Showing papers in "Optics Letters in 1987"
TL;DR: It is demonstrated that a combination of prisms and diffraction gratings can provide not only quadratic but also cubic phase compensation of ultrashort optical pulses.
Abstract: We demonstrate that a combination of prisms and diffraction gratings can provide not only quadratic but also cubic phase compensation of ultrashort optical pulses We obtain compressed pulses as short as 6 fsec
976 citations
TL;DR: An optical evaluation technique is described that is suitable for determining the positions and magnitudes of reflection sites within miniature optical assemblies using the coherence effects exhibited by a broadband optical source and is referred to as optical coherence-domain reflectometry.
Abstract: An optical evaluation technique is described that is suitable for determining the positions and magnitudes of reflection sites within miniature optical assemblies. This method utilizes the coherence effects exhibited by a broadband optical source and is referred to as optical coherence-domain reflectometry. Background theory is given, and experimental results have demonstrated a resolution of 10 μm with an optical dynamic range of more than 100 dB.
800 citations
TL;DR: The use of a linearly chirped Bragg grating filter for dispersion cancellation in an optical-fiber link is discussed and calculations show that, with the proper taper function, the filter can have a high reflectivity and a quasi-constant nonzero dispersion, proportional to the inverse of the chirp.
Abstract: The use of a linearly chirped Bragg grating filter for dispersion cancellation in an optical-fiber link is discussed. Numerical and theoretical calculations are made, which show that, with the proper taper function, the filter can have a high reflectivity and a quasi-constant nonzero dispersion, proportional to the inverse of the chirp. The filter can compress dispersion-broadened pulses by factors of 2-5 or more, if many filters are cascaded. Its compactness and efficiency would make it suitable for on-line implementation.
531 citations
TL;DR: In this paper, a lambda = 1.53 microm signal with +22 dB gain was achieved at 295 K in an Er(3+)-doped single-mode fiber using a Lambda = 514.5 nm pump source.
Abstract: Traveling-wave amplification of a lambda = 1.53 microm signal with +22-dB gain is achieved at 295 K in an Er(3+)-doped single-mode fiber using a lambda = 514.5 nm pump source. The optimum fiber length for maximum gain is determined experimentally. A limit in signal-to-noise ratio that is due to concurrent amplification of spontaneous emission is observed. By cooling the fiber to 77 K, the amplifier gain is increased to +29 dB as a result of depopulation of the lower laser level.
531 citations
TL;DR: This method is used to stabilize laser frequencies and reduce linewidths by a factor of 1000 from 20 MHz to approximately 20 kHz.
Abstract: With simple optical geometries a separate resonant Fabry-Perot cavity can serve as an optical feedback element that forces a semiconductor laser automatically to lock its frequency optically to the cavity resonance. This method is used to stabilize laser frequencies and reduce linewidths by a factor of 1000 from 20 MHz to approximately 20 kHz.
515 citations
TL;DR: This experiment supports a mechanism for photoinducing an alternating second-order nonlinearity in the fiber by generating second-harmonic light from a single-mode fiber after a few minutes of seeding with 532-nm harmonic light along with 1.064-microm pump light.
Abstract: We generated second-harmonic light from a single-mode fiber after a few minutes of seeding with 532-nm harmonic light along with 1.064-μm pump light. This experiment supports a mechanism for photoinducing an alternating second-order nonlinearity in the fiber.
408 citations
TL;DR: It is shown that while linear birefringence will lead to a substantial splitting of the two polarizations over 20 km, this effect can be eliminated by use of the Kerr nonlinearity.
Abstract: The effect of birefringence on soliton propagation in single-mode optical fibers is considered. Emphasis is on solitons with multipicosecond widths that are appropriate for communications applications. It is shown that while linear birefringence will lead to a substantial splitting of the two polarizations over 20 km, this effect can be eliminated by use of the Kerr nonlinearity. Above a certain amplitude threshold, the central frequency of each polarization shifts just enough to lock the two polarizations together.
351 citations
TL;DR: A low-cost and simple technique for encryption of two-dimensional patterns and shapes based on the superposition of random grids is suggested and demonstrated.
Abstract: A low-cost and simple technique for encryption of two-dimensional patterns and shapes is suggested and demonstrated. The method is based on the superposition of random grids.
320 citations
TL;DR: A criterion for detector size to give true confocal operation is introduced and it is shown that the lateral resolution is considerably more sensitive to detector size than is the depth-discrimination or optical-sectioning property.
Abstract: We consider the role of the detector size in the imaging of confocal systems. We introduce a criterion for detector size to give true confocal operation and show that the lateral resolution is considerably more sensitive to detector size than is the depth-discrimination or optical-sectioning property.
276 citations
TL;DR: The four complex, almost degenerate, second-order eigenmodes of a two-mode fiber having a circular core are reduced to two nondegenerate, linearly polarized second-orders with stable-intensity lobe positions in a highly elliptical core fiber.
Abstract: The four complex, almost degenerate, second-order eigenmodes of a two-mode fiber having a circular core are reduced to two nondegenerate, linearly polarized second-order eigenmodes with stable-intensity lobe positions in a highly elliptical core fiber. Existing two-mode-fiber devices can be improved by this stabilization of the second-order modes. Practical sensors employing the two spatial modes as the two arms of an interferometer are described. The two arms of an interferometer of this type can have the same group delays, while the difference in phase delays is large.
273 citations
TL;DR: The operation of the double phase-conjugate mirror (DPCM), a photorefractive resonator with two facing DPCM's that can support spatial information in its oscillations, is demonstrated.
Abstract: We report on the operation of the double phase-conjugate mirror (DPCM). Two inputs to opposite sides of a photorefractive barium titanate crystal, which may carry different spatial images, are shown to pump the same four-wave mixing process mutually and are self-refracted without any external or internal crystal surface. This results in the phase-conjugate reproduction of the two images simultaneously. This device is analyzed theoretically, and applications in image processing, interferometry, and rotation sensing are discussed. We also demonstrate the operation of a ring laser, using the DPCM, as well as a photorefractive resonator with two facing DPCM’s that can support spatial information in its oscillations.
TL;DR: Pairs of soliton pulses are sent through a fiber, and the pulse separation at fiber input and output are compared, and close quantitative agreement with prediction is achieved, except when the pulses begin to merge.
Abstract: Pairs of soliton pulses are sent through a fiber, and the pulse separation at fiber input and output are compared. Both attractive and repulsive forces are observed. Close quantitative agreement with prediction is achieved, except when the pulses begin to merge. Then the attractive force becomes repulsive as the result of phase shifts triggered by the soliton self-frequency shift.
NEC1
TL;DR: A novel optical fiber is proposed that supports the lowest-order soliton despite the presence of optical loss and groupvelocity dispersion decreases with distance, in accord with soliton attenuation that is due to the inherent optical loss of the fiber.
Abstract: A novel optical fiber is proposed that supports the lowest-order soliton despite the presence of optical loss. Group-velocity dispersion of this fiber decreases with distance, in accord with soliton attenuation that is due to the inherent optical loss of the fiber.
TL;DR: It is shown that solitons emerge from initial pulses of arbitrary shape and amplitude whose central frequencies are at the zero-dispersion point, and are an attractive alternative to both the linear and the nonlinear communication schemes that have been proposed to date.
Abstract: It is shown that solitons emerge from initial pulses of arbitrary shape and amplitude whose central frequencies are at the zero-dispersion point. The initial threshold power is substantially reduced from that required for experiments to date. The use of these solitons is thus an attractive alternative to both the linear and the nonlinear communication schemes that have been proposed to date.
TL;DR: The behavior of single solitons is similar to that of continuous waves, and the nonlinear effects make the fast mode unstable when the beat length between the modes is long, but nondispersive pulses can still propagate.
Abstract: We examine the propagation of solitons in the two linearly polarized modes of a birefringent fiber. The behavior of single solitons is similar to that of continuous waves, and the nonlinear effects make the fast mode unstable when the beat length between the modes is long. Even with the instability, nondispersive pulses can still propagate. High-order solitons break up and can transfer most of the energy into a single, highly compressed soliton.
TL;DR: Gas sensing using evanescent waves of optical fibers is investigated and methane gas is detected by means of its strong optical absorption of the 3.392-microm line of a He-Ne laser.
Abstract: Gas sensing using evanescent waves of optical fibers is investigated. Methane gas is detected by means of its strong optical absorption of the 3.392-μm line of a He–Ne laser. A single fiber is used as both a sensor and an optical transmission line. The sensor has a small diameter, ranging from 1.8 to 7 μm, made by heating and expanding a part of a step-index silica fiber. An evanescent wave of 5 to 40% of the total propagating power is generated outside the fiber. When a sensor fiber of 1.8-μm diameter and 10-mm length is used, the minimum detectable concentration of methane is less than the lowest explosive limit of 5%.
TL;DR: In this paper, a simple model that concentrates on the phase change as a function of pulse walk-off was proposed to explain the spectral broadening of signal pulses during Raman or parametric optical pulse amplification.
Abstract: When pulse pairs copropagate in a fiber, each pulse chirps the other through cross-phase modulation (XPM). In particular, XPM causes spectral broadening of signal pulses during Raman or parametric optical pulse amplification. We have studied XPM experimentally in the fiber Raman amplification soliton laser. We show that experimentally observed spectra can be explained by a simple model that concentrates on the phase change as a function of pulse walk-off.
TL;DR: Numerical calculations of mean scattered intensities by simulation of one-dimensional perfectly conductive random rough surfaces using the Kirchhoff approximation can be used for assessing perturbative theories and for further experiments.
Abstract: Numerical calculations of mean scattered intensities by simulation of one-dimensional perfectly conductive random rough surfaces are presented Results relative to backscattering enhancement and more accurate criteria for the validity of the Kirchhoff approximation are obtained This method can also be used for assessing perturbative theories and for further experiments
TL;DR: For fibers with highly elliptical core geometries, which propagate only one lobe orientation of the second-order mode, the differential phase shift is also found to be polarization dependent.
Abstract: Longitudinal strains in optical fibers have been found to produce a large differential phase shift between the first-and second-order spatial modes propagating in a two-mode fiber. This differential phase shift between the modes is both calculated and measured to be dispersive with respect to wavelength. For fibers with highly elliptical core geometries, which propagate only one lobe orientation of the second-order mode, the differential phase shift is also found to be polarization dependent.
TL;DR: A digital phase-measuring interferometer with a laser-diode source has been developed that is based on a fringe-scanning technique with a stepwise wavelength change by variation of the laser injection current.
Abstract: A digital phase-measuring interferometer with a laser-diode source has been developed that is based on a fringe-scanning technique with a stepwise wavelength change by variation of the laser injection current. The phase is changed to produce a relative phase difference between the beams in the two arms of the interferometer. Calibrated phase shifts used for a phase-extraction algorithm are derived from one-dimensional least-squares fits to cosine fringe functions to achieve accurate results. Experimental results are presented.
TL;DR: Experiments were carried out in order to investigate efficient second-harmonic generation in phosphor-doped glass fibers with peak conversion efficiencies > 5% corresponding to peak powers> 1 kW at 0.53 microm.
Abstract: Experiments were carried out in order to investigate efficient second-harmonic generation in phosphor-doped glass fibers. Peak conversion efficiencies> 5% corresponding to peak powers> 1 kW at 0.53 μm have been obtained. By measuring the side light emitted and also by cutting the fibers, both the second-harmonic output power and the generation rate were studied along the fiber. Other measurements, including the polarization and mode structure of the frequency-doubled output, are also described.
TL;DR: A new method of instantaneously measuring three-dimensional velocity profiles and structure in air and oxygen using Raman excitation and laser-induced electronic fluorescence to generate a time-gated image of the moving oxygen molecules is reported.
Abstract: We report the development of a new method of instantaneously measuring three-dimensional velocity profiles and structure in air and oxygen. No seeding of particles, molecules, or atomic species is required. The method combines Raman excitation and laser-induced electronic fluorescence to generate a time-gated image of the moving oxygen molecules.
TL;DR: A three-laser, coherent anti-Stokes Raman scattering (CARS) technique for the simultaneous acquisition of spectra from two species has been developed, using a narrow-band, tunable dye-lasers as one of the CARS pump beams.
Abstract: A three-laser, coherent anti-Stokes Raman scattering (CARS) technique for the simultaneous acquisition of spectra from two species has been developed. A narrow-band, tunable dye-laser beam is used as one of the CARS pump beams. The frequency spacing between the spectra of the two species can be adjusted by changing the frequency of the dye-laser pump beam, enabling the spectra to be displayed at high resolution (0.5 cm(-1)) on the same intensified diode array detector.
TL;DR: In this article, exact dispersion relations for transverse magnetic polarized guided waves at an interface between either a linear dielectric or a metal and a nonlinear dielectrics were derived.
Abstract: We derive exact dispersion relations for transverse magnetic polarized guided waves at an interface between either a linear dielectric or a metal and a nonlinear dielectric. The nonlinearity is taken to be a Kerr-type nonlinearity. Numerical results are presented for the dielectric–metal case.
TL;DR: It was found that the odd-order higher dispersion [beta(3)] does not contribute to the modulation-instability frequency and the time derivative of the nonlinearity was included and shown to affect the instability.
Abstract: The modulation instability of an extended nonlinear Schrodinger equation was investigated. It was found that the odd-order higher dispersion [beta(3)] does not contribute to the modulation-instability frequency. The time derivative of the nonlinearity was included and shown to affect the instability. Finally, nonlinear retardation effects are shown to alter the results significantly.
TL;DR: The first observation to the authors' knowledge of optical bistability in CdS(x)Se(1-x)-doped glasses with rise and fall times of 25 psec for bistable switching is reported.
Abstract: We report the first observation to our knowledge of optical bistability in CdSxSe1−x-doped glasses with rise and fall times of 25 psec for bistable switching. The third-order nonlinear susceptibility χ(3) was estimated experimentally to be 1.3 × 10−9 esu, which is in good agreement with the value reported previously. The high-speed switching and value of χ(3) show that the bistability is caused by an optical nonlinearity that is attributed to the band-filling effect.
TL;DR: The mechanism of the soliton interaction is examined both analytically and numerically and it is shown that a bound 2-soliton splits into individual solitons traveling with different speeds because of higher-order effects.
Abstract: Interactions of solitons generated by pairs of optical pulses are studied using the perturbed nonlinear Schrodinger equation, which models nonlinear optical pulses in a monomode fiber. We examine the mechanism of the soliton interaction both analytically and numerically and show that a bound 2-soliton splits into individual solitons traveling with different speeds because of higher-order effects. The numerical results are in extremely close agreement with those obtained recently by Mitschke and Mollenauer in their experiments on 2-solitons in optical fibers [Opt. Lett. 12, 355 (1987)].
TL;DR: Room-temperature operation of a continuous-wave Tm-sensitized Ho:YAG laser at 2.0974 microm has been achieved under diode-laser pumping at 781.5 nm.
Abstract: Room-temperature operation of a continuous-wave Tm-sensitized Ho:YAG laser at 2.0974 microns has been achieved under diode-laser pumping at 781.5 nm. Observed thresholds are as low as 4.4 mW, with a slope efficiency of 19 percent with 0.5 percent output coupling.
TL;DR: It is shown that squeezed-state light is generated through forward four-wave mixing in sodium vapor as verified by homodyne detection and optical phase-sensitive noise with a minimum falling 4% below the shot-noise limit was observed.
Abstract: We have generated squeezed-state light through forward four-wave mixing in sodium vapor as verified by homodyne detection. Optical phase-sensitive noise with a minimum falling 4% below the shot-noise limit was observed.
TL;DR: The frequency stability of laser-diode-pumped, monolithic Nd:YAG solid-state unidirectional nonplanar ring oscillators was studied by heterodyne measurements and cw single-axial- and transverse-mode power was obtained.
Abstract: The frequency stability of laser-diode-pumped, monolithic Nd:YAG solid-state unidirectional nonplanar ring oscillators was studied by heterodyne measurements. CW single-axial- and transverse-mode power of 25 mW at 1064 nm was obtained at a slope efficiency of 19 percent. Two independent oscillators were offset-locked at 17 MHz with frequency fluctuations of less than + or - 40 kHz for periods of 8 min.