Low Harmonic Distortion DFB Laser for Broadband Analog Applications

$1.35~\mu $ m AlGaInAs/InP DFB lasers with low harmonic distortion and high frequency response bandwidth have been demonstrated for broadband analog applications. By optimizing active layers and setting Bragg wavelength 10 nm blue shifted of the gain peak wavelength, the device has a threshold current of 8.5 mA, 3-dB frequency response bandwidth of 21 GHz at 60 mA and 28GHz at 90 mA, second harmonic distortion of -23 dB and 1.5 ps group delay time up to a modulation frequency of 25 GHz. These highly linear and high frequency response bandwidth DFB lasers are realized for broadband analog applications and will become the key transmitters for the future 5G millimeter wave communication systems.