title: Direct backward third-harmonic generation in nanostructures.
abstract: 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.
authors.affiliation: Department of Electrical Engineering and Graduate Institute of Photonics and Optoelectronics, National Taiwan University, Taipei 10617, Taiwan.
authors.forename: Chieh-Feng
authors.initials: CF
authors.lastname: Chang
authors.forename: Hsing-Chao
authors.initials: HC
authors.lastname: Chen
authors.forename: Miin-Jang
authors.initials: MJ
authors.lastname: Chen
authors.forename: Wei-Rein
authors.initials: WR
authors.lastname: Liu
authors.forename: Wen-Feng
authors.initials: WF
authors.lastname: Hsieh
authors.forename: Chia-Hung
authors.initials: CH
authors.lastname: Hsu
authors.forename: Chao-Yu
authors.initials: CY
authors.lastname: Chen
authors.forename: Fu-Hsiung
authors.initials: FH
authors.lastname: Chang
authors.forename: Che-Hang
authors.initials: CH
authors.lastname: Yu
authors.forename: Chi-Kuang
authors.initials: CK
authors.lastname: Sun
mesh_terms: 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
chemical_list: D005290:Ferric Compounds; C000499:ferric oxide