We report the optical characteristics and the linewidth enhancement factor (α-factor) of InAs/GaAs quantum dot (QD) laser diodes (LDs) with a 5-μm-wide stripe and 1-mm-long cavity. Continuous wave (CW) operation of the laser yielded a kink-free output power of 160 mW with an external efficiency of 0.35 W/A. The threshold current was 28 mA and the lasing occurred at 1286 nm, solely at the ground state (GS) up to a current of 345 mA, without switching to the excited state (ES). Then, to estimate the α-factor of the LDs, we investigated the differential gain and wavelength shift versus the current. The differential gain was 2.37 cm-1/mA at 1286 nm, and the wavelength shift was 0.00046 nm/mA, which resulted in an α-factor of 0.057 at 1286 nm. The α-factor decreased with increasing wavelength. To the best of our knowledge, this is the lowest value of the α-factor that has been reported so far, indicating that our QD-LD has excellent beam quality under high-power operation due to the elimination of the filamentation.
- Differential gain
- Laser diodes (LDs)
- Linewidth enhancement factor
- Quantum dot (QD)
ASJC Scopus subject areas
- Computer Science Applications
- Electrical and Electronic Engineering