A broadband external cavity tunable InAs/GaAs quantum dot laser by utilizing only the ground state emission

A broadband external cavity tunable laser is realized byusing a broad-emitting spectral InAs/GaAs quantum dot (QD) gaindevice. A tuning range of 69~nm with a central wavelength of 1056nm, is achieved at a bias of 1.25~kA/cm^2 only by utilizing thelight emission from the ground state of QDs. This large tunablerange only covers the QD ground-state emission and is related to theinhomogeneous size distribution of QDs. No excited state contributesto the tuning bandwidth. The application of the QD gain device to theexternal cavity tunable laser shows its immense potential inbroadening the tuning bandwidth. By the external cavity feedback,the threshold current density can be reduced remarkably comparedwith the free-running QD gain device.