Optical gain in different silicon nanocrystal systems

An extensive experimental study of optical gain in silicon nanocrystals is under way. Different types of samples have been tested (e.g., nanocrystalline silicon superlattices prepared in Rochester, ion implanted silicon dioxide prepared in Canberra) using different measurement techniques (e.g., variable stripe length method in Trento and in Rochester, prism coupling in Canberra) and different pump laser sources (from femtosecond to cw). All the results presented here have been reproduced in at least two different laboratories, making it unlikely that experimental artifacts play a role. So far, we have observed nsec-duration gain in the visible/near infrared range in nanocrystalline silicon superlattices under high photoinjection conditions with short laser pulses. For other conditions (e.g., lower photoinjection, ion implanted samples with a lower concentration of quantum dots), we have not observed gain.