Several Optical Devices Based On Microfiber

In recent years, the development of micro fibers has attracted the interest of many researchers and microfibers soon become a hot topic. With different structure, size and material system, microfibers can come up with different new effects. We have designed several optical devices based on the unique properties of optical microfibers. These devices include Fabry-Perot interferometer based on microfiber tip, microfiber Bragg gratings, highly birefringent slot-microfiber and D-shaped fiber based on microfiber. We have investigated their properties in the field of sensing and communication. We can greatly reduce their sizes by employing our design.1. We have designed Fabry-Perot interferometers based on microfiber tips and used them for refractive index and temperature sensing application. This structure utilizes the phase change induced by the change of cavity length and that by the phase difference between different modes. This enables these devices to be compact and small in size (-5μm in length), making it the smallest Fabry-Perot interferometer. It shows potential applications in temperature measurement in tiny space and in bio-photonics.2. We have investigated microfiber Bragg gratings and found that they can be used as both refractive index and temperature sensors. The gratings fabricated by focused ion beam method have a large refractive index modulation which could be used to increase reflection by fewer periods, thus reducing the dize. In fact, the microfiber grating fabricated is the smallest one to our knoelwdge. Besides, microfiber Bragg gratings have a large evanescent field, enlarging their application in more areas. Experimentally, we found the refractive index and temperature sensitivity reaches20pm/℃and125nm/RIU, respectively.3. We have proposed a slot-micro fiber and its sensing applications. We found that by introducing the slot structure in microfibers, we obtained a birefringence that is one to two magnitudes higher than that of conventional highly birefringent fibers. We also designed a sensor based on fiber loop mirror. Theoretical results show that the refractive index, temperature and strain sensitivity is one to two magnitudes higher than that of traditional ones. Besides, we extended this method to planar waveguide. The results show that this new design makes the sensors have much higher sensitivity than those without the design.4. Theoretically, we have designed a D-shaped fiber based on optical microfiber and discussed its waveguiding, dispersion and birefringence properties. Experimentally, we have wrapped a microfiber on a rod that was pre-treated with low-index polymer. This compact device has a birefringence higher than10"3over a spectrum of400nm. Moreover, the fabrication of this method is simple but effective. The investigation into this device could improve our understanding of microfibers in future optical fiber communication, sensing and micro-/nano-photonics.In sum, we have carried out a series of meaningful exploration and research in the field of microfibers, such as, to minimize the size of the device and to improve the sensitivity of the sensors. We believe that our investigation into microfiber could offer powerful support for the development of micfiber and its application in our daily life.