This PDF file contains the front matter associated with SPIE Proceedings Voume 7366, including Title Page, Copyright information, Table of Contents, Introduction (if any), and the Conference Committee listing.

Silicon Photonics is a field that has seen rapid growth and dramatic changes in the past 5 years. According to the MIT Communications Technology Roadmap [1], which aims to establish a common architecture platform across market sectors with a potential $20B in annual revenue, silicon photonics is among the top ten emerging technologies. This has in part been a consequence of the recent involvement of large semiconductor companies around the world, particularly in the USA. Significant investment in the technology has also followed in Japan, Korea, and in the European Union. Low cost is a key driver, so it is imperative to pursue technologies that are mass-producible. Therefore, Silicon Photonics continues to progress at a rapid rate. This paper will describe some of the work of the Silicon Photonics Group at the University of Surrey in the UK. The work is concerned with the sequential development of a series of components for silicon photonic optical circuits, and some of the components are discussed here. In particular the paper will present work on optical waveguides, optical filters, modulators, and lifetime modification of carriers generated by two photon absorption, to improve the performance of Raman amplifiers in silicon.

In this invited paper, we will first discuss the recent research progress regarding silicon-on-insulator (SOI) Raman wavelength converters, the working principle of which is based on the four-wave mixing process of coherent anti-Stokes Raman scattering (CARS). Next, we will present our research results on other aspects of CARS in SOI waveguides. First, starting from the basic formalism for CARS we will show that, in contrast to what most scientists believe, CARS exchanges energy with the Raman medium in which it takes place and is even able to extract energy (i.e. extract phonons) from it. Furthermore, we will introduce a novel CARS-based approach to reduce the heat dissipation in Raman lasers due to the quantum defect between pump and lasing photons, and we will numerically demonstrate that with this "CARS-based heat mitigation technique" the quantum-defect heating in SOI waveguide Raman lasers could be reduced with as much as 35%.

Efficient generation of polarized single photons or entangled photon pairs is a crucial requirement for the implementation of quantum key distribution (QKD) systems [1] [2]. In this context, self-organized semiconductor quantum dots (QDs) [3] [4] play a decisive role as they are capable of emitting only one polarized photon at a time using appropriate electrical current injection [5] [6]. Therefore, a single QD embedded in a LED can be used as a single photon source. By tuning the electronic structure it is possible to use QD as source for entangled photons. Resonant cavity-induced enhancement of spontaneous emission and out-coupling efficiency can improve external quantum efficiency of quantum dot based single photon sources dramatically. In order to optimise the device geometry detailed numerical device modelling must be performed. The modelling of the electromagnetic field were done using eigenmode-techniques. The essential design parameters, such as cavity length, aperture diameter, position and thickness were systematically varied. We designed and fabricated optimized resonant cavity light emitting diodes combined with a submicron oxide current aperture, to pump individual InGaAs/GaAs QDs electrically. These devices demonstrates more than ten times increased single photon rate in comparison to the simple LED design. Pulsed correlation measurements demonstrated true single photon emission with g²(0) = 0 at a rate of 1 GHz.

In the last few years, silicon photonics has been characterized by a wide range of applications in several fields, from communications to sensing, from biophotonics to the development of new artificial materials. In this communication, we report a review of the main results obtained in our laboratories in design, fabrication and characterization of new silicon-based optical structures and devices, including metamaterials, photodetectors, raman light amplifiers, and porous silicon based bio-chemical sensors and biochips. Future perspectives in integration of silicon based MEMS and MOEMS are also presented.

Steady state fluorescence (SSF) and photon transmission (PT) techniques were used for studying film formation from TiO₂ and Al₂O₃ covered polystyrene (PS) latex particles. These films were annealed at elevated temperatures in 10 min time intervals above glass transition (T_g) temperature of polystyrene. Fluorescence emission, I_p and transmitted photon, I_tr intensities were measured after each annealing step to monitor the stages of film formation. Films present dramatic increase in both I_tr and I_p above the certain onset temperature called minimum film forming temperature, T₀. Dissolution of annealed PS film, with high TiO₂ content presented a nice, ordered nano-sized ceramic structure, which may predict the construction of nano-layer photonic crystals. It was observed that latex particles are encapsulated above a critical Al₂O₃ content of 33 wt% which corresponds to the critical occupation probability of p_c=0.33 at which the film obey the site-percolation model with a critical exponent of 0.45.

This paper reports on fabrication and characterization of waveguide integrated vertical PIN Ge/Si photodetectors for operation at optical telecommunication wavelengths. The measured -3dB bandwidth of waveguide integrated photodetectors at 1.53 μm wavelength under 4 V reverse bias is 42 GHz.

A vertically illuminated photodetector based on Ge-on-SOI, which operates at 8 Gb/s for reverse bias as low as 0.5 V, is presented. The integrated photodetector also features low dark current and good photogenerated carrier collection efficiency.

Contact lithography with i-line (365 nm) or DUV (248 nm) is widely used in laboratories for prototyping. The achievable line width of 300 nm is sufficient for photonic wires, but a process with larger line width is more controllable. The sidewall roughness induced by the lithography and by the following etching steps results in high optical losses. Thermal oxidation is known to smoothen the silicon surface. The oxidation also consumes silicon, so that the photonic wire will shrink and a wider lithography linewidth can be applied. The silicon dioxide is used as a low loss cladding, which further reduces the refractive index contrast, so that the remaining roughness causes less losses. Single mode silicon nanowires with 500nm by 200nm cross section and optical losses of 2dB/cm were produced. The index contrast is still high enough for small bending radii for highly integrated photonic devices. Sharp branches used in Y-couplers can not be fabricated by this oxidation technique, due to the waveguide shrinkage. 3dB-couplers are easily realized by multimode interference (MMI)-couplers, with the output branches sufficiently apart. Using such couplers, Mach-Zehnder interferometers were fabricated. For electric contacts, the SiO₂-cladding is locally removed and ZnO and Al electrodes are applied. The c-axis of sputtered ZnO grows preferentially perpendicular to the surface, which allows to utilize the electro optic effect.

By measuring the transmission of Biodiesel/Diesel mixtures in the near- and far-infrared wavelength ranges, it is possible to predict the blend level with a high accuracy. Conventional photospectrometers are typically large and expensive and have a performance that often exceeds the requirements for most applications. For automotive applications for example, what counts is size, robustness and most important cost. As a result the miniaturization of the spectrometer can be seen as an attractive implementation of a Biodiesel sensor. Using Silicon-on-Insulator (SOI) this spectrometer miniaturization can be achieved. Due to the large refractive index contrast of the SOI material system, photonic devices can be made very compact. Moreover, they can be manufactured on high-quality SOI substrates using waferscale CMOS fabrication tools, making them cheap for the market. In this paper, we show that it is possible to determine Biodiesel blend levels using an SOI spectrometer-on-a-chip. We demonstrate absorption measurements using spiral shaped waveguides and we also present the spectrometer design for on-chip Biodiesel blend level measurements.

The realization of photonic structures operating at visible and near infrared frequencies is a highly attractive scientific and technological challenge. Since optical fiber innovation, a huge of activity has been performed leading to interesting results, such as optical waveguides and planar lightwave circuits, microphotonic devices, optical microcavities, nanowires, plasmonic structures, and photonic crystals. These systems have opened new possibilities in the field of both basic and applied physics, in a large area covering Information Communication Technologies, Health and Biology, Structural Engineering, and Environment Monitoring Systems. Several materials and techniques are employed to successfully fabricate photonic structures. Concerning materials, Er³⁺-activated silica-based glasses still play an important role, although recently interesting results have been published about fluoride glass-ceramic waveguides. As far as regards the fabrication methods sol-gel route and rf sputtering have proved to be versatile and reliable techniques. In this article we will present a review of some Er³⁺-activated photonic structures fabricated by sol gel route and rf sputtering deposition. In the discussion on the sol-gel approach we focus our attention on the silica-hafnia binary system presenting an overview concerning fabrication protocols and structural, optical and spectroscopic assessment of SiO₂-HfO₂ waveguides activated by Er³⁺ ions. In order to put in evidence the reliability and versatility of the sol-gel route for photonics applications four different confined structures are briefly presented: amorphous waveguides, coated microspheres, monolithic waveguide laser, and core-shell nanospheres. As examples of rf sputtering technique, we will discuss Er³⁺-activated silica-hafnia and silica-germania waveguides, the latter system allowing fabrication of integrated optics structures by UV photo-imprinting. Finally, two examples of photonic crystal structures, one prepared by sol-gel process and the other one fabricated by rf sputtering deposition, will be illustrated.

The work was devoted to the design of advanced plasmonic nanoantennas based on numerical investigation of Surface Plasmon Polariton resonances in noble metal nanoparticles. Their dependence on the nanoparticle shape and size is investigated for an efficient manipulation by SPP strength and excitation wavelength. Local near-field plasmon effects and the impact of SPPs on the directivity of emission in far-field are analyzed simultaneously by means of a boundary integral equation approach. Various particles including the shapes with gaps and sharp tips were investigated in order to select the geometries which permit achieving of strong near-field enhancement. The investigation of crescent moon structures demonstrated the possibility of additional field enhancement because both a gap and sharp tips are realized at the same time. Analysis of all considered noble-metal nanoparticles revealed a mechanism of efficient manipulation by SPPs leading to the design of several highly optimized optical nanoantennas.

We have studied the surface plasmon theory with Bloch's hydrodynamic model. The results of the analysis done by Bloch model have been compared with the ones done with Drude model and the dominant differences between two models in valid frequency range have been shown. The transmittance of the slit embedded in a metal layer has been investigated by these models and the differences have been emphasized. An electron density dependent parameter defined by Bloch model has been used to control the transmission behavior of the light through nano-apertures. A system consisting of a nano-slit formed in a metal layer with a periodically textured surface used for beam focusing has been introduced and how the focusing capacity of the system is controlled by the parameter defined by Bloch model has been shown.

Microcavity optical resonators have been investigated in the last years extensively for possible applications in optical communication (switching, filtering, and multiplexing), to investigate cavity quantum dynamic effects, and for sensor applications. The most recent area of application is bio-sensing. The preferential resonator type in the communication area is the disc resonator, the spherical resonator is the most prominent resonator type in sensing applications and a rapidly growing number of groups are investigating the potential of hollow tube resonators for detecting of bio-agents. Here we will present the concept of resonator arrays as sensing element. Potential fields of application are similar to the single resonator sensor but also beyond. We will give an example of an application that is not accessible for single resonators. We will describe the use of resonator arrays as wavelength sensor and discuss several aspects such as the number of sensing elements or the line width on the performance of such a device.

The lasing characteristics of an erbium doped silica glass microsphere coupled to a tapered fiber are numerically investigated in the third band of the optical fiber communication. In the model, the electromagnetic field profile of the whispering gallery modes (WGMs) traveling in the microsphere is described by means of spherical Bessel functions for the radial dependence and spherical harmonics for the angular dependence, at both pump and signal wavelengths. Moreover, the microsphere laser operation has been simulated by taking into account the rare earth ion emission, via the rate equations, and the coupling with the tapered fiber. A number of simulations have been performed in order to demonstrate the feasibility of the active microspheres to be employed as distributed micro laser sources or to fabricate active microsensors.

We consider single photons propagating along two paths, with the polarization correlated to the path. Two information related aspects of this translational-internal entanglement (TIE) are analyzed: a) Using the polarization to record the path (a "flying detector" scheme), we characterize the tradeoff between path- and phaseinformation. b) We investigate the effects of non-Markovian noise on the two-qubit quantum channel consisting of the photon path and polarization (that are both used to encode information), and suggest noise protection schemes.

We report on visible light emission from Si quantum dot (QD) based optically active microdisk resonators. Room temperature photoluminescence from single microdisks shows the characteristic modal structure of whispering-gallery modes (WGM). Highest quality factors of up to 7000 at visible wavelengths, where Si QDs absorb strongly, have been measured for the first time. Apart from conventional flat and circular resonators, we demonstrate for the first time a new class of active microdisk resonators with out-of-plane bending. In these devices, composed of silicon nitride, Si₃N₄ and Si QD-rich silicon oxide, SiOx, materials, the engineered stress at the interfaces results in bent-up (cup-like) and bent-down (umbrella-like) resonators, depending on which material is used as a top layer. Both type of bent devices support perfectly WGMs and, quite unexpectedly, offer a rich and interesting physics, in particular, the possibility of tuning and enhancing the Q-factor band of WGM modes in bent disks. Generally, the wavelength dispersion of two main different loss-channels, the material absorption and radiative losses, result in a limited bandwidth where the highest Q-factors can be observed (Qband). We show here, that in a bent resonator, with respect to a flat one (same diameter, thickness and amount of Si₃N₄ and SiOx materials in both), the maximum of the Q-factor band blue-shifts by more than 70nm (from 832nm to 760nm). In addition, the absolute maximum of Q-band in a bent resonator is 3-4 times higher than that of the flat disk at the wavelength of 760nm. We explain this phenomenon by a smart interplay between the modified dispersions of material absorption and radiative loss related Q-factors (simultaneous increase of Q_mat and decrease of Q_rad). Importantly, this tuning scheme does not require larger device sizes, but rather utilizes self-adjustment properties of originally stressed resonator core. Remarkably, the bent resonators benefit from unmodified free-spectral range and cleaner WGM spectra due to the absence of higher order mode families.

A silicon microsphere coupled to a silica optical fiber half coupler is excited using a diode laser operating at 1.55 μm. The transmitted and the 90o elastically scattered light signals are modulated with an electrical square wave applied to the silicon microsphere.

Some new experiments leading to observation of multi-photon entanglement will be presented. They utilize multi-pair emissions in a down-conversion crystal. In configurations that avoid interferometric overlaps this leads to a high visibility multi-photon interference. General theoretical results concerning the influence of photon statistics and distinguishability on the interference effects in such experiments is be given. Methods of detection of entanglement in multi-qubit systems, via Bell's theorem and a non-linear generalization of entanglement witnesses, will be presented. Finally it will be shown that multi-photon entanglement can be applied to reduce of communication complexity of some computational tasks.

We report on the application of a simple white light source based on the supercontinuum generation from commercial photonic crystal fibres to confocal fluorescence microscopy and fluorescence lifetime imaging (FLIM) microscopy. The coherent white light can be tuned by varying the wavelength and intensity of the pump, a Ti:Sapphire laser. There are several advantages jn the use of SC sources: spatially coherent white radiation, tuning ranges of approximately 400 nm, high brightness, a robust compact system (potentially all-fibre) and relatively low cost. Being pulsed, SC sources are suitable for FLIM and may be used for multiple excitation.

An integrated ratiometric wavelength monitor consisting of a Y-branch and a pair of symmetrical multimode interference structures (MMI) based on silicon-on-insulator (SOI) is investigated numerically. Two symmetrical MMIs are optimized in terms of width and length to achieve overlapping opposite slope spectral responses. The designed ratiometric structure demonstrates a suitable spectral response for wavelength measurement, with a high resolution over a 100 nm wavelength range.

In recent years the interest in the manipulation of quantum systems has furthered new strategies for maintaining their coherence, continuously threatened by unwanted and uncontrollable interactions with the environment. Photons interact weakly with the surroundings. Even so decoherence may significantly affect their polarization state during the propagation within dispersive media because of the unavoidable presence of more than a single frequency in the envelope of the photon pulse. Here we report on a suppression of the polarization decoherence in a ring cavity obtained by properly retooling for the photon qubit the "bang-bang" protection technique already employed for nuclear spins and nuclear-quadrupole qubits. Our results show that bang-bang control can be profitably extended to all quantum information processes involving flying polarization qubits.

We give a proposal on how to use a piece of two-dimension (2D) nonlinear photonic crystal to generate a polarization entangled source. It provides not only a high stability, but also a high entangled quality and a high intensity. Moreover, our scheme involves only practical experimental conditions and setup, and easy to realize. Therefore, it may have a potential application in the quantum world.

We review experimental and theoretical studies performed on left-handed metamaterials (LHM). The metamaterials exhibit quiet unusual electromagnetic properties such as negative refraction, negative phase velocity, subwavelength focusing, subwavelength cavities and enhanced transmission.

Recent technological advances in the terahertz (THz) region of the electromagnetic spectrum, located midway between microwaves and optical waves, have made possible the development of THz systems for applications such as spectroscopy, sensing, imaging, and communications. The availability of low-loss flexible waveguides for THz waves would represent a key step towards innovative systems and would open the way to novel applications. This paper attempts to give an overview of the experimental and theoretical investigations in this area, from the early parallel-plate metal waveguides to the present photonic crystal fibers.

As they are compatible with on-chip integration, photonic-crystal (PhC) devices operating with slow light represent a promising solution for time-domain processing of optical signals. However, the slow-light transport is strongly impacted by random fabrication fluctuations, such as variations in hole sizes, shapes or locations, and since disorder is regarded as critical in practice, there has been significant effort to determine the induced extrinsic losses. Our current understanding of how does light actually propagate in real photonic-crystal waveguides (PhCWs) relies on perturbation approaches. Although intuitively sound, the latter are only valid in the weak-scattering regime, where the structural imperfections hardly affect the light propagation. Here we introduce a new Bloch mode scattering formalism that overcomes the present limitations of perturbation approaches, since it takes into account the inevitable multiple-scattering that leads to Anderson's localization in such waveguides.

Recent work on an OptoElectronic Integrated Circuit (OEIC), the resonant tunneling diode-laser diode (RTD-LD) has shown that it can act as an optoelectronic voltage controlled oscillator (OVCO). The RTD-LD oscillates because of the negative differential resistance of the RTD and simply providing the RTD-LD with a dc voltage will cause it to oscillate at frequencies determined by both the external components of the circuit and the value of the dc voltage. It has been observed to oscillate at frequencies as high as 2.2GHz and be tunable from 1.8-2.2GHz as the dc voltage is tuned by 0.5V. Both monolithic and hybrid (separate RTD and LD chips) have been investigated. The hybrid RTD-LD has been accurately modeled as a Liénard's oscillator - closely related to the Van der Pol oscillator. The model is a classic of nonlinear systems theory and explains all of the observed operating features that include synchronization and chaotic output. Applications include wireless to optical signal conversion where phase synchronization has been demonstrated to transfer phase modulated signals from the wireless to the optical domain by modulating the RTD-LD OVCO to produce a phase modulated optical sub-carrier.

Technological frontiers between semiconductor technology, packaging, and system design are disappearing. Scaling down geometries [1] alone does not provide improvement of performance, less power, smaller size, and lower cost. It will require "More than Moore" [2] through the tighter integration of system level components at the package level. System-in-Package (SiP) will deliver the efficient use of three dimensions (3D) through innovation in packaging and interconnect technology. A key bottleneck to the implementation of high-performance microelectronic systems, including SiP, is the lack of lowlatency, high-bandwidth, and high density off-chip interconnects. Some of the challenges in achieving high-bandwidth chip-to-chip communication using electrical interconnects include the high losses in the substrate dielectric, reflections and impedance discontinuities, and susceptibility to crosstalk [3]. Obviously, the incentive for the use of photonics to overcome the challenges and leverage low-latency and highbandwidth communication will enable the vision of optical computing within next generation architectures. Supercomputers of today offer sustained performance of more than petaflops, which can be increased by utilizing optical interconnects. Next generation computing architectures are needed with ultra low power consumption; ultra high performance with novel interconnection technologies. In this paper we will discuss a CMOS compatible underlying technology to enable next generation optical computing architectures. By introducing a new optical layer within the 3D SiP, the development of converged microsystems, deployment for next generation optical computing architecture will be leveraged.

The quest for mass replication has established technologies like nanoimprinting via hard stamps or PDMS stamps, where the stamps are usually produced via Electron Beam Lithography (EBL) for applications in the microelectronic industry. On the other hand, nanopatterning with self ordered structures¹ or via holographic patterns provide the basis for large area imprints for applications for example, antireflection coatings based on biomimetic motheyes². In this work we report on a technology for enabling the mass replication of custom-designed and e-beam lithographically prepared structures via establishing novel roll to roll nanoimprint processes for pattern transfer into UV curable pre-polymers. The new nano-fabrication technology is based on the concept of Disposal Master Technology (DMT) capable of patterning areas up to 1 x 1 m² and is suitable for mass volume manufacturing of large area arrays of sub-wavelength photonic elements. As an example to show the potential of the application of the new nanoimprint technologies, we choose the fabrication of a photonic crystal (PhC) structure with integrated light coupling devices for low loss interconnection between PhC lightwave circuits and optical fibre systems. We present two methods for fabrication of nanoimprint lithography stamps in Si substrate. In the first method optimized electron beam lithography (EBL) and lift-off patterning of a 15-nm thick Cr mask, and then the pattern transfer into Si using reacting ion etching (RIE) with SF6 as etch gas. In the first method, we use 200nm of positive resist PMMA 950K for EBL exposure. In this method, resist thickness, exposure dose, development time and parameter for etching have been optimized and a photonic crystal of Si-rods in air was fabricated. In the second method lift-off has not been performed and metal mask has been used as master. The subsequent steps for fabricating the master will be presented in detail.

Electromagnetic beams are subject to spatial spreading as they propagate. We have investigated the light propagation passing through a finite-aperture which is obtained by the two-dimensional square-lattice photonic crystals. It is observed that the beam that is coupled to the free-space by exiting the axicon-shape photonic crystal resists considerably against the diffraction. The inspection of the beam profile in the transverse to the propagation direction reveals the appearance of the side-lobes and we attributed the limited-diffraction beam propagation to these artificially created lobes. We show that an order of magnitude improvement for beating the diffraction length is achievable with axiconshape photonic crystal. The advantages of the presented photonic crystal based axicon over the bulk refractive axicons are the compactness and the integrated nature of the former one in addition to the flexibility of engineering individual unit cells of photonic crystal structure.

Numerous applications in scientific, medical, and military areas demand robust, compact, sensitive, and fast ultraviolet (UV) detection. Our (Al)GaN photodiodes pose high avalanche gain and single-photon detection efficiency that can measure up to these requirements. Inherit advantage of back-illumination in our devices offers an easier integration and layout packaging via flip-chip hybridization for UV focal plane arrays that may find uses from space applications to hostile-agent detection. Thanks to the recent (Al)GaN material optimization, III-Nitrides, known to have fast carrier dynamics and short relaxation times, are employed in (Al)GaN based superlattices that absorb in near-infrared regime. In this work, we explain the origins of our high performance UV APDs, and employ our (Al)GaN material knowledge for intersubband applications. We also discuss the extension of this material engineering into the far infrared, and even the terahertz (THz) region.

X-ray photoelectron spectroscopy (XPS) was used to characterize xHfO₂ - (100-x) SiO₂ (x = 10, 20, 30, 40 mol%) amorphous waveguides and xHfO₂ - (100-x) SiO₂ (x = 10, 20, 30 mol%) glass-ceramic waveguides, doped with 0.3 mol% Er³⁺ ions, and prepared by the sol-gel route. The XPS analysis provided a detailed description of the mechanisms underlying the structural properties of the two different silica-hafnia systems. In particular the effect of the Hf concentration and of the annealing protocol on the material structure were worked out by studying the oxygen, silicon and hafnium core lines. In the case of SiO₂-HfO₂ amorphous waveguides with hafnia concentration ≤ 30 mol%, core lines show the formation of hafnium silicate homogeneously dispersed in the silica matrix. For higher hafnia concentrations the material undergoes a spinodal decomposition with generation of HfO₂ rich domains. In the glass-ceramics the thermal treatments lead to the growth of crystallites also at Hf concentration as low as 10%. Optical, structural and spectroscopic properties of the amorphous and glass-ceramic waveguides are compared and discussed on the basis of the XPS results, allowing us to understand the chemical-physics of the fabricated waveguides, which are characterized by low-losses and by efficient luminescence @ 1.5 μm.

Laser writing of waveguides in bulk glasses opens the opportunity for creating three-dimensional photonic devices. In order to become practical, the numerical aperture (NA) of these waveguides should be significantly higher than currently achievable of 0.1 - 0.15. One reason is that with higher NAs one can decrease the bending radii of the embedded photonic devices without significant loss penalty and make them compact. Thus, femtosecond-laser-written waveguides in glasses do not allow bending radii smaller than 15 - 20 mm. In order to overcome this limitation, we propose to fabricate waveguides in phase-separable and leachable glass where the index contrast is determined by the difference between the refractive indices of the unprocessed glass and of the leached porous glass. We show that we can achieve the NA = 0.25 prior to optimization. Surface and sub-surface treatment with a nanosecond ultraviolet (UV) laser produces a similar effect with even higher NA = 0.35. Applications may include a range of tightly packed embedded and three-dimensional photonic devices in bulk glass like directional couplers, splitters, interferometers, etc.

We report on the fabrication and optical characterization of photonic crystal cavities for visible wavelengths made from silicon nitride (SiN). We note significant improvements in fabrication process with respect to our previous studies. The intrinsic luminescence of the SiN membranes was used as an internal light source to study the quality factor of the cavity modes. We experimentally found values as high as 3400, which are up to the present unsurpassed for photonic crystal resonators in the visible spectra range. Finite difference time domain (FDTD) simulations suggest another boost by a factor of two is possible by further optimizing the fabrication process. We describe a method by which arbitrary emitters or other nanoscopic objects can be coupled in a deterministic way by using the manipulation capabilities of an atomic force microscope.

A novel emerging technique for the label-free analysis of nanoparticles including biomolecules using optical micro cavity resonance of whispering-gallery-type modes is being developed. Schemes of such a method based on microsphere melted by laser on the tip of a standard single mode fiber optical cable with a laser and free microsphere matrix have been developed. Using a calibration principal of ultra high resolution spectroscopy based on such a scheme the method is being transformed to make further development for microbial application. The sensitivity of developed schemes has been tested to refractive index changes by monitoring the magnitude of the whispering gallery modes spectral shift. Water solutions of ethanol, glucose, vitamin C and biotin have been used. Some other schemes using similar principals: stand-alone, array and matrix microsphere resonators, liquid core optical ring resonators are also being under development. The influences of the gap in whispering-gallery modes on energy coupling, resonance quality and frequency have been investigated. An optimum gap for sensing applications has been defined at the half maximum energy coupling where both the Q factor and coupling efficiency are high and the resonance frequency is little affected by the gap variation. Developed schemes have been demonstrated to be a promising technology platform for sensitive, lab-on-chip type sensor which can be used for development of diagnostic tools for different biological molecules, e.g. proteins, oligonucleotides, oligosaccharides, lipids, small molecules, viral particles, cells as well as in different experimental contexts e.g. proteomics, genomics, drug discovery, and membrane studies.

Elastic scattering intensity calculations at 90° and 0° for the transverse electric and transverse magnetic polarized light were performed at 1200nm for a 50 μm radius and 3.5 refractive index silicon microsphere. The mode spacing between morphology dependent resonances was found to be 1.76 nm. The linewidth of the morphology dependent resonances was observed to be 0.02 nm, which leads to a quality factor on the order of 10⁴.

We present photoconductive emitters and detectors for radially and azimuthally polarized terahertz beams. Microstructured electrodes consisting of concentric rings serve as antennas for radially polarized beams. Electrode patterns consisting of radially arranged segments are employed for the antennas for azimuthally polarized beams. A second periodic structure is used to prevent destructive interference of THz wavelets of opposite polarization. Beam profiles are detected for divergent beams in proximity to the emitter as well as for refocused beams. The THz beams have a donut-like intensity distribution and the beam profiles can be quantitatively described as lowest order Bessel- Gauss modes. Furthermore we demonstrate that detection antennas of similar patterning are selective for detection of particular modes.

We present large-area emitters based on GaInAsN which show efficient THz emission for excitation wavelengths up to 1.35 μm. The substrate material consists of a 1000 nm Ga_1-yIn_yAs_1-xN_x (y = 0.11 and x = 0.04) layer grown by molecularbeam epitaxy on semi-insulating GaAs. On top there is an additional GaAs/Al_0.3Ga_0.7As heterostructure with thicknesses of 5 nm for the GaAs and 60 nm for the AlGaAs layer, respectively. Transmission measurements with a Fourier transform spectrometer reveal a bandgap corresponding to a wavelength of 1.5 μm. The resistance of a complete device with an active area of 1 mm² is 0.3 MΩThis allows operation with high bias fields (30 kV/cm) without being limited by heating.

Due to remarkable properties of the chalcogenide glasses (Chgs), especially sulphide glasses, amorphous chalcogenide films should play a motivating role in the development of integrated planar optical circuits and their components. This paper describes the fabrication and properties of optical waveguides of undoped and erbium doped sulphide films obtained by RF magnetron sputtering and laser ablation (PLD). The deposition parameters were adjusted to obtain, from sulphide glass targets with a careful control of their purity, layers with appropriate compositional, morphological, structural characteristics and optical properties. A transmission loss of 0.8 dB/cm can be obtained for rib waveguides produced by dry etching under CF₄ plasma (4-300 μm wide, 5.5 μm film thickness, 1.5 μm etched thickness). The photo-luminescence of erbium doped Ge₂₀Ga₅Sb₁₀S₆₅ films were clearly observed in the n-IR and mid-IR spectral domain. The study of their decay lifetime with a well adapted annealing treatment controlling the roughness variation reached value of the bulk counterpart. Amplification tests were carried out leading to a complete characterisation of the Erbium doped waveguide. Gain on/off of 4.4 dB (3.4 dB/cm) were achieved for a signal at 1.54 μm in multiple modes sulphide:Er waveguides. The first demonstration of photoluminescence in mid-IR in an Er³⁺- doped Chg waveguide could potentially be employed to produce sources or amplifiers operating in the mid-IR.

The reorganization processes at submicron level of the polymeric materials have been investigated because of their applications in optoelectronics and bio-science. We have obtained surface relief modulation in single step processing on the photo resist and polysiloxane films. But for technical applications the time evolution and stability of the induced surface structure is an important parameter and is a problem to be discussed. In case of single step surface relief formation on polymeric materials the process is connected with the photochromic behavior of the materials. As it is known the UV light induced effects on the material structure are reversible under the action of visible light, but with different speeds. In this report is analyzed the time evolution of the surface modulation obtained under the action of the UV light for azopolymers with different structures.

Usually the synthesis of such structures is performed using ion implantation techniques or chemical reaction methods or ablating metal targets inside liquid solutions, while here we propose pulsed laser ablation in vacuum for the generation of these particles without any catalytic environment and annealing procedures for their activation. Silver targets were ablated in a vacuum chamber at (10^-7 Torr) by Nd:YAG high power pulsed laser at room temperature. The consequent deposition on Si-substrates covered by a ~50 nm thick SiO₂ results in the formation of well separated nanometric spheroidal particles of Ag with a diameter of 5-10 nanometers depending on the deposition time. The generation of silver nanoparticles was confirmed by scanning electron microscopy analysis (SEM). The kinetic energy (2 keV) of Ag ions of the non-equilibrium plasma produced by the high power pulse was measured by the aid of Faraday's cup inserted in the interacting chamber. Monte Carlo simulations of ions tracks in solid targets (TRIM) reveal that silver ions are implanted in a region thinner than 10 nm just under the surface. Optical properties of the samples were studied by variable angle ellipsometric spectroscopy (VASE). The ellipsometric spectra were modeled with a 2-layer model. Layer-1 is modeled using the dielectric function of SiO₂ and a variable thickness, while Layer-2 is best modeled with a single Lorenztian-oscillator and a constant layer thickness of 7 nm. The imaginary part of the refractive index for layer-2 reveals an absorption band in the energy range characteristic for surface plasmon resonances (SPR) of Ag nanoparticles. The maximum of SPR shifts 372 nm to 414 nm for longer deposition time indicating an increase of the average particle size [1]. Interestingly, although silver nanoparticles are located within the SiO₂ layer, nanparticle formation occurs during PLD and needs no additional forming or annealing step.

In recent years, infrared light sources have attracted great attention for their application in remote sensing, sensors, optical communication, medical and military technology, and so on. Innovative erbium-doped microstructured optical fiber ring lasers (EDFRLs) have been proposed in order to increase the performance of the conventional fiber lasers, enabling a number of advantages such as smaller size, higher power, better beam quality. In a previous work, the authors proposed a design of a Fabry Perot laser made of a novel erbium-doped Ga₅Ge₂₀Sb₁₀S₆₅ chalcogenide glass, operating in the Mid-IR wavelength range. This work reports the design of a ring laser, made of the same glass, operating at the signal wavelength λ_s = 4600 nm and at the pump wavelength λ_p = 806 nm. The design and optimization has been performed in order to improve the laser performance. The numerical computer code, implemented ad-hoc to investigate the fiber ring laser, takes into account the rate equations of the 5-level erbium ion system, the pump and signal power propagation, the energy transfer of the up-conversion and cross-relaxation phenomena, the cavity losses and the coupling losses. The measured amplified spontaneous emission ASE power spectrum has been accurately sampled in 150 wavelength slots from λ₁=4200 nm to λ₂=4800 nm, to obtain more realistic simulations.

In this work a thermo-optic switch with very low power consumption of less than 1 mW is presented. The switch consists of a Mach-Zehnder-Interferometer whose arms are placed on free-standing SiO₂-membrane cantilevers. The waveguides are monomode nanowires fabricated by DUV-contact lithography having losses of 2 dB/cm. Additionally, a membrane-system to tune the nanowires elasto-optically is shown.

Silicon-on-Insulator (SOI) photonics has become an attractive research topic within the area of integrated optics. This paper aims to fabricate SOI-structures for optical communication applications with lower costs compared to standard fabrication processes as well as to provide a higher flexibility with respect to waveguide and substrate material choice. Amorphous silicon is deposited on thermal oxidized silicon wafers with plasma-enhanced chemical vapor deposition (PECVD). The material is optimized in terms of optical light transmission and refractive index. Different a-Si:H waveguides with low propagation losses are presented. The waveguides were processed with CMOS-compatible fabrication technologies and standard DUV-lithography enabling high volume production. To overcome the large mode-field diameter mismatch between incoupling fiber and sub-μm waveguides three dimensional, amorphous silicon tapers were fabricated with a KOH etched shadow mask for patterning. Using ellipsometric and Raman spectroscopic measurements the material properties as refractive index, layer thickness, crystallinity and material composition were analyzed. Rapid thermal annealing (RTA) experiments of amorphous thin films and rib waveguides were performed aiming to tune the refractive index of the deposited a-Si:H waveguide core layer after deposition.

The potential impact of nanoscience on energy transfer processes in biomolecules was investigated on the example of a complex between fluorescent semiconductor nanocrystals and photochromic membrane protein. The interactions between colloidal CdTe quantum dots (QDs) and bacteriorhodopsin (bR) protein were studied by a variety of spectroscopic techniques, including integrated and time-resolved fluorescence spectroscopies, zeta potential and size measurement, and fluorescence correlation spectroscopy. QDs' luminescence was found to be strongly modulated by bacteriorhodopsin, but in a controllable way. Decreasing emission lifetimes and blue shifts in QDs' emission at increasing protein concentrations suggest that quenching occurs via Förster resonance energy transfer. On the other hand, concave Stern-Volmer plots and sigmoidal photoluminescence quenching curves imply that the self-assembling of NCs and bR exists, and the number of nanocrystals (NCs) per bacteriorhodopsin contributing to energy transfer can be determined from the inflection points of sigmoidal curves. This number was found to be highly dependent not only on the spectral overlap between NC emission and bR absorption bands, but also on nanocrystal surface charge. These results demonstrate the potential of how inorganic nanoscale materials can be employed to improve the generic molecular functions of biomolecules. The observed interactions between CdTe nanocrystals and bacteriorhodopsin can provide the basis for the development of novel functional materials with unique photonic properties and applications in areas such as all-optical switching, photovoltaics and data storage.

Light transmission through circular subwavelength apertures in metallic films with surrounding nanostructures is investigated numerically. Numerical results are obtained with a frequency-domain finite-element method. Convergence of the obtained observables to very low levels of numerical error is demonstrated. Very good agreement to experimental results from the literature is reached, and the utility of the method is demonstrated in the investigation of the influence of geometrical parameters on enhanced transmission through the apertures.

Light initiated liquid polymer quasi-instant solidification is attractive for its ultra precise spatial and temporal control of the reaction. Here we present femtosecond laser induced two-photon photopolymerization for structuring of microoptical and sample photonic devices. Due to nonlinear phenomena the fabrication resolution is not restricted to diffraction limit for the applied laser excitation wavelength but determined by the exposure dose. Furthermore, pinpoint structuring enables one to produce 3D structures of any form out of photopolymer. The smallest structural elements voxels of 200 nm lateral dimensions can be achieved reproducibly by using high numerical aperture optics. Axial resolution which is fundamentally few times worse than lateral can be controlled in few hundred nanometers precision by forming polymeric pad as an additional structure. In our work we applied commercially available and widely used hybrid zirconium-silicon based hybrid sol-gel material ORMOSIL (SZ2080) and an acrylate based AKRE37 photopolymer. Arrays of custom parameters spherical microlenses for microscopy applications have been fabricated. Their surface roughness, focal distance and imaging quality were tested. 3D custom form woodpile structures with submicron period and chain-mail structure were made as a sample photonic bandgap structures. Finally, we show some structures produced out of fluorescent dyes rhodamine 6G doped photopolymer.

The work presented here shows the effect of wavelength conversion experiment on Four Wave Mixing (FWM) by utilising photonic crystal fibre(PCF). This configuration consists of dual pump and a few sets of Fiber Bragg Gratings (FBGs). Selective conversion is also possible by adjusting on one of pump laser. However, phase matching conditions plays vital roles in this experiment. This phenomenon is the major cause of FWM.

The construction of transparent electronic devices based on zinc oxide depend on the availability of high performance p type ZnO. This paper addresses the origin of n type conductivity in undoped ZnO which would require compensation before p-type material is possible. ZnO films were prepared by magnetron sputtering and filtered cathodic arc deposition with and without PIII. The intrinsic free carrier properties of have been analyzed by infrared ellipsometry and temperature dependent conductivity measurements. The correlation of intrinsic carrier density and the crystal size and orientation as assessed by XRD shows that the free carriers originate from charged intrinsic defects. Even an undoped ZnO film with large and well oriented grains can exhibit substantial defect conductivity. Temperature dependent conductivity measurements lead to the conclusion that the charged defect sites give rise to electronic subbands in the band gap. The defect conductivity of undoped ZnO is comparable to values in the literature for Al-doped ZnO.