Core-shell colloidal nanorods are a very interesting material for light emitting applications due to their bright and polarized luminescence. This system has great advantages for optically pumped light emitting devices since the excitation light is efficiently harvested by the large rod-shaped shell, and the photo-excited carriers recombine after fast relaxation under emission of light from the strongly quantum confined exciton ground state of the spherical core. We recently discovered that dense layers of such nanorods do not only exhibit amplified spontaneous emission from the core, but also from the shell material.
We demonstrated single mode laser action from core-shell CdSe/CdS nanorods that self-assembled into micro-resonators via coffee stain evaporation dynamics. To fabricate the resonators we deposited picoliter quantities of nanorod solution onto planar glass substrates. The peculiar microfluidics in such a tiny evaporating droplet resulted in densely packed micron-size stripes of nanorods with amazingly smooth lateral borders. Optical pumping of such stripes at record-low pump fluences resulted in laser emission with a line width of less than one nanometer. We were able to obtain lasing from core and shell states and therefore can span the spectral range from 490-650 nm with a single emitting material system. Our self-assembled microlasers could be versatile components for on-chip multiplexing applications.
Related IIT publications
- R. Krahne, M. Zavelani et al., “Amplified Stimulated Emission from Core and Shell Transitions in CdSe/CdS Nanorods fabricated by Seeded Growth”, Appl. Phys. Lett. 98, 063105 (2011).
- M. Zavelani, R. Krahne et al., “Lasing in self assembled microcavities of colloidal core/shell CdSe/CdS quantum rods”, Nanoscale 2, 931 (2010). Cover image.
- M. Zavelani, R. Krahne et al., “Self-assembled CdSe/CdS nanorod micro-lasers fabricated from solution by capillary jet deposition”, submitted (2011).