Low threshold lasers based on GaInSbAs/GaSb type-II QW structures operating between 2 and 2.4 micrometers at room temperature have been fabricated. The RT threshold current density as low as 305 A/cm² was obtained for a 900- micrometers -long laser emitting at 2.36 micrometers . High efficiency of indirect radiative recombination is explained by accumulation of holes in potential wells situated in barrier layers near the QW interfaces.

We report metalorganic chemical vapor deposition-grown double heterostructure and multiple quantum well InAsSb/InAsSbP laser diodes emitting at 3 to 4 micrometers and light emitting diodes up to 5 micrometers . Maximum output power up to 1 W was obtained from a MQW laser with stripe width of 100 micrometers and cavity length of 700 micrometers for emitting wavelength of 3.6 micrometers at 90 K. Maximum operating temperature up to 220 K with threshold current density of 40 A/cm² at 78K were achieved from the double- heterostructure lasers emitting at 3.2 micrometers . The far-field beam divergence as narrow as 24 degrees was achieved with the sue of higher energy gap barrier layers, i.e., lower effective refractive index, in MQW active region. We also discuss the effect of composition-fluctuation in the InAsSb active region on the gain and threshold current of the lasers.

Diode laser parameters such as emission wavelength, threshold current and optical output power, sensitively depend on the junction temperature of the laser diode. The temperature in the active layer results from the loss processes inside the laser structure as well as from the thermal characteristics of the semiconductor material and the heat sink configuration. In this paper, we present numerical model calculations employing a two dimensional finite element method in order to study the transient temperature behavior of high power laser arrays in a time range between 10 ns and cw-operation. Furthermore, we investigated the influence of different heat sinks on the thermal performance of whole device. Numerical and experimental results are compared.

Optically sensitive binary, ternary and quaternary materials are now being explored for formation of heterojunctions which are capable to produce mm-waves MITATT mode. The source of saturation current injection can be excited by optical phonon radiation of suitable energy, which in turn can enhance the saturation current leading to the drop in carrier multiplication factor across the active zone of the p-n junction. The optical radiation at the edges of the depletion zone thus can affect the microwave performance of the homostructure/heterostructure DDRs. The authors have undertaken computer aided studies on optical control of mm- wave performance of several heterojunction DDRs, which can find application for optical detection/communication system. Heterojunctions of different base material like GaAs and InP are designed with the ternary material GaInAs to generate mm-waves with microwave frequencies centered around an window frequency of 94 GHz. The result have also ben compared with those of corresponding homostructure double drift diodes. The DDRs have been analyzed considering drift and tunnel current in MITATT mode. A double iterative computer method has been used to study the effect of optical injection on device properties of both homostructure and heterostructure DDR. The results indicate that the rf power output decreases with optical injection, which enables the DDR to be used as an optical detector.

This paper gives an overview of opportunities for sol-gel glass guest-host materials chemistry in the area of glass integrated optics, glass integrated optics on silicon, from the perspective of optical devices and components. Our discussion locates sol-gel glass processing among several available and competing processes such as flame hydrolysis deposition and chemical vapor deposition for producing glass optical devices and components. For the most part, these are high temperature processes. Hybrid sol-gel glass chemistry (HSGG) is reviewed as an adaptable, potentially low cost, high volume, very low temperature alternative. HSGG offers an outstanding range of materials tunable in properties from ones that are closely related to organic polymers, to ones that are indistinguishable from high temperature inorganic glasses. HSGG gives the designer material compositions and properties that can be adapted to an enormous range of photonics attractive for their use in hybrid opto-electronic circuits. Reliability issues, packaging and interconnect challenges to the implementation of these materials are enumerated for the example of electro-optic modulation.

This paper describes the application of the silicon-on- insulator (SOI) technology as a platform for low cost guided-wave optics. Recent progress in material and device technologies are reviewed and results on multimode interference couplers, thermo-optics switches, and phased array wavelength filters in SOI are presented.

The sol-gel method is employed to implement a new, simple and highly versatile fabrication process for integrated optical waveguides on silicon. Photosensitive glass films of several microns thickness are dip-coated and optical components of various configurations through suitable masks are directly inscribed in them by ultraviolet light. Undefined regions are removed by soaking the films in an organic solvent for a few minutes. The developed ridges are then treated and planarized with a cladding layer. Altogether, the procedure is reproducible, and leads to waveguides with low propagation losses, on the order of 0.13 dB/cm.

We report on the fabrication and characterization of waveguide thin films on silicon by ultraviolet light imprinting in a new photosensitive, organically modified aluminophosphate sol-gel silica glass prepared by a one-step dip-coating process. Appropriate combinations of ultraviolet light exposure time, sol-gel film thickness and postbake parameters produce waveguides suitable for optical telecommunication applications.

We present the optimized design and the fabrication of an integrated-optic 1 by 32 multifunnel power splitter and the extension to a 2 by 32 splitter of the same type which we are the first to report. This splitter type operates by receiving the radiated input power at the end of a slab waveguide by funnel shaped waveguides of increasing width to compensate for the power decrease towards the outer parts. Using cycle of BPM simulation and adapting the width of the receiver waveguides according to the calculated intensity distribution we achieved a maximum excess loss of 0.5 dB in the simulation. The 2 by 32 splitter was designed using two input waveguides placed symmetrically 8 micrometers off-center and facing the center of the receiver region. Both splitters were fabricated by UV exposure of PMMA with photo initiator BDK. The realized 1 by 32 splitter shows an excess loss of 0.7 dB compared to a reference waveguide and a standard deviation of 0.5 dB with a maximum loss of 1.8 dB at (lambda) equals 1320 nm, the 2 by 32 splitter has 1.3 dB excess loss, 0.8 dB standard deviation and 2.5 dB maximum loss.

Microstructural features of a new hybrid organoaluminosilicate glass are described. The glass is prepared by low temperature acid catalyzed hydrolysis and polycondensation of organoalkoxides. This sol-gel method produces transparent materials for one-step, crack-free thin film formation suitable for fabrication of passive and active optical waveguides. Aluminum NMR reveals that the inclusion of erbium ions affects the structure of the glass by controlling the distribution of aluminum between tetrahedral and octahedral coordination sites in the lattice. The distribution appears to follow the 'aluminum avoidance principle' enunciated by Lowenstein. We also find that choice of the erbium ion precursor markedly affects the structure of the glass. This was demonstrated by comparing Er³⁺ derived from the nitrate and the double alkoxide, Er[Al(isopropoxide)₄]₃. The latter compound, when mixed in pre-hydrolyzed organosiloxane media, forces aluminum to retain its tetrahedral coordination geometry. This is not so when erbium originates from the nitrate. Evidence from NMR, Raman and transmission electron microscopy suggests that the erbium ion is rather homogeneously dispersed in the glasses. This suggests that clustering of the rare earth may have been defeated in this system. Because the glass contains a photosensitive moiety, erbium-doped channel waveguides can be prepared by direct photoinscription.

Possible ways of generating visible light in optical waveguides excited with infrared light are investigated. Preliminary results obtained in doped TiO₂ sol-gel thin films are reported and various possibilities of improving the efficiency of the devices are considered.

Nonlinear optical polymers are gaining increasing research interests for high frequency photonic device applications, in particular, broadband modulators in commercial communication systems. the unique features of these materials allows the fabrication of integrated optical modulator chips that are compact, lightweight, and broadband at a low cost. With the advances in material synthesis and device fabrication, the application of polymer electro-optic modulators in commercial fiber-optic data links becomes increasingly realistic. We report our design, fabrication and packaging of polymeric integrated electro-optic Mach- Zehnder intensity modulators, as well as their test results including halfwave voltage, frequency response, optical insertion loss, on-off ratios, etc. We have inserted our packaged modulators into commercial fiber optical data links for applications tests. The standard tests procedures for the cable television industry are used and the results are compared to current commercial NTSC multi-channel cable television transmitter units with directly modulated lasers or LiNbO₃ external modulators. The stability issues including thermal stability, photochemical stability and bias control stability have been investigated and will be discussed. The bottle-neck technical issues that may affect device design, fabrication, and applications will also be discussed.

A digital optical switch with a modified coupling region is designed by using the beam propagation method, and it is fabricated by employing an electro-optic polymer rib waveguide formed by the reactive ion etching method. The structure of the modified coupling region and its refractive index profile are designed to optimize the mode coupling in the Y-branch, since the coupling determines the switching performance. Therefore, the switching performance of the device may be enhanced with a fixed device length. The practical optimization of coupling region is performed by using the photobleaching method after the device fabrication. The crosstalk has been experimentally improved by as great as 4 dB by introducing the modified coupling region. The drive voltage is also reduced by more than 30 percent.

Small young companies can commercialize photonics. Many are already doing so and may more are getting started with a small government subsidy from Small Business Innovation Research. Capital is gushing, even begging for good investment opportunities, for companies ready to commit themselves to commercial success.

Low power, optoelectronic integrated circuits are being developed for high speed switching and data processing applications. These high performance optoelectronic computing modules consist of three primary components: vertical cavity surface emitting lasers, diffractive optical interconnect elements, and detector/amplifier/laser driver arrays. Following the design and fabrication of an HPOC module prototype, selected commercial funding sources will be evaluated to support a product development stage. These include the formation of a strategic alliance with one or more microprocessor or telecommunications vendors, and/or equity investment from one or more venture capital firms.

Thirty years after first envisioned, integrated planar optical devices are being commercialized. The markets driving commercialization are discussed. The types of planar devices and fabrication techniques are described. The technologies required for planar integration are then reviewed. Finally, some challenges facing commercialization are explored.

We propose a novel electrooptic (E/O) phase modulator using domain inversion of a part of an E/O crystal. The domain inversion is achieved by applying a high electric field to an E/O crystal at room temperature. We made an E/O modulator of an LiTaO₃ with this method and experimentally confirmed the operation of the Quasi-Velocity matched E/O modulator at high microwave frequency. As a result, we obtained ultrawide modulation spectra of 1.85 THz width.

This paper will deal with the ability of a high energy flashlamp to decoat surfaces using a photoablation method. The flashlamp produces a broad-band near-blackbody radiation spectrum that peaks in the far-UV. We call this flashlamp a near-blackbody radiator because of its ionization characteristic that is predominantly composed of free-bound transitions, and because of its high emissivity that ranges from 0.89 across the UV band to almost unity across the VIS and IR bands. Three distinct phases divide the flashlamp photoablation process: (1) Initial photoablation of the coating by the intense light energy pulse of the flashlamp; (2) VOC scrubbing of the newly created vapor and plasma layer by the UV component of the light pulse; (3) Removal and trapping of the resulting fine ash and residual fumes by chemical and mechanical means. In order to accomplish the first two phases, the peak plasma temperatures generated within the flashlamp must be on the order of 7500K to 15000K with pulse durations ranging between 170-680microsecond(s) ec. Even though the peak power of the flashlamp is high for its size, ranging from 12-30Mw, the lamp lifetime is reasonable at 1- 10 million shots. It is this high lamp lifetime, as well as the flashlamp system's inherent simplicity, that makes the system cost effective and rugged for the application being proposed in this paper.

In this paper, three relevant examples related to space applications are considered of new integrated optic systems: the first one refers to on-board data pre-processing in remote sensing applications, the second one concerns a correlator for SAR processing and the third one is relevant to a beam forming network for active array antennas for satellite telecommunication applications. Exploitation of such opportunities would open new fertile terrain for commercialization of integrated optic devices.

The single crystalline solid solutions H_xLi_1-xNbO₃ prepared by proton exchange exhibit very complex structural chemistry which is different from known for powders. The H_xLi_1-xNbO₃ layers present up to seven different crystallographic phases. the correlation between the crystalline structure, refractive indices, proton concentration and ferroelectric properties has been experimentally determined, that allows to predict the characteristics of great variety of waveguides.

The field of integrated optics design software tools is reviewed. Current status of main waveguide optics calculation tools is discussed. An example of design environment is described in more detail.Integrated optics design is divided into different areas: layout design, process modeling, waveguide device design and guided-wave circuit design. Typical present approach of software is emphasis on layout design and beam propagation method simulation, aimed mainly for device design, but somewhat limited in scope by the lack in addressing constructive device design viewpoint.

The performance characteristics of an integrated optical directional coupler are extremely sensitive to both geometrical and optical waveguide parameters: this makes quite difficult the realization of devices complying with the design specifications. The adequacy of currently available design and modeling tools is discussed, starting form the analysis of the measured performance characteristics of directional couplers fabricated in glass substrates by K⁺-Na⁺ ion-exchange.

The beam propagation method (BPM) as a design tool for integrated optics is usually implemented with respect to waveguide configurations. When single interfaces and arbitrary refractive index distributions are used to define the geometry, the remaining limitations are due to the approximation of the Helmholtz-operator and the neglect of reflection. Using wide angle propagation schemes and taking into account he reflection at a single interface the BPM, solving an initial value problem only, can be applied to a variety of microoptic structures. This includes graded index lenses, microprisms, transmission gratings and so on. Thus, a sequence of integrated optical and microoptic components can be modeled within one scheme, inherently operating with the amplitude and the phase of the optical field. In the case of 1D refractive index profiles, finite difference algorithms give very rapid answers. This is profitably used when the BPM is applied to ion exchanged transmission gratings, which is described in more detail. With a Fourier- transform in the plane of the air-glass interface, the reflection can be taken into account using Fresnel's formulae. The results for the diffraction efficiencies into different orders calculated by the BPM are compared with those of a rigorous integral equation method. Because multiple reflections can be neglected, the results of both methods agree well. The calculated phase relations between different diffraction orders, which are of special interest in the filed of interferometry, are found to agree well with experimental results, too.

We report here about a computer simulation program, based on a comprehensive physical and numerical model of an a/(mu) c- Si:H p-i-n device, applied to the 2D problem of describing the transport properties within the structure under non- uniform illumination. The continuity equations for holes and electrons together with Poisson's equation are solved simultaneously along the two directions parallel and perpendicular to the junction. The basic semiconductor equations are implemented with a recombination mechanism reflecting the microcrystalline structure of the different layers. The lateral effects occurring within the structure, due to the non-uniformity of the radiation are outlined. The simulation results obtained for different wavelengths of the incident light are compared and shown their dependence on the energy of the radiation. The results of simulating a p- i-n (mu) c-Si:H junctions under non-uniform illumination is that the generated lateral effects depend not only in intensity but also in direction on the wavelength of the incident radiation.

The optical noise of the set: DFB Laser + EOM has been investigated, in a medium frequency range. This noise characterization clearly shows that in most cases the modulator increases the noise level properly relevant to the laser emitter. However, far above threshold, the optical noise at the end of the modulator tends, in some specific cases, to the fundamental noise, that is to say the shot noise level.

Our FOrtran program MOLCAR is well suited for the hybrid analysis of passive or active longitudinally homogeneous dielectric waveguides in integrated optics or in microwave engineering. Transverse to the propagation direction the waveguides can be shaped arbitrary and the waveguides can be composed of layers with lossy materials like metal and dielectric. The generality of MOLCAR allows the analysis of a wide range of different waveguide structures like slab waveguides, rib waveguides, channel waveguides, diffused channel waveguides, waveguide couplers, structures which include metallic layers like TE/TM mode splitters, microstrip lines, coplanar waveguides, elevated coplanar waveguides, slot lines, strip lines and arbitrary combinations of all these waveguides, e.g. diffused channel waveguides or groove guides. The propagation and attenuation constant, the distribution of all field components and the intensity distribution as well as the characteristic impedance can be obtained by using MOLCAR. The program is based on the method of liens which is a semi-analytical method and yields for that reason a high degree of accuracy with less computational effort. The computational window is drastically decreased by using special absorbing boundary conditions. Especially for waveguides with a weak confinement his proves very advantageous and the occurrence of box modes is also avoided.

Silica waveguide technologies have been developed based on a combination of the flame hydrolysis deposition and reactive ion etching, which have the advantage of structure controllability and reproducibility of integrated circuits. The bonding technology using UV adhesive and the mold packaging technology have been developed. Silica waveguide integrated devices such as 1 by N, 2 by N and N by N, polarization maintaining splitters, wavelength division multi/demultiplexers, frequency division multi/demultiplexers, dense WDMs, and optical switching devices can be commercially produced with these technologies.

We have demonstrated the feasibility of Er/Yb co-doped strip-loaded waveguide using a glass thin film deposition process based on sol-gel chemistry. We have assessed the potentiality of using this sol-gel technology to make commercial integrated 1.55 micrometers optical amplifiers. For this purpose, we have checked the spatial uniformity of the fluorescence lifetime and losses. We have also checked the fluorescence lifetime stability over time and we have evaluated the fluorescence spectrum flatness of the material.

The advent of phase mask technique has made it possible to fabricate Bragg gratings to tight tolerances in a repeatable, reliable and cost effective manner. These gratings are in turn making it possible to manufacture a wide variety of high performance guided wave devices for lightwave communication and sensor applications. This paper will review the phase mask fabrication technology and the commercially available products. the paper will then discuss a few successful applications of grating based devices currently entering the market, in particular, wavelength demultiplexing devices, gain flattening filters for EDFA and dispersion compensators, all of which are critical elements in high data rate lightwave systems.

In this paper we show that large scale integrated optic circuits can be used in performing complex optical signal processing such as spectral encoding, correlation, and possible logical operations in conjunction with electrical circuits. We present the photonic pattern concept based on which we developed a theory that shows how we can process optical information with scalar linear operations. Moreover a new communication system for parallel transmission of many data channel is presented.

Potassium ion exchange is used to make channel waveguides in an erbium-ytterbium co-doped phosphate glass. Gain characteristics of the fabricated waveguides are studied. The effect of pump and signal wavelengths, and the waveguide length on the gain in the waveguides are investigated. At the signal wavelength of 1.530 micrometers , 19.5 dB internal gain is achieved in a 6 mm long waveguide; the measured noise factor is 4 dB.

All silicon Fabry-Perot modulators, operating at the wavelengths of 1.3 and 1.55 micrometers , have been fabricated by VLSI technology. The planar channel cavities, with lengths ranging between 50 and 100 micrometers , have been obtained by plasma etching and not by cleavage of the chips. Therefore, the devices are really integrable with microelectronic circuits or with other photonics components. the modulators, based on the thermo-optic effect, are electrically driven and operate at repetition frequencies up to about 2 MHz. This is by far the best result obtained in thermo-optic effect based modulators. Optimixed version of the devices could find application in low-cost optoelectronic systems at the subscriber units in fiber-to-the-home networks.

We present various fabrication techniques for 1 by 8 single- mode fiber couplers. Single-mode couplers are used for signal distribution in optical networks. Traditionally, for division of eight or more, several couplers are cascaded. This constraints increases the length as well as the production cost of the component. Our work demonstrates that the fusion/stretching process for making couplers can be applied to couplers containing up to eight fibers. Three different techniques have been studied to produce these couplers. Through one technique, uniformity of power was obtained at 1.55 micrometers . Typical losses are less than 1 dB. A theoretical analysis of the structure shows the coupling of eight supermodes. However, if transversal symmetry is respected, only two of these supermodes will interact in the power transfer between the fibers. The control of the interaction of these two supermodes permits a control of the wavelength dependence of the component. These phenomena are analyzed and experimental results are presented. The new 1 by 8 coupler is a compact component of less than 10 cm that integrates itself efficiently within the networks.

High isolation 1480-1550 nm WDM using fused fibers has been achieved. Several techniques have been tested but 2 by 2 fused couplers cascaded with filters give best results. Indeed, they demonstrate an isolation greater than 30 dB over 25 nm for the 1480-1550 nm WDM with a maximum insertion loss of 0.3 dB. Furthermore, the polarization dependence has been reduced to 0.1 dB. This device can therefore realize very efficient demultiplexing in EDFAs at low price.

The coupling efficiency of diode lasers to optical fibers is theoretically investigated at 1.55 micrometers wavelength. A waveguide device in glass for low-loss multiplexing of diode laser arrays to optical fibers is proposed. The device is composed of cascaded Y-junctions made by single ion exchange in glass with taper waveguide at input or output end. The taper waveguide is made by a double ion exchange process. Theoretical simulations indicate that approximately 5 dB improvement per channel, compared to a simple multiplexer, in coupling of diode lasers to single mode optical fibers can be achieved using the proposed device.

Two multimode integrated optics devices were demonstrated: an asymmetric bus access coupler for passive linear bidirectional fiber optic bus and a combined optical-to- electrical converter and bidirectional data transceiver. The integrated optics devices were made using electric field assisted Ag-Na ion-exchange processes; the versatility of the ion-exchange process allowed for the implementation of these integrated optics devices, which by the use of commercial fiber optical devices would have been difficult. The design of the asymmetric bus access coupler enable d efficient coupling from a node to the bus while the fraction of optical power that was coupled from the bus into the node was optimized for the number of nodes. The optimization of the coupler for an LED source allowed for 7 nodes to be connected in the bus for a 30-dB optical power budget. A 27 percent optical-to-electrical power conversion efficiency was obtained for a customized 10-element photovoltaic array that was illuminated by the use of a customized 1 by 10 integrated optics coupler; in addition, the design of the array and coupler enable bidirectional optical data transmission via a single multimode fiber.

We use an optical fiber sensor whose part of clad is removed for the optical constants of ultra thin film measurement. The sensitivity of the sensor is increased by decreasing the diameter of the optical fiber and/or increasing the length of the film deposited part. The result of the in situ measurement method of change of amorphous hydrogenated silicon (a-Si:H) ultra thin films by oxidation with passage of time by leaking from vacuum to atmospheric air is shown. We use an optical fiber sensor whose length of the film deposited part is 100 mm, diameter of the core is 110 micrometers and the core material is silica. a-Si:H film with approximately 10 nm in thickness is deposited on the core of the optical fiber sensor. The oxidation saturates in approximately 600 s. The larger attenuation of transmitted light at the long wavelengths from 685 to 800 nm is observed. This phenomenon is maybe due to the change of defects by relaxation.