Research On Polymer Waveguide Power Splitter Based On NaTF₄:Er³⁺,Yb³⁺ Nanocrystals

Optical communication,as a kind of emerging communication technology based on light wave,has received widespread attention in recent years due to its advantages of large transmission capacity,long relay distance,and excellent security performance.It has become an important pillar of the communication industry.In the optical communication network,there exists a large number of planar optoelectronic devices,such as optical switches,multiplexers/demultiplexers,optical modulators,etc.As the foundation of the optical network,they are rapidly developing with the development of optical network.These optoelectronic devices will inevitably cause losses during operation and it will greatly reduce the signal transmission distance and increase the bit error rate without compensation.Optical amplifier is an optical device that can amplify signal light by pump source excitation thus realizing the compensation function.Erbium-doped optical waveguide amplifier,a typical kind of optical amplifier with characteristics of small product and high gain,has been widely used in integrated optics.Although easy integration is its advantage,when an independent optical amplification unite is inserted,the integration degree of the device will be inevitably decreased.Therefore,a device that can provide compensation for its own insertion loss while achieving the basic function of the optical element has become the best solution to the problem of on-chip integration loss.In this paper,an integrated Y-branch waveguide power splitter with loss compensation using a doped polymer as the core material was proposed.It is an effective way to fix the contradiction between integration and insertion loss.By this method,the loss will be compensated under the excitation of pump power and the integration of device will not be reduced.A polymer waveguide amplifier in a structure of embedded waveguide based on NaYF₄:Er³⁺,Yb³⁺nanocrystals was designed and fabricated.The rare earth ion-doped NaYF₄ nanocrystals were prepared by high-temperature pyrolysis method.The absorption spectrum,emission spectrum and particle morphology of NaYF₄:Er³⁺,Yb³⁺nanocrystals were characterized.With these parameters,the gain and power distribution of the device was simulated by Matlab,COMSOL.The nanocrystals were dispersed in SU-8 photoresist as the core material of the waveguide,PMMA and SiO₂were used as the upper cladding and lower cladding,respectively.PMMA/SiO2 were used as the upper/lower cladding layers of the device.Using the method of typical semiconductor technology.When the input optical signal power was 0.1 mW and the pump power was 267.7 mW,a relative gain of 3.5 dB at 1530 nm was achieved.A Y-branch polymer waveguide power splitter with loss compensation based on NaYF₄:Er³⁺,Yb³⁺nanocrystals was designed and fabricated based on the research of waveguide amplifier.The structure of the device was optimized by software such as Rsoft and COMSOL and the power distribution was simulated.The polymer Y-branch with a structure of embedded waveguide was obtained by etching SiO₂.Nanocrystals were dispersed in the SU-8 as the core material of the waveguide,the PMMA and SiO₂ were used as the upper cladding and lower cladding,respectively.The insertion loss of each branch of the device is about 15 dB.The relative gains of two branches were 5.81 dB and 5.41 dB at 1530 nm under the pump power of 267.7 mW.An integrated pump/signal multiplexer with waveguide amplifier on chip was designed and simulated.According to the directional coupling theory of the waveguide and optical waveguide design theory,the parameters were calculated.According to the simulation result,the pump power is well demultiplexed by the device both in 1550 nm and 540 nm amplification system.By integrating the multiplexer at the output side of the waveguide amplifiers,the residual pump power after amplification will be demultiplexed from the output light.The residual pump light will not influence the signal light by this structure.