research and development on this technology have attracted great attention. We proposed a laser tracking system for measuring development of laser tracking technology, a laser tracking system consisting of three tracking and measuring stations is described in detail. The three stations track respectively three retro reflectors on the moving target, and measure the position and attitude. We built the mathematical model of measurement and developed the algorithm for processing data. According to the homogeneous coordinate transformation, we deduced the formulae for computing coordinates and attitude under different coordinate systems. Some key techniques of the measuring system are discussed at the end of the paper.
The spatial position of industrial object, such as robot end- effector, is an important geometric parameter whose accuracy determines whether robot can perform accurately. Therefore, we have established a laser tracking and coordinate measuring system with galvanometer scanner for high accuracy, large range, non- contact, and spatial dynamic measurement. In this paper, the laser tracking system and its setup are illuminated at first. Then, the formulae for calculating coordinates are deduced, and the calibration method of the initial distance from tracking mirror to target is presented. After that, two preliminary experiments in different distances are described. One is on CMM; the other is with grating ruler as reference. In the former, the maximum measurement error of coordinates is 70micrometers and the maximum error of length is 35micrometers in the 85x100x100mm3 measurement volume, and in the 1m initial distance. In the later, the maximum error of length is 140micrometers in the range of 480mm, and in the 5m initial distance. At the end of the paper, the error sources are analyzed and simulated.
The main methods for measuring geometric parameters used to be static or quasi-static. At present, former static measurement methods with sliding guide have met with great difficulty when measuring the outline and profile of large-scale workpiece or coordinates of objects moving in large dimension. Thus we established the laser tracking system for high precision, large range, non-contact, dynamic measurement. Laser tracking system involves in interdisciplinary knowledge and it can be made up into a new type of computer integral system with both measuring and controlling capacity. With common static coordinate measurement system, such as CMM, the probe must move along the three orthogonal guides equipped with standard rulers, while the laser tracking system has no such objective reference coordinate system. So we put forward the notion of 'Virtual Coordinate System,' that means during the measurement, the coordinate frame is not fixed. On the primary stage of our research, we established practical system for 2D moving target measurement in real-time. In order to measure the coordinate of the target, three tracking stations are used, which only measure length changes between the target and stations each, with no angles are measured. By solving non- linear least-square equations, the target and the tracking stations' coordinate can be attained respectively. We also present the optical design and the tracking controlling system based on the PID controlling principle. At the end of this paper, we will give the experiment result of the system.
Laser tracking and measuring system is made for real-time measurement of dynamic target in industry field and it can be made up into computer integral system with both measuring and controlling capacity. The system has no objective reference coordinate system, during the measurement, its coordinate frame is not fixed, so we call this coordinate system as Virtual Coordinate System. Laser tracking system involves interdisciplinary knowledge, such as laser dynamic aiming technique, laser interferometry, optical system and precision mechanism design, motor controller design and modern numerical computation. This paper mainly focuses on the otpical system analysis and design. The system, which can track and measure the dynamic target, uses the dual- frequency laser interferometer as the light source and length-measured sensor simultaneously. The interferometer produces linear-polarized orthogonal beam with two different frequencies. When the beam passes through the optical system, its polarization and amplitude will be both changed. This paper presents vector analysis method for the optical tracking systems and analyzes the polarization effect of the optical system on the light beam incident in any direction by Jones matrix analysis. On the basis of analytical and experimental results, the optical scheme is optimized in order to improve the tracking and measuring performance of the whole system.
The main methods for measuring geometric parameters are used to be static or quasi-static measurement. Recently, however, dynamic geometric parameters measurement has been becoming increasingly important and turning into a new field in metrology. The laser tracking system for measuring dynamic geometric parameters of moving targets employs laser dynamic aiming technique, laser interferometry and control technique of precision instruments. The moving target is tracked and its geometric parameters are measured in real time. The measurement range is one to ten meters and the accuracy is fifty microns per meter. It is a novel computer integral system with both measuring and controlling capacity. This paper present the characteristic and concept of dynamic geometric parameters measurements and puts forward the cardinal measuring principles and methods of the laser tracking system. This paper also gives a more detailed discussion about the key techniques for this system, which are different from the static measurement, such as the self- calibration principle, the redundancy design principle, the fault-tolerant design principle, the virtual coordinate system establishment principle. We will also discuss the developing trend of laser tracking system for measuring dynamic geometric parameters at the end of the paper.
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