抄録
We have developed a frequency-tunable continuous-wave (CW) terahertz (THz) light source using non-collinear phase matched difference frequency generation (DFG) based on excitation of phonon-polariton mode in gallium phosphide (GaP). Distributed feedback laser diode (DFB) and external cavity laser diode (ECLD) are used as excitation near-infrared light sources. THz wavelength can be tuned by changing the wavelength of DFB LD. The wavelength of DFB LD can be tuned from 1058nm to 1061nm by changing the temperature of its diffraction grating structure embedded in DFB laser diodes. The line width of each laser is less than 4MHz. The output power of two lasers is amplified up to 2W by using a polarization maintained (PM). ytterbium-doped fiber amplifier. CW THz wave source has superior features in the frequency resolution because of its narrow line width. As an example of high resolution THz spectroscopy, we have shown our recent results on non-destructive inspection of ultra high molecular weight polyethylene (UHMWPE) deformation.
