Interference fringes in the far field of short-external-cavity InGaAsP diode lasers: a method for longitudinal mode control.

Interference fringes in the far field of short-external-cavity InGaAsP diode lasers are discussed and explained. The interference occurs between light emitted from the front laser facet and light emitted from the rear laser facet that is reflected forward by the external mirror. The change in the relative phase of light emitted from each facet caused by a change in the longitudinal mode results in a shift of position of a portion of the fringes …