Polarization features of optically pumped CdS nanowire lasers

Abstract

Abstract. High quality CdS nanowires suspended in air were optically pumped both below and above the lasing threshold. The polarization of the pump laser was varied while the nanowire emission was monitored in a 'head-on' measurement geometry. Highest pump-efficiency and most efficient absorption of the pump radiation are demonstrated for an incident electric field being polarized parallel to the nanowire axis. This polarization dependence was observed both above the lasing threshold and in the regime of amplified spontaneous emission. Measured Stokes parameters of the nanowire emission reveal that due to the onset of lasing the degree of polarization rapidly increases from approximately 15% to 85 %. Both, Stokes parameters and degree of polarization of the nanowire lasing emission are independent of the excitation polarization.

Light-matter interaction and lasing in semiconductor nanowires: A combined finite-difference time-domain and semiconductor Bloch equation approach

“…5(e-g), the mode dynamics after the onset of lasing can be observed. As predicted from linear calculations, 30 the field profiles of wires of the investigated diameter range are dominated by the HE21 mode, which has a high modal reflectivity as well as a high confinement factor. However, the field profile is fluctuating between the individual timesteps, indicating an admixture of additional transverse modes.…”

Ultrafast Dynamics of Lasing Semiconductor Nanowires

“…This behavior is likely caused by a switching from single transverse (HE 11 ) mode lasing towards high order (TE 01 ) mode lasing in thicker wires. The abrupt increase in pulse width for the CdS NW lasers occurs at a diameter of ~ 180 nm, which fits with our interpretation of this transition [20]. Note, that the three thickest CdS…”

“…NWs exhibit diameters providing efficient mode confinement even to additional higher order modes (such as HE 21 , TM 01 ) [20]. The expected multi high order mode lasing or mode competition can drastically affect the output pulse width.…”

Nanowire Lasers

“…For instance, a large confinement factor (Γ > 0.8) can be achieved in a nanowire with a sufficiently large triangular cross section for the TE 01 mode [90]. We note that producing a large confinement factor is only meaningful when the polarization of the electromagnetic guided mode matches the polarization of the dipole transition of the semiconductor nanostructure [85]. Both the crystalline structure (wurtzite and zincblende) and the dielectric mismatch between the wires have been demonstrated to cause optical anisotropy, which greatly impacts the polarization of the light emitted from the wire [86].…”