Showing papers on "Fiber laser published in 2008"

Wideband-tuneable, nanotube mode-locked, fibre laser

Abstract: Ultrashort-pulse lasers with spectral tuning capability have widespread applications in fields such as spectroscopy, biomedical research and telecommunications1–3. Mode-locked fibre lasers are convenient and powerful sources of ultrashort pulses4, and the inclusion of a broadband saturable absorber as a passive optical switch inside the laser cavity may offer tuneability over a range of wavelengths5. Semiconductor saturable absorber mirrors are widely used in fibre lasers4–6, but their operating range is typically limited to a few tens of nanometres7,8, and their fabrication can be challenging in the 1.3–1.5 mm wavelength region used for optical communications9,10. Single-walled carbon nanotubes are excellent saturable absorbers because of their subpicosecond recovery time, low saturation intensity, polarization insensitivity, and mechanical and environmental robustness11–16. Here, we engineer a nanotube–polycarbonate film with a wide bandwidth (>300 nm) around 1.55 mm, and then use it to demonstrate a 2.4 ps Er31-doped fibre laser that is tuneable from 1,518 to 1,558 nm. In principle, different diameters and chiralities of nanotubes could be combined to enable compact, mode-locked fibre lasers that are tuneable over a much broader range of wavelengths than other systems.

Analysis of the scalability of diffraction-limited fiber lasers and amplifiers to high average power

Abstract: We analyze the scalability of diffraction-limited fiber lasers considering thermal, non-linear, damage and pump coupling limits as well as fiber mode field diameter (MFD) restrictions. We derive new general relationships based upon practical considerations. Our analysis shows that if the fiber's MFD could be increased arbitrarily, 36 kW of power could be obtained with diffraction-limited quality from a fiber laser or amplifier. This power limit is determined by thermal and non-linear limits that combine to prevent further power scaling, irrespective of increases in mode size. However, limits to the scaling of the MFD may restrict fiber lasers to lower output powers.

High-energy femtosecond fiber lasers based on pulse propagation at normal dispersion

Abstract: The generation and stable propagation of ultrashort optical pulses tend to be limited by accumulation of excessive nonlinear phase shifts. The limitations are particularly challenging in fiber-based devices, and as a result, short-pulse fiber lasers have lagged behind bulk solid-state lasers in performance. This article will review several new modes of pulse formation and propagation in fiber lasers. These modes exist with large normal cavity dispersion, and so are qualitatively distinct from the soliton-like processes that have been exploited effectively in modern femtosecond lasers but which are also quite limiting. Self-similar evolution can stabilize high-energy pulses in fiber lasers, and this leads to order-of-magnitude increases in performance: fiber lasers that generate 10 nJ pulses of 100 fs duration are now possible. Pulse-shaping based on spectral filtering of a phase-modulated pulse yields similar performance, from lasers that have no intracavity dispersion control. These new modes feature highly-chirped pulses in the laser cavity, and a theoretical framework offers the possibility of unifying our view of normal-dispersion femtosecond lasers. Instruments based on these new pulse-shaping mechanisms offer performance that is comparable to that of solid-state lasers but with the major practical advantages of fiber.

Dissipative solitons in normal-dispersion fiber lasers

Abstract: Mode-locked fiber lasers in which pulse shaping is based on filtering of a frequency-chirped pulse are analyzed with the cubic-quintic Ginzburg-Landau equation. An exact analytical solution produces a variety of temporal and spectral shapes, which have not been observed in any experimental setting to our knowledge. Experiments agree with the theory over a wide range of parameters. The observed pulses balance gain and loss as well as phase modulations, and thus constitute dissipative temporal solitons. The normal-dispersion fiber laser allows systematic exploration of this class of solitons.

Phase-locked generation and field-resolved detection of widely tunable terahertz pulses with amplitudes exceeding 100 MV/cm.

Abstract: Phase-locked terahertz transients with peak electric fields of 108 MV/cm and center frequencies continuously tunable from 10 to 72 THz are generated via difference-frequency mixing of two parametrically amplified pulse trains from a single white-light seed. Free space electro-optic sampling with 8 fs gating pulses from a two-branch Er:fiber laser allows us to monitor all transients directly in the time domain. We identify extreme terahertz nonlinearities in the detector crystal with subcycle resolution.

Mode-locked 1.93 μm thulium fiber laser with a carbon nanotube absorber

Abstract: We report a ring-cavity thulium fiber laser mode locked with a single-wall carbon nanotube absorber used in transmission. A carboxymethyl cellulose polymer film with incorporated carbon nanotubes synthesized by the arc discharge method has an absorption coinciding with in the amplification bandwidth of a Tm-doped fiber. This laser is pumped by an erbium fiber laser at 1.57 μm wavelength and produces a 37 MHz train of mode-locked 1.32 ps pulses at 1.93 μm wavelength with an average output power of 3.4 mW.

Properties of normal-dispersion femtosecond fiber lasers

Abstract: We report a systematic study of all-normal-dispersion mode-locked fiber lasers. Spectral filtering of a chirped pulse in the cavity is a major component of the pulse shaping in these lasers. We identify the nonlinear phase shift accumulated by the pulse, spectral filter bandwidth, and group-velocity dispersion as the key parameters that determine the behavior and properties of these lasers. Trends in the performance as these parameters are varied are summarized. A wide range of pulse shapes and evolutions can occur. Experimental results from Yb-doped all-normal-dispersion fiber lasers agree reasonably well with the results of numerical simulations.

Acousto-Ultrasonic Optical Fiber Sensors: Overview and State-of-the-Art

Abstract: This paper gives a review of acoustic and ultrasonic optical fiber sensors (OFSs). The review covers optical fiber sensing methods for detecting dynamic strain signals, including general sound and acoustic signals, high-frequency signals, i.e., ultrasonic/ultrasound, and other signals such as acoustic emissions, and impact induced dynamic strain. Several optical fiber sensing methods are included, in an attempted to summarize the majority of optical fiber sensing methods used to date. The OFS include single fiber sensors and optical fiber devices, fiber-optic interferometers, and fiber Bragg gratings (FBGs). The single fiber and fiber device sensors include optical fiber couplers, microbend sensors, refraction-based sensors, and other extrinsic intensity sensors. The optical fiber interferometers include Michelson, Mach-Zehnder, Fabry-Perot, Sagnac interferometers, as well as polarization and model interference. The specific applications addressed in this review include optical fiber hydrophones, biomedical sensors, and sensors for nondestructive evaluation and structural health monitoring. Future directions are outlined and proposed for acousto-ultrasonic OFS.

Mid-Infrared Coherent Sources and Applications

Abstract: Preface. I. Crystalline Laser and Nonlinear Optical Materials for the Mid-IR. New Monocrystals with Low Phonon Energy for Mid-IR Lasers L. Isaenko et al.- Orthorombic Crystals of Lithium Thioindate and Selenoindate for Nonlinear Optics in the Mid-IR J-J. Zondy et al.-Quaternary Nonlinear Optical Crystals for the Mid-IR Spectral Range from 5 to 12 Micron V. Petrov et al.-Microstructured Semiconductors for Mid-Infrared Nonlinear Optics P.S. Kuo and M. M. Fejer.- II Sources in the Mid-IR. Progresses in Quantum Cascade Lasers J. Faist et al.- High-Brightness 2.X tm Semiconductor Lasers M. Rattunde et al.- Broadband Mid-Infrared Solid-State Lasers I. Sorokina.- New Regimes of Excitation and Mid-Infrared Lasing of Transition Metal Doped Il-VI Crystals S. Mirov and V. Fedorov.- Advances in Mid-Infrared Fiber Lasers M. Pollnau and S. D. Jackson.-Mid-Infrared Optical Parametric Oscillators and Applications M. Ebrahim-Zadeh.- Mid-Infrared Integrated Optical Parametric Generators and Oscillators with Periodically Poled Ti:LiNbO3 Waveguides S. Orlov et al.-Optical Parametric Generators and Amplifiers V. Pasiskevicius and F.Laurell.-Tunable THz Sources Based on Quasi-Phase-Matched Gaffium Arsenide K. Vodopyanov.- Semiconductor Waveguides for Nonlinear Frequency Conversion L. Lanco et al.-III. Applications. 1. Semiconductor Laser Based Trace Gas Sensor Technology : Recent Advances and Applications F. Tittel et al.-Trace-Gas Analysis with Isotopic Selectivity Using DFG-sources H. Waechterand M. Sigrist.- Photoacoustic Spectroscopy Using Continuous Wave Optical Parametric Oscillators A. K. Y. Ngai et al.-Online Monitoring of Exhaled Breath Using Mid-Infrared Laser Spectroscopy M. Murtz and P.Hering.- Ultrabroadband Solid-State Laser Based Trace Gas Sensoing E. Sorokin.- Medical Applications of Mid-IR Solid-State Lasers R. Steiner.-Opportunities for Mid-IR Sources in Intense-field and Attosecond Physics M. Ivanov et al.-UltrawidebandMid-Infrared Spectroscopy of Semiconductor Nanostructures Th. Muller und K. Unterrainer.-

Miniaturized fiber inline Fabry-Perot interferometer fabricated with a femtosecond laser.

Abstract: We report a miniaturized inline Fabry-Perot interferometer directly fabricated on a single-mode optical fiber with a femtosecond laser. The device had a loss of 16 dB and an interference visibility exceeding 14 dB. The device was tested and survived in high temperatures up to 1100°C. With an accessible cavity and all-glass structure, the new device is attractive for sensing applications in high-temperature harsh environments.

Observation of high-order polarization-locked vector solitons in a fiber laser.

Abstract: We report on the experimental observation of a new type of polarization-locked vector soliton in a passively mode-locked fiber laser. The vector soliton is characterized by the fact that not only are the two orthogonally polarized soliton components phase-locked, but also one of the components has a double-humped intensity profile. Multiple phase-locked high-order vector solitons with identical soliton parameters and harmonic mode locking of the vector solitons were also obtained in the laser. Numerical simulations confirmed the existence of stable high-order vector solitons in the fiber laser.

Efficient Yb laser fibers with low photodarkening by optimization of the core composition

Abstract: We report on photodarkening (PD) investigations at Yb doped fibers with specific variation of the concentrations of the codopants aluminum and phosphorus, measured during cladding pumping at 915 nm. A core composition with equal content of Al and P is most promising to achieve Yb fibers with low PD, high laser efficiency and low numerical aperture of the laser core despite of high codoping. A laser output power of more than 100 W was demonstrated on such a fiber with a slope efficiency of 72%. The correlation of the PD loss with the NIR-excited cooperative luminescence encourages the supposition that cooperative energy transfer from excited Yb(3+) ions to the atomic defect precursors in the core glass enables the formation of color centers in the pump-induced PD process.

Ultra-low repetition rate mode-locked fiber laser with high-energy pulses.

Abstract: This paper reports on the results of research into passively mode-locked fiber laser with a record-setting optical length of the resonant cavity amounting to 3.8 km. Significant elongation of the laser resonator led to more than two orders of magnitude increase in the output pulse energy at the same pump radiation power. At ultra-low (for mode-locked lasers) pulse repetition rate (77 kHz) and pulse duration of 3 ns the energy per pulse reached 3.9 µJ. At this moment this is the highest pulse energy on record generated directly from a mode-locked laser without Q-switching, cavity dumping techniques, or additional optical amplifiers.

Yb: and Nd: mode-locked oscillators and fiber systems incorporated in solid-state short pulse laser systems

Abstract: The invention describes classes of robust fiber laser systems usable as pulse sources for Nd: or Yb: based regenerative amplifiers intended for industrial settings. The invention modifies adapts and incorporates several recent advances in FCPA systems to use as the input source for this new class of regenerative amplifier.

Visible supercontinuum generation in photonic crystal fibers with a 400W continuous wave fiber laser

Abstract: We demonstrate continuous wave supercontinuum generation extending to the visible spectral region by pumping photonic crystal fibers at 1.07 microm with a 400 W single mode, continuous wave, ytterbium fiber laser. The continuum spans over 1300 nm with average powers up to 50 W and spectral power densities over 50 mW/nm. Numerical modeling and understanding of the physical mechanisms has led us to identify the dominant contribution to the short wavelength extension to be trapping and scattering of dispersive waves by high energy solitons.

Visibly “white” light generation in uniform photonic crystal fiber using a microchip laser

Abstract: We report on visibly white supercontinuum generation in photonic crystal fibers using a sub ns pump source at 1064 nm. The spectra extend from below 400 nm to 2450 nm, some 50 nm further into the blue than previously reported spectra. The extra bandwidth which is achieved by a simple modification to the fiber structure gives a higher apparent color temperature and a truly "white" visual appearance. The mechanism for the generation of the deeper blue to ultraviolet frequencies is outlined and our modified fiber is compared with fibers which have been conventionally used for supercontinuum generation.

Distributed Feedback Fiber Laser Strain Sensors

Abstract: The distributed feedback (DFB) fiber laser strain sensor has demonstrated strain resolution comparable to that obtained from high-performance fiber-optic interferometry. This manuscript describes the characteristics and performance of this fiber laser strain sensor and discusses the technological developments necessary to obtain comparable performance from a multiplexed array of laser sensors. The design of the Bragg grating and doped fiber are discussed, where possible providing simplified equations to quantify the relevant design parameters. Techniques based on fiber-optic interferometry to decode the wavelength shifts of the laser are presented and potential noise sources are described. Measurements conducted on a test laser demonstrate the capability of the DFB fiber laser to resolve effective length changes to less than 0.76 fm/Hz1/2 at 2 kHz. The accuracy of the strain measurement, calculated by subtracting the output of two lasers subjected to the same strain, is found to be less than 1%. Issues relating to multiplexing lasers, such as pump power depletion and optical feedback, are described along with methods to maximize the number of lasers serially multiplexed on a single fiber. Finally, the strain transduction mechanism and methods to mount the laser sensor are described. It is shown that for certain applications, the DFB fiber laser sensor provides significant performance benefits when compared with remotely interrogated fiber-optic interferometric sensing techniques.

>1 MW peak power single-mode high-brightness passively Q-switched Nd 3+ :YAG microchip laser

Abstract: A high-brightness diode end-pumped Nd:YAG microchip laser, passively Q-switched by a Cr(4+):YAG saturable absorber (SA), has been developed. The dependences of pulse energy and width were investigated based on theoretical verification to enhance the peak power. As a result, the peak power exceeded 1.2 MW with M(2) = 1.04 and spectrum width Delta lambda < 5.1 pm at a repetition rate of 100 Hz. Brightness of 98 TW/sr x cm(2) was obtained with a supplied average electrical power of 2.3 W. The peak power increased up to 2.1 MW with M(2) = 1.36. Peak power of 1.7 MW was obtained from a 2-cm-diameter x 5-cm-long monolithic laser head.

Ultra‐large effective‐area, higher‐order mode fibers: a new strategy for high‐power lasers

Abstract: This paper describes the physics and properties of a novel optical fiber that would be attractive for building high-power fiber lasers and amplifiers. Instead of propagating light in the fundamental, Gaussian-shaped mode, we describe a fiber in which the signal is forced to travel in a single, desired higher order mode (HOM). This provides for several advantages over the conventional approach, ranging from significantly higher ability to scale mode areas (and hence laser powers) to managing dispersion for ultra-short pulses - a capability that is practically nonexistent in conventional fibers. Particularly interesting is the tact that this approach challenges conventional wisdom, and demonstrates that for applications requiring meter-length fibers (as in high-power lasers), signal stability actually increases with mode order. Using this approach, we demonstrate mode areas exceeding 3200 μm 2 , and propagate signals with negligible mode distortions over up to 50-meter lengths. We describe several pulse propagation experiments in which we test the nonlinear response of this fiber platform, ranging from managing dispersive effects in femtosecond pulse systems, to reducing Brillouin scattering impairments in systems operating with the nanosecond pulses.

Passive mode locking of Yb:KLuW using a single-walled carbon nanotube saturable absorber

Abstract: Mode locking of an Yb-doped bulk laser in the 1 μm spectral range using a single-walled carbon nanotube saturable absorber (SWCNT-SA) is demonstrated for the first time, to our knowledge. Passive mode locking of an Yb:KLuW laser resulted in nearly transform-limited pulses as short as 115 fs at 1048 nm. In addition, the nonlinear response of the SWCNT-SA was measured, yielding a modulation depth of 0.25% and a relaxation time of 750 fs.

All-fiber normal-dispersion femtosecond laser

Abstract: Spectral filtering of a chirped pulse can be a strong pulse-shaping mechanism in all-normal-dispersion femtosecond fiber lasers. We report an implementation of such a laser that employs only fiber-format components. The Yb-doped fiber laser includes a fiber filter, and a saturable absorber based on carbon nanotubes. The laser generates 1.5-ps, 3-nJ pulses that can be dechirped to 250 fs duration outside the cavity.

Preventing photodarkening in ytterbium-doped high power fiber lasers; correlation to the UV-transparency of the core glass

Abstract: Photodarkening experiments are performed on ytterbium-doped silicate glass samples. A strong charge-transfer (CT) absorption band near 230nm in aluminosilicate glass is found to be correlated to the mechanism of induced color center formation. Excitation into the CT-absorption band generates similar color centers as observed in ytterbium-doped fiber lasers under 915nm high power diode pumping. The position of the CT-absorption band is compositional dependent and is shifted to shorter wavelengths in ytterbium doped phosphosilicate glass. Very low levels of photodarkening is observed for the ytterbium doped phosphosilicate glass composition under 915nm high power diode pumping. Possible excitation routes to reach the CT-absorption band under 915nm pumping are discussed.

High power ytterbium-doped rod-type three-level photonic crystal fiber laser.

Abstract: In this paper, we investigate power scalability of ytterbium-doped ultra large core photonic crystal fiber laser operating on the zero-line transition. We first report on an 80 microm core diameter ytterbium-doped rod-type photonic crystal fiber laser emitting up to 94 W in continuous wave regime when operating at 977 nm, which is to our knowledge the highest output power ever achieved from a single-mode solid-state laser operating at this wavelength. Key parameters of ytterbium-doped three-level laser, such as transparency pump intensity, pump absorption saturation, and gain competition between three and four-level laser operation are then discussed in the particular context of high power fiber laser operating at 977 nm.

Long-distance frequency transfer over an urban fiber link using optical phase stabilization

Abstract: We transferred the frequency of an ultra-stable laser over 86 km of urban fiber. The link is composed of two cascaded 43-km fibers connecting two laboratories, LNE-SYRTE and LPL in Paris area. In an effort to realistically demonstrate a link of 172 km without using spooled fiber extensions, we implemented a recirculation loop to double the length of the urban fiber link. The link is fed with a 1542-nm cavity stabilized fiber laser having a sub-Hz linewidth. The fiber-induced phase noise is measured and cancelled with an all fiber-based interferometer using commercial off the shelf pigtailed telecommunication components. The compensated link shows an Allan deviation of a few 10-16 at one second and a few 10-19 at 10,000 seconds.

Multiwavelength fiber laser with fine adjustment, based on nonlinear polarization rotation and birefringence fiber filter.

Abstract: We have proposed and demonstrated a multiwavelength fiber laser based on nonlinear polarization rotation (NPR). The mechanism for stable room-temperature multiwavelength operation contributes to the ability of the intensity-dependent loss in NPR to effectively alleviate mode competition. In addition, through tuning the birefringence fiber filter, the lasing wavelength can be accurately tuned in the free spectrum range of the in-line periodic filter.

All-fiber bidirectional passively mode-locked ring laser.

Abstract: We report the design and operation of a novel all-fiber bidirectional passively mode-locked ring laser. An erbium-doped fiber was chosen as the active element in a ring cavity arrangement. A short segment of a fiber taper embedded in carbon nanotubes/polymer composite, acting as a saturable absorber, was used to enable bidirectional mode locking. The laser generates two stable femtosecond pulse trains in opposite directions. A beat note of about 2 MHz, having a bandwidth of less than 2 kHz, is measured when the pulses propagating in opposite directions are (temporally) overlapped at a photodetector. We believe this device will find important applications in precision rotation sensing.

94 W 980 nm high brightness Yb-doped fiber laser

Abstract: We report on the generation of 94 W continuous wave output power at 980 nm using an Yb-doped fiber laser This is achieved using an ultra large-mode-area rod-type photonic crystal fiber pumped at 915 nm To the best of our knowledge this is the highest output power close to diffraction-limited beam quality (M2 about 22) achieved in this wavelength range from fibers so far The experimental results are supported by detailed numerical simulations that provide a deeper understanding of the laser process, in particular the competition with the 1030 nm emission

Mid-infrared ZnGeP2 parametric oscillator directly pumped by a pulsed 2 microm Tm-doped fiber laser.

Abstract: We have demonstrated what we believe to be the first mid-infrared optical parametric oscillator (OPO) pumped directly by a pulsed Tm-doped fiber laser. The Tm-fiber pump laser produces 30 ns pulses with a repetition rate of 30 kHz at a wavelength of 2 microm. The ZnGeP2 (ZGP) OPO produces 20 ns mid-IR pulses in the 3.4-3.9 microm and 4.1-4.7 microm spectral regions simultaneously. More than 658 mW of mid-IR output power has been generated with a total OPO slope efficiency greater than 35%.

Coherent energy exchange between components of a vector soliton in fiber lasers.

Abstract: We report on the experimental evidence of four wave mixing (FWM) between the two polarization components of a vector soliton formed in a passively mode-locked fiber laser. Extra spectral sidebands with out-of-phase intensity variation between the polarization resolved soliton spectra was firstly observed, which was identified to be caused by the energy exchange between the two soliton polarization components. Other features of the FWM spectral sidebands and the soliton internal FWM were also experimentally investigated and numerically confirmed.

All-polarization-maintaining Er-doped ultrashort-pulse fiber laser using carbon nanotube saturable absorber.

Abstract: We present an all-polarization-maintaining Er-doped ultrashortpulse fiber laser using a single-wall carbon nanotube polyimide nanocomposite saturable absorber. The maximum average power for single-pulse operation is 4.8 mW, and the repetition frequency is 41.3 MHz. Self-start and stable mode-locking operation is achieved. The RF amplitude noise is also examined and it is confirmed that the noise figure is as low as that of a solid-state laser. Using a polarization-maintaining anomalous dispersive fiber, a 314 fs output pulse is compressed to 107 fs via higher-order soliton compression. The peak power of the compressed pulse is up to 1.1 kW.