Luca Carrà

High-gain diode-pumped amplifier for generation of microjoule-level picosecond pulses.

A diode-pumped single-pass amplifier system relying on two grazing-incidence Nd:YVO(4) slabs was developed to increase the energy of low-repetition-rate pulses from a decimated low-power cw mode-locked oscillator. Single-pass unsaturated gain up to 1.3x10(5) was achieved, and amplified pulses of 10-muJ energy and 8.0-ps duration were obtained. Efficient second harmonic generation (SHG) at 532 nm was achieved, as well as traveling-wave parametric conversion in the range 770-1020 nm (signal) and 1110-1720 nm (idler).

Amplification of a low-power picosecond Nd:YVO/sub 4/ laser by a diode-laser side-pumped grazing-incidence slab amplifier

An optimized diode-laser side-pumped grazing-incidence Nd:YVO4 amplifier was used to increase the power of a 50-mW 150-MHz continuous-wave (CW)-pumped mode-locked oscillator up to 6.1 W in single pass, with 22% optical-to-optical efficiency, or up to 8.4 W in double pass, with 30% efficiency. Both beam quality (M2<1.4 from TEM00 seed pulses) and pulse duration (7.5 ps from 6.9 ps) were preserved. Single- or double-pass small-signal gain greater than 40 dB was achieved. These experimental results have been corroborated by a numerical model analysis of the amplifier

Nd:YVO 4 amplifier for ultrafast low-power lasers

An Nd:YVO4 amplifier consisting of two modules end pumped at 808 nm at 30 W total absorbed power has been designed for efficient, diffraction-limited amplification of ultrafast pulses from low-power seeders. We investigated amplification with a 50 mW, 7 ps Nd:YVO4 oscillator, a 2 mW, 15 ps Yb fiber laser, and a 30 mW, 300 fs Nd:glass laser. Output power as high as 9.5 W with 8 ps pulses was achieved with the 250 MHz vanadate seeder, whereas the 20 MHz fiber laser was amplified to 6 W. The femtosecond seeder allowed extracting Fourier-limited 4 ps pulses at 7 W output power. To our knowledge, these are the shortest pulses from any Nd:YVO4 laser device with at least 7 W output power. This suggests a novel approach to exploit the gain bandwidth of vanadate amplifiers with high output power levels. Such amplifier technology promises to offer an interesting alternative to high-power thin disk oscillators at few picoseconds duration, as well as to regenerative amplifiers with low-repetition-rate fiber seeders.

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-μm wavelength has been achieved with a Nd:BaY2F8 (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 ≈70-mW output power for ≈570-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 narrow-band neodymium lasers are reviewed and their implications are discussed.

210-

A single-pass two-stage Nd:YVO4 amplifier was used to increase the energy of a 7.7-ps seed pulse from < 1 nJ to 210 muJ (11-ps time duration), maintaining the input spatial quality of the pulse. The laser-diode side-pumped grazing-incidence Nd:YVO4 slab amplifier was optimized for minimum amplified spontaneous emission noise and for maximum energy extraction, with single-pass small-signal gain of 59 dB. Diffraction-limited operation up to 1 kHz is possible. Conversion efficiency of 75 % at 532 nm and 40% at 266 nm was observed.

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We report a passively mode-locked picosecond ytterbium-doped fiber laser operating in the normal dispersion regime, tunable over 70 nm around 1.05 μm. Mode-locking operation is achieved through a free-space coupled semiconductor saturable absorber. An external grating in Littrow configuration is used for both tuning and mode-locked stabilization through spectral filtering. Pulse duration of 19 ps with pulse repetition rates below 20 MHz is obtained with a maximum average output power of 1.5 mW.

J Picosecond Pulses From a Quasi-CW Nd:YVO

A diode-pumped, prismless Nd:glass laser oscillator, mode-locked by a semiconductor saturable absorber, was stabilized against self-Q-switching by using a phase-mismatched second harmonic crystal. Furthermore, negative-index cascaded second-order nonlinearity provided the soliton shaping mechanism with normal intracavity dispersion. Nearly Fourier-limited pulses as short as 520 fs were obtained.

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A single pass, side pumped grazing incidence Nd:YVO₄ amplifier, optimized for minimum ASE noise, was used to increase the energy of 10-ps mode-locking seed pulses from 1 nJ to 210 muJ, with M²=1.3.

Grazing-Incidence Two-Stage Slab Amplifier Package

Thanks to the reduced quantum defect with respect to Nd doped materials, Yb doped crystals are widely employed as laser material in high-power diode-pumped lasers. YAG crystalline matrix, thanks to its remarkable thermo-mechanical properties is particularly suitable for high-power management. Moreover, the relatively broad fluorescence bandwidth of Yb:YAG allows ultrashort pulse generation, even at very high average power. Ceramic Yb:YAG has also been investigated in recent years since it promises cheaper devices and larger volume fabrication, while maintaining the attractive properties of the single crystal. In this work, we investigated the growth, spectroscopy and laser operation of two Yb:YAG ceramic samples. We demonstrated a combination of average power (4.4 W), pulse duration (~7 ns), peak power (~12 kW) and repetition rate (~50 kHz) in Passive Q-switching (PQS) operation that set the state of the art for medium power Yb-doped solid-state lasers and can be very attractive for many material processing applications.