| 摘要 |
PURPOSE:To facilitate handling, realize high sesitivity, and stabilize wavelength for a long period, by synchronously detecting the detected signal of a photo detector and an AC signal applied to a pair of electrodes of a Fabry-perot resonator, and sending a wavelength control signal to a semiconductor laser, so as to reduce an error signal. CONSTITUTION:AC signal V1 is applied to electrodes 194, 195, and electric field Ex is generated in the X-axis direction, thereby lineally polarizing incident light S4 in the X-axis direction or the Y-axis direction. As a result, the incident laser light S4 to the Fabry-Perot resonator 19 is modulated so as to correspond with the Fabry-Perot resonant wavelength by the electrooptic effect r11 of quartz. A synchronous detector 27 obtains a product of the output v2 of a second photo detector 21 with reference to the AC input V1, and eliminates high frequency components, thereby performing synchronous detection. The detected result is outputted as an error signal to a feedback controller 28. The controller 28 multiples the input error signal by a specified feedback gain, and according to the value, changes the injection current for determining the oscillation wavelength of the semiconductor laser 11 and controls the error signal to be zero.
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