Florian Kienle

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.

High-power, variable repetition rate, picosecond optical parametric oscillator pumped by an amplified gain-switched diode

We demonstrate a picosecond optical parametric oscillator (OPO) that is synchronously pumped by a fiber-amplified gain-switched laser diode. At 24W of pump power, up to 7.3W at 1.54microm and 3.1W at 3.4microm is obtained in separate output beams. The periodically poled MgO-doped LiNbO(3) OPO operates with ~17ps pulses at a fundamental repetition rate of 114.8MHz but can be switched to higher repetition rates up to ~1GHz. Tunabilty between 1.4microm and 1.7microm (signal) and 2.9microm and 4.4microm (idler) is demonstrated by translating the nonlinear crystal to access different poling-period gratings and typical M(2) values of 1.1 by 1.2 (signal) and 1.6 by 3.2 (idler) are measured at high power for the singly resonant oscillator.

High-power, high repetition-rate, green-pumped, picosecond LBO optical parametric oscillator

We report on a picosecond, green-pumped, lithium triborate optical parametric oscillator with record-high output power. It was synchronously pumped by a frequency-doubled (530 nm), pulse-compressed (4.4 ps), high-repetition-rate (230 MHz), fiber-amplified gain-switched laser diode. For a pump power of 17 W, a maximum signal and idler power of 3.7 W and 1.8 W was obtained from the optical parametric oscillator. A signal pulse duration of ~3.2 ps was measured and wide tunability from 651 nm to 1040 nm for the signal and from 1081 nm to 2851 nm for the idler was achieved.

Compact, high-pulse-energy, picosecond optical parametric oscillator

We report a high-energy optical parametric oscillator (OPO) synchronously pumped by a 7.19 MHz, Yb:fiber-amplified, picosecond, gain-switched laser diode. The 42-m-long ring cavity maintains a compact design through the use of an intracavity optical fiber. The periodically poled MgO-doped LiNbO(3) OPO provides output pulse energies as high as 0.49 μJ at 1.5 μm (signal) and 0.19 μJ at 3.6 μm (idler). Tunability from 1.5 to 1.7 μm and from 2.9 to 3.6 μm is demonstrated, and typical M(2) values of 1.5 × 1.3 and 2.8 × 1.9 are measured for the signal and idler, respectively, at high power.

Green-pumped, picosecond MgO:PPLN optical parametric oscillator

We investigate the performance of a magnesium-oxide-doped periodically poled lithium niobate crystal (MgO:PPLN) in an optical parametric oscillator (OPO) synchronously-pumped by 530nm, 20ps, 230MHz pulses with an average power of up to 2W from a frequency-doubled, gain-switched laser diode seed and a multi-stage Yb:fiber amplifier system. The OPO produces ~165mW (signal, 845nm) and ~107mW (idler, 1421nm) of average power for ~1W of pump power and can be tuned from ~800nm to 900nm (signal) and 1.28µm to 1.54µm (idler). Observations of photo-refraction and green-induced infrared absorption (GRIIRA) in different operational regimes of the MgO:PPLN OPO are described and the role of peak intensity and average power are investigated, both with the aim to find the optimal operating regime for pulsed systems.

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:CaF2, very likely including the most promising choices for the next generation of commercial bulk ultrafast solid-state systems.

42 W femtosecond Yb:Lu 2 O 3 regenerative amplifier.

We report on a femtosecond high-power regenerative amplifier based on Yb:Lu2O3. Exploiting the excellent thermo-mechanical properties of this material, we were able to achieve up to 64.5 W in continuous-wave regime, limited only by the available pump power. In pulsed operation, 42 W of average output power at a repetition rate of 500 kHz with 780 fs long pulses could be demonstrated, resulting in a pulse peak power of ∼100  MW. The spectrum was centered at 1034 nm with an FWHM of 2.4 nm, potentially allowing for even shorter pulses. At the maximum output power the beam was nearly TEM00, with an M2 value of 1.2 in both axes.

Performance of Yb:Sc 2 SiO 5 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 4.7 W at 500 kHz and sub-300-fs pulses.

High power high repetition rate picosecond optical parametric oscillator pumped by frequency doubled all-fiber Yb-doped MOPA

We demonstrate a lithium triborate (LBO) optical parametric oscillator (OPO), which is synchronously pumped with a pulse-compressed and frequency-doubled master-oscillator power-amplifier (MOPA) system consisting of a gain-switched laser diode and a series of Ytterbium-doped fiber amplifiers. The 20ps pulses from the MOPA were compressed in a transmission grating compressor down to 4.4ps with a throughput efficiency of ~70% and subsequently frequency-doubled with an efficiency of ~60% in a 20mm long LBO to a maximum of ~25W. With a typical pump power of 17W for the OPO, we obtained a maximum combined signal and idler output power of 2.5W (at 877nm) and 1.7W (at 1.3μm). Individually, a maximum signal power of up to 3.7W at 740 nm was obtained with a signal pulse duration of ~3.2ps. The OPO was widely tunable from 651nm-1040nm (signal) and from 1081nm-2851nm (idler). To the best of our knowledge, this is the highest output power from a green-pumped LBO OPO. The fiber-based pump source can potentially be operated between 100MHz and 1GHz, which in combination with the few-picosecond pulses and the near-IR tunability of the OPO is a very attractive source for nonlinear microscopy.

Next-generation of high-power, sub-300 fs lasers with >100 W for industrial applications

Femtosecond laser systems are the enabling technology for cold ablation, a process that removes layers of material with virtually no thermal side-effects, and therefore leads to a superior quality without additional post-processing steps [1, 2]. Cold ablation can be applied to even the most complex and hardest to machine materials, like diamond, ceramics, polymers and metals, making the femtosecond laser system a universal tool for micromachining. However, in order to achieve high throughput, high pulse energies at high repetition rates, and therefore high average output power, is required [3].