Showing papers on "Fiber laser published in 1988"

Infrared laser catheter system

Abstract: Laser energy produced by a laser operating in the mid-infrared region (approximately 2 micrometers) is delivered by an optical fiber in a catheter to a surgical site for biological tissue removal and repair. Disclosed laser sources which have an output wavelength in this region include: Holmium-doped Yttrium Aluminum Garnet (Ho:YAG), Holmium-doped Yttrium Lithium Fluoride (Ho:YLF), Erbium-doped YAG, Erbium-doped YLF and Thulium-doped YAG. For tissue removal, the lasers are operated with relatively long pulses at energy levels of approximately 1 joule per pulse. For tissue repair, the lasers are operated in a continuous wave mode at low power. Laser output energy is applied to a silica-based optical fiber which has been specially purified to reduce the hydroxyl-ion concentration to a low level. The catheter may be comprised of a single optical fiber or a plurality of optical fibers arranged to give overlapping output patterns for large area coverage.

Semiconductor laser optical amplifiers for use in future fiber systems

Abstract: The application of semiconductor laser amplifiers to long-wavelength optical fiber systems is discussed. The basic equations defining laser amplifier characteristics are presented together with experimental results. Linear and nonlinear modes of operation are considered; the former includes use as an optical gain block, a linear repeater, and a preamplifier, while the latter includes use as a bistable element, an electrically controlled optical switch, and an injection-locked amplifier. >

DOUBLE CLAD, OFFSET CORE Nd FIBER LASER

Abstract: The earlier glass lasers in both rod and fiber form were mostly side pumped.1 With the demonstration of single mode CW fiber lasers doped with Nd in low loss glass2 there followed considerable work with end pumped fiber lasers with many of the rare earths that had lased.3-6 In this paper, the behavior of a single mode Nd fiber laser with a double clad configuration is described in which light focused into the first cladding is absorbed by the neodymium core as the pump light proceeds down the fiber. This allows use of multimode pump sources and relatively simple focusing systems for efficient coupling.

Compound optical-fiber-based resonators

Abstract: The relative merits of three designs of compound optical-fiber-based resonators for application to line narrowing in fiber lasers and demultiplexing in optical-communications systems are discussed. The three resonator designs are a set of concatenated rings, a three-reflector resonator with loop mirrors, and a fiber Fox–Smith interferometer.

Three-level fiber laser amplifier: a theoretical model.

Abstract: A theoretical analysis of a three-level fiber laser amplifier in the small-signal regime is presented in which the effects of the transverse variation of the pump and signal mode intensities, the transverse variation of the density of the lasing species, and excited-state absorption of pump photons are included. Guidelines for the design of an optimum fiber are given.

Continuous-wave oscillation of a monomode ytterbium-doped fibre laser

Abstract: The last few years have seen intense interest and activity in the field of rare earth doped monomode fibre lasers and amplifiers [1,2],since these components could be used in fields as diverse as medicine and communications. Furthermore their small active volume offers a number of important advantages over conventional bulk glass lasers. We have chosen to investigate ytterbium doped fibre as it provides a very "clean" system (ie free from excite-q state absorption. Apart from the energy levels around 11,000cm there are no other levels until the ultra-violet). The ytterbium fibre laser should therefore offer a good system on which to test some of the basic physics of fibre lasers. In addition it offers 3-level, 4-level and quasi 3-level laser transitions. Published work on ytterbium doped glass lasers in bulk form has been sparse with the main publication being that of Snitzer [3]. In this paper we describe the characteristics of an ytterbium-doped, silica based, monomode fibre laser operating at discrete wavelengths in the range 1035nm to 1076nm.

Continuous wave lasing at 2.7 μm in an erbium-doped fluorozirconate fibre

Abstract: A fibre laser operating at 2.702 mu m using fluorozirconate fibre doped with <0.1 mol.% of erbium is reported. The authors propose that the mechanism which allows CW operation is absorption of pump radiation by ions in the lower lasing level.< >

Fiber Fox–Smith resonators: application to single-longitudinal-mode operation of fiber lasers

Abstract: An optical-fiber Fox–Smith resonator was demonstrated for the first time to our knowledge. It was applied to obtain single-longitudinal-mode operation from an erbium-doped fiber laser. Both the passive performance and the active performance of the device are studied in detail. Good agreement is found between theoretical and experimental results.

Lasing at 2.08 mu m and 1.38 mu m in a holmium doped fluoro-zirconate fibre laser

Abstract: We report for the first time a fibre laser operating beyond the 1.55μm communications window. Using a holmium doped fluoro-zirconate fibre, laser emission occurs from the threelevel 2.08μm transition, and also at 1.38μm via a cascading transition.

Single-longitudinal-mode operation of an Nd3+-doped fibre laser

Abstract: We report the first operation of an Nd3+-doped monomode fibre laser oscillating in a single longitudinal mode. The laser incorporated an integral fibre grating used as a narrowband reflector. The lasing linewidth was measured as 1.3MHz FWHM at a wavelength of 1082nm.

1.3μm fluoride fibre laser

Abstract: Laser action has been achieved in the 133–134μm range using an Nd3+-doped fluorozirconate glass multimode fibre These operating wavelengths are the closest to the important telecommunications channel at 13μm of any reported for glass laser

Fiber optic laser joining apparatus

Abstract: Fiber optic laser apparatus for spot welding, brazing, or soldering comprises an optical fiber for transmitting a laser beam to a workpiece, and a tool disposed at an output end of the optical fiber for mechanically engaging and applying pressure to the workpiece The output end of the optical fiber is supported within a longitudinal bore of the tool with the tip of the fiber closely adjacent to an opening in a workpiece-engaging end of the tool The diverging laser beam from the end of the optical fiber projects a spot onto the workpiece through the opening with sufficient power to cause melting without the necessity for a lens system for focusing of the laser beam

Efficient operation of an Yb-sensitised Er fibre laser at 1.56 μm

Abstract: We report operation of a high-efficiency Yb:Er single-mode fibre laser. Pumping at wavelengths of 1064nm and at 820nm has shown low pump thresholds ( < 7 and 4mW) and high slope efficiencies (4.2 and 7.0%).

Optical fiber output coupler for a power laser

Abstract: An optical fiber output coupler for application to a power laser beam transmitting optical fiber is disclosed. The output coupler includes lenses for expanding the fiber delivered beam in order to enable minimization of the diameter of a focussed spot provided by a focussing lens of the coupler.

Broadband diode-pumped fibre laser

Abstract: Reports the observation of a strong dependence of the emission spectrum (centre wavelength and linewidth) of Nd:silica fibre lasers on pump wavelength. In a particular fibre, careful selection of the pump wavelength has led to the operation of a broadband fibre laser at 1060 nm with 19 nm FWHM bandwidth. When pumped with a 30 mW diode laser, it exhibits a 1 mW threshold, a 2.5 mW output, and an intrinsic average wavelength temperature stability of about 10 p.p.m./ degrees C.

Jones calculus analysis of single-mode fiber Sagnac reflector

Abstract: It is postulated that stray birefringence degrades the performance of the single-mode fiber Sagnac reflector. An expression for the birefringence dependence of reflector performance is derived using the Jones calculus and is used as the basis for a theoretical model of the spectral response of a real Sagnac reflector. The experimental behavior of the reflector with (1) different levels of stress applied to the fiber loop and (2) different lengths of highly birefringent fiber spliced into the loop are compared with the model. This comparison confirms the initial postulate.

Broadband-tunable external fiber-cavity laser

Abstract: A broadband-tunable external fiber-cavity laser system includes a laser diode, and a single-mode optical fiber with an in-line fiber optic grating filter. The grating filter includes a grating with divergent ridges so that the periodicity at an exposed evanescent field can be adjusted by translating the grating transversely with respect to the fiber. The evanescent field of light transmitted along the fiber core is accessed at a side-polished region. The laser preferentially oscillates at the reflected wavelength, so that the laser output is tuned by moving the grating. The grating is manufactured by oblique exposure to a holographic wavefront, producing the divergent pattern.

Measurement of head/disk spacing modulation using a two channel fiber optic laser Doppler vibrometer

Abstract: A two-channel laser Doppler vibrometer system is described for studying spacing modulation of the head/disk interface in a magnetic recording disk file. Three types of sliders, namely a standard two-rail slider, an experimental negative-pressure slider, and a cross-cut slider, are studied. In comparing the results from the single-channel and dual-channel laser Doppler systems, excellent agreement is observed for the resonant frequencies of the air bearing. The single-channel system, however, exhibits problems with offset in the velocity and displacement signals that are absent with the two-channel system. >

Efficient operation of an Yb-sensitised Er fibre laser pumped in 0.8 μm region

Abstract: The dependence of threshold and slope efficiency on pump wavelength around 0.8µm has been investigated for an Yb-sensitised fibre laser. Results confirm a wider choice of pump wavelength compared with unsensitised Er fibre. A 5mW threshold and slope efficiency of 8.5% were observed for 820-830nm pumping.

Coupling device for high power laser beam transmitting optical fibers

Abstract: A fiber optic coupling device for coupling two optical fibers transmitting a high power laser beam is disclosed. In one embodiment, the device comprises a first lens to collimate the beam delivered by one of the optical fibers and a second lens to focus that collimated beam onto the end of the other fiber for injection therein and continued transmission of the power laser beam through the second fiber.

Saturated semiconductor laser amplifier for compensation of optical fibre dispersion

Abstract: The span of an optical dispersion-limited fiber for propagating optical pulses is improved by simultaneously chirping and amplifying the stream by means of a saturated semiconductor laser amplifier. The chirp causes a compression of the pulses as they propagate through an initial portion of the fiber, whereby the span of the fiber is increased.

ERBIUM FIBER LASER AMPLIFIER AT 1.55µm WITH PUMP AT 1.49µm AND Yb SENSITIZED Er OSCILLATOR

Abstract: The first erbium glass lasers at 1.54μm were made from alkali, alkaline earth silicates with ytterbium added as a sensitizer.1 They were used primarily as Q-switched oscillators for eye safe range finders.2,3 With the demonstration of CW fiber lasers doped with Nd in low loss glass,4 there followed considerable activity with CW fiber lasers with the rare earths that had lased.

Lasing characteristics of Er3+‐doped silica fibers from 1553 up to 1603 nm

Abstract: The laser oscillations from 1553 up to 1603 nm have been demonstrated in Er3+‐doped silica fibers with a doping rate of 2500 ppm. Wide changes in laser oscillation wavelengths are due to broad splitting of the upper sublevels in the 4I15/2 manifold, caused by the random structure of the silica matrix. It has been shown that unpumped parts of the Er3+ ions in the end pumped fiber laser configuration play an important role in the wavelength changes of the laser oscillation. For an absorbed pump power of 320 mW at 514 nm, output power of 0.5 mW was obtained at 1603 nm.

Control of power-splitting ratio in asymmetric fused-tapered single-mode fiber couplers

Abstract: The extent of coupling in asymmetric fused-tapered single-mode fiber couplers is found to vary not only with the initial cladding diameters of the fibers to be tapered but also with the degree of fusion in the coupler. It is thus possible to optimize the coupling efficiency of dissimilar-fiber couplers by adjusting the degree of fusion without resort to etching the fibers. A simple slab-waveguide model is described that can account for these trends in coupler performance.

High-power, mode-locked Nd:fibre laser pumped by an injection-locked diode array

Abstract: A neodymium-doped fibre laser has been actively mode-locked to produce pulses shorter than 120 ps using an intracavity acousto-optic loss modulator. The laser operated at 1.088 mu m at an average power of 5 mW when pumped by an injection-locked diode array, which coupled approximately 40 mW of 0.82 mu m into the fibre. A peak pulse power of 1 kW was obtained in Q-switched operation.

Efficient operation of array-pumped Er3+ doped silica fibre laser at 1•5 μm

Abstract: We present the results for diode-array pumped Er3+ doped silica fibres, which lase near 1550 nm. A maximum output power of 8 mW is obtained with a 13% overall efficiency against the launched pump power.

Spectroscopy During Laser Induced Shock Wave Lithotripsy

Abstract: In the course of laser induced shock wave lithotripsy (LISL) by means of a flashlamp pumped dye laser a plasma is formed on the stone's surface. Spectral analysis of the plasma flash leads to chemical stone analysis during the procedure. A time resolved integral analysis of scattered and laser induced fluorescence light makes stone detection possible and avoids tissue damage. We used a 200 μm fiber to transmit a 2 μs, 50 mJ pulse to the stone's surface and a second 200 μ fiber for analysis. This transmission system is small and flexible enough for controlled endoscopic use in the treatment of human ureter or common bile duct stones. Under these conditions the stone selective effect of lasertripsy leads only to minor tissue injury.