An ultrafast fiber MOPA was developed which delivered high average power and rapid and continuous tunability over
the range 1035 - 1070 nm. Through FWM in a single PCF, this source generated greater than 30% conversion efficiency
to a narrow linewidth signal with tunability from 720 to 880 nm and a corresponding idler tunable from 1370 to 1880
nm. Generation of tunable signal SHG, signal-pump SFG, pump SHG and pump-idler SFG were demonstrated in a
single angle tuned BBO crystal. The combined system enabled tunability over large portions of the UV, visible and NIR
spectral range from 370 - 1900 nm with a very simple setup. There is scope for power scaling of the source and
extending the wavelength coverage.
We demonstrate a sub-100 fs frequency doubled fiber laser operating at 810 nm. The laser produces 60 mW of average power at a repetition rate of 50 MHz. Extremely low amplitude noise (below 0.1%) and compact size makes this source ideal replacement for low power ultrafast Ti:Spphire lasers.
Ultrafast lasers can be used to produce laser pulses with enormous peak powers and power densities. The very high peak power that can be achieved with femtosecond pulses means that in principle, nonlinear frequency conversion should be very efficient. It should be quite straightforward to use second-harmonic (SHG), third-harmonic (THG) and fourth-harmonic generation (FHG) to produce femtosecond pulses in the near- to deep-ultraviolet. We present results on a mode-locked Yb<sup>3+</sup>-fiber laser operating in the 980 nm spectral band. Such lasers are very attractive as a seed source for generating blue light using SHG. The laser comprised a linear fiber cavity defined by the fiber loop-mirror and the semiconductor saturable-absorber mirror (SESAM) used to self-start the mode-locking. SESAM operating in the 940-1050 nm wavelength-range comprised 26 pairs of AlAs/GaAs quarter-wave layers that form a distributed Bragg reflector with a center wavelength at about 1000 nm. The active region consists of five GaInNAs quantum wells embedded within GaAs layers. With proper alignment of the laser cavity, the laser was self-starting for pump powers above 50 mW at 915 nm. The output mode-locked pulse train at about 980 nm had an output power of 3 mW, a repetition rate of 30 MHz and pulse duration of 2.3 ps. The pulse spectrum exhibited soliton sidebands at all pump powers, confirming that the laser operates in the anomalous-dispersion regime. The time-bandwidth product was equal to 0.47, indicating that the pulses were nearly bandwidth-limited with Gaussian temporal and spectral profiles. The average value of the cavity dispersion near 1 µm, estimated from the soliton sidebands, was -1.6 ps<sup>2</sup>. With a master oscillator power amplifier configuration (MOPA) more than 200 mW of the output power is expected with just two single-mode pump laser diodes.
We demonstrate a practical ultra-fast Nd-doped fiber laser operating in the 894-909 nm spectral range, in both soliton and stretched pulse dispersion supporting regimes. Using purposely designed semiconductor saturable absorbers, a truly self-started mode-locking regime of operation with clean, transform limited pulses, was achieved.
We assess different power limits of cladding-pumped fiber lasers. Despite recent advances in pump sources, these are still primarily limited by available pump power. We find that it should be possible to reach output powers beyond 1 kW in single-mode ytterbium doped fiber lasers. Experimentally, we have realized an ytterbium-doped fiber laser with 272 W of output power at 1080 nm, with an M<sup>2</sup>-value of 3.2, as well as an erbium-ytterbium co-doped fiber laser with 103 W of output power at 1565 nm, with an M<sup>2</sup>-value of 2.0. We believe these are the highest-power ytterbium and erbium-ytterbium fiber lasers ever reported.
We present a detailed description of a passive harmonically mode-locked laser. Experimental results are consistent with the suggestion of a passive self-stabilization effect driven by transverse acoustic wave excitation due to electrostriction. We also demonstrate some applications of the laser.
It is well known that Neodymium glasses are widely used as active media in powerful picosecond laser systems. However, low thermal conductivity of glasses with broad bands of absorption and luminescence limits their use in pulsed lasers with high repetition rate. At the same time, disordered crystals having broad inhomogeneous bands of active ions and combining properties of both glasses and crystals may be reckoned as active media for ultrashort pulse lasers with high repetition rate. It has been shown recently that Calcium-Niobium-Gallium disordered garnet crystals doped with Nd3+ ions (CNGG:Nd3+) with broad inhomogeneous spectrum of amplification are prospective active media for the laser generation of powerful ultrashort pulses1 . In ref. 1 a passively mode-locked (PML) with a saturable dye absorber CNGG:Nd3+ laser generated trains of 7 ps pulses at a repetition rate of 0.3 Hz. To eliminate a liquid absorber and get an all solid state laser configuration one can mode-lock a laser actively with a crystalline modulator. But while the active mode-locking (AHL) technique may lead to the generation of high stable and reproducible laser pulses with a high repetition rate, its main drawback in comparison with the PML is relatively large pulse duration, in particular, at lamp pumping. Nevertheless, the use of a highly efficient LiNb03 acousto-optic modulator (AOMJ 2 •3 in a glass laser has led to the generation of pulses with duration of 13 ps 4 , so the operation of a laser on disordered crystals doped with Nd 3+ ions actively mode-locked with the AOM is a matter of considerable interest. It is known also that LiF crystals with F 2 color centers are successfully employed for passive Q-switching6 and the application of these crystals as passive Qswitchers to AHL lasers may give sufficient rise to pulse peak power. The aim of this work is to investigate the operation of actively mode-locked with LiNb03 AOM laser on a Calcium-Lithium-Niobium-Gallium disordered garnet crystal doped with Nd3+ ions (CLNGG:Nd3+) and a LiF:F2 passive Q-switch.