Showing papers in "IEEE Journal of Quantum Electronics in 1981"
TL;DR: In this paper, a general discussion of the free-electron lasers (FEL's) with variable parameter wigglers is presented with a view towards their potential for the production of high power optical radiation at reasonable efficiency.
Abstract: A general discussion of the free-electron lasers (FEL's) with variable parameter wigglers is presented with a view towards their potential for the production of high power optical radiation at reasonable efficiency. The theoretical analysis is based upon a one-dimensional relativistic Hamiltonian formulation and is developed in a manner to take advantage of the analogy between the FEL process and radio frequency accelerators. Three promising operational modes are identified and analyzed. The first may be thought of as an electron decelerator and is thought to have the most promise for single-pass devices. Both oscillator and amplifier configurations are studied. The second is based upon adiabatic trapping and detrapping, intended to reduce the spread in electron energy typically induced by the FEL process. The third is based upon the method of phase area displacement. It has the advantage of wide gain bandwidth and small induced energy spread, and is thought to have the most promise for storage ring applications. Generally speaking, it is found that high peak power is intrinsic to these modes of operation. Potential problems from parasitic oscillations analogous to the stimulated Raman effect are analyzed, and some others arising from transverse inhomogeneity are identified.
530 citations
TL;DR: In this paper, the nature of random coupling between normal modes of polarization is analyzed and discussed in connection with various applications, such as fibers with very small or very large birefringence for polarization dependent applications.
Abstract: Recent research on fibers with very small or very large birefringence for polarization-dependent applications is reviewed. The nature of random coupling between normal modes of polarization is analyzed and discussed in connection with various applications.
501 citations
TL;DR: In this paper, the feasibility of coherent optical fiber transmission systems was studied from the view point of device and system consideration and expected performance, in which laser coherence is utilized to carry information.
Abstract: The feasibility of coherent optical fiber transmission systems, in which laser coherence is utilized to carry information, are studied from the view point of device and system consideration and expected performance. Modulation scheme comparison among optical ASK, FSK, and PSK, transmitter and receiver configurations, single-polarization transmission through fibers, problems in providing stable local oscillator waves, and wide-band photodetectors are discussed together with alternative technologies to realize high performance systems. A study on digital system impairments caused by FM quantum noise of laser oscillators, interferometric FM-AM conversion noise, IF frequency fluctuation, and optical fiber transmission turbulence show the feasibility of the systems. Repeater spacing is estimated by considering the transmitting and receiving signal levels, optical fiber loss, and fiber transmission capacity. Repeater spacing of 240 km is feasible by 400 Mbit/s PSK homodyne-detection system and 220 km by 400 Mbit/s FSK heterodyne-discrimination detection system. The regenerative repeater spacing can be expanded further by employing intermediate repeaters with direct optical signal amplification. Based on the performance of semiconductor laser amplifiers, such as traveling wave type, Fabry-Perot cavity type, and injection locked devices, it is estimated that regenerative repeater spacing of more than 104km is feasible with 50 km intermediate repeater spacing. These systems will find application in transoceanic optical fiber cable transmission as well as terrestrial long distance transmission systems.
384 citations
TL;DR: In this paper, an external-cavity semiconductor laser was used as the gain medium for an injection laser with a stripe-geometry double-heterostructure diode.
Abstract: Experiments with an external-cavity semiconductor laser indicate that single-frequency oscillation may be obtained in an injection laser when the gain is temporally and spatially stabilized within the active region. Using an originally multimode laser diode as the gain medium, the external-cavity laser oscillates stably in the fundamental spatial mode and in a single longitudinal mode with a frequency which is tunable over a 10 nm spectral range. The rms frequency jitter of the unstabilized laser is 500 kHz. These mode characteristics suggest that spatially inhomogeneous gain saturation is significant only in the lateral direction in the active region of a stripe-geometry double-heterostructure laser diode. A quantitative analysis of the spontaneous emission in the spectral vicinity of the lasing mode shows no evidence of spectral hole burning, with a 0.5 percent upper limit to the depth of the hole burned in the gain spectrum by a lasing mode power of 5 mW.
353 citations
TL;DR: In this article, a light single-sideband modulator, or frequency shifter, of integrated optics structure is proposed, which is confirmed by constructing and testing the device using Ti indiffused LiNbO 3 waveguides.
Abstract: A novel light single-sideband modulator, or frequency shifter, of integrated optics structure is proposed. The operation was confirmed by constructing and testing the device using Ti indiffused LiNbO 3 waveguides. The first demonstration of frequency shifting was carried out at 2 GHz, and either the upper or lower single-sideband output without carrier was obtained. Conversion efficiency of -5 dB was achieved with input drive power of 730 mW.
331 citations
TL;DR: In this paper, the current status of guided-wave optical communication devices is reviewed and the operation and presently demonstrated performance characteristics of waveguides switches, modulators, filters and polarization transforming devices are discussed.
Abstract: We review the current status of guided-wave optical communication devices. The operation and presently demonstrated performance characteristics of waveguides switches, modulators, filters, and polarization transforming devices are discussed. Emphasis is given to recent developments with very high speed modulators and polarization insensitive devices.
294 citations
TL;DR: In this article, the nonlinear wave equation and self-consistent pendulum equation are generalized to describe free-electron laser operation in higher harmonics; this can significantly extend their tunable range to shorter wavelengths.
Abstract: The nonlinear wave equation and self-consistent pendulum equation are generalized to describe free-electron laser operation in higher harmonics; this can significantly extend their tunable range to shorter wavelengths. The dynamics of the laser field's amplitude and phase are explored for a wide range of parameters using families of normalized gain curves applicable to both the fundamental and harmonics. The electron phase-space displays the fundamental physics driving the wave, and we use this picture to distinguish between the effects of high gain and Coulomb forces.
248 citations
TL;DR: In this article, the authors measured the dispersion of a single-mode optical fiber only 1 m long by a newly proposed interferometric method, where interference fringes are produced by two laser beams, one transmitting through the fiber and the other through air.
Abstract: Chromatic dispersion of a single-mode optical fiber only 1 m long is measured by a newly proposed interferometric method. Interference fringes are produced by two laser beams, one transmitting through the fiber and the other through air. Path length shifts in an interferometer for attaining the visibility maximum are measured by varying optical source wavelengths between 818 and 904 nm. Group delay time differences around 1 ps are measured. The measured results are in good agreement with those measured by the conventional pulse method for the identical 1.3 km long fiber.
218 citations
TL;DR: In this paper, the authors studied the relation of the locking bandwidth versus the ratio of locked laser power to injected power in AlGaAs double-heterostructure (DH) laser systems.
Abstract: Injection locking of AlGaAs double-heterostructure (DH) lasers was studied with respect to locking bandwidth, required power, and coherence. The relation of the locking bandwidth versus the ratio of locked laser power to injected power was consistent with the classical analysis on injection locking phenomena reported by Adler [2]. The measured maximum locking bandwidth was 5.8 GHz when the locking gain was 18 dB. A maximum gain of 40 dB was observed with a 500 MHz locking bandwidth. The power increase in the injected mode agrees well with theoretical values calculated with the van der Pol equation. The interference pattern was observed between an injecting beam and a locked laser beam. Visibility was the same as that obtained by the interference between forward and backward emitted beams in an identical free-running laser. Spurious mode suppression was observed when a single-frequency optical power is injected into an RF-modulated laser. Single longitudinal mode operation was obtained at a sufficiently high injecting level.
216 citations
TL;DR: In this paper, the effects of twist in an elliptical core fiber gave rise to a polarization whose major axis points in an intrinsic direction with an azimuthal angle, where φ t is the torsion per unit length and z is the fiber length.
Abstract: Birefringence and polarization dispersion caused by: 1) elliptical core, 2) twist, 3) pure bending, 4) transverse pressure, and 5) axial tension are studied by treating these deformations as perturbations to step-index single-mode fiber with a round core. These effects ate formulated in terms of fiber structure and perturbation parameters and are compared comprehensively. Birefringence depends strongly on factors 1)-4), while polarization dispersion depends on factors 1), 3), and 4). Polarization performance of twisted elliptical core fibers was also studied. Twist in an elliptical core fiber gives rise to a polarization whose major axis points in an intrinsic direction with an azimuthal angle \phi_{t}z , where φ t is the torsion per unit length and z is the fiber length.
TL;DR: In this paper, a theory of optical bistability for a Fabry-Perot cavity containing a medium with nonlinear refraction but linear absorption with only plane-wave and slowly varying envelope approximations is presented.
Abstract: We present a theory of optical bistability for a Fabry-Perot cavity containing a medium with nonlinear refraction but linear absorption with only plane-wave and slowly varying envelope approximations. An analytic expression for the critical intensity I c for the onset of bistability is derived and used to compare cavity designs. It is shown that 1) the important material parameter for minimum I c is the ratio n_{2}/\alpha 2 ) the limit to I c is set by limitations on finesse due to inhomogeneities rather than the absorption itself, and 3) the cavity design which gives lowest I c for a given finesse is that for which the mirror transmissivity equals the absorption per pass; at high finesse this design leads to a total peak cavity transmission of 1/4 when mirror reflectivities are equal.
TL;DR: In this article, a finite element method was used to calculate modal birefringence due to thermal stress and/or stress caused by external forces in noncircular core fibers.
Abstract: Stress-induced birefringence in single-mode optical fibers having arbitrary shape of core has been investigated using a finite element method. The calculated modal birefringence due to the thermal stress and/or stress caused by external forces in noncircular core fibers is compared with the values obtained by measurement of polarization properties, showing good agreement.
TL;DR: In this paper, a comparison of three schemes (angle-detuned, polarization-mismatch, and polarization-bypass) permitting high efficiency frequency tripling of 1 μm laser radiation is made.
Abstract: A comparison is made of three schemes ("angle-detuned," "polarization-mismatch," and "polarization-bypass") permitting high efficiency frequency tripling of 1 μm laser radiation. The overall characteristics of each are examined in terms of sensitivity to input intensity, polarization angles, and mismatch angles. The "polarization-mismatch" scheme is favored for tripling current high-power 1 μm Nd:glass laser radiation with KDP crystals, while for future systems the "polarization-bypass" scheme may be optimum. All schemes permit the tripling of some shaped pulses without substantial degradation in efficiency. The theory of tripling in KDP is reviewed.
TL;DR: In this article, the authors considered the temperature dependence of the threshold current of GaInAsP/InP lasers in terms of linear gain, loss, and carder lifetime, taking into account electronic intraband relaxation effects.
Abstract: The temperature dependence of the threshold current of GaInAsP/InP lasers was considered in terms of linear gain, loss, and carder lifetime. The linear gain was calculated taking into account electronic intraband relaxation effects. The carrier lifetime, intraband relaxation time, loss in the active region, and dipole moment, all of which determine the threshold condition, were estimated from the experiments. The main loss mechanism which determines the temperature dependence of the differential quantum efficiency appears to be the absorption due to transitions between the split-off and heavy-hole valence bands. The temperature dependence of the theoretical threshold current I th calculated in terms of these parameters was compared with the measured results and reasonable agreement was obtained.
TL;DR: In this article, a phase matching with the positive dispersive tare gas Ar or Xe was proposed to improve the efficiency of the conversion of negative dispersive Kr to positive dispersion Xe by two orders of magnitude.
Abstract: Nonresonant frequency tripling of intense dye laser radiation in negative dispersive Kr ( \lambda = 1203-1235 A ) is efficiently enhanced by phase matching with the positive dispersive tare gas Ar or Xe. Phase matching of Kr with Ar improved the efficiency of the conversion of 3648 A to L_{\alpha} = 1216 A by more than two orders of magnitude. At L_{\alpha}, 16 W ( 4 \cdot 10^{10} photons/pulse) could be generated with 1.5 MW pulses of a frequency doubled dye laser. The optimum conversion is limited by absorption of the VUV in the rare gas mixture and by dielectric breakdown. In mixtures of Kr and Xe, the dependence of the VUV on the density of the two gas components indicates a phase difference between their contributions to the induced third-order polarization. Measurements of the VUV output of different Kr-Xe mixtures provide a determination of the ratio of the third-order nonlinear susceptibilities χ Kr /χ Xe and of the wave vector mismatches per atom C Kr /C Xe at wavelengths \lambda = 1205-1230 A Besides frequency tripling in Kr, third-harmonic generation of blue dye laser light ( \lambda = 4208-4406 A) has been investigated in Xe phase matched with Kr. The peak power of the tunable VUV at \lambda = 1403-1469 A exceeded 30 W ( 8.7 \cdot 10^{10} photons/pulse).
TL;DR: In this paper, the band-to-band Auger recombination effect on the threshold current in an InGaAsP laser is studied theoretically and an approximation method for the calculation is derived and the Auger lifetime is obtained numerically in the framework of the k-p perturbation method for band structure calculation.
Abstract: The band-to-band Auger recombination effect on the threshold current in an InGaAsP laser is studied theoretically. An approximation method for the calculation is derived and the Auger lifetime is obtained numerically in the framework of the k-p perturbation method for band structure calculation. Gain factor and radiative lifetime are calculated by using Stern's method, which involves the band tailing caused by injected carriers. Calculated carder lifetime, quantum efficiency, and threshold current density for the 1.27 μm InGaAsP laser agree well with reported experimental values. The calculated characteristic temperature T 0 and the break point temperature T B are compared with experimental values for InGaAsP lasers with a variety of compositions. The comparison shows that the Auger recombination is one of the dominant effects in determining the threshold current of InGaAsP lasers.
TL;DR: In this paper, the authors measured the impact ionization coefficients α (electrons) and β (holes) with different composition and temperature and found a resonant enhancement of the hole ionization coefficient for x = 0.065 (300 K) where the ratio α/α exceeds values of 20.
Abstract: The liquid-phase epitaxy and device fabrication of p-n and p-i-n Ga 1-x Al x Sb avalanche photodiodes is described. Breakdown voltages up to 95 V and dark currents of 10-4A/cm2have been obtained. With p-i-n diodes we have measured the impact ionization coefficients α (electrons) and β (holes) with different composition and temperature. A resonant enhancement of the hole ionization coefficient is found for x = 0.065 (300 K) where the ratio \beta/\alpha exceeds values of 20. This effect is attributed to impact ionization initiated by holes from the split-off valence band: if the spin orbit splitting Δ is equal to the bandgap energy E g , the threshold energy for hole initiated impact ionization reaches the smallest possible value ( E_{i} = E_{g} ) and the ionization process occurs with zero momentum. This leads to a strong increase of β at \Delta/E_{g} = 1 . The experimentally determined dependence of ionization coefficients on threshold energy is compared with theoretical expectations.
TL;DR: In this article, the effects of diffusion, generation-recombination (GR), and the recently observed tunneling currents on the performance of photodiodes made from In 0.73 Ga 0.27 As 0.63 P 0.37 and 0.53 ga 0.47 As.
Abstract: We present a theoretical study of the effects of diffusion, generation-recombination (GR), and the recently observed tunneling currents on the performance of photodiodes made from In 0.73 Ga 0.27 As 0.63 P 0.37 and In 0.53 Ga 0.47 As. Calculations are made for both p+ν and p-i-n punch-through diode configurations, and are compared with recent measurements made by several independent investigators. For doping densities typical of present material ( N_{D} \gsim 10^{15} cm-3), tunneling currents become dominant prior to avalanche breakdown. Thus, for detection of weak (-55 dBm at 45 Mbits/s) optical signals, the diodes must be operated at low voltages where GR is the dominant source of reverse-biased leakage. To meet the requirements of low capacitance ( C \leq 0.5 pF for a diode area of 10-4cm2) and low GR dominated dark current ( I_{D} \leq 10 nA at T = 70\deg C), the doping density and effective carrier lifetime (τ eff ) must be N_{D} cm-3and \tau_{eff} \gsim 150 ns for In 0.73 Ga 0.27 As 0.63 P 0.37 and 5 \times 10^{14} \lsim N_{D} \lsim 7 \times 10^{15} cm-3and \tau_{eff} \gsim 3.5 \mu s for In 0.53 Ga 0.47 As.
TL;DR: In this paper, a theory for the steady-state behavior of the external-cavity semiconductor laser taking into account such coherent optical effects is developed, and the inclusion of these effects is also important in the interpretation of the threshold data of such lasers.
Abstract: A broadening of the apparent linewidth of the semiconductor laser modes with external optical feedback is observed. This is shown to be due to the coherent nature of the feedback and multiple reflections in the external cavity. A theory for the steady-state behavior of the external-cavity semiconductor laser taking into account such coherent optical effects is developed. The inclusion of these effects is also important in the interpretation of the threshold data of such lasers.
TL;DR: In this article, the basic electrical equivalent circuit of a laser diode is derived and the effects of spontaneous emission and self-pulsations are represented by a negative resistance in the model.
Abstract: The basic electrical equivalent circuit of a laser diode is derived. The effects of spontaneous emission and self-pulsations are included. It is found that self-pulsations are represented by a negative resistance in the model. Application of this model suggests purely electronic methods of suppressing relaxation oscillations in laser diodes.
TL;DR: In this article, a new coupling method of a laser diode to a single-mode fiber is described, which consists of a spherical ruby lens and a graded index (GRIN) rod lens positioned under a confocal condition.
Abstract: A new coupling method of a laser diode to a single-mode fiber is described. It consists of a spherical ruby lens and a graded index (GRIN) rod lens positioned under a confocal condition. A high coupling efficiency of more than 40 percent has been easily obtained for InGaAsP laser diodes. Alignment sensitivities of the proposed coupling circuit have been studied both experimentally and theoretically. The dependence of the coupling efficiency on misalignments has been found to be in agreement with the theoretical consideration, and it has been apparent that the stringent alignment tolerances required for conventional coupling methods have been overcome. A laser diode module using the proposed circuit was also fabricated with high coupling efficiency into the single-mode fiber, and good reproducibility and performance have been obtained.
TL;DR: In this paper, the authors describe the theoretical and experimental study of an optical time domain reflectometry (OTDR) in a single-mode fiber and the maximum measurable distance by the OTDR is theoretically studied.
Abstract: This paper describes the theoretical and experimental study of an optical time domain reflectometry (OTDR) in a single-mode fiber. The maximum measurable distance by the OTDR is theoretically studied. In the experiment, the cylindrical lens attached to the laser diode, the low-loss and low-crosstalk directional coupler, and the digital averaging technique combined enabled us to measure a break in a single-mode fiber up to 17 km in length. This paper also describes the application of the OTDR to loss measurement of a single-mode fiber.
TL;DR: Theoretical stationary and transient temperature rises are calculated using Fourier and Laplace transformations as discussed by the authors, where the effects of inhomogeneous heat flow to a submount and heat radiation from the diode surface into the ambient atmosphere are taken into account in the calculation.
Abstract: Numerical analyses and experimental results on thermal behavior of AlGaAs laser diodes for CW and modulated operations are presented. Theoretical stationary and transient temperature rises are calculated using Fourier and Laplace transformations. Effects of inhomogeneous heat flow to a submount and heat radiation from the diode surface into the ambient atmosphere are taken into account in the calculation. Thermal resistances of laser arrays are also discussed. Experimental temperature behavior at the active layer is obtained from the wavelength shift measurement of an oscillation mode using a birefringent filter, which provides fast and precise measurement. Three components of temperature rise are observed in step and periodic responses. Numerical and experimental results are in good agreement.
TL;DR: In this article, the Hamiltonian picture of the free-electron laser (FEL) was reexamined and the multielectron effects were accounted for in the low-gain regime.
Abstract: The Hamiltonian picture of the free-electron laser (FEL) is reexamined and the multielectron effects are accounted for. The conditions under which the multieleetron effect can be neglected are made precise (low-gain regime) and, in this connection, the strong signal analysis of the Stanford experiment is carried out.
TL;DR: In this article, an explanation of laser-induced ripples in dielectric surfaces is given, taking into account the polarization charge which is induced on the boundaries of defects by the applied laser field.
Abstract: An explanation of laser-induced ripples in dielectric surfaces is given. The model takes into account the polarization charge which is induced on the boundaries of defects by the applied laser field. It is shown that this charge results in a sinusoidally varying perturbation to the applied laser field in the vicinity of the defect, and that the perturbation field has a period of \lambda/n , where λ is the laser wavelength and n is the index of the dielectric. It is further shown that this perturbation is greatest along the direction of laser polarization. At sufficiently high laser field intensities, the sum of the applied laser field and the maxima in the perturbation field will exceed the damage threshold, and a permanent ripple pattern in the surface will result. The predicted spacing and orientation of these ripples is in agreement with the experimentally observed data. Finally, it is shown how bootstrapping occurs to enhance the ripple pattern, once begun, and what roles propagation delays, defect size, and laser polarization state play in the process.
TL;DR: In this paper, a kinetics model for e-beam excited XeCl lasers using Ne/Xe/HCl gas mixtures is described, and the model has been validated by comparison with measured transient absorption in Ne /Xe mixtures, as well as by comparison of measured laser performance under a range of conditions.
Abstract: A kinetics model for e -beam excited XeCl lasers using Ne/Xe/HCl gas mixtures is described. The model has been validated by comparison with measured transient absorption in Ne/Xe mixtures, as well as by comparison with measured laser performance under a range of conditions. A key feature of the model is the inclusion of a fast three-body charge exchange process between Ne+ 2 and Xe which provides an efficient channel for XeCl* formation through ion-ion recombination. Xe+ 2 is predicted to be the dominant absorber in Ne/Xe mixtures with xenon fractions greater than 0.75 percent, while Cl- is predicted to be the major absorber in optimum laser mixtures.
TL;DR: In this paper, the main operating parameters of various free-electron lasers (FEL's) are discussed in a comparative way, providing a useful tool for laser design and a comparative evaluation of the various lasers.
Abstract: This paper discusses in a comparative way the main operating parameters of various free-electron lasers (FEL's), providing a useful tool for laser design and a comparative evaluation of the various lasers. We show that the various kinds of FEL's satisfy the same gain-dispersion relation and differ only in a single coupling parameter k . The different gain regimes which are common to all FEL's are delineated. We find the small signal gain in all the gain regimes (warm and cold beam, low- or high-gain, single electron, collective or strong coupling interaction). The laser gain parameter, radiation extraction efficiency, maximum power generation, and spectral width are given and compared in the various kinds of FEL's and gain regimes. The maximum power generation of all FEL's (except Compton-Raman scattering) is shown to be limited by an interaction region width parameter. This parameter and, consequently, the laser power are larger in the highly relativistic limit by a factor \sim \gamma_{0} in all bremsstrahlung FEL's, in comparison to Cerenkov-Smith-Purcell FEL's. Some expressions which were derived earlier for the magnetic bremsstrahlung FEL, like the expression for gain in the low-gain regime with the space charge effect correction and the low-gain expression for efficiency, are shown to be special cases of more general expressions.
TL;DR: In this article, a parameteric investigation of the damage threshold and morphology of nine frequently employed dielectric coatings as a function of pulse length (5 and 15 ns), frequency (1.06, 0.35, and 0.26 μm), and film thickness was performed.
Abstract: We report a parameteric investigation of the damage threshold and morphology of nine frequently employed dielectric coatings as a function of pulse length (5 and 15 ns), frequency (1.06, 0.53, 0.35, and 0.26 μm), and film thickness. A vidicon camera and computer were used to obtain real-time laser spatial profiles for each testing event. This technique greatly reduced the time required to obtain damage thresholds and enabled a large matrix of data to be obtained. The data and damage morphologies are discussed and several important conclusions are drawn concerning pulsed laser-induced damage to optical materials in thin-film form.
TL;DR: In this paper, the authors studied the performance of AlGaAs Fabry-Perot cavity type laser amplifiers for the exponential bandtail model with no k-selection rule.
Abstract: Signal gain, frequency bandwidth, and saturation output power, which are important parameters in determining preamplifier and linear repeater system performance, are studied theoretically and experimentally for AlGaAs Fabry-Perot cavity type laser amplifiers. Multimode rate equations with an input signal term are solved for the exponential bandtail model with no k -selection rule. Experimental results are in reasonable agreement with theoretical predictions. The maximum signal gain, frequency bandwidth, and the tolerance of the optical center frequency control are determined by facet mirror reflectivity and cavity length. The unsaturated signal gain increases with the pumping rate and the maximum signal gain as high as 21-28 dB is obtained near oscillation threshold for various cavity structures. The frequency bandwidth, at which signal gain is decreased by 3 dB from the low frequency value, is 1 GHz at 21 dB signal gain for a 900μm cavity length amplifier. The saturation output power, at which the signal gain is decreased by 3 dB from the unsaturated value, is -10 to -5 dBm. The saturation output power will be improved by 18 dB in a traveling wave type amplifier.