Research of a single-polarization suspended-core micro-structured fiber

Single-polarization single-mode (SPSM) fibers, supporting only one polarization state within some particular wavelength ranges, can suppress both polarization mode couplings and polarization mode dispersions, which have extensive applications in various techniques such as fiber optic gyroscopes, high power fiber lasers, current sensors, and other polarization-sensitive components. The suspended-core PCF, based on index-guiding mechanism, is one promising kind of fiber which can easily realize single-mode operation and meanwhile keep a relatively larger fraction of the guided mode power distributing in the air. This type of fiber, due to the property of the high overlap factor of the evanescence field, has attractive applications in chemical or biological sensing and gas sensing areas. In this paper we present the design and investigation of a single-polarization suspended-core fiber with an elliptical core consisting of crossed rectangular shaped dielectric strips. A rectangular shaped dielectric strip distributes in an orientation which has an angle θ with the x-axis, and the other strip distributes in the direction which has an angle π-θ with the x-axis. The two strips have the same thickness and width with each other. The intersection part of the two strips acts as the fiber core. The rest of these rectangular shaped strips and four big air holes constitute the cladding of the fiber. The guiding mechanism of the proposed fiber is the total internal reflection. By adjusting the fiber structure parameters, one polarized mode can be effectively eliminated through certain transmission distance and the single-polarization operating can be realized. For some cases with optimized fiber configuration parameters, single-polarization single-mode transmission with broad bandwidth can also be obtained. Meanwhile, the power fraction within air of the x-polarization mode for this fiber is relatively high which facilitates its applications in high precision sensors.