Study On Polymer Integrated Photonic Devices Based On Femtosecond Laser Direct Writing

Thanks to the development of semiconductor micro-nano processing technology,the size of electronic computers has been reduced by about 20 orders of magnitude.However,with the advent of the 21 st century,quantum tunneling and thermal noise problems can not be effectively solved,integrated circuits also deviate from Moore’s law planning,resulting in the development of integrated circuits into a bottleneck.The emergence and development of integrated optics provide a good way to solve these problems.Integrated optics is a new cross-information discipline,which is carried by photons with faster propagation rate,stronger stability,higher coding dimension and lower energy consumption,and is represented by optical path systems similar to integrated circuits.Fabrication of photonic devices is the experimental basis and important branch of integrated optics.Photonic devices for functional applications are becoming more and more complex in structure and material composition,so the traditional micro-nano processing technology is facing new challenges.Femtosecond laser direct writing technology has the advantages of high precision,high design degree,wide material selectivity,true three-dimensional,etc,which can largely solve the problems existing in the preparation of micro-nano structures in photolithography.In this paper,femtosecond laser two-photon polymerization direct writing technology is proposed to fabricate micro-nano integrated photonic devices based on polymer system.Waveguide,microcavity laser and microcavity filter,as basic integrated photonic devices,play important roles in signal conduction,signal source and signal processing.A three-dimensional SU-8 photoresist waveguide was prepared by femtosecond laser shell scanning assisted by UV exposure,and the adiabatic conversion between the circular cross section waveguide and the linear polarization state was realized.The fabrication of true 3d mode selective deformation microcavity laser achieves good single-longitudinal mode maser and directional output.A humidity responsive PEG-DA hydrogel microcavity coupled filter was prepared and the humidity adjustable filter was realized.The main contents are:1.UV-NIR femtosecond laser scanning shell SU-8 photoresist waveguide device: using femtosecond laser direct writing preparation of arbitrary cross section shape and high precision shell waveguides,with the help of UV exposure efficiency(improving efficiency to 1500%)curing inside the shell material,design and preparation of arbitrary cross section polarization controlled device,twisted type polarization adiabatic conversion waveguide.The polarization independent waveguide with nearly circular cross-section is fabricated,and the birefringence is as low as1.7e-6.The adiabatic conversion of linear polarization state in any polarization direction is realized.The conversion efficiency of polarization state in visible band and communication band is higher than 80%,and it shows excellent reversibility through light.2.True 3D Mode Selective Deformed Microcavity Laser: For the multimode problem of spatial symmetric microcavity,a three-dimensional deformed polymer microcavity laser doped with dye was designed and fabricated by using the true 3D high precision property of femtosecond laser direct writing.Specifically,three microdisk cavities superimposed coupled lasers,three microring cavities tangentially coupled lasers and grating/microdisk coupled microcavity lasers are fabricated.Three kinds of microcavity lasers are pumped by 532 nm picosecond laser,and good single longitudinal mode excitation is achieved.By adjusting the grating period,the directional maser with wavelength from 636.1 nm to 647.2 nm is realized.3.Humidity response PEG-DA hydrogel microcavity coupling filter: based on the regulation of micro-nano devices demand,PEG-DA hydrogel with humidity response was proposed to replace SU-8 photoresist as the basic material for laser processing,using two-photon polymerization technology,preparation of doped laser dye rhodamine B(as gain medium and light initiator)microcavity group.The filtering effect is realized by adjusting the space of microcavity based on the different response results of hydrogel under external humidity stimulation.The mode reduction and spectral redshift of the microcavity group are achieved under the relative humidity of60%,showing good tunable filtering characteristics.In this paper,by means of femtosecond laser direct writing,the shell scanning ultraviolet exposure and efficient processing solution is put forward,the preparation of the arbitrary cross-section polarization controlled device,polarization adiabatic conversion waveguide,deformation pattern choice microcavity laser and humidity response PEG-DA hydrogel microcavity coupling complex three-dimensional integrated photonic devices have been realized.It provides an effective solution for the three-dimensional spatial distribution of photonic chips and the multidimensional and multifunctional control of photons,and accumulates the technology for the practical application of integrated photonic devices.