Passive laser-fiber alignment by index method

A method for packaging a laser-fiber module was explored in which the critical laser-fiber alignment is carried out not with the usual active means, i.e., with the laser activated, but by a passive method based on the registration principles of photolithography. The method relies on an index scheme in which fiducial marks are lithographically placed on the laser chip and on a fiber carrier. At 850 nm, using the index technique with cleaved multimode fibers, it was possible to achieve the same laser-fiber coupling efficiency as attained by active alignment; with cleaved single-mode fibers about 80% of the active-alignment coupling efficiency was achieved.<>     

Deformation behavior of solid polymer during hot embossing process

Though hot embossing is a well known technique for the fabrication of polymer based micro-device, the deformation behavior of solid polymer during hot embossing process is not investigated clearly. In this paper, the deformation behavior of solid polymer was observed by two methods, synchronous observation and asynchronous analysis. A finite element simulation and a phenomenological model were used to evaluate the deformation behavior of solid polymer during hot embossing. Results showed that the deformation of solid polymer during embossing process included two stages. One was a stress concentration and strain hardening stage, which occurred during the heating and applying pressure process. The “swallowtails” induced by incomplete filling generate at this stage. The other was a stress relaxation and deformation recovery stage, which occurred during the remaining temperature and pressure process. The “swallowtails” were eliminated at this stage. The second stage was significant for improving replication precision, but it had not been reported before.     

Microlens array produced using hot embossing process

In this paper, the fabrication of molds that are suitable for the production of microlens arrays using the replication technique is discussed. Variation of parameters in the replication process were investigated. A focused ion beam was used to fabricate the microlens cavities on three materials, with silicon showing the best result. Hot embossing was used to produce replicated polycarbonate lens array. The temperature of the mold and the embossing force were the two parameters varied. The microlens array produced using the embossing replication process demonstrates the possibility of nanometre fabrication.     

Pattern replication in polypropylene films by hot embossing

The hot embossing of electron beam generated structures with linewidths of 0.35-3.25 μm has been examined in biaxially-oriented polypropylene (BOPP). The individual test elements consisted of pixels of 30 × 30 μm containing a specific configuration of symbols and lettering. The embossing of these features has been performed as a function of temperature (80-140 °C) and applied pressure (2-20 kPa). Significant increases in both embossed depth and sidewall angle were evident over the temperature range 100-130 °C with a leveling off at higher temperatures attributed to the onset of a regime of viscous liquid flow. At temperatures within this regime, a critical level of pressure was required to fill the mold features. Accurate embossing of medium and coarse lettering (0.50-0.65 μm linewidth) and geometric symbols (1.25-3.25 μm linewidth) has been demonstrated at a temperature of 130 °C and an applied pressure ?13 kPa. The depth of the finest lettering (0.35 μm linewidth) was incompletely embossed under these conditions.     

Direct stamp fabrication for NIL and hot embossing using HSQ

Commonly stamps or masters for nanoimprinting are made by electron beam lithography (EBL) and subsequent reactive ion etching into silicon. Here we present a single step procedure to prepare stamps suitable for nanoimprinting and hot embossing. The stamps are directly fabricated in HSQ (hydrogen silsequioxane), a negative EBL resist, which has a high lateral resolution and good mechanical properties. We demonstrate successful pattern transfer in both bulk PMMA and PCL by hot embossing with features down to 20 nm. Such pattern transfer is useful for biological applications. Also, we demonstrate that this approach can make stamps suitable for nanoimprint lithography and have achieved features as small as 35 nm. It was found that the stability and strength of the HSQ could be improved by annealing and that the application of a non-stick coating was not necessarily required although it aided the demoulding.     

Passive electro-optic antenna using polymer material

The experimental results of a polymer microwave electro-optic antenna are reported. The device amplitude-modulates an optical input beam with a free-space propagating electromagnetic wave. By using a new dipole printed antenna, the electromagnetic energy is concentrated inside the device. An antenna factor of 168 dB/m is achieved with only 1 mum of electro-optic polymer     

A novel method for fabrication of a PLC platform for hybridintegration of an optical module by passive alignment

A novel fabrication method and structure of a planar lightwave circuit (PLC) platform for hybrid integration of an optical module by passive alignment technology is presented. Precise formation of V-grooves in the PLC platform can be easily obtained by the proposed process. The passive alignments of optical elements, including optical fiber, are achieved in one-mask. LD modules were implemented by the proposed method     

Microfabrication of a nickel mold insert by a modified deep X-ray lithography process and its application to hot embossing

In the present study, a modified deep X-ray lithography process is utilized for an efficient fabrication of precise metallic mold insert. A bare bulk polymethylmethacrylate (PMMA) sheet is used without any substrate as an X-ray photoresist in order to achieve a stable fabrication by avoiding a generation of a secondary radiation during a deep X-ray lithography process. The patterned PMMA sheet after development is then bonded on a metallic substrate using adhesive layers. The adhesive layers on the opened region of the patterned PMMA sheet are subsequently removed by X-ray exposure of short duration time. The next procedure is an electroplating process onto the opened area in the PMMA sheet, consequently resulting in the final mold insert. In this manner, a robust metallic mold insert for a mass replication of microstructures could be realized quite efficiently. The present fabrication method is confirmed by an example with a replication of microchannels via hot embossing process.     

Novel fiber alignment method using a partially metal-coated fiberin a silicon V-groove

We propose a novel fiber alignment method using a partially metal-coated (PMC) fiber. A PMC fiber is a fiber whose side is partially metal coated, and a core of PMC fiber can be regarded as eccentric with respect to the outside of PMC fiber. Rotating the PMC fiber in a silicon V-groove, the core position can be aligned. Using this method, laser diode modules with high coupling efficiency were obtained     

Contact-degradation studies on GaAs transferred-electron devices using a focused backscattering technique

Focused backscattering microanalysis has been used to overcome some of the problems associated with conventional backscattering. The small beam size enables the study of (a) small areas typical of real microwave devices, (b) lateral variations of the contact interdiffusion and (c) deep profiles when used in conjunction with angle lapped samples.     

Fabrication of gold sub-wavelength pore array using gas-assisted hot embossing with anodic aluminum oxide (AAO) template

This paper reports a novel and effective method for the fabrication of gold sub-wavelength pore array using gas-assisted hot embossing. The novel fabrication comprises the fabrication of AAO template with high order pore array, sputter-coating of gold and gas-assisted hot embossing. AAO template is fabricated by a two-step anodization process. It is then coated with gold (100 nm thick). The gold sub-wavelength pore array is finally formed by using gas-assisted hot embossing process. The transmission spectra of gold sub-wavelength pore array are measured in several conditions such as air, water and glycerol/water mixture. The detection shows significant shift in the wavelength of resonance peak. The gold sub-wavelength pore array can be employed as optical biosensors.     

Network reliability evaluation of three-state devices using transformation technique

Equations for delta-star and star-delta transformations are derived for 3-state device networks. These equations are obtained by equating probability of failure for a pair of nodes of both delta and star network. A function minimization method is suggested to solve the nonlinear algebraic equations in case of the star-delta transformation.     

Printing via hot embossing of optically variable images in thermoplastic acrylic lacquer

A novel printing process via hot embossing of either grating or micro-mirror microstructures has been demonstrated in thermoplastic acrylic lacquer. Embossing experiments were performed in the temperature range 100-150 °C and at 80 kN force. The range of microstructures has included a dot-matrix hologram, grating-based optically variable devices (OVDs) and a micro-mirror based OVD. High quality replicas of each type of device have been fabricated using this process. Embossed replicas of grating-based OVDs have shown optical effects including image switching and color movement. For devices based on micro-mirror arrays, the embossed replicas have shown an optically variable switch between a portrait and a non-portrait image. Printing via an embossing process offers the possibility of incorporating optically variable devices into documents without the use of hot stamping foil. This is particularly relevant for documents based on polymeric substrates such as credit cards and polymer banknotes.     

A replication process of metallic micro-mold by using parylene embossing and electroplating

This study demonstrated a replication process for metallic micro-mold that combines the parylene-C (poly-chloro-p-xylylene C) hot-embossing and electroplating techniques. A nickel original master was fabricated using the deep RIE silicon etching followed by the electroplating process. Then, the patterned fields composed of arrays of 25 μm-high, 10 μm-wide and 1 mm-long lines with 10 μm spacing in nickel molds were successfully replicated on the 60 μm-thick parylene-C films by the hot-emboss process. Under complete filling conditions, the deviation of the replicated micropattern was less than 2.4%. The electroplated copper successfully filled parylene-C replica master patterns with the aspect ratio of 2.5 without the void formation by both adding organic addictives and controlling the seed layer thickness. After electroplating, the copper micro-mold could be successfully separated from the parylene-C replica master.     

Inverse scattering method for one-dimensional inhomogeneous lossymedium by using a microwave networking technique

The formulation of reflection coefficients from an inhomogeneous lossy medium illuminated by TE and TM waves is approximately derived, in closed form, by using a microwave network method. From the formulation, a novel inverse scattering scheme to reconstruct simultaneously the permittivity and conductivity profiles, is proposed. This scheme is suitable for both continuous and discontinuous profiles, under both the weak scattering and strong scattering conditions. It has also been shown that when the conductivity of the medium equals zero, the reconstructed result of this scheme will reduce to the one formulated by Ladouceur and Jordan (1985). Numerical and closed-form reconstruction examples show the validity of the scheme     

Optimum design method of optoelectronic devices using simulatedannealing

A design methodology for optimizing optoelectronic functional devices is described. The introduction of cost function for electrical and optical device characteristics enables automatic optimization by simulated annealing. The optimum design of AlGaAs/GaAs pnpn differential optical switches in consideration of light emission efficiency, light sensitivity, and switching voltage is successfully demonstrated     

Novel high precision alignment technique for polarisation maintaining fibres using a frequency modulated tunable laser

A precision alignment technique for polarisation-maintaining, fibres is described using a frequency modulated tunable laser in combination with phase sensitive detection. The effect of residual intensity modulation is overcome by detecting the signal at twice the modulation frequency. An alignment accuracy of better than 0.2 degrees was achieved.<>     

GaAs Hall-effect devices fabricated by ion-implantation technique

Gallium-arsenide Hall-effect devices were developed by using Se-implanted n layers. A Hall voltage of 85 mV was generated at I = 1 mA and B = 5 kgauss. The imbalance voltage appearing was below 1.4 mV at I = 1 mA and B = 0.This fabrication technique is very promising in the high throughput of GaAs Hall-device production.     

An accurate design method of bipolar devices using a two-dimensional device simulator

The systematic application of two-dimensional analysis for the bipolar device design is described. In this analysis, surface recombination is taken into account by properly modifying the carrier lifetime term, in addition to mobility variations and bandgap narrowing effects. Moreover, an effective method to obtain terminal currents from the calculated current densities is introduced. The analysis of transistors with different emitter length demonstrates the validity of this procedure. The propagation delay time of IIL also is calculated usingV-Icharacteristics and capacitances obtained by this two-dimensional analysis. The results give good agreement with experimental ones. IIL and SFL with subnanosecond gate delay time are designed with the suitable geometry and doping profiles by the two-dimensional analysis.