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An experimental characterization of the grating couplers for sub-micrometer silicon-on-insulator (SOI) waveguides is presented. The grating couplers have been designed, realized, and characterized for the +1 diffraction order at an operating wavelength of 1.31 mum for TE polarization. At the resonant angle, a coupling efficiency higher than 55% has been measured. The angular coupling range and the wavelength tolerance have been evaluated to 3deg and 20 nm, respectively. The grating coupler is followed by a taper, and about 50% of the input power at 1.31 mum is coupled into sub-micrometer rib and strip SOI waveguides. The ration between light power decoupled toward the cladding and light power decoupled toward the substrate is about three [ABSTRACT FROM PUBLISHER]

An innovative design is presented enabling fine positioning of each individual fiber in a fiber array used in multiinput- and multioutput-port photonic integrated circuits. Hence, the coupling efficiency of lensed fiber arrays can be improved by eliminating the eccentricities of the lenses deposited on the individual fibers and the inaccuracies of the supporting V-groove substrates. In preparation, four different types of commercially available lensed fibers are characterized and coupling efficiencies to InP-based waveguides are determined in order to select the best applicable fibers for the array. The final fiber-tip position accuracy is within plusmn0.25 mum and this design is based on metal deformation by laser-welding-induced local heat. With this technique, laser-supported adjustment is possible, allowing the opportunity of fine-tuning the fiber-tip position of already secured parts in the subassembly. Owing to the accurate fiber-tip position and the assembly of the array with selected lensed fibers, coupling efficiencies of -2.9 to -3.5 dB are simultaneously measured for four fibers to InP-based waveguides with physical dimensions of 3 mum times0.6 mum. To compare these results, the performance of different types of regular, commercially available fiber arrays, whereby the fibers are mounted on silicon V-groove substrates, are determined. In contrast, the measured coupling efficiencies are of the order of -5.2 to -7.8 dB using similar InP-based waveguides [ABSTRACT FROM PUBLISHER]

A high-power laser diode (LD) has an elliptical mode field at the endface of its laser diodes. A mode field mismatch between the high-power LD and single-mode fibers (SMFs) results in low coupling efficiency. Accordingly, various methods for coupling between the LD with the higher aspect ratio and SMFs have been employed. Among these approaches, the quadrangular pyramid. shaped fiber endface (QPSFE), which has the capability to control both axial curvatures, can easily match the far field of the high-power LD. However, a QPSFE, which was fabricated by polishing techniques, is hard to employ because of the special shape involved and the need for high precision. This paper presents a novel method for automating QPSFE polishing based on a thorough system analysis and using an online image inspection system. The system successfully supported automatic polishing with an encouraged fiber tip offset that ensures high coupling efficiency. Such an automatic polishing system can also be applied to any other type of fiber endface. [ABSTRACT FROM AUTHOR]

In this paper, an accurate model of the far-field radiation of a tapered optical fiber, which is widely used in communication optics and biomedical tomography, is presented. The authors first analyze the far field that is radiated from the normally cut fiber then extend the model to a fiber with a tapered end by considering the different phase contributions of the emitted rays. The proposed technique shows the effects of the cut with a view of obtaining a high efficiency both in coupling and radiation pattern characteristics [ABSTRACT FROM PUBLISHER]

Multimode interference (MMI) devices operating at high data rates are important in optical interconnects and optical networks. Their 1timesN splitting provides a fundamental functionality in these and other applications. To determine the speed limitations of MMI devices, the ultrashort pulse response of these devices is modeled. For example, for 50-fs Gaussian input pulses into a 1 times 16 splitter, the output pulses are severely degraded in coupling efficiency (48%) and completely broken up in time primarily due to intermodal and intramodal (waveguide) dispersion. Material dispersion is found to play only a minor role in the pulse response of MMI devices. However, for 1-ps input pulses into the same 1 times 16 splitter, the output pulses are only moderately degraded in coupling efficiency (86%) and only slightly degraded in shape [ABSTRACT FROM PUBLISHER]

Abstract: The surfaces of low alloy and martensitic stainless steels have been transformation hardened in inert and oxidizing atmospheres using a high-power diode laser beam. The effect of oxide layer growth on the absorptivity of the materials to the laser beam is investigated. When hardening was performed in an inert atmosphere, absorptivity values between 35% and 40% were obtained for both steels, with lower values being associated with higher peak temperatures. In an oxidizing atmosphere, the material composition and the processing variables are shown to play an important role in determining the material absorptivity and the extent of hardening. Absorptivity is found to increase with an increase in peak surface temperature and beam–material interaction time because of the growth of an absorbing oxide layer, particularly in the case of the low alloy steel. The corrosion resistance of the stainless steel grade restricted oxide layer growth, thus limiting the increase in absorptivity. The data obtained illustrate the advantages of diode laser beam hardening over longer-wavelength alternatives, and can be used to select processing parameters. They are also valuable in calibrating existing mathematical models of laser transformation hardening. [Copyright &y& Elsevier]

Microlens arrays are introduced on glass substrates to improve the out-coupling efficiency of organic light-emitting devices (OLEDs). The microlenses suppress waveguiding loss in the substrate. A theoretical model, based on electromagnetic wave propagation and geometric ray tracing, is developed to simulate the enhancement effects and optimize the structure parameters of the lens pattern. A simple soft-lithography approach is employed to fabricate the microlens array on glass substrates. With the use of an optimized lens pattern, an increase of over 85% in the coupling efficiency of the OLED is expected theoretically. An increase of 70% in the coupling efficiency is achieved experimentally, without detrimental effect to the electrical performance of the OLED. [ABSTRACT FROM PUBLISHER]

A method based on a genetic algorithm (GA) is used to design the optimum configuration of defects that when put within a photonic-crystal (PhC) taper improve the coupling efficiency between dielectric and PhC waveguides (WGs). This approach optimizes the whole configuration of defects simultaneously and, therefore, takes into account the correlation among the defects. Transmission efficiencies up to 94% have been predicted for a 3-μm-wide dielectric WG into a single-line-defect PhC-WG. This result significantly improves the transmission efficiency of the same PhC taper without defects. The influence on the coupling efficiency of the PhC taper length and geometry are also discussed. [ABSTRACT FROM PUBLISHER]

This paper presents the study of coupling efficiencies between two-dimensional (2-D) waveguides and microring resonators with a newly developed high-order discontinuous Galerkin time domain (DGTD) method for Maxwell's equations. The DGTD method is based on a unified formulation for the physical media and the artificial media in the uniaxial perfectly matched layer (UPML) regions used to truncate the computational domain. The DGTD method employs finite element type meshes and uses piecewise high-order polynomials for spatial discretization of the Maxwell's equations and Runge-Kutta methods for time integration. After demonstrating the high-order convergence of the DGTD method, the effect of separation gap between the waveguides and one and two microrings on the coupling efficiency and transmittance for pulse propagations is studied. [ABSTRACT FROM PUBLISHER]

Abstract: In this paper, we present a simple technique to determine the coupling efficiency between a laser diode and a lensed-tip based on the ABCD transformation matrix method. We have compared our analysis technique to that of previous work and have found that the presented method is reliable in predicting the coupling efficiency of lensed-tip and has the advantage of simplicity of coupling efficiency calculation even by a pocket calculator. The results can be useful for designing coupling optics. [Copyright &y& Elsevier]

Abstract: The coupling reaction of melt linear low density polyethylene (LLDPE) initiated by dicumyl peroxide (DCP) in steady shear flow field was investigated. The conversion of DCP was measured by electron spin resonance (ESR) and chemical titration. An absolute method was proposed to calculate the actual conversion of DCP from rheological data. The coupling efficiency of DCP was obtained from those analyses, which was shown to increase at first, reach a maximum and then decrease in the end stage. A linear relationship between the coupling efficiency of DCP and the concentration of macroradicals was also found in the experiments. [Copyright &y& Elsevier]

A novel three-dimensional (3-D) propagation analysis of coupled waveguides using local normal modes and the segmentation along the propagation axis was developed. The coupling efficiency of vertically coupled microring resonators was optimally designed using this analysis. The computation time is much faster and the required memory capacity is much smaller than those of the 3-D finite-difference time-domain (FDTD) method. [ABSTRACT FROM PUBLISHER]

Abstract: In this paper, we demonstrate a novel method for optimizing the in- and out-coupling of light confined in the fundamental high-Q whispering-gallery mode of a microsphere resonator via an external prism coupler. The technique relies on the use of a near-field probe to map the modes of the resonator and to obtain topographical information at the same time. We demonstrate the feasibility and efficiency of this technique by applying it to a sphere with a radius of 59μm. [Copyright &y& Elsevier]

Abstract: Phenylalanine hydroxylase (PAH) is a tetrahydrobiopterin (BH4)-dependent enzyme that catalyzes the hydroxylation of l-Phe to l-Tyr. The non-heme iron in the enzyme (Fe(III) as isolated) is 6-coordinated to a 2-His-1-carboxylate motif and three water molecules (wat1, wat2 and wat3). Tyr325 is at the second coordination sphere, hydrogen-bonded to water (wat1). We prepared and expressed mutants with Leu, Ala, Ser and Phe at this position. Only Y325L and the conservative mutation Y325F resulted in stable enzymes, but the mutant Y325F has been found to be post-translationally hydroxylated and to revert back to wild-type PAH [S.D. Kinzie, M. Thevis, K. Ngo, J. Whitelegge, J.A. Loo, M.M. Abu-Omar, J. Am. Chem. Soc. 125 (2003) 4710–4711], being inadequate to investigate the early inferred functional role of Tyr325. On the other hand, compared to wild-type PAH, Y325L shows reduced specific activity, decreased coupling efficiency and decreased iron content. The mutant also reveals a very high affinity for l-Phe and BH4 and does not manifest positive cooperativity for the substrate. All together, our results support that the mutation Y325L causes the removal or increased delocalization of the iron-ligated wat1 and, in turn, a less tight binding of the metal. Tyr325 thus appears to have an important role ensuring stoichiometric binding of iron, correct geometry of the complexes with substrate and cofactor and, consequently, a right coupling efficiency of the PAH reaction. In addition, the residue appears to be important for the correct cooperative regulation by l-Phe. [Copyright &y& Elsevier]

For the design of reliable micro-optical devices with a high coupling efficiency, a source-modeling method necessary for ray tracing is newly proposed. This method is based on the ray-division of an incident wavefront estimated by Gaussian beam optics. The simulation result obtained using the proposed method was compared with those of the conventional methods, and its accuracy was confirmed by the experimental results. Finally, the method was used to design a micro-optical device with two GRIN lenses and a thin-film filter. [ABSTRACT FROM AUTHOR]

A model to investigate the frequency response of waveguide (WG) p-i-n photodetectors (PDs) is presented. The model is based on the 2-D position-dependent distribution of carriers in the device and the results show that the contribution to the total current mainly comes from a small length of the PD measured from its input end. The effect of carrier trapping at a heterointerface has also been considered to study the frequency dependence of the photocurrent at low-bias voltages. The frequency response and bandwidth obtained from the model are in good agreement with published experimental results. A simplified and approximate relation for the fiber-to-WG coupling efficiency has also been used to calculate the overall quantum-efficiency of WGPDs. Then, the effect of WG geometry on the band- width-quantum efficiency product has been analyzed and some results on the optimum design of a WG p-i-n PD for maximum bandwidth-quantum efficiency product have been tabulated. [ABSTRACT FROM AUTHOR]

A new scheme for the lensed fiber employing a conical-wedge-shaped fiber endface (CWSFE) for coupling between the high-powered 980-nm laser diodes and single-mode fibers (SMFs) is proposed. The CWSFE was fabricated by following grinding and polishing techniques and then through heating in a fusing splicer to form an elliptical microlens endface. A coupling efficiency of 84% has been demonstrated. The higher coupling efficiency of the CWSFE lensed fiber was attributed to the better matching of both the elliptical Gaussian field distribution and the aspect ratio between the laser source and the fiber. In comparison to other fabrication techniques of lensed fiber used in high-power diode lasers, the advantages of this novel CWSFE structure are the ability to control over two axial curvatures and a small fiber offset through grinding and polishing processes to form a good elliptical endface. The results of this study have led to the development of a simple and reproducible fabrication process for achieving a high-yield and high-coupling CWSFE structure that is suitable for use in commercial high-power pump laser modules. [ABSTRACT FROM PUBLISHER]

Controlling welding-induced-alignment-distortion (WIAD) and maintaining coupling efficiency is obviously the most challenging issue in assembling of fiber-optic components using laser welding. WIAD is the dominant barrier to having high packaging yields. Previous investigation has revealed that the WIAD in butterfly laser diode module packaging could be mitigated by properly choosing weld process parameters such as welding sequence. In this paper, the effect of welding sequence on WIAD is studied numerically by finite-element method (FEM) with a more realistic physics based laser welding model and experimentally by welding prototype butterfly packages. Results from both methods are compared. It is shown that the influence of welding process parameters on WIAD is significant and WIAD control is possible if proper welding sequence is employed. [ABSTRACT FROM PUBLISHER]

Abstract: Longitudinally shifting waveguide junctions can achieve high efficiency light coupling from external silica waveguides into photonic crystal waveguides (PCWs) without requiring taper PCW structures in the waveguide junctions. Due to the periodic field distribution of PCWs along the propagation direction, maximum and minimum coupling efficiency occur when waveguide junctions are located near the peak and valley of the longitudinal mode profile, and coupling efficiency depends on both the localization of mode fields in PCWs and the group velocities of eigenmodes. Coupling efficiency of 86% between silicon/silica PCWs and external silica waveguides can be achieved without the need for special design in the junction region for the reduced-rod PCW. Due to large Bragg reflection, coupling of the band edge modes at the flat dispersion regions that possess small group velocities is inefficient. [Copyright &y& Elsevier]

The coupling efficiency between two step-index multimode fibers of different numerical apertures with an angular misalignment is calculated. The theory is presented using radiometry and geometrical optics. The limit case of the calculation is consistent with a previously published result. Applications include power launching between two types of fibers with different numerical apertures, for example, silica fiber and plastic optical fiber (POF) with an angular misalignment. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 43: 231–234, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20427 [ABSTRACT FROM AUTHOR]

A simple method is presented to approximate the coupling efficiency in optical interconnection systems, which are affected by alignment parameters of various optical elements. The method considers geometric effects of alignment parameters, not considering the material-dependent losses which are insensitive to the misalignment parameters. To indicate the independent contribution of a given alignment parameter, we define a partial coupling efficiency (PCE) that reflects the effect of only one parameter on a local coupling efficiency at an optical element. The total coupling efficiency (TCE) in the whole system is approximated by multiplications of the PCEs calculated for each parameter and normalization factors. For an interconnection scheme using a 45°-ended waveguide, we demonstrate by considering many misalignment parameters simultaneously that our approximation is well matched to the results of the simulated TCE. [Copyright &y& Elsevier]

A detailed study of a platform of ultra-small photonic large-scale integrated circuits was conducted. Bandgap structure calculations of silicon-on-insulator (SOI) based photonic crystals have been investigated. The photonic crystal consists of dielectric cylinders in air. Using the band structure calculations we obtained design parameters for the proposed structures. The coupling between the photonic crystal and a waveguide fabricated from SOI system has been analysed. It is shown that the optical coupling is improved by interfacing different types of spot-size converters (SSCs) between the SOI waveguide and the photonic crystal. Also, the possibility and limitations of silicon doped germanium and SOI photonic crystals to analyse the light guiding in the third dimension is discussed. [ABSTRACT FROM AUTHOR]

In this paper, a new architecture for a chip-to-chip optical interconnection system is demonstrated that can be applied in a waveguide-embedded optical printed circuit board (PCB). The experiment used 45°-ended optical connection rods as a medium to guide light paths perpendicularly between vertical-cavity surface-emitting lasers (VCSELs), or photodiodes (PDs) and a waveguide. A polymer film of multimode waveguides with cores of 100×65 μm was sandwiched between conventional PCBs. Via holes were made with a diameter of about 140 μm by CO2-laser drilling through the PCB and the waveguide. Optical connection rods were made of a multimode silica fiber ribbon segment with a core diameter of 62.5 and 100 μm. One end of the fiber segment was cut 45° and the other end 90° by a mechanical polishing method. These fiber rods were inserted into the via holes formed in the PCB, adjusting the insertion depth to locate the 45° end of rods near the waveguide cores. From this interconnection system, a total coupling efficiency of about -8 dB was achieved between VCSELs and PDs through connection rods and a 2.5 Gb/s × 12-ch data link demonstrated through waveguides with a channel pitch of 250 μm in the optical PCB. [ABSTRACT FROM PUBLISHER]

An I/O bandwidth commensurate with a dramatically increasing on-chip computational capability is highly desirable. Achieving this goal using board-level copper interconnects in the future will become increasingly challenging owing to severe increase in high-frequency, skin-effect and dielectric loss, noise due to crosstalk, impedance mismatch, and package reflections. The solutions designed to overcome these deleterious effects require complex signal processing at the interconnect endpoints, which results in a larger power and area requirement. Optical interconnects offer a powerful alternative, potentially at a lower power. Prior work in comparing the two technologies has entailed overly simplified assumptions pertaining to either the optical or the electrical system. In this paper, we draw a more realistic power comparison with respect to the relevant parameters such as bandwidth, interconnect length and bit error rate (BER) by capturing the essential complexity in both types of interconnect systems. At the same time, we preserve the simplicity by using mostly analytical models, verified by SPICE simulations where possible. We also identify critical device and system parameters, which have a large effect on power dissipation in each type of interconnect, while quantifying the severity of their impact. For optical interconnect, these parameters are detector and modulator capacitance, responsivity, coupling efficiency and modulator type; whereas, in the case of electrical system, the critical parameters include receiver sensitivity/offset and impedance mismatch. Toward this end, we first present an optimization scheme to minimize optical interconnect power and quantify its performance as a function of future technology nodes. Next, on the electrical interconnect side, we examine the power dissipation of a state-of-the-art electrical interconnect, which uses simultaneous bidirectional signaling with transmitter equalization and on-chip noise cancellation. Finally, we draw extensive comparisons between optical and electrical interconnects. As an example, for bandwidth of 6 Gb/s at 100 nm technology node, lengths greater than the critical length of about 43 cm yields lower power in optical interconnects. This length becomes lower (making optics more favo- rable) with higher data rates and lower bit error rate requirement. [ABSTRACT FROM PUBLISHER]

This paper proposes a new scheme of a tapered hyperbolic-end fiber (THEF) microlens for efficient coupling between laser diode and single-mode fiber. The THEFs were fabricated by symmetrically tapering the fiber during the etching process and hyperbolically lensing the tip during the fusing process. The hyperbolic microlenses of the THEFs have demonstrated up to 82% coupling efficiency for a laser with an aspect ratio of 1:1.5. The influence of tapering asymmetry on the coupling has also been investigated experimentally and theoretically. The axially symmetrical tapered microlenses of the THEFs showed far-field profiles well approximated by a Gaussian profile, while the asymmetric taper deviated significantly from a Gaussian profile. The coupling efficiency for both symmetrical and asymmetrical microlenses were calculated based on the Fresnel diffraction theory and the results were in good agreement with the measurements. This study makes it possible to fabricate the hyperbolic microlenses using unique etching and fusion techniques that result in a more than 2 dB improvement in coupling efficiency when compared to the currently available hemispherical microlenses. [ABSTRACT FROM PUBLISHER]

This paper proposes a new scheme for the lensed fiber employing a quadrangular-pyramid-shaped fiber endface (QPSFE) for coupling between the high-power 980-nm laser diodes and the single-mode fibers (SMFs). The QPSFE was fabricated by grinding and polishing techniques and then heating in a fusing splicer to form an elliptical microlens endface. A coupling efficiency of 83% has been demonstrated. Based on the far-field profile measurements, the higher coupling efficiency of the QPSFE lensed fiber was attributed to the better matching of both the elliptical Gaussian field distribution and the aspect ratio between the laser source and the fiber lens, The advantage of the QPSFE structure was to be able to control two axial curvatures, and, therefore, this novel QPSFE can form any different aspect ratios of elliptical microlenses to match the far field of the high-power diode lasers as well as the commercial diode lasers used in lightwave communications. [ABSTRACT FROM PUBLISHER]

The design and fabrication of an electrostatic MEMS variable optical attenuator (VOA) is described. The VOA is a reflection type with a folded micromirror actuated by a comb-drive actuator. The VOA is fabricated by a simple single-mask process. One photolithography and subsequent deep silicon reactive ion etching define all the microstructures of the VOA. The folded micromirror structure can reduce the overall size of the device by enabling the parallel alignment of an input fiber and an output fiber. Lensed fibers are used to maximize the coupling efficiency and the ease of assembly. The electrooptic characteristics and dynamic characteristics of fabricated VOA are measured. The initial insertion loss is 0.5 dB at 1550 nm and the maximum attenuation is 45 dB, respectively. The polarization dependent loss is measured to be 0.2 dB at 20-dB attenuation. The response time for maximum attenuation is less than 5 ms. [ABSTRACT FROM PUBLISHER]

In this paper, we present a simple analysis, utilising the ABCD transformation matrix method, to analyze and determine the coupling efficiency and misalignment tolerances between a laser diode and a conically lensed fibre. The calculated and measured results, that is, the coupling efficiencies and transverse misalignments, were compared for microlenses etched at 20, 30, and 40 min. The calculated results agree well with the measured values. The angular misalignments are also calculated to determine their tolerances. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 40: 191–195, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11325 [ABSTRACT FROM AUTHOR]

We propose an approach to optical wave field spot-size conversion that uses a waveguide structure. An optical wave field is decomposed with a Hermite-Gaussian basis, and we describe its motion with partial differential equations for the field radius and center parameters derived from the propagation of the lower order components. We use the equations to design a spot-size conversion waveguide structure for expanding and reducing a field spot as an example in a quasi-single-mode optical waveguide. [ABSTRACT FROM PUBLISHER]

Two approaches, i.e., a diffraction model considering Fresnel reflection and a paraxial beam propagation method are utilized to optimize the design of wedge-shaped lensed fibers for coupling between laser diodes of highly asymmetrical beam and single-mode fibers. It is demonstrated for the first time that, in contrast to the prevailing view, the non-Gaussian fiber-mode shape modification by the wedged fiber tip greatly reduces the coupling efficiency when the wedge angle is relatively large, while the Fresnel reflection is found to play an insignificant role. The fundamental cause of the non-Gaussian shape effect is fully explored and, consequently, a novel design is proposed to suppress this effect and increase coupling efficiency. Moreover, the novel design is relatively simple, and it does not complicate the fiber tip fabrication process. [ABSTRACT FROM PUBLISHER]

High-Q semiconductor microdisk resonators laterally coupled to optical waveguides serve as compact and robust components in wavelength-division-multiplexing systems. We present an efficient algorithm for the two-dimensional design of wavelength-selective filters based on waveguide-coupled whispering-gallery-mode (WGM) microresonators of arbitrary cross-sectional shape. A full-wave integral equation formulation enables us to accurately account for the coupling between the resonator and bus waveguide as well as for radiation and material losses. Furthermore, we apply this approach to the analysis of elliptic-resonator filters. Filter tuning by changing the resonator shape from circular to elliptic reduces the dependence of the coupling efficiency on the width of the air gap. Two alternative coupling designs are suggested for monolithic and hybrid integration technologies. One is based on increasing the coupling length, while the other exploits the field concentration at the increased-curvature portion of the deformed WGM resonator. [ABSTRACT FROM PUBLISHER]

Vertical-cavity semiconductor optical amplifiers (VCSOAs) are interesting devices because of their small form factor, potential low manufacturing cost, high coupling efficiency to optical fiber, and polarization-independent gain. In this paper, we present an overview of the properties of VCSOAs, as well as emerging applications for this new class of devices. We present general design rules and analyze how the mirror reflectivity affects the properties of the VCSOA. Experimental results of carrier-confined, optically pumped VCSOAs operating at 1.3-μm wavelength are presented. The devices were fabricated by wafer bonding high-quality AlGaAs distributed Bragg reflectors (DBRs) to an InGaAsP/InP active region. A carrier-confining structure was formed on the active region before the top mirror was bonded to the sample. These VCSOAs show the highest fiber-to-fiber gain (17 dB) and the lowest noise figure (6.1 dB) of any long-wavelength VCSOAs to date. VCSOAs should find applications as low-cost, single-channel amplifiers, amplifying filters, amplifying switches or modulators, as well as in two-dimensional array applications such as optical interconnects. We demonstrate the use of VCSOAs for optical preamplification at 10 Gb/s. Using an 11-dB gain VCSOA, the sensitivity of a regular p-i-n detector was increased by 7 dB resulting in a receiver sensitivity of -26.2 dBm. [ABSTRACT FROM PUBLISHER]

Significant opportunities are emerging for optical interconnections at the board, module, and chip level if compact, low loss, high data rate optical interconnections can be integrated into these electrical interconnection systems. This paper describes an integration process for creating optical interconnections which can be integrated in a postprocessing format onto standard boards, modules, and integrated circuits. These optical interconnections utilize active thin-film optoelectronic components embedded in waveguides, which are integrated onto or into the interconnection substrate, thus providing an electrical output on the substrate from an optical interconnection. These embedded optical interconnections are reported herein using BCB (Benzocyclobutene ) polymer optical waveguides in two different formats, as well as a third waveguide structure using a BCB cladding with an Ultem core. All of these waveguides were fabricated with InGaAs-based thin-film inverted metal-semiconductor-metal (I-MSM) photodetectors embedded in the waveguide layer, thus eliminating the need for beam turning elements at the output of the waveguide. These embedded interconnections have been fabricated and tested, and the coupling efficiency of the optical signals from the waveguides to the embedded photodetectors was estimated from these measurements. These measurement-based estimates are then compared to theoretical models of the coupling efficiency. Using the theoretical coupling efficiency model, variable coupling can be engineered into the interconnect design, thus enabling partial coupling for arrays of photodetectors embedded in waveguide interconnections. [ABSTRACT FROM PUBLISHER]

When optical fibers are used for delivery and collection of light, two major factors affect the measurement of collected light: 1) light transport in the medium from the source to the detection fiber and 2) light coupling to the optical fiber (which depends on the angular distribution of photons entering the fiber). This paper studies the latter factor, describing how the efficiency of the coupling depends on the optical properties of the sample. The coupling dependence on optical properties is verified by comparing experimental data to a simple diffusion model and to a Monte Carlo (MC)-corrected diffusion model. Mean square errors were 7.9% and 1.4% between experiments and the diffusion, and experiments and the MC-corrected models, respectively. The efficiency of coupling was shown to be highly dependent on the numerical aperture (NA) of the optical fiber. However, for lower scattering, such as in soft tissues, the efficiency of coupling could vary two- and threefold from that predicted by fiber NA. The collection efficiency can be used as a practical guide for choosing optical fiber-based systems for biomedical applications. [ABSTRACT FROM PUBLISHER]

In this paper, a new micro-optical system for VCSEL-to-fiber active alignment is described. An integrated microsystem platform, which has a thermally-actuated micromirror, a silicon etched v-groove and flip-chip function, is successfully fabricated and actuated for beam adjustment from a vertical-cavity surface-emitting laser (VCSEL) to a fiber. The micro-optical system has 4.0° maximum beam steering angle with the resolution of 0.08°/mA. With the steering angle reaching 2.5°, the coupling efficiency from the VCSEL to the fiber improves to more than 80% from 9% initial efficiency of 25 μm misaligned fiber position. [Copyright &y& Elsevier]

The wave propagation through a photonic crystal with a triangular lattice of air holes realized in the InP-InGaAsP heterostructure are studied theoretically for the transverse magnetic modes. The photonic crystal possesses a negative refractive index, and the self-focus of the beam is successfully observed. The weak side beams are observed due to high-order Bloch waves in the photonic crystal. The coupling efficiency for the outgoing waves to a waveguide is also studied. [ABSTRACT FROM PUBLISHER]