Studies on Active Monitoring Method Adopted to AR Coat Semiconductor Amplifiers

Abstract

It has been realized that the signal used to control the AR film deposition on the semiconductor diode facets with the active monitoring method (AMM) is related to the relative change of the output power P with respect to the injection current I, instead of P. In order to study the AMM, the rate equations have been employed to analyse the variation of dP/dl with the reflectivity of the facet being coated. The results reveal that the time evolution of the derivative during the film deposition follows almost the same pattern. This has led to the establishment of a new criterion aiding the control of the film deposition for the AMM and provided the possibility of making full use of the on-time information available with the AMM. The coating experiments have confirmed the theoretical predictions, and the reliability of the film control has also been improved substantially with the effective use of the new criterion.