Effect Of Bonding Ratio Of Erbium-Doped Nanocrystals To Polymers On The Gain In Optical Waveguide Amplifier

In the information age,there has been an explosive growth of the demand for data transmission.Integrated photonic chip has become a significant pillar of the communication network due to its advantages of large transmission capacity,low transmission loss and strong anti-interference ability.A large number of planar optoelectronic devices will inevitably cause optical loss in the large-scale integration,affecting the quality of communication directly.The optical waveguide amplifier,which is mainly used to process and amplify the optical signal in the integrated circuit,can realize the compensation function for the optical signal loss in the integrated device.Rare earth nanocrystals have high luminescence intensity and quantum efficiency in the near-infrared band.Organic polymers have convenient processing technology,low price and compatibility with silicon matrix.Therefore,the development of rare earth nanocrystals doped polymer optical waveguide amplifier can advance the development of the integrated photonic chip.The copolymerization of erbium-doped nanocrystals with monomer can obtain high-quality organic-inorganic nanocomposite gain medium,and then fabricate the excellent performance optical waveguide amplifier.The gain performance of the device is closely related to the sizes and bonding concentrations of nanoparticles in the composite polymers.Increasing both the sizes and concentrations of nanoparticles can enhance the luminescence intensity of the gain medium in the C-band,but also increases the scattering loss.To address the question of how the bonding ratio of erbium-doped nanocrystals to polymers affects the gain of optical waveguide amplifier,this thesis focused on the light scattering calculation of nanoparticles,the synthesis of materials and the preparation of devices and achieved the following innovative results.1.The Rayleigh ratios of nanoparticles were calculated based on Rayleigh scattering theory.The scattering cross sections of the nanoparticles in the polymers were calculated using FDTD Solutions.The scattering cross section decreased with the increasing wavelength and increased with the increasing concentrations of nanoparticles.At 1530 nm,the scattering cross section increased by a factor of 96.5 and67.5 for the two spherical particles at 16 nm and 30 nm,respectively,when the concentrations were increased tenfold from 0.05 mmol to 0.5 mmol.This indicated that for the same change in molar concentrations,the variation of scattering cross section was relatively smaller with large sizes nanoparticles doped.2.Theβ-Na Lu_0.5Y_0.3F₄:Yb³⁺,Er³⁺nanoparticles with sizes around 16 nm were synthesized,modified with unsaturated functional groups as carbon-carbon double bonds.Four groups of organic-inorganic composite polymers with different bonding ratios were successfully synthesized by copolymerizing 10 g of MMA monomer with0.05 mmol,0.10 mmol,0.15 mmol and 0.25 mmol of nanoparticles,respectively.With the increasing concentrations of bonded nanoparticles,the luminescence intensity of the composite polymers increased gradually,but the transmittance decreased slightly to around 80%in the C-band.Four groups of embedded optical waveguide amplifiers with the length of 1.3 cm were fabricated by spin coating process.The relative gains of the devices were 1.0 d B,3.0 d B,3.5 d B and 5.6 d B at 1550 nm when the pump optical power was 300 m W and the signal optical power was 1 m W,corresponding to the nanoparticles concentrations of 0.05 mmol,0.10 mmol,0.15 mmol and 0.25 mmol,respectively.3.Theβ-Na Lu_0.1Y_0.7F₄:Yb³⁺,Er³⁺@NaLuF₄ nanoparticles with sizes around 18 nm were synthesized.Surface defects can be passivated by coating an inert layer in order to improve the intensity of downconversion luminescence.Five groups of organic-inorganic composite polymers with different bonding ratios were successfully synthesized by copolymerizing 10 g of MMA monomer with 0.1 mmol,0.2 mmol,0.3mmol,0.4 mmol and 0.5 mmol of nanoparticles,respectively.With the increasing concentrations of bonded nanoparticles,the luminescence intensity of the composite polymers increased gradually,but the transmittance decreased significantly to around50%in the C-band.Finally,five groups of optical waveguide amplifiers with the length of 0.5 cm were fabricated.The relative gains of the devices were 6.0 d B,8.5 d B,11.1d B,12.8 d B and 13.6 d B at 1530 nm when the pump optical power was 250 m W and the signal optical power was 0.03 m W,corresponding to the nanoparticles concentrations of 0.1 mmol,0.2 mmol,0.3 mmol,0.4 mmol and 0.5 mmol,respectively.Above all,theoretical and experimental studies showed that increasing the concentration of nanocrystals resulted in an advantage of the gain improvement over the increase in scattering loss.