KOHERENT · Kerr based Opa for High Energy infraRed PulsE geNeraTion

Kerr based Opa for High Energy infraRed PulsE geNeraTion

KOHERENT Summary Matteo Clerici Heriot-Watt University, Edinburgh EH14 4AS, UK. Email: m.clerici@hw.ac.uk KOHERENT, namely “Kerr-based optical parametric amplification for high energy infrared pulse generation” aims at boosting high-energy, long wavelength ultrafast laser technology. Intense and short laser pulses are able to strongly interact with matter, owing their ability to reach extremely high intensities when condensed on a small spatial scale. Long wavelengths, differently from the routinely employed 800 nm radiation, are favorable for a large number of processes, such as high-order harmonic generation and energy transport over long distances, yet the technology for delivering intense long wavelength radiation is not as mature as the near infrared counterparts, which rely on the well-known laser amplifier based on a Titanium doped sapphire gain medium. KOHERENT is aimed at boosting the development of long wavelength laser technology both for what concern the radiation generation, detection and its applications. The objectives of KOHERENT are therefore on the one hand the development of a novel source and detectors of long wavelength coherent radiation, relying on parametric processes in Kerr media, and on the other the application of this long wavelength radiation to field of photonics, with emphasis to analogue optics. This field allows performing partial experimental investigations of phenomena that are currently outside our technological capabilities, relying on the fact that the mathematical model that describes such phenomena also rule the propagation of light in specific circumstances. Starting from the process of frequency conversion in a centro-symmetric material, central to KOHERENT, we succeeded in demonstrating novel routes to efficiently produce long wavelength in the tens of micrometer wavelength range. We indeed demonstrated a > 30 times enhancement in the efficiency of terahertz emission (at nearly 60 μm, from air ionization by employing a mid-infrared pump laser, instead of a standard 800 nm one [1]). These results have been enabled by the collaboration with top level scientists dedicated to the development of mid-infrared parametric source working at INRS-EMT (the outgoing institution, Canada), at Heriot- Watt University (the return institution), and the fellow’s know-how. These results, published in 2013 in an important peer-review journal, have been highly cited, witnessing their impact to the photonics community. Following these investigations, we have also developed a substantial know-how on parametric interactions with long wavelength pulses both in air and in solid state media, allowing us to demonstrate novel detection schemes for characterizing i) the absolute phase of mid- and far-infrared pulses [2, 3], ii) the far-infrared beam profiles, also in the sub-wavelength case relevant for the emerging field of far-infrared microscopy [4-7], and iii) the radio-frequency pulse train spectrum [8]. Furthermore, we have successfully demonstrated i) a novel way to directly generate the long wavelength radiation into a dispersion-free guiding structure [9], ii) how to control the beam collapse along the nonlinear propagation [10], and iii) how to employ the long wavelength radiation for characterizing the temperature of samples in the biologically relevant temperature window of 30 − 50 C [11]. During the last stage of the fellowship we also succeed in observing an experimental signature of the emission of radiation arising from the scattering of the long-wavelength pulse from a horizon generated by an intense laser in a diamond bulk sample. This emission appears as extremely blue-shifted from the input 60 μm seed and is at the blue side of the visible spectrum (≃ 430 nm). Our experimental results fulfill the KOHERENT section related to enhancing the study of analogue effects with long wavelength radiation and are backed up by extensive theoretical and numerical work [12]. Owing to the strong collaborative efforts of the scientific community to develop novel quantum based technologies exploiting photonics, we have also investigated parametric processes in Kerr media for the generation of infrared radiation at telecom wavelengths (≃ 1.5 μm) for quantum optical applications. Within the framework of an international collaboration based at the outgoing host institution we succeeded in demonstrating a novel stable integrated parametric source [13], a frequency multiplexed integrable quantum state emitter [14] and more recently our results reporting on-chip generation on cross polarized photon pairs have been accepted for publication in a major high-impact journal [15]. These results have high impact on the community developing the future of quantum communication and open the path to exploiting integrated photon pair sources for quantum optics. Finally, building on the developed expertise on photo-ionization induced in air for the generation of long-wavelength radiation, together with the know-how acquired along KOHERENT on the generation of pulses that propagates on curved trajectories [16], we have just recently demonstrated that shaped laser pulses can be employed also for guiding high-voltage electric discharge in air along complex trajectories that are able for instance to avoid an obstacle on the path [17]. These results have been recently published on a major, high-impact journal and have attracted a relevant attention from the general public press, being reported for instance at the German National Radio, on the first page of the Daily Telegraph, and on the Le Monde. These results may find a relevant application to the field of electric assisted machining and milling and work is in progress to capitalize on this initial breakthrough. The activities performed within KOHERENT have been widely advertised both at international scientific meetings (more that 80 contributions), by journal publications (currently 17), by press releases of the host institutions (see e.g. [18, 19]), by seminars (5 in the framework of the project) and outreaching activities performed by the fellow (see e.g. [20, 21]) and on the project webpage www.koherent.eu and the fellow personal webpage www.mclerici.com. Among the major results of KOHERENT is also the fellow training. The international experience allowed him to develop a broad network of collaboration and to mature a position of professional independence that allowed him to succeed in the process of recruitment within the academic world in Europe, thus fulfilling the final training goal of this fellowship. REFERENCES [1] M. Clerici et al., Phys. Rev. Lett. 110, 253901 (2013). [2] M. Clerici et al., Invited on New J. Phys. 15, 125011 (2013). [3] M. Clerici et al., SPIE Photonics Asia, invited, Beijing, China, October 9-11 (2014). Manuscript in preparation. [4] M. Clerici et al., Opt. Lett. 38, 178 (2013). [5] M. Clerici et al., Opt. Lett. 38, 1899 (2013). [6] M. Peccianti et al., IEEE J. Sel. Top. Quant. 19, 8401211 (2013). [7] S. P. Ho et al., Sci. Rep. 5, 8551 (2015). [8] M. Ferrera et al., Opt. Express 22, 21488 (2014). [9] M. K. Mridha et al., Opt. Express 22, 22340 (2014). [10] A. Pasquazi et al., Phys. Rev. Lett. 113, 133901 (2014). [11] A. Mazhorova et al., TERA-MIR Radiation keynote, Prague, Czech Republic, April 8-11 (2015). [12] M. Clerici et al., arXiv:1403.6026, (2015). Also Ultrafast Optics X, invited, Beijing, August 16-21 (2015). [13] A. Pasquazi et al., Opt. Express 21, 13333 (2013). Manuscript in preparation. [14] C. Reimer et al., Opt. Express 22, 6535 (2014). [15] C. Reimer et al., Nature Comm. accepted, (2015). [16] Y. Hu et al., Opt. Lett. 38, 380 (2013). [17] M. Clerici et al., Science Advances 1, e1400111 (2015). [18] http://www.inrs.ca/english/actualites/could-we-control-path-lightning [19] http://www.hw.ac.uk/news/brightly-guided-sparks.htm. [20] SPIE Newsroom, doi: 10.1117/2.1201312.005240, (2013). [21] http://www.2physics.com/2015/08/bending-electric-discharges-with-lasers.html.

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