Characteristics of Cladding-Pumped Short Er3+/Yb3+ Codoped Single Mode Phosphate Glass Fibre

We experimentally investigate the laser characteristics of a series of short pieces of newly-developed Er³⁺/Yb³⁺ codoped single mode phosphate glass fibres via the cladding pump of a 976nm multimode laser diode. A stablecontinuous-wave single transverse mode laser with over 85mW at 1553nm is generated from a 5.5-cm-long active fibre. Single mode laser output power per unit length is up to 15mW/cm. Moreover, the slope efficiency is 11.8% when the pump power is below 940mW and the 3dB linewidth is 0.06nm at the maximum pump power. The numerical simulation results show that the laser emission slope efficiency can exceed 20% by means of increasing the coupling efficiency of the pump to the fibre core further.     

Q-Switched Large-Mode-Area Yb-Doped Fibre Laser Using GaAs as Saturable Absorber

A passive Q-switched large-mode-area Yb-doped fibre laser is demonstrated using a GaAs wafer as the saturable absorber. A high Yb doping concentration double-clad fibre with a core diameter of 30μm and a numerical aperture of 0.07 is used to increase the laser gain volume, permitting greater energy storage and higher output power than conventional fibres. The maximum average output power is 7.2W at 1080nm wavelength, with the shortest pulse duration of 580ns and the highest peak power of 161W when the laser is pumped with a 25W diode laser operating at 976nm. The repetition rate increases with the pump power linearly and the highest repetition rate of 77kHz is obtained in the experiment.     

Polarization-resolved analysis of the characteristics of a Raman laser made with a polarization maintaining fiber

We derive a simple model describing steady characteristics of Raman fiber lasers made with polarization maintaining fibers. We show both theoretically and experimentally that this kind of laser simply consists of two independent Raman lasers linearly polarized along the fiber birefringence axes. The output power characteristics of the laser are shown not to be influenced by optical Kerr effect. Finally, we use our model to propose answers to questions recently raised about efficiency of Raman lasers made with polarization maintaining fibers.     

All-fiber actively Q-switched Yb-doped laser

An all-fiber actively Q-switched Yb-doped laser is presented. Q-switching is performed by modulating a fiber Bragg grating via a magnetostrictive rod which is fixed to the fiber at the position of the grating. By exposing the rod to a changing magnetic field, the rod is stretched and relaxed causing the Bragg wavelength of the grating to shift and thereby changes the Q-factor of the cavity. Using Yb-doped fiber, pulses at 1052 nm are obtained at repetition rates from 1 to 200 kHz. At 75 kHz, 0.5 μJ pulses with peak powers of 3 W can be produced when 180 mW of pump power is applied. To the knowledge of the authors, this is the first all-fiber actively Q-switched Yb-doped laser presented to date.     

Colliding-pulse harmonically mode-locked fiber laser

A Fabry–Perot semiconductor saturable absorber has been implemented in a colliding pulse configuration for stabilizing a harmonically mode-locked fiber laser. An environmentally stable CPM design is shown to enhance supermode suppression. Received: 24 October 2000 / Revised version: 28 November 2000 / Published online: 9 February 2001     

A Continuously Tunable Erbium-Doped Fibre Laser Using Tunable Fibre Bragg Gratings and Optical Circulator

A continuously tunable erbium-doped fibre laser （TEDFL） based on tunable fibre Bragger grating （TFBG） and a three-port optical circulator （OC） is proposed and demonstrated. The OC acts as a 100%-reflective mirror. A strain-induced uniform fibre Bragger grating （FBG） which functions as a partial-reflecting mirror is implemented in the linear cavity. By applying axial strain onto the TFBG, a continuously tunable lazing output can be realized. The wavelength tuning range covers approximately 7.00nm in C band （from 1543.6161 to 1550.3307nm）. The side mode suppression ratio （SMSR） is better than 50 dB, and the 3 dB bandwidth of the laser is less than 0.01 nm. Moreover, an array waveguide grating （AWG） is inserted into the cavity for wavelength preselecting, and a 50 km transmission experiment was performed using our TEDFL at a 10 Gb/s modulation rate.     

2-GHz passive harmonically mode-locked Yb-doped double-clad fiber laser

We report passive harmonic mode locking of a high-power Yb-doped double-clad fiber laser. 680-fs, 48-pJ pulses are emitted at the repetition rate of 2.13 GHz, while the free spectral range of the cavity is 23.4 MHz. Results indicate a supermode suppression of more than 25 dB.     

Side-pumped fiber laser

A neodymium-doped side-pumped double-clad fiber laser operating at 1.06 µm is described. We report here, what is, to our knowledge, the first exclusively repetitive side-pumping scheme with two monomode laser diodes. Side-pumping has been realized by prism-fiber couplers. A pump-light-loss analysis at the pump positions has been performed. An output power of 13.5 mW is obtained with both diode lasers. The highest slope efficiency of 66% with respect to absorbed pump power at 809 nm is achieved when pumping with only one diode.     

Doppler velocimetry using self-mixing effect in a short Er–Yb-doped phosphate glass fiber laser

Accurate and highly sensitive speed measurements have been successfully demonstrated by the optical feedback velocimetry technique using the self-mixing modulation effect in a double-clad Er–Yb-doped fiber laser. The sensitivity to back-scattered light has been investigated regarding the Doppler frequency shift or the target distance, and it has been shown that the velocimeter is still sensitive to a target located at 20 m and for speeds as high as 13 m s^–1.     

Diode-pumped Cr:LiCAF fs regenerative amplifier system seeded by an Er-doped mode-locked fiber laser

A fs regenerative amplifier based on Cr:LiCAF is demonstrated for the first time. With direct diode pumping, 8 μJ of pulse energy are obtained directly from the amplifier. When seeded by an Er-doped fiber laser, the amplified seed pulses are compressed down to 252 fs, limited by residual net third-order dispersion of the compression gratings and intracavity elements. Pulse broadening due to second- and third-order dispersion is theoretically investigated and compared to experimental results. Dispersion generated by the geometrical cavity arrangement is measured experimentally. Received: 19 November 2001 / Revised version: 28 January 2002 / Published online: 14 March 2002