A simple and accurate method for measuring the front facet modal reflectivity of a Fabry–Perot laser diode is presented. In this method, optical feedback from an external mirror of known reflectivity, <i>R</i><sub>ext</sub>, is used to alter the laser diode threshold current. The effect of the external mirror and front facet reflectivities on the threshold current then allows for a measurement of the front facet modal reflectivity of the laser diode and is theoretically and experimentally studied. This method was used to measure a facet reflectivity of <i>R</i><sub>2</sub> = 0.0151(+0.0018/−0.0032) [<i>R</i><sub>2</sub> = 0.00592(+0.00085/−0.00123)] for a commercially antireflection-coated facet of a laser diode with a center wavelength of 795 nm (935 nm). The results of the reflectivity measurements based on the threshold current as a function of the external mirror reflectivity are compared with the results of the reflectivity measurements based on modulation depth of the optical spectrum [IEEE J. Quantum Electron. <b>QE-19,</b> 493 (1983)].
© 2000 Optical Society of America
Kevin S. Repasky, Gregg W. Switzer, Casey W. Smith, and John L. Carlsten, "Laser Diode Facet Modal Reflectivity Measurements," Appl. Opt. 39, 4338-4344 (2000)