| 摘要 |
<P>PROBLEM TO BE SOLVED: To achieve a device and a method for accurately measuring spectral line width of a laser beam to be measured and for obtaining a beat signal with high SN ratio by suppressing saturation of a photodetector and reducing excessive noises in spectrum measurement of a laser beam by a ring type delayed self-heterodyne method. <P>SOLUTION: A spectrum measuring device using a delayed self-heterodyne method comprises: a circuital optical system 2 for inputting a laser source to be measured; an optical filter 8; and a photodetector 9a which receives the light from the optical filter and performs heterodyne detection to output a beat signal. The spectrum measuring device measures the spectral line width from the beat signal. The circuital optical system 2 comprises an optical directional coupler 3a, an optical frequency shifter 4 whose frequency shift is f<SB POS="POST">S</SB>, and a delay optical fiber 5. The optical filter 8 selectively outputs spectrum components of the laser source to be measured output from the circuital optical system 2 and spectrum components subjected to the frequency shift of Nf<SB POS="POST">S</SB>by the circuital optical system. <P>COPYRIGHT: (C)2012,JPO&INPIT |
