We present a highly purposive technique to optically induce periodic photonic lattices enriched with a negative defect site by using a properly designed nondiffracting (ND) beam. As the interference of two or more ND beams with adequate mutual spatial frequency relations in turn reproduces an ND beam, we adeptly superpose a hexagonal and a Bessel beam to create the ND defect beam of demand. The presented wavelength-independent technique is of utmost universality in terms of structural scalability and does not make any specific requirements to the photosensitive medium. In addition, the technique is easily transferable to all pattern-forming holographic methods in general and its application is highly appropriate, e.g., in the fields of particle as well as atom trapping.
We introduce a universal method to optically induce multiperiodic photonic complex superstructures bearing two-dimensional (2D) refractive index modulations over several centimeters of elongation. These superstructures result from the accomplished superposition of 2D fundamental periodic structures. To find the specific sets of fundamentals, we combine particular spatial frequencies of the respective Fourier series expansions, which enables us to use nondiffracting beams in the experiment showing periodic 2D intensity modulation in order to successively develop the desired multiperiodic structures. We present the generation of 2D photonic staircase, hexagonal wire mesh and ratchet structures, whose succeeded generation is confirmed by phase resolving methods using digital-holographic techniques to detect the induced refractive index pattern.
We present a method based on incremental holographic multiplexing to create a refractive index ratchet distribution into a photorefractive crystal as an example for the generation principle of such complex multiperiodic lattices. The implemented technique follows a finite optical series expansion of the desired index modulation. To analyze the induced lattice, we determine the phase retardation of a probe beam at the back face of the crystal by digital holography analysis. Our result depicts a first example to optically explore the fascinating phenomena of ratchet resembling systems.
Silicon-on-Insulator (SOI) is the most commonly used technology for integrated circuits capable of operating at high temperature. Due to the efficient reduction of leakage current paths much higher operation temperatures are achievable with SOI than with bulk technologies. Published work on high temperature CMOS circuits typically refers to technologies with a minimum feature size of 0.8 to 1.0 micron [1][2][3] even though for complex digital circuits this results in large die size. Technologies with smaller feature size are available but typically not suitable for reliable high temperature operation due to high leakage currents, decreasing threshold voltages over temperature or reliability issues with the standard aluminum metallization.
Fraunhofer IMS has developed a high temperature 0.35 micron thin film SOI technology. The mixed signal technology provides numerous devices, e.g. specific transistors for analog and digital circuit design, diodes, resistors and voltage independent capacitors. Also non-volatile memory cells (EEPROM) are available. In addition the technology is equipped with a tungsten metallization for highly reliable operation even at high temperatures. An overview on the new technology including characterization results of devices and test circuits is given in this paper.
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