Impedance Characteristics of a Bi-section Gain Lever Laser Diode for 5G Applications

This paper reports the numerical evaluation of impedance response of a bi-section laser diode having multiple quantum wells, operating at 1.3 μm employing gain lever effect. The current in the absorber section is varied linearly for a fixed gain section current and parameters such as impedance, resonant frequency, bandwidth are computed by numerically solving the rate equations. A quarter-wavelength (λ/4) transmission line (QWT) is designed to perfectly match the laser diode to 50 Ω at 5G NR (new radio) C-band (3.3–5 GHz) centered at 4 GHz, for radio over fiber (RoF) applications. For the device under consideration, at a gain section current of 60 mA and absorber section current of 4 mA, the magnitude of intrinsic impedance was found to be 1.2 Ω at a frequency of 4 GHz. The bandwidth of the normalized modulation response was found to be 1.68 GHz. Also, gain lever laser diode showed 23.46% improvement in optical modulation index for its application in radio over fiber links, over the conventional single section laser diodes.