Analysis of red-shift in SMFP-LD with positive and negative wavelength detuning

Abstract

Optical injection in the semiconductor laser has been widely investigated in digital optical signal processing and microwave photonics. Red-shift is a typical nonlinear physical phenomenon in semiconductor lasers due to external beam injection. In this paper, we analyze the physical principle of the red-shift when an external beam is injected into a single mode Fabry-Perot laser diode (SMFP-LD). In our scheme, we observe the range of the red-shift in an SMFP-LD with respect to the change in power of the injected beam by measuring the variation of the RF signal generated by optical beating the injected beam and the corresponding longitudinal mode of the SMFP-LD. We measure the red-shift due to the power variation of the injected beam with both positive and negative wavelength detuning. At first, the wavelength detuning is made constant and later on, the wavelength detuning is varied to find the behavior of red-shift due to different wavelength detuning. In addition, the dependence of red-shift on the mode of the SMFP-LD, where the external beam is injected, is also analyzed. The variation in the red-shift due to change in the power of the injected beam is used to generate microwave signal with different frequencies at the output. Based on the output results of the variation of the red-shift and the output microwave signal, whether it is a linear or non-linear curve, the analysis can be utilized on different applications in the microwave photonics that includes 5G communication, radar applications, military communication, and many others.