Observation of waveguide Fabry-Perot lasing in highly efficient Si nanocrystals

A luminescent Si nanocrystal (SiNC) thin film with photoluminescence quantum yield (PLQY) > 70% was made by using hydrogen silsesquioxane (HSQ), followed by long-time high-pressure hydrogenation. A net optical gain of 524 ± 21 cm⁻¹ was obtained by means of variable stripe length-shifting excitation spot (VSL-SES). A rectangularly shaped SiO₂ Fabry-Perot (F-P) cavity with size of 1.5 μm (width) × 0.7 μm (height) × 2000 μm (length) was made on top of the SiNC thin film. The waveguide F-P device was pumped with a 400 nm femtosecond pulsed laser. A threshold behavior of the light emission intensity as a function of the pumping power was observed. Other lasing characteristics including spectral narrowing, polarization of the emission, and small emission angle were also observed beyond the threshold pumping power.