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Showing papers in "Optics Letters in 1991"


Journal ArticleDOI
TL;DR: Pulses having durations as short as 60 fsec have been directly generated by a self-mode-locked, dispersion-compensated Ti:sapphire laser and by using an extracavity fiber-prism pulse compressor.
Abstract: Pulses having durations as short as 60 fsec have been directly generated by a self-mode-locked, dispersion-compensated Ti:sapphire laser. By using an extracavity fiber-prism pulse compressor, pulse durations as short as 45 fsec have been obtained.

1,487 citations


Journal ArticleDOI
TL;DR: A large second-order nonlinearity is induced in the near-surface region of commercial fused-silica optical flats by a temperature and electric-field poling process and is extremely stable at room temperature and laboratory ambient.
Abstract: A large second-order nonlinearity [ χ(2)~1 pm/V~0.2 χ22(2) for LiNbO3] is induced in the near-surface (~4 μm) region of commercial fused-silica optical flats by a temperature (250–325°C) and electric-field (E ~ 5 × 104 V/cm) poling process. Once formed, the nonlinearity, which is roughly 103–104 times larger than that found in fiber second-harmonic experiments, is extremely stable at room temperature and laboratory ambient. The nonlinearity can be cycled by repeated depoling (temperature only) and repoling (temperature and electric field) processes without history effects. Possible mechanisms, including nonlinear moieties and electric-field-induced second-order nonlinearities, are discussed.

746 citations


Journal ArticleDOI
TL;DR: What is to the authors' knowledge the first high-density (>10(12) bits/cm(3)) optical recording of digital information in a multilayered, three-dimensional format is reported.
Abstract: What is to our knowledge the first high-density (>1012 bits/cm3) optical recording of digital information in a multilayered, three-dimensional format is reported. Information is written as submicrometer volume elements of increased refractive index in a photopolymer by two-photon excitation of a photoinitiator at the waist of a highly focused beam from a colliding-pulse mode-locked laser. Quadratic dependence of two-photon excitation on intensity confines polymerization to the focal volume. Information is read with sufficient axial resolution by differential interference contrast microscopy. This write-once, read-many technique should increase the capacity of the spinning disk format by 100-fold.

607 citations


Journal ArticleDOI
TL;DR: An approximate treatment that eliminates the McCumber theory's requirement of detailed electronic structure has been developed and found to usually provide more accurate values than an Einstein analysis.
Abstract: We have applied the theory of McCumber to the (4)4I(13/2) ? (4)I(15/2) transition of Er(3+) -doped glasses and confirmed its ability to provide both spectra and accurate values of cross sections. For an Al/P-silica fiber, the exact McCumber treatment is within 3% of the measured emission cross section, whereas an Einstein analysis is off by >50%. An approximate treatment that eliminates the McCumber theory's requirement of detailed electronic structure has been developed and found to usually provide more accurate values than an Einstein analysis.

565 citations


Journal ArticleDOI
TL;DR: It is demonstrated the operation of a quadrature phase-shifted extrinsic Fabry-Perot fiber-optic sensor for the detection of the amplitude and the relative polarity of dynamically varying strain.
Abstract: We demonstrate the operation of a quadrature phase-shifted extrinsic Fabry–Perot fiber-optic sensor for the detection of the amplitude and the relative polarity of dynamically varying strain. Two laterally displaced single-mode fibers inserted within a hollow silica tube form the 90° phase-shifted sensing system. A multimode fiber, placed in the tube facing the two fibers, acts as a reflector, thereby creating an air gap that acts as a Fabry–Perot cavity. A theoretical description of the sensor is given, and its operation as a dynamically varying strain sensor is described. Strain sensitivities of 5.54° phase shift/microstrain cm−1 are obtained.

483 citations


Journal ArticleDOI
TL;DR: An efficient room-temperature ytterbium-doped YAG laser operating at 1.03 microm pumped by an InGaAs strained-layer diode laser operating on 968 nm offers a number of advantages over AlGaAs pumped Nd:YAG lasers, including broader absorption features, longer fluorescent lifetime, and lower thermal loading of the gain medium.
Abstract: We have developed an efficient room-temperature ytterbium-doped YAG laser operating at 1.03 μm pumped by an InGaAs strained-layer diode laser operating at 968 nm. The threshold was 234 mW, and 23 mW of output power was obtained for an absorbed pump power of 345 mW. This laser offers a number of advantages over AlGaAs-pumped Nd:YAG lasers, such as broader absorption features, longer fluorescent lifetime, and lower thermal loading of the gain medium.

448 citations


Journal ArticleDOI
TL;DR: The present approach is robust and permits two-dimensional and three-dimensional electromagnetic pulse propagation directly from the full-vector Maxwell's equations.
Abstract: The initial results for femtosecond pulse propagation and scattering interactions for a Lorentz medium obtained by a direct time integration of Maxwell's equations are reported. The computational approach provides reflection coefficients accurate to better than 6 parts in 10,000 over the frequency range of dc to 3 x 10 to the 16th Hz for a single 0.2-fs Gaussian pulse incident upon a Lorentz-medium half-space. New results for Sommerfeld and Brillouin precursors are shown and compared with previous analyses. The present approach is robust and permits 2D and 3D electromagnetic pulse propagation directly from the full-vector Maxwell's equations.

440 citations


Journal ArticleDOI
TL;DR: An amplifying nonlinear-optical fiber loop mirror is used as the gain element in an all-fiber ring laser, and the resulting double-loop structure resembles a figure eight.
Abstract: An amplifying nonlinear-optical fiber loop mirror is used as the gain element in an all-fiber ring laser. The resulting double-loop structure resembles a figure eight. The output of the amplifying nonlinear-optical fiber loop mirror is fed back to the input through an optical isolator to ensure unidirectional operation. The laser produces 2-ps transform-limited pulses. The pulse energy corresponds to that of the fundamental soliton in the fiber used.

367 citations


Journal ArticleDOI
TL;DR: The Gordon-Haus limit of long-distance soliton transmission can be partially overcome through the use of linear filters in each amplifier stage, and new limits are derived and they show the possibility of increased bit rates and/or distances of propagation.
Abstract: The Gordon–Haus limit of long-distance soliton transmission can be partially overcome through the use of linear filters in each amplifier stage. New limits are derived, and they show the possibility of increased bit rates and/or distances of propagation.

357 citations


Journal ArticleDOI
TL;DR: An external cavity has been developed for use with commercial diode lasers that uses a diffraction grating at grazing incidence for wavelength selection and output coupling and is useful for high-resolution spectroscopy, laser cooling of atoms, time standards, and coherent optical communications.
Abstract: An external cavity has been developed for use with commercial diode lasers. It uses a diffraction grating at grazing incidence for wavelength selection and output coupling. This configuration allows a GaAlAs diode laser to be tuned conveniently anywhere in a range greater than 20 nm. Also, the linewidth is reduced by a factor of more than 1000 from 40 MHz to less than 10 kHz. The new laser system should be useful for high-resolution spectroscopy, laser cooling of atoms, time standards, and coherent optical communications.

343 citations


Journal ArticleDOI
TL;DR: Cross-phase and self-phase modulation are used for self-sustained mode locking of a high-power neodymium glass fiber laser.
Abstract: Cross-phase and self-phase modulation are used for self-sustained mode locking of a high-power neodymium glass fiber laser. Stable pulses with a FWHM as short as 70 fs and pulse energies of as much as 1 nJ are generated at a wavelength of 1.064 microm.

Journal ArticleDOI
TL;DR: It is shown how fast-Fourier-transform methods can be used to accelerate computations of scattering and absorption by particles of arbitrary shape using the discrete-dipole approximation.
Abstract: We show how fast-Fourier-transform methods can be used to accelerate computations of scattering and absorption by particles of arbitrary shape using the discrete-dipole approximation.

Journal ArticleDOI
TL;DR: A stimulated Brillouin fiber ring laser with a spectral width of 2 kHz and an intrinsic linewidth of less than 30 Hz has been demonstrated, and applications of such a laser include laser linewsidth narrowing, microwave frequency generation, high-rate amplitude modulation, and optical inertial rotation sensing.
Abstract: A stimulated Brillouin fiber ring laser with a spectral width of 2 kHz and an intrinsic linewidth of less than 30 Hz has been demonstrated. Applications of such a laser include laser linewidth narrowing, microwave frequency generation, high-rate amplitude modulation, and optical inertial rotation sensing.

Journal ArticleDOI
TL;DR: A new boundary condition algorithm is presented that passes outgoing radiation freely with a minimum reflection coefficient (typically 10(-5)) while inhibiting the flux of incoming radiation.
Abstract: A new boundary condition algorithm is presented that passes outgoing radiation freely with a minimum reflection coefficient (typically 10−5) while inhibiting the flux of incoming radiation. In contrast to the commonly used absorber method, this algorithm contains no adjustable parameters and is thus problem independent. It adapts naturally to a standard Crank–Nicholson difference scheme and is shown to be accurate and robust for both two-and three-dimensional problems.

Journal ArticleDOI
TL;DR: A novel micromanipulation technique is proposed for aligning fine particles on micrometer-scale spatial patterns and for moving the particles continuously along the formed patterns.
Abstract: A novel micromanipulation technique is proposed for aligning fine particles on micrometer-scale spatial patterns and for moving the particles continuously along the formed patterns. This technique is based on the repetitive scanning of a focused trapping laser beam. The velocity of the particle flow can be controlled by scan speed and laser power. The origin of the driving force is considered theoretically and experimentally.

Journal ArticleDOI
TL;DR: The ABCD propagation law is generalized for an optical system by introducing a generalized complex radius of curvature Q for a general optical beam.
Abstract: We have generalized the ABCD propagation law, Q(2) = (AQ(1) + B)/(CQ(1) + D), for an optical system by introducing a generalized complex radius of curvature Q for a general optical beam. The real part of 1/Q is related to the mean radius of curvature of the wave front, while the imaginary part is related to the second moment of the amplitude of the beam.

Journal ArticleDOI
TL;DR: An eye-safe pulsed coherent laser radar has been developed by using single-frequency Tm,Ho:YAG lasers and heterodyne detection.
Abstract: An eye-safe pulsed coherent laser radar has been developed by using single-frequency Tm,Ho:YAG lasers and heterodyne detection. Returns from a mountainside located 145 km from the laser radar system and the measurement of wind velocity to ranges exceeding 20 km have been demonstrated with transmitted pulse energies of 22 mJ.

Journal ArticleDOI
TL;DR: It is shown analytically that the evolution equation can be reduced to the nonlinear Schrödinger equation if the variation length is much shorter than the soliton period.
Abstract: The effects of randomly varying birefringence on solitons are studied. It is shown analytically that the evolution equation can be reduced to the nonlinear Schrodinger equation if the variation length is much shorter than the soliton period. The soliton does not split at high values of the average birefringence, but it does undergo spreading and loss of polarization. A soliton with a temporally constant initial state of polarization is still largely polarized after 40z0 if the normalized birefringence is δ ≤ 1.3.

Journal ArticleDOI
TL;DR: Filters that have optimal trade-offs among the criteria of noise robustness, sharpness of the correlation peak, and Horner efficiency are presented, and an explicit mathematical expression is provided.
Abstract: Filters that have optimal trade-offs among the criteria of noise robustness, sharpness of the correlation peak, and Horner efficiency are presented, and an explicit mathematical expression is provided. Owing to their optimality, these filters provide a figure of merit and then permit a rigorous characterization of filter performances for optical pattern recognition.

Journal ArticleDOI
TL;DR: This work proposes what is to their knowledge the first use of a Pr(3+)-doped fluoride fiber amplifier as a practical amplifier operating at the 1.3-microm band, based on a demonstration of signal amplification and a spectroscopic investigation.
Abstract: We propose what is to our knowledge the first use of a Pr3+-doped fluoride fiber amplifier as a practical amplifier operating at the 1.3-μm band, based on a demonstration of signal amplification and a spectroscopic investigation. The feasibility of the fluoride fiber amplifier is confirmed.

Journal ArticleDOI
TL;DR: High-resolution, uniformly diffracting volume holograms in a single Fe-doped LiNbO(3) crystal are recorded by angularly multiplexing a plane-wave reference beam to compute exposure schedules.
Abstract: We have recorded (at room temperature) as many as 500 high-resolution, uniformly diffracting volume holograms in a single Fe-doped LiNbO3 crystal. The holograms were stored by angularly multiplexing a plane-wave reference beam. The graphical procedure that we used to compute exposure schedules is described. Experimental results are also presented.

Journal ArticleDOI
TL;DR: A direct measurement of the amplitude and the phase of a femtosecond light pulse is performed for the first time to the authors' knowledge, and the time dependence of the field can be easily obtained by a Fourier transform.
Abstract: A direct measurement of the amplitude and the phase of a femtosecond light pulse is performed for the first time to our knowledge The measurement is made in the frequency domain, and the time dependence of the field can be easily obtained by a Fourier transform The technique relies on a pulse synthesis scheme to unravel the frequency dependence of the phase A mask filters the spectrum, which gives rise to a pulse with a measurable temporal profile related to the frequency dependence of the phase In particular, with a rectangular slit the time delay of the synthesized pulse is the first derivative of the phase with respect to the frequency of the original pulse at the central frequency of the filter The amplitude of the spectrum is obtained from the power spectrum

Journal ArticleDOI
TL;DR: A novel aspheric holographic optical element, the holographic axilens, is reported for achieving extended focal depth while keeping high lateral resolution.
Abstract: We report a novel aspheric holographic optical element, the holographic axilens, for achieving extended focal depth while keeping high lateral resolution. The element is designed according to special optimization techniques and recorded as a computer-generated hologram. The results for a specific element, which has a depth of focus of 30 mm, a lateral resolution of 80 microm, a focal length of 1250 mm, and a diameter of 12.5 mm at a wavelength of 633 nm, are presented.

Journal ArticleDOI
TL;DR: The mode spectrum of a 3.8-cm-diameter fused-silica sphere has been studied in the vicinity of 1.06 microm and is in excellent agreement with predictions from Mie theory.
Abstract: The mode spectrum of a 3.8-cm-diameter fused-silica sphere has been studied in the vicinity of 1.06 μm. A single-frequency Nd:YAG laser was used to excite whispering gallery modes by means of evanescent wave coupling. The spectrum is in excellent agreement with predictions from Mie theory.

Journal ArticleDOI
TL;DR: The microchip laser can be tuned over 107 GHz, without mode hopping, by heating the laser crystal with a single-mode-oscillation output power of ~103 mW in 1.1-at.%-doped Nd:YVO(4).
Abstract: Single-mode-oscillation output power of ~103 mW has been observed in 1.1-at.%-doped Nd:YVO(4) pumped with a 500-mW laser diode. Continuous-wave thresholds of ~5.3 mW have been observed with slope efficiencies of greater than 32.4%. The microchip laser can be tuned over 107 GHz, without mode hopping, by heating the laser crystal.

Journal ArticleDOI
TL;DR: It is shown that an external coupled cavity containing a nonlinear quantum-well reflector can continuously selfstart a dispersion-compensated Ti:sapphire laser, which produces stable time-transform-limited pulses as short as 70 fs in a TEM(00) mode.
Abstract: We show that an external coupled cavity containing a nonlinear quantum-well reflector can continuously self-start a dispersion-compensated Ti:sapphire laser, which produces stable time-transform-limited pulses as short as 70 fs in a TEM00 mode. In this mode of operation, the quantum wells do not control the mode-locking process, as in previous research on the resonant passive mode-locked laser. By separating the mode-locking and starting processes, we show that the presence of higher-order spatial modes is not required to start or sustain mode locking.

Journal ArticleDOI
TL;DR: A grating with variable duty cycle behaves like a material with distributed index and distributed-index elements are proposed and the physical principle is demonstrated with water waves.
Abstract: Zero-order gratings are grating structures with a period that is small compared with the wavelength of light. Only the directly transmitted or reflected light, the zero diffraction order, is nonevanescent and propagates in a distance from the grating. Thus the grating behaves like a slab of ordinary homogeneous material with an effective refractive index. By varying the material composition, i.e., by variation of the duty cycle of the grating, the effective refractive index can be changed. A grating with variable duty cycle therefore behaves like a material with distributed index. Based on such artificial materials, distributed-index elements are proposed. The physical principle is demonstrated with water waves.

Journal ArticleDOI
TL;DR: It is shown that thedegree of indistinguishability equals the degree of coherence, which provides the fundamental link between the wave and the particle descriptions.
Abstract: It has long been known that the interference produced by two light beams is related both to their mutual coherence and also to the intrinsic indistinguishability of the photon paths. With the help of a decomposition of the density operator it is shown that the degree of indistinguishability equals the degree of coherence. This provides the fundamental link between the wave and the particle descriptions.

Journal ArticleDOI
TL;DR: This technique makes possible the generation of clean, high-intensity subpicosecond laser pulses even in the presence of high levels of amplified spontaneous emission from the laser system.
Abstract: We demonstrate the technique of self-induced plasma shuttering as a means of suppressing prepulse energy that accompanies high-energy, ultrashort laser pulses. This technique makes possible the generation of clean, high-intensity subpicosecond laser pulses even in the presence of high levels of amplified spontaneous emission from the laser system. Low prepulse energy is important in applications such as the generation of solid-density subpicosecond plasmas.

Journal ArticleDOI
TL;DR: An ABCD matrix model is presented showing that self-focusing in the laser rod leads to modifications of the Gaussian beam parameters in cw-pumped Ti:Al(2)O(3) lasers, and stabilization of self-mode-locking should result from these beam perturbations.
Abstract: We present an ABCD matrix model showing that self-focusing in the laser rod leads to modifications of the Gaussian beam parameters in cw-pumped Ti:Al2O3 lasers. Stabilization of self-mode-locking should result from these beam perturbations. Experimental measurements of beam modifications supporting this model are presented. The role of gain guiding is studied, and the limitations of the model are discussed.