Study On Direct Writing Of Polymer Strip Optical Waveguides By Micropen

Although the traditional methods of fabricating polymer strip optical waveguides are already applied widely, the shortcomings of the complex manufacturing process, time-consuming and low efficiency are still difficult to overcome. In compare, direct writing technology has attracted great attention for the virtues of maskless, high-flexibility, high-precision, fast-fabrication, high-reliability, low-cost and wide-adaptability to materials. Therefore, the technology of direct writing is very suitable for the period of experimental research and small-scale product development.In this paper, the idea of fabricating the core layer of polymer strip optical waveguides was given based on the characteristics of polyimide(PI) and the direct writing of micropen. PI strip optical waveguides with good formation were fabricated successfully and the writing parameters, dimension control and light propagation of waveguides were investigated systematically.In experiments, the effects of writing velocity (V), gas pressure (P) and the height (H) between the micropen point to the substrate on the width of the polymer strip waveguides were studied. The width of the waveguides increases with the gas pressure but decreases with the writing velocity when other parameters are fixed. Besides, there is a critical distance between the micropen point to the substrate. The width of the waveguide changes little when the height (H) between the micropen point to the substrate is lower than the critical distance. But the formation quality of the strip waveguide becomes worse when the height (H) between the micropen point to the substrate is higher than the critical distance. In our work, basing on dimension and appearance of the strip optical waveguides, we can get the following optimized writing parameters: writing velocity (V) is 2mm/s, gas pressure (P) 8kPa, the height (H) between the micropen point to the substrate is 5μm.Heat treatment process tremendous influences the propagation loss of waveguides. The experimental result indicates that propagation loss of the PI material increases with the temperature in the range of 50 to 300℃. And the minimum propagation loss of the PI materials was gotten after the heat treatment at 300℃. Moreover, the reason of producing particles, pores, cracks and irregular shape in the procedure of writing waveguides were discussed and corresponding solutions were given. The propagation losses of the PI strip optical waveguides were measured by the use of cut-back method at the wavelength of 1550nm. And the minimum propagation of the strip optical waveguides is 0.27 dB/cm, which can meet the application need of the optical integrate device in the communication wave band.