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.

Femtosecond Mamyshev fiber oscillator started by a passively Q-switched microchip laser.

A femtosecond Mamyshev fiber oscillator in normal dispersion mode at 1 µm was started reliably and safely by an inexpensive diode-pumped passively Q-switched monolithic microchip laser emitting 300-ps pulses. Four-wave mixing spectral broadening is shown to play a pivotal role in starting the Mamyshev oscillator, owing to the random short and intense temporal fluctuations allowed by its ∼10-nm bandwidth. Systematic studies of the starting dynamics show that a success rate of 100% of the attempts is achieved with modest seed energy, as low as ∼30 nJ from the sub-nanosecond laser, corresponding to ∼100 pJ for the total four-wave mixing signal required to start the oscillation.

Low-noise Yb:CALGO optical frequency comb.

We report on a compact optical frequency comb, operating in the wavelength range from 670 to 1500 nm, based on diode-pumped low-noise femtosecond Yb:CALGO amplified laser system. Both the carrier-envelope offset and repetition rate are phase-locked to reference synthesizers. A full characterization of the frequency comb, in terms of frequency stability, phase noise analysis, and optical beating against a single-frequency non-planar ring oscillator Nd:YAG laser, is presented, showing the excellent properties of the Yb:CALGO comb.

Electrically driven source of time-energy entangled photons based on a self-pumped silicon microring resonator.

Time-energy entangled photon pairs are fundamental resources for quantum communication protocols since they are robust against environmental fluctuations in optical fiber networks. Pair sources based on spontaneous four-wave mixing in silicon microring resonators usually employ expensive external tunable lasers to compensate for ambient fluctuations; adopting self-pumped configurations, instead, lifts the need for such external source. Here we demonstrate the emission of time-energy entangled photon pairs at telecom wavelengths from a silicon self-pumped ring, obtaining a Franson interference fringe with 93.

Few-optical-cycle pulse generation based on a non-linear fiber compressor pumped by a low-energy Yb:CALGO ultrafast laser.

Pulse compression in a short, normal dispersion photonic-crystal fiber is investigated with a Yb:CaGdAlO laser pumped by a low-power fiber-coupled single-mode diode that delivers 70-fs pulses at 1050 nm central wavelength, with 45-mW average power at 60 MHz repetition rate. A simple and power-efficient compressor based on a ∼15-cm long, low-cost commercial nonlinear fiber, with normal dispersion at the laser wavelength, produces pulses as short as 14.9 fs, corresponding to ∼4.

Multi-watt amplification in a birefringent Yb:LiLuF single crystal fiber grown by micro-pulling-down.

We present, to the best of our knowledge, the first demonstration of a single crystal fiber solid-state amplifier based on a birefringent Yb-doped thin crystal grown by the micro-pulling-down method. We measured a small signal gain >30 in a four-passes Yb:LiLuF amplifier pumping with a 120-W maximum power fiber-coupled laser diode. At an absorbed pump power of 80 W, a maximum output power of 8.

Jitter investigation of narrow-bandwidth passively Q-switched Nd:YAG unidirectional ring laser.

A passively Q-switched Nd:YAG undirectional ring laser with external feedback is reported. The laser generates 50 ns single-axial-mode pulses up to 6 kHz, with energy 34 μJ, M<1.05, and pulse jitter <50  ns rms, which is quite remarkable for this class of devices.

Passively Q-switched single-frequency Nd:YVO ring laser with external feedback.

A compact diode-pumped Nd:YVO ring laser was developed for generation of relatively long (few tens nanoseconds) single-frequency pulses for high-spectral-resolution LIDAR applications. Exploiting the feedback from an external mirror and Cr:YAG passive Q-switching with pulsed pump, unidirectional single-frequency operation with high quality ∼50-ns, 80-µJ TEM pulses was achieved from 100 Hz to 10 kHz. Amplitude, duration and repetition rate stability of the pulses was better than 1%.

Laser investigation of Yb:YLF crystals fabricated with the micro-pulling-down technique.

Fiber rods of 10% doped Yb:YLF were fabricated with the micro-pulling-down technique and characterized. The crystal a axis was oriented along the rod length, allowing polarized emission with the largest cross section available in the c direction. Laser experiments showed that these fiber samples perform similarly to crystals grown by the standard Czochralski method.

Continuous-wave and SESAM mode-locked femtosecond operation of a Yb:MgWO laser.

We present a detailed continuous-wave regime characterization and, for the first time to the best of our knowledge, SESAM mode-locked femtosecond operation with a monoclinic, Yb-doped, MgWO crystal. Pumping with a low-power, single-mode fiber-coupled laser diode emitting at 976 nm, we demonstrate threshold for continuous-wave (cw) operation as low as 50 mW (absorbed pump power) and slope efficiency up to ~60% (with respect to the absorbed pump power) for two of the principal emission polarizations. The output wavelength in the cw regime is continuously tunable over a ∼50 nm broad range.

Threshold reduction and mode selection with uncoated Raman crystal acting as a low-finesse cavity.

We report a stimulated Raman scattering threshold reduction by a factor of ∼4 using a simple uncoated SrWO crystal with plane/parallel faces pumped by 1.5 mJ, 11 ns single-frequency pulses at 532 nm. The weak etalon effect is sufficient to shape both the spatial and spectral characteristics of the output Raman beam.

87  fs pulse generation in a diode-pumped semiconductor saturable absorber mirror mode-locked Yb:YLF laser.

A Yb:YLF crystal has been investigated in a femtosecond oscillator pumped by two 400 mW single-mode fiber-coupled diodes emitting at 976 nm and mode locked with a semiconductor saturable absorber mirror. Almost Fourier transform-limited pulses with durations of 87 and 107 fs were demonstrated for extraordinary and ordinary polarizations, respectively. This is, to the best of our knowledge, the first demonstration of sub-100 fs pulses with Yb:YLF, and it proves the potential for ultrashort pulse generation and amplification with this material.

Ultrafast, solid-state oscillators based on broadband, multisite Yb-doped crystals.

A detailed performance comparison of new interesting Yb-doped crystals in the same oscillator setup, with single-mode fiber-coupled diode laser pump is reported. We intended to assess the shortest pulses achievable with available SESAM technology, running a fair comparison with laser crystals Yb:KLuW, Yb:SSO, Yb:CALGO, Yb:CALYO and Yb:CaF, very likely including the most promising choices for the next generation of commercial bulk ultrafast solid-state systems.

Performance of Yb:Scâ‚‚SiOâ‚… crystal in diode-pumped femtosecond oscillator and regenerative amplifier.

Yb:Sc2SiO5 has been investigated in a low-power laser femtosecond oscillator pumped by 400-mW single-mode fiber-coupled diode at 976 nm. Pulses as short as 71 fs were achieved. The same crystal was later employed in a regenerative amplifier, with an output power as high as 4.

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.

Narrow bandwidth, picosecond, 1064  nm pumped optical parametric generator for the mid-IR based on HgGa₂S₄.

We report on optical parametric generation in a mercury thiogallate (HgGa2S4) crystal pumped by 16 ps, 1064 nm pulses at 250 kHz. A broad tuning range extending from 1.19 to 1.

Narrow-bandwidth, ~100 ps seeded optical parametric generation in CdSiP2 pumped by Raman-shifted pulses at 1198 nm.

Low-threshold, efficient optical parametric generation at ~4.64 μm is demonstrated using CdSiP2 nonlinear crystal pumped by 150 ps Raman shifted pump pulses at 1198 nm in noncritical configuration at 1 kHz repetition rate. Maximum single pulse idler energy of 6 μJ and total conversion efficiency of 30% are achieved.

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.

Nd:YVO4 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.

Narrow-bandwidth, mid-infrared, seeded optical parametric generation in 90° phase-matched CdSiP2 crystal pumped by diffraction limited 500 ps pulses at 1064 nm.

Low-threshold, efficient optical parametric generation at ~6100 nm is demonstrated using CdSiP2 nonlinear crystal at 1 to 10 kHz repetition rates with relatively long 500 ps pump pulses at 1064 nm. Maximum single pulse energy of 8.7 μJ and average power of 79 mW are achieved for the idler.

40-fs Yb3+:CaGdAlO4 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.

80-fs Nd:silicate glass laser pumped by a single-mode 200-mW diode.

A Nd(3+)-doped Schott LG680 silicate glass laser was pumped with a single-mode 200-mW diode. Efficient cw operation was demonstrated with 37.5 mW output power and 36% slope efficiency.

Low-threshold femtosecond Nd:glass laser.

Using a 150-mW single-transverse-mode laser diode at 802 nm for pumping an Nd:phosphate laser, we achieved efficient cw operation (40% slope efficiency) with pump threshold as low as 12 mW at optimum coupling, and a maximum output power of 53 mW. Under passive mode-locking operation, we obtained nearly Fourier-limited 270-fs pulses in a prismless dispersion-compensated cavity and 173-fs pulses with a single-prism setup. This compact laser is especially interesting for applications requiring low power levels, such as seeding amplifiers and for biodiagnostics.

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.

Femtosecond Nd:glass oscillator operating in normal dispersion regime.

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.