Optimized Waveguide Geometry for Low Amplified Spontaneous Emission Operation on ITO-Coated Glass

• Published in: IEEE journal of selected topics in quantum electronics 2016-01, Vol.22 (1), p.21-25
• Main Authors: Yi, Jianpeng, Fang, Yueting, Fang, Ting, Chi, Lang, Xia, Ruidong, Wei, Wei, Xia, Bin
• Format: Article
• Language: English
• Subjects: Amplification; amplified spontaneous emission (ASE); cellulose acetate; Gain; Glass; Indium tin oxide; Nanoparticles; Optical films; Optical pumping; Optical waveguides; Organic laser; PFO; Reduction; silver nanoparticles (AgNPs); Spontaneous emission; Thresholds; Waveguides
• ISSN: 1077-260X; 1558-4542
• DOI: 10.1109/JSTQE.2015.2456339

We demonstrated a significant reduction of amplified spontaneous emission (ASE) threshold for an organic optical gain medium operation on an ITO-coated glass by introducing a solution-processed cellulose acetate (CA) thin film as a space layer between the ITO electrode and the optical gain active layer. Using PFO as an optical gain medium, we observed a 4.4-fold threshold reduction from 140 μJ/cm 2 for glass/ITO/PFO device to 32 μJ/cm 2 for glass/ITO/CA/PFO by controlling the thickness of CA film at 38 nm, and 9.9-fold reduction to 15 μJ/cm 2 by further increasing the thickness of CA film to around 152 nm. Furthermore, we investigated symmetrical waveguide of glass/ITO/CA/PFO/CA configuration. It exhibited 3.3-fold lower ASE threshold than that of asymmetrical waveguide of glass/ITO/CA/PFO (6.0 versus 20.0 μJ/cm 2 ), which was even lower than that of quartz/PFO (8.4 μJ/cm 2 ). The CA film was also doped with Ag nanoparticles (AgNPs) in various ratios to improve the conductivity. ASE threshold of glass/ITO/CA(AgNPs)/PFO exhibited no detectable increase with the doping ratio of Ag nanoparticles up to 15 wt%.