In the past decades, third harmonic generation (THG) is realized mainly by bulk optical materials possessing high nonlinear coefficients, however its long interactional length hampers the practical applications. Silicon metasurface provides a new idea to solve this problem, trapping the light in the silicon nanoparticles can substantially enhance the local electric field to improve the conversion efficiency of THG using trapped mode.
Prof. Yi Wang’s team of ANPI, Wuhan National Laboratory for Optoelectronics, has designed a silicon metasurface which is consist of symmetric spindle-shape nanoparticle array，realizing the enhancement of THG successfully. Supported by the high quality factor Fano resonance in silicon metasurface, the conversion efficiency of THG is about 300 times larger than that of bulk silicon slab. The maximum extinction ratio of the intensity of THG reaches about 25 dB by tuning the polarization angle of incident light.
On August 22th, 2016, the investigation result entitled “Enhanced third harmonic generation in a silicon metasurface using trapped mode” was published in “Optics Express” (vol. 24, no. 17, pp. 19661-19670, 2016). Relative work was partially supported by the National Natural Science Foundation of China (NSFC) (No. 60806016, No. 61177049, No. 11304365) and National Basic Research Program of China (No. 2012CB922103, No. 2013CB933303).
Fig. 1.Scheme of three-photon up conversion within silicon metasurface.
Fig. 2. (a) The spectrum of pump beam; (b) Blue-green THG; (c) Enhanced THG spectrum with different polarization angles; (d) The measured normalized THG signals (red rhombus dots) fitted with simulation results (blue dashed line) and theoretical equation (black line).