Design And Fabrication Of 3D Optical Polymer Waveguides For Optical Interconnect And Optical Sensing Applications

With the rapid development of super computer and data center,there are increasing demands for the process speed and the capacity of interconnects.The traditional electric interconnects technologies have large difficulties in overcoming the bottleneck of bandwidth,interconnect density and the sustainability on the power consumption.On the other hand,optical interconnect technology due to its distinctive advantages in realizing large bandwidth,low latency,low transmission loss,and immune to electromagnetic interferences,are under intensive research and are penetrate to board-level even chip-level interconnect applications.Polymer waveguide is one of the key components for optical interconnects application with advantages such as good compatibility with printed circuit board,high interconnect density,and suitable for mass production.By using the 3D direct inscribing method,3D polymer waveguide with large size and complicated structure with three-dimensional freedom can be realized.In addition,instead of the square core fabricated by the lithography method,circular core waveguide and an adjustable index-profile can be realized which lead to a better compatibility with the mode profile of optical fiber and can effectively reduce the additional loss resulted from the side-wall surface roughness.In this research,we fabricated polymer waveguide for board-level optical interconnects application by using the 3D direct inscribing technique.The waveguide core size is 50?m,the waveguide core pitch is 250?m,and the overall size is 16 cm?20 cm.We have prepared 3 sets of 18 waveguides,each with 6 waveguides,the longest of which is 27 cm.The measured waveguide loss is 0.089 d B/cm,crosstalk is less than 43 d B,and the 3 d B misalignment tolerance in both horizontal and vertical directions is greater than±20?m.We evaluated the transmission performance of the waveguide and tested the eye diagram of the optical waveguide at 25 Gb/s and 32 Gb/s NRZ signal,demonstrating its performance at high rates.At the same time,by comparing the simulation results with the experimental data,the experimental results fit well with the simulation results.We also proposed a novel flexible and wearable optical pressure sensor using 3D polymer directional coupler for the first time to the best of our knowledge.The sensing chip employs a 3D directional coupler structure and is made of polymer material which guarantees the adequate responsibility to pressure and flexibility for wearable applications.When the external pressure is applied to the sensing region,the sensing chip deforms and the spacing between two waveguides becomes smaller which results in a change in the splitting ratio at the output ports and can be converted to pressure changes after a calibration process.In experiment,we achieved a sensitivity of 1.46 MPa^-1 at the range from 0.1 to 0.2 MPa at the wavelength of 1550nm and the experimental results agree well with the simulated ones.