Resonant grating waveguide structures (GWS) are candidates for extreme narrow line reflection filters. In contrast to conventional dielectric mirror designs, a GWS may be composed from a single high refractive index film with a diffraction grating on top or bottom. In the high-refractive index film, a guided-mode resonance mechanism may theoretically lead to 100% reflection efficiency, while the system is only merely reflective off-resonance. The theoretical treatment of these systems is complicated because it combines optical interference coatings theory with the theory of diffraction gratings. Hence, typical thin film design programs are at stake here and must be replaced by grating solver software, which performs these calculations within the rigorous coupled wave approximation (RCWA), but is not always convenient for reverse search tasks, among them the system design. We derived approximation formulae that allow to analytically estimate film thickness and grating period necessary for a required peak reflection wavelength, assuming a vanishingly small grating profile depth. The estimation formulae work for normal as well as oblique incidence and both types of light polarization. In addition to all-dielectric GWS, we discussed the case of a GWS with metal components. In this case, instead of selective high reflectivity, the system woks as a selective high absorber. The derived formulae allow a straightforward and simple estimation of the film thickness for any resonant GWS. All results have been confirmed with RCWA-calculations and first experimental data. We discuss the merit of peak wavelength and width estimation, as well as the effects caused by absorption of the high refractive index film material.

Air trench structure for reduced-size bends in low (Δn=0.01-0.1) and medium (Δn=0.1-0.3) index contrast waveguides is proposed. Local high index contrast at bends is achieved by introducing air trenches. An air trench bend consists of cladding tapers to avoid junction loss, providing adiabatic mode shaping between low and high index contrast regions. Drastic reduction in effective bend radius is achieved. We present FDTD simulations of bends in representative silica index contrasts, fabrication scheme and waveguide loss measurement results using Fabry-Perot loss measurement technique. We employed CMOS compatible processes to realize air trench bends and T-splitters to achieve low production cost and high yield. A simple, compact waveguide and T-splitter are fabricated and evaluated. The loss measurement results show that losses are consistent with theoretical simulations. By using air trench waveguides, other applications such as BioMEMS (e.g. Evanescent-field sensor) or EDWA can be realized.

Lithium Niobate is an important material in optical communication due to its special characteristics (high electrooptic coefficients and high optical transparency in the near infrared wavelengths). In this paper, we investigated the effects of 775-nm, femtosecond laser radiation on the Lithium Niobate crystal. By focusing the laser beam through a microscope objective, a certain refractive index change may be induced in Lithium Niobate substrate. Based on this effect, channel waveguides and other waveguide structures were fabricated. The output optical fields through them were measured, and the refractive index change of ~6×10^-4 was calculated with the Near-field Method. The properties of these waveguide structures were discussed. We also investigated the waveguides effect induced with different fabrication conditions. The experimental results revealed that different fabrication conditions affect the waveguide effect greatly.

In this study, the sol-gel process to fabricate directly UV-photopatternable lanthanum-doped lead zirconate titanate (PLZT) films was investigated. Photosensitive films were obtained via chemical methacrylic acid modification of metal organic PLZT precursors. Spin-on deposited films were patterned using direct UV-photolithography process. Patterned films were annealed in air, in order to obtain perovskite type crystalline material. AFM and XRD techniques were used for the characterization of the material and fabricated structures. The sol-gel processed PLZT films had good crystallinity, they were crack-free, and had low surface roughness. The films exhibit electro-optic effect being therefore interesting to be used in active integrated optic devices.

Device parameters, like center frequency, polarization dependent loss (PDL), and optical crosstalk in silica-based waveguide device, are determined by the refractive index (RI) and its uniformity across the wafer, thermal expansion coefficient (TCE), and biaxial elastic modulus of silica film. In this study the optical and thermo-mechanical properties of plasma enhanced CVD silica films with different compositions were investigated before and after thermal annealing. RI of deposited films decreased sharply with N₂O/SiH₄ ratio up to 40, and increased slowly when this ratio was larger than 60. The minimum RI of deposited film was found slightly higher than that of thermal oxide. CTE and elastic modulus of silica film were obtained by measuring the film stress with temperature. Growth stresses of deposited films were increased with N₂O/SiH₄ ratio. Due to the porous structure, the CTE and elastic modulus of deposited films at low temperature range (<400°C) were different from those of pure silica. Sharp rise in stress due to gas evolution from film was observed around 500°C. The amount of stress increase and the origin of evolved gas are dependent on the film composition. When silica films were fully annealed (1100°C for 4hour), their CTE and elastic modulus were the same as those of thermal oxide. Upon annealing at high temperature (~800°C), however, cracks were generated on sub-oxide film, which was deposited at low N₂O/SiH₄ ratio. RI of annealed films changed with the composition of deposited film, the annealing temperature, and the cooling rate after anneal.

The microdisk based devices principle of operation is presented. The advantages of analytical approach to design with accuracy this kind of structure are discussed. Problems caused by a random roughness on the microdisk periphery are also introduced. It is also shown that a periodic roughness such as a microgear structure can significantly increase the quality factor for some specifically chosen modes. Different design to extract the light from the resonator are presented. The case of a microdisk and waveguide output coupler is better developed. Through new analytical modeling based on perturbation theory, the effect of the interaction between a channel waveguide and a microdisk is indeed presented showing a fast and efficient approach to design such couplers.

We present the state of the art for commercial design and simulation software in the 'front end' of photonic circuit design. One recent advance is to extend the flexibility of the software by using more than one numerical technique on the same optical circuit. There are a number of popular and proven techniques for analysis of photonic devices. Examples of these techniques include the Beam Propagation Method (BPM), the Coupled Mode Theory (CMT), and the Finite Difference Time Domain (FDTD) method. For larger photonic circuits, it may not be practical to analyze the whole circuit by any one of these methods alone, but often some smaller part of the circuit lends itself to at least one of these standard techniques. Later the whole problem can be analyzed on a unified platform. This kind of approach can enable analysis for cases that would otherwise be cumbersome, or even impossible. We demonstrate solutions for more complex structures ranging from the sub-component layout, through the entire device characterization, to the mask layout and its editing. We also present recent advances in the above well established techniques. This includes the analysis of nano-particles, metals, and non-linear materials by FDTD, photonic crystal design and analysis, and improved models for high concentration Er/Yb co-doped glass waveguide amplifiers.

An overview of the present silicon-on-insulator (SOI) waveguide technology is given and supplemented with an extensive set of theory and simulation results. Characteristics of slab-, rectangular- and ridge waveguides in SOI are explained. In particular, the number of modes and the single-mode conditions are carefully analyzed. Experimental work with straight and bent 8 to 10 μm thick SOI ridge waveguides and a very fast thermo-optical switch are reported. Propagation loss in a very long spiral waveguide down to 0.3 dB/cm, waveguide birefringence below 10^-4, and a switching frequency up to 167 kHz were obtained. A very promising multi-step patterning principle for SOI waveguides is described together with many practical application examples.

A dual-channel, integrated, multiplexer, based on holographic Bragg reflector (HBR) devices and exhibiting flat-top, 4-nm-wide channels is demonstrated. Theory calibrated by the achieved performance indicates that HBR waveguide grating devices can be implemented to provide fully integrated and high performance multiplexer solutions for CWDM and FTTH applications. The enabling HBR devices can be regarded as mode-specific photonic crystals, i.e. photonic crystals whose spatial structure is tailored to interact with a specific signal mode or a very narrow range of such modes. Unlike standard bandgap-based photonic crystals, mode-specific photonic crystals may be effectively implemented with low-refractive-index-contrast and hence low-loss materials.

A shape-from-shading algorithm is applied to topography images of silica waveguide sidewalls coming from a Scanning Electron Microscope. The approach is found appropriate to restitute the sidewall profile. The reconstructed relief obtained is then height calibrated via Line Edge Roughness measurement. The technique enables thereafter roughness measurement at arbitrary positions on the sidewall, with the advantage of providing non-destructive testing on full wafer.

We present the design and fabrication process for an AlGaAs optical frequency conversion device based on tightly confining waveguides and a Photonic Bandgap Crystal Microcavity. We first theoretically analyze the improvement in non-linear conversion efficiency due to a high confinement cavity, compared to traditional QPM waveguides. The theoretical analysis is supported by finite difference frequency and time domain simulations. The theoretical conversion efficiency estimated with these tools is ~4%/mW for a device ~10 μm long. Influence of sidewall roughness on the Q of the cavity is also analyzed. Then, we describe the fabrication process of our device, which involves molecular beam epitaxy, electron beam lithography and plasma etching.

An elastic beam of waves in the Megahertz range, generated using a PZT ceramic, crosses one arm of an integrated Mac-Zehnder interferometer realised by ion-exchange in a glass substrate. Elastic waves modify locally the refractive index of glass. A laser beam of 0.83 μm wavelength is injected into the interferometer. For a sine excitation voltage of 7 volts of the piezoelectric transducer, the variation of the optical intensity measured at the interferometer output is greater than 20% of the intensity observed without elastic waves. Refractive index variation of 9.4×10^-7 were obtained. The optical intensity observed at the output of the interferometer varies at the frequency of the piezoelectric crystal excitation. A model taking into account the elastic and the optical effects is proposed. This model allows the optimisation of the piezoelectric transducer in order to obtain the maximum of elastic strain at the position of the optical waveguides. The theoretical results obtained with the model are in accordance with the experimental results.

Design details and performance data are presented for (Al,Ga)As and polymeric monolithic tapered rib waveguides achieving modal spot-size transformation for mode-matching from a variety of devices to single-mode optical fiber. 2D expanded output modes of waveguide modulators and lasers are achieved using 1D and 2D tapers between non-critical initial and final widths well suited for optical lithography.

The use of multimode interference (MMI) structures within Mach-Zehnder configurations have showed some promise for switching and power splitting functions in integrated optics circuits. In this paper a matrix model is presented that can aid in assessing the switching and power-splitting capabilities of these structures. The paper also examines some of the factors that may limit the performance of these devices when high port counts are attempted.

This paper presents the realization and characterization of ultra narrow linewidth DFB lasers realized by ion-exchange on Er/Yb codoped glass substrates. Output power characteristics such as power efficiency and relative intensity noise are presented. Spectral behavior such as linewidth, wavelength stability versus temperature and emission wavelength calibration are also investigated. Indeed, a fully connectorized DFB with 4.5 mW output power and a 3 kHz narrow linewidth is presented.

For the development of future agile photonic networks, integrated photonic technology will play a crucial role. A particular concern is the need for integration of both active and passive components at the chip level. Through simulation and fabrication results, a study on a hybrid device based on ion-exchanged waveguides and III-V active material is presented.

A novel semiconductor-fiber laser is proposed that would greatly reduce the alignment and packaging complexity of fiber-coupled semiconductor laser systems. As opposed to conventional butt-coupled edge-emitter/fiber packages, these new devices use the evanescent light to efficiently couple light between the fiber and the semiconductor waveguide. Here, an Anti-Resonant Reflective Optical Waveguide (ARROW) is fabricated on an MBE-grown GaAs wafer and is designed to resonate with the mode of the fiber at the operating wavelength. The coupling mechanism provides an inherent wavelength filter that would allow single-mode operation of the laser, without any Bragg grating. Part of the laser cavity and one of the laser mirrors are located in the fiber while the active region and the other mirror are realized in the semiconductor. Simulations of various performance parameters of these devices and the fabrication processes will be described. Initial experimental data will also be presented.

We propose a simple procedure to design a structure that integrates spectral and polarization filters on a single chip. A simulation using rigorous coupled wave anlysis shows that structural adjustment based on the effective medium theory can achieve the desired integration without notable performance degradation. Our spectro-polarimetric filter design maintains spectral filter characteristics, while its extinction ratio is significantly enhanced over the passband. Based on the proposed spectro-polarimetric filter, we plan to build multispectral multipolarimetric filters for remote sensing applications such as to improve forest resource management.

In signal and system analysis, the concept of convolution is very important. It can be implemented optically using non-linear-optic effects by interacting, or mixing, two contra-directed surface waves in the non-linear thin-film photonic crystal waveguide. Complex electric field amplitudes are derived using Maxwell's equations that take the polarization into account and general solutions are then found by using the Variation of Parameters method. In reality, it is the non-linear part of the polarization that allows the mixing of two surface waves to generate a third wave. In order for this optical mixing process to take place effectively, both frequency- and phase-matching conditions must be satisfied. Both collinear and non-collinear interactions are being considered. All derived electric field amplitudes are intensities that may be regarded as signals. Convolution may then be implemented using the above non-linear-optic effects. Because predicted signals are often discussed in terms of their Fourier transforms, the convolution concept is being studied in both frequency- and time-domains. Convolution kernels are being looked into graphically and the convoluted wave is being analyzed according to the Convolution theorem and the Input-Output Description of a system. Finally, the optical implementation of the Fourier transform using a lens is briefly looked into.

We propose the double-side dual hologram reconstruction scheme which can simultaneously read out holograms using both the forward and phase conjugate reference beams, and demonstrate stereo image recording and playback by the holographic memory system. This system is composed of a stereoscopic camera obtained stereo image pairs, holographic data storage where stereo images are recorded in the usual manner but read out by double-side dual reconstruction, and a stereo monitor that use polarized light techniques. As a result, stereo digital pages, which are reconstructed by the proposed double-side dual reconstruction method, can be obtained with very low cross talk noise, and the estimated raw BER of retrieved holograms were approximately 3.59×10^-4 (left image) and 5.0×10^-4 (right image), respectively.

An InGaAsP/InP superluminescent diode (SLD) emitting at 1.55 um has been fabricated by the metal organic vapor deposition (MOCVD) and liquid phase epitaxy (LPE) equipments. Lasing is effectively suppressed by incorporating a bent absorbing guide structure for SLD operation. The fabricated SLD has an optical power of 4mW at an injection current of 200 mA. The spectral width of the SLD is 40 nm at the same current.

In this work, silicon oxynitride (SiO_xN_y) films with different chemical compositions were deposited by plasma enhanced chemical vapor deposition (PECVD) technique and used as core and cladding in optical slab and strip waveguides in order to obtain high quality optical devices with low attenuations. The refractive index and optical loss measurements of the PECVD SiO_xN_y-based waveguides were obtained by a prism coupler system. On the other hand, etching experiments, using a Reactive Ion Etching (RIE) system, were also accomplished in order to define vertical walls on optical strip waveguide structures. The results of the optical characterizations showed that it is possible to obtain slab waveguides with optical loss as low as 0.4 dB/cm depending on the chemical composition of the core and cladding layers. In this way, the feasibility of using SiO_xN_y films for the fabrication of optical waveguide structures is demonstrated.

The titled method has been systematically studied to improve existing alignment control difficulties between optical components to be coupled. Using UV curable resin as a waveguide material, UV cured optical waveguide is “self-written” by UV exposure from an edge of optical fiber. So far we have shown that this method is very effective for optical fibers coupling under existence of gap and offset. We tried here to couple different optical circuit using polymer optical waveguide. One key technique to produce a self-written waveguide from a polymer waveguide is to use visible light curable resin instead of so far used UV curable resin in which self-written waveguide hardly forms because of strong UV absorption of the polymer waveguide. Similar coupling loss is also obtained for polymer waveguide/optical fiber coupling as well as so far studied optical fibers coupling. Clad stabilizing process in the optical fiber coupling is also optimized to decrease coupling loss. The obtained coupling loss is less than 1 dB for 500 um gap; the value is significantly lower than the previously reported value, > 2 dB. Using this unique and easy coupling method, significant cost reduction can be expected in optical coupling procedure.