  The common terahertz time-domain spectroscopy (THz-TDS) based on
photoconductive antenna (PCA) needs two separate PCA chips. One PCA works as an
emitter, and the other works as a receiver. For a reflection-type measurement,
the technique called 'attenuated total reflection' usually is needed to enhance
the reflection sensitivity. These make the system bulk and complicated for the
reflection-type measurement. In this paper, we propose a novel THz-TDS
endoscope that is specifically designed for reflection-type measurement. This
THz-TDS endoscope is benefited from an integrated photoconductive antenna (we
call it iPCA), which integrates the emitter and receiver on a single antenna
chip. Therefore, the dimension of the endoscope can be shrunk as much as
possible for practical usage. We present the design and working principle of
this THz-TDS endoscope in details. It may open a promising way for the THz-TDS
application in biomedical fields.
