Optical power monitor for two‐beam laser diodes using electric operational circuits

Abstract

AbstractThis paper presents a method for monitoring individual laser beams from an array‐type, two‐beam laser diode with two emission points in one laser chip using an electric operational circuit. the characteristics of the two‐beam monitoring system are evaluated by experiment. This system analytically monitors optical output powers on the principle that the two laser beams are received at different ratios by a photodiode having two detecting surfaces located near the laser facet. the main feature of the system is the possibility of signal separation using a simple circuit configuration and adjustmentfree arrangement of the photodiode.Evaluation of a trial two‐beam monitoring circuit has revealed that a gain deterioration of 3 dB is exhibited at 1 MHz. Crosstalk, which represents the degree of signal separation, depends on frequency and is ‐54 dB at 10 kHz and ‐23 dB at 1 MHz, exhibiting excellent separation characteristics. These results can be used without problems in optical disk drives incorporating two‐beam laser diodes. Thus, they demonstrate the effectiveness and practicality of the proposed system.