Fabrication technology and device structures suitable for low- cost production of replicated integrated optical devices are presented and discussed. Shim fabrication and replication techniques such as hot embossing and injection moulding are capable of achieving the submicron resolution, high fidelity requirements of integrated optical structures. Polymeric materials have been shown to be suitable both as replicated substrates and as waveguiding films with losses under 1 dB/cm. High index dielectric waveguiding films are highly suited to sensor applications and have been fabricated with losses under 5 dB/cm. New types of vertically structured integrated optical devices which can be fabricated by replicating a microstructure followed by dielectric coating are presented.

Conventional chromium mask transfer can be used for the photolithographic transfer of high spatial frequency gratings at nonnormal incidence. A systematic study brings the tolerance on the transfer parameters such as proximity, angle of incidence, and line/space ratio.

This paper shows that a direct write laser has completely incoherent properties, even though the light used for illumination is coherent. As a result of this fact it has twice the resolving power of that of a coherent imaging system. Due to the extended depth of focus steep resist walls can be achieved using a direct write system. To demonstrate this exposure on 1.5 micrometers and 2.0 micrometers thick photoresist were made. A multiple- exposure technique is proposed to produce structures consisting of 0.25 micrometers lines and spaces, although the smallest structure which can be exposed is 0.75 micrometers .

In this paper, we will describe our work at Columbia in developing a laser prototyping system, in conjunction with computer simulation, to design, fabricate, and test novel waveguide circuits. The system is also useful for manufacturing small-run circuit designs. The fundamental technique uses a laser-induced photoelectrochemical process for etching GaAs and other III-V compounds. The technique is maskless and discretionary. The computer-controlled apparatus can be programmed with any desired circuit pattern, and prototype waveguide circuits can be produced within a day. The waveguides and passive components produced with this technique include linear waveguides, tapered waveguides, abrupt and smoothly curved bends, Y-branches, asymmetric splitters, directional couplers, and optical delay lines. The passive devices are single-mode and low-loss. The technique also has the ability to vary the effective index of refraction along the device by grading the etch depth. In addition to passive devices, we have recently shown that active switching components can be prototyped by combining passive structures with laser-patterned metal electrodes. These electrodes are produced masklessly using standard metal deposition techniques coupled with laser- patterning of photoresist. In addition, metal can be deposited directly using laser-induced selective metallorgainic CVD.

The paper reviews the application of deep X-ray lithography in conjunction with electroforming, plastic molding, and stamping (LIGA) for a mass production of micro- and submicron-structured photonic devices. LIGA technology offers almost total design freedom in lateral structuring and a high aspect ratio of 100. Vertical walls with heights up to 1 mm and optical grade surfaces enable their use as functional optical surfaces. It is possible to process a variety of materials such as metals and different polymers, including those with nonlinear optical properties. Therefore, Y-branches, couplers, and structures for the positioning and fixing of fibers, detectors, and light emitters can be integrated on one chip to build up hybrid optoelectronic devices.

Laser heating can be used to fully densify selected areas of a partially densified sol-gel film deposited onto a glass substrate, thus substituting the conventional heat treatment in an oven. Here the topographic and optical characteristics of strip waveguides produced in a SiO₂-TiO₂ film by direct writing with a focused CO₂ laser are presented, and the critical parameters of the process discussed.

The microfabrication of optical and micromechanical elements requires a high degree of accuracy in order to obtain the required efficiency in the functionality of the element. An easy, nondestructive 3D characterization of the batch fabricated elements after each fabrication step is needed to ensure a reliable engineering control over the whole process. We demonstrate the versatility of a stand-alone AFM which can be used as a flexible tool for the nondestructive characterization of all steps of a fabrication sequence of microfabricated optical and micromechanical elements without the necessity to specially prepare the samples under test.

New micro-optical devices are presented: a modulated thermal IR source and an electrical controllable micromirror for image formation with an adjustable focal length ranging from (infinity) down to 0.001 m. These integrable thermo-optical devices base on micromechanics and thin film technology. Device fabrication, the physical background, properties, advantages, limitations, especially size effects, and experimental examples are given.

Groove patterns with submicron lateral sizes and depths of several hundreds of nanometers have been defined in silica glass surfaces by focused ion beam implantation and differential wet etching in hydrofluoric acid solutions. Nonperiodic arbitrary patterns can be defined and variable depth achieved through local ion dose control. The fabrication of diffractive optical elements for excimer lasers in the ultraviolet is described.

A new integrated device for coupling light into waveguides or deflecting and focusing the light from waveguide elements is proposed. The device shows flexible design possibilities and compact dimensions. It consists of a combination of a refractive cylindrical microlens and an integrated planar Fresnel zone lens. High coupling efficiencies can be expected by approaching a kinoform profile with multiphase steps. The Fresnel zone lenses and the cylindrical microlenses were fabricated by thin film deposition of SiO_x-multilayers. The measured spot-sizes of the fabricated microlenses are close to the diffraction limited values. A theoretical analysis of coupling tolerances indicates that integrated planar Fresnel zone lens couplers are useful for optical free space interconnects.

A grating fabrication technology has been established for producing DFB- /DBR-grating structures in Er-doped Ti:LiNbO₃ waveguide lasers. It is based on holographically defined resist gratings transferred into the surface of LiNbO₃ waveguides using reactive ion etching with SF₆ gas as the dry etching technique. For a sample with a 24 mm long surface relief grating of 346 nm period, a transmission drop of -11.7 dB, a filter bandwidth as small as 0.08 nm, a Bragg resonance wavelength at 1528.4 nm very close to the Erbium absorption line at 1531 nm and excess losses attributed to the grating of only 1 to 2 dB were measured.

We demonstrate improvements to the double ion-exchange process proposed for the fabrication of synthetic diffractive optical elements in glass waveguides. In this process a potassium slab waveguide is first fabricated. Then the diffractive element is made with silver ion exchange. In the modified process a short silver ion exchange is used in the second process step and the double ion-exchanged waveguide remains single mode. The undesired undiffracted light can be nearly totally eliminated. The mode profile of the potassium and double ion-exchanged waveguides are very close to each other resulting in low coupling loss between these two waveguide regions.

This work is devoted to the investigation of the authors in the field of fabrication of Fresnel lenses and other optical elements with the help of optical methods and registering media on the base of chalcogenide vitreous semiconductors. Developed and investigated are the processes of binary Fresnel lenses fabrication by holographic method, with the consequent transfer of diffraction pattern into the substrate. The results of the investigations of optical elements with blazed profiles fabrication processes are discussed. Most perspective is considered the method of direct recording of optical elements with blazed profiles with the help of sharpfocused laser beam, that enables to obtain kinoform elements with micrometer sizes of distant zones. Methods of additional treatment (wet or dry) enable to obtain the blazed gratings using the initial holographic diffraction gratings with the symmetrical profile, fabricated on the base of chalcogenide layers.

Investigations on input and output grating couplers with asymmetric triangular (blazed) profiles for planar polymer waveguides are reported. With blazed gratings a high outcoupling efficiency into one direction, either substrate or superstrate is achieved. The gratings are written directly into the waveguiding polymer layer by electron beam lithography and are replicated by embossing. Electron dose control across every grating period results in asymmetric blazed corrugation of the grating. Additionally, variation of the electron dose across the whole grating leads to a variable corrugation depth along the grating length. Two types of waveguide gratings were designed and produced, blazed corrugated gratings with constant groove depth and with variable groove depth, respectively. Input efficiencies of about 40% for gratings with constant grating depth were measured. The original gratings were replicated into nickel by electroplating. For a replicated grating we attained an efficiency of the outcoupled light into one diffraction order of about 74%. Waveguide grating couplers with blazed profile and variable grating groove depth are investigated. Thus, the intensity distribution of the outcoupled light can be varied and the field profile was matched to a Gaussian like profile.

A new integrated optical 1:N tap-power-divider is proposed and demonstrated. It is compact, and can tap and divide light at any ratio in an integrated optical system.

A new paradigm for writing long-range, spatially-coherent multiple-quarter-wave shifted Bragg gratings is described. The implementation of such a paradigm is essential for fabricating integrated optical devices for wavelength-division multiplexed applications.

Singlemode strip waveguides at the wavelengths (lambda) equals0.514 micrometers and (lambda) equals0.488 micrometers have been fabricated in potassium titanyl phosphate (KTiOPO₄ or KTP) by rubidium- potassium ion exchange in molten mixtures of RbNO₃/KNO₃/Ba(NO₃)₂. The technological parameters had been chosen by means of theoretical calculations concerning the singlemode region of the effective strip waveguide index N₀₀ at the given wavelength. Measured near field distributions and insertion losses of the strip waveguides led to a typical attenuation of about 2 dB/cm for TM polarization at (lambda) equals0.514 micrometers . The light-induced refractive index changes (photorefractive effect) have been measured as a function of time, wavelength, and optical mode intensity. Electro-optic phase modulators have been successfully investigated concerning dynamic V_pi measurements, the electric-optical field overlap and dc-drift phenomena by using a special interferometric setup based on a two-beam interference of two neighboring strip waveguides.

Antiresonant reflecting optical waveguide (ARROW) structures in strip configuration have been designed and fabricated on a SiON- SiO₂-Si-wafer. The ARROW structures have been calculated by combining the effective index method with the transfer matrix approach and their field distribution by FEM. The width of the reflectors corresponds to the (lambda) /4 layers for the lateral component of the wavevector and, therefore, strips of 0.2 to 0.6 micrometers width are patterned by e-beam direct writing and etched into SiON by RIE. As an application a directional coupler consisting of two parallel strip-ARROWs is realized on the same substrate. The coupling length is a periodic function of the waveguide separation because of the leaky wave mechanism in waveguiding. Remote coupling up to 93 micrometers is demonstrated experimentally.

In this paper, we discuss circular grating surface emitting lasers and review the progress in this field. The theoretical approach to analyze these lasers is mentioned. The fabrication technology to make them is explained. Recent achievements are presented.

Electrochemically etched porous silicon shows luminescence. In this paper, the electroluminescence is investigated. The fabrication and the characterization of a light emitting diode is described.

Aluminum-oxide thermally grown into high Al-concentration Al_xGa_1-xAs layers has recently been studied extensively. The material shows electrical and optical properties that make it useful in a semiconductor laser fabrication process where it can provide electrical isolation and optical guiding, as well as simplify the fabrication and integration process considerably. We use this thermal oxide to produce GaAs/AlGaAs semiconductor lasers that can be integrated with other devices. The GaAs cap- layer is masked with photoresist and the exposed GaAs areas are etched away, leaving a GaAs oxidation mask on the AlGaAs upper cladding layer. Using N₂ carrier gas saturated with H₂O vapor, the uncovered Al_0.8Ga_0.2As material is converted into a stable aluminum-oxide at temperatures around 450 degree(s)C. Due to the near-isotropic oxidation an `ellipsoidal' diffusion front is created, which is in strong contrast to the well-known mesa cross-section in conventional dry-etched ridge-waveguides but is more similar to e.g. wet-etched buried heterostruture lasers.

Semiconductor technology, when applied to the design and fabrication of integrated optical sensors, will yield structures of improved performance and reduced cost. Key advances in this area employ two quantum well-based effects, the quantum confined Stark effect and selective quantum well intermixing, the use of which enable the monolithic integration and enhanced functionality of semiconductor-based optical sensor circuits. In this paper, we discuss the application of these effects to the fabrication of semiconductor devices useful for integrated optical sensors based on waveguide interferometry. The quantum confined Stark effect allows us to electrically define the absorption edge of detectors and permits the fabrication of high- efficiency phase modulators. By the use of different surface dielectrics, quantum well intermixing is employed to generate transparent and absorbing regions on a single substrate. Current and future applications are discussed.

The progress in fabrication of rare-earth doped glass waveguides using two different techniques, ion exchange in a doped glass and sol-gel processing, is reported. A study of the effect of postbake on the coupling efficiency of the pump beam in silver ion-exchanged waveguides made in a commercially available neodymium-doped silicate glass is presented. Upconversion is reported for the first time in a silver ion-exchanged phosphate glass waveguide. A new ion-exchanged glass fabrication process in conjunction with rare-earth-doped sol-gel layers is proposed.

The development of broadband telecommunication networks has led to a growing interest in photonic devices so that monolithic integration on InP material has been intensively studied to get miniaturization, high complexity, advanced functions and consequently cost reduction. We illustrate in this paper the continuous progress that has been done to make technology mature enough for integration through the fabrication of two types of Photonic Integrated Circuits: a 4 X 4 switch matrix and a multifunctional access node switch.

Nonsymmetric three-port integrated optical Mach-Zehnder interferometer configuration is employed to make 0.807/1.3 micrometers , 1.3/1.55 micrometers , and 1.48/1.55 micrometers wavelength multiplexers/demultiplexers. The devices are produced by potassium-silver double-ion exchange process. The effect of thermal post-annealing on spectral behavior of the fabricated devices is investigated. The losses and extinction ratios of the fabricated devices are also determined.

We propose the integration, in a single glass substrate, of a 0.807/1.3 micrometers wavelength multiplexer, a 1.48/1.55 micrometers wavelength multiplexer, and a 1.30/1.55 micrometers wavelength multiplexer followed by a 1/8 splitter by potassium and silver double-ion exchange. The wavelength multiplexers are based on nonsymmetric three-port Mach-Zehnder interferometers, and symmetrical Y-junctions are used for achromatic splitting. The facet-to-facet excess loss in the 0.807/1.3 micrometers and 1.48/1.55 micrometers multiplexers is less than 3 dB and in the integrated 1.30/1.55 micrometers multiplexer and 1/8 splitter less than 2.65 dB. The device can be used, in connection with an Er-doped fiber, in future wavelength division multiplexing subscriber networks, in which amplification is needed at 1.3 micrometers and 1.55 micrometers wavelength regions.

This paper deals with the realization of a 1.3/1.55 micrometers duplexer integrated on a silica on silicon substrate. The design consists of two cascaded directional couplers in order to enhance the rejection bandwidth. Fabrication is based on plasma enhanced chemical vapor deposition and reactive ionic etching of silica films. The channel guide structure has been optimized to comply with the small distance between guides along the coupler, that would still ensure low loss fiber coupling. The results show an excellent spectral response: insertion loss lower than 3 dB on a 150 nm bandwidth at both wavelengths, crosstalk as low as 20 dB on a 100 nm bandwidth. Moreover, quite a total independence on polarization and temperature has been checked, for the required 1.3/1.55 micrometers separation.

A pigtailing process is presented which is based on flip chip assembling and fiber mass preparation. The technique is automated and it is suitable for chips with a high number of ports from several integrated optics technologies. Fast fully passive chip/fibers connection and high performances active pigtailing are demonstrated.

This paper examines two different approaches for grating assisted optical interconnects between waveguides composed of dissimilar materials, i.e. evanescent and projection coupling. For evanescent coupling the waveguides have to be sufficiently close to allow overlap of the optical modes, whereas projection coupling has the advantage of allowing the waveguides to be separated by a much larger distance. In both cases we assume that phase matching is achieved using surface relief gratings. This paper compares the performance of these two methods using theoretical modelling. Results show the effects of nonparallelism with regard to the manufacture of interconnecting networks. For projection coupling an optimal design for the grating structure is proposed which combines high efficiency and device compactness.

The new technology for making the elements and devices of semiconductor integrated optics is presented. We report about creation in the planar diffusion CdSSe-waveguides such integrated optical elements as the channel waveguides, diffractive gratings for input or output of the emission, local waveguide photoresistors and monolith integrated optical device. This technology is based on the phenomenon of the light induced irreversible change (decreasing) of the subsurface layer refractive index of the single crystal that is immersed in high polar liquid at the room temperature under band-to-band absorbed illumination. At the first time this phenomenon was detected by us in CdS-single crystals and called low temperature photohydromodification.

We report on the fabrication of a grid polarizer for the visible spectral region, based on metallic grids with periods below 100 nm. Theoretical calculations of the degree of polarization predict useful values for the visible region, if the period is in the range of 100 nm. The properties of the polarizer are shown to be strongly dependent on the optical constants of the metal and the substrate. For the fabrication of the grids, direct e-beam writing in combination with a dry etching process has been used. Metallic grids with 50 nm lines and a period of 100 nm were fabricated on a glass substrate. Measurements of the degree polarization were made at a wavelength of 670 nm. The results are compared to theoretical calculations made in the framework of a rigorous diffraction theory.

We study effects of macro- and micro-postprocessing of multilayered synthetic Ni/C film structures. The structures have nm-period 1D modulation of concentration of the major components. Initially low surface and interface roughness of such structures makes them advantageous for application as a new type of substrates in nanofabrication technologies and for information storage with nm-resolution. Metastability of microstructure and high residual stresses favor the use of the structures themselves as a media for fine-scale processing.

We demonstrate a new integrated narrow-band spectral filter which consists of a planar waveguide covered with a thin polymer film donated with molecules liable to persistent spectral hole-burning (SHB) at liquid helium temperature. We show that such a device performs as a miniature programmable narrow-band spectral filter with a transmission bandwidth less than 1 angstrom. In contrast to currently used techniques, the frequency resolution of a SHB filter is limited, in first place, by the width of the homogeneous zero-phonon lines of the chromophore molecules, and not by the geometrical dimensions of the device.

Amorphous fluorocarbon polymers are attractive materials for optical applications because of their high transparency at wavelengths up to 3 micrometers because of the absence of C-H bonds. since 1989 DuPont's amorphous fluoropolymer Teflon AF is available, films of which can be fabricated by means of spin, spray, or dip coating from solution or by use of compression or injection molding from the melt. An alternative and promissing route for processing fluorocarbon films is the use of a low- pressure plasma: This technique can be employed for plasma polymerization of suitable fluorocarbon monomers and for controlled etching of fluorocarbon materials. In the present work, we present the characteristics of plasma-polymerized tetrafluoroethylene layers with a refractive index of approximately 1.4. Reactive ion etching in an N₂O plasma is used for patterning these layers, and also the spin-coated Teflon AF films with a refractive index of around 1.3. Possibilities of fabricating passive and active polymer waveguide devices from flurocarbon polymers are discussed, and estimates of the expected waveguide performance are presented.

Diffraction lenses, formed on a surface of an optical waveguide (WDL), are important elements for a number of integrated optic devices as waveguide lenses and couplers. Such lenses can be fabricated by the electron beam lithography. The WDL can be constructed also by using a more simple method of holographic techniques with bulk beams. A key feature is that during use, at least one light wave (reconstruction wave) propagates as waveguide mode: parallel to the WDL and with nonunity index of refraction n_(omicron ) ($AP1,5). Additionally, the end-use wavelength (lambda) -$R) ($AP800 nm) differs from the construction wavelength (lambda) -$C) ($AP480 nm). Due to these features, aberrations exist in the image wave. We propose a method for recording WDL, that allows one to create aberration- free diffraction lenses if image wave is propagated in the waveguide. In the other case, when image wave is propagated in the air, the method provides an opportunity to compensate the aberrations using convex-plano spherical lenses in the object wave.

The modern production of integrated optic devices (IOD) is impossible without integration of all its components into a unified system ranging from the coordination of device parameters to their sales. The integration of artificial intelligence methods, microtechnologies and modern communications helps create IODs of quite a new quality. Such systems are being developed and used in the production of electronic devices. They can be the basis for the development of automated systems in the IOD production. These automated technologies use a unified production cycle model system.

A ring passive resonator has been developed and studied which utilizes optical channel waveguides formed on a K8 glass substrate by diffusion ion exchange in the potassium nitrate melt. Coupling between external devices and channel waveguides was implemented by coupling prisms and end joints. Experiments have been performed on the transfer function of the ring resonator which illustrate its resonant properties. The ultimate sensitivity of the light gyroscope has been estimated and ways for its improvement have been envisaged.

We discuss the design of all-optical universal integrated optic logical elements for digital optical data processing and transmission systems based on effects of changing of reference radiation spreading direction under the influence of control radiation. We present the possibility of construction of multichannel universal logical elements with high-speed programmed tuning on a realized Boolean function. Their throughput may be up to 100 billion operations/second and higher.