Optical spectrum analyzer

An optical spectrum analyzer comprising:

• (i) an optical waveguide formed of a material allowing propagation of surface acoustic waves therethrough,
• (ii) a surface acoustic wave generating means for generating a surface acoustic wave, including means for changing a frequency of said surface acoustic wave continuously, wherein said surface acoustic wave advances in a direction intersecting an optical path of a guided optical wave as light-to-be analyzed entered to said optical waveguide and advancing inside of said optical waveguide and diffracts and deflects said guided optical wave, in said optical waveguide,
• (iii) a focusing grating coupler for converging and radiating said diffracted and deflected guided optical wave,
• (iv) a light detection means for detecting the optical level of said guided optical wave, deflected by said surface acoustic wave and radiated out of said optical waveguide, said light detection means including a pinhole plate for receiving an output of said focusing grating coupler and having a pinhole formed therein through which at least a portion of the optical wave converged by said optical grating coupler passes, said light detection means receiving said portion and detecting said optical level accordingly, and
• (v) a frequency detection means for detecting the frequency of said surface acoustic wave at the time said light detection means detects the optical level of said optical wave guided, deflected by said surface acoustic wave and radiated out of said optical waveguide.