Partially liquid-filled hollow-core photonic crystal fiber polarizer

Abstract

A compact fiber polarizer is demonstrated by the filling of selected air holes of a hollow-core photonic crystal fiber (PCF) with a liquid. The liquid-filling results in an asymmetric waveguide structure, leading to a large polarization dependent loss. A 6 mm long ethanol-filled PCF exhibits a polarization extinction ratio of ∼18 dB over a wavelength range from 1480 nm to 1600 nm. In-line fiber polarizers with low-insertion loss, highpolarization extinction ratio and wide operational wavelength range are often needed in optical fiber sensors and communication systems. Fiber optic polarizers have been made by coating the flat side of a side-polished conventional single-mode fiber (SMF) or a D-shaped optical fiber with a thin metal layer [11,12]. However, the complex manufacturing process means higher component cost. Combined with the PCFs, a novel polarizer based on a long period grating written on a solid-core PCF is realized [7]. However, the device suffers from a narrow operational wavelength range (∼10 nm). A fiber polarizer was made by using a pulsed CO 2 laser to deform the air holes of a hollow-core PCF [8]. The polarizer exhibits a polarization extinction ratio of more than 20 dB over an operational wavelength range of wider than 100 nm. However, the CO 2 laser irradiated region is fragile, which may be disadvantageous for practical applications. Recently, we proposed a polarizer configuration based on a partially liquid-filled hollow-core PCF [13]. The polarizer is compact and robust.In this Letter, we report the experimental demonstration of a compact polarizer based on a partially ethanolfilled hollow-core PCF. The partial filling of air holes by a liquid is realized by a simple and practical technique.To the best of our knowledge, it is the first time that this technique is used to fill liquid into selected air holes so that an asymmetric waveguide structure is formed. The partial filling of liquid results in leaking out of one polarization eigen-mode, while keeping the orthogonal polarization-mode propagating along the fiber with relatively low loss. The details about the selective filling technique, the fabrication, and characterization of the polarizer are reported in following sections. Figure 1 illustrates the proposed partial liquid-filling technique. In this illustration, a solid-core PCF is shown, but the technique can be used for both solid-core and hollow-core PCFs. The PCF is firstly spliced to a SMF with a lateral offset. Most of the cladding air holes are sealed by the spliced joint while some of the air holes are left open and used for subsequent liquid-filling. The size of the unsealed region [indicated as S in Fig. 1(b)] is controlled by the lateral offset at the spliced joint. The spliced joint is

Ultra-high tunable liquid crystal-plasmonic photonic crystal fiber polarization filter

“…The fiber-grating-based polarizing devices have many advantages including compact structure, narrowband spectrum and low insertion loss. However, the other approach for realizing polarization-dependent devices is filling liquids [7,8] or LCs into PCFs [1,2]. This technique helps to construct devices, which are more easily tunable, controllable and can be flexibly designed than the other devices based on fiber gratings.…”

“…At 2011, Zheng et al proposed an adaptable single polarization single mode high birefringence PCF based on selectively filling cladding-air holes with liquid material [7].This structure achieved an adjustable sensitivity of 1.975 nm/ºC about three orders of magnitude higher than the polarizer based on long-period fiber grating [4]. In the same year, a fiber polarizer was constructed by filling some air holes of a hollow-core PCF partially with weak temperature dependent liquid [8]. In addition, some anisotropic liquids [9,10] are used to design fiberpolarizing devices.…”

Compact and Ultrasensitive Temperature Sensor With a Fully Liquid-Filled Photonic Crystal Fiber Mach–Zehnder Interferometer

“…Based on post-processing techniques, the micro air holes can also be filled with liquid, gas or even solid materials, which can greatly change the PCF guiding characteristics, and a variety of functional fiber devices could be fabricated such as electrically controlled optical switches [1]- [3], all-optical modulator [4], temperature-controlled tunable optical filters [5], photonic bandgap fiber polarimeters [6], [7] and optical fiber sensors [8].…”

All-Fiber Optofluidic Component to Combine Light and Fluid

“…Several techniques have been reported for filling fluid into the holes of microstructured fibers. For instance, blocking cladding holes with a cured polymer [12], focused ion beam-milled microchannels on the side of the fiber [13], splicing with a lateral offset [14], using a micropipette [15] and C-shaped fiber for liquid delivery [16] are techniques that allowed for the interaction of a liquidfilled hollow core and light. However, the problem remains of how to collect or administer fluid in a controlled way without disturbing the optical path, providing a hermetic arrangement that prevents harmful fumes and contamination while avoiding the use of bulky components with large dead-volume.…”