This paper describes surface plasmon polariton (SPP) modes that show extraordinary propagation behaviors along metal stripes with finite width, including multiple energy condensations. Phenomenological and quantitative investigations are carried out on these behaviors. Images of SPP modes at output edges for wide stripes exhibit multiple spots that spanned the lateral side of the stripes. The spot number is monotonously decreased as the stripe length increases. Besides, the input versus output power ratio shows a stepwise change as changing the propagation distance. We present a model of SPP modes to explain these behaviors.
Surface-plasmon polaritons (SPPs) existing at metal-dielectric interfaces with exponentially damped vertical intensity profiles have attracted much interest for their capability of confining light energy into a small space beyond the diffraction limit. Theoretical considerations have been given to understandings of wave behaviors based on Maxwell's equations taking into account metals as dielectric materials with negative permittivity. However, since this approach assumes metals as homogeneous media, it is difficult to perform detailed analysis on propagation mechanisms in three-dimensional micro and nano structures. Here we propose a theoretical method based on the dynamics of electric dipoles formed by local displacement of free electrons in metals to describe SPP waves. In this method, the Poisson equation is used to describe actual movement of electrons in metals interacting with the electromagnetic field. Based on this method, we have revealed fundamental properties including electron density distribution functions in the area close to metal surfaces, SPP waves are then modeled by reconstructing microscopic features of such novel electromagnetic waves in a given material systems. After this simple verification, we make the best use of this method to explain SPP propagation at ultra-thin metal films or along narrow metal wires.
KEYWORDS: Optical fibers, Optical signal processing, Silicon, Image resolution, Atomic force microscopy, Photoresist materials, Near field scanning optical microscopy, Near field, Semiconducting wafers, Near field optics
This paper describes the design and applications to optical processing and recording of a Scanning Near-field Optic/Atomic-force Microscope (SNOAM). A sharpened and bent optical fiber was used as a near-field optical probe as well as an atomic force microscope probe in a vertical vibrating mode. SNOAM provides simultaneous topographical and optical images with high resolution beyond the diffraction limit. As an example of an application to optical processing, near-field exposures have been demonstrated by a SNOAM. We produced pit and line patterns exposed and developed in commercial photoresist film. In the processing mode, the pit and line patterns down to a width of 100 nm have been fabricated on a Si wafer through the Integrated Circuits process.
A joint transform correlator with feedbacks from the correlation outputs to the input intensity of the reference images works as a neurocomputing system. The characteristics change catastrophically with the parameters of the feedback transfer function.
We report that nonlinear parameters effect the characteristics of the optical pattern recognition of a feedback joint transform correlator (FJTC) which is based on a joint transform correlator (JTC). This system incorporates the optically addressed ferroelectric liquid crystal spatial light modulator named LAPS-SLM. Nonlinear parameters in the FJTC are a threshold level of the LAPS-SLM to record the binary joint power spectrum (JPS), and a feedback transfer function from the correlation plane to the input plane. It is important to control the threshold level of the binary JPS. But the FJTC does not always need the optimum condition where the FJTC recognizes the signal image correctly at the initial recognition.
A rotation and scale invariant joint transform correlator is described. The polar-logarithmic coordinate transformation is used as a preprocessing of input images. The resultant coordinate transformed images are interfaced to a joint transform correlator. The use of optically addressed ferroelectric liquid crystal spatial light modulators at the coordinate transform plane and at the Fourier plane allows data to be processed faster than video rate and gives the characteristics of a binary joint transform correlator. The rotation and scale invariance of the correlator is demonstrated experimentally.
A new algorithm of the feedback joint transform correlator ( FJTC ) was proposed. The
system is made by using the ferroelectric liquid crystal spatial light modulator named
LAPS-SLM. The FJTC features excellent pattern recognition characteristics and pattern
associative characteristics, compared to conventional joint transform correlators ( JTC).