| 摘要 |
PROBLEM TO BE SOLVED: To make it possible to observe the waveform at an excellent signal-to- noise ratio (SN) even if the frequency of an optical signal is high by mounting a photodiode, a short-pulse generating means, a sampling circuit and the like on a common substrate. SOLUTION: A groove 11 is formed in an electrode 20 formed on the surface of a semi-insulating substrate 10 such as GaAs. A transmission line 21 is formed at the central position of the groove. Then, light under observation OS is applied on a photodiode D1 and transduced into the electric signal, and the signal is inputted into a sampling circuit 30. The sampling circuit 30 outputs the potential of the signal under observation at this time to an output terminal 23 at every time when a short pulse SP having a narrow pulse width, which is outputted from a short-pulse generating means 40, is supplied. In this way, the optical signal is transduced into the electric signal on the same semi-insulating substrate 10, the electric signal is sampled in the sampling circuit 30, the signal is transduced into the electric signal having the frequency lower than that of the optical signal and the signal is outputted. Therefore, the observed signal having the excellent SN ratio can be inputted to a waveform observing apparatus at a low loss. |
