High Gain Solid-State Amplifiers for Picosecond Pulses

We review solid-state laser amplifiers for generation of intense picosecond pulses, in various regimes from single shot to repetition rates of GHz. Such laser sources are becoming increasingly attractive for many industrial and scientific applications. In particular, we have exploited the technology of side-pumped grazing-incidence bounce amplifiers. Such amplifiers yield very high gain per pass, up to several thousands, and offer excellent beam quality preservation owing to the total reflection leading to left-right inversion. This technology allows the realization of compact, efficient and modular amplifiers, significantly simpler than, for example, cavity-based regenerative schemes. Starting from robust, low-power diode-pumped solid-state oscillators, using programmable pulse-pickers one can select either a single pulse or a properly shaped pulse train for further amplification and compensation of envelope distortions due to gain saturation. For single pulse amplification it is preferred to start with a relatively low-repetition-rate oscillator (< 100 MHz). Picosecond fiber oscillators are most promising in this respect. Using quasi-cw diode arrays as the pump source of Nd:YVO4 slab amplifier, starting from ≈ 1 nJ, 10-ps pulse seed, amplified pulse energy as high as 200 μJ at 1 kHz can be obtained. Efficient harmonic and traveling-wave parametric generation are readily achieved with such high pulse peak powers. Some other applications require instead the amplification of pulse trains, that can be conveniently extracted and amplified from a low-power oscillator at the desired repetition rate. For example, starting from a 20-mW, 5-GHz picosecond oscillator we amplified trains of few thousands of pulses up to 2 mJ with three slab amplifiers (as much as 300 mJ were achieved with two additional Nd:YAG flash-lamp-pumped post-amplifiers). Such pulse trains are very effective for synchronous pumping of optical parametric oscillators, lowering significantly their threshold with respect to the traveling-wave geometry. When multi-MHz picosecond pulses are required, cw diode arrays are chosen as pump sources for the slab amplifiers. An 8-W, 8-ps laser system has been demonstrated starting from a 50-mW cw oscillator, at 150 MHz. Owing to the effective gain shaping of the tightly pumped amplifier, no significant thermal distortion were detected, allowing nearly diffraction limited operation. Although high power picosecond oscillators have been demonstrated lately, this result is interesting since it suggests an alternative way for power-scaling of picosecond sources without pushing delicate intracavity components (such as semiconductor saturable absorbers) to the damage limit. Numerical models of the amplifiers and their dynamics are also reviewed. The effects of amplified spontaneous emission are discussed, as well as the most effective methods for its suppression

Versatile OSCAT time-domain THz spectrometer

: We report on a compact and versatile time-domain spectrometer operating in the THz spectral region from 0.2 to 2.5 THz based on ultrafast Yb:CALGO laser and photo-conductive antennas. The spectrometer operates with the optical sampling by cavity tuning (OSCAT) method based on laser repetition rate tuning, which allows at the same time the implementation of a delay-time modulation scheme. The whole characterization of the instrument is presented and compared to the classical THz time-domain spectroscopy implementation. THz spectroscopic measurements on a 520-μm thick GaAs wafer substrate together with water vapor absorption measurements are also reported to further validate the instrument capabilities

Narrowband, mid-infrared, seeded optical parametric generator based on non-critical CdSiP2 pumped by 120-ps, single longitudinal mode 1,064 nm pulses

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Sub-nanosecond, 1-10 kHz, low-threshold, non-critical OPOs based on periodically poled KTP crystal pumped at 1,064 nm

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Laser system generating 250-mJ bunches of 5-GHz repetition rate, 12-ps pulses.

We report on a high-energy solid-state laser based on a master-oscillator power-amplifier system seeded by a 5-GHz repetition-rate mode-locked oscillator, aimed at the excitation of the dynamic Casimir effect by optically modulating a microwave resonator. Solid-state amplifiers provide up to 250 mJ at 1064 nm in a 500-ns (macro-)pulse envelope containing 12-ps (micro-)pulses, with a macro/micropulse format and energy resembling that of near-infrared free-electron lasers. Efficient second-harmonic conversion allowed synchronous pumping of an optical parametric oscillator, obtaining up to 40 mJ in the range 750-850 nm

Diode-pumped Nd: BaY 2 F 8 picosecond laser mode-locked with carbon nanotube saturable absorbers

Picosecond pulse generation near 1-m wavelength has been achieved with a Nd: BaY 2 F 8 (Nd:BaYF) laser mode-locked using a single-walled carbon nanotube saturable absorber (SWCNT-SA). The laser was operated at its main 1049-nm transition, generating 8.5-ps pulses with Ϸ70-mW output power for Ϸ570-mW absorbed pump power. This is the first demonstration of cw mode-locking in the picosecond regime with Nd-doped crystals and SWCNT-SAs. The requirements on the SWCNT-SA for successful mode-locking in relatively narrowband neodymium lasers are reviewed and their implications are discussed

Special issue on solid state lasers materials, technologies and applications

Even though more than half a century has already passed since the first demonstration of laser action in ruby crystal, solid-state lasers are still a hot research topic.[...

Solid State Lasers Materials, Technologies and Applications

Solid-state lasers offer unique qualities in terms of flexibility, robustness, efficiency, and wavelength diversity. For these reasons, they are nowadays irreplaceable tools in many scientific and industrial applications. The engineering of new materials, the advances in photonics technologies, and the increasing demand for speed, cleanliness, and high-precision in industrial processes contribute to propel the research in this exciting and quickly developing field. Despite the impossibility to cover all the aspects of this very diversified topic in a single publication, this Special Issue "Solid State Lasers Materials, Technologies and Applications" offers an interesting insight into some of the latest developments in this field. Comprehensive review papers describe the state of the art of highly doped fiber lasers and amplifiers, deep-ultraviolet generation, and laser welding under vacuum with high-power lasers. Research articles present the latest results on picosecond pulse amplification, mid-infrared laser sources, parametric down-conversion modules, and coherent beam combining. Heavy-industry applications, such as laser welding and laser cladding, are also addressed

Chapter High Gain Solid-State Amplifiers for Picosecond Pulses

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