title: Ultralow-threshold two-photon pumped amplified spontaneous emission and lasing from seeded CdSe/CdS nanorod heterostructures.
abstract: Ultralow-threshold two-photon pumped amplified spontaneous emission (2ASE) and lasing in seeded CdSe/CdS nanodot/nanorod heterostructures is demonstrated for the first time. Such heterostructures allow the independent tunability of the two-photon absorption (2PA) cross-section (σ(2)) through varying the CdS rod size, and that of the emission wavelength through varying the CdSe dot size. With an enhanced σ(2), 2ASE in these heterostructures is achieved with an ultralow threshold fluence of ~1.5 mJ/cm(2), which is as much as one order less than that required for spherical semiconductor NCs. Importantly, by exploiting this unique property of the seeded nanorods exhibiting strong quantum confinement even at relatively large rod sizes, a near reciprocal relation between the 2ASE threshold and the 2PA action cross-section (σ(2)η) (where η is the quantum yield) was found and validated over a wide volume range for II-VI semiconductor nanostructures. Ultrafast optical spectroscopy verified that while the Auger processes in these heterostructures are indeed suppressed, ASE in these samples could also be strongly affected by a fast hole-trapping process to the NR surface states. Lastly, to exemplify the potential of these seeded CdSe/CdS nanodot/nanorod heterostructures as a viable gain media for achieving two-photon lasing, a highly photostable microsphere laser with an ultralow pump threshold is showcased.
authors.affiliation: Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371.
authors.forename: Guichuan
authors.initials: G
authors.lastname: Xing
authors.forename: Yile
authors.initials: Y
authors.lastname: Liao
authors.forename: Xiangyang
authors.initials: X
authors.lastname: Wu
authors.forename: Sabyasachi
authors.initials: S
authors.lastname: Chakrabortty
authors.forename: Xinfeng
authors.initials: X
authors.lastname: Liu
authors.forename: Edwin K L
authors.initials: EK
authors.lastname: Yeow
authors.forename: Yinthai
authors.initials: Y
authors.lastname: Chan
authors.forename: Tze Chien
authors.initials: TC
authors.lastname: Sum
mesh_terms: D019187:Cadmium Compounds / Q000737:chemistry*; D007834:Lasers; D043942:Nanotubes / Q000737:chemistry*; D055620:Optical Phenomena; D017785:Photons; D018036:Selenium Compounds / Q000737:chemistry*; D013057:Spectrum Analysis; D013440:Sulfides / Q000737:chemistry*
chemical_list: D019187:Cadmium Compounds; D018036:Selenium Compounds; D013440:Sulfides; C034939:cadmium sulfide; C058667:cadmium selenide