Direct backward third-harmonic generation in nanostructures.
Direct-backward third harmonic generation (DBTHG) has been regarded as negligible or even inexistent due to the large value of wave-vector mismatch. In the past, BTHG signals were often interpreted as back-reflected or back-scattered forward-THG (FTHG). In this paper, we theoretically and experimentally demonstrate that backward third harmonic waves can be directly generated, and that their magnitude can be comparable with FTHG in nanostructures. Experimental data of DBTHG from ZnO thin films, CdSe quantum dots and Fe(3)O(4) nanoparticles agree well with simulation results based on the Green's function. An integral equation was also derived for fast computation of DBTHG in nano films. Our investigation suggests that DBTHG can be a potentially powerful tool in nano-science research, especially when combined with FTHG measurements.
Chang
Chieh-Feng
CF
Department of Electrical Engineering and Graduate Institute of Photonics and Optoelectronics, National Taiwan University, Taipei 10617, Taiwan.
Chen
Hsing-Chao
HC
Chen
Miin-Jang
MJ
Liu
Wei-Rein
WR
Hsieh
Wen-Feng
WF
Hsu
Chia-Hung
CH
Chen
Chao-Yu
CY
Chang
Fu-Hsiung
FH
Yu
Che-Hang
CH
Sun
Chi-Kuang
CK
D000465:Algorithms; D003198:Computer Simulation; D005290:Ferric Compounds / Q000737:chemistry; D007091:Image Processing, Computer-Assisted; D015233:Models, Statistical; D049329:Nanostructures / Q000737:chemistry*; D036103:Nanotechnology / Q000379:methods*; D016011:Normal Distribution; D055095:Optics and Photonics; D045663:Quantum Dots
D005290:Ferric Compounds; C000499:ferric oxide