Electron beam pattern generators are nowadays used extensively for the production of masks and for direct writing on wafers. For obvious reasons electron beam pattern generators are optimized for integrated circuit fabrication. However there is also considerable potential for the use of electron beam lithography in other areas. In this paper recent trends in the development of electron beam pattern generators are described and the problems encountered in the application of electron beam machines in other areas e.g. integrated optics are discussed.

In this paper an overview is given of the PCVD process as applied for the large scale production of optical fibres for telecommunication. The specific merits and potentials of the process, such as the profile independent high deposition rate and excellent controllability are discribed. The current state of the art of the process, as it is used in the Eindhoven production unit, is a deposition rate of 1 g/min., a preform size equivalent to 28 km of fibre and a drawing speed of 4 m/s. Fibre characteristics are well within the requirements imposed by the telecommunication market. The PCVD process has also proven to be suited for the production of dispersion flattened singlemode fibres and high NA graded index fibres for short distance applications. For both fibre types the high refractive index differences obtained with fluorine doping are exploited. Depending upon the market demands all fibre types can be manufactured at the same productivity. Some trends are given towards further increase of productivity and reduction of fibre costs.

Very high quality GaxIn1-xAsyP1-y (0 < x < 0.47, 0 < y < 1) lattice matched to InP heterojunctions, quantum-wells, and superlattices has been grown by the low pressure metal-organic chemical vapor deposition growth technique. High quality GaInAsP-InP double heterojunction lasers emitting at 1.3 μm and 1.55 μm have been fabricated with threshold current density as low as 430 A/cm2 and 500 Å/cm2, respectively, for a cavity length of 400 μm. Room temperature CW threshold current as low as 6 mA, 8 mA and 12 mA have been measured (for stripe buried devices with cavity length of 300 μm and stripe width of 1 μm) for 1.3 μm, 1.5 μm and 1.55 μm DEB laser, respectively. Phase-locked high power laser arrays of GaInAsP-InP emitting at 1.3 μm have been fabricated with material grown by two step low pressure metalorganic chemical vapor deposition.

GaAs/AlGaAs GRIN-SCH type multiple quantum well lasers with 4 wells of 11 nm GaAs, grown in an MOVPE chimney reactor, exhibit an output power as high as 110 mW/facet (CW, 30°C; 5 μm stripe) and 1.3 W/facet (pulsed, 30°C; 53 μm stripe) until catastrophic optical damage occurs. 2000 hours life tests conducted at 60°C and 15 mW CW show no noticeable degradation for the 5 μm stripe laser with a reflective coating on both facets. Raman spectroscopy on similar multiple quantum well structures with 65 GaAs wells is used to ascertain that the wells have minimum residual aluminum-content.

Realistic theoretical models of quantum well laser performance at both short wavelengths in GaAs/GaAlAs and long wavelengths in InP matched materials have been shown to require a degree of relaxation of the k-selection rule for the optical transition in order to match experimentally obtained spectral gain curves. This can be achieved by the inclusion of lifetime broadening into the calculation of the spectral dependence of the gain. As is discussed, parameters of device performance such as threshold current, gainslope and linewidth enhancement factor are also sensitive to the degree of broadening so that it is important to have a good understanding of the different mechanisms contributing to the broadening energy. The origin of this broadening may lie in both accidental material variations, well width fluctuations for example, or in intrinsic broadening mechanisms such as electron-electron scattering. This paper concludes by introducing results from a relatively simple calculation of the lifetime broadening due to electron-electron interactions for a state in a single parabolic band. Results for 3D systems and 2D systems in the infinite well depth limit are compared and it emerges that the broadening is somewhat enhanced in the 2D system.

The effect of band mixing and non-parabolicity on quantum well gain and spontaneous emission is studied using k.p theory. Spectra of gain and spontaneous emission are strongly modified but the relation of maximum gain versus nominal current density is not strongly affected.

Nonlinear Fabry-Perot switching effects have been observed in a 400μm long GaAs/GaAlAs MQW strain induced waveguide resonator. Experimental evidence showing that the mechanism responsible for the switch has a negative coefficient in the refractive index nonlinearity is described; this rules out the possibility that heating could be the cause of the observed switching. However thermal effects were always present in the background and become more prominent at slow input-power sweep rates. Absorptive bistability has also been observed in a similar non-resonant waveguide structure, at slightly longer wavelengths.

We illustrate the benefits of strained layer structures for long wavelength lasers by considering a laser with 35Å InAs wells in GaAs. The lasing wavelength is close to 1.55μm. The built-in strain ensures that the highest hole band has a low effective mass over more than 3kT at room temperature, with the zone centre hole mass mh = .112. The reduced effective mass leads to the virtual elimination of the two major loss mechanisms in 1.55μm lasers, namely intervalence band absorption and Auger recombination. A threshold current density of Jth = 150 A cm-2 and a To of 120K can be achieved in a separate confinement laser with 3 wells. We conclude that a low threshold current, high efficiency, high To laser can be achieved in a suitable strained layer structure.

The fabrication and performance characteristics of integrated thermally and electronically tunable distributed feedback and distributed Bragg reflector type single wavelength laser diodes are described. Continuously tunable sources of this type are useful for coherent transmission systems.

A simple one-dimensional theory predicts mode selective properties of a semiconductor laser structure consisting of several equally long elements which are separated by regions with different effective refractive index and gain. Measurements on realized lasers with etched and unpumped regions interrupting a ridge waveguide confirm this theory. The best laser shows a side mode suppression of about 25 dB at 1.5xIth and maintains single mode operation under high speed direct modulation.

There is a need to determine the suitability of laser sources for use in coherent transmission systems and to study the spectral characteristics and processes that determine phase and amplitude noise of these sources. A novel method for determining the laser lineshape, linewidth, and phase noise is presented. An optical-fibre, 4 x 4 multiport is used to derive amplitude and phase information of an optical signal by mixing it with a reference optical signal. Signal processing then yields the complex cross-correlation function of the two signals, (or for a single source, the complex auto-correlation function) in the frequency domain. It is intended that information, concerning the amplitude and phase noise of the source or sources, may then be derived or inferred by comparison. The initial system has been designed to operate at 1.55 μm wavelength with a distributed feedback laser.

Propagation modes in four-layer electrooptical waveguides, single mode conversion conditions, have been studied as a function of the electrooptic coefficients and the active and intermediate layer's thickness.

We present a simulation study concerning an optical modulator using the electrooptic (EO) Pockels effect and the prism excitation of a long-range surface plasmon (LSP) at a metal (Ag) - EO medium (CuCl) interface. It is demonstrated that by a proper optimization of the structure paramaters, LSP presents a very narrow ATR resonance. It is then possible to predict a voltage command less than 5 V for a 80 % modulation.

The theoretical investigation of planar dielectric waveguide affected by electric field is presented herein. The electric field modifies refractive index of the waveguide only by means of Pockets effect. As a result, distorted waveguide: causes radiation losses for guided electromagnetic waves in different way for TE and TM modes. The model of step index waveguide- was assumed and calculation of transmission characteristics for TE and TM modes with the Y-cut lithium niobiate plate was done. As a conclusion, some practical applications of electrooptically perturbated waveguide are disaussed.

The effective dielectric constant method is developed for the disc resonator so as to determine its characteristics. Based on this knowledge an interesting possible application of the resonator as a cross point switch is discussed.

The technology and characteristics of a silicon-based polarimeter are presented. This device features guided mode polarization splitting, non-taper solution for guided light detection and electronic signal processing. The overall fabrication process is fully compatible with standard Si technology.

The interaction of light beams and pulses with strongly and weakly nonlinear planar and optical fibre waveguide structures is described. A critique of the predictions of optical bistability/hysteresis, based upon plane waves, is given and a model that builds memory into the calculation is briefly indicated. Several structures are considered and the relevance of the solutions for strongly nonlinear fibres to the stability of the nonlinear field is demonstrated. The behaviour of narrow pulses in birefringent optical fibres is described and full details of the power dependence of the polarisation are given.

In this paper we discuss the characteristics of the nonlinear coaxial coupler and compare the results with the parallel fibre coupler. The coupled differential equations which describe this nonlinear device are investigated for the case where the nonlinear terms are unequal. It is shown that for the coaxial coupler the critical power is greatly modified due to these unequal nonlinear terms.

The analysis and experimental results for weakly perturbed, narrow band, backward wave couplers and fibre reflectors, will be presented. Conventional, co-directional fibre couplers - polished, fused or coaxial - can be designed to demonstrate a sufficient wavelength dependence for some filtering and multiplexing applications. While coupled bandwidths can be sufficiently reduced by weakening the coupling between the guides and hence increasing the interaction (beat) length, useful limits of a few nms are reached for interaction lengths of a few cms. These limitations in coupled bandwidth are considerably transformed for contra-directional coupling provided by a periodic perturbation of suitable pitch (half the guide wavelength) imposed on the coupler. The inverse relationship between bandwidth and interaction length still holds, but the magnitudes are substantially improved. Calculations show that we may expect sub-Angstrom bandwidths for interaction lengths in the order of 1cm. These extremely narrow band effects depend on the successful fabrication of regular, weak, periodic perturbations over relatively long fibre lengths. We have fabricated long gratings (~ 1cm) of periodicity ~ 0.27μm on D-shaped elliptical cored fibres as a first step towards narrow band couplers. These structures can be investigated by observing reflection characteristics at ~ 800nm and the latest results will be described. A contra-directional coupler may then be formed, by joining two dissimilar D-fibres in the polished-coupler configuration with a periodic structure in between them. Additionally, the design of a special twin-core fibre coupler will be described, and its potential as a backward-wave coupler will be examined.

In this presentation a wavelength selective single mode optical switching matrix is reported. The matrix design comprises the use of low loss all-fibre wavelength selective couplers, switches and multiplexers. The matrix is primarily intended for use as a switched wavelength division demultiplexer operating at 1.30 μm and 1.53 μm wavelengths and exhibits insertion losses per path of less than 1 dB.

We consider optical frequency doubling in isotropic single-mode fibres. We show that the non-linear electric quadrupole and magnetic dipole moments can be calculated from first principles and may allow efficient second harmonic generation in single-mode fibres with their long interaction lengths and high power densities.

Short optical pulses have been involved in a number of areas of science and technology. It is now possible to generate optical pulses of less than 10 fs duration corresponding to only a few optical cycles. One of the most important applications of these short optical pulses is in electronics, where, in conjunction with the electro-optic effect, electrical waveforms now can be characterized with a few hundred femtosecond resolution - corresponding to 1 THz in bandwidth. This technique makes possible the characterization in situ of high-speed optoelectronic and electronic devices as well as circuits operating in the picosecond time scale or 100 GHz frequency domain.

The 90psec pulses from a cw mode-locked Nd:YAC laser operating at 1.32μm have been initially shortened to l.5psec by means of a fibre/grating compressor arrangement and subsequently propagated through a negatively dispersive optical fibre to generate, through high-order soliton effects, pulses as short as 33fsec. Input peak power and fibre length variations have been performed and the results compared with theoretical predictions

The physics of low-energy optical switching in both ideal and experimental devices is discussed. Guided-wave optical bistable devices are predicted to have the lowest switching energy per unit gain of any optical switching devices. So far, the bistable diode laser amplifier is the only optical device which can switch with the same switching efficiency as the best electronic device.

Theoretical and experimental studies aimed at low power all-optical bistability in thermal devices are described. Cavities containing semiconductors, liquid crystals and liquids have been investigated. Submilliwatt and laser-diode-induced switching is reported for metal cavities containing strongly thermo-optic liquid crystal material. Aspects of switching dynamics are described.

A guided wave is launched through a nonlinear prism coupler whose prism-waveguide gap is filled with a liquid crystal. We observe that the intensity of the guided wave may exhibit optical bistability. Tests are realized which proove that the loops are true bistable cycles and not only hysteresis. The experimental results are in good agreement with plane-wave calculations. The disagreement with finite-width incident beam calculations is explained by a thermal averaging process within the liquid crystal.

Intensity transmission of GaAlAs strip waveguides embedded in unbiased pn-junctions shows a strong nonlinearity at submilliwatt power levels due to the so-called photo-induced Franz-Keldysh effect. It represents a combination of two well-known effects : the photo-voltaic effect in semiconductor pn-junctions and the common Franz-Keldysh effect. The nonlinearity is typical for bleachable absorption. First-order theory and experiment show good agreement. The effect is used for all-optical switching. The transmitted light power of a probe beam is switched by about 3 dB due to the influence of a control beam at input light power levels of about 0.5 mW each. The switching dynamics is limited by RC time constants.

At 1.06 µm optoelectronic and optical bistability and a clear multistability due to a self-electrooptic-effect is observed in hybrid Si and InP SEED devices. The nonlinearity is traced back to thermal effects which are largely enhanced by the electrical power input. Novel photodetector and modulator devices with high sensitivity and threshold characteristics are found. For a Si-Schottky diode a quantitative comparison with the thermal model and first dynamical measurements of the switch up process are presented.

The dynamical behaviour of semiconductor lasers is investigated at or near a Hopf bifurcation in order to characterise the small-signal amplification properties of the device. The work is discussed within the context of finding practical applications for non-linear dynamical phenomena.

Polymeric glasses have been investigated as a means of incorporating organic molecules into optical waveguides for non-linear optical applications. Polycarbonate thin films, loaded with up to 65% of the organic electo-optical material MBA-NP gave waveguide propagation losses below 3 dB/cm. The nonlinear properties of these films have been investigated.

Semiconductors show often an absorption which increases with increasing laser excitation. If such an induced absorber is put into a ring cavity, one can obtain with constant laser im put an oscillating or chaotically varying output. The frequency locking for the oscillations and the influence of the temporal chaos on the transverse beam profile are described.

The steady state operation of a nonlinear Fabry-Perot (NLFP) for oblique incidence is studied. Depending on the values of the angle and the width of the beam, different theoretical models are proposed. They predict important modifications in the bistable behaviour of the device, which also crucially depend on the state of polarisation of the incident beam.

This paper describes the GaAs semiconductor optoelectronic switch and its application in picosecond streak camera of both metal plate deflector and travelling wave deflector. Finally some results have been obtained as follows: 1. When the GaAs semiconductor optoelectronic switch is lumined by intense laser pulse with duration of 30ps, the fastest leading edge of the electrical pulse measured by picoseco-nd, streak camera is 6.8kv/ns. 2. The streak speed is 3x1O10 cm/s for the metal plate deflector streak tube and 7.6x10 cm/s for the travelling wave deflector streak tube.

We describe a piezo-electrically tunable servo-stabilised Fabry-Perot (FP) filter developed for use in fibre optic systems as a high resolution tunable filter/wavelength demultiplexer. The device has a built-in capacitance micrometer error detector which is used in a closed loop system to servo-stabilise the separation of the FP mirrors and allow hysteresis-free random access wavelength selection.