Surface plasmon enhancement of photon extraction efficiency by silver nanoparticles: With applications in laser cooling of semiconductors

Laser cooling of materials has been one of the important topics of photonic research during recent years. This is due to the compactness, lack of vibration, and integratibility of this method. Although laser refrigeration has been achieved in rare earth doped glass, no net cooling of semiconductors has been observed yet. The main challenge in this regard is the photon trapping inside the semiconductors, due to its high refractive index, which prevents the extraction of the energy from the material. Various methods have been proposed to overcome photon trapping but they are either not feasible or introduce surface defects. Surface defects increase the surface recombination which absorbs some portion of the photoluminescence and converts it to heat. We exploit the surface plasmons produced in silver nanoparticles to scatter the PL and make the extraction efficiency significantly higher without increasing the surface recombination. This is also important in the semiconductor lighting industry and also for enhancing the performance of solar cells by coupling the sunlight into the higher index absorbing region. Finite difference time domain simulations were used to find the total power extraction efficiency of the silver nanoparticles. It is also proposed for the first time to use the silver nanoparticles as mask for dry etching. The results for both etched and unetched cases were compared with each other. We also refer to a method of silver nanoparticle fabrication which is easy to apply to all kinds of cooling targets and is relatively cheaper than deposition of complex anti-reflective coatings.