Showing papers on "Fiber laser published in 2001"

Thermal, stress, and thermo-optic effects in high average power double-clad silica fiber lasers

Abstract: Yb:glass fiber lasers have matured to the point where the average power scaling of such devices to the kilowatt level and beyond can be realistically pursued. In this paper, we present a comprehensive study of thermal, stress, and average power scaling in double-clad silica fiber lasers. We show that careful management of thermal effects in fiber lasers will determine the efficiency and success of scaling-up efforts.

Rare-Earth-Doped Fiber Lasers and Amplifiers, Revised and Expanded

Abstract: Rare-Earth-Doped Fiber Lasers and Amplifiers, Second Edition discusses the essential principles, operating characteristics, and current technology of the main fiber laser and amplifier devices based on rare-earth-doped silica and fluorozirconate fibers. Covering all aspects of this revolutionary technology, the book reviews fiber fabrication methods and the basic spectroscopic properties of rare-earth ions in glasses, concentrates on the most important fiber laser sources, examines several advances in fiber amplifiers, and analyzes new findings and improvements in single-frequency operation, frequency tenability, broadband fiber sources, and blue-green and far-infrared fiber lasers.

High-temperature stability of long-period fiber gratings produced using an electric arc

Abstract: We report, for the first time to our knowledge, the excellent optical performance of long-period gratings written in three standard fibers and in two nonstandard fibers, namely, S-doped and N-doped fibers, using the flexible and low-cost electric arc technique The fundamental mechanism for their formation is proposed The grating thermal behavior and the effect of fiber preannealing prior to writing have been investigated We have demonstrated a good stability of these gratings at high temperatures

Observation of bound states of solitons in a passively mode-locked fiber laser

Abstract: We report on an experimental observation of bound states of solitons in a passively mode-locked fiber soliton ring laser. The observed bound solitons are stable and have discrete, fixed soliton separations that are independent of the experimental conditions.

Multiwavelength fiber laser sources with Bragg-grating sensor multiplexing capability

Abstract: Two erbium-doped fiber ring lasers (EDFRLs) wvith simultaneous emission at four different wavelengths are demonstrated. Both systems employ fiber Bragg gratings (FBGs) to select the operation wavelengths within the ring. The sensing capability of the FBGs has been taken advantage of, allowing for the sources to be used as sensor multiplexing schemes. The first system employs four FBGs in a tree filter topology, achieving four output channels with -5 dBm power each. The second system comprises an in-line filtering topology with active fiber segments within the filter. This second source yields 2-dBm output signals and allows for a higher number of lines to be easily added to the system. A comparison between both topologies is carried out, and their capability for sensor multiplexing is demonstrated.

Cladding pumped Ytterbium-doped fiber laser with holey inner and outer cladding.

Abstract: We have fabricated an ytterbium doped all-glass double-clad large mode area holey fiber. A highly efficient cladding pumped single transverse mode holey fiber laser has been demonstrated, allowing continuous-wave output powers in excess of 1W with efficiencies of more than 80%. Furthermore both Q-switched and mode-locked operation of the laser have been demonstrated.

A high-brightness laser beam from a phase-locked multicore Yb-doped fiber laser array

Abstract: We observed a high-brightness laser beam emitted from a closely packed array of seven Yb-doped single-mode fiber lasers embedded in a common cladding. The measured slope efficiency, greater than 65%, was achieved by clad-pumping from one end of the fiber. A theoretical model is established to provide a physical interpretation of the measured far field radiation patterns.

Characteristics of Q-switched cladding-pumped ytterbium-doped fiber lasers with different high-energy fiber designs

Abstract: We theoretically and experimentally analyze Q-switched cladding pumped ytterbium-doped fiber lasers designed for high pulse energies. We compare the extractable energy from two high-energy fiber designs: (1) single- or few-moded low-NA large mode area (LMA) fibers and (2) large-core multimode fibers, which may incorporate a fiber taper for brightness enhancement. Our results show that the pulse energy is proportional to the effective core area and, therefore, LMA fibers and multimode fibers of comparable core size give comparable results. However, the energy storage in multimode fibers is mostly limited by strong losses due to amplified spontaneous emission (ASE) or even spurious lasing between pulses. The ASE power increases with the number of modes in a fiber. Furthermore, spurious feedback is more difficult to suppress with a higher NA, and Rayleigh back-scattering increases with higher NA, too. These effects are smaller in low-NA LMA fibers, allowing for somewhat higher energy storage. For the LMA fibers, we found that facet damage was a more severe restriction than ASE losses or spurious lasing. With a modified laser cavity, we could avoid facet damage in the LMA fiber, and reached output pulse energies as high as 2.3 mJ, limited by ASE. Theoretical estimates suggest that output pulse energies around 10 mJ are feasible with a larger core fiber, while maintaining a good beam quality.

Miniature all-fiber devices based on CO(2) laser microstructuring of tapered fibers.

Abstract: A focused carbon dioxide laser beam is used to microstructure fibers that have already been narrowed by conventional fiber tapering. We describe three new miniature devices made with this technique: a fused fiber microcoupler with an interaction length of 200 μm, a long-period grating made from a periodic chain of microtapers, and a new type of prolate whispering-gallery mode microcavity.

A tunable, femtosecond pulse source operating in the range 1.06-1.33 microns based on an Yb doped holey fiber amplifier

Abstract: Summary form only given. Wavelength tunable femtosecond optical pulse sources have applications in areas as diverse as ultrafast spectroscopy, materials processing, optoelectronics, nonlinear optics and optical chemistry. In the past, such sources have been available only in limited wavelength ranges and were realized using solid state lasers with complex, high precision cavities. More recently, the soliton self frequency shift (SSFS) in silica fibers has been exploited to obtain tunable femtosecond pulses; tuning from 1.55-2.2 /spl mu/m was previously reported in conventional silica fiber, and tuning from 1.3-1.6 /spl mu/m has been demonstrated using tapered microstructured fiber. Here we report what we believe is the first demonstration of a continuously tunable soliton source in the wavelength range 1.06-1.33 /spl mu/m, a wavelength range that is difficult to access using conventional solid state laser technology. The system is based on diode pumped Yb/sup 3+/ doped silica fiber components, and operates at mW average input power levels in a 4.7 m length of fiber.

Efficient neodymium-doped glass-ceramic fiber laser and amplifier.

Abstract: We report an efficient glass-ceramic fiber laser and show that its slope efficiency (~30%) is not compromised by the presence of Nd-doped fluoride crystals embedded within the core of the single-mode optical fiber. In contrast, the spectroscopy (fluorescence and gain spectrum) of the Nd(3+) ions is dramatically changed by the ceramming process, an indication of strong partitioning of the rare-earth ions into the CdF(2):PbF(2):YF(3) crystal environment. The enormous potential for a new range of optical devices based on transparent glass-ceramic materials is highlighted.

Yb:YAG and Nd:YAG edge-pumped slab lasers.

Abstract: Experimental demonstrations of two edge-pumped zigzag slab lasers are presented. The Nd:YAG slab laser generated 127 W of multimode output power with 300W of pump power. Preliminary results with a Yb:YAG slab produced 46 W of output power with 315W of pump power. The edge-pumped slab design permits symmetric conduction cooling and efficient pump absorption and accepts large-numerical-aperture pump sources.

Large-scale multiplexing of interferometric fiber-optic sensors using TDM and DWDM

Abstract: This paper describes multiplexing schemes for interferometric fiber sensors based on time-division multiplexed and dense wavelength-division multiplexing using optical add/drop multiplexers. The results of an experimental arrangement, which is based on one of the architectures, is also presented. Topics include a discussion of the noise sources in the system, dynamic range, and a characterization of the distributed feedback fiber laser source noise. We show the crosstalk levels in the experimental arrangement to be between -47 and -76 dB depending on the mechanism involved. The multiplexing schemes demonstrate the potential to address at least 192 interferometric sensors through two fibers based on a system with six wavelengths with a phase resolution less than 20 /spl mu/rad//spl radic/Hz. For application to sonar arrays, our analysis has shown that hydrophones multiplexed in this type of architecture would achieve ambient acoustic noise-limited pressure resolution with an in-water dynamic range up to 135 dB at frequencies up to 10 kHz. In general, these architectures would find application in systems requiring very large numbers of sensors with a minimum of telemetry cabling required.

Residual stress relaxation in the core of optical fiber by CO 2 laser irradiation

Abstract: We observed residual stress relaxation by CO2 laser irradiation in the cores of optical fibers by direct stress measurement. It was demonstrated that the mechanical stress was fully relaxed by CO2 laser irradiation and that the remaining stress in the core was thermal stress that was due to a mismatch of the thermal expansion coefficients of the fiber core and cladding. The net core stresses after relaxation were 17, 68, and 203 MPa in Ge–B-codoped fibers drawn at 0.53, 1.38, and 3.48 N, respectively. Changes in the refractive indices of the cores as a result of residual stress relaxation were also estimated.

Mode-locked multi-mode fiber laser pulse source

Abstract: A laser utilizes a cavity design which allows the stable generation of high peak power pulses from mode-locked multi-mode fiber lasers, greatly extending the peak power limits of conventional mode-locked single-mode fiber lasers. Mode-locking may be induced by insertion of a saturable absorber into the cavity and by inserting one or more mode-filters to ensure the oscillation of the fundamental mode in the multi-mode fiber. The probability of damage of the absorber may be minimized by the insertion of an additional semiconductor optical power limiter into the cavity.

Experimental and theoretical study of linewidth narrowing in Brillouin fiber ring lasers

Abstract: In Brillouin fiber lasers, the phase fluctuations of the pump laser are transferred to the emitted Stokes field after being strongly reduced. The result is a linewidth narrowing that we study both experimentally and theoretically. We derive simple expressions to connect the linewidths of the waves interacting in the fiber, and we show that the magnitude of the narrowing effect depends only on the acoustic damping rate and the cavity loss rate. We successfully compare these theoretical predictions with experimental results obtained by recording the response of a Brillouin fiber ring laser to frequency modulation of the pump field.

Widely Broadened Super Continuum Generation Using Highly Nonlinear Dispersion Shifted Fibers and Femtosecond Fiber Laser

Abstract: 1.25–1.95 µm widely broadened and almost flat super continuum is generated using only 5-m-long polarization maintaining highly nonlinear dispersion shifted fiber (PM-HN-DSF) and passively mode-locked Er-doped fiber laser. When the fiber length is 200 m, although there is a large depression around 1.5 µm, the optical spectra are widely broadened from 1.1 to 2.1 µm. The temporal distributions of the spectral components in the super continuum are observed using the technique of cross correlation frequency resolved optical gating. The initial generation process of the super continuum is directly observed.

Theory and numerical simulation of nth-order cascaded Raman fiber lasers

Abstract: Using the classical treatment of the stimulated Raman-scattering process, we use a theoretical model to simulate the operation of an nth-order cascaded Raman fiber laser. We introduce the partial differential equations employed to describe the propagation and time dependence of the forward and reverse-propagating fields of an nth-order cascaded Raman fiber laser. Under steady-state conditions, these equations form the well-known system of first-order, nonlinear boundary-value ordinary differential equations, with separated boundary conditions. We solve this system of equations numerically with the use of mono-implicit Runge–Kutta methods within a defect-control framework. We consider cascaded Raman fiber lasers of orders 2 through 5 and examine the parameters that influence the operation of these devices. We also provide preliminary results on the investigation of a time-dependent model in which the pump power is assumed to vary periodically with time. The associated system of first-order, hyperbolic, partial differential equations is treated by employing a transverse method-of-lines algorithm; the time derivatives are discretized with a finite-difference scheme, yielding a large system of boundary-value ordinary differential equations. We establish that for sinusoidal modulation of the pump the Stokes cavity modes exhibit antiphase dynamics typical of a system of locally coupled nonlinear oscillators.

Fiber-coupled microsphere laser

Abstract: A fiber-coupled laser based on a whispering-gallery-mode resonator formed of a laser gain medium and an angle-polished fiber coupler.

Ultrashort-pulse source with controllable multiple-wavelength output

Abstract: A multiple-wavelength ultrashort-pulse laser system includes a laser generator producing ultrashort pulses at a fixed wavelength, and at least one and preferably a plurality of wavelength-conversion channels. Preferably, a fiber laser system is used for generating single-wavelength, ultrashort pulses. An optical split switch matrix directs the pulses from the laser generator into at least one of the wavelength conversion channels. An optical combining switch matrix is disposed downstream of the wavelength-conversion channels and combines outputs from separate wavelength-conversion channels into a single output channel. Preferably, waveguides formed in a ferroelectric substrate by titanium indiffusion (TI) and/or proton exchange (PE) form the wavelength-conversion channels and the splitting and combining matrices. Use of the waveguide allows efficient optical parametric generation to occur in the wavelength-conversion channels at pulse energies achievable with a mode-locked laser source. The multiple-wavelength laser system can replace a plurality of different, single-wavelength laser systems. One particular application for the system is a multi-photon microscope, where the ability to select the ultrashort-signal wavelength of the laser source accommodates any single fluorescent dye or several fluorescent dyes simultaneously. In its simplest form, the system can be used to convert the laser wavelength to a more favorable wavelength. For example, pulses generated at 1.55 μm by a mode-locked erbium fiber laser can be converted to 1.3 μm for use in optical coherence tomography or to 1.04-1.12 μm for amplification by a Yterbium amplifier, allowing amplification of pulses which can be used in a display, printing or machining system.

Fiber-laser-based wavelength-division multiplexed fiber Bragg grating sensor system

Abstract: A wavelength-division-multiplexing technique for interrogating 10-cascaded fiber Bragg grating sensing elements based on a ring-compounded-cavity fiber laser is reported. A feedback control technique was introduced to a tunable Fabry-Perot filter that tracks the wavelength-shift of the sensor. The sensors were demodulated using an unbalanced scanning Michelson interferometer and a sensitivity of 1.682/spl deg///spl mu//spl epsi/ has been demonstrated.

Erbium 3 /spl mu/m fiber lasers

Abstract: With its recent breakthrough in terms of output power the erbium 3-/spl mu/m fiber laser has become an object of intense scientific research and an increasingly attractive tool for medical applications. The paper reviews the research on the erbium 3-/spl mu/m fiber laser since its first demonstration. Its development is seen in relationship to the early success of the corresponding crystal laser system, to the foundations that were laid by the investigation of its spectroscopy and population mechanisms, and the recent technological developments in related fields.

Anisotropic distributed feedback fiber laser sensor

Abstract: The invention relates to a DFB fiber laser sensor (1). The inventive laser-amplifying fiber (2) has a non-rotational-symmetrical structure so that isotropic pressures p, acoustic waves or chemical substances that can be radially attached to the laser-amplifying fiber (2) can be detected.

Jacketed air-clad cladding pumped ytterbium-doped fibre laser with wide tuning range

Abstract: A tunable cladding-pumped ytterbium-doped fibre laser is presented. An air-clad inner cladding supported by a micro-structured silica mesh inside a silica jacket is used. A measured inner-cladding NA of 0.4 to 0.5 enables efficient pump launch into a 36 /spl mu/m-diameter inner cladding. The small inner cladding area enables tuning from 1010 to 1120 nm.

Injection-seeded terahertz-wave parametric oscillator

Abstract: The narrow linewidth operation of a THz-wave parametric oscillator was achieved through the use of narrow linewidth laser injection. THz-wave parametric oscillation, generated by a LiNbO3 crystal pumped with a single longitudinal mode Q-switched Nd:YAG laser, was injection seeded with a continuous-wave Yb:fiber laser. The measured THz-wave linewidth was 200 MHz, which corresponded to the measurement resolution limit.

Combined phase locking and beam shaping of a multicore fiber laser by structured mirrors

Abstract: We present a novel mirror geometry combining the two features of phase locking and simultaneous beam shaping of the emission of a multicore fiber (MCF) laser. In the experiments we applied a Talbot cavity to a diode-pumped MCF laser with 18 microcores placed on a ring. The feedback mirror consisted of a highly reflecting structure with 18 spokes and a circle in the center deposited on a glass substrate. The spokes increased the discrimination between the supermodes and suppressed independent lasing of the individual emitters. The central dot caused strong diffraction of the output radiation, leading to a shaped beam profile. The output power of the phase-locked MCF laser exceeded 5 W.