Starting from the present state of tl art of discrete devices up to the on going realization of monolithic semicorxtuctor integrated prototypes an overview ofoptoelectronic devices for telecom applications is given inchiding a short classification of the different kind of integrated devices. On the future perspective of IBCN distribution network some economica of hybrid and monolithic forms of integration are attempted. lnaflyashoitpresentationoftheactivitiesperformedintbefieldofmonolithic integration by EEC ESPR1T and RACE projects is reported. 1.

Recent advances in semiconductor crystal growth and process techniques have made it possible to produce semiconductor wire and box structures on a mesoscopic scale (''''1Onm). The interference of electron waves in the mesoecopic structures bring about various phenomena which are interesting from the view points of solid-state physics as well M device application. This paper addresses the recent progress in research on the semiconductor rnesoscopic structures that is fabrication processes characterization and application to optical devices. The unique optical features of the mesoscopic structures are discussed in relation to the quantum coithnenient effects in one-dimensional quantum wires and zero-dimensional quantum boxes. The carrier confinement effects in the low-dimensional systems lead to new concepts for device physics which utilize nonlinear birefringence and coherent nonlinearity. The current status and the problems associated with the fabrication of these semiconductor low-dimensional structures are also discussed. I.

Large electric field induced refractive index variation and large index variation absorption loss variation ratio in low fundamental absorption region are theoretically reported in a GaInAs/InP quantum box (QB) structure. This effect is shown to be applicable to low loss intersectional type optical switch. Moreover the Q B size dependence as well as fluctuations in QB size on QB-intersectional type optical switch was also discussed. As a first step towards the realization of such high-dimensional structure we have fabricated and measured the index variation in a GaInAs/InP multi-layered ( 3layers) quantum wire structure. The measured index variation was around 4 at an applied reverse bias voltage of 3V. I.

We investigate the electro-optic effect in quantumwire (QWR) arrays and discuss possible applications for self-electro-optic-effect devices. By application of a static electric field normal to the growth planes the interband optical selection rules are modulated between one and two dimensional due to heavy-holelight-hole mixing. I.

Magnitude of the signal relative to noise determines the ultimate quality of all information transmission. In a lightwave system there are several fundamental and nonfundamental noise mechanisms that govern the system ormance. In this paper concepts related to these issues will be developed and a review of the current status of this rapidly evolvmg field will be given. 1.

We present a simple and accurate . ethod for the analysis of tunneling through an arbitrary onediaensional potential barrier based on the Modified Airy Function approach. We have considered truncated step-linear parabolic and quartic potential barriers. The results have been coipared with those obtained by the conventional WKBJ modified WKBJ and the aatrix sethod. The effect of the truncation level on the tunneling coefficient has also been investigated. I .

I.

The objective of this paper is to investigate the theoretical aspects of colorimetric noise analysis of component video signals for an optical fibre video transmission systems. The design of a low noise optical fibre colour video transmission system requires information regarding the degradation of various hues or at least the colours to which the eye is more sensitive in the presence of system noise. An expression for objective component video signal-to-noise ratio called the Display Signal-to-Noise Ratio (DSNR) is derived for both subcarrier frequency and amplitude modulated systems for the first time. The DSNR expression take into account the effects television receiver decoding and the nonlinearity of the display tube. A fundamental relationship between the input composite video SNR and the DSNR is established. Using this analysis impairments in various hues at different saturations and at different luminances are examined. The effect of the input noise spectrum on displayed primary colours is also analysed. The analysis discussed here is shown to be useful not only for present but also for future video systems and for dynamic noise reduction applications. 337 L

The design and performance of a novel circuit working with a Gallium Arsenide multiquantum well p-i-n modulator is reported. The circuit can rapidly compensate for the temperature dependent shift of the excitonic energy position of quantum confined stark effect modulators. The energy position remains invariant over a temperature of 10K. The circuit is simple and can be operated with a single device or an array of modulators. I .

We describe a modification of a nonlinear Mach-Zehnder interferorneter to produce a sub-Poissonian photon distribution and an experimental set-up to realize it. It is shown that it is possible to achieve a substantial reduction in the photon number uncertainty with a high power efficiency.

An acousto-optic phased array antenna beamformer with independent phase and carrier control capability is experimentally demonstrated using single-sideband signals driving two acousto-optic devices. A dynamic range of 66. 6 dB +2 MHz and carrier-to-noise of 126. 9 dBIHz +2 MHz is measured. This beamformer has wide antenna tunable bandwidth and intrapulse beamforming capabilities. L

We present an approxiMate aethod for the analy8is of diffused channel waveguides. The aethod is iterative requiring only 3-4 iterations and is based on the variational principle. We have also applied the Rethod to study the diffused channel waveguide directional couplers. I

Iritum arxi antincny-dcped strain layers of GaAs grcn by liquid phase epitaxy are st3.ted hy phcal, electrical and cçtical techniques . Doping ranges to obtain lci dislocaticri dsity GaAs are assessed. Nz deep levels associat1 with irx1izn arx antinony dopants are identified by photocurrent technique, and their possible origins are discussed.

Abstract not available.

Aluminosilicate gels of different alumina and silica ratios and cordierite MgAkSi5O1 gels were made by the nanocomposite sol-gel route and sintered to obtain highly dense materials. Measurements of the dielectric constant K and dissipation (loss) as a function of temperature and frequency showed that low dielectric constants of 5. 6 and 5. 4 at 1 and 4 MHz respectively for cordierite and of 6. 9 and 6. 7 at 1 and 4 MHz respectively for mullite at 25C were achieved. Aluminosilicate materials prepared with 10 wt A12O and 90 wt SiO showed the lowest dielectric constants of 4. 27 and 4. 20 at 1 and 4 MHz respectively.

Output power and fiber-to-fiber gain along with infernal gain of the active element and optoelectronic signal curves at different values of input power versus pumping current are measured for the amplifier modules on the base of AR-coated InGaAsP/InP BH diodes. It is shown that diagnostics of the amplifier module oper''ation regime may be performed by voltage measurements and the optoelectronic signal can be used to monitor optical information passage in the regenerator device or for the distributed access the data transmitted in the lightwave comrnunicat ion systems. I.

It has been shown that improved surface properties of InP could be achieved through HF and sulfide NaS. 9HO) treatments. The photoluminescence (PL) intensity was found to increase due to reduction in interface state density after chemical treatments. X-ray photo-electron spectroscopy (XPS) studies revealed that the formation of IflF3 and P2S3 after HF and sulfide treatment respectively are responsible for better interfacial behaviour. I.

Liquid phase epitaxy (LPE) is a very suitable growth technique for InGaAs detectors. The growth of high purity epitaxial layez wth low electron concentrationl0 cm however requires prolonged baking to reduce background impurity concentrations. This work reports the use of novel rare earth (RE) gettering technique to reduce background carrier concentration with nominal baking tirne. At a RE concentration of 8xlO atomic fraction the highest mobility was obtained. Beyond this while the carrier concentration and etch pit density decreased inonotonically , the mobility also decreased. SIMS and photoluininescence (PL) studies showed that the gettering effect was due to removal of silicon . For InGaAs similar results were obtained except that the layer showed type conversion at high RE concentrt5ion.Otimised layers with n = 2.4 x 10 cm ?ave been characterized through resistivity, Hall effect, PL and DXRD measurements. The narrow linewidths showed the exellent quality of the layers and interface.The present status of fiber-optic detectors grown by LPE as well as MOVPE will be compared as regards sensitivity, frequency response and data rate. The performwice of integrated fiber-optic receivers with GaAs FET preamplifier will also be discused.

Electronic system U3iflfl ULSI wi11 be based on ultrasmall features for ULSI monolithic circuits and on small f eatures for advanced packaging such as multi-chip modules (MCMs). These reduced interconnection cross sections are needed to achieve very high density circuits but may conflict with achieving very high data rates across thos e interconnections. Optical interconnections may provide both very high density interconnections and very high speed data rates. Most comparisons of optical with electrical inter. onnection emphasize the high speed bipolar circuits rather than the high density CMOS circuits. However within VLSI/ULSI systems CMOS interconnections are quite different from and offer several advantages (particularly lower power dissipation at the system level) over bipolar LSI interconnections. The role of optical interconnects is viewed here from the perspective of the CMOS interconnection environment. L

Several of the high speed optical fibre Metropolitan Area Networks proposed in recent years are slotted networks using deflection muting [1]. Manhattan Street Network is amongst the simplest of these with an underlying Manhattan graph. We propose to place highways in the Manhattan street network. This significantly reduces the delay in the case where packets have to travel long distances. With the reduced delay the network can better support multiple services like packetised voice in addition to data communication. I.

Optical sIf-rt*tsg scheme. inK*iCh packet switched net eo integrated optic direCtiO*aI copIers a*d an all optical scheme employing FmbryPerot de tce have ken ptvpuseL Both the methods make se ofCDMA sequences in their headers msking the process of address recognition simple mechanim. These aeqitences eliminate the seed for atorqe demeists for header processing. 1

The paper suggests a method of computation of Discrete Walsh Transform (DWT) by matrix vector multiplication which is easier to perform in 2D optical system where processing can be done parallely in 2D. The computation of DWT in such an optical computing architecture is much easier to perform and requires less processing time. A methodology is also proposed where a microprocessor is utilized to sequentially process matrixvector operations on digitized data. The result is stored in the memory for display and/or read out. I.

Present work reports successful pre paration of thin transparent homogeous films of ferroelectric TGS and PVF2 by a spin technique and their characterization for application in 10 waveguides. The characterization were done by observing modelines through a spectrometer for the measurement of mode angles. The other important parameter that is required to characterize are refractive index and light propagation loss which have also been evaluated. I

IL EXPERIMENTAL Cr(VI) [as (4)2271 and Fe(ffl) [as FeC1] doped Polyvinyl alcohol and Polyacrylic acid systems have been employed'' as real-time holographic recording materials. Holograms have been recorded in Dicbmmated Polyvinyl alcohol (DCPVA) Dichromated Polyacrylic acid (DCPAA) and Ferric chloride Polyvinyl alcohol (FePVA) films. Various chemical and physical parameters influencing the holographic performance have been optimized. L

Applications of ultrafast optics to microwave technology are reviewed. A time domain broad band sparameter measurement technique has been demonstrated. On-wafer phase locking of a free running microwave source to the optical pulses is also reported. Some of its applications are discus''sed. I.

The effect of optical radiation on the electrical characteristics of a HENT device has been carried out. Both photovoltaic effect in the metalsemiconductor junction and photogeneration of carriers in the space charge layer of n-A1GaAs HENT device have been taken into account. Offset voltage is found to decrease with flux density and active layer concentration. The drain current is observed to increase with the increase in radiation flux density photogeneration of electronhole pairs. The photovoltaic effect develops a forward voltage across the metalsemiconductor junction. In a A1GaAs/GaAs system the electrons and holes generated in nAlGaAs layer are separated out from each other by the field across the'' metalsemiconductor junction and heterointerface. Thus due to the additional charge carriers the charge density in 2DEG at the heterointerface of the HENT structure will be modified. The theory is given in the next section. Theory The optical HENT structure is shown in Fig. 1 . The region between the Schottky gate and the heterojunction interface is assumed to be totally depleted and the electrostatic potential v2 at the end of the semiconductor (x d2) is obtained by solving Poisson''s eqn. 2 - '' [N2(x) + n(x)(1) dx2 alongwith appropriate boundary condition N2(x) and 2 are the doping concentration and permittivity of n-A1GaAs layer. n(x) is the Photonic devices find a lot of applications in optical communication integrated optics and optical computer. High speed devices

A simple design is developed for corrugated waveguides for operation in the millimeterwave range of frequencies. The method determines both the corrugation period and the depth. The design is based on slab waveguide principles and uses solutions of the (scalar) boundary value problem of the slab waveguide to determine the corrugation depth and the corrugation spacing. The design tecimique compares well with other techniques developed for the purpose. Reflections at 90 at certain specific wavelengths are measured in the far field to obtain the radiation patterns. The patterns show good agreement with theoretical predictions confirming the effectiveness of design principles used. Measurements range in the frequencies from 90 GHz to 100 GHz. 1.

Two open waveguides separated by a finite spacing can be decoupled if the index between them is a suitable function of the transverse coordinates. The proof of this statement relies on vector properties of e. m. waves. On the contrary decoupling is impossible for scalar waves. Therefore it is incompatible with the weakly-guiding approximation. However numerical results and other ones based on perturbation theory show that it can be ohtamed with index differences which are still small enough to be practical. Decoupling can be interpreted physically as an antiresonance of the region between the guides. Examples are presented and potential practical applications are outlined. I.

An analytical technique was developed using Jacobian elliptic functions to determine the beam profile parameters for graded index (GRIN) fibers with fourth-order radial index distribution. Results using this techthque show significant effect of fourth-order radial variation on the beam profile parameters. L

In this work 3D techniques based on finite difference (FD) schemes will be introduced to efficiently simulate the wave propagation in both longitudinally variant and invariant InP based devices. For a longitudinally invariant medium whose refractive index does not vary along propagation direction, we have chosen a step-index channel waveguide and determined the intensity distribution of the fundamental mode. As a longitudinally variant integrated optic structure, a tapered waveguide is selected which is commonly used as a beam transformer for butt-joint coupling of the above mentioned rectangular waveguide to a fibre. According to both structures two different FD techniques are chosen to permit a numerically more effective investigation as against the split-operator fast- Fourier transform (FFT) method, also known as the Beam-Propagation-Method (BPM). This paper consists of three sections. In the first chapter the FD method will be investigated in comparison with the BPM and its capability for solving a variety of integrated-optics problems will be emphasized. The second chapter describes the analytical background of the propagation algorithms used in this paper. Numerical results obtained by the application of the developed algorithms to the above mentioned two devices will be given in the last chapter. investigation of perhaps most complex integrated optics structures in order to finally determine the optimized design of the optical device before going into production. Since none of the existing methods is universal, one must choose a simulation method according to the given problem or think of developing something new. In this work we show that for two different structures two different FD methods are capable to tackle the given simulation problem. Each method has its advantages and disadvantages.

The modal solutions of an arbitrary graded-index dielectric slab waveguide have been derived by applying the generalized telegraphist's equations to the equivalent inhomogeneous parallel-plate waveguide model with electric or magnetic walls. These solutions have been employed in a mode-matching procedure to calculate the transmission properties of step discontinuities in diffused optical waveguides having exponential, Gaussian and complementary error-function index profiles. For slab waveguides contaming an abrupt offset, the radiated power is found to increase smoothly with increasing displacement. Power loss calculations for an abrupt change in the diffusion depth show a sharp transition from almost zero loss to nearly total radiation loss in the vicinity of the cutoff wavelength associated with the dominant mode.

For long wavelength single node DFB type laser devices it Is required to rrugate the surface of InP substrate in the form of lines (Grating) with spatial period In sub-half micron ng. Electron beam lithography (E2L) can be used to make such high resolutlon lines first in the resist and then these lines can be transferred to the substrate by suitable dry or wet etching process. In delineating such closely spaced lines In the resist which Is coated on a relatively high average atctnic number substrate ( At.No.32), the well known proximity exposure (PE) effect associated with EBL requires cxrrection • The paper discusses arid gives the simulation results which depict the effect of PE on the width and spacing of lines. A comparison Is made between the lines on the lower At.No. substrate Si, and high At.No. InP substrate. A proximity exposure compensation (PEC) scheme based on dose variation technique is found to provide just adequate correction to PE effect. The experimental results on the delineation of lines before and after correction show good agreement with the simulated results within experimental limitations.

Silicon close contact rapid thermal annealing (RTA) behavior of heated Zn implants in lnP at low doses 5E11-1E12 ions/cm2 has been studied in the temperature range 800- 900C. Annealing at 800C for 1 0 seconds results in 90+ activation with acceptable profiles. At temperatures above 800C the implant profiles are considerably broadened and exhibit anomalous diffusion tails. The shape of the dopant profile and the position of the peak ion concentration are influenced by phosphorus out diffusion from the sample surface and bulk impurity redistribution du ring the activation process. RTA annealed Au/Zn/Au alloyed contacts were formed on the activated regions in the temperature range 350-450C and the contact resistivity was measured by the Transmission Line Method (TLM). A minimum contact resistivity of 24 xlO-3 a-cm was obtained for the sample annealed at 400C for 5 minutes. X- ray Photoelectro n Spectroscopy (XPS) depth profiles show significant Zn and Au in-diffusion into the substrate at 400C. I.

Photopolymers offer excellent pmperties such as ease of handling low cost and real-time recording for the application of holography and non-linear optics. A Vinyl Polymer viz. Polyvinyl Alcohol has been employed for holography and non-linear optics. In this paper results of our experimental investigations on dye/polymer systems for real-time holographic recording and non-linear optics are reported.

Nonlinear pulse propagation in optical fibers and stationary self-focusing of laser beams in nonlinear media are investigated using the invariant of motion method. It is shown that this method is not only effective for the solution of problems related to nonlinear propagation in quasi-optics but also algebraically simple and yields results faster. In the first case it enables one to follow the dynamical interplay between dispersion and nonlinearity in detaiLthe knowledge of which is essential for applications to soliton based communication system. In the second case,unlike paraxial ray theory ,it takes into account the spatial characteristics of the whole beam and shows that the real critical power for self- focusing should be at least four times the critical power given by paraxial ray theory.

Optical Phase Conjugation studies have been carried out on five different metal substituted Tetraphenyl Porphines. The dependence of conjugate efficiency on perturbation of u-electron cloud of porphine ring by different substituted metals solute concentration solvent parameters intensities and quantum efficiencies have been investigated. I. Intrrxiuctiort: Tetraphenyl Porphines form the basis of many biological molecules including hae moglobin and chlorophyll. However their ability to absorb visible radiation strongly and their conjugated double bond structure allows us to keep them within the general classification of dye molecules. The structural formula of the free base tetraphenyl porphine (H2TPP) is given in fig. 1. Other porphines can be formed by substituting the two centre hydrogens with a metal. The presence of this metal perturbs the yr-electron cloud in the porphine ring and this perturlxition is dependent on the substituted metal. Porphines therefore appear to be an excellent model system in which one can investigate the effects of perturbing a u-electron system by DFWM. Porphines exhibit the phenomenon of reverse saturable absorption i. e. a decrease in transmission with increasing intensity of incident radiation. This occurs if the absorption 257 cross-section from the excited state up to a higher excited state is larger than the absorption from the ground state to the excited state. In this paper we present the details of phase conjugation studies on five metal substituted te traphenyl porphines: (1)Al TPP (2)Co TPP

An analysis of the asymmetric response from the device facets is performed. Attention is devoted to the mechanisms that make the feedback adversely affect differential quantum efficiency in a single-mode laser. A key is obtained to the description and control of the non-linear P-I relationship in the region just above threshold (kink).

U1travio1t radiation down to 47nm and infrared radiation upto 3. 4 has been qenerated by second harmonic generation surn+requency mixing and di++rence-- +rquency mixing in a Barium Borate cryutal . The bai c pump 1 aser used I s 1064nm Nd:YAG laser. The other tunable pump source is derived from dye laser. The generation is made by nonco). linear i nteract 1 on. 1.

The existing model of Fermi sea shake up to explain the excess transverse magnetic component in optical emission from quantum well lasers is inadequate beyond the lasing threshold condition. In this paper we propose that when lasing occurs the heavy hole wave-function loses directionality and has equal projections in x, y and z directions.

Many seemingly diverse optical processing operations are possible on one new multifunctional optical architecture. We describe these operations and provide examples of each for scene analysis. L

Configuration. of artificial satellites for communication remote sensing and scientific investigations at present is based requirements of payload or experiment within the constraints of weight volume and power available and utilizes existing proven technologies. The advances in opto electronic components and systems have opened up a new dimension in designing satellites of the future incorporating new technologies. This paper deals with general ideas on configuring satellites based on advanced opto electronic systems wherever applicable. 1.

n(x) na flb na (d+2a) d d (d+2b) otherwise 450 (1)

Coupled-mode theory (CMT) has a number of application. involving mvJtiple wavegtides periodically perturbed nonlinear or extenzally perftirbed wave g''ides. In this paper CMT is tsed to deterniinig the scaMr modes of a tt clad fiber. The basie of the approach 18 that the normal modes of a copIed wavegttide th''schire can be eXpres8Cd as a . riperposition of the cospied modu. 1

The fabrication and performance characteristics of InGaASP/InP and strained JnGaAS/GaAS InGaAS/IIIP quantum well lasers are described. Recent results on low threshold high power low absorption loss low chirp and low linewidth which results in new system applications are presented. I. SUMMARY Quantum well (QW) lasers fabricated using the AlGaAs/GaAs material system has been extensively studied and these devices show improved performance characteristics than regular double heterostructure lasers. The fabrication of quantum well lasers require very high perfection of materials growth and interfaces. Such high perfection has been achieved using MOCVD (metal organic chemical vapor deposition) growth technique for In_p based materials. As a result it has been possible to fabricate high performance unstrained and strained InGaAsP/lnP quantum well lasers and examine the performance improvement for system applications. For GaAs based materials QW lasers can be fabricated using both molecular beam epitaxy (MBE) and MOCVD growth technique. The principal advantages of QW lasers over regular double heterostructure (1)11) lasers are (i) lower threshold current density (ii) lower optical loss which can result in low threshold current and higher power and (iii) lower dynamic linewidth under modulation which results in longer repeater spacing for optical fiber transmission ms The parameters for optimization of a quantum well laser structure are the well and barrier widths barrier composition and grading for a graded index separate confinement heterostructure (GRIN-SCH) design. The 137 schematic of QW laser

The paper reviews recent results obtained with diode lasers used in external hybrid cavities with frequency selective feedback. Very wide discreet tunable ranges are achieved. They can be made to oscillate in a tunable mode having the desired polarization state TE or TM. High-speed polarization switching in the GHz range is possible by inserting passive or active polarization selecting elements in the cavity. Hybrid external cavities are attractive for applications in optical metrology spectroscopy and optical communications.

This paper presents the study of an Erbiua ioped multicomponent glass fibre laser pumped Dy ar Rrgui ion laser. Frequercy tunabiIity is achieved through shift of laser spectra with pump power and fibre Iength.The linewidth of the output and its variation with pump power 'ere Iso studied.

Integrated optoelectronics using 111-V compound semiconductor technology is expected to offer new techniques of interconnection and signal processing within electronic digital systems solving the wiring limit in data communication and processing using the advantages of optical technique such as high data transmission rate and high parallelism. Optical interconnection devices are the key to this and the development is being carried out not only to multiplex a vast amount of data but also to provide flexible interconnection functions. This paper summarizes the role and current status of integrated optoelectronics technology for optical interconnections and signal processing systems. 1.

Array illuminators find wide applications not only as optical distributors for an array of optical devices but also as key elements for optical interconnects . We have evolved a simple and a straight - forward method to fabricate a two - dimensional integrated optic array illuminator that is capable of generating multiple twodimensional beamlets . Two identical plane holographic gratings orthogonal to each other were multiplexed on a photosensitive emulsion coated glass waveguide . On coupling a laser beam from the side opposite to the emulsion multiple parallel beams travelling normal to the surface are generated . Experimental details and results are reported.

- The diffusion coefficient of interdiffusion in InGaAs/GaAs strained quantum wells has been determined as a function of time following implantation with gallium arsenic and krypton ions. All implants were shown to produce some collisional mixing. Gallium implantation produced no enhancement of the intermixing over unimplanted samples whilst krypton implantation produced a factor oftwo increase in the interdiffusion. Arsenic implantation produced a two step diffusion mechanism with a fast initialdiffusion(20 times unimplanted)and a steady state region similar to that observed with krypton implants. I.

The occurrence of the defect structures in heteroepita. xies can be attributed to some low energy configuration of atoms at the interface which also result in specific orientation relationships between the epilayer and the substrate. Here we apply a generalized model to characterize the interfaces of CoSi2 and MoSi2 with silicon and compare the predictions of the models with TEM observations of the defect structure.

In strained Si Ge i-x/Si quantum wells alloy-disorder and intervalley phonon scatterings are found to be weak. The calculated values of mobility are higher than in bulk silicon and closer to the recent experimental data and are mainly limited by deformation potential acoustic phonon scattering. I .

This paper describes the nagative resistance characteristic exhibited by a composite optoelectronic device consisting of a liquid crystal display and a phtoconductor. This characteristic is suitable for memory devices optical pattern generators and special oscillator circuits. Devices like SCR UJT Tunnel diode are known to exhibit negative resistance characteristics and hence electrical bistability (1) A liquid crystal display (LCD) (2) in series with a photoconductor (PC) is known to exhibit optical bistability (3 4). The electrical characteristics of this or any other combination of these devices has to our knowledge not been reported so far. It is found that a parallel combination of these devices exhibits a negative resistance characteristic which is described below. Fig. I Structure of the LCD-LDR optoelectronic device. 274 transparent LCD is connected to a PC in parallel and placed such that the light passing through the LCD falls directly on the PC. The transmmission characteriastic of the LCD is given graphically as shown in Fig. 2. To a first approximation the transmittance T of the LCD can be expressed as T Tmax when A V VB T Tmax - K(V - VB) when VB I '''' T Tmin when VC V VD where I Initially the transmittance of the LCD is Tmax and hence the resistance of the PC is Rein which may be approximately written as Fig. 2 : Transmission composite characteristics of the

A novel but simple high contrast optical switching suitable for display! window applications is demonstrated. The technique is based on electrochromic effect in electrochemically prepared prussian blue (PB) film. The switching action is observed through a colour change from dark blue to total trans prency by simultaneous insertion of K ions and electrons into prussian blue lattice. The device performance and its improvement over the presently known state of the art technology using prussian blue films are also briefly discussed. 1.

The defect mapping system is built on the principle of Scanning Optical Microscope (SOM). It''s essentially an optical probe with an xY translational stage and a Data Acquisition System (DAS). The SOM can be used in three different modes namely Reflection Transmission and Light Beam Induced Current (LBIC). In this paper the instrumentation and it''s capability as SOM and in LBIC mode has been demonstrated. I

The inverse ion-exchange process in glass is studied with the aim of fabricating single mode waveguide devices. Single mode channel waveguides arc fabricated by ion-exchange. The process is modeled using finite difference technique and the effects of various experimental parameters on the refractive index profile of the waveguide are studied.

Indium Phosphide is a semiconductor which is very useful for applications in the field of micro and optoelectronics. Growth of InP bulk sin9le crystals by Liquid Encapsulation Czochralski (LEC) is stil a major problem of scientific and technological importance. The lack of a suitable dopant to reduce the EPD without enhancing the number of free carrier concentration has been eliminated by the addition of codopants, namely Cadmium and Sulpihur. In the present work, it will be shown that it is possible to obtain LEC boules having n-type conductivity over the entire crystal length with a distribution of carriers more homogeneous than in crystals doped, for instance with sulphur alone. The doping procedure adopted leads to a good evaluation of the segregation coefficient of Cadmium in InP. The coefficients reported in the literature are so scattered that it is difficult to set accurately the amount of dopant to be added for obtdining the desired doping level. A variety of dopants have been made use of to understand the nature of dopants and their role in the structural and electrical characteristics of the crystal.

Gallium Antimonide Crystals were grown by the vertical Bridgman technique. The crystals were characterized using Xray analysis EDAX Chemical Etching Hall Effect measurements Photoluminescence spectroscopy and Raman spectroscopy. I

The two-dimensional modeling of the semi-insulating gallium arsenide (SI-GaAs) interdigitated photodetectors is presented. The model considers full bipolar transport, effects of nonuniform carrier generation, field dependent mobilities, carrier diffusion, recombination and includes the effects of the external circuit elements. Dynamic simulation is performed after applying an ideal optical impulse and the simulated response is compared with the experimentally observed response.

A monoli thi c opti cal rcei vex' consisting of an MSM-PD and MESFET anp1ifiez' for near 850nrn wavelength applications has been designed and fabricated on GaAs substrate. The parameters avaluated on fabricated test structures such as 1pm MESFET and MSM-PD were used as the model parameters for receiver circuit simula tion. The mesa epitaxial 1pm MESFET. technology was used for receiver fabrication. The receiver module characterized for output response showed values close to the simulated values of 3dB upper cut-off frequency of 370MHz with a flat trazis impedance of 3.5KQ.

The increased use of high data rate in optical systems brings to stress the receiver performance both in sensitivity and in bandwidth. Among the others the monolithic GaAs technology (MMIC) seems to be extremely suitable for this kind of applications. In order to achieve the best results from this new approach a series of design guidelines are given for Gigabit rate DC coupled transimpedance amplifier used as optical front-end. Two solutions are also presented and experimental results are displayed to confirm the reliability of the theoretical simulation. 1.

Techniques for the generation of far infrared (FIR) radiation through optical mixing process have been discussed. Methods for estimating the phase matching angle angular width of phase matching and power output of the FIR source have been given. Experimental results obtained through optical difference mixing of two orthogonally polarized dye laser frequencies have been quantif ied. 2.

The NETD is calculated in FPN limited MCT FPAs, on the basis of a model in which two-point compensation is used and the readout contribution to FPN is not considered. It is shown that the lowest NETD is obtained when x is about 0.235 in MCT.

Photodetectors with metal-semiconductor -metal (MSM) structures having very high quan turn efficiency are investigated to identify the gain mechanism. From the temperature dependence studies impact ionisation of carriers in a region under the edge of the cathode is shown to be the predominant gain mechanism. Metal-Semiconductors-Metal (MSM) structure has recently emerged" 2 as an attractive device for photodetection due to its simple planar tech nology which can be easily adapted to optoelec tronic integration. The other features of MSM photodetector are their high sensitivity, low capacitance, low dark current and high speed. Substatial amount of work has been done on GaAs MSM photodiodes which are useful in near infrared wavelength regime. Devices with very low dark current (lOOpA at 1OV for 200x200pm geometry) and low rise and fall times (23 and 55 ps respecti vely) have been recently fabricated on semi-insu lating (SI) GaAs substrates1. The other interest ing feature of MSM structure is that it has in ternal gain. Despite intensive study of these devices there is still confusion about the physi cal origin of the gain in these devices. Ito et a13 attribute the gain to hole injection at the forward biased anode contact. Measurements of Zirngibl et al however, point to avalanche mechanism of gain in these devices. In this paper we report the results of experimental in vestigation of gain mechanism in GaAs MSM struc tures which have extremely high gain (100).

The design of a 4x4 switch module of blocking architecture based on Ti:LiNbO3 has been developed and attempts have been made to fabricate the device. The design methodoogy and fabrication details are described. 1.

We report further investigations of the surface electric fields present between the contacts ofan optically controlled silicon switch. The Kerr electro-optic effect and a phase sensitive interferometric analyzer is used to measure the surface fields when a pulsed high voltage is applied across the contacts. The experimental arrangement has a temporal resolution of 100 nanoseconds and a spatial resolution of 50 microns. The experimental results show preferential field enhancement near the anode and the surface electric fields are nonuniform in space and time. The temporal non-uniformity is more pronounced at higher electric fields.

A c irclAl: L mode 1 for Laser diodes based ort nu I C z. mode ra t e eqtiat tons i. s presert t ed hre. be I ay 1 i ries are cornec t ed aL the outpt nodes iduch provide de Lays corresponding to reLative propaation de 1 ays D7i for L aser Lorii LILdZ. ia I modes L!. . ) . n w optical fiber. Th(s modeL s(iruLat. d lASCfl3 th* c(reut s(nwLa LLOTt pacha6e SPICE2. The results were compared with those resuLts by the dtrect rtv soLution of th muLti mode rate equations.

Abstract not available.

Thero-optic coefficients of ADP, KDP and KD*P crystals are aflaly5ed in a physically .eaningful sodel by considering both electronic and lattice effects to coapute optical constants Existing nonlinear optical devices are agreed well and sose devices are proposed by using this iodel and roos teaperature Sellaeier equations

Photoinduced refractive-index gratings are shown to affect the differential phase modulation between the LP and LP11 modes copropagating within the core of a germanium-doped (Ge-doped) two-mode elliptical-core (e-core) fiber. The beat length of fibers containing such gratings is shown to vary as a function of strain applied to the fiber leading to a new type of weighted optical fiber sensor whose sensitivity varies as a function of length along the structure to which it is attached or embedded. This novel type of spatially-weighted distributed fiber sensor is shown experimentally to function as an efficient vibration mode filter by enhancing either the first or second mode of a thin cantilever beam. These results support future applications of spatially-weighted/distributed optical fiber sensors for the evaluation and control of vibrating structures. I.

We present a new method to obtain nuerica1 solutions of the Generalised Nonlinear Schrodinger Equation (GNLSE) which describes nonlinear pulse propagation through optical fibers. The aethod based on the collocation principle is more efficient than the conventionally used FFT based method as we show in this paper through numerical examples. I .

We propose the design of a novel and highly efficient all dielectric three waveguide polarization splitter based on the phenoRenon of resonant tunneling. By consideriang a glass waveguide structure with an intersediate high index guiding layer (such as a i 1 icon) we show that one can obtain extinction ratios better than -30 dB in both the outer waveguides at a particular thickness of the high index layer. The proposed configuration should be of interest in the design of inline fiber optic polarization splitters and in integrated optics. I.

We present here an exact numerical procedure to obtain the propagation constants of multilayer lossy waveguides in which the complex eigenvalue problem is solved in real domain and hence it is most suitable for Personal Computers. We also report a first order technique in which once the real eigenvalue problem is solved the ohmic loss due to a small imaginary part is obtained analytically. 1

M. MukUndaraO Indian Institute of Technology Madras-600 036 V. C. RaVihaiidran and P. Mythill Anna University Madras-600 025 With the increasing use of fluoride fibres tor communication in the infrared region OTDR technique (1) has been extended conceptually for fluoride fibres in the wave length range 1. 5urn - 4urn. OH is found to be the rnajQr contributing factor whose possibility to be monitored by means of an OTDR- are discussed. I NTRODUCT I ON The most exciting prospect for optical fibres made from fluoride glasses is the possibility of prvoldlng long distance optical communication systems without the need for repeaters and amplifiers. ZrF4 baed glasses are pi''ominent in particu I ar 2 rF4-BaF2-LaF3-A I F3-NaF (2BLAN) offer good properties. Considering the various loss mechanisms the outcome is that fluoride based optical fibre exhibits a low loss window at 2. 53 urn with a theoritical minimum loss approaching 0. 04 dB/KM. Fluoride fibres can transmit both infrared and visibie light. They have many applications outside the field of telecommunications including opticai fibres sensors in remote infrared Spectroscopy'' iaser s''rgerv and ribre 119 lasers. Fluoride glass fibres have high transition temperature and refractive indices conpared to silica glass fibres. the of fluorides is that they have a high rate of crystallization which complicates the fibre fabrication process. The reported minimum loss has remained unchanged iP the 2. 5 pm windiw region

We pre8enI i c. spled mode analysis on Cerenku Second Hatrmonic Ceneration(SHG) 1. find osl nsmer ledly the harmonic power planar wave side. B. lh TE and TM modee are considered. The ci. fed of variatien 0/ use g*idc parameters on the cnivcru. n efficiency sa prcacnled. Nmerica1 reaI1a are preP 8enIeifor prolen e:changeililhi*m niohaie(FE:LiNIO6) vdvegvides. Improved cospling c. efficienta are used. Estension of the present s1dy te optical flere ie of lined. I

The refractive-index profile of optical waveguides can be obtained from transmitted near-field intensity measurements by the method of transverse offset scanning. As the calculation of the refractive-index profile from the scalar wave equation requires the second derivative of the field distribution, we developed a modified measurement setup, the modulated transverse offset scanning method.

The present work deals with the performance analysis of an optical FSI( heterodyne receiver einpioying limiter-discriminator detection ( LDD). The analysis is carried out with due considerations to laser phase noise and FM clicks at discriminator output. The receiver performance is assessed from the plots of bit error probability (BEP) versus IF SNR for various combinations of IF bandwidth frequency deviation az laser Jinewidth. The results indicate that an optical heterodyne FSK receiver employing LDD can achieve a BEP floor for suttable combinations of IF banawidth arid frequency deviations with moderate laser linewidths ( 5/. ). This suggests an easier implementation of NCFSK heterodyne optical receivers with a reasonaDie tolerance to the laser phase noise. I.

The prospects of using Coherent Communication techniques is -to increase the inlorniation Capacity of an optical link, which has been widely appreciated for more than 20.years. Earlier, in optical fiber communication systems, ono±'1 intensity modulation and direct photo detection were most commonly ado— pted. In these systems, the receiver sensitivity is limited by the detector and amplifier noi8es. Indeed optical communication systems which use heterodyne or homo—dyne detection are common— ly referred as "Coherent Communication Systems" .

Dispersion in optical fibers and rise time in electro-optic components are very important parameters in the design of high speed optical communication systems. Dispersion parameter is used to determine the bandwidth capability of the optical fiber. Rise time parameter is used to estimate the bandwidth capacity of the overall transmission system comprising transmitter fiber and receiver. Both dispersion and rise time parameters are treated in isolation in technical literature. An approximate relation between these two parameters in conjunction with the bandwidth estimation has been derived and presented in the paper.

This paper describes a model suitable for simulation of optical fiber communication system for transmission of digital data. The model is based on the idea of defining the spectral function for each of the sub-system like transmitter fiber and receiver. To evaluate the system performance an overall spectral function is computed and used as a model for computer simulation. A PC based software is developed using this model. To estimate the validity of the simulation program a set of results were generated using the system parameters obtained from previously published work. The simulation results and the experimental results are found to be very close. The simulation program is also capable of generating eye diagrams for a given set of system parameters.

Several pure optical processing methods have been investigated in order to improve the quality of images from a military environment. Two methods proved unsuitable from the military viewpoint: the well know Vander Lugt matched filter and the classical spatial filtering by a 4f system with coherent illumination. On the other hand two other methods gave encouraging results : pseudocolour encoding of spatial frequencies and cryptography by means of a double aberrating medium. I.

The nature of the diffracted Gaussian'' beam from a photorefractive hologram under the influence of electronic noise is investigated by determining the signa1-tonoise ratio and spatial degradation index of the output. 1.

The present paper reports a simple method for measurement of temporal coherence of a laser using holographically generated phase conjugate wavefront employing an iron doped LiNbO3 (0 . 1 ) crystal . In this method one has to see only the presence of a laser point on the screen rather than to observe interference fringes as in Michelson method. 1 .

The design and performance of a fiber optic sensor working on the principle of evanescent wave absorption are described. Using this sensor the rate of a standard chemical reaction is determined. The measured value is compared with that obtained using a spectrophotometer. I.

At multi-gigabaud rates, the overhead of optical electrical- optical conversion and the limitation imposed by the electronic drive circuitry is unacceptable. Selfrouting, in which the photonic date streams carry their own routing information and bulk of the header processing is achieved by the photonic circuitry, addresses this problem and enables the transmission and switching of data at the full capacity of the optical medium.

The limiting or threshold values of the various parameters affecting the perfor mance of low light level imaging systems have ieen discussed. An attempt has also been made to oztimise the performance of these systems by controlling some of the parameters.

In the present report several implementation of trinary logic functions using three logical values 1 0 and 1 will be presented. Fredkin gate having three input and three output lines has been suggested as a basic building block of an optical computer. In this paper a binary coded trinary (BCT) method has been used to represent each trinary number and several similar logic functions in blocks using Fredkin gates are proposed. I.

In this paper design simulation and optimization of AGC amplifier for the frontend receiver of the high speed optical transmission system have been done. Characterization of Gain Adding Current Dividing and Modified Current Dividing type AGC amplifiers using spread of the transistor parameters as well i. e. frequency response dynamic range and dependence of the output DC level fluctuations on gain variation are investigated and compared. I.

The advantages provided by Photonic Computing has been well documented. An Optical arithmetic processor has to take full advantage of the massive parallelism in optical signals. Such a processor, using the Modified - Signed - Digit (MSD) number . (i) representation, has been presented here based (2) on the symbolic substitution 1ogi. The higher order symbolic substitution rules are formulated for the addition operation, which is carried out in just two steps. Based on the addition operation, the other arithmetic operations - subtraction, multiplication and division - are implemented. Finally, the usefulness of this MSD system is studied.

The analysis of an efficient, low-loss curved single mode optical fiber coupler has been presented. Numerical results for coupling coefficients, effective interactive length and normalized power as a function of minimum spacing, wavelength and offset have been obtained. The coupling effects due to vertkal offset of the fibers have also been determined. This provides an additional design flexibility for the coupler.

Intrinsic ultraweak light emission from cellular nuclei and 2-dimensional photon images obtained on injury to germinating seedlings and mouse are reported and discussed. I.

Self-consistent semiempirical Molecular Orbital Programs MOPAC and MOSOL are used for studying the surface restructuring and energetics of gallium arsenide substrates. The total energy calculations of different cluster sizes to determine the binding energy of surface layer arsenic atoms indicate that proper bulk termination of the surface and inclusion of second nearest neighbors is very important. The comparison of our results with ab initio results is encouraging and indicates the potential of this approach for studying surface restructuring in semiconductors.

Optically tuned GaAs OPFET Is a potential device for integrated Optics Optical Communication and Computing. The transient analysis of an ion implanted GaAs OPFET shows that the carriers generated in the gate depletion region due to absorption of photons attains the steady state value after 40 ps. The D. C. analysis indicates that a analysis normally ON device becomes OFF at a higher negative gate voltage compared to the dark condition and a normally OFF device is opened even at zero gate bias. The drainsource current and the transconductance are significantly enhanced due to optical radiation. In the a. c. analysis the optical radiation is modulated by the signal and hence the number of electronhole pairs generated below the gate is also modulated. So the device properties are greatly influenced by the modulated frequency.

This paper discusses photonic network architectures. The low medium and high bit rate implementations have been described. These include Fiber Distributed Data Interface Distributed Queue Dual Bus and Wavelength Division Multiplexed Networks. iL

Abstract not available.

An automatic and accurate technique for angular positioning of mask with respect to wafer is reported.. Alignment marks are in the form of gratings and the moire signal is obtained by the relative displacement between the gratings. The higher slope region of the moire signal is used to obtain higher sensitivity and better position control accuracy. The experiments are performed with 25 micrometer pitch gratings and Piezo- Electric Transducer is used for the angular displacement. The angular -7 accuracy of the order of 2 x 10 radian is reported with a time constant of 0.2 sec. In the recent years, use of moire interference technique for mask to wafer alignment has attracted much attention especially in VLSI fabrication technology where a highly accurate linear and angular positioning is involved. In this technique the alignment marks are in the form of gratings. A laser beam is passed normally through a mask grating and reflected from the wafer grating. Intensity variation in the reflection mode due to relative angular rotation is detected by a photodetector and converted into the electrical signal, known as moire signal.

Optical characterization of novel photocrosslinkable second-order nonlinear optical (NLO) polymers are presented. These polymer systems have been designed with nonlinear optical moieties in the polymer main chain. When poled and sufficiently photocrosslinked these polymers exhibit relatively stable second-order optical nonlinearity at room temperature. The linear optical and second-order NLO properties of these recently synthesized polymers have been investigated. Second harmonic generation (SHG) was utilized to monitor the temporal stability of the nonlinearity. The linear electro-optic coefficients were measured with a modified Michelson interferometer. 1.

The phenomenon of photosensitivIty in optical fibres covering both Bragg- grating formation and second-harmonic generation is reviewed with emphasis on recent work. Although much is understood more research is necessary to elucidate the mechanisms and unfold the microscopic effects responsible for both observations. This exciting field has grown substantially in past years from fundamental investigations into this curious phenomenon to the applications arena impacting on fibre and semiconductor lasers sensors memory and supervisory application in telecommunications fibre taps and in novel filter applications. Cheap optical fibre frequency converters are a possibility in the future. 1

This paper briefly describes the opto electronics activities at C-DOT. Some of the ongoing activities which are described in this paper are design and development of Synchronous Multiplex Optical Line terminating equipments and regenerators for 'Synchronous Optical Network', low capacity opti cal fibre systems and optical interconnects for varying data rates.

A modification of the Beam PropagationMethod (BFM) is suggested so that only one integral has to be evaluated instead of two for every two iteration. This will reduce computational time as well as errors. Also for a medium whose refractive index does not vary along propagation direction we have suggested a matrix method which takes very less computer time as agaiflst the conventional BPM. The method is applied to the combinar tion of microlens and taper. I

The statistics of the intensity and phase of a Gaussian laser speckle pattern constitutes an important study in several optical systems. Often such a study is limited to the first and second order statistics because calculations of the third and higher order statistics, though striaght forward involve lengthy algebraic manipulations. It is demonstrated that the use of computeraided symbolic manipulations simplifies the calculation of the higher-order correlations, in which research interests are growing. Some examples are given.

In this article we describe the sali ent features of the classical LPE technique with special reference to A1GaAS and InGaAsP. We also review the work of very thin layers for quantum well structures.

The modulation-doped field-ffect transistors (MODFETs) based on 111-V materials have demonstrated low-noise and high power gain performance at millimeter-wave frequencies beyond 100 GHz. Use of these devices for high speed optoelectronic receivers will depend heavily on integrated circuits (OEICs) built with optical detector and transistor amplifier structures. This overview paper examines the limitations of compatible MSM detector diode and a transimpedance amplifying MODFET circuit and projects the performance of a receiver based on them with 23 Gb/s response. I.