研究目的
To demonstrate the first realization of quasi-phase-matched (QPM) third harmonic generation in isotropic polymer films using spin-coated thin films of ethyl-violet molecules dispersed in a polymer host.
研究成果
The study successfully demonstrated QPM for direct THG with multi-layer polymer films, showing a quadratic increase in THG output with the number of nonlinear layers up to four periods. A record THG conversion efficiency of 0.15% was achieved. Future work includes investigating waveguide structures for QPM with more periods and new materials with smaller optical losses.
研究不足
The optical quality deteriorates with more layers, and the loss increases significantly. The study suggests investigating new materials with smaller optical losses at the harmonic frequency window for QPM with more periods.
1：Experimental Design and Method Selection:
The study used spin-coated thin films of ethyl-violet molecules dispersed in a polymer host (EV) as cubic nonlinear optical media. A passive layer of a UV-curable material (NOA61) was used to compensate the phase shift between the fundamental and third harmonic light waves.
2：Sample Selection and Data Sources:
Samples with 1~4 EV layers (0~3 alternatingly coated passive layers) were fabricated. The thickness of each layer was chosen to be one coherence length for the THG process.
3：List of Experimental Equipment and Materials:
Optical parametric generation-amplification (OPGA) system, β-barium borate crystals, mode-locked Nd:YAG laser, Si-avalanche photodiode, power meter.
4：Experimental Procedures and Operational Workflow:
The idler light was loosely focused on the samples near normal incidence. The 3ω output was spectrally separated from the strong fundamental and measured.
5：Data Analysis Methods:
The THG output power was measured and analyzed for quadratic increase with the number of layers.
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