Showing papers on "Fiber laser published in 1984"

Fiber-optic lattice signal processing

Abstract: We discuss the implementation of fiber-optic lattice structures incorporating single-mode fibers and directional couplers. These fiber structures can be used to perform various high-speed time-domain and frequency-domain functions such as matrix operations and frequency filtering. In this paper we mainly consider systems in which the signals (optical intensities) and coupling coefficients are nonnegative quantities; these systems fit well in the theory of positive systems. We use this theory to conclude, for example, that for such systems the pole of the system transfer function with the largest magnitude is simple and positive-valued (in the Z-plane), and that the magnitude of the frequency response can nowhere exceed its value at the origin. We also discuss the effects of various noise phenomena on the performance of fiber-optic signal processors, particularly considering the effects of laser source phase fluctuations. Experimental results are presented showing that the dynamic range of the fiber systems, discussed in this paper, is limited, not by the laser source intensity noise or shot noise, but by the laser phase-induced intensity noise. Mathematical analyses of lattice structures as well as additional applications are also presented.

The Soliton Laser

Abstract: The soliton laser1 is a novel mode-locked device employing a length of single-mode fiber in its feedback loop. Its pulse width can be made to have any desired value, down to a small fraction of a picosecond, through choice of the fiber’s length. Operation is based on the ability of single-mode fibers, in the region (λ> 1.3 µm) of negative group-velocity dispersion, to support periodic soliton pulses, as well. as to narrow broader-pulses of the same energy.2,3 As the fiber is the all-important control element, pulse shape and width are largely independent of factors, such as details of gain dynamics and pump pulse width, that are normally of prime importance in mode-locked lasers.

Industrial hand held laser tool and laser system

Abstract: Laser processes such as cutting, drilling, and welding metals and other materials are performed manually with a hand held fiber optic laser tool. A near infrared or visible wavelength pulsed laser beam is coupled to the tool by a single clad quartz fiber whose ends are prepared to reduce losses and which transmits laser energy with peak powers in the kilowatt range to the output end. The hand held laser tool is comprised of focusing optics for the laser beam, an inert gas supply for welding cover gas, and an oxygen supply for gas assist cutting.

High power laser energy delivery system

Abstract: A low-divergence 1.06 micrometer wavelength beam from a total-internal-reflection, face-pumped laser (TIR-FPL) is focused onto the end of a quartz optical fiber to a spot having a size smaller than the fiber diameter and with a beam cone angle less than twice the numerical aperture of the fiber. The fiber transmits the energy to emerge at the other end where it is collimated and focused onto material to be processed. A laser average output power level greater than 400 watts can be transmitted through an optical fiber having a diameter less than 600 micrometers.

Lens coupling of laser diodes to single-mode fibers

Abstract: This paper studied the effect of lens aberration on coupling efficiency and loss penalty due to misalignment for a laser diode to single-mode fiber couplers. The theoretical results were in very good agreement with experimental values and the validity of the present analysis was confirmed. The paper made clear that coupling loss is dominated by aberration and proposed some basic approaches to improving coupling efficiency.

Lens-ended fibers for medical applications: a new fabrication technique.

Abstract: Microlens-ended fibers may be of great usefulness in medical applications, in particular in endoscopic laser treatment and surgery. Previous fabrication techniques of integral microlenses have mainly faced the problems related to optical communications, where damage due to high-power lasers does not occur. We describe a novel method, the laser-microfurnace technique, which uses the laser energy delivered by the fiber itself to create a microfurnace in a suitable material that reirradiates energy in a different wavelength band and causes the fiber tip to melt. This easy and reliable method is applicable to all types of fiber, even those with pure-silica core and large core diameter. No special equipment or training of the operator is required, so fabrication of microlenses may be carried out even in the surgery room. Experimental process parameters are reported.

External-cavity laser design

Abstract: External cavity stabilized semiconductor lasers using laser cavities \lsim 200 \mu m and etalon cavities between 50 and 200 μm appear suitable for single-longitudinal-mode sources in high data rate fiber communication systems. The design of cavity lengths, losses, and mirror reflectivities are considered for optimum device performance. Using obtainable parameters, it appears possible to provide a sufficient overdesign to allow reasonable changes in optical path lengths and temperature without loss of the required spurious mode suppression.

Method of aligning a polarization-preserving optical fiber with a semiconductor laser for attachment of the fiber to the laser

Abstract: A method of aligning the polarization-preserving axis of a receiving end of a polarization-preserving optical fiber with the linearly-polarized output of a semiconductor laser in which the fiber optic end is placed substantially adjacent the laser rather than being separated from the laser by a polarizing optical system.

Digital transmission of TV signals with a fiber-optic heterodyne transmission system

Abstract: A heterodyne-type fiber-optic television transmission is reported. The setup consists of a semiconductor transmission laser, a polarization maintaining fiber, and a heterodyne receiver with a local laser, fiber coupler, and an avalanche photodiode. Further, an interference experiment between two coherent optical channels was performed.

Clinical measurements using fiber optics and optrodes

Abstract: Fiber optics, optrodes, and fluorescence spectroscopy have been combined to form the new technology of remote fiber fluorimetry (RFF). Both in-vivo and in-vitro clinical measurements can be made by using this technique. The optrode, a fiber termination with preselected chemical or physical properties, is attached to the distal end of the optical fiber so that specific, in-situ measurements can be made. RFF systems for pH, blood pressure, oxygen, and carbon dioxide are being completed, and other optrodes are in the development stages.

Single-mode operation of 1.3 µm InGaAsP/InP buried crescent lasers using a short external optical cavity

Abstract: Highly single longitudinal mode operation of 1.3 μm InGaAsP/InP buried crescent lasers has been obtained using a 60-600 \mu m long external cavity defined by a spherical mirror. The intensity of the neighboring modes was suppressed by a factor of 1200 for dc excitation and by a factor of 800 for combined dc and 250 MHz current modulation.

A high-power fiber optic laser Doppler velocimeter

Abstract: A fibre optic Doppler difference type laser velocimeter for use with high optical powers has been devised and constructed. The system provides a flexible monomode optical fibre link between the argon ion laser used and the launching optical system, which illuminates the measurement volume. A multimode optical fibre links the receiving optical system and the photodetector. Optical powers of up to 500 mW were delivered to the measurement volume.

Single Crystal Fibers By The Laser-Heated Pedestal Growth Method

Abstract: The versatility of the laser heated pedestal growth method for producing a wide range of compounds in single crystal fiber form is discussed along with some potential applications. Some preliminary results on the growth of single domain LiNb0 3 crystals, and crystals of BaF 2 and CaF 2 , sapphire and several laser materials are discussed.

Theoretical And Experimental Analysis Of A Fiber Optic Proximity Probe

Abstract: To allow computer synthesis of the response of commercial multifiber optical proximity probes, an investigation was made of the response of a single pair of fibers. A theoretical and experimental analysis was made of the coupling of an illuminating and receiving fiber through reflection off a dull or specular target. A computer program was developed that superposes the responses of all fiber pairs in a probe that may contain up to 2400 fibers, with a total of 1200 2 pairings maximum. A comparison is made between the computed and measured response of an actual probe.

Use of a laser diode and an optical fiber for a compact laser-Doppler velocimeter

Abstract: In order to make an optical-fiber-type laser-Doppler velocimeter (LDV) more compact, we propose the use of a laser diode as the coherent light source. To reduce the optical feedback on the laser source, a polarization-maintaining single-mode fiber was adopted. We have confirmed that the LDV system can be compact and also that it can have a velocity resolution of a few millimeters per second and a signal with a 20-dB signal-to-noise ratio, which are similar to the resolution and signal-to-noise ratio obtained with a He–Ne laser.

Raman amplification of 1.50-µm laser diode light in a low fiber loss region

Abstract: Raman amplification utilizing the second Stokes line of 1.32-μm Nd:YAG laser light in a single-mode silica fiber was observed. Raman gains of 24 dB have been obtained for 1.50-μm laser diode light in the low-loss region. In addition, the signal-to-noise characteristics of Raman amplification using the second Stokes line was investigated. As a result, it became clear that the S/N ratio was inferior to that in 1st Stokes line by about one order of magnitude.

Laser diode to fiber coupling using anamorphic gradient-index lenses

Abstract: A lens design approach using anamorphic gradient-index components is used to examine the problem of coupling light from a laser diode to a multimode fiber.

Synchronously pumped D 2 gas-in-glass fiber Raman laser operating at 1.56 μm

Abstract: A synchronously pumped D2 gas-in-glass fiber Raman laser operating at 1.56 μm has been demonstrated. The active medium is molecular D2 diffused into a 100-m-long conventional single-mode solid silica optical fiber. Synchronous pumping with a mode-locked 1.06-μm Nd:YAG laser (120-psec pulse width with 100-MHz repetition rate) produces 15-psec pulses at 1.56 μm with peak output powers of 20 W.

Optically-Powered Transducer With Optical-Fiber Data Link

Abstract: A novel transducer with optical-fiber data link -- to provide electrical isolation and immunity from electromagnetic noise -- has been developed. A pulse-position (or pulse-frequency) modulated optical signal is transmitted by optical fiber from a remote converter to mainframe. Light of a different wavelength is transmitted via the same optical fiber from a laser in the mainframe to a photocell battery in the remote converter, to power it. Signal and "power" light beams are separated by dichroic mirrors. A practical thermocouple converter is described; it consumes only 84 μW, and is powered by light from a 5 mW semiconductor laser in the mainframe.

130-km-long fault location for single-mode optical fiber using 1.55-μm Q-switched Er 3+ :glass laser

Abstract: An optical-time-domain reflectometer has been constructed with a 1.55-μm Er3+:glass laser, a TeO2 acousto-optical directional coupler, and a cooled Ge P-I-N photodiode. With it, a maximum detectable fault-location length of 130 km for single-mode optical fiber has been successfully achieved at a 1.55-μm wavelength.

Carbon monoxide laser power delivery with an As2S3 infrared glass fiber

Abstract: High-intensity delivery of CO laser (λ ≃ 5.4 μm) power by an As2S3 chalcogenide glass optical fiber is reported. Transmission of 4-W cw power is achieved in a 200-μm core diam unclad fiber without any deterioration. Light intensity of 12.8 kW/cm2 at the fiber output was attained. Use of this power for various applications, especially medical, is discussed.

Oxide Glass Hollow Fiber For CO 2 Laser Radiation Transmission

Abstract: The feasibility study of a new type of hollow-core waveguide for CO2 laser radiation guidance is described. This kind of fiber has an air core surrounded by an oxide-glass cladding which for Ary10.6 μm exibis a complex refractive index with real part <1. Curves of the measured reflectivity and real and immaginary part of the refractive index for glass samples with different PbO percentage are shown, along with attenuation measurements performed on fiber drawn from such glasses.

Attaching single-mode polarization-preserving fiber to single mode semiconductor lasers

Abstract: The coupling of a semiconductor laser as a coherent well-polarized source to birefringent polarization-maintaining fiber is an important step in exploiting the unique characteristics of this waveguiding medium. The total light output of most semiconductor lasers is relatively poorly polarized yielding extinction ratios of the order of 10–12 dB. We wish to report here alignment and coupling characteristics of a linear polarized single-mode semiconductor laser to a highly birefringent fiber for polarization-maintaining purposes. We have observed extinction ratios in excess of 20 dB between the two axes of the fiber using a simplified alignment method which utilizes the natural polarization of the laser and the relatively narrow acceptance angle of the fiber as a spatial filter. A simple method of alignment and permanently attaching the fiber to the laser is described.

Fiber‐optic laser Doppler velocimeter using an external‐cavity semiconductor laser

Abstract: Influence of the spectral linewidth Δν of a semiconductor laser on the performance of a fiber‐optic laser Doppler velocimeter (FLDV) was investigated. By using an external‐cavity laser with Δν≂0.3 MHz, we could build a FLDV having an optical fiber probe length up to 25 m long.

Fiber Technology: From Film to Fiber

Abstract: This book is intended to fiber technologists, textile dealers, and textile salesmen a practical guideline to become acquainted with and to deepen their knowledge of the processes for the manufacture of film tapes, split-film yarns, and fibrillated film fibers.

Continuous-wave Raman oscillation for a Nd 3+ :YAG intracavity fiber laser

Abstract: Continuous-wave Raman oscillation characteristics of a Nd3+:YAG intracavity fiber laser are described. The laser has two threshold levels: one is for the oscillation of a 1.064-μm Nd3+:YAG laser, and the other is for a fiber Raman laser oscillation of 1.122 μm. The oscillation of the fiber Raman laser is produced with the aid of optical pumping resulting from the oscillation of the 1.064-μm YAG laser, i.e., the optical pumping gain medium and the fiber Raman gain medium share a common laser cavity. For a 330-m-long single-mode fiber resonator configuration, the output power of the fiber Raman laser is about 0.32 mW, which corresponds to about 30% of the 1.064-μm laser power.

Method and means for high resolution measurement of fiber diameter

Abstract: Changes in the diameter of a fiber are determined by directing a laser beam transversely onto the fiber and directing a fringe produced by the scattering of the beam to a photodiode array by means of a transforming lens. Circuitry is provided to detect movement of the fringe on the diode array thereby indicating changes in the diameter of the crystal fiber.

Single-mode-fiber saturable absorber.

Abstract: Saturable absorption is performed on a signal in a single-mode fiber by allowing the evanescent field of the guided wave to interact with a saturable-absorbing dye. The evanescent field is exposed by mechanically removing a portion of the fiber cladding. The saturable material is then placed in close proximity to the fiber core. The singlemode-fiber saturable absorber is characterized by a nonlinear transmission versus input optical intensity. Transmissions ranging from 50 to 80% have been demonstrated using Eastman 9860 saturable-absorbing dye and optical pulses from a Q-switched Nd:YAG laser.