Laser spectral linewidth dependence on waveguide loss measurements using the Fabry–Perot method

The critical role of the optical source spectral linewidth in semiconductor low loss waveguide measurements using the Fabry–Perot resonance method is analyzed. For 5-mm-long GaAs/AlGaAs waveguides with losses in the 1 dB/cm range, a frequency stabilized single mode laser with a linewidth of less than 0.01 Å is required to obtain a loss value accurate to within 5%.