title: Gain-dependent linewidth enhancement factor in the quantum dot structures.
abstract: We measured the linewidth enhancement factor (alpha factor) of InAs quantum dot (QD) laser diodes (LDs) with two different QD structures. One is a normal QD LD with the same energy bandgap for each active QD layer, while the other is chirped with different energy bandgaps. The differential gain of the chirped InAs QD LDs is found to be about five times smaller than that of normal InAs QD LDs, whereas no overall wavelength shift with injection currents is observed in both QD LDs. The alpha factor is approximately five times higher in the chirped InAs QD LDs than in the normal InAs QD LDs. This relatively large alpha factor in the chirped InAs QD LDs is attributed to the asymmetrical, wide inhomogeneous gain profile.
authors.affiliation: Nano Device Research Center, Korea Institute of Science and Technology, Seoul, Korea.
authors.forename: Kyoung Chan
authors.initials: KC
authors.lastname: Kim
authors.forename: Il Ki
authors.initials: IK
authors.lastname: Han
authors.forename: Jung Il
authors.initials: JI
authors.lastname: Lee
authors.forename: Tae Geun
authors.initials: TG
authors.lastname: Kim