This paper describes the design, fabrication and testing of tunable Fabry-Perot filters. The goal of this research is to develop novel tunable filter with an area of 5x5 mm<sup>2</sup> that will be used in infrared gas sensors. This exploits the fact that most gases have unique infrared absorption signatures in the 2-14 µm wavelength region. The filter consists of two thin silicon wafers coated with quarter wave dielectric layers to form wavelength dependent high reflection mirrors and separated by air gaps with an average height of 8, 5.1 and 3.5 μm. The mirrors are supported by four elastic polymer posts (springs) each with an area of 100×100 μm<sup>2</sup> made by using photo definable polydimethylsilxane (PDMS). An
electrostatic voltage is used to compress the springs, change the airgap height and hence shift the transmission peaks to a shorter wavelength. A finesse of 12 with full width at half maximum (FWHM) of 70 nm, and a peak transmission of 63% were achieved by applying 100 volts on a device with 8 µm post height and wafer thickness of 125 µm. In addition, the measured tunability before and after hard baking of the device was 210 nm and 130 nm respectively. The tunability
stayed constant after hard baking the devices and did not show any changes with time. The tunability was also measured on a thinner silicon mirror with 3.5 µm post height. In this case, the filter was tuned 180 nm by applying 10 volts. However, the filter finesse was 3, transmission peak was 40% and FWHM over 200 nm. An antireflection coating was deposited on one side of silicon wafers and a Fabry-Perot filter to study transmission enhancement and satisfactory results were achieved.
Today's product design, especially the consuming product design, focuses more and more on individuation, originality, and the time to market. One way to meet these challenges is using the interactive and creationary product design methods and rapid prototyping/rapid tooling. This paper presents a novel Freeform Object Design and Simultaneous Manufacturing (FODSM) method that combines the natural interaction feature in the design phase and simultaneous manufacturing feature in the prototyping phase. The natural interactive three-dimensional design environment is achieved by adopting virtual reality technology. The geometry of the designed object is defined through the process of "virtual sculpting" during which the designer can touch and visualize the designed object and can hear the virtual manufacturing environment noise. During the designing process, the computer records the sculpting trajectories and automatically translates them into NC codes so as to simultaneously machine the designed part. The paper introduced the principle, implementation process, and key techniques of the new method, and compared it with other popular rapid prototyping methods.
Applications of Virtual Reality (VR) technology in many fields have gained great success. In the product development field, VR is a good tool to provide interactive and friendly human-machine interface. Freeform Object Design and Simultaneous Manufacturing (FODSM) uses VR to establish an interactive design environment and enable simultaneous manufacturing. It aims at improving design efficiency, creativity, ease of use, and also aims at integrating design and manufacturing in order to obtain the designed object by the designer independently and simultaneously. For the current stage, key technologies to implement FODSM include the algorithm of swept volume calculation and the following Boolean operation, mechanism to provide natural and intuitive feedback. This paper uses an analytical and experimental method to implement the novel design and manufacturing technology. Key issues are analyzed and tested. Experimental details are demonstrated.