Continuous Wave Operation of SiO2 Sandwiched Colloidal CdSe/ZnS Quantum-Dot Microdisk Lasers

We report continuous wave operation of SiO
₂
sandwiched colloidal CdSe/ZnS quantum-dot microdisk lasers at room temperature. The SiO
₂
sandwiched quantum dot structure is formed first and then the disk patterns are defined by e-beam lithography. The benefits of introducing the sandwich structure are two folds: one to increase the confinement factor and the other to reduce the photo-oxidation of quantum dots. The luminescence stability of CdSe/ZnS quantum dots is much improved after they are sandwiched in silicon dioxide. We observe whispering gallery modes spatially and spectrally in the microdisks. We also fabricated Si
₃
N
₄
microdisks for comparison. The result shows that Si
₃
N
₄
microdisks are severely damaged when operating under continuous wave excitation while SiO
₂
microdisks demonstrate stable lasing behavior at the same excitation condition. Therefore, SiO
₂
microdisks are more suitable for high excitation and/or continuous wave applications such as lasers. This device structure shows great potentials to be applied to other wavelength in the visible range.