Showing papers in "Optical and Quantum Electronics in 1988"
TL;DR: In this paper, a picosecond ruby laser pump source was used to generate spontaneous emission and seeding pulses in a longitudinally pumped dye laser generator and amplifiers, and the coherence properties of the generated radiation were analyzed.
Abstract: Picosecond pulse generation in longitudinally pumped dye laser generators and amplifiers is studied experimentally and theoretically. Frequency-tunable pulses between 720 and 940 nm are generated with a picosecond ruby laser pump source. The amplification of spontaneous emission and of seeding pulses in the generator and amplifier cells is investigated. Stimulated emission cross-sections and excited-state absorption cross-sections are determined by computer simulations. The coherence properties of the generated radiation are analysed. Resonance Raman contributions are resolved.
75 citations
AT&T1
TL;DR: The computational requirements and limitations for non-linear optical devices and optical interconnects are spelled out and relationships between the optical properties of devices and their potential computational properties are derived.
Abstract: The promise of digital optical computing is based on massively parallel interconnections between logic gates, which allow for novel architectures, and the possibility of ultrafast switching devices. This paper spells out the computational requirements and limitations for non-linear optical devices and optical interconnects. Relationships between the optical properties of devices (transmission and contrast) and their potential computational properties (fanin and fanout) are derived. The accuracy of the intensity levels required in the system are estimated. The requirements for a minimal device useful for digital optical computing are stated. The ‘volume’ of a device in phase-space limits fanin, switching energy and the degree of space variance in the interconnections. Space-invariant and space-variant interconnections are compared. Limits of random interconnects by volume holograms are discussed.
49 citations
TL;DR: In this paper, the current state-of-the-art of optical pulse compressors based on the optical fiber grating pair is reviewed and the role played by additional non-linear effects (such as stimulated Raman scattering).
Abstract: This article reviews the current state-of-the-art of optical pulse compressors based on the optical fibre-grating pair. As this technique has become a standard laboratory procedure providing pulses with duration shorter than those directly generated from mode-locked lasers, we review the basic mechanism of the method, the role played by additional non-linear effects (such as stimulated Raman scattering), describe the current results, with emphasis to our own work, and point out the limitations of the technique.
35 citations
TL;DR: In this article, the energy required for switching to occur depends on the interaction coefficient as well as the nonlinearity of the coupler, and it is shown that, for a certain input energy, there is no coupling.
Abstract: Non-linear couplers should be important in optical circuitry, especially in switching applications. In a non-linear coupler the oscillation in energy between the two cores depends on the initial light intensity. New effects which can occur in non-linear coupling are presented, using an analysis which includes an interaction coefficient. For a coupler formed from identical guides, the complete forms for the two invariants are given. Energy components are considered, and it is shown that, for a certain input energy, there is no coupling. In this case there is no oscillation in energy levels, so energy launched in one guide will remain in that guide. The energy required for switching to occur depends on the interaction coefficient as well as the non-linearity.
31 citations
TL;DR: This review concerns the development of OEICs based on GaAs systems, and the developed devices such as low-threshold-current quantum-well (QW) lasers, planar-structure metal-semiconductor-metal (MSM) photodiodes and the planar integration process have been developed and used to fabricate multichannel transmit- and receive-OEICs operating at gigabit rates.
Abstract: Optoelectronic integrated circuits (OEICs) in which both optoelectronic and electronic devices are monolithically integrated can exhibit various advantages in improving performance, functionality and reliability. This review concerns the development of OEICs based on GaAs systems. The requirements of integration include the development of devices having high performance and structures suitable for integration, and fabrication techniques for planar, process-compatible integrated structures. Superior devices such as low-threshold-current quantum-well (QW) lasers, planar-structure metal-semiconductor-metal (MSM) photodiodes and the planar integration process have been developed, and these have been used to fabricate multichannel transmit- and receive-OEICs operating at gigabit rates. The applications of such OEICs have been demonstrated in high-speed optical links and 4×4 optical switches. The technological areas expected to be developed further are discussed in view of the future widespread applications of OEICs to communication and signal-processing systems.
28 citations
TL;DR: In this paper, three promising methods of improving temporal coherence in semiconductor lasers are reviewed, which are the development of novel laser devices, a technique of optical feedback and a techniques of electrical feedback.
Abstract: Three promising methods of improving temporal coherence in semiconductor lasers are reviewed. They are the development of novel laser devices, a technique of optical feedback and a technique of electrical feedback. The main discussion in this paper is focused on the technique of electrical feedback. The theoretical limit of frequency stability and recent experimental results are presented with respect to the following five subjects which are indispensable in the realization of highly coherent lasers: (a) frequency stabilization; (b) improvements in frequency reproducibility; (c) linewidth reduction; (d) frequency tracking; and (e) stable, accurate and wideband frequency sweep.
23 citations
TL;DR: In this paper, a review of single-mode channel waveguide lithium niobate integrated optics is presented, and the range of devices and applications in telecommunications, signal processing and sensing are discussed.
Abstract: Recent advances in single-mode channel waveguide lithium niobate integrated optics are reviewed. Fabrication technology, the range of devices, and applications in telecommunications, signal processing and sensing are discussed.
21 citations
TL;DR: In this article, a conical microlens on the end of an Al-coated vapour-axial deposition (VAD) SMF was constructed to improve the coupling efficiency between semiconductor laser diodes and single-mode fibres.
Abstract: The coupling efficiency between semiconductor laser diodes (LDs) and single-mode fibres (SMFs) can be improved by matching their respective modes. This may be achieved by constructing a conical microlens on the end of an Al-coated vapour-axial deposition (VAD) SMF. A simple process to etch an SMF end selectively to produce such a conical microlens is described.
17 citations
TL;DR: A review of experiments on various laser types is given and chaotic emission of lasers theoretically predicted long ago has only recently been experimentally verified.
Abstract: Chaotic emission of lasers theoretically predicted long ago has only recently been experimentally verified. A review of experiments on various laser types is given.
17 citations
TL;DR: In this article, the authors compared the operation parameters between an ordinary-circuitry (OC) excited CuBr laser and the IPC (interacting peaking circuits, IPC) excited CUBr laser.
Abstract: An innovation in CuBr laser excitation causes a significant increase of the output power and laser efficiency The novel electrical circuitry consists of two interacting peaking circuits A comparison of the operation parameters between an ordinary-circuitry (OC) excited CuBr laser and the novel-circuitry (interacting peaking circuits, IPC) excited CuBr laser is made An efficiency of 145% at 174 W average output of the IPC CuBr laser is obtained
15 citations
TL;DR: In this article, the Schrodinger equation (NSE) is used to describe the process of pulse propagation in fibres and subsequent pulse compression in a dispersive delay line.
Abstract: Numerical simulation is used to consider non-linear pulse propagation in fibres and subsequent pulse compression in a dispersive delay line. It is shown that for small initial pulse powers the conventional non-linear Schrodinger equation (NSE) is quite accurate to describe the process of pulse propagation in fibres. In this case initially symmetrical pulses undergo squaring and spectral broadening in fibres, and frequency chirp is linearized over most of the pulse, while shapes of the pulse, spectrum and frequency chirp remain symmetrical at the output of the fibre. There is a certain optimum fibre lengthZopt which is determined by the initial pulse parameters and fibre characteristics for pulse compression in the dispersive delay line. When the fibre lengthZ>Zopt the optical wave breaking effect distorts the linearity of the frequency chirp and thus deteriorates the quality of the compressed pulse. The region of NSE approximation accuracy is determined. It is demonstrated that at increase of the initial pulse power (initial pulse width makes no difference) the NSE approximation becomes inaccurate. So the pulse dynamics in the fibre were described by the modified NSE derived in the higher-order approximation of the method of slowly varying amplitudes from Maxwell's equations. In this case the shock wave appears at the trailing edge of the pulse, which accelerates the wave breaking process. This results in a decrease of the optimum fibre length and deterioration of compressed pulse parameters, compared with the NSE case. Spectral windowing of the extreme Stokes components of the pulse spectrum permits significant improvement in the quality of the compressed pulse. The main features of the compression of pulses with asymmetrical initial shape are also considered.
TL;DR: In this article, a parabolic model of the formg =αn2 +βn +γ has been suggested for long-wavelength InGaAsP laser diode peak-grain coefficient variations with the carrier density.
Abstract: A parabolic model of the formg =αn2 +βn +γ has been suggested for long-wavelength InGaAsP laser diode peak-grain coefficient variations with the carrier density. The parametersα,β andγ, which are dependent on doping, bandgap-wavelength and temperature, have been calculated by applying the least-mean-square method to fit the results of the Lasher and Stern theory of the recombination in semiconductors. p ]This model is superior to the commonly used linear model in accuracy and range of applicability.
TL;DR: In this paper, a theoretical investigation of a two-section single-cavity (TSSC) laser was carried out to demonstrate its potential as a frequency-tunable laser source.
Abstract: This paper reports on a theoretical investigation of a novel scheme devised for a two-section single-cavity (TSSC) laser. The results of the investigation are used to demonstrate its potential as a frequency-tunable laser source. By the implementation of an appropriate electrical drive scheme the TSSC laser can be shown to exhibit a reduction in frequency chirping under direct modulation. Alternatively, by employing a different drive scheme, the device can be shown to behave as a wavelength-tunable laser. Control of the tuning range by antireflection (AR) coating of laser facets is also predicted.
TL;DR: In this article, the optical characteristics of the asymmetric metal-clad waveguide are analyzed, and more accurate formulae are derived for calculating the propagation constants and loss coefficients of TE and TM modes.
Abstract: The optical characteristics of the asymmetric metal-clad waveguide are analysed, more accurate formulae are derived for calculating the propagation constants and loss coefficients of TE and TM modes. The computed results for Al/GaAs/AlGaAs waveguides are in good agreement with the numerical results, and are much more accurate than the results in some other papers. The method for selecting the TE0 mode is presented and discussed.
TL;DR: In this paper, the operation and optimization of soliton Raman fiber-ring lasers using a c.w. mode-locked Nd-YAG laser at 1.32μm as the source of 100 ps pump pulses were presented.
Abstract: Results are presented on the operation and optimization of soliton Raman fibre-ring lasers using a c.w. mode-locked Nd-YAG laser at 1.32μm as the source of 100 ps pump pulses. Various lengths of standard single-mode silica fibre were used, and tunable pulses as short as 100 fs generated.
TL;DR: In this article, the phase-matched third-harmonic light generation in dye solutions was studied experimentally and theoretically, and it was shown that up to 4×10−4 was achieved for one of the dyes investigated.
Abstract: The phase-matched third-harmonic light generation in dye solutions is studied experimentally and theoretically. In the experiments picosecond light pulses of a passive mode-locked Nd-glass laser are converted to the third-harmonic frequency. A third-harmonic conversion efficiency of up to 4×10−4 was achieved for one of the dyes investigated (1,3,3,1′,3′,3′-hexamethylindocarbocyanine iodide in hexafluoroisopropanol). The theoretical calculations determine the influence of various dye and solvent parameters on the conversion efficiency. The conversion efficiency is found to be limited by excited-state absorption of pump laser light and third-harmonic light from the S1-state to higher singlet states. The S1-state is mainly populated by two-photon absorption. Amplified spontaneous emission may reduce the limiting effects of excited-state absorption. Phase changes caused by the non-linear refractive index and the refractive index dispersion within the spectral bandwidth of the laser pulses reduce the conversion efficiency. Under ideal conditions conversion efficiencies up to 10% may be achieved.
TL;DR: In this article, the maximum number of connectable laser diode optical switches (LDSWs) was studied through the baseband signal-to-noise ratio calculation, and 60 stages of LDSWs were connected with a 6-nm optical bandpass filter inserted after the last stage at an input signal level of −30 dB m and an internal gain of 16 dB.
Abstract: The maximum number of connectable laser diode optical switches (LDSWs) was studied through the baseband signal-to-noise ratio calculation. For an NRZ 100 Mbits−1 PCM-IM signal, 60 stages of LDSWs can be connected with a 6-nm optical bandpass filter inserted after the last stage at an input signal level of −30 dB m and an internal gain of 16 dB. A PCM-IM signal of 10 Gbits−1 can be transmitted through 130 stages of LDSWs at an internal gain of 8 dB and an input signal level of −20 dB m.
Abstract: Using an iterated moment method (weighted index method), formulae are derived for the accurate calculation of the dispersion characteristics and field distributions of guided modes in strip dielectric waveguides and strip-loaded waveguides, and for the calculation of the coupling length of rectangular-core dual-channel directional couplers The formulae are simple and the results obtained by the present analysis agree well with computer-aided exact numerical analysis This method can be readily extended to the analysis of other dielectric waveguide structures
TL;DR: In this paper, a method is proposed for studying laser dynamics, which relies on periodical inversion modulation in its active medium with the aid of external radiation, and the possibilities of this approach are shown in determining the most important dynamic parameters of a laser system, such as the frequency of natural relaxation vibrations, the resonance curve width, the inversion relaxation rate and the saturation parameter.
Abstract: In this paper a method is proposed for studying laser dynamics, which relies on periodical inversion modulation in its active medium with the aid of external radiation. Through the example of a CO2 laser, the possibilities of this approach are shown in determining the most important dynamic parameters of a laser system, such as the frequency of natural relaxation vibrations, the resonance curve width, the inversion relaxation rate and the saturation parameter. The main advantage of this method is that it does not require the introduction of additional losses into the cavity, yet it permits investigation of the laser transfer characteristics over a wide range of frequencies. Such measurements are very important in making intracavity investigations. They also make it possible to predict the level of technical fluctuations and to carry out internal modulation and stabilization of the radiation power which is essential in developing laser systems for various practical applications.
TL;DR: In this article, a divided-pump four-photon mixing process was used to investigate the behavior of modes on a bent few-mode optical fiber, and the second-order mode set became non-degenerate, even for slight bending.
Abstract: A divided-pump four-photon mixing process is used to investigate the behaviour of modes on a bent few-mode optical fibre. The second-order mode set becomes non-degenerate, even for slight bending; the two modes propagate along the fibre with different group delays and preferred axes of symmetry. Our experimental results are compared with a theoretical analysis.
TL;DR: In this paper, 50 percent modulation was observed in Schott Glass OG530 semiconductor doped filter glass with a c.w. argon-ion laser, with the balance between them being dependent on sample temperature, modulation frequency and light intensity.
Abstract: Fifty percent modulation was observed in Schott Glass OG530 semiconductor doped filter glass with a c.w. argon-ion laser. Laser-induced clearing and darkening were also detected, the balance between them being dependent on sample temperature, modulation frequency and light intensity.
TL;DR: In this article, the performance of a flowing gas CO2 laser is analyzed and compared with a theoretical model which takes into account the gas flow rate and the CO2 decomposition, and particular attention has been devoted to the characteristics of slow gas flow as a function of the gas mixture composition.
Abstract: The performance of a flowing gas CO2 laser is analysed and compared with a theoretical model which takes into account the gas flow rate and the CO2 decomposition. Particular attention has been devoted to the characteristics of slow gas flow as a function of the gas mixture composition.
TL;DR: Optical fibres with organic single-crystal cores offer the potential for efficient second harmonic generation (>50%) and high amplification gain (>35 dB) when centimetre-long devices are pumped by semiconductor lasers of just a few milliwatts of power output as discussed by the authors.
Abstract: Optical fibres with organic single-crystal cores offer the potential for efficient second harmonic generation (>50%) and high amplification gain (>35 dB) when centimetre-long devices are pumped by semiconductor lasers of just a few milliwatts of power output
TL;DR: In this paper, the InGaAsP/InP system which is monolithically integrated with opto-electronic and electronic devices is discussed and the technological problems for the development of the OEICs are explained.
Abstract: Recent developments in opto-electronic integrated circuits (OEICs) using the InGaAsP/InP system which is monolithically integrated with opto-electronic and electronic devices are discussed. The technological problems for the development of the OEICs are explained by reviewing recent developments in OEICs.
TL;DR: In this article, the electrical characteristics of a small volume-discharge of standard XeCl laser gas mix was studied using a PFL (pulse-forming line) of conveniently changeable output impedance ZO.
Abstract: Through the use of a PFL (pulse-forming line) of conveniently changeable output impedance ZO, the electrical characteristics of a small volume-discharge of standard XeCl laser gas mix was studied. The impedance ZD from a 2×0.5×1(=1) cm3 discharge was found to be about 10Ω. A PFL of very low impedance is therefore rather inefficient in driving the discharge, because of the impedance mismatch and the slower current rise time. The data presented will be useful for the design of excimer lasers of small discharge volume, which find applications in serving as master oscillator or in high repetition rate operation.
TL;DR: In this article, the authors investigated the splicing of graded index tapers to dissimilar waveguides, and derived a simple formula for the coupling efficiency, which clearly reveals the loss due to mismatch of spot-size and the curvature of the wavefronts.
Abstract: Marcatili has proposed a class of graded-index (GRIN) tapers which do not radiate along their length. We investigated the splicing of such tapers to dissimilar waveguides, and derive a simple formula for the coupling efficiency, which clearly reveals the loss due to mismatch of spot-size and the curvature of the wavefronts.
TL;DR: In this paper, a simple approach for the analysis and design of ring cavities for c.w. passively mode-locked dye lasers is suggested based on the representation of the intracavity beam as a series of two matched beams, each considered to be formed in a linear cavity configuration.
Abstract: A simple approach for the analysis and design of ring cavities for c.w. passively mode-locked dye lasers is suggested. The approach is based on the representation of the intracavity beam as a series of two matched beams, each considered to be formed in a linear cavity configuration. Useful expressions are obtained for the cavity parameters in terms of the intracavity beam properties of interest for two different beam configurations. The expressions can be used for the correct design of ring resonators.
TL;DR: In this paper, a bit error rate floor for DPSK heterodyne optical systems is evaluated, considering the actual shape of the emission line of single-mode semiconductor lasers considering a strictly Lorentzian shape can give rise to relevant errors.
Abstract: A bit-error rate floor for DPSK heterodyne optical systems is evaluated, considering the actual shape of the emission line of single-mode semiconductor lasers Considering a strictly Lorentzian shape can give rise to relevant errors in the design of the above systems An ‘equivalent linewidth’ is introduced which, when accounted for in the formalism usually adopted, allows the correct results to be obtained