Study On Thermo-Optic Tunable Filter And Its Key Technology

Thermo-optic tunable filter is a new kind of optical device,it has a wide range of applications in lots of fields such as optical fiber communication,tunable laser output,spectrum analysis and infrared detection.The device based on thermo-optic effect could achieve tunable filtering by the shift of central wavelength,and has the merits of wide tuning range,easy to manufacture and simple structure.Aiming filter performance to design structure,determining the process plan of the filter based on experiment condition,and variation of each film layer in filter structure are all key points to influence the device performance,therefore,in this paper the structure characteristic is analyzed through theory,then on this basis to optimize and select the device structure,and from the perspective of process to consider and eliminate the problem which exist in multilayer films.The filter is fabricated and tested,and its application is explored initially.At first,the suitable filter materials are determined by analyzing the character demanding of device,and the filter structure is analyzed through theory according to the selected material,from the analysis the filter structure is determined,its basic structure has the cavity thickness of half wavelength and single cavity,the thermal tuning performance is also simulated,and the filter achieves the tuning sensitivity of 0.1nm/?.Secondly,by analyzing the requirements of the device to the film and the difficulties of process realization,the problems in deposition process such as stress,uniformity,layer contact and roughness are solved,and the process parameters of each layer are also selected,besides,the possible error in fabrication is analyzed,on this basis the process of unit filter is completed.The filter sample achieve 72% transmittance at the position of 1554 nm,the film layer of the device is uniform,continuous and compact,there is no obvious defect according to the SEM image.The thermo-optic device test platform is built to test the thermal tuning performance of the filter,the center wavelength emerges obvious shift and achieve tuning sensitivity of 0.072 nm/?,and the variation of thermal response is tiny at different position,exhibiting favorable thermal response uniformity.Finally,the arrayed device is achieved using lithography technology to explore the application technique,the device is characterized,the distribution of filter array is uniform,and the size of the pattern almost keeps the same.The filter realizes the control of light intensity by the changes of temperature,exhibiting desirable application prospect in the fields of optical switch and detection,and it laid the foundation of further research.