Real-time transmission-type terahertz microscope with palm size terahertz camera and compact quantum cascade laser

This paper describes a real-time transmission-type Terahertz (THz) microscope, with palm-size THz camera and compact quantum cascade laser (QCL). The THz camera contains 320x240 microbolometer focal plane array which operates at 30 Hz frame rate and has lock-in imaging function as well as integration functions such as frame integration and spatial filter. These functions are found very powerful in improving signal-to-noise ratio. QCL is installed in compact Stirling cycle cooler. A variety of QCLs covers frequency range from 1.5 to 5 THz and provides time-average power of 0.5~2 mW. The illumination area for sample is changed by adjusting one lens in the illumination optics. Performances of the THz microscope, such as signal-to-noise ratio and so on, were measured and are found consistent with the calculations. THz images taken with the THz microscope are finally presented.