Modulation of High-Intensity Optical Properties in CdS/CdSe/CdS Spherical Quantum Wells by CdSe Layer Thickness

Area of Science:

• Materials Science
• Quantum Optics
• Nanotechnology

Background:

• Spherical quantum wells (SQWs) suppress Auger recombination due to larger confinement volumes.
• Understanding factors influencing SQW high-intensity optical properties like multiexciton and nonlinear optical properties is crucial for optimization.

Purpose of the Study:

• Investigate the impact of CdSe shell thickness variations in CdS/CdSe/CdS SQWs.
• Analyze the modulation effects on photoluminescence (PL) properties, defect distribution, biexciton binding energy, and third-order optical nonlinearities.
• Evaluate the influence on multiexciton properties and optical gain.

Main Methods:

• Fabrication of CdS/CdSe (xML)/CdS SQWs with varied CdSe layer thicknesses.
• Characterization of PL properties, defect distribution, and biexciton binding energy.
• Measurement of third-order optical nonlinearities and optical amplification under one- and two-photon excitation.

Main Results:

• The CdS/CdSe(3ML)/CdS sample demonstrated a high volume-normalized two-photon absorption cross-section (18.17 × 10^2 GM/nm^3).
• Optical amplification was achieved under both one-photon (400 nm) and two-photon (800 nm) excitation.
• Novel amplified spontaneous emission spectra were observed under one/two-photon excitation, attributed to thermal effects exceeding biexciton binding energy.

Conclusions:

• CdSe shell thickness significantly modulates the optical properties of CdS/CdSe/CdS SQWs.
• Optimized SQWs exhibit promising multiexciton gain characteristics and potential for optical gain applications.
• The findings offer valuable insights for designing advanced quantum well structures for optoelectronics.