R.G. Smart

Frequency upconversion in Tm- and Yb:Tm-doped silica fibers

Frequency upconversion has been observed and studied in Tm3+-doped and Yb3+-sensitized Tm3+-doped silica fibers. In the singly singly doped fiber upconversion to the blue and UV has been observed under excitation in the red (660 nm) and infra-red (1.064µm). In the co-doped fiber upconversion has also been observed under excitation at around 800-900 nm.

Efficient and tunable operation of a Tm-doped fibre laser

Abstract We report on improved performance from a silica based thulium doped fibre laser. Under excitation at 810 nm this system has demonstrated a near theoretical maximum slope efficiency of 36% (84% photon conversion efficiency), corresponding t mW of laser output power at 1900 nm for 167 mW of absorbed power. In addition we have used a birefringent filter to continuously tune the laser over a range of 276 nm, from 1780 to 2056 nm.

An Ytterbium-doped Monomode Fibre Laser: Broadly Tunable Operation from 1·010 μm to 1·162 μm and Three-level Operation at 974 Nm

Abstract Continuous-wave laser action has been observed from an ytterbium-doped monomode fibre laser on the three-level transition at 974 nm and on the four-level transition at 1036 nm with slope efficiencies of 67% and 77% respectively, with respect to absorbed power. Tuning behaviour is described, in which polarisation control by means of fibre loops has allowed smooth continuous tuning from 1·010 μm to 1·162 μm.

CW room temperature operation of praseodymium-doped fluorozirconate glass fibre lasers in the blue-green, green and red spectral regions

Abstract We report room temperature, continuous-wave oscillation of Pr3+-doped fluorozirconate fibre lasers at around 491 nm, 520 nm, 605 nm, 635 nm and 715 nm. An output power of 250 mW has been obtained 635 nm for 800 mW of pump power from an argon ion laser operating at 476.5 nm. Tunable operation of the red transitions has been investigated, with output powers in excess of 30 mW being obtained. Q-switched pulses of 75 ns (fwhm) and 20 W peak power at 635 nm have also been generated.

Measurements of fibre laser losses via relaxation oscillations

Abstract We describe a simple method for measuring fibre laser losses. The method is based on including relaxation oscillations by modulating the laser gain. From the oscillation frequency and known fibre parameters a loss figure can be extracted. Loss measurements performed on a Nd-doped fibre laser are presented.

Thulium doped fluorozirconate fibre lasers

Pumping of thulium-doped fluorozirconate fibre lasers at wavelengths available from semiconductor diodes around 790 nm has enabled continuous wave laser operation at 806 nm, 1.47 μm, 1.97 μm and 2.3 μm, many of which may occur simultaneously. The performance of these laser transitions, including diode-pumped operation of the 3H4-3H6 transition at 1.97 μm, is discussed.

Efficient superfluorescent emission at 974 nm and 1040 nm from an Yb-doped fiber

Abstract End-pumping of an Yb-doped single-mode fiber has yielded > 10mW and 30 mW of broadband superflourescence at 974 nm and 1040 nm, respectively. Slope efficiencies > 40% have been obtained. Pump wavelength dependent linewidths between 2 nm and 19 nm have been observed.

Theoretical and experimental investigation of a resonantly pumped thulium doped fluorozirconate fiber amplifier at around 810 nm

The potential of thulium-doped fluorozirconate fibers to provide an efficient AlGaAs diode pumped traveling wave amplifier at wavelengths around 810 nm is investigated. The authors present calculations and experimental measurements of the small signal gain when excitation is resonant with the upper laser level, with a view to predicting the upper limits of performance for optimized fiber design. The theoretical treatment involves numerical determination of the evolution of pump and signal power (and hence gain) along the length of the fiber as a function of wavelength, spectral lineshapes and lifetimes, and geometrical factors. Amplification over the range 800-830 nm has been achieved in multimoded fiber with a best observed gain of 22 dB at 806 nm. >

Continuous-wave oscillation of Tm3+ -doped fluorozirconate fibre lasers at around 1.47 μm, 1.9 μm and 2.3 μm when pumped at 790 nm

Abstract Continuous-wave operation of Tm 3+ -doped fluorozirconate fibre lasers at around 1.47 μm, 1.9 μm and 2.3 μm has been demonstrated when pumping at around 790 nm with a Ti: sapphire laser. The efficiency of the 1.9 μm 3 H 4 - 3 H 6 transition was found to be significantly increased by enforcing simultaneous oscillation on the 3 F 4 - 3 H 5 transition at 2.3 μm as this effectively enhances the branching ratio for pumping the 3 H 4 level. An upconversion process leading to blue emission has also been observed. The efficiency of this process is enhanced by more than an order of magnitude as soon as laser oscillation takes place at 2.3 μm, indicating the potential application of manipulating branching ratios via lasing.

Lasing Characteristics Of Ytterbium, Thulium And Other Rare-Earth Doped Silica Based Fibers

We have experimentally studied the lasing characteristics of silica fibers doped with Yb, Tm, Pr and Ho and present a summary of these results.