Apparatus for real-time non-contact non-destructive thickness measurement using terahertz wave

An apparatus for real-time non-contact non-destructive thickness measurement using a terahertz wave, comprising:

• a wavelength-fixed laser generating first laser light having a first fixed wavelength λ1;
• a wavelength-swept laser generating second laser light having a second wavelength λ2 changed from a preset minimum wavelength to a preset maximum wavelength at a high speed for one period;
• a driver applying a voltage modulated at the same frequency as a wavelength sweep rate to the wavelength-swept laser to change the second wavelength from the minimum wavelength to the maximum wavelength for the one period;
• a coupler coupling the first laser light with the second laser light to form mixed light and splitting the mixed light into first mixed light and second mixed light;
• an emitter receiving the first mixed light split from the coupler to output a terahertz wave having a frequency fTHz=|f1−f2| corresponding to a difference between a frequency f1=c/λ1 (c is the speed of light in vacuum) corresponding to the first wavelength λ1 and a frequency f2=c/λ2 corresponding to the second wavelength λ2;
• a sample irradiated with the terahertz wave output from the emitter;
• a detector receiving the second mixed light split from the coupler and the terahertz wave transmitting or reflected from a sample to generate a photocurrent;
• a data acquisition unit converting the photocurrent into digital data to acquire and output the digital data;
• and
• a calculator generating frequency-domain data from the output digital data, performing fast Fourier transform on the frequency-domain data to generate time-domain data, and calculating a thickness of the sample on the basis of the time-domain data.