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An analysis, based on Jones calculus, is presented of polarization effects in the merged Sagnac-Michelson interferometric sensor for distributed disturbance detection. The nature of birefringence biasing in the Sagnac interferometer is clarified: the cosine-response of the Sagnac interferometer can be biased to a sine-response by introducing birefringence with retardation equal to /spl pi//2 in the Sagnac-loop. In addition, the input light should be linearly polarized and both the direction of polarization and the optical axes of the birefringence region should be oriented at /spl pi//4 with respect to the plane of the fiber-loop.

IR normal transmission and angular reflection spectra are studied for lamellar silicon grating-wafer structures. The grating dimensions are comparable with the radiation wavelengths 2.2–22 μm. The spectra were measured using the FTIR system. Numerical simulations of the spectra were carried out using an operator-vector version of rigorous-coupled wave analysis. The theoretical results are in agreement with the measured spectra. The effect of grating structure on the manifestation of two inherent light absorption mechanisms of bulk silicon-interstitial oxygen vibrations and lattice phonons—is discussed. The results indicate the possibility of obtaining a narrow spectral absorber.

A phase detection system for open-loop fiber-optic gyroscopes which is able to determine the Sagnac phase over several interference fringes is presented. It employs two quadrature signals of the Sagnac phase, as well as an electronic feedback signal that is a first-order estimate of the phase. Linearity is achieved by means of a trigonometric transformation, several of which have been identified, and a first-order control system that generates the feedback signal. The dynamic properties such as ramp and step response of the phase tracker have been studied. It is shown that the introduction of a simple feedforward loop completely eliminates the velocity error which is inherent in the first-order feedback system. For the particular loop gain used in the experimental system, a ramp of 280*10/sup 3/ rad/s could be tracked without detectable velocity error. The introduction of feedforward improved the risetime for a step input of 0.86 rad from 2.4 mu s to 550 ns. >

We describe 'Figure-of-Eight' fibre lasers with NALM (Nonlinear Amplifying Loop Mirror) loops of 100 m, 200 m 300 m highly nonlinear dispersion shifted fibre and 50 m photonic crystal fibre. Apart from the NALM loops the rest of the fibre lasers consisted of normal single-mode fibre (SMF28). The fibre lasers produced mode-locked and Q-switched pulses. By varying the length of the NALM loop we generated a variety of short and long stable high peak power and low peak power pulses in the range from 2 ns to 104 ns. The length of the pulses depends on the length of the NALM loop and the pump diode power. By changing the setting of the polarization controllers we can manipulate the amplitude of the pulses, produce high and low pulses, step pulses, double or multiple pulses. The period of the pulses is equal to the round trip time. We present pulse widths, pulse peak power and spectral measurements in dependence of the pump diode power, and discuss the shapes and spectra of the laser pulses with reference to the transmission curves.

We present a method to design broadband optical transmission filters from complex spectrum profiles, for application in dense wavelength-division multiplexing (DWDM) systems. A discrete inverse scattering method, known as layer-peeling, is used to reconstruct a long-period fibre grating (LPG) structure from a specified realisable complex spectrum by a direct solution of the coupled-mode equations, while simultaneously determining the physical properties of the layered structure. The low algorithm complexity, and relative short computation time when compared to classical grating analysis techniques, are the main advantages of the layer-peeling method. Results obtained from the layer-peeling method, are optimised using the flip-flop refinement method to ease the fabrication process. We also present a method to manufacture symmtrically-written LPGs in optical fibre. The fabrication process is based on the point- by-point method using a continuous-wavelength (CW) carbon-dioxide (CO2) laser to induce the necessary index changes in the fibre core.

Microstructure optical fibres (MOFs) have attracted significant interest because of their unusual optical properties. Therefore MOFs are expected to be integrated within existing optical fibre transmission systems. In this paper, we report on experimental and numerical techniques involved in characterizing the coupling losses of standard single mode fibre (SMF) and MOF. The theoretical results using finite difference full vector beam propagation method (FD-VBPM) are given as a function of the MOF's geometrical parameters and wave properties. In order to compare simulation results and experiment, a simple and reliable setup has been developed in order to study MOFs coupling with SMF using an arc electric splicer. Results show that losses caused by a mode mismatch are particularly sensitive to MOF's characteristics and propagation properties.

We report that a supercontinuum spectrum can be generated in this microstructure optical fibers by Nd:YAG nanosecond laser pulses with central wavelength of 1064 nm and frequency doubled laser yielding pulses at 532 nm. We show that the supercontinuum generation in this MOF is highly influenced the simulated results using full vectorial finite element method that give insight into the physical mechanisms responsible for the supercontinuum generation formation in MOF.

This work is primarily concerned with the utilization of fiber Bragg gratings (FBGs) and chirped long-period gratings (CLPGs) to realize a novel wavelength-tunable optical add/drop multiplexer (OADM) device. We considered the theory of fiber Bragg gratings and long-period gratings to explain the operation of the new device. The method of strain used for tuning of the fiber Bragg grating, channel isolation, and crosstalk between channels are also discussed.

We propose a chirped Bragg grating interrogator for a uniform Bragg grating sensor. The wavelength of light reflected by the sensing grating is a function of strain. The position within the chirped Bragg gating the light is reflected from is a function of its wavelength. We determine this position by amplitude modulating the light source and measuring the phase of the reflected light and thus determine the value of the strain.

Summary form only given. The estimation of film thickness from measured reflectance data for silicon-on-insulator material is discussed. Kamins and Colinge (1986) have proposed a technique whereby the thickness of both the silicon surface layer and the insulator are determined. The method compares the positions of minima in the optical reflectance pattern measured in the visible, to minima obtained by computer simulations of the reflectance curves. Although this method yields good results, it requires either a large amount of computer time or a nomograph for each different insulator thickness. A new technique which employs the frequency content of the transformed reflectance versus inverse wavelength data is presented. There is a significant reduction in the computation burden compared to the above mentioned method. >

Summary form only given. The determination of the surface roughness parameters of nitrogen-implanted silicon for an implant temperature of less than 300 degrees C is discussed. These wafers were implanted to a dose of 8*10/sup 17/ cm/sup -2/ at an energy of 150 keV, annealed at 1100 degrees C, and characterized with a UV-VIS spectrophotometer in the 200-2600 nm wavelength range by measuring the specular reflectance at a 5 degrees angle of incidence. The effects of surface roughness on the reflectance of an unimplanted silicon wafer and a wafer damaged by ion implantation with light ions have been simulated. A comparison of these results to that of the calculated reflectance of implanted silicon and material with a silicon-dioxide surface layer is presented to explain the observed UV-reflectance curves of the SOI material implanted at a low temperature. >

High-temperature material processing is used for a wide variety of applications. These processes often require a specific temporal temperature profile. This design note describes an inexpensive programmable temperature profile controller. The proposed controller is based on an 8051 microprocessor.

Presented is a technique for the continuous tracking of interferometer fringes. The technique uses a fringe quadrature signal to keep the state of the digital tracker in balance with the interferometer state. The quadrature signal is obtained through wavelength modulation of a semiconductor laser.

The effect of surface recombination velocity on the short wavelength response of the tandem junction solar cell is investigated theoretically. The analysis predicts approximately the same dependence of the short-circuit current on surface recombination velocity as for a conventional p-n junction solar cell. It is concluded that the experimentally observed improvement in the blue response of the tandem junction solar cell is probably due to a small surface recombination velocity as a result of the absence of front-surface metallization.

A one dimensional analysis of Poisson's equation is carried out for the metal-oxide-semiconductor buried-channel charge-coupled device (MOSBCCD) and the Schottky-barrier version (SBCCD). This yields a simple design procedure for uniformly doped thin channel devices. The safe design boundaries are fixed by avalanche breakdown and charge containment in the bulk channel. These boundaries are unique functions of the channel parameters and become more critical for highly doped thin-channel devices.

The effects of dielectric dissipation have been included in studies of distributed RC notch filter networks, and it is shown that these may have considerable influence on the magnitude of the optimum notch parameter /spl alpha//SUB 0,1/ and the location of the lowest order optimum notch frequency /spl omega//SUB 0,1/. Voltage transfer function relationships, incorporating a frequency-dependence dissipation factor B(/spl omega/), are given for uniform and exponentially tapered structures. The measured transfer responses of aluminium-silicon monoxide-nichrome evaporated thin-film notch structures were in good agreement with these values predicted. Uniformly distributed RC notch filters exhibited optimum notch attenuations of 71 dB, while exponentially tapered RC filters with taper D=+1 gave 62-dB optimum notch attenuation together with reduced rejection band width.

The energy consumption for a typical solar manufacturing process is discussed. It is shown that by applying laser instead of thermal annealing of the implanted area, 7% of the energy consumption could be saved. Improved solar cells could be obtained by laser annealing

A new type of voltage-controlled tunable distributed RC filter is described by the type metal-insulator-semiconductor-metal. Tuning is attained by field-effect control of the capacitance by a bias voltage, independently of the distributed resistance. Results are given for evaporated thin-film NiCr-Y/SUB 2/O/SUB 3/-CdS-Al filters, together with illustrative applications to tunable RF networks.

A small notch inductance L n in a distributed RC notch filter can drastically shift the location of the optimum notch frequency. Experiments on an A1-Y 2 O 3 - NiCr evaporated thin-film filter yielded a shift of -32 percent in optimum notch frequency by the addition of L n =0.9 µH, in agreement with predictions.

An evaluation is given on the effects of MIS losses and parasitic notch inductance on the tuning-range compression of a voltage-controlled tunable distributed URC notch filter.