Enhanced photoluminescence extraction efficiency from a diamond photonic crystal via leaky modes

Two-dimensional photonic crystal can be exploited as the top part of a light source in order to increase its extraction efficiency. Here, we report on the room-temperature intrinsic photoluminescence (PL) behavior of a nanocrystalline diamond (NCD) layer with diamond columns prepared on the top and periodically ordered into the lattice with square symmetry. Angle-resolved far-field measurements in the Gamma-X crystal direction of broadband visible PL revealed up to six-fold enhancement of extraction efficiency as compared to a smooth NCD layer. A photonic band diagram above the lightcone derived from these measurements is in agreement with the diagram obtained from transmission measurements and simulation, suggesting that the enhancement is primarily due to light's coupling to leaky modes

Time-resolved measurements of optical gain and photoluminescence in silicon nanocrystals

In this paper, we present time-resolved optical gain spectroscopy using a combination of the variable stripe length and the shifting excitation spot techniques under pulsed nanosecond excitation at 355 nm. Optical gain measurements in the temporal detection window of 10 ns width, coincident with the excitation pulse, revealed induced absorption losses, whereas measurements with a different detection gate width and delay in two main photoluminescence components (a fast band at ~430 nm decaying in nanoseconds and a slow band at ~620 nm decaying in microseconds) show a positive optical gain of the order of tens of cm-1