Hollow-core photonic bandgap fiber polarizer

Broadband, compact in-fiber polarizers were fabricated using a pulsed CO(2) laser to modify the air holes along one side of the hollow-core photonic bandgap fibers. The polarizers have lengths from 3 to 6 mm and exhibit a polarization extinction ratio of better than 20 dB over a wavelength range larger than 100 nm at approximately 1,550 nm.     

Low-loss all-solid photonic bandgap fiber

We report the fabrication and characterization of a new type all-solid photonic bandgap fiber. By introducing an index depressed layer around the high-index rod in the unit cell of photonic crystal cladding, transmission loss as low as 2 dB/km within the first bandgap is realized for the all-solid photonic bandgap fiber with a bandwidth of over 700 nm. The bend loss experiment shows that the photonic bandgap fiber is much less bend sensitive than single-mode fiber.     

Mode-locked all-solid photonic bandgap fiber laser

We report on a mode-locked all-normal dispersion fiber laser featuring a large-mode-area all-solid photonic bandgap fiber. The self-starting chirped-pulse laser delivers 660 mW of average power at a repetition rate of 30 MHz, leading to 22?nJ energy. The output pulses are dechirped outside the cavity to nearly transform-limited duration of 50?fs. Numerical simulations are in good agreement with experiments and highlight the key role of passive spectral filtering on pulse shaping.     

Three-level neodymium fiber laser incorporating photonic bandgap fiber

We report a neodymium fiber laser incorporating an all-solid photonic bandgap fiber to suppress the four-level laser transition 4F(3/2)-4I(11/2). We demonstrate lasing at 907 nm on the three-level transition 4F(3/2)-4I(9/2) when pumping at 808 nm. The maximum slope efficiency obtained was 32% with a threshold pump power of 70 mW.     

A hollow-core photonic bandgap fiber polarization controller

A polarization controller was built by pressurizing laterally three segments of a commercial hollow-core photonic bandgap fiber. By varying the magnitudes of the applied pressures, the output state of polarization showed a good coverage of all the possible polarization states on the surface of the Poincaré sphere.     

Design of air-guiding honeycomb photonic bandgap fiber

We introduce a design procedure for hollow-core photonic bandgap (PBG) fiber with a cladding made of air-silica honeycomb photonic crystal (PC). It is found that air-guiding can be realized in both fundamental and secondary PBG regions of the cladding PC. Dispersion and radiation loss of the fundamental mode for two types of fiber structure are theoretically calculated. The fibers show promising waveguiding ability.     

Fabrication of all-solid photonic bandgap fiber coupler

We report the fabrication of a tunable all-solid photonic bandgap fiber coupler based on the side-polishing technique. This device is believed to be the first demonstration of a photonic bandgap fiber coupler to eliminate the contamination of the open air holes. By adjusting the length of the interaction section, the tunable coupling ratio as much as 92.5% at 1550 nm is achieved. The investigation of the spectrum properties shows that the coupler has excellent tunability properties, for which the coupling ratio can be smoothly and continuously controlled.     

Highly dispersive large mode area photonic bandgap fiber

An all-silica photonic bandgap fiber composed of a low-index core surrounded by alternating high- and low-index rings allows us to achieve a large mode area (500 microm(2)) and large chromatic dispersion. Sharp resonances from the even Bragg mode to odd ring modes theoretically lead to 20,000 ps/(nm km) chromatic dispersion when large bends are applied. By nature, sharp resonances are sensitive to inhomogeneities along the fiber length. Under experimental conditions, the resonances are broadened and the dispersion coefficient is decreased to 1000 ps/(nm km). However, to the best of our knowledge, this is the largest dispersion coefficient reported using a large mode area fiber.     

All-solid silica-based photonic crystal fibers

An index-guiding all-solid photonic crystal fiber (PCF) composed entirely of silica material is proposed in this paper. The core of this optical fiber is composed of pure silica, and the cladding consists of doped silica rod in the background of pure silica. The dependence of confinement loss on the diameter of the doped rods, the number of doped-rod rings, and the doping level is investigated numerically. In addition, the proposed fiber possesses a shorter cutoff wavelength as compared with the air/silica PCF, which is directly confirmed by the V parameter, and explained based on a scalar approximation method. Furthermore, the bending loss for the fiber is predicted. A low-loss single-mode all-solid silica-based PCF with a large-mode-area is possible by the appropriate selection of configuration parameters.     

Electrically controlled broadband liquid crystal photonic bandgap fiber polarimeter

We demonstrate a liquid crystal photonic bandgap fiber based polarizer integrated in a double silicon v-groove assembly. The polarizer axis can be electrically controlled as well as switched on and off.     

Similariton fiber laser with a hollow-core photonic bandgap fiber for dispersion control

We report on an ytterbium-doped similariton fiber ring laser with a hollow-core photonic bandgap fiber for intracavity dispersion control. The oscillator is hybrid mode locked with a saturable Bragg reflector and by nonlinear polarization evolution. This scheme allows for an exact adjustment of the transmission characteristic to avoid the formation of bunched noiselike pulses while the self-starting characteristic is preserved. The oscillator generates highly stretched similaritons at 1025 nm with a pulse energy above 1n J at a repetition rate of 21.9 MHz.     

低损宽频高双折射太赫兹光子带隙光纤

设计了一种低损耗、宽频段、高双折射太赫兹光子带隙光纤,呈三角晶格排列的亚波长空气孔包层实现了带隙的局域作用.利用全矢量有限元法对光纤的双折射及损耗特性进行了理论分析.结果表明,在大约0.3 THz的宽频范围内,类矩形纤芯太赫兹光子带隙光纤的损耗小于0.009 cm^-1,相双折射在10^-3数量级,群双折射可达10^-2数量级. 关键词： 太赫兹 太赫兹波导 光子晶体光纤 双折射     

谐振式光子带隙光纤陀螺一体化方案

实现了使用光子带隙光纤的一体化谐振式光纤陀螺方案,设计并制作了谐振腔中基于微光学结构的耦合器。实验测得制作的谐振腔清晰度为3.7。搭建了基于该谐振腔的陀螺系统,并对其主、次偏振态的谐振曲线进行了实际测量。实验结果测得该系统60 s零漂为2.45 ()/s,及1 h长期稳定性为7.11 ()/s。同时,实现了对应陀螺输出50 ()/s（积分时间10 s）及100 ()/s（积分时间10 s）的模拟转速实验,验证了该陀螺系统的Sagnac效应。分析得到耦合损耗是影响该陀螺系统性能的主要因素。验证了该谐振腔结构具有应用于陀螺系统的可行性,为谐振式光纤陀螺性能进一步提高提供了参考。     

谐振式光子带隙光纤陀螺一体化方案

实现了使用光子带隙光纤的一体化谐振式光纤陀螺方案,设计并制作了谐振腔中基于微光学结构的耦合器。实验测得制作的谐振腔清晰度为3.7。搭建了基于该谐振腔的陀螺系统,并对其主、次偏振态的谐振曲线进行了实际测量。实验结果测得该系统60 s零漂为2.45 ()/s,及1 h长期稳定性为7.11 ()/s。同时,实现了对应陀螺输出50 ()/s（积分时间10 s）及100 ()/s（积分时间10 s）的模拟转速实验,验证了该陀螺系统的Sagnac效应。分析得到耦合损耗是影响该陀螺系统性能的主要因素。验证了该谐振腔结构具有应用于陀螺系统的可行性,为谐振式光纤陀螺性能进一步提高提供了参考。     

High-efficiency single-mode Raman generation in a liquid-filled photonic bandgap fiber

Single-spatial-mode Raman generation in an ethanol-filled photonic bandgap fiber is demonstrated. Due to the limited bandwidth of the fiber, the generation is limited to the first Stokes order only, allowing high generated power without any visible decrease of the conversion efficiency. The realization of these two key properties opens the way to the realization of optimized compact nonlinear wavelength converters that will accommodate a large variety of usable liquids.     

Optimization of photonic bandgap fiber long period grating refractive-index sensors

Long period gratings in low-index contrast solid-core photonic bandgap fibers are a promising platform for fiber-based fluid refractive index sensing with very low detection limits. We provide a comprehensive investigation of the possibilities for refractive index sensing using that principle in a commercial photonic crystal fiber filled with a fluid: using an acoustic grating, we map out the cladding bands, and use this data to optimize a long period grating’s sensitivity. We then implement the optimized long period grating, again using an acoustic grating, and directly measure its sensitivity to refractive index. We demonstrate a sensitivity of 17,900 nm/RIU (6.94 nm/°C) which corresponds to a smallest detectable index change of the fluid of 8.4 × 10⁻⁶.     

Silica-air photonic crystal fiber design that permits waveguiding by a true photonic bandgap effect

A theoretical investigation of a novel type of optical fiber is presented. The operation of the fiber relies entirely on wave guidance through the photonic bandgap effect and not on total internal reflection, thereby distinguishing that fiber from all other known fibers, including recently studied photonic crystal fibers. The novel fiber has a central low-index core region and a cladding consisting of a silica background material with air holes situated within a honeycomb lattice structure. We show the existence of photonic bandgaps for the silica-air cladding structure and demonstrate how light can be guided at the central low-index core region for a well-defined frequency that falls inside the photonic bandgap region of the cladding structure.     

Parabolic pulse generation in a dispersion-decreasing solid-core photonic bandgap Bragg fiber

We analyze the interplay of nonlinearity and dispersion in a dispersion-decreasing photonic bandgap Bragg fiber as a new platform for generating parabolic pulses. A suitably designed linearly tapered, low-index-contrast, solid-core Bragg fiber - amenable to fabrication by conventional modified chemical vapor deposition technology - is shown to yield stable parabolic pulses. The fiber design was optimized through a simple and accurate transfer-matrix formalism and pulse evolution was studied by the well-known split-step Fourier method. Our study revealed feasibility of generating parabolic pulses in such a dispersion-decreasing Bragg fiber of length as short as 1 m. We have also studied the effect of third order dispersion on generated parabolic pulse, which is an important deteriorating factor in such applications. The effective single-mode operation of the proposed device is achieved through appropriate tailoring of the outer cladding layers.     

Scattering loss analysis and structure optimization of hollow-core photonic bandgap fiber

Effects of core structure in 7 cell hollow-core photonic bandgap fibers (HC-PBGFs) on scattering loss are analyzed by means of investigating normalized interface field intensity. Fibers with different core wall thickness, core radius and rounding corner of air hole are simulated. Results show that with thick core wall and expanded core radius, scattering loss could be greatly reduced. The scattering loss of the HC-PBGFs in the wavelength range of 1.5–1.56 μm could be decreased by about 50 % of the present level with optimized core structure design.     

Saturated absorption spectroscopy of acetylene gas inside large-core photonic bandgap fiber

Saturated absorption spectroscopy is performed on the acetylene nu(1) + nu(3) band near 1532 nm inside photonic bandgap fibers of small (approximately 10 microm) and large (approximately 20 microm) core diameters. The observed linewidths are narrower in the 20 microm fiber and vary from 20 to 40 MHz depending on pressure and power. Variations in the background light transmission, attributed by others to surface modes, are significantly reduced in the 20 microm fiber. The optimum signal for use as a frequency reference in a 0.8 m long, 20 microm diameter fiber is found to occur at about 0.5 torr for 30 mW of pump power. The saturation power is found by modeling the propagation and attenuation of light inside the fiber.