Two-color plasma, induced by two lasers of different colors, can radiate ultra-broadband and intense terahertz (THz) pulses, which is desirable in many technological and scientific applications. It was found that the polarization of the emitted THz depends on the phase difference between the fundamental laser wave and its second harmonic. Recent investigation suggests that chirp-induced change of pulse overlap plays an important role in the THz yield from two-color plasma. However, the effect of laser chirp on THz polarization remains unexplored. Hereby, we investigate the impact of laser chirp on THz polarization. It is unveiled that the chirp-induced phase difference affects THz polarization. Besides, positive and negative chirps have opposite effects on the variation of the THz polarization versus the phase difference. The polarization of THz generated by a positively chirped pump laser rotates clockwise with an increasing phase difference, while it rotates anticlockwise when generated by a negatively chirped pump laser.

中文翻译：

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激光线性调频对双色等离子体太赫兹偏振的影响

由两种不同颜色的激光诱发的双色等离子体可以辐射超宽带和强太赫兹 (THz) 脉冲，这在许多技术和科学应用中都是可取的。发现发射的太赫兹的偏振取决于基波激光波及其二次谐波之间的相位差。最近的研究表明，线性调频引起的脉冲重叠变化在双色等离子体的太赫兹产量中起着重要作用。然而，激光线性调频对太赫兹偏振的影响仍未得到探索。因此，我们研究了激光线性调频对太赫兹偏振的影响。揭示了线性调频引起的相位差影响太赫兹偏振。此外，正负线性调频对太赫兹偏振随相位差的变化具有相反的影响。