Photonics Research, Volume. 11, Issue 6, 978(2023)
Impact of laser chirp on the polarization of terahertz from two-color plasma
Fig. 1. Experimental setup. The beam from the laser is split into two parts. The reflected part is used as a probe to detect THz with electro-optic sampling (EOS), and the other is used as a pump to generate THz. In the pump arm, another beam splitter is inserted to reflect part of the beam for monitoring the pulse width with SSA. The pump laser is focused by a lens. Between the lens and its focus, a BBO crystal is inserted. Transmitted FW and SH create two-color plasma, and THz is radiated. A PM collimates THz, and a second PM focuses THz. A third PM collimates THz again, and a fourth PM focuses THz for EOS. Between the third and fourth PMs, another PM mounted on a flip platform (PM in the dashed square) switches between THz electric field and power detections. The inset coordinate system shows the THz polarization and propagation directions. M, mirror; L, lens; PM, parabolic mirror; PD, photodiode; PBS, polarizing beam splitter; SSA, single shot autocorrelator.
Fig. 2. THz polarization characterized by a pyroelectric sensor and electro-optic sampling (EOS). (a) Power of THz transmitted through a THz polarizer versus the transmission axis angle
Fig. 3. THz polarization variation with positive and negative chirps. The black arrows show the THz polarization rotation by looking into the increasing pulse width direction. The red arrows indicate the THz polarization rotation by looking into the increasing phase difference direction (see details in the text). The numbers near the curves are the pulse widths. (a) Polarization rotation for positively chirped pulses. (b) THz polarization rotation in the
Fig. 4. THz intensity versus BBO-to-focus distance (BFD) with different laser chirps. The movement direction of the curves with pulse width is related to the initial phase difference
Fig. 5. Initial phase difference
Fig. 6. THz polarization versus BBO-to-focus distance (BFD) at fixed laser chirps. The phase difference variation between FW and SH is realized by changing BFD for two typical positive and negative laser chirps. The left (right) column shows THz polarization trajectories and THz yield for pulse width equal to 110 (340) fs with a positive (negative) chirp. (a) and (c) THz polarization trajectories rotate clockwise (anticlockwise) with an increasing phase difference between FW and SH when the laser is positively (negatively) chirped. The arrows show the rotation directions. (b) and (d) THz yield versus BFD. The red open circles are experimental data. The black curves are fitting results with Eq. (
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Sen Mou, Luca Tomarchio, Annalisa D’Arco, Marta Di Fabrizio, Salvatore Macis, Alessandro Curcio, Luigi Palumbo, Stefano Lupi, Massimo Petrarca. Impact of laser chirp on the polarization of terahertz from two-color plasma[J]. Photonics Research, 2023, 11(6): 978
Category: Ultrafast Optics
Received: Jun. 24, 2022
Accepted: Nov. 27, 2022
Published Online: Jun. 8, 2023
The Author Email: Sen Mou (sen.mou@roma1.infn.it)