Laser diode facet modal reflectivity measurements

A simple and accurate method for measuring the front facet modal reflectivi ty of a Fabry-Perot laser diode is presented. In this method, optical feedb ack from an external mirror of known reflectivity, R-ext, is used to alter the laser diode threshold current. The effect of the external mirror and fr ont facet reflectivities on the threshold current then allows for a measure ment of the front facet modal reflectivity of the laser diode and is theore tically and experimentally studied. This method was used to measure a facet reflectivity of R-2 = 0.0151(+0.0018/-0.0032) [R-2 = 0.00592(+0.00085/-0.0 0123)] for a commercially antireflection-coated facet of a laser diode with a center wavelength of 795 nm (935 nm). The results of the reflectivity me asurements based on the threshold current as a function of the external mir ror reflectivity are compared with the results of the reflectivity measurem ents based on modulation depth of the optical spectrum [IEEE J. Quantum Ele ctron. QE-19, 493 (1983)]. (C) 2000 Optical Society of America OCIS codes: 140.2020, 120.5700, 130.5990.