Study On High-Speed Organic Polymer Waveguide Thermo-Optical Switches

In the all-optical network, there are many optical switching technologies, including two-dimensional or three-dimensional micro-electro-mechanical systems (MOEMS), waveguide structure, liquid crystal, acousto-optical switches. Among them, the waveguide switches based on changing absorbance or refractive index to affect the transmission of light, can be easily prepared. If multiple optical switch devices are integrated on a substrate, it can reduce the cost of a single function, and improve the stability. The waveguide thermo-optic switch is a device of refraction index modulation using thermo-optical effect, with its small size and large scalability. Its low crosstalk and insertion loss are suitable for most applications. Due to organic polymer materials’ large thermo-optical coefficient, phase modulation can be achieved with little temperature change. With small transmission loss, simple preparation process, low cost, a more promising market, they become a kind of attractive materials for waveguide.Firstly, the principle of thermo-optical switch has been demonstrated. Then based on ChemOptics ZPU series of fluorinated acrylate material, using effective index and beam propagation method, polymer thermo-optical switch has been designed and optimized. There are two types of MMI switches based on silica or polymer as the lower cladding. The size of the structure and theoretically derived switching time are simulated. By spin coating, lithography, etching and other processes, polymer thermo-optical switches have been prepared. The idea is demonstrated that pre-spin coat upper cladding, so that the absorbtion loss caused by Al embedded polymer in etching process can be reduced. Experimental results confirm its feasibility. Static and dynamic properties of waveguide devices have been tested. Results of 1 ×2 Switches with polymer lower cladding have been demonstrated that insertion loss is less than 9.4dB, crosstalk is greater than 19.3dB, the switching time of less than 1.15ms. Results of 1×2 Switches with silica lower cladding have been demonstrated that the insertion loss is less than 9.9dB, crosstalk is greater than 16.5dB, the switching time of less than 0.65ms. Experimental results show that silica material as the lower cladding layer can greatly improve the speed of the switch, but the characteristic of loss is not ideal. Finally, optical switching unit is cascaded to achieve the design and preparation of silica lower cladding 1×4 optical switch array. Results have been demonstrated that insertion loss is less than 12.9dB, crosstalk is greater than 18dB. Test results validate the design ideas.