TUNING SYSTEM FOR EXTERNAL CAVITY DIODE LASER

摘要

A tunable external cavity semiconductor laser is provided with a semiconductor laser diode, a diffraction grating and a movable mirror. The diode laser is positioned to illuminate a diffraction grating and a movable mirror is positioned to reflect a selected wavelength back into the cavity. The mirror is mounted on a pivot so positioned to provide simultaneous rotation and linear translation. The pivot point is selected so as to provide an internal cavity length which is exactly an integral number of half wavelengths at three different wavelengths and an exceptionally close (within 1/1000 of one wavelength) match at all other wavelengths within the tuning range. Significantly, the pivot point calculation takes into account the effect of the dispersion of the laser and other optical elements in the system on the cavity length. These elements are usually a small part of the physical length of the cavity, but their greater dispersion makes their contribution to the number of half wavelengths in the resonant cavity very significant.