PHOTO DETECTOR AND OPTICAL DEVICE USED THE SAME

Disclosed in the present invention are a photo detector and an optical device including the same. The device includes: first and second lasers which generate first and second laser beams; an optical waveguide which is connected to the first and second lasers; and a photo detector which detects the first and second laser beams transmitted through the optical waveguide, wherein the photo detector includes: a substrate; a first impurity layer on the substrate; an absorption layer on the first impurity layer; and a second impurity layer on the absorption layer. The absorption layer generates terahertz waves by the beating of the first and second laser beams and is able to have a thickness less than 0.2 micrometer. [Reference numerals] (12) First laser;(14) Second laser;(30) Photodetector;(50) Output circuit