P.R. Morkel

Absorption and emission cross section of Er/sup 3+/ doped silica fibers

A detailed set of measurements is presented on determining the emission and absorption cross sections of Er/sup 3+/ doped fibers for the /sup 4/I/sub 13/2/ to /sup 4/I/sub 15/2/ transition. Two techniques are employed: the Fuchtbauer-Ladenberg analysis, based on spectroscopic data, and a more direct technique involving optical saturation of the transition. The cross sections, and in particular their ratio, are significantly different for the two techniques. Possible reasons for this are discussed, and it is concluded that the Fuchtbauer-Ladenberg approach is inappropriate in this situation. >

Erbium-doped fiber amplifier with flattened gain spectrum

An optical notch filter was incorporated within the length of all erbium-doped fiber amplifier. Careful choice of the filter characteristics and location made it possible to enhance the amplifier gain at wavelengths around 1550 nm. An amplifier with 27-dB gain and 33-nm bandwidth was demonstrated. The saturation characteristics of the amplifier were uniform across its gain spectrum, making it ideal for wavelength division multiplexed (WDM) application.<<ETX>>

Theoretical modeling of erbium-doped fiber amplifiers with excited-state absorption

Numerical 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 experimen. 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.

Diode-array pumping of Er/sup 3+//Yb/sup 3+/ Co-doped fiber lasers and amplifiers

Single-mode double-clad Er/sup 3+//Yb/sup 3+/ co-doped fibers are shown to be suitable for diode array pumping at around 960 nm. A fiber laser with 96-W output power at 1.53 mu m and a power amplifier exhibiting a small signal gain of 24 dB and a saturated output power of +17 dBm are reported.<<ETX>>

Efficient diode-pumped single-frequency erbium:ytterbium fiber laser

We report a 7.6-mW single-frequency fiber laser operating at 1545 nm, using for the first time an Er/sup 3+/:Yb/sup 3+/ doped fiber and a fiber grating output coupler. The laser did not exhibit self-pulsation, which is a typical problem in short three-level fiber lasers, and had a relative intensity noise (RIN) level below -145.5 dB/Hz at frequencies above 10 MHz. The linewidth of the laser was limited by the relaxation oscillation sidebands in the optical spectrum and was typically less than 1 MHz.<<ETX>>

High-quantum-efficiency Er(3+) fiber lasers pumped at 980 nm.

Significant improvements in the operation of Er(3+)-doped silica fiber lasers operating at wavelengths between 1.5 and 1.6 microm are reported. The use of 980 nm as the pump wavelength provides an output that is limited mainly by the quantum efficiency of the lasing process. It is thus considerably more efficient than previous results using ~810-nm pumping, where excited-state absorption degrades the lasing performance. Operation at three discrete output wavelengths is observed and is accounted for by studying gain across the lasing bandwidth.

Short-pulse, high-power Q-switched fiber laser

A high-power, laser-diode-pumped, Q-switched fiber laser operating at 1.053 mu m which is suitable for use in time-multiplexed fiber sensor applications is described. The laser emits >1-kW pulses at 1.053 mu m with 2-ns duration at up to 1-kHz repetition rates for an adsorbed pump power of only 22 mW at 810 nm. Tunable Q-switched operation over a 40-nm wavelength range has also been demonstrated.<<ETX>>

Passively mode-locked Er/sup 3+/ fiber laser using a semiconductor nonlinear mirror

A nonlinear mirror consisting of an InGaAs/InP multiple-quantum-well saturable absorber integrated with a Bragg reflector stack has been used to passively mode-lock a fiber laser in an extremely simple and advantageous linear-cavity configuration. To date, pulses as short as 7.6 ps have been observed.<<ETX>>

All‐solid‐state subpicosecond passively mode locked erbium‐doped fiber laser

Using a semiconductor saturable absorber, an erbium‐doped fiber laser has been passively mode locked to yield pulses of 840 fs with pulse energies of 0.85 nJ. Stable mode locking at the fundamental roundtrip frequency and also at the second and third harmonic has been achieved.

Q-switched neodymium-doped phosphate glass fiber lasers

The operation of a short-pulse, Q-switched, neodymium-doped fiber laser operating at 1.054 mu m is described experimentally and theoretically. The laser is efficiently pumped with a single-stripe AlGaAs laser diode and emits >1 kW pulses. It is seen that due to high gain short pulses with high energy extraction efficiency can be obtained. The feature of broad emission lines associated with rare-earth-doped glasses is exploited to demonstrate tunable, Q-switched operation over a 40-nm tuning range. >