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Showing papers in "Optics Letters in 1993"


Journal ArticleDOI
TL;DR: These images represent the highest depth resolution in vivo retinal images to date and are to the authors' knowledge the first in vivo measurements of human retinal structure with optical coherence tomography.
Abstract: We describe what are to our knowledge the first in vivo measurements of human retinal structure with optical coherence tomography. These images represent the highest depth resolution in vivo retinal images to date. The tomographic system, image-processing techniques, and examples of high-resolution tomographs and their clinical relevance are discussed.

1,049 citations


Journal ArticleDOI
TL;DR: By incorporating a section of large positive-dispersion fiber in an all-fiber erbium ring laser, a fully self-starting source of 77-fs pulse with 90 pJ of energy and greater than 1 kW of peak power at a 45-MHz repetition rate is obtained.
Abstract: By incorporating a section of large positive-dispersion fiber in an all-fiber erbium ring laser, we obtain high-energy pulses with spectral widths of 56 nm. The chirp on these pulses is highly linear and can be compensated for with dispersion in the output coupling fiber lead. The result is a fully self-starting source of 77-fs pulse with 90 pJ of energy and greater than 1 kW of peak power at a 45-MHz repetition rate.

912 citations


Journal ArticleDOI
TL;DR: The use of a fiber Fabry–Perot filter for detecting the wavelength shift of a Fiber Bragg grating sensor or network of sensor elements along a common fiber path is described.
Abstract: The use of a fiber Fabry–Perot filter for detecting the wavelength shift of a fiber Bragg grating sensor or network of sensor elements along a commonfiber path is described. Results obtained by using a system with four sensor elements are presented.

798 citations


Journal ArticleDOI
Fai H. Mok1
TL;DR: As many as 5000 holograms of high-resolution images have been stored within a single crystal of Fe:LiNbO3 using fracture-space multiplexing to increase the storage bandwidth.
Abstract: As many as 5000 holograms of high-resolution images (320 × 220 pixels) have been stored within a single crystal of Fe:LiNbO3. The nominal angle between the reference beam and the object beam was 90°. Fractal-space multiplexing was used to increase the storage bandwidth.

548 citations


Journal ArticleDOI
TL;DR: In this article, the frequency-resolved optical gating (FOSG) technique was introduced for measuring the intensity and phase of an arbitrary ultrashort pulse using an instantaneous nonlinear-optical interaction of two variably delayed replicas.
Abstract: We introduce a new technique, frequency-resolved optical gating, for measuring the intensity I(t) and the phase ϕ(t) of an individual arbitrary ultrashort pulse. Using an instantaneous nonlinear-optical interaction of two variably delayed replicas of the pulse, frequency-resolved optical gating involves measuring the spectrum of the signal pulse versus relative delay. The resulting trace, a spectrogram, yields an intuitive full-information display of the pulse. Inversion of this trace to obtain the pulse intensity and phase is equivalent to the well-known two-dimensional phase-retrieval problem and thus yields essentially unambiguous results for I(t) and ϕ(t).

484 citations


Journal ArticleDOI
TL;DR: By optimizing the intracavity dispersion compensation in a self-mode-locked Ti:sapphire laser, pulses of 10.95-fs duration are generated, which are shorter than has been possible with any other type of laser material to date.
Abstract: By optimizing the intracavity dispersion compensation in a self-mode-locked Ti:sapphire laser, we have generated pulses of 10.95-fs duration. Dispersion within the laser cavity is reduced by use of a short 4.5-mm highly doped Ti:sapphire crystal and fused-silica prisms. The output from the laser has an average power of as much as 500 mW, with a wavelength centered at 780 nm and a bandwidth of 62 nm. Our results demonstrate that the exceptionally broad bandwidth of Ti:sapphire can be utilized to generate pulses that, to our knowledge, are shorter than has been possible with any other type of laser material to date.

403 citations


Journal ArticleDOI
A. Constable1, Jinha Kim1, J. Mervis1, F. Zarinetchi1, Mara Prentiss1 
TL;DR: A fiber-optical version of a stable three-dimensional light-force trap is demonstrated, which has been used to hold and manipulate small dielectric spheres and living yeast.
Abstract: We demonstrate a fiber-optical version of a stable three-dimensional light-force trap, which we have used to hold and manipulate small dielectric spheres and living yeast. We show that the trap can be constructed by use of infrared diode lasers with fiber pigtails, without any external optics.

337 citations


Journal ArticleDOI
TL;DR: The pulse energy of the far-infrared radiation is found to be a quadratic function of bias field and a nonmonotonic function of laser intensity.
Abstract: We have generated sub-single-cycle pulses of electromagnetic radiation with pulse energies as high as 0.8 μJ and pulse lengths < 500 fs. The 10-dB width of the spectrum is 1.5 THz. The transmitter is a GaAs wafer illuminated at normal incidence by 120-fs, 770-nm pulses from a Ti:sapphire chirped-pulse amplifier system while a pulsed electric field is applied across the surface. The pulse energy of the far-infrared radiation is found to be a quadratic function of bias field and a nonmonotonic function of laser intensity.

316 citations


Journal ArticleDOI
TL;DR: The concept for a new type of confocal microscope with a fiber-optic imaging bundle is presented, and experimental results are shown to demonstrate the principle.
Abstract: The concept for a new type of confocal microscope with a fiber-optic imaging bundle is presented, and experimental results are shown to demonstrate the principle. The primary advantage of the system is the flexbility of imaging samples that would otherwise be inaccessible to confocal microscopy.

297 citations


Journal ArticleDOI
TL;DR: A new technique, femtosecond transillumination optical coherence tomography, for time-gated imaging of objects embedded in scattering media, derives a fundamental limit on ballistic imaging thickness based on quantum noise considerations.
Abstract: We describe a new technique, femtosecond transillumination optical coherence tomography, for time-gated imaging of objects embedded in scattering media. Time gating is performed with a fiber-optic interferometer with femtosecond pulses and coherent heterodyne detection to achieve a 130-dB dynamic range. A confocal imaging arrangement provides additional spatial discrimination against multiply scattered light. By time gating ballistic photons, we achieve 125-microm-resolution images of absorbing objects in media 27 scattering mean free paths thick. We derive a fundamental limit on ballistic imaging thickness based on quantum noise considerations.

286 citations


Journal ArticleDOI
TL;DR: A five-level model of C60 yields excellent agreement with both pulse-width data sets for incident fluences as high as approximately 1 J/cm2 and additional phenomena observed at higher fluences indicate that other mechanisms may be active and contribute to optical limiting in this regime.
Abstract: Nonlinear absorption at 532 nm in a C60–toluene solution by using 8-ns and 30-ps laser pulses is reported. The transmittance for both pulse widths is fluence dependent. A five-level model of C60 is described that yields excellent agreement with both pulse-width data sets for incident fluences as high as approximately 1 J/cm2. Additional phenomena observed at higher fluences indicate that other mechanisms may be active and contribute to optical limiting in this regime. The application of C60 as an optical limiter material is discussed.

Journal ArticleDOI
TL;DR: A modulator-driven, erbium-fiber ring laser that produces chirp-free pulses with width adjustable over the range of 5 to 100 ps that has extended the error-free distance of a series of soliton transmission experiments by 2000-3000 km over previous results with a mode-locked semiconductor laser.
Abstract: We describe a modulator-driven, erbium-fiber ring laser that produces chirp-free pulses with width adjustable over the range of 5 to 100 ps. A high-finesse Fabry-Perot etalon with a free spectral range equal to the 2.5-GHz laser repetition rate eliminates unwanted laser ring modes and stabilizes the pulse amplitude. Using this laser, we have extended the error-free distance of a series of soliton transmission experiments by 2000-3000 km over previous results with a mode-locked semiconductor laser.

Journal ArticleDOI
TL;DR: It is shown that processes such as second-harmonic generation and subsequent downconversion, and parametric mixing in general, can lead to large field-dependent phase shifts for the input beams under a variety of conditions.
Abstract: We show that processes such as second-harmonic generation and subsequent downconversion, and parametric mixing in general, can lead to large field-dependent phase shifts for the input beams under a variety of conditions.

Journal ArticleDOI
TL;DR: In this paper, the authors demonstrate a simple way of increasing the data acquisition and processing speed in a scanning white-light interferometer for surface topography measurement, which consists of undersampling interference data and processing the resultant sub-Nyquist interferograms in the frequency domain to create complete three-dimensional images.
Abstract: We demonstrate a simple way of increasing the data acquisition and processing speed in a scanning white-light interferometer for surface topography measurement. The method consists of undersampling interference data and processing the resultant sub-Nyquist interferograms in the frequency domain to create complete three-dimensional images. Experimental results on a 20-μm step height standard show a measurement repeatability of 10 nm.

Journal ArticleDOI
TL;DR: It is shown that the optical-limiting behavior is consistent with excited-state absorption (reverse saturable absorption) as a mechanism, and it is suggested that a higher threshold for optical limiting compared with that of C(60) in toluene is due to nonlinear scattering for the liquid.
Abstract: We demonstrate optical limiting for the C60 fullerene in polymethyl methacrylate (PMMA) as a solid polymer host. It is shown that the optical-limiting behavior is consistent with excited-state absorption (reverse saturable absorption) as a mechanism. We suggest that a higher threshold for optical limiting compared with that of C60 in toluene is due to nonlinear scattering for the liquid. The performance of C60 in PMMA is compared with that in chloroaluminum phthalocyanine, N-methylthioacridone, King’s complex, and ruthenium King’s complex in PMMA. Optical damage thresholds are reported.

Journal ArticleDOI
TL;DR: This system is shown to be capable of resolving sub-microstrain changes in the quasi-static strain applied to a grating and has a resolution of ~6 x 10(-3) microstrain/ radicalHz at a strain perturbation frequency of 1 Hz.
Abstract: The operation of a fiber Bragg grating strain sensor system that uses interferometric determination of strain-induced wavelength shifts and incorporates a reference channel to compensate for random thermal-induced drift in the output is described. This system is shown to be capable of resolving sub-microstrain changes in the quasi-static strain applied to a grating and has a resolution of ~6 x 10(-3) microstrain/ radicalHz at a strain perturbation frequency of 1 Hz.

Journal ArticleDOI
TL;DR: A novel distributed temperature sensor that uses the temperature dependence of the frequency at which the loss is maximized in the interaction between a cw laser and a pulsed laser with a 32-km sensing length is presented.
Abstract: We present a novel distributed temperature sensor that uses the temperature dependence of the frequency at which the loss is maximized in the interaction between a cw laser and a pulsed laser. With a 32-km sensing length, a temperature resolution of 1°C has been achieved; it is also shown that a spatial resolution of 5 m may be obtained.

Journal ArticleDOI
TL;DR: This gentler technique should improve the sensitivity of scanning-force microscopy for the imaging of soft samples in aqueous media.
Abstract: An optically trapped prolate glass stylus is the force-sensing element of a novel scanning-force microscope. Stylus displacement is detected with the use of the forward scatter of the trapping laser beam. Radiation forces owing to the three-dimensional intensity distribution near the focus permit the stylus to be both positioned with fine control and oriented along the z (optic) axis. Details of 20-nm size appear in traces recorded with a crude stylus in a trap formed with 1064-nm radiation. The spring constant of the optical-force transducer is below 10−4 N/m, which is to be compared with ∼0.1 N/m for typical mechanical cantilevers used in atomic-force microscopy. This gentler technique should improve the sensitivity of scanning-force microscopy for the imaging of soft samples in aqueous media.

Journal ArticleDOI
TL;DR: The picosecond nonlinear optical response of a metal-dielectric composite made by implanting Cu ions in fused silica, which aggregates during implantation to form nanometer-diameter clusters in a dense, thin layer just beneath the surface of the substrate.
Abstract: We describe the picosecond nonlinear optical response of a metal-dielectric composite made by implanting Cu ions in fused silica. The implanted Cu ions aggregate during implantation to form nanometer-diameter clusters in a dense, thin (~150 nm) layer just beneath the surface of the substrate. The third-order susceptibility X((3)) has an electronic component with a magnitude of the order of 10(-8) esu and is enhanced for laser wavelengths near the surface plasmon resonance of the copper colloids.

Journal ArticleDOI
TL;DR: A new approach for the interrogation of a large number of fiber-optic grating sensors is proposed and demonstrated for a small number of sensors in which signal recovery is achieved by matching a receiving grating to its corresponding sensor.
Abstract: A new approach for the interrogation of a large number of fiber-optic grating sensors is proposed and demonstrated for a small number of sensors in which signal recovery is achieved by matching a receiving grating to its corresponding sensor. This technique is demonstrated for both quasi-static and periodic measurands, and the resolution achieved for a single sensor–receiving grating pair for quasi-static strain is 4.12 μ∊.

Journal ArticleDOI
TL;DR: This work investigates the adiabatic compression of picosecond and subpicosecond soliton pulses from all-fiber, passively mode-locked, erbium-doped fiber soliton lasers operating at 1550 nm in dispersion-decreasing fibers (DDF's).
Abstract: We investigate the adiabatic compression of picosecond and subpicosecond soliton pulses from all-fiber, passively mode-locked, erbium-doped fiber soliton lasers operating at 1550 nm in dispersion-decreasing fibers (DDF's). High-quality soliton compression from 630 down to 115 fs in a 100-m DDF and from 3.5 down to 230 fs in a 1.6-km DDF is obtained. The effects of third-order dispersion and Raman self-scattering on the compression process are observed and discussed.

Journal ArticleDOI
TL;DR: In this paper, the authors developed a simple, high-speed, nearly vibration-free, mechanically scanned, optical delay line suitable for femtosecond time-resolved signal-averaging measurements.
Abstract: We have developed a simple, high-speed, nearly vibration-free, mechanically scanned, optical delay line suitable for femtosecond time-resolved signal-averaging measurements. We demonstrate a 2-ps time window autocorrelator with a display updated at 400 Hz. The delay line uses a dithering planar mirror as a time-varying linear phase ramp in the spectral plane of a modified grating-lens femtosecond pulse shaper. The time delay is linearly proportional to the angular deviation of the mirror. The high speed and low vibration are a result of the extremely small angular changes required to generate a large time delay.

Journal ArticleDOI
TL;DR: The permanent all-optical poling of an azo-aromatic acrylic copolymer is experimentally demonstrated by seeding preparation in a backward phase-conjugation geometry by monitoring the characteristic kinetics of monitored by second-harmonic generation.
Abstract: The permanent all-optical poling of an azo-aromatic acrylic copolymer is experimentally demonstrated by seeding preparation in a backward phase-conjugation geometry. The microscopic mechanism involves an orientational hole burning followed by orientational redistribution caused by trans-to-cis isomerization of the azo-dye chromophores. The characteristic kinetics of growth and decay of the noncentrosymmetry grating is monitored by second-harmonic generation.

Journal ArticleDOI
TL;DR: With an ultrafast time-gated optical detection method, a thin translucent strip of fat hidden inside a 4-cm-thick tissue is located with millimeter spatial resolution with high precision.
Abstract: With an ultrafast time-gated optical detection method, a thin translucent strip of fat (2.5 mm thick) hidden inside a 4-cm-thick tissue is located with millimeter spatial resolution.

Journal ArticleDOI
TL;DR: The system allows one to eliminate spatial inhomogeneities and cubic and quartic phase errors that make existing designs unsuitable for use with pulses much shorter than 100 fs, and is experimentally demonstrate >10,000 times expansion and recompression of ∼25-fs optical pulses.
Abstract: Design of an expansion and recompression system for amplification of sub-20-fs optical pulses to multiterawatt peak powers is presented. The system allows one to eliminate spatial inhomogeneities and cubic and quartic phase errors that make existing designs unsuitable for use with pulses much shorter than 100 fs. We experimentally demonstrate >10,000 times expansion and recompression of ∼25-fs optical pulses.

PatentDOI
TL;DR: A broadly tunable femtosecond optical parametric oscillator (OPO) based on KTiOPO(4) that is externally pumped by a self-mode-locked Ti:sapphire laser is described.
Abstract: A broadly tunable femtosecond optical parametric oscillator (OPO) based on KTiOPO4 is externally pumped by a self-mode-locked Ti:sapphire laser. The laser is capable of continuous tuning from 1.2 micrometers to 1.37 micrometers in the signal branch and 1.8 to 2.15 micrometers in the idler branch, when using one set of OPO optics. Other optics expand the tuning range of the OPO from 1.0 micrometers to 2.75 micrometers, for example, by using three sets of mirrors and two different crystals. Without prisms in the OPO cavity, 215 mW of chirped pulses is generated in the signal branch, while 235 mW is generated in the idler branch. The total conversion efficiency, as measured by pump depletion, is 50%. With prisms in the cavity, nearly transform-limited pulses of 135 femtoseconds are generated, which can be shortened to 75 fs by increasing the output coupling.

Journal ArticleDOI
TL;DR: The optical transpose interconnection system uses a simple pair of lenslet arrays to implement a one-to-one interconnection that is useful for shuffle-based multistage interconnection networks, mesh-of-trees matrix processors, and hypercubes.
Abstract: The optical transpose interconnection system uses a simple pair of lenslet arrays to implement a one-to-one interconnection that is useful for shuffle-based multistage interconnection networks, mesh-of-trees matrix processors, and hypercubes.

Journal ArticleDOI
TL;DR: This work demonstrates the polarization dependence of the nonlinear refractive index or two-photon absorption coefficient in BaF2, KTP, and GaAs at wavelengths of 532 and 1064 nm by incorporating a wave plate into the Z-scan apparatus.
Abstract: We introduce a method for measuring the anisotropy of nonlinear absorption and nonlinear refraction in crystals by incorporating a wave plate into the Z-scan apparatus. We demonstrate this method by measuring the polarization dependence of the nonlinear refractive index or two-photon absorption coefficient in BaF2, KTP, and GaAs at wavelengths of 532 and 1064 nm.

Journal ArticleDOI
TL;DR: In this article, a glass element between the objective and the disk was added to increase the transverse resolution of optical storage systems by as much as a factor of 1.5.
Abstract: We describe a new type of optical pickup for use in high-density optical storage systems. By changing a conventional pickup design to include a glass element between the objective and the disk, the transverse resolution of the system can be increased by as much as a factor of 1.5. This system is also less sensitive than conventional systems to variations in disk thickness and disk tilt. We demonstrate how the system has been used as a microscope to inspect an optical disk and describe possible design configurations for an optical pickup.

Journal ArticleDOI
TL;DR: A pulse-coupled neural network was implemented, for the first time to the authors' knowledge, in a hybrid electro-optical laboratory demonstration system, suggesting a new mechanism for information transmission in a network with limited local connectivity.
Abstract: A pulse-coupled neural network was implemented, for the first time to our knowledge, in a hybrid electro-optical laboratory demonstration system. Dynamic coherent traveling-wave patterns were observed that repeated their spatial patterns at each locality with a period that depended on the local input pattern and strength. Coherence and periodicity were maintained far beyond the physical limits of the linking receptive fields, suggesting a new mechanism for information transmission in a network with limited local connectivity. With no linking, the output became chaotic because the relative phases increased linearly in time.