Terahertz microscopy assisted by semiconductor nonlinearities

Real-Time Megapixel Electro-Optical Imaging of THz Beams with Probe Power Normalization

In this work, we present a simple method to improve the spatial uniformity of two-dimensional electro-optical imaging of terahertz (THz) beams. In this system, near-field THz images are captured by fully illuminating a sample using conventional optical microscope objectives. Unfortunately, due to the linear relationship between the optical probe power and the measured THz electric field, any spatial variation in probe intensity translates directly into a variation of the recorded THz electric field. Using a single normalized background frame information map as a calibration tool prior to recording a sequence of THz images, we show a full recovery of a two-dimensional flat field for various combinations of magnification factors. Our results suggest that the implementation of dynamic intensity profile correction is a promising avenue for real-time electro-optical imaging of THz beams.

Quantum enhanced electro-optic sensor for E-field measurement

The measurement of intense E-field is a fundamental need in various research areas. An electro-optic (EO) sensor based on common path interferometer (CPI) is widely used due to its better temperature stability and controllability of optical bias. However, the small EO coefficient leads to poor sensitivity. In this paper, a quantum enhanced EO sensor is proposed by replacing the vacuum state in classical one with a squeezed-vacuum state. Theoretical analysis shows that the performance of the quantum enhanced EO sensor, including signal to noise ratio (SNR) and sensitivity, can always beat the classical one due to the noise suppression caused by the squeezed-vacuum state. Experimental results demonstrate that, there is still a 1.12dB quantum enhancement compared with the classical one when the degree of the squeezed-vacuum is 1.60dB. More importantly, except the increase of the EO coefficient or the optical power, the performance of the EO sensor can also be enhanced via quantum light source. Such a quantum enhanced EO sensor could be practically applied for the measurement of intense E-field.