The dynamics of amplified spontaneous emission in CdSe∕ZnSe quantum dots

Abstract

We have used the variable stripe technique and pump-probe spectroscopy to investigate both gain and the dynamics of amplified spontaneous emission from CdSe quantum dot structures. We have found modal gain coefficients of 75 and 32 cm −1 for asymmetric and symmetric waveguide structures, respectively. Amplified spontaneous emission decay times of 150 and 300 ps and carrier capture times of 15 and 40 ps were measured for the structures with high and low material gains respectively. The difference in the capture times are related to the fact that for the symmetric waveguide, carriers diffuse into the active region from the uppermost ZnMgSSe cladding layer, yielding a longer rise time for the pump-probe signals for this sample.

Ultrafast Charge Carrier Dynamics and Nonlinear Optical Absorption of InP/ZnS Core–Shell Colloidal Quantum Dots

“…The rise time is determined by fitting the rising process with the Boltzmann sigmoidal function where B 1 is the initial value, B 2 is the final value, t s indicates the time center, and τ R represents the time constant for the rising process. The rise time (τ R ) for FX obtained from the fitting is 101 ± 5 ps (results shown in Figure a), which value is larger than that in CdSe QDs (20–40 ps). , The decay curve of the QD samples can be well-fitted by a double-exponential function where I b represents the noise. The fitting results are plotted as solid lines in Figure a.…”

“…The rise time (τ R ) for FX obtained from the fitting is 101 ± 5 ps (results shown in Figure 4a), 39 which value is larger than that in CdSe QDs (20−40 ps). 40,41 The decay curve of the QD samples can be well-fitted by a double-exponential function 38…”

Size Dependent Optical Properties of CdSe Nanocrystals at Low Temperature

“…The emission color of CdSe NCs can be covered in the whole visible range depending on size variations. With these interesting properties, CdSe NCs can become an ideal candidate for optoelectronics such as light-emitting diodes, laser, and bio-sensors [8][9][10][11][12][13][14][15]. In particular, CdSe NCs obtained a higher density of electronic states near the edges of valence and conduction bands compared to bulk semiconductors.…”

Vertically oriented self-assembly of colloidal CdSe/CdZnS quantum wells controlled via hydrophilicity/lipophilicity balance: optical gain of quantum well stacks for amplified spontaneous emission and random lasing

“…16 Since ASE is an effective indicator to compare the material capability for optical gain, the ASE behaviors of different types of colloidal nanocrystals have been investigated. 19,30–33 Such laterally oriented self-assembly of CQWs has paved the way for the development of ultrathin optical gain media with tunable thickness, thanks to the excellent uniformity and close-packed nature of their films. 16…”

“…16 Since ASE is an effective indicator to compare the material capability for optical gain, the ASE behaviors of different types of colloidal nanocrystals have been investigated. 19,[30][31][32][33] Such laterally oriented self-assembly of CQWs has paved the way for the development of ultrathin optical gain media with tunable thickness, thanks to the excellent uniformity and close-packed nature of their films. 16 Herein, different from our previous work, we propose and demonstrate vertically oriented self-assembled monolayer (SAM) film formation of CdSe/CdZnS CQWs by controlling the hydrophilicity/lipophilicity balance of their subphase by using a binary subphase.…”