Federico Pirzio

40-fs Yb 3+ :CaGdAlO 4 laser pumped by a single-mode 350-mW laser diode

We report the results of the investigation on a passively mode-locked Yb(3+):CaGdAlO(4) laser, pumped by a single transverse mode laser diode emitting 350 mW at 980 nm. This particular pump source allows efficient pumping with a nearly TEM(00) beam and minimal thermal load, making the optimization of the mode-locking performance more straightforward than with higher-power multimode beams. Indeed, using a semiconductor saturable absorber mirror and extra-cavity dispersion compensation, pulses as short as 40 fs (31-nm spectrum) have been measured, tunable across 20 nm with 15-mW output power. Slightly longer Fourier-limited 46-fs pulses with 33 mW output power directly from the oscillator have been achieved, using a different saturable absorber mirror. Such overall performance, especially considering these are among the shortest pulses generated in diode-pumped ytterbium lasers, confirms the excellent qualities of Yb(3+):CaGdAlO(4).

Sub-100-fs Cr:YAG laser mode-locked by monolayer graphene saturable absorber

We report on mode-locking of a Cr:YAG laser at 1516 nm using a monolayer graphene-based saturable absorber of transmission type generating 91 fs pulses with a Fourier product of 0.38 at an average output power exceeding 100 mW. Stable single-pulse mode-locked operation without any sign of Q-switching instabilities or multiple pulses is achieved.

Compact, 1.5 mJ, 450 MHz, CdSiP 2 picosecond optical parametric oscillator near 6.3 μm

We report a compact, efficient, high-energy, and high-repetition-rate mid-IR picosecond optical parametric oscillator (OPO) based on the new nonlinear material CdSiP(2) (CSP). The OPO is synchronously pumped by a master oscillator power amplifier system at 1064.1 nm, providing 1 μs long macropulses constituting 8.6 ps micropulses at 450 MHz, and it can be tuned over 486 nm across 6091-6577 nm, covering the technologically important wavelength range for surgical applications. Using a compact (∼30 cm) cavity and improved, high-quality nonlinear crystal, idler macropulse energy as high as 1.5 mJ has been obtained at 6275 nm at a photon conversion efficiency of 29.5%, with >1.2 mJ over more than 68% of the tuning range, for an input macropulse energy of 30 mJ. Both the signal and idler beams are recorded to have good beam quality with a Gaussian spatial profile, and the extracted signal pulses are measured to have durations of 10.6 ps. Further, from the experimentally measured transmission data at 1064 nm, we have estimated the two-photon absorption coefficient of CSP to be β=2.4 cm/GW, with a corresponding energy bandgap, E(g)=2.08 eV.

28-W, 217 fs solid-state Yb:CAlGdO4 regenerative amplifiers.

A new high-performance Yb:CaAlGdO(4) (Yb:CALGO) regenerative amplifier is demonstrated. Pumped by 116 W at ≈980 nm and seeded by means of a 92 fs oscillator, it generates as much as 36 W of average output power with chirped pulses, and 28 W with 217 fs compressed pulses at 500 kHz repetition rate. This corresponds to 56 μJ of pulse energy and 258 MW peak power. The compressed pulses have a time-bandwidth product of 0.69 and could be shortened further with an improved compressor setup.

Multi-GHz tunable-repetition-rate mode-locked Nd:GdVO4 laser.

We report on a simple design for a multi-GHz tunable-repetition-rate diode-pumped picosecond laser. Using a plano-Brewster Nd:GdVO4 crystal in a V-folded cavity employing only readily available commercial components, we achieved passive mode-locking with 4.4-ps pulses tunable in the range 2.5-2.7 GHz. This laser is meant to be employed in the MIR experiment that aims at the detection of the Schwinger radiation (dynamical Casimir effect).

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).

Sub-50-fs widely tunable Yb:CaYAlO(4) laser pumped by 400-mW single-mode fiber-coupled laser diode.

Yb:CaYAlO(4) has been investigated spectroscopically and compared to better known Yb:CaGdAlO(4). It turns out that both materials show very similar spectroscopic parameters relevant to ultrafast lasers design. Employing single-mode fiber-coupled 400-mW laser diode at 976 nm we measured pulses as short as 43 fs, and broad tunability of 40 nm with a simple single-prism setup.

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

Narrow-bandwidth, mid-infrared, seeded optical parametric generation in 90° phase-matched CdSiP 2 crystal pumped by diffraction limited 500 ps pulses at 1064 nm

Low-threshold, efficient optical parametric generation at 6100 nm is demonstrated with CdSiP2 at 1 to 10 kHz repetition rates with seeding at the signal wavelength employed for narrowing of the idler spectral bandwidth.

99 fs Nd:Glass Laser Mode-Locked with Carbon Nanotube Saturable Absorber Mirror

The mode-locked operation of Nd:silicate glass with both single-walled carbon nanotubes (SWCNTs-SAM) and semiconductor saturable absorber mirrors (SESAMs) has been investigated. SWCNT-SAM mode-locking has been optimized in Nd-doped bulk lasers for the first time, yielding 99-fs pulses at 1070 nm. For comparison, by using a SESAM instead of SWCNT-SAM, pulses as short as 87 fs and a tuning range of 30 nm were achieved. Related to the applied 200-mW single-mode laser diode as pump source the lasers were characterized by high efficiency and low threshold. The optimized low-power pump setup yielded a remarkable slope efficiency of 46.5% in the cw regime.