Stimulated emission from PbS‐quantum dots in glass matrix

Yue, Fangyu; Tomm, Jens W.; Kruschke, Detlef; Glas, P.

doi:10.1002/lpor.201200075

Cited by 11 publications

(12 citation statements)

References 27 publications

(30 reference statements)

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“…Even more important, the integral intensity of the fast component depends in a superlinear way on excitation, as shown in Figure d, which shows a threshold‐like excitation value at 20 μJ · cm −2 ; and the fast component shows no dependencies of excitation, and even temperature, therefore, the fast component with a typical decay time of ∼40 ps could account for amplified spontaneous emission (ASE). This is consistent with the observation of stimulated emission in PbS:Glass material system …”

supporting

confidence: 92%

“…Our measurements at high excitation levels, however, provided a number of unexpected findings, in particular, if one compares our actual findings with those from an earlier study on highly excited PbS:Glass that was carried out with comparable methodology . There, we found stimulated emission located at almost the same spectral position, where the ground‐state absorption peaked.…”

supporting

confidence: 69%

“…All in all, our results indicate a rather complex situation. Although the ASE or even stimulated emission is observed from the excited states in PbSe:Glass, the absence of ground‐state stimulated emission or ASE is in striking contrast to the situation in PbS:Glass . Probably this is due to a more flat shape of the density of states in PbSe:Glass compared to PbS:Glass.…”

mentioning

confidence: 91%

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Emission Kinetics from PbSe Quantum Dots in Glass Matrix at High Excitation Levels

Hong

Wang

Yue

et al. 2018

Physica Rapid Research Ltrs

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The photoluminescence dynamics of PbSe quantum dots in a glass matrix (PbSe:Glass) is investigated at high excitation levels. Up to 470 meV blue‐shifted emissions are observed, which are assigned to excited‐state emission populated by carrier accumulation. Rapid photoluminescence decays of ∼25–40 ps are observed. Together with a threshold‐like dependence on excitation, even at room temperature, this component is tentatively attributed to amplified spontaneous emission. The absence of stimulated emission from the ground state and the overall higher threshold compared to PbS:Glass suggest that there are more intrinsic restrictions on the use of PbSe:Glass as a laser material than for PbS:Glass.

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confidence: 92%

supporting

confidence: 69%

mentioning

confidence: 91%

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Emission Kinetics from PbSe Quantum Dots in Glass Matrix at High Excitation Levels

Hong

Wang

Yue

et al. 2018

Physica Rapid Research Ltrs

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“…55 In this section, we will address the mechanisms of stimulated emission and the accompanied spontaneous emission as well as the influence of excitation density and/or temperature on the recombination. Figure 9(a) shows transient PL data as obtained at 5 K by pulsed excitation at 785 nm (80 MHz).…”

Section: Stimulated Emission At High Excitation Densitiesmentioning

confidence: 99%

Spontaneous and stimulated emission dynamics of PbS quantum dots in a glass matrix

2013

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Optical properties and relaxation mechanisms of PbS quantum dots in glass matrix (PbS:Glass) have been systematically investigated by transmission and (steady-state and transient) photoluminescence spectroscopy. Key parameters are determined by combining the data with semiempirical expressions, based on which the recombination mechanisms including spontaneous and stimulated emissions have been discussed as a function of temperature by referring to a multilevel model including intrinsic (or band-to-band transition), bright, dark, and ground states. The results disclose that (i) the existence of a dark exciton state is the main reason for thermal quenching of the emission even at low temperatures due to the strong multiacoustic phonon coupling, (ii) the "intrinsic" spontaneous emission related to the intrinsic state is observed with an approximately nanosecond lifetime, in contrast to the "regular" spontaneous emission from the bright exciton state with an approximately microsecond lifetime, and (iii) stimulated emission, which has a lifetime of 20-40 ps and shows power-dependence of excitation density (or temperature), only appears from the intrinsic state but not the (bright) exciton state when enough accumulation of photogenerated carriers is reached. Furthermore, we find that the thermal conductivity will become crucial for future PbS:Glass related optoelectronic device applications.

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“…2(d) and the corresponding description in the text (e.g., τ C < τ B < τ A ) as well as the previous attribution of peak A to the intrinsic E g of QDs, τ 3 points to a μs lifetime typically for a ground-state-related lifetime in such QDs (i.e., peak A in Fig. 1); see reports on spontaneous emission lifetimes of PbS QDs [9,23,24]. Figure 3(b) summarizes the temperature dependencies of the lifetimes τ i (i = 1, 2, 3).…”

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confidence: 96%

Experimental observation of exciton splitting and relaxation dynamics from PbS quantum dots in a glass matrix

2014

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Multiple optical transitions from PbS quantum dots (QDs) in glass matrix are observed. Energy separations between them amount up to ∼200 meV. Instead of being due to a size distribution of QDs, they are found to be related to a splitting of the lowest exciton levels. Systematic analysis of the relaxation dynamics reveals the lifetimes of the split states ranging from sub-100-ns to ∼μs. Moreover, we observe excited and "intrinsic" states having a sub-100-ps and ∼ns lifetime, respectively. The behavior of the split structure can be modeled by a phonon-assisted relaxation mechanism. This investigation offers a conclusive interpretation for the wide distribution of experimentally observed nonequilibrium carrier lifetimes in PbS QDs.Lead salt (e.g., PbS) quantum dots (QDs) have been widely investigated for applications in optoelectronic devices [1,2]. The QDs are either colloidal or embedded into a glass matrix. The latter provides substantial advantages in terms of longterm stability [3]. In order to evaluate and improve the properties of materials or devices, the QD size and its distribution as well as the excitonic lifetime are major issues, which should be accurately characterized, e.g., directly by optical methods including steady-state (SS) or transient absorption and photoluminescence (PL) spectroscopy at room temperature [4].However, in rock salt PbS QDs the dimension of the excitonic manifold is theoretically 64 because both the valence-band maximum and the conduction-band minimum originate from the 8-fold (including spin) L valleys in the first Brillouin zone of bulk PbS. The degeneracy of these L valleys becomes lifted due to, e.g., intervalley coupling, interband coupling, and electron-hole Coulomb and exchange interaction [5]. Another mechanism potentially acting into this direction is external forces such as pressure as well as a special chemical surrounding, e.g., in a matrix. The split structure makes the optical transition in QDs complex and affects the characterization of QD features including the lowest excitonic transition energy (for simplicity called E g ) and subsequently the size and distribution of QDs as well as the nonequilibrium carrier recombination mechanism. In spite of the fact that asymmetric-or multi-PL (or absorption) peaks from these kinds of QDs have been observed even at room temperature, no direct reports involve these split states. Typically extrinsic assumptions are made including size distribution (e.g., multimodal QDs) [6], temperature/excitation-induced broadening [7], or defect states [8,9].In this Rapid Communication, PbS QDs embedded in a borosilicate glass matrix are prepared and characterized by SS-or transient-PL spectroscopy at low excitation densities and temperatures. A three-transition structure from the QDs is observed with an energy separation up to 200 meV, in dependence of growth conditions including annealing. The * yue@mbi-berlin.de intrinsic mechanism for this three-transition structure that seems to be sensitive to the host matrix, e.g., with borosilicate b...

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Stimulated emission from PbS‐quantum dots in glass matrix

Cited by 11 publications

References 27 publications

Emission Kinetics from PbSe Quantum Dots in Glass Matrix at High Excitation Levels

Emission Kinetics from PbSe Quantum Dots in Glass Matrix at High Excitation Levels

Spontaneous and stimulated emission dynamics of PbS quantum dots in a glass matrix

Experimental observation of exciton splitting and relaxation dynamics from PbS quantum dots in a glass matrix

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