Showing papers in "Optics Letters in 1990"
TL;DR: The question of phase detection in photonic communications systems that use linear optical amplifiers is considered, owing to the nonlinear Kerr effect in the transmission fiber, which limits the capacity and range of such systems to a range of a few thousand kilometers.
Abstract: Spontaneous emission noise limits the capacity and range of photonic communications systems that use linear optical amplifiers. We consider here the question of phase detection in such systems. Amplitude-to-phase-noise conversion occurs owing to the nonlinear Kerr effect in the transmission fiber, resulting in optimal phase noise performance when the nonlinear phase shift of the system is approximately 1 rad. Error-free state-of-the-art systems that use phase detection at multigigabit rates are thereby limited to a range of a few thousand kilometers.
679 citations
TL;DR: Under the combined effect of diffraction, anomalous dispersion, and nonlinear refraction, an optical pulse can collapse simultaneously in time and space as discussed by the authors, and such a collapse could yield short pulses with extremely large optical fields.
Abstract: Under the combined effect of diffraction, anomalous dispersion, and nonlinear refraction, an optical pulse can collapse simultaneously in time and space. Such a collapse could yield short pulses with extremely large optical fields. Light bullets—pulses that propagate without change in space or time—are also possible. The condition for such a collapse and possible experiments are discussed.
618 citations
TL;DR: A method is presented that permits the determination of atmospheric aerosol extinction profiles from measured Raman lidar signals, no critical input parameters are needed, which could cause large uncertainties of the solution.
Abstract: A method is presented that permits the determination of atmospheric aerosol extinction profiles from measured Raman lidar signals. No critical input parameters are needed, which could cause large uncertainties of the solution, as is the case in the Klett method for the inversion of elastic lidar returns.
496 citations
TL;DR: A novel device arrangement for all-optical switching that permits efficient exploitation of waveguide nonlinearities is discussed, based on a long optical fiber loop mirror with an integral short asymmetrically located optical amplifier.
Abstract: A novel device arrangement for all-optical switching that permits efficient exploitation of waveguide nonlinearities is discussed. It is based on a long optical fiber loop mirror with an integral short asymmetrically located optical amplifier. The device performance is demonstrated by using a Nd3+-doped fiber amplifier. Switching is obtained for peak signal powers of less than 1 W and an amplifier pump power of 10 mW.
454 citations
TL;DR: Temperature distribution in silica single-mode optical fibers, from -30 to +60 degrees C, is successfully measured by using Brillouin optical-fiber time-domain analysis.
Abstract: Temperature distribution in silica single-mode optical fibers, from -30 to +60 degrees C, is successfully measured by using Brillouin optical-fiber time-domain analysis. A temperature measurement accuracy of 3 degrees C with a spatial resolution of 100 m is attained over a fiber length of 1.2 km.
435 citations
TL;DR: The observation of spatial optical solitons due to the Kerr nonlinearity in a planar glass waveguide and measurements of the nonlinear response obtained by placing a pinhole at the output of the waveguide are reported.
Abstract: We report the observation of spatial optical solitons due to the Kerr nonlinearity in a planar glass waveguide and present measurements of the nonlinear response obtained by placing a pinhole at the output of the waveguide. For input intensities greater than that required for the fundamental soliton, we observe breakup of the output owing to the effect of two-photon absorption.
383 citations
TL;DR: This work reports programmable shaping of femtosecond optical pulses by use of a multielement liquid-crystal modulator to manipulate the phases of spatially dispersed optical frequency components.
Abstract: We report programmable shaping of femtosecond optical pulses by use of a multielement liquid-crystal modulator to manipulate the phases of spatially dispersed optical frequency components. Our approach provides for continuously variable control of the optical phase and permits the pulse shape to be reconfigured on a millisecond time scale. We use the apparatus to demonstrate femtosecond pulse-position modulation as well as programmable compression of chirped femtosecond pulses.
378 citations
TL;DR: It is proposed by which the quantum states of two light beams of different frequencies can be interchanged and it is possible to generate frequency-tunable squeezed light for spectroscopic applications.
Abstract: An experimental scheme is proposed by which the quantum states of two light beams of different frequencies can be interchanged. With this scheme it is possible to generate frequency-tunable squeezed light for spectroscopic applications.
342 citations
TL;DR: The guidingcenter soliton is shown to satisfy the nonlinear Schrodinger equation with a correction of order (z(a)/z(0))(2) with distortionless propagation of the guiding-center solitons.
Abstract: For a relatively long optical pulse in a fiber with a dispersion distance z(0) much larger than the loss distance, a soliton cannot exist in an ideal sense. However, with a proper choice of the initial amplitude and amplifier distance z(a), a nonlinear pulse (a guiding-center soliton) propagates like a soliton over a distance much larger than the dispersion distance when it is periodically amplified at distances much shorter than the dispersion distance. The guidingcenter soliton is shown to satisfy the nonlinear Schrodinger equation with a correction of order (z(a)/z(0))(2). Numerical examples supported by analytical results are presented for distortionless propagation of the guiding-center solitons with a pulse width of 40 psec in a dispersion-shifted fiber of D = 1 psec/(nm-km).
314 citations
TL;DR: Zinc doping is shown to reduce the photorefraction in LiNbO(3):Zn, and the optical and nonlinear-optical data are similar to those of LiNnbO (3):Mg, but the former shows better optical performance.
Abstract: Zinc doping is shown to reduce the photorefraction in LiNbO3:Zn. The damage-resistant crystal LiNbO3:Zn has demonstrated a conversion efficiency of approximately 50% for frequency doubling of 1.06-μm radiation. The dependence of optical characteristics on the ZnO concentration in the melt reveals a sharp change of the optical properties at the threshold concentration of 4–6 mol % Zn. The optical and nonlinear-optical data of LiNbO3:Zn are similar to those of LiNbO3:Mg, but the former shows better optical performance.
303 citations
TL;DR: Broadly tunable cw laser emission is reported in Tm:YAG and TM:YSGG at room temperature with Ti:sapphire laser pumping with smooth tuning results from overlapping transitions between phonon-broadened crystal field Stark levels.
Abstract: Broadly tunable cw laser emission is reported in Tm:YAG and Tm:YSGG at room temperature with Ti:sapphire laser pumping. The Tm3+3F4 → 3H6 transition is tuned continuously over the ranges 1.87–2.16 μm in YAG and 1.85–2.14 μm in YSGG. Smooth tuning results from overlapping transitions between phonon-broadened crystal field Stark levels.
TL;DR: A time-gated technique to improve the possibility of localizing spatial differences in absorption when transilluminating a turbid, highly scattering medium, such as human tissue, is demonstrated.
Abstract: A time-gated technique to improve the possibility of localizing spatial differences in absorption when transilluminating a turbid, highly scattering medium, such as human tissue, is demonstrated. When transmitting picosecond laser pulses and detecting photons on the opposite side of the object, the contrast can be strongly enhanced by detecting only the photons with the shortest traveling time. Measurements on a 35-mm-thick tissue phantom with 5-mm-diameter absorbing objects inside are reported with data for a human hand in vivo. Implications for optical mammography (diaphanography) are discussed.
TL;DR: Photoinduced guided index changes approaching 10−4 in the range 488–784 nm, measured using a simple interferometric technique, are reported in germanosilicate single-mode optical fibers exposed to the 488-nm line of an Ar+ laser running multifrequency.
Abstract: Photoinduced guided index changes approaching 10−4 in the range 488–784 nm, measured using a simple interferometric technique, are reported in germanosilicate single-mode optical fibers exposed to the 488-nm line of an Ar+ laser running multifrequency. The wavelength dependence and dynamics of the writing process are characterized, and the material dispersion of the induced Δn(λ) is shown to be weak. The effect is placed in the context of related research on color centers in these fibers, and two different mechanisms are proposed that lead to quantitative estimates in rough agreement with the measured Δn values.
TL;DR: The codoping of a heavy-metal fluoride glass by two rare-earth ions, erbium and ytterbium, permits the semiconductor laser infrared excitation of two visible neighboring fluorescence lines of erbia by upconversion, the intensity ratio of which is a single variable function of temperature.
Abstract: The codoping of a heavy-metal fluoride glass by two rare-earth ions, erbium and ytterbium, permits the semiconductor laser infrared excitation of two visible neighboring fluorescence lines of erbium by upconversion, the intensity ratio of which is a single variable function of temperature.
TL;DR: A method of constructing optimal multicriteria filters for optical pattern recognition by illustrated for double-optimization criteria, and filters that are not overspecialized are obtained, in contrast with traditional techniques.
Abstract: A method of constructing optimal multicriteria filters for optical pattern recognition is presented. In the particular case of synthetic discriminant function filters, this method is illustrated for double-optimization criteria, and filters that are not overspecialized are obtained, in contrast with traditional techniques. Furthermore, a rigorous comparison between different filters, with respect to the considered criteria, is provided with this approach.
TL;DR: A new method and apparatus for measuring the group delay in optical components and laser cavities are described, using a Michelson interferometer for cross-correlational fringes.
Abstract: A new method and apparatus for measuring the group delay in optical components and laser cavities are described. Cross-correlational fringes are fully recorded with a Michelson interferometer, in one of whose arms the optics to be measured are inserted. The path difference of the interferometer is calibrated to subwavelength accuracy, and the group delay is calculated from the phase of the Fourier transform of the measured fringe. The group delay for the entire visible-wavelength region is evaluated after a single measurement in approximately 10 min, using white light.
TL;DR: Angle- and time-resolved studies are presented for an ultrafast laser pulse propagating through a slab of random media in the intermediate scattering regime, where a coherent (ballistic) component coexists with a incoherent (diffusive) component in the forward-scattered light.
Abstract: Angle- and time-resolved studies are presented for an ultrafast laser pulse propagating through a slab of random media in the intermediate scattering regime, where a coherent (ballistic) component coexists with a incoherent (diffusive) component in the forward-scattered light. The incoherent component can be approximated by diffusion theory when the thickness of the slab is greater than 10 transport mean free paths. The theoretical results from the two-frequency coherence function in the Rytov approximation are in qualitative but not quantitative agreement with the experimental results.
TL;DR: A more exact model is suggested for the description of nonlinear light propagation in fibers that takes into account the Stokes losses associated with the material excitation, the dependence of non linear effects on the light frequency, and the frequency dependence of the fiber mode area.
Abstract: A more exact model is suggested for the description of nonlinear light propagation in fibers. In addition to the previously discussed self-phase modulation, parametric, dispersion, self-steepening, and Raman self-scattering effects, this model also takes into account the Stokes losses associated with the material excitation, the dependence of nonlinear effects on the light frequency, and the frequency dependence of the fiber mode area. The self-steepening effect is taken into account more correctly in comparison with previous models. The effects influence considerably the femtosecond soliton propagation. The model is generalized for the case of various fiber dispersion properties along the fiber length. The possibility of obtaining high-quality pulses of less than 15-fsec duration by compression of fundamental solitons with approximately 100-fsec duration in fibers with slowly decreasing dispersion is shown.
TL;DR: The feasibility of an optical-frequency-to-radio-frequency division method that is based on visible or near-infrared laser oscillators only is explored and the arithmetic average of two visible frequencies is generated.
Abstract: We explore and demonstrate the feasibility of an optical-frequency-to-radio-frequency division method that is based on visible or near-infrared laser oscillators only. Comparing harmonic and sum frequencies, we generate the arithmetic average of two visible frequencies. Cascading n stages provides difference-frequency division by 2(n). For a demonstration we have phase locked the second harmonic and the sum frequency of two independent diode lasers.
TL;DR: A phase plate based on the fractional-Talbot effect is described that converts a single expanded laser beam into a regular array of uniformly illuminated apertures with virtually 100% efficiency.
Abstract: We describe a phase plate based on the fractional-Talbot effect that converts a single expanded laser beam into a regular array of uniformly illuminated apertures with virtually 100% efficiency. The size, spacing, and fill factor of the illuminated aperture grid can be freely chosen to interface with a variety of electro-optic devices. A binary-optics phase plate is demonstrated that converts uniform illumination into an array of square illumination cells with a fill factor of 1/16.
TL;DR: The properties and construction of a polarization-independent Fresnel lens array using nematic liquid crystals in which the diffraction efficiency of lenses can be electrically controlled is described.
Abstract: In successive zones of a layer of nematic liquid crystal material, the principal axes of at least some of the material in each zone are established orthogonal to the axes of at least some of the material in adjacent zones. By applying a uniform electric field to the zones of the entire layer, an electrically controlled polarization-independent Fresnel lens is achieved.
TL;DR: The experimental results show that the nonlinear loop mirror performs as an optical modulator that consists of all-fiber components that includes a high-power signal at one wavelength and a low- power signal at another wavelength.
Abstract: We describe the two-wavelength operation of the nonlinear fiber loop mirror. In this mode of operation a high-power signal at one wavelength switches a low-power signal at another wavelength. This device is investigated both theoretically and experimentally. The experimental results show that the nonlinear loop mirror performs as an optical modulator that consists of all-fiber components.
TL;DR: Speculative reflection for laser-cooled atoms dropped onto a gradient-light-force mirror is demonstrated and transit times are observed for atoms dropped from a height of ~2.0 cm and bouncing twice on the evanescent wave before being detected.
Abstract: We demonstrate specular reflection for laser-cooled atoms dropped onto a gradient-light-force mirror. Transit times of 264 msec are observed for atoms dropped from a height of ~2.0 cm and bouncing twice on the evanescent wave before being detected. Of the ~107 atoms initially dropped, ~3 × 103 are detected after 264 msec.
TL;DR: A simple linear filtering technique for transforming individual femTosecond light pulses into terahertzrepetition-rate bursts of femtosecond pulses achieves high efficiency and pulse repetition rates approaching 6 THz.
Abstract: We describe a simple linear filtering technique for transforming individual femtosecond light pulses into terahertzrepetition-rate bursts of femtosecond pulses. By using phase-only filtering, high efficiency is achieved. Pulse repetition rates approaching 6 THz are obtained.
TL;DR: An argon-ion-laser-pumped erbium-doped fiber laser at 1.55 microm that incorporates low-rate frequency modulation of an intracavity acousto-optic modulator to provide repeated, continuous tuning of the output spectrum is described.
Abstract: We describe an argon-ion-laser-pumped erbium-doped fiber laser at 1.55 microm that incorporates low-rate frequency modulation of an intracavity acousto-optic modulator to provide repeated, continuous tuning of the output spectrum. The spectral width of this wavelength-swept fiber laser is as large as 20 nm with 9 mW of output power, even though erbium in silica has a mostly homogeneously broadened gain. The time-averaged visibility curve for a 14-nm-wide source indicates a short (160-microm) coherence length, which is of interest for fiber-optic gyroscopes that operate with long integration times and short-coherence-length sources.
TL;DR: Spectroscopic measurements of fluorescence and absorption in an erbium-doped fiber permit the evaluation of the Stark-level energies of the (4I(15/2) and (4)I(13/ 2) manifolds in Er:glass.
Abstract: Spectroscopic measurements of fluorescence and absorption in an erbium-doped fiber permit the evaluation of the Stark-level energies of the (4)I(15/2) and (4)I(13/2) manifolds in Er:glass. The data permit the allocation of the individual laser transitions associated with the room-temperature gain spectrum of erbium-doped fiber amplifiers operating near lambda = 1.53 microm.
TL;DR: In this article, a 75-km recirculating loop of dispersion-shifted fiber (D = 1.38 psec/nm/km at λs), using low-gain erbium amplifiers spaced 25 km apart, displays jitter in pulse arrival times consistent with low error rates for transmission over 9000 km and for bit rates ≲4 Gbits/sec.
Abstract: Transmission of 50-psec solitons in a 75-km recirculating loop of dispersion-shifted fiber (D = 1.38 psec/nm/km at λs), using low-gain erbium amplifiers spaced 25 km apart, displays jitter in pulse arrival times consistent with low error rates for transmission over 9000 km and for bit rates ≲4 Gbits/sec. Furthermore, a study of soliton pair propagation in the same loop shows no significant interaction over 9000 km for pair spacings ≥5τ.
TL;DR: The first measurements of the phase of the infrared-visible sum-frequency generation signal are presented, and two techniques are introduced and applied to the determination of the polar orientation of a selected group of atoms within an adsorbed molecule.
Abstract: We present what are to our knowledge the first measurements of the phase of the infrared-visible sum-frequency generation signal. We introduce two techniques and apply the measurements to the determination of the polar orientation of a selected group of atoms within an adsorbed molecule.
TL;DR: A diode-pumped Nd:YAG laser is passively Q switched by using F(2)(-) color centers in lithium fluoride as a saturable absorber to produce pulses of 20-30-nsec duration at 1064 nm.
Abstract: A diode-pumped Nd:YAG laser is passively Q switched by using F(2)(-) color centers in lithium fluoride as a saturable absorber. When cw pumped with a laser diode, the laser produces pulses of 20-30-nsec duration at 1064 nm, with an energy of as much as 20 microJ and a peak power of more than 1 kW. Data are presented on pulse width, energy, and repetition rate as a function of pump power. When the laser is operated at high pulse energy levels, a gradual bleaching of the saturable absorber is observed.
TL;DR: Experimental results for sech(2) intensity input profiles are in good agreement with the theoretical predictions, and input pulses with substantial background radiation emerge both compressed and pedestal free.
Abstract: We study the shaping of picosecond-duration optical pulses by the intensity-dependent transmission characteristics of a fiber loop mirror in the normally dispersive region. Experimental results for sech2 intensity input profiles are in good agreement with the theoretical predictions. In addition, input pulses with substantial background radiation emerge both compressed and pedestal free.