Characterization method and test device for near-field terahertz THz time domain spectrum

Abstract

The invention relates to a characterization method and a test device for a near-field terahertz THz time domain spectrum. The characterization method comprises the following steps: a near infrared femtosecond pulse laser beam which is radiated by a femtosecond laser source is split into a pump light path and a detection light path by an optical beam splitter; pump light is modulated by an opticalchopper, and excites a solid terahertz emitting source or a test sample in a nanoscale quasi one-dimensional structure so as to generate terahertz wave signals required by spectral analysis; detection light passes through an optical delay line and a necessary transmission light path, is superposed with the pump light path on a terahertz detection crystal, and samples terahertz signals; the terahertz signals sampled by the detection light pass through a quarter wave plate and a Wollaston prism and is split into P light and S light, the P light and the S light are put into the input end of a difference photodiode, the small signal output end of the difference photodiode outputs differential signals, and the differential signals are processed (amplified and subjected to analog-to-digital conversion) by a lock phase signal amplifier, wherein synchronous frequency signals of the lock phase amplifier come from the optical chopper; and the processed signal data are transmitted to a computer for further processing and operational analysis.

Description

technical field [0001] The invention relates to a near-field terahertz THz time-domain spectral characterization method applied to a quasi-one-dimensional nanostructure semiconductor or metal material and a testing device thereof. Background technique [0002] Usually, most THz time-domain spectroscopy systems THz-TDS systems use the measurement of THz THz transmission or reflection signals in the far field, which is mainly due to the shape of the test sample itself (block material, polymer material etc.) and the existing terahertz THz detection optical path limits the near-field approach. In far-field conditions, due to the existence of diffraction phenomena, the spatial resolution of THz-TDS and THz imaging systems is greatly limited. In the research of nanoelectronic devices, people urgently need to understand the process of exciton generation and separation, free charge transport, and capture of quasi-one-dimensional nanostructured semiconductor or metal materials, and ...

AI Technical Summary

Problems solved by technology

[0003] In the past few years, people tried to use aperture (Aperture) technology to realize the measurement of terahertz THz signal in the near-field mode, but as the aperture diameter shrinks, the energy of terahertz THz light signal also decreases sharply, which is likely to be affected by the background noise. Submerged, it is not conducive to improving the signal-to-noise ratio of the system

In recent years, many researchers refer to Scanning Near-field Optical Microscopy (SNOM) to develop the THz-SNOM method of THz near-field scanning microscopy, which improves the resolution to THz light. Half or even one tenth of the wavelength, the effect is obvious, but this method has a low signal-to-noise ratio, a complex system structure, and a very expensive cost

Images