From amplified spontaneous emission to microring lasing using nanocrystal quantum dot solids

Malko, Anton V.; Mikhailovsky, Alexander; Petruska, Melissa A.; Hollingsworth, Jennifer A.; Htoon, Han; Bawendi, Moungi G.; Klimov, Victor I.

doi:10.1063/1.1497708

Cited by 254 publications

(245 citation statements)

References 13 publications

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“…S4 †). In addition, although NR 6 has the longest CdS rod length, we achieved almost the same amount ($8 nm) of blue-shied ASE from NR 6 when compared to NR 5 . It is also shown that both NR 5 and NR 6 have the same radiative lifetime, which conrms that photoluminescence lifetimes are a good indicator of connement.…”

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confidence: 70%

Type-tunable amplified spontaneous emission from core-seeded CdSe/CdS nanorods controlled by exciton–exciton interaction

et al. 2014

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Type-tunable optical gain performance of core-seeded CdSe/CdS nanorods is studied via two-photon optical pumping. Controlling the Colloidal semiconductor nanocrystals have recently arisen as promising candidates to be utilized as active gain media for lasing applications. 1,2 With their band gap tunability (via size and shape modications), efficient band edge emission (even at room temperature), discrete band structure, and synthesis through facile wet-chemistry, it is possible to achieve colortunable, low-threshold, temperature insensitive and solution processed lasers from colloidal quantum dots (CQDs). [2][3][4][5][6] However, there are various problems and challenges associated with CQD-based lasers. One way of achieving stimulated emission from the CQDs is through multi-exciton generation. When multiple excitons are formed, the Auger recombination (AR) process becomes more pronounced and inhibits optical gain in CQDs. [7][8][9] In addition, high intensity optical pumping, which is required for stimulated emission, can photo-damage the sample and decrease the stability. 10 To address these issues, CQDs having suppressed AR and exhibiting a higher absorption cross-section, which can increase the stability of CQDs by lowering the optical gain threshold, are strongly required.As a subclass of nanocrystals, core/shell nanorods (NRs) have been extensively considered for lasing applications and optical gain studies to overcome these problems with possibility of engineering their electronic structure for longer gain lifetime and increased absorption cross-section. 11-14 From different varieties of core/shell NRs, core-seeded CdSe/CdS NRs have become quite attractive. With advances in the colloidal synthesis of CdSe/CdS core/shell NRs, it is possible to synthesize highly efficient and crystalline CdSe/CdS core/shell NRs having a narrow size distribution by nely controlling their shape and size. 15,16 Furthermore, due to shallow band offset for electrons in the CdSe/CdS core/shell material system, a partial separation of electron and hole wavefunctions is observed which is known as the quasi type-II electronic structure that contributes to the suppression of Auger recombination, which is highly critical for achieving lasing. 11,[16][17][18] The other advantage of having a lower energy barrier for electrons in CdSe/CdS NRs is that, by simply changing their core and shell sizes, it is possible to tailor the electron and hole wavefunction overlap and tune CdSe/CdS NRs from type-I-like to quasi-type-II-like band alignment, which can be an important design consideration when engineering the gain/loss mechanisms in practical lasing systems. [19][20][21][22][23] Moreover, due to the narrower band gap of CdS with respect to ZnS, the absorption cross-section of CdSe/CdS core/shell NRs is greatly enhanced. 13 With all of these aforementioned promises, in the nanocrystal lasing context, CdSe/CdS NRs have become one of the most heavily studied materials systems. 18,24 Recently, singlemode, single-exciton and tunable laser emis...

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confidence: 70%

Type-tunable amplified spontaneous emission from core-seeded CdSe/CdS nanorods controlled by exciton–exciton interaction

et al. 2014

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“…A linear fi t was used to account for the change in PL intensity as a function of excitation stripe length prior to optical amplifi cation [ 4 ] while the onset and subsequent saturation of the ASE intensity was fi tted with a previously reported 1-D amplifi er model: [ 6 , 15 ] I ∝ e gla 1 − e −(z−z 0 ) la used to explicate the absence and presence of ASE in short and long CdSe seeded CdS nanorods respectively, [ 21 ] given that in our case the dimensions of the CdS arms in both small and large core tetrapods as well as their volume fractions in the fi lm are comparable. One plausible explanation would be to consider an exciton blocking effect in which the small CdSe core is populated with a high density of excitons at suffi ciently large excitation intensities such that the electrons and holes photogenerated in CdS do not experience a strong driving force for relaxing into the CdSe core, thus recombining radiatively.…”

Section: Doi: 101002/adma201200121mentioning

confidence: 99%

Low Threshold, Amplified Spontaneous Emission from Core‐Seeded Semiconductor Nanotetrapods Incorporated into a Sol–Gel Matrix

et al. 2012

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“…1 These particles cover the visible to near-infrared spectral range and have important potential applications in biology and electro-optical devices. [2][3][4][5][6][7] Such electro-optic devices rely on the conversion of light into excited electrons and holes (excitons) and vice versa, and knowledge of the processes immediately following photoexcitation is therefore essential for these applications, in addition to the fundamental interest in exciton and charge dynamics in QDs.…”

Section: Introductionmentioning

confidence: 99%

Carrier Multiplication and Its Reduction by Photodoping in Colloidal InAs Quantum Dots

et al. 2007

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Carrier (exciton) multiplication in colloidal InAs/CdSe/ZnSe core-shell quantum dots (QDs) is investigated using terahertz time-domain spectroscopy, time-resolved transient absorption, and quasi-continuous wave excitation spectroscopy. For excitation by high-energy photons (∼2.7 times the band gap energy), highly efficient carrier multiplication (CM) results in the appearance of multi-excitons, amounting to ∼1.6 excitons per absorbed photon. Multi-exciton recombination occurs within tens of picoseconds via Auger-type processes. Photodoping (i.e., photoinjection of an exciton) of the QDs prior to excitation results in a reduction of the CM efficiency to ∼1.3. This exciton-induced reduction of CM efficiency can be explained by the twofold degeneracy of the lowest conduction band energy level. We discuss the implications of our findings for the potential application of InAs QDs as light absorbers in solar cells.

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From amplified spontaneous emission to microring lasing using nanocrystal quantum dot solids

Cited by 254 publications

References 13 publications

Type-tunable amplified spontaneous emission from core-seeded CdSe/CdS nanorods controlled by exciton–exciton interaction

Type-tunable amplified spontaneous emission from core-seeded CdSe/CdS nanorods controlled by exciton–exciton interaction

Low Threshold, Amplified Spontaneous Emission from Core‐Seeded Semiconductor Nanotetrapods Incorporated into a Sol–Gel Matrix

Carrier Multiplication and Its Reduction by Photodoping in Colloidal InAs Quantum Dots

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