BEGIN:VCALENDAR VERSION:2.0 PRODID:-//CERN//INDICO//EN BEGIN:VEVENT SUMMARY:Amplification of THz Radiation by Strong Interaction of Drifting E lectrons with Plasmons in Graphene and GaN DTSTART;VALUE=DATE-TIME:20220707T094500Z DTEND;VALUE=DATE-TIME:20220707T103000Z DTSTAMP;VALUE=DATE-TIME:20260521T051830Z UID:indico-contribution-87-785@events.ncbj.gov.pl DESCRIPTION:Speakers: Wojciech Knap (CENTERA Laboratories\, Institute of H igh Pressure Physics PAS\, Warsaw)\nMore than 40 years ago\, a new directi on in physics opened up with the arrival of plasma-wave electronics. The p ossibility that the plasma waves could propagate faster than electrons fas cinated all. Therefore\, it was initially expected that plasmonic devices\ , including detectors and generators of electromagnetic radiation\, would be able to work effectively in the very high frequencies - terahertz (THz) range\, inaccessible to standard electronic devices. However\, numerous e xperimental attempts to realize the amplifiers or emitters failed: the int ensity of radiation turned out to be too small\, plasma resonances too bro ad\, or devices operated only at cryogenic temperatures. \nWe demonstrate – for the first time- experimentally strong interaction of resonant pla smons in Graphene with drifting electrons leading to THz radiation amplifi cation with a gain going up to 9%. The results are interpreted using a dis sipative plasmonics crystal model\, which captures some trends and basic p hysics of the amplification phenomena but is far from being completed [1] .\nWe will present challenges of both experimental and theoretical researc h on the strong plasmons-drifting electrons- THz light interaction in Dira c matter - that were recently (2022) recognized as an important research direction by EU commission - awarding ERC -Advanced grant –“TERAPLAS M” that will be realized by CENTERA laboratory – UNIPRESS-PAN in cons ortium with CEZAMAT – Technical University of Warsaw and in collaboratio n with teams from Japan France Germany\n\n[1] Boubanga-Tombet S\, Knap W\, Yadav D\, Satou A\, But DB\, Popov VV\, Gorbenko IV\, Kachorovskii V\, Ot suji T: Room-Temperature Amplification of THz Radiation by Grating-Gate Gr aphene Structures. Phys Rev X 2020\; 10(( 3): 031004. [DOI: 10.1103/PhysRe vX.10.031004]\n\nhttps://events.ncbj.gov.pl/event/75/contributions/785/ LOCATION:Novotel Warszawa Centrum Róża URL:https://events.ncbj.gov.pl/event/75/contributions/785/ END:VEVENT BEGIN:VEVENT SUMMARY:Graphene plasmonics: THz nonlinearities beyond thermal effects DTSTART;VALUE=DATE-TIME:20220707T090000Z DTEND;VALUE=DATE-TIME:20220707T094500Z DTSTAMP;VALUE=DATE-TIME:20260521T051830Z UID:indico-contribution-87-754@events.ncbj.gov.pl DESCRIPTION:Speakers: Martin Mittendorff (University of Duisburg-Essen)\nG raphene is a very versatile material for optoelectronics or nonlinear opti cs in a large spectral range\, in particular for THz radiation. One drawba ck is the low interaction volume between THz radiation and the single atom ic layer\, which limits the light matter interaction at elevated photon fr equencies. During the recent years it has been shown that patterning graph ene into plasmonic structures\, e.g. ribbons or disks\, can shift the rath er strong optical response of free charge carriers at low frequencies to a more confined plasmonic resonance at higher frequencies. The size of the structure\, in combination with the carrier density\, determines the plasm on frequency\, that can be tailored in a wide range. Beyond the linear abs orption\, the nonlinear optical properties are enhanced by about two order s of magnitude under resonance compared to unpatterned graphene. Here we p resent a set of studies that quantify the thermal effect when the structur es are excited with strong laser pulses: the charge carriers are heated ef ficiently\, as their specific heat is rather low\, which leads to a decrea sed chemical potential and therewith a reduced plasmon frequency. Compared to thermal nonlinearities in conventional materials\, thermal nonlinearit ies in graphene are very fast as the hot charge carriers cool down within several tens of picoseconds. Polarization-resolved pump-probe measurements on graphene disks revealed nonlinear absorption beyond thermal effects\, i.e. plasmonic nonlinearities: thermal and nonthermal effect can be distin guished by using cross- and co-polarized pump-probe measurements. Numerica l simulations considering thermal as well as plasmonic nonlinearities\, ma tch the observed signals well\, giving a complete picture of the nonlinear processes in graphene plasmons.\n\nhttps://events.ncbj.gov.pl/event/75/co ntributions/754/ LOCATION:Novotel Warszawa Centrum Róża URL:https://events.ncbj.gov.pl/event/75/contributions/754/ END:VEVENT END:VCALENDAR