85 W Tm/sup 3+/-doped silica fibre laser

An 85 W Tm/sup 3+/-doped silica fibre laser is presented. To the best of the authors' knowledge this is the highest output power achieved by pumping with 793 nm. The slope efficiency was 56%, the threshold 11 W and the output wavelength centred at 2.04 /spl mu/m. The high rate of cross relaxation in this laser provided a quantum efficiency of >130%.     

Semiconductor laser pumping of continuous-wave Pr/sup 3+/-doped ZBLAN fibre laser

Blue semiconductor laser pumped continuous-wave laser oscillation of a Pr-doped ZrF/sub 4/-BaF/sub 2/-LaF/sub 3/-AlF/sub 3/-NaF fibre in the red spectral range is reported for the first time. The pump power is provided by a frequency-doubled optically pumped semiconductor laser system. When pumped with 300 mW at a wavelength of 479.7 nm, the Pr/sup 3+/-laser emitted 94 mW of output power at a wavelength of 635 nm. Threshold pump power and slope efficiency with respect to the incident pump power were determined to be 49.7 mW and 41.5%, respectively.     

Pr/sup 3+/-doped fluoride single-mode fiber laser

Laser oscillation at 1.312 mu m was achieved using a Pr/sup 3+/-doped fluoride single-mode fiber laser pumped at 1.017 mu m. The operation of a rare-earth-doped fiber laser at 1.31 mu m, which is one of the central wavelengths in conventional optical telecommunication trunk line systems, was demonstrated for the first time using Pr/sup 3+/ ion as an active ion. The laser cavity consists of a mirror and a cleaved fiber facet used as an output mirror. The maximum output power, threshold pump, and slope efficiency are 26 mW, 370 mW, and 9.86%, respectively.<>     

Multiwavelength diode-cladding-pumped Nd/sup 3+/-doped germano-aluminosilicate fiber laser

Simultaneous multiwavelength oscillation at 1060 and 1090 nm has been produced from a free-running Nd/sup 3+/-doped multicomponent silica fiber laser. As a result of co-doping with both Al/sub 2/O/sub 3/ and GeO/sub 2/, the Nd/sup 3+/ ions are situated at separate sites relating to either Al/sup 3+/-rich or Ge/sup 4+/-rich regions of the germano-aluminosilicate glass. The slope efficiency of the combined /spl sim/1-/spl mu/m output was /spl sim/52% (56%) with respect to the launched (absorbed) pump power. The 1060-nm emission reaches threshold first because of the greater number of Nd/sup 3+/ ions that are located at Al/sup 3+/-rich sites. On chopping the pump light the relaxation oscillations relating to the 1090-nm emission are antiphase with the oscillations observed with the 1060-nm emission. A degree of spectral overlap exists between the fluorescence emitted from Nd/sup 3+/ ions located at each site. Power equalization (to /spl sim/1 W each) of the 1060- and 1090-nm emissions was carried out by way of Raman amplification that occurred either internally or externally to the Nd/sup 3+/-doped silica fiber laser.     

Tunable Pr/sup 3+/-Yb/sup 3+/-doped all-fiber upconversion laser

Fiber lasers in the visible spectral range at 603 and 634 nm were demonstrated using upconversion in fluoride Pr/sup 3+/-Yb/sup 3+/-doped fibers and Bragg gratings photoinduced in germanosilicate fibers. Reliable fine tuning of the all-fiber laser over 6.9 at 603 nm has been demonstrated using high strength fiber Bragg gratings.     

Tunable Pr/sup 3+/-doped silica-based fibre laser

The tunability of the Pr/sup 3+/-doped silica-based fibre laser has been investigated. A broad tuning range of 86 nm is obtained for the transition /sup 1/D/sub 2/-/sup 3/F/sub 3,4/ in the band centred at 1048 nm. Factors limiting tunability, and effects of host matrix and broadening mechanisms are discussed.<>     

Tunable Nd/sup 3+/-doped fibre ring laser

A novel tunable all-fibre laser using a Nd/sup 3+/-doped single mode fibre ring resonator is reported. End pumped by an argon laser of 514.5 nm wavelength, the laser threshold was 1.45 mw, and a tuning range of 60 nm is obtained.<>     

High-power multiwavelength Er/sup 3+/-Yb/sup 3+/ codoped double-cladding fiber ring laser

A high-power simultaneous multiwavelength lasing in an Er/sup 3+/-Yb/sup 3+/ codoped double-cladding fiber (EYCDF) ring laser is demonstrated based on a wavelength-dependent filter through spatial mode beating within the multimode fiber section. We have investigated the relationship between the lasing wavelengths and the length of the EYCDFs. The experimental results indicate that both the number of lasing wavelength lines and the spacing between two adjacent lasing lines can be controlled by the changes of the lasing light polarization states.     

Analysis and optimization of Q-switched operation of a Tm/sup 3+/-doped silica fiber laser operating at 2 /spl mu/m

Analysis and operation of a Q-switched Tm/sup 3+/-doped silica fiber laser in the wavelength region of 2 /spl mu/m is described when pumped with a Nd:YAG laser operating at 1.319 /spl mu/m. A large core of 17-/spl mu/m diameter was used to increase the laser gain volume, allowing high pump-power absorption and an output of high pulse energy and peak power. An acoustooptic modulator was used as Q-switching element and operated at repetition rates up to 30 kHz. A maximum peak output power of greater than 4 kW and a pulse duration at full-width at half-maximum of 150 ns has been obtained. This is the first report of high peak-power operation of the thulium-doped silica fiber laser.     

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%.     

Laser diode pumped Pr/sup 3+/-doped and Pr/sup 3+/-Yb/sup 3+/-codoped fluoride fiber amplifiers operating at 1.3 mu m

Both Pr/sup 3+/-doped and Pr/sup 3+/-Yb/sup 3+/-codoped singlemode fibres with high numerical apertures are pumped by laser diodes with InGaAs/GaAs strained quantum well structures. A net gain of 5.2 dB is obtained from Pr/sup 3+/-doped fluoride fibre pumped by laser diodes operating at 1.1017 mu m and a net gain of 3.2 dB is obtained from Pr/sup 3+/-Yb/sup 3+/-codoped fibre pumped by laser diodes operating at 0.98 mu m. The pumping efficiency difference between Pr/sup 3+/-doped and Pr/sup 3+/-Yb/sup 3+/-codoped fibre is discussed.<>     

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.     

Simultaneous operation of a Raman fiber amplifier and laser pumped by a dual-wavelength Nd/sup 3+/-doped fiber laser

This paper presents an experimental study on the dynamics of Raman fiber lasers that use highly GeO/sub 2/-doped fibers as an active medium and a dual-wavelength (1060 and 1090 nm) Nd/sup 3+/-doped fiber laser as a pump source. The 1090-nm pump wavelength is located within the SiO/sub 2/ Raman gain spectrum relating to the 1060-nm pump wavelength, and competition is observed between Raman amplification of the 1090-nm emission with the 1060-nm emission used as the pump source and Raman lasing, which is independent of the 1090-nm amplification and which is also uses the 1060-nm emission as the pump source. Several pump configurations have been demonstrated to generate specific Stokes emissions generated through Raman lasing or amplification. Changing the gain-to-loss ratio by introducing intracavity loss of Raman emissions or increasing the Raman fiber length within each configuration can force either Raman amplification or lasing to dominate. The maximum slope efficiency as a function of the launched pump power was /spl sim/55% with a total output power of 1.6 W produced. A red shift of both the pump and the Stokes wavelengths is experimentally observed when the launched diode pump power is scaled up.     

Proposal for an Er/sup 3+/-doped chalcogenide glass fiber upconversion laser operating at 980 nm and pumped at 1480 nm

We propose a novel fiber upconversion laser operating at 980 mn and pumped at 1480 nm, which will allow remote optical pumping of erbium-doped optical amplifiers. From the measured spectroscopy, we show Er/sup 3+/-doped gallium lanthanum sulphide glass to be a potential host for such a 1480-nm/980-nm upconversion laser. The small-signal gain is analyzed numerically and the lasing possibilities are discussed.     

Modeling high-power Er/sup 3+/-Yb/sup 3+/ codoped fiber lasers

High-power cladding-pumped Er/sup 3+/-Yb/sup 3+/ codoped fiber lasers (EYDFL) are analyzed with a detailed rate-equations model that takes into account the energy transfer between Yb/sup 3+/ and Er/sup 3+/. Examples of EYDFL with distributed Bragg reflector (DBR) mirrors at both fiber ends are demonstrated. Approximate quasi-analytical solutions to the rate equations show good agreement with the exact numerical solutions for practical operating conditions. An "optimum design" of the laser is discussed in relation to the fiber length that maximizes the output power.     

Concentration-dependent upconversion in Er/sup 3+/-doped fiber amplifiers: Experiments and modeling

Eight different fibers were studied to examine upconversion as a function of erbium concentration below 1000 ppm by weight. These experiments and a computer model of two-particle upconversion made it possible to estimate the upconversion coefficient used in a rate-equation model. A strong correlation was found between amplification reduction and parasitic upconversion in fibers with both Ge- and Ge/Al/P-cores when the erbium-doping concentration is in the range 70-840 ppm by weight. When plotting maximum amplification versus the 980 luminescence on a logarithmic scale, the slope was approximately -2 irrespective of the host material. The validity of the assumed two-particle upconversion model up to 4 mW of pump power is shown.<>     

Optimum parameter design of Er/sup 3+/-doped fiber for optical amplifiers

The parameters of Er/sup 3+/-doped fiber which optimize the signal gain of a fiber amplifier pumped by a 1.48- mu m laser diode are theoretically determined using the rate equation for a three-level laser system. The basic parameters specified are the relative-index difference and the cutoff wavelength. The optimum cutoff wavelength of a completely Er/sup 3+/-doped core fiber with a step-index profile is 0.8 mu m regardless of the value of the relative-index difference. The optimum cutoff wavelength depends on the Er/sup 3+/-doped area radius.<>     

Pr/sup 3+/-doped fluoride fiber amplifier module pumped by a fiber coupled master oscillator/power amplifier laser diode

We constructed the first Pr/sup 3+/-doped fluoride fiber amplifier (PDFA) module pumped by a fiber-coupled master oscillator/power amplifier laser diode (MOPA-LD) operating at 1.017 /spl mu/m. The maximum signal gain and noise figure were 30.5 and 5.5 dB, respectively. An output power of 18 dBm was achieved at an input signal power of 0 dBm. Furthermore, we showed that the use of MOPA-LD pumping, rather than conventional Nd-YLF laser pumping, makes it possible to halve the length of the Pr/sup 3+/-doped fluoride required in the amplifier module and also allows a broader spectral bandwidth to be achieved.     

Efficient upconversion pumping at 1.064 mu m Tm/sup 3+/-doped fluoride fibre laser operating around 1.47 mu m

1.064 mu m upconversion pumping was used to operate a highly efficient CW and Q-switched thulium (Tm/sup 3+/)-doped fluoride fibre laser at around 1.47 mu m. The maximum CW output power was 100 mW for a launched pump power of 570 mW. The threshold power was 200 mW, the slope efficiency 27% and the wavelength width 20 nm. A peak power of 70 W was generated for Q-switching at a launched pump power of 300 mW.<>