Brillouin fibre laser enhanced by Raman amplification

A multiple-wavelength Brillouin fibre laser is demonstrated, with channel spacings of /spl sim/10.5 GHz, using Raman amplification in dispersion-shifted optical fibre. More than 20 frequency lines with /spl sim/2 kHz linewidths are obtained using a 14.5 km length of fibre and a 1.3 MHz linewidth Brillouin pump. Gain depletion due to amplified spontaneous emission limits the total number of cascaded Brillouin lines. At high Raman pump powers, the laser produces a pulse train at the repetition rate corresponding to the cavity round-trip time.     

Spacing-tunable multiwavelength fibre laser

A novel spacing-tunable multiwavelength fibre laser is proposed and demonstrated. A spacing-tunable comb filter consisting of polarisers and a polarisation maintaining fibre (PMF) was used. By changing the pressure position on the PMF, the wavelength spacing can be controlled. 1.46 nm-spaced nine wavelengths and 0.73 nm-spaced 14 wavelengths, when the pressure point was 4 and 8 m, respectively, has been demonstrated     

Experimental characterisation of Raman gain efficiency of holey fibre

The Raman gain efficiency of a 2.3 /spl mu/m-core-diameter holey fibre was measured using three different techniques. A /spl sim/4.65/spl times/10/sup -3/ W/sup -1/ m/sup -1/ efficiency is obtained by all techniques with mismatches lying within the estimated errors. It is shown that the high efficiency is due to small mode-field diameter of the holey fibre, as expected. The use of the fibre as a continuous-wave-pumped Raman amplifier is discussed.     

Lasing wavelength and spacing switchable multiwavelength fiber laser from 1510 to 1620 nm

We experimentally demonstrate a flexibly switchable multiwavelength fiber laser with multiple functionalities like a wide tuning range of lasing wavelength, wavelength spacing, and the number of channels simultaneously. The lasing wavelength is controlled in the range from 1510 to 1620 nm based on the effect of nonlinear gain compression of a semiconductor optical amplifier incorporated with an erbium-doped fiber amplifier. The wavelength spacing and the number of channels in the multiwavelength fiber laser are readily controlled by the effective length of polarization-maintaining fiber (PMF) segments in the intracavity PMF Lyot-Sagnac filter.     

Compact fully fibre integrated source of 100 fs pulses at 1.1 /spl mu/m based on compression in holey fibre

A simple, compact, fully fibre integrated source of /spl sim/100 fs pulses at a wavelength of 1.1 /spl mu/m is reported. 4 ps pulses at 1063 nm from a modelocked fibre laser were amplified to 23 mW in a ytterbium-doped fibre amplifier and subsequently propagated through 62 m of holey fibre with a zero dispersion wavelength at 1040 nm. Soliton formation, breakup and self frequency shift resulted in the formation of /spl sim/100 fs pulses at 1.1 /spl mu/m. Wavelength tunability from 1113 to 1220 nm is demonstrated.     

Singlemode fibre frequency-modulated continuous-wave Sagnac gyroscope

A singlemode fibre frequency-modulated continuous-wave Sagnac gyroscope is described. The rotation speed of the fibre coil can be determined simultaneously by detecting the phase shift of the beat signal produced by two counter-propagating laser beams in a singlemode fibre coil. A resolution of 0.02/spl deg//s with a 100 m fibre coil has been observed.     

Birefringent fibre frequency-modulated continuous-wave Sagnac gyroscope

A birefringent fibre Sagnac gyroscope is described, which is based on the principle of optical frequency-modulated continuous-wave interference and primarily consists of a single-longitudinal-mode frequency-modulated laser diode and a birefringent fibre coil. The rotation velocity of the fibre coil can be determined simultaneously by detecting the phase shift of the beat signal produced by two counter propagating laser beams in the birefringent fibre coil. A resolution of 0.02/spl deg//s with a 100 m fibre coil has been observed. The advantages and limitation of the gyroscope are discussed.     

Forced pump oscillation at anti-Stokes wavelength of coupled Raman fibre laser resonators

Multi-watt oscillation of a Yb/sup 3+/-doped silica fibre pump laser is demonstrated at two wavelengths when pump-coupled Raman fibre laser resonators are constructed using fibre end reflection and a dielectric mirror, which are common to both the pump and Raman fibre lasers. Using an off-resonant Bragg grating to force the initial oscillation of the Raman fibre laser, pump emission at the anti-Stokes wavelength is demonstrated.     

Helical-core ytterbium-doped fibre laser

An Yb-doped fibre laser with a helical core trajectory in the cladding material has been demonstrated for the first time. The laser yields 350 mW of linearly-polarised, single-spatial-mode output at 1047 nm from a multimode core of diameter, 26 /spl mu/m, and numerical aperture, 0.14, when core-pumped by an Yb:YAG laser at 1030 nm.     

Singly Ho/sup 3+/-doped fluoride fibre laser operating at 2.92 /spl mu/m

A singly Ho/sup 3+/-doped fluoride fibre laser that uses energy transfer upconversion to maintain the population inversion has produced 340 mW at 2.92 /spl mu/m. The /spl sim/1100 nm output from a diode-cladding-pumped Yb/sup 3+/-doped silica fibre laser was used as the pump source and a maximum slope efficiency of 5% was obtained.     

210 mW 2.84 /spl mu/m Ho/sup 3+/, Pr/sup 3+/-doped fluoride fibre laser

210 mW of unsaturated continuous-wave output from a Ho/sup 3+/, Pr/sup 3+/-doped fluoride fibre laser is demonstrated using the /spl sim/1100 nm output from a free-running diode-cladding-pumped Yb/sup 3+/-doped silica fibre laser as the pump source. A slope efficiency of 3.2% and an output wavelength of 2.84 /spl mu/m are obtained.     

High-power cascaded Raman fibre laser using phosphosilicate fibre

A 13.2 W second cascade phosphosilicate cascaded Raman fibre using a 450 m phosphosilicate singlemode optical fibre is demonstrated. The lasing wavelength is 1539 nm and the conversion efficiency is 32.5%. This is the highest output power ever reported from a cascaded Raman fibre laser in the 1400-1600 nm range.     

High-power, high-brightness, mJ Q-switched ytterbium-doped fibre laser

A simple diode-pumped, Q-switched fibre laser is reported based on large mode area ytterbium-doped fibre capable of producing pulses with a high beam quality (M/sup 2/=1.1), a duration of /spl sim/40 ns and energies as high as 1.2 mJ at a repetition rate of 10 kHz. This combination of desirable beam qualities makes the source attractive for a range of industrial applications currently serviced by conventional bulk crystal/glass based Q-switched laser systems.     

810 W continuous-wave and single-transverse-mode fibre laser using 20 /spl mu/m core Yb-doped double-clad fibre

It is shown that continuous-wave kW-power fibre lasers can be built using double-clad fibres with relatively small cores. 810 W in a single-transverse-mode output (M/sup 2/=1.27) is demonstrated experimentally with 20 /spl mu/m core low-NA (NA=0.06) Yb-doped double-clad fibre. A laser numerical model matches experimental results and predicts scalability of achievable powers into a multi-kW range.     

Characterisation of a fibre Raman oscillator using fibre grating reflectors

We have constructed a completely integrated fibre Raman oscillator using two fibre grating reflectors. This was synchronously mode-locked using a CW mode-locked Nd:YAG laser operating at 1.06?m. Spectral and temporal characteristics of the Raman oscillator are presented.     

1.47 /spl mu/m Tm/sup 3+/:ZBLAN fibre laser pumped at 1.064 /spl mu/m

A large core area (1257 /spl mu/m/sup 2/) Tm/sup 3+/-doped ZBLAN fibre laser operated at 1.47 /spl mu/m is demonstrated. The pump source is a Nd:YAG laser operated at 1.064 /spl mu/m. A laser output power of 1.56 W continuous wave was obtained for 5.2 W of launched pump power. The slope efficiency with respect to the launched pump power was measured to be 33%.     

High-power broadly tunable Ho/sup 3+/-doped silica fibre laser

Tuning of the 2.1 /spl mu/m Ho/sup 3+/-doped silica fibre laser is demonstrated for the first time. The /sup 5/I/sub 7//spl rarr//sup 5/I/sub 8/ transition provides tuning over 144 nm, from 2019 to 2163 nm, and a maximum pump-limited output power of 1.58 W at 2100 nm was produced.     

Switchable dual-wavelength Raman erbium-doped fibre laser

A fibre Bragg grating feedback fibre laser with both Raman and erbium-doped fibre pumps is proposed. Dual-wavelength switching is achieved by controlling the power of the Raman pump. The characteristics of the dual-wavelength switching are studied experimentally, and the mechanism is explained physically.     

Ytterbium-doped large-core fibre laser with 1 kW of continuous-wave output power

A ytterbium-doped fibre laser with up to 1 kW of continuous-wave output power at 1.09 /spl mu/m with a slope efficiency of 80% and a good beam quality (M/sup 2/=3.4) is reported. The fibre was pumped by two diode-stack sources launched through opposite ends. No undesirable roll-over was observed in output power with increasing pump power.