Semiconductor laser wavelength stabiliser - has noise voltage detected at photodetector, and has control circuit for temp. of and/or injection current through laser

摘要

The laser radiation of the semiconductor laser, whose emission wavelength is to be stabilised, is passed from the front or rear laser mirror through a dispersive optical element, or through an element whose transmission loss is wavelength-dependent. After passing through this element the laser radiation is received by a photodetector (3) whose noise voltage is also detected. The semiconductor laser (1) temperature and/or the injection current through this laser, is controlled by an electronic circuit (4) in such a manner as to keep the noise voltage, detected at the photodetector, at a minimum. Pref. this voltage is measured by a frequency exceeding 10 kHz, but smaller than 10 MHz. The lazer radiation may reach the photodetector through an optical filter of such type that the wavelength dependent transmission change will reach its maximum at the respective laser wavelength.