Speaker
Description
Coherent THz radiation has become an important type of electromagnetic radiation in many fields of basic and applied studies of matter. It also serves as a valuable diagnostic of longitudinal bunch characteristics in electron accelerators. Electro-optic methods enable direct measurement of the THz field. In the customary method of electro-optic sampling (EOS), it is necessary to make many sequential EOS measurements at varying delays to reconstruct a complete THz. This method is not effective if the THz waveform is changing shot-to-shot in any way (timing jitter, phase, etc.), therefore it is necessary to develop methods that provide more complete information for each shot.
We present here, a novel technique that enables shot-to-shot measurement of both the magnitude and phase of the THz field using a single NIR laser pulse. The method is robust and utilizes standard ADC for data acquisition, and thus has significant potential for real-time diagnostics even at high repetition rates.
As a demonstration, we utilize this setup to measure the shot-to-shot carrier envelope phase (CEP) of the FELBE FEL operating at a continuous rep. rate of 13 MHz. This powerful technique overcomes the problem of the unstable CEP that is typical in an oscillator FEL to enable phase-resolved measurements of the FEL pulses. This method is critical for the study of coherent THz-driven phenomena, and also has significant potential in the pursuit of CEP stability in an oscillator FEL as well as other THz-based accelerator diagnostics.
