We present a free-running 80-MHz dual-comb polarization-multiplexed solid-state laser which delivers 1.8 W of average power with 110-fs pulse duration per comb. With a high-sensitivity pump-probe setup, we apply this free-running dual-comb laser to picosecond ultrasonic measurements. The ultrasonic signatures in a semiconductor multi-quantum-well structure originating from the quantum wells and superlattice regions are revealed and discussed. We further demonstrate ultrasonic measurements on a thin-film metalized sample and compare these measurements to ones obtained with a pair of locked femtosecond lasers. Our data show that a free-running dual-comb laser is well-suited for picosecond ultrasonic measurements and thus it offers a significant reduction in complexity and cost for this widely adopted non-destructive testing technique.

Silicoaluminophosphates of the framework types CHA (SAPO-34) and AFI (SAPO-5) are deposited onto the surface of open-celled ceramic SiC foam monoliths by direct crystallization. Therefore, a conventional hydrothermal synthesis is carried out in the presence of SiC foam monoliths with pore densities of 10 and 30 PPI, respectively. Moreover, the crystallization time is varied to determine its effect on the coating produced. In all cases, the direct crystallization of the respective SAPO material is successful. Irrespective of the pores density of the ceramic foam a variation of the crystallization time (SAPO-5: 20 h/30 h, SAPO-34:30 h/45 h) does not show any influence on the thickness of the layers produced as suggested by optical microscopy. However, in the case of SAPO-34 these layers are clearly thicker than the layers of SAPO-5, which leads to a partial blockage of the pores of the ceramic foam with a pore density of 30 PPI. As proved by N 2 -sorption measurement, the coatings offer BET surface areas comparable with those reported for pure powder samples.

We present a high power optical parametric oscillator (OPO) synchronously pumped by the second-harmonic of a modelocked 1030-nm thin-disk laser (TDL) oscillator. The OPO delivers an average power of 51.1 W around degeneracy (1030 nm) with a 10.2-MHz repetition-rate. After extra-cavity dispersion compensation using dispersive mirrors, we obtain a pulse duration of 169 fs, which is 4.6× shorter than the TDL pulse duration of 770 fs. The TDL has 250 W average power, which is converted to 215 W at the second-harmonic. Hence, the OPO exhibits a high photon conversion efficiency of 47% (ratio of signal photons to 515-nm pump photons). Moreover, the OPO generates a peak power of 26.2 MW, which is very similar to the 28.0-MW peak power of the TDL. To facilitate continuous tuning around degeneracy and convenient extraction of the pump and idler beams, the OPO is operated in a noncollinear configuration. A linear cavity configuration was chosen since it offers easy alignment and straightforward cavity length tuning. To the best of our knowledge, this source has the highest average power generated by any ultrafast OPO, and the shortest pulse duration for any >5-W OPO. This result is an important step to adding wavelength tunability to high power Yb-based laser sources without the complexity of either laser or parametric amplifier systems.

Transformative research requires transdisciplinary collaboration, forcing researchers out of their disciplinary comfort zones. In transdisciplinary research projects, the role of (social) scientists changes, and non-scientific actors become part of research projects. Transdisciplinary research is particularly suited to not only generate scientific knowledge, but also invent real-world solutions and to innovative. This, however, does not come without challenges. Implementing a transdisciplinary project is time-consuming and requires the alignment of both the research and impact ambitions of all project partners. In this paper we build upon experiences gained in four transdisciplinary research projects and ask: (1) What is the transdisciplinary approach followed by the project? (2) Which opportunities and challenges can be identified for successful transdisciplinary collaborations? (3) What is the rationale for engaging in transdisciplinary research from the perspective of social scientists? Building upon the logics of interdisciplinary, a fourth logic, called the logic of empowerment, is identified as a driver for transdisciplinary research. Transdisciplinary collaboration empowers researchers to not only ‘discover’ innovations, i.e., to invent, but also to implement, i.e., to innovate.

We demonstrate a free-running single-cavity dual-comb optical parametric oscillator (OPO) pumped by a single-cavity dual-comb solid-state laser. The OPO ring cavity contains a single periodically-poled MgO-doped LiNbO3 (PPLN) crystal. Each idler beam has more than 245-mW average power at 3550 nm and 3579 nm center wavelengths (bandwidth 130 nm). The signal beams are simultaneously outcoupled with more than 220 mW per beam at 1499 nm and 1496 nm center wavelength. The nominal repetition rate is 80 MHz, while the repetition rate difference is tunable and set to 34 Hz. To evaluate the feasibility of using this type of source for dual-comb applications, we characterize the noise and coherence properties of the OPO signal beams. We find ultra-low relative intensity noise (RIN) below –158 dBc/Hz at offset frequencies above 1 MHz. A heterodyne beat note measurement with a continuous wave (cw) laser is performed to determine the linewidth of a radio-frequency (RF) comb line. We find a full-width half-maximum (FWHM) linewidth of around 400 Hz. Moreover, the interferometric measurement between the two signal beams reveals a surprising property: the center of the corresponding RF spectrum is always near zero frequency, even when tuning the pump repetition rate difference or the OPO cavity length. We explain this effect theoretically and discuss its implications for generating stable low-noise idler combs suitable for high-sensitivity mid-infrared dual-comb spectroscopy (DCS).