太赫兹脉冲的正交平衡单次电光测量

Crossed and Balanced Single-Shot Electro-Optic Measurement for Terahertz Pulses

提出了一种基于波长编码的超短太赫兹(THz)脉冲单次探测方法。该方法将新型正交平衡电光取样技术和波长编码技术结合起来,同时拥有这两种方法的优点:能对超快太赫兹脉冲实现高调制度和高信噪比的单次实时测量。为了实现单次测量,采用线性啁啾激光脉冲作为探测光,将太赫兹电场对探测脉冲的时域调制映射到频域,并用光谱仪对频域信息进行单次采集。在电光取样技术方面,采用正交平衡探测取代传统波长编码单次测量,通过设置两臂静态偏置相位,使它们大小相等、符号相反,实现对称推挽式调制,从而有效提高近0°偏置点附近的探测线性度和调制深度,并有效抑制动态噪声。

A method for single-shot detection of ultrashort terahertz （THz） pulse based on wavelength coding is proposed. This method combines the new crossed and balanced electro optic sampling technology and the wavelength coding technology, which has the advantages of both of them： it realizes single-shot real-time measurement for ultrafast THz pulse with high modulation depth and high signal-noise ratio. In order to achieve single shot measurement, linear chirped laser pulses are used as the probe laser to map the temporal modulation of THz wave to the frequency domain, and the information of which is singly-acquired by spectrometers. In the aspect of electro-optic sampling technique, instead of the traditional wavelength coding single-shot measurement method, we use a novel crossed and balanced method. By setting two optical paths with a pair of equal and opposite static bias phases, the symmetrical push-pull modulation is achieved. The detecting linearity and modulation depth near 0° optical bias can be improved effectively, and the dynamical noise is suppressed.