Ultralow-Threshold Two-Photon Pumped Amplified Spontaneous Emission and Lasing from Seeded CdSe/CdS Nanorod Heterostructures

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• 作者：Guichuan Xing ; Yile Liao ; Xiangyang Wu ; Sabyasachi Chakrabortty ; Xinfeng Liu ; Edwin K. L. Yeow ; Yinthai Chan ; Tze Chien Sum
• 刊名：ACS Nano
• 出版年：2012
• 出版时间：December 21, 2012
• 年：2012
• 卷：6
• 期：12
• 页码：10835-10844
• 全文大小：570K
• 年卷期：v.6,no.12(December 21, 2012)
• ISSN：1936-086X

文摘

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 (蟽₂) through varying the CdS rod size, and that of the emission wavelength through varying the CdSe dot size. With an enhanced 蟽₂, 2ASE in these heterostructures is achieved with an ultralow threshold fluence of 1.5 mJ/cm², 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 (蟽₂畏) (where 畏 is the quantum yield) was found and validated over a wide volume range for II鈥揤I 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.

Keywords:

CdSe/CdS nanorod; upconversion; whispering gallery mode lasing; two-photon absorption; ultrafast