1,721,012 research outputs found
An all-fibre, diode-pumped, recirculating-ring delay line
No full textA Nd3+-doped optical fibre is used as an amplifier in a 35m 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, to pump the amplifier. Injected pulses have been maintained for more than 300 round trips
Fibre lasers: a review of devices, techniques and applications
No full textSummaryHistory 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
Narrow-linewidth and tunable fiber lasers
No full text1. 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
Theoretical modelling of erbium doped fibre amplifiers with excited state absorption
No full textNumerical solution of a general rate-equation model of an erbium-doped fiber amplifier highlights several important features of the device. A difference in strong-signal gain between copropagating and counterpropagating signal pump schemes in the presence of pump excited-state absorption is predicted, and this is confirmed by experiment. The detriment in the noise figure previously associated with counterpropagating schemes for only small-signal conditions is shown to be similar for strong signals, corresponding to a power-amplifier operating regime. In addition, a correction to the noise figure is given for the limit of a low-gain amplifier
Modelling erbium/ytterbium-doped fibre amplifiers
No full textA rate equation analysis of Er/Yb-doped fibre amplifiers has been performed. It is expected that the analysis will enable optimisation of co-doped fibre designs for particular pump wavelengths
Jones calculus analysis of single-mode fibre Sagnac reflector
No full textIt 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
320mW Nd<sup>3+</sup>-doped single-mode fibre superfluorescent source
No full textSuperfluorescent, SF single-mode Nd3+ doped fiber sources are of interest for us in a number of applications where a high brightness source of low temporal coherence is required. These include sensors such a fiber gyroscopes and medical diagnostic Such sources are similar to fiber lasers, but suppression of round-trip feedback prevent. the formation of discrete longitudinal cavity modes. The amplified spontaneous emission thus maintains a continuous spectrum. By pumping special doubleclad fibers with multistripe diode arrays, powers of up to 80 mW have been achieved. However, the output power is limited by a tendency to lase around line center when the product of the fiber gain and the effective reflection induced by Rayleigh backscattering exceeds unity. In this paper we report a scheme whereby the limitation is overcome by injecting light from a relatively low-power fiber SF seed source into a high-gain fiber amplifier. Using this technique we have demonstrated output power approximately four times that previously reported
Erbium-doped fibre superfluorescent source for the fibre gyroscope
No full textThe 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
Spectral variation of excited state absorption in neodymium doped fibre lasers
No full textThe spectral variation of gain and excited state absorption have been measured for neodymium doped silica fibres co-doped with germania and alumina. The results show that an observed excited state absorption peak at 1300 nm is considerably reduced in the alumina co-doped fiber
Gain and excited state absorption in neodymium doped optical fibre lasers
No full textGain and excited state absorption for a diode pumped Nd3+ doped silica fibre laser have been measured in the wavelength range 900-1400 nm. The results show a strong excited state absorption in the range 1100-1400 nm in addition to gain at 938 & 1088 nm
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