62 research outputs found

    Q-switched neodymium-doped phosphate glass fibre lasers

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    The operation of a short-pulse, Q-switched, neodymium-doped fiber laser operating at 1.054µm is described experimentally and theoretically. The laser is efficiently pumped with a single-stripe AlGaAs laser diode and emits &gt;1kW pulses. It is seen that due to high gain, short pulses with high energy extraction efficiency can be obtained. The feature of broad emission lines associated with rare-earth-doped glasses is exploited to demonstrate tunable, Q-switched operation over a 40 nm tuning range. <br/

    Spectroscopic and lasing characteristics of samarium-doped glass fibre

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    The fluorescence spectra of trivalent samarium doped glass fibres are described. In silica glass Sm3+ has a narrow fluorescence of 2.2 nm f.w.h.m. at a wavelength of 650 nm The influence of fluorescence line narrowing and large external electric fields on this line is reported. Visible laser emission is obtained at this wavelength when the fibre is pumped in a Fabry Perot cavity. The performance of the laser in continuous, Q-switched and self mode-locked operation is described. The basic theory of self-mode-locking is presented

    Absorption-emission cross-section ratio for Er<sup>3+</sup> doped fibres at 1.5µm

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    The ratio of absorption to emission cross-section is determined for Er3+ doped fibres. This parameter, essential in modelling optical amplifiers, is found to be significantly different from previously published values. Reasons for this are discussed

    Efficient diode-pumped single-frequency erbium:ytterbium fibre laser

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    We report a 7.6-mW single-frequency fiber laser operating at 1545 nm, using for the first time an Er3+:Yb3+ doped fiber and a fiber grating output coupler. The laser did not exhibit self-pulsation, which is a typical problem in short three-level fiber lasers, and had a relative intensity noise (RIN) level below -145.5 dB/Hz at frequencies above 10 MHz. The linewidth of the laser was limited by the relaxation oscillation sidebands in the optical spectrum and was typically less than 1 MHz. <br/

    Quantum well devices for mode-locking fibre lasers

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    The generation of picosecond duration pulses in the 1.55 micron wavelength region is of considerable interest for applications related to telecommunications. In the 1.06 micron region, picosecond pulses are useful for spectroscopy and the electro-optic sampling of high speed integrated circuits [I]. Passive mode-locking of fibre lasers using multiple quantum well (MQW) material can provide optical pulses with picosecond durations in both these wavelength regions. The optical confinement and long lengths available, give doped fibre lasers high gain together with flexibility in physical configuration. The use of QWs with light incident perpendicular to the epitaxial layers, as passive saturable absorbers to mode-lock these lasers, is attractive because of their polarisation insensitivity and the wide range of wavelengths available. The semiconductor sample operating wavelength is governed by the materials, their compositions and dimensions used. In fibre, gain is provided in the 1.55 micron region by doping with Erbium whilst Neodymium is used for operation in the 1.06 micron region. By integrating the saturable absorber and laser-cavity end mirror into a single semiconductor device we have generated picosecond pulses in very simple cavity configurations

    Fibre lasers: a review of devices, techniques and applications

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    SummaryHistory of fibre laser development.Fundamentals and key features of fibre lasers - fibre amplifiers withfeedbackReview of applications and laser wavelengthsContinuous wave laser configurations - Power and spectral characteristicsOther configurationsTunable lasersQ-switched lasersMode-locked lasersSingle-frequency lasersUpconversion lasersSuperfluorescent sourcesSome theorySummar

    Erbium-doped fibre superfluorescent source for the fibre gyroscope

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    The operation of an erbium-doped silica fibre as a superfluorescent source at 1.535 µm pumped at 980nm is reported. The variation of superfluorescent output power with pump power and fibre length is characterised. The spectrum of the superfluorescent emission is seen to be dependent on fibre length, pump power and fibre temperature. However, under certain operating conditions, good spectral stability with pump power and fibre temperature can be obtaine

    Narrow-linewidth and tunable fiber lasers

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    1. Introduction 2. Line-narrowed fiber laser devices Integral fiber reflective Bragg grating lasers Intra-cavity etalon laser 3. Tunable, line narrowed fiber laser devices Ring lasers using wavelength selective couplers Tunable lasers using bulk-optic components a) Mechanical tuning b) Electronic tuning 4. Single frequency fiber lasers Integral fiber reflective Bragg grating laser Interferometric cavity laser Injection locked laser Travelling-wave laser 5. Summary Introduction: fiber laser devices based on rare-earth ions incorporated into various glass types have generated considerable interest as narrow linewidth sources, and a number of research groups have published results in this area. Inherent compatibility with optical fiber transmission and sensing media are an obvious attraction for the use of fiber laser devices as sources in fiber communication and sensor applications where narrow linewidths are required. In particular, potential future coherent optical communication systems using wavelength division multiplexing (WDM) will require tunable, narrow-line laser sources. The broad lineshapes associated with rare-earth-doped glass media allow tunable fiber laser sources to be fabricated. The strong optical confinement associated with single-mode fiber laser media enables substantial gain to be obtained over a large fraction of the total emission lines, for both 3-level and 4-level transitions, and hence broad tunability is possible. The potential exists therefore for tunable, narrow linewidth and single longitudinal-mode fiber sources which could find wide application in the field of optical fiber communications and sensors. The ability to convert emission from laser diode pump sources which can be of low modal and temporal quality into highly coherent, low-noise laser emission is an attractive feature of rare-earth lasers in general. The ultimate aim of the development of narrow linewidth fiber laser devices is to provide rugged and stable narrow linewidth or single frequency sources, pumped by a semiconductor laser diode with the capacity of rapidly electronic tunability. Also at low cost! A challenging target certainly, although as will be seen in this chapter, all of the above requirements have been addressed to some extent in various fiber laser devices developed to date. The cost issue has yet to be addressed, although the relative ease of fabrication of bulk quantities of fiber laser gain media (see chapter I: Fiber fabrication), along with expected high yields in device fabrication indicate that low cost devices can be expected. A single device offering all of the above characteristics has yet to be developed although considering the relative youth of modem single-mode fiber laser technology, progress in this field to date has been substantial

    An all fibre, diode-pumped recirculating-ring delay line

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    A Nd3+-doped optical fibre is used as an amplifier in a 35 m fibre recirculating delay line to overcome the round trip losses experienced by injected pulses. Dichroic fused-tapered couplers are used to couple light from a semiconductor source into the ring in order to pump the amplifier. Injected pulses have been maintained for more than 300 round trips
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