Showing papers on "Fiber laser published in 1987"

Fiber-optic evanescent-wave methane-gas sensor using optical absorption for the 3.392-μm line of a He–Ne laser

Abstract: Gas sensing using evanescent waves of optical fibers is investigated. Methane gas is detected by means of its strong optical absorption of the 3.392-μm line of a He–Ne laser. A single fiber is used as both a sensor and an optical transmission line. The sensor has a small diameter, ranging from 1.8 to 7 μm, made by heating and expanding a part of a step-index silica fiber. An evanescent wave of 5 to 40% of the total propagating power is generated outside the fiber. When a sensor fiber of 1.8-μm diameter and 10-mm length is used, the minimum detectable concentration of methane is less than the lowest explosive limit of 5%.

Excimer laser angioplasty: Tissue ablation, arterial response, and fiber optic delivery

Abstract: The results of recent work directed towards the application of excimer lasers to angioplasty are presented. Several laser-tissue interactions are examined, including the effect of the XeCl laser optical pulse duration (7-300 ns) on the threshold fluence for ablation of arterial wall and on the quality of the cut in human postmortem artery, the potential for altering the ablation threshold fluence of arterial plaque in swine by treatment with hematoporphyrin derivative, and the healing response of swine arterial wall to surgical irradiation with an argon laser and a pulsed XeCl laser. The dependence of damage thresholds and transmission properties of selected commercial fused silica fibers on the laser pulsewidth and wavelength are determined.

Laser diode pumped fiber lasers with pump cavity

Abstract: A fiber laser having a single mode fiber core of laser material is pumped by a high power coherent laser diode source by providing a multi-mode fiber around the single mode core to define a pump cavity which propagates pump radiation while allowing the pump radiation to couple to the single mode core. Laser diode arrays and extended emitter laser diodes can be used to pump a single mode fiber by inputting the pump radiation into the multi-mode fiber surrounding the single mode fiber core. The milti-mode fiber has a much greater diameter than the single mode core.

Silver halide optical fibers for medical applications

Abstract: Optical fibers fabricated from silver halide crystals (AgCl x Br 1-x ) are transparent in the far infrared ( 3-15 \mu m). They can transmit CO 2 laser radiation with power densities greater than 3 \times 10^{4} W/cm2in the CW mode or short pulses with power densities on the order of 5 \times 10^{6} W/cm2. A laser catheter system based on a silver halide fiber and a pulsed CO 2 laser was used to perform laser angioplasty and atrial septostomy in vivo. A similar system was used to coagulate bleeding gastric ulcers in vivo. Silver halide fibers were also used in diagnostic procedures, such as noncontact temperature measurements during laser surgery and hyperthermia cancer treatment.

Fiber Raman soliton laser pumped by a Nd:YAG laser.

Abstract: We have pumped a fiber Raman laser with a continuous-wave mode-locked Nd:YAG laser operating at 1319 nm and generated pulses as short as 160 fsec by using soliton pulse shaping in the fiber. We have also constructed a completely integrated oscillator loop by using a fiber-optic coupler and fusion splicing.

Laser materials processing with a lensless fiber optic output coupler

Abstract: Laser materials processing apparatus for performing processing with a fiber optic transmitted beam is disclosed. A fiber injecting lens is selected to have a focal length of sufficient length to enable the use, for materials processing, of the diverging beam emitted at an output end of the fiber without the need for a beam focusing lens type output coupler.

Laser diode pumped solid state laser with miniaturized laser head

Abstract: A compact laser head for a solid state laser has a miniaturized laser rod and output coupling mirror which form a miniaturized laser cavity. A miniaturized frequency doubler crystal placed in the cavity provides frequency doubled output. The laser head is connected by an optical fiber to a separate power supply which contains a laser diode pumping source. A quick disconnect connector enables the fiber optic to be easily connected to the laser head. Pumping radiation is transmitted through the optical fiber to longitudinally end pump the laser rod using fiber coupling imagery. The fiber is aligned with the rod by the connector and the pumping radiation is imaged into the rod by a focussing sphere. The pumping volume is matched to the lasing volume which is determined by the cavity geometry. The quick disconnect laser head allows interchange of different heads with different output characteristics while using a single power supply.

A Nd(3+)-doped cw fiber laser using all-fiber reflectors.

Abstract: We demonstrate a novel all-fiber resonant optical cavity which uses two-fiber reflectors, each formed by a single loop of fiber between the output ports of a fiber directional coupler. The reflectivities of the fiber mirrors are each determined by the coupling ratio and the insertion loss of the fused couplers. When the cavity is formed in this way using a continuous length of Nd(3+)-doped fiber and pumped using a GaAs laser diode, lasing occurs at a wavelength of 1064 nm. Both theoretical and practical descriptions of the device are given.

Clad Nd:YAG fibers for laser applications

Abstract: We report the implementation of an extrusion method to clad Nd:YAG single crystal fibers with index-matched glasses ( \Deltan = 0.048 ). A propagation loss coefficient of 0.08 dB/cm was measured for the fundamental mode of a 41-μm-diameter glass-clad fiber laser, an improvement of about one order of magnitude over unclad fibers. Guided clad fiber lasers operated at 1.064 μm with thresholds as low as 0.3-0.5 mW and up to 65-mW CW output power are also reported. The origins of and means of reducing the residual loss are discussed.

High-gain rare-earth-doped fibre amplifier at 1.54µm

Abstract: Optical amplifiers are of interest as wideband in-line repeaters for telecommunications and as signal regenerators for a variety of sensor applications. Much current research has concentrated on semiconductor laser amplifiers which are difficult to splice to fiber systems. It is clear that an amplifier consisting of a special optical fiber which is compatible with telecommunication fiber would overcome this problem. This paper describes the first results of an optical fiber amplifier based on an Er3+-doped fiber which has a maximum gain at a wavelength of 1.536 µm. A single-pass gain of 26 dB and a maximum output of 13 dBm at 140 MHz has been demonstrated

Diode-laser-pumped operation of an Er3+-doped single-mode fibre laser

Abstract: We report the first operation of an Er3+-doped single-mode fibre laser operating around 1.6μm pumped by a CW AIGaAs diode laser. An output power of 130μW was obtained with a lasing threshold of 3 mW.

Transversely coupled fiber Fabry-Perot resonator: theory

Abstract: The theory of output intensities and field strengths of two variants of a four-port fiber-based device called a transversely coupled fiber Fabry-Perot interferometer is presented. The analysis is sufficiently general to consider both input and output from all four arms in both variants. Finesse is calculated for all modes of operation.

Laser Self-Trapping for the Plasma Fiber Accelerator

Abstract: A short-pulsed intense laser is injected into an underdense plasma to sustain a self-trapped photon channel. With either high-enough intensity or strong-enough focusing the optical beam causes total electron evacuation on the beam axis. Under appropriate conditions this laser and plasma fiber system can provide a slow wave structure of the electromagnetic wave that is suitable for high-energy acceleration.

Ion doped, fused silica glass fiber laser

Abstract: An optical fiber laser comprising a nearly pure fused silica glass, neodymium doped active core within a cavity in the form of a single mode optical fiber. The gain cavity is end pumped at a nominal wavelength of 0.8 microns and its length and neodymium concentration are adjusted to maximize pump absorption and minimize concentration quenching. Dichroic mirrors are preferably integrally formed on ends of the cavity and have reflection characteristics selected so that the laser has an output at a nominal wavelength of 1.06 microns.

Optical fibre lasers and amplifiers

Abstract: This thesis describes the development and characterisation of single-mode optical fibre lasers and amplifiers. Although the fibre laser configuration was first employed over twenty years ago, its application to conventional optical fibre technology has not been demonstrated previously. The new devices are based on single-mode fibres doped with rare-earth ions, notably neodymium and erbium. The combination of strong absorption bands, long fluorescence lifetimes; low fibre losses in the infra-red and small fibre cores have made possible very low threshold and efficient fibre lasers. Experiments on the tunability, output spectra and pulsed operation of these devices are described. A number of world firsts, including the Lowest, threshold and widest tuning range of a doped glass laser, and the efficient CW operation of an erbium-doped three level laser, have been achieved. High-gain amplification at 1.54µm, the preferred wavelength for optical communication, has also been demonstrated. The results have been modelled by adapting conventional laser theory to the single-mode fibre configuration, and some simple design criteria are considered.

Neodymium-doped fluoro-zirconate fibre laser

Abstract: We report for the first time lasing in a multimoded neodymium-doped fluoro-zirconate fibre. Close to threshold we observe a single line of less than 1 a?ngstrom width. The threshold is high and efficiency is low, but we believe that significant improvements will be achieved with single-mode geometry.

Single-mode fiber components

Abstract: A variety of optical components have been made directly from single-mode fibers. These components can be combined to construct in-line all-fiber systems such as fiber gyroscopes, fiber Raman lasers, local area networks, or coherent lightwave systems. This paper reviews the present state of passive and active single-mode fiber components. Passive components are polarizers, directional couplers, filters, and Faraday rotators. Active components require external control or optical power and include modulators, polarization controllers, frequency shifters, and amplifiers. Polarization is usually important in fiber components and discussions of polarization-maintaining and ordinary single-mode fibers are included.

Low-threshold CW operation of an erbium-doped fibre laser pumped at 807 nm wavelength

Abstract: We report an erbium-doped fibre laser operating CW at a wavelength of 1555nm pumped at a wavelength of 807 nm, with a threshold launched pump power of 2.5 mW. This level corresponds to only 1 mW of pump power absorbed.

Subpicosecond fiber laser

Abstract: A fiber laser for producing subpicosecond pulses is formed by placing a laser fiber in a resonant cavity, in either a linear or closed loop configuration. The laser fiber is formed of two different types of fibers joined in series, a gain fiber which contains the laser gain medium followed by a pulse shaping fiber which uses the phenomenon of solution pulse shaping to shorten the pulses. An initially formed pulse recirculates many times in the resonator; on each pass the pulse is both amplified and shortened until steady state is reached. The zero dispersion wavelength of the pulse shaping fiber is chosen to be slightly less than the laser wavelength. The fiber is pumped by a continuous source, particularly CW laser diodes. The initial pulse can be formed by a self starting technique produced by selecting the proper length of the laser fiber, or else a mode locker/acousto-optic shutter can be placed in the cavity.

Intensity Modulated Fiber Optic Sensors Overview

Abstract: Intensity modulated fiber optic sensors have the many distinct advantages associated with fiber optics that makes them suitable for several industrial and military applications. Although, the accuracy of the sensor is far less that for interferometric sensors, the accuracy is more than sufficient for most process control situations. The concepts for intensity modulated fiber optic sensors include: transmissive, reflective, microbending and intrinsic mechanisms. The paper describes the various concepts and applications.

Pulse characteristics of Q-switched fiber lasers

Abstract: A theoretical investigation of the anticipated properties of optically end-pumped Q -switched fiber lasers is reported. This analysis stresses the effect of the transverse structure of the interacting pump and signal (guided) waves, in particular of the fiber V number, on the device performance. In Nd : YAG single crystal fibers thresholds as low as a fraction of a milliwatt may be achieved; pulses with peak powers of hundreds of watts and subnanosecond widths may be generated under laser diode pumping conditions.

Optical fiber transmission of high power excimer laser radiation

Abstract: An experimental investigation of optical fiber transmission of high power excimer laser radiation is presented. Different types of commercially available UV fiber have been tested, measuring energy handling capabilities and transmission losses of short samples at the XeCl (308-nm) and KrF (249-nm) wavelengths by using a standard excimer laser. A power density dependent damage process has been observed over 1 GW/cm(2). Fiber losses due to different radii of curvature are also reported. Experimental results have been examined to evaluate the effectiveness of excimer laser transmission through optical fibers for such medical uses as laser angioplasty, including also a comparison between the use of KrF or XeCl emission lines for this purpose. Finally, optimum excimer laser characteristics to increase the energy coupling in fibers are discussed.

High-efficiency Nd-doped fibre lasers using direct-coated dielectric mirrors

Abstract: The letter presents an Nd-doped silica single-mode fibre laser with dielectric mirrors coated directly on to the fibre endfaces The LD-pumped fibre laser had a CW output power of more than 4mW, a threshold power of 151 mW and a slope efficiency of 55% The theoretically predicted values and experimental values of the laser characteristics are very similar owing to a negligibly small excess cavity loss

Optical fiber and laser interface device

Abstract: A laser-optical fiber interface including the combination of a solid state laser producing a point source of polarized light and a polarization-holding, single-mode optical fiber. The optical fiber comprising a core and cladding of non-circular cross section and having different refractive indices forming a single mode guiding region which permits the de-coupling of waves polarized along the axis of the fiber. The outer surface of the fiber includes an indexing surface with a predetermined geometric relationship to the guiding region. The optical fiber being mounted upon a substrate for receiving and supporting the indexing surface of the fiber with the solid state laser so that the end of the fiber is placed and aligned adjacent the solid state laser.

Four-photon fiber laser.

Abstract: Strong infrared optical signals at the wavelengths 0.991 and 1.149 microm were produced as a result of phase-matched four-photon mixing when Nd:YAG laser light was coupled into a <4-m-long piece of single-mode glass fiber. Stimulated gain was observed, and laser action was obtained with the fiber in an external cavity.

Laser-beam writing system for optical integrated circuits

Abstract: A computer-controlled laser-beam writing system has been developed for optical integrated circuits (optical ICs). This system allows us to make waveguide patterns 3-4 microm wide, such as directional couplers, and Yjunction, crossed, and S-shaped waveguides, automatically within an edge roughness of 0.2 microm on a photoresist-coated LiNbO(3) substrate. By combining these waveguide patterns, optical ICs can be delineated over more than 50-mm length. This paper presents the system description and the laser-beam writing characteristics of key waveguide patterns. The integrated-optic fiber laser Doppler velocimeter is also demonstrated as an example of large-area optical ICs.

Diode-laser-pumped Nd3+-doped fibre laser operating at 938 nm

Abstract: We report the efficient diode-laser-pumped operation of an Nd3+-doped single-mode fibre laser at 938 nm on the three- level transition 4F3/2−4I9/2. An output power in excess of 3 mW has been obtained with a threshold of 1.9 mW.

Using a 1.5-μm DFB InGaAsP laser in a passive ring cavity-type fiber gyroscope

Abstract: It has been demonstrated that a 1.5-μm distributed feedback InGaAsP laser can be used as a coherent light source in a passive ring cavity-type fiber gyroscope. A formula for the detector shot noise-limited sensitivity of detection of rotation was derived for this type of gyroscope. Its value in the present experimental setup was estimated as being 0.8 · τ1/2 degree/hour, where τ represents the integration time of measurements. Experiments showed that the uncertainty of the detection of rotation was 1.5°/h at τ = 100 s, which was governed by the slight reflection of light at the AR-coated fiber edges and residual frequency fluctuations of the laser.