Synthesis and Properties of Photoisomerizable Derivatives of Isosorbide and Their Use in Cholesteric Filters

This paper describes the synthesis of photoisomerizable derivatives of isosorbide. These derivatives contain a stilbene or cinnamate moiety and can therefore be used as photoisomerizable chiral compounds in cholesteric liquid‐crystalline mixtures. The reflection wavelength of cholesteric layers made from these mixtures is increased by UV irradiation due to the fact that the Z‐isomers of these derivatives exhibit a lower helical twisting power than the corresponding E‐isomers. The cinnamate derivatives are very suitable for use in cholesteric color filters that find application in liquid‐crystal displays.     

A surface-mounted device assembly technique for small optics based on laser reflow soldering

The three-dimensional miniaturized optical surface-mounted device (TRIMO-SMD) is a new flexible and automated assembly technique for small optical components (maximum diameter for a lens is 2 mm) based on laser reflow soldering technique. This technology can be compared to the electronic SMD technique but applied to micro-optical devices. We present some recent developments of TRIMO-SMD in its application to industrial products.     

GaAs pHEMT-based technology for microwave applications in a volume MMIC production environment on 150-mm wafers

The establishment of a 150-mm (6-in) gallium arsenide (GaAs) facility is described together with the development of very high yielding and cost-effective semiconductor device technologies and a manufacturing capacity of over 40000 wafers/annum. The background to the demand for very high volumes of RF products for this market is discussed, together with the prospects for future growth. The paper describes recent process development by the utilization of a data-driven yield management system to support the delivery of high-quality RF products to customers. Finally, "end of line" DC and RF testing of finished 150-mm GaAs pHEMT foundry wafers is described, enabling scalar measurements of power, noise, and intermodulation products as well as vector measurements of S-parameters and noise parameters at frequencies of up to 40 GHz.     

At least N+1 finite transmission zeros using frequency-variant negative source-load coupling

A second-order cross-coupled combline filter which has three finite transmission zeros is presented. The problem of the frequency-invariant coupling in a real circuit is introduced. To make extra transmission zeros, a top metalized dielectric block is used.     

Influence of the model for random birefringence on the differential group delay of periodically spun fibers

We consider the two Wai-Menyuk models of birefringence in periodically spun fibers, and we show that the differential group delay differs significantly for the two models when the spin period approaches or exceeds the fiber beat length. When the fiber correlation length is large, we explain this difference quantitatively, and we explain it qualitatively for any fiber correlation length.     

Calculation of imaging errors of AWG

This paper reports on the modeling of arrayed-waveguide gratings (AWGs) by means of Fourier optics where the coupling between the grating waveguides and defocus of the star couplers is taken into account as well. Special interest is drawn to the geometrical modeling of AWGs. The paraxial approximation for the free-space propagation within the star couplers, the exact calculation of the coupling coefficients for the star couplers by an orthonormal basis (ONB) expansion, and the drawbacks due to the nonunitary transfer matrix provided by the Green's functions approach for the coupling between the grating waveguides, as well as possible improvements thereof, are identified as crucial points. An efficient orthonormalization procedure by means of an eigenvector decomposition is presented. A unitary approximation of the transfer matrix, which is in itself approximate but in general not unitary, introduced within the impulse response method, is obtained. The presented simulation technique allows for ab initio simulations, which do not fall back on any experimental input, for the spectral response of AWGs, which are found in good agreement with experimental results.     

The Gilbert-Holland FDTD thin slot model revisited: an alternative expression for the in-cell capacitance

This paper proposes an alternative expression for the in-cell capacitance of a photoelectrical cell (PEC)-mounted slot, which is the conceptual cornerstone of the Gilbert-Holland subcell finite difference time domain (FDTD) model. By treating a slightly modified electrostatic problem, the extraneous charge singularity on the PEC edges touching the cell, which is characteristic of the originally proposed model, is removed. The latter offers better physical grounds for a new expression of the capacitance and the effective permittivity used in the update equations. High resolution standard FDTD simulation results are presented in support of the new expression.     

A fast algorithm and practical considerations for passive macromodeling of measured/simulated data

Passive macromodeling of high-speed package and interconnect modules characterized by measured/simulated data has generated immense interest during the recent years. This paper presents an efficient algorithm for transient simulation of interconnect networks characterized by measured/simulated data in the presence of other linear and nonlinear devices. A new set of linear constraints are proposed, which help in preserving the passivity of resulting macromodels. Examples are presented to demonstrate the validity and efficiency of the proposed algorithm.     

A biomorphic digital image sensor

An arbitrated address-event imager has been designed and fabricated in a 0.6-/spl mu/m CMOS process. The imager is composed of 80 /spl times/ 60 pixels of 32 /spl times/ 30 /spl mu/m. The value of the light intensity collected by each photosensitive element is inversely proportional to the pixel's interspike time interval. The readout of each spike is initiated by the individual pixel; therefore, the available output bandwidth is allocated according to pixel output demand. This encoding of light intensities favors brighter pixels, equalizes the number of integrated photons across light intensity, and minimizes power consumption. Tests conducted on the imager showed a large output dynamic range of 180 dB (under bright local illumination) for an individual pixel. The array, on the other hand, produced a dynamic range of 120 dB (under uniform bright illumination and when no lower bound was placed on the update rate per pixel). The dynamic range is 48.9 dB value at 30-pixel updates/s. Power consumption is 3.4 mW in uniform indoor light and a mean event rate of 200 kHz, which updates each pixel 41.6 times per second. The imager is capable of updating each pixel 8.3K times per second (under bright local illumination).