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SUMMARY:High repetition rate THz generation by cavity enhanced optical rec
 tification in GaP
DTSTART;VALUE=DATE-TIME:20240219T090000Z
DTEND;VALUE=DATE-TIME:20240219T092000Z
DTSTAMP;VALUE=DATE-TIME:20260417T182859Z
UID:indico-contribution-1150@cern.ch
DESCRIPTION:Speakers: Gianluca Galzerano (Istituto di Fotonica e Nanotecno
 logie - CNR)\nTerahertz (THz) radiation exhibits properties of great inter
 est and potential applications in several scientific fields. For example\,
  THz waves (in the spectral range between 0.1 and 30 THz) find direct appl
 ications in spectroscopy of innovative materials\, time-domain quantum opt
 ics\, and biological sensing [1]. However\, THz science remains challengin
 g because of the lack of suitable sources and detectors. To fill this tech
 nological gap\, various techniques have been explored over the years. For 
 instance\, quantum cascade lasers and photoconductive antennas are well-es
 tablished methods to generate THz radiation [2]. Recently\, frequency down
 -conversion of near-infrared light in nonlinear crystals emerged as a powe
 rful alternative to more traditional methods. In particular\, optical rect
 ification schemes based on ytterbium (Yb) ultrafast lasers are now conside
 red extremely promising [3]. Moreover\, the use of an enhancement resonato
 r able to store the infrared pulses from the Yb laser source boosts the po
 wer that can be used for optical rectification [4]. However\, high-average
  power leads to a high thermal load for the nonlinear crystal. In addition
 \, spatial deformation of the resonant mode can occur when the crystal is 
 under stress inside the cavity\, causing power losses and THz power drops.
  A crystal widely used is Gallium Phosphide (GaP) [5]. Recently\, Hekmat e
 t al. [6] published an extensive study on the behavior of this crystal whe
 n used for single pass optical rectification in the presence of high power
 . In this work\, we propose a preliminary study in a slightly different re
 gime of operation for GaP crystals\, exploiting an enhancement resonator t
 o achieve an average power > 300 W. This offers the chance to investigate 
 the material properties at very high power together with the possibility o
 f understanding the effect of GaP-induced mode deformation inside an enhan
 cement cavity. We propose an experimental setup based on a amplified Yb fi
 ber mode-locking laser (spectral width ~ 7 nm around 1035 nm) with a repet
 ition rate of nearly 100 MHz\, with maximum power of 60 W\, and a pulse le
 ngth of 370 fs. The amplified pulses are boosted to nearly 300 W using an 
 enhancement cavity inside which optical rectification in a GaP crystal tak
 es place. This way\, modal instabilities and high-power-induced effects on
  GaP are observable and characterizable together with the THz generation e
 fficiency. Even if modal instabilities partially limit the maximum gain ac
 hievable with the enhancement cavity\, the comprehension of the phenomenon
  will soon allow the implementation of mitigation strategies to fully expl
 oit the advantage of optical rectification in an enhancement cavity for th
 e high repetition rate and the milliwatt level average power THz generatio
 n\, opening the way to promising applications in the THz region.\n\n**Refe
 rence**\n\n[1] A. Leitenstorfer et al.\, “The 2023 terahertz science and
  technology roadmap\,” J. Phys. D: Appl. Phys. 56\, 22\, 223001 (2023).\
 n\n[2] P. U. Jepsen et al.\, “Terahertz spectroscopy and imaging – Mod
 ern techniques and applications\,” Laser Photonics Rev. 5\, 1\, 124-166 
 (2011).\n\n[3] J. Drs at al.\, “Optical rectification of ultrafast Yb la
 sers: pushing power and bandwidth of terahertz generation in GaP\,” JOSA
  B 36\, 11\, 3039 (2019).\n\n[4] Suerra et al. "Generation of high repetit
 ion rate THz radiation at the millwatt-level via optical rectification in 
 an enhancement cavity\," EPJ Web of Conferences\, 08021 (2023).\n\n[5] J. 
 Li et al.\, “Generation of 0.3 mW high-power broadband terahertz pulses 
 from GaP crystal pumped by negatively chirped femtosecond laser pulses\,
 ” Laser Phys. Lett. 10\, 125404 (2013).\n\nhttps://indico.unina.it/event
 /75/contributions/1150/
LOCATION:Federico II Conference Center Aula B
URL:https://indico.unina.it/event/75/contributions/1150/
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