Single-polarization Photonic Crystal Fiber Research Articles

Single-polarization photonic crystal fiber filter composed of elliptical gold films

A metallic photonic crystal fiber (PCF) filter based on surface plasmon resonance is designed and investigated by the full-vector finite-element method. The inner wall of the air holes in the PCF is coated with gold layers of different thicknesses. The x-polarized and y-polarized confinement losses of the core mode are as high as 1920.36 dB / cm and as low as 3.29 dB / cm at 1310 nm, respectively. For a fiber length of 1000 μm, the crosstalk of the filter is 1665.14 dB at 1310 nm and the available optical bandwidth is 779 nm. The results show that the PCF filter has excellent prospect in optical information processing.

A Broadband Single Polarization Photonic Crystal Fiber Filter Around 1.55 μm Based on Gold-Coated and Pentagonal Structure

In this paper, a broadband single polarization photonic crystal fiber (PCF) filter around 1.55 μm is presented on account of surface plasmon resonance. The finite element method is used to investigate the performance of the filter, and the structure parameters’ influences on the performances of the filter are studied. Due to asymmetry which is caused by the pentagonal arranged cladding air holes, the confinement loss of the Y polarization core mode reaches to as high as 1751.05 dB/cm around 1.55 μm, while the loss for the X polarization mode is only 0.22 dB/cm. This indicates that a loss ratio of 7959.32 is achieved and the crosstalk value is up to 304.15 dB with 200 μm PCF around 1.55 μm. Moreover, the bandwidth of 20 dB crosstalk value is 1010 nm with a wavelength coverage from 1.39 to 2.40 μm. Numerical simulations also show that the designed filter has good tolerance to structural deformation. Therefore, the proposed pentagonal filter has great potentials in the application of broadband communication system.

Design of single-polarization single-mode photonic crystal fiber filter with four small holes near the core based on second-order and third-order surface plasmon polariton modes

A single-mode single-polarization photonic crystal fiber (SMSP-PCF) filter at the wavelengths of 1.125 and 1.31 μm based on surface plasmon resonance is proposed and studied by the finite element method. Numerical results indicate that compared with the filter with the same size of holes near the core, the filter with four small holes near the core makes its extinction ratio (ER) at the wavelengths of 1.125 and 1.31 μm twice as large. That is, when the fiber length is 500 μm, the ER at 1.125 μm increases from 33.43 to 58.62 dB, and the ER at 1.31 μm increases from 129.41 to 244.85 dB. Furthermore, the designed SMSP-PCF filter also has a good structural tolerance. The proposed optical fiber filter has excellent performance of compact structure, high ER and good structural tolerance, and can be used in an integrated communication transmission system.

Tunable single-polarization bimetal-coated and liquid-filled photonic crystal fiber filter based on surface plasmon resonance

A bimetal-coated single-polarization photonic crystal fiber (PCF) filter based on surface plasmon resonance (SPR) with a liquid-filled structure is designed and calculated by the finite element method (FEM). The filter has many excellent properties. The y-polarized and x-polarized modes can simultaneously filter at 1310 nm and 1560 nm with unwanted losses 544.3 dB/cm and 147.3 dB/cm, respectively, corresponding to polarized losses as low as 12.3 dB/cm and 24.0 dB/cm. The filtering range can be tuned by adjusting the diameter of the outer air holes (d1), the diameter of the inner air holes (d2), and liquid refractive index n. The filtering ranges of x-polarization and y-polarization are 1550-1990 nm and 1310-1830 nm, respectively. The crosstalk (CT) values are 462.0 dB and -107.1 dB and corresponding available bandwidths are 224 nm and 504 nm at 1310 nm and 1560 nm, respectively.

A Double-Cladding Single Polarization Photonic Crystal Fiber and Its Structure Deviation Tolerance

We propose a novel broadband single-polarization single-mode (SPSM) photonic crystal fiber with hexagonally latticed circular airholes. Combined with our fabricated polarization maintaining fiber, it has demonstrated that the enlarged air holes in the outmost layer are superior for the confinement loss reduction. At the optimized parameters, the wavelength of SPSM region ranges from 1.52 to 2.13 $\mu$ m, where only y-polarized fundamental mode exists and the confinement loss is 0.051 dB/km at 1.55 $\mu$ m. The influence of realistic fabrication errors involving structure deviation on SPSM operation has also been systematically investigated.

Single polarization photonic crystal fiber filter based on surface plasmon resonance

In this paper, we propose a photonic crystal fiber (PCF) polarization filter based on surface plasmon resonance (SPR) characteristics. Gold nanowire is used as the active plasmonic material. Light into silica core becomes coupled to gold nanowire stimulating SPR. It splits light into two orthogonal (x-polarization and y-polarization) polarization in the second order of surface plasmon polarization. Numerical investigations of the proposed PCF filter is finite element method (FEM). By tuning the diameter of gold nanowire and shifting their position, the performance of the proposed PCF filter is inspected rigorously. Filtering of any polarization can be obtained by properly placing the metal wires. The maximum confinement loss of x-polarization is 692.25 dB/cm and y-polarization is 1.13 dB/cm offers at resonance position 1.42 μm. Such a confinement loss difference between two orthogonal polarizations makes PCF a talented candidate to filter devices. Consequently, the recommended PCF structure is useful for polarization device.

A tunable single-polarization photonic crystal fiber filter based on surface plasmon resonance

A tunable single polarizing filter is proposed by selectively coating gold film on the air holes of photonic crystal fiber (PCF). The polarization properties of the PCF filter are evaluated by the finite-element method. Simulation results show that the loss of y-polarized core mode at 1250 and 1550 nm is 136.23 and 839.73 dB/cm, respectively. Furthermore, we innovatively combine stable modulation with flexible modulation. To be specific, the resonance wavelengths are slowly controlled in a small wavelength range by altering the diameter of the air-hole-coated gold film, while the resonance wavelengths are flexibly controlled in a wide wavelength range by altering the thickness of the gold film or the diameter of the small air holes. When the length of the PCF is 500 µm, the bandwidth of extinction ratio greater than − 20 dB is only 60 nm at the communication window of 1550 nm. It is beneficial to fabricate a narrow-band polarization filter.

A Photonic Crystal Fiber Polarized Filter at 1.55 μm Based on Surface Plasmon Resonance

A single-polarization photonic crystal fiber (PCF) based on surface plasmon resonance (SPR) is proposed. Finite element method is employed in simulating the PCF with gold-coated. The resonance wavelength can be modulated by changing the thickness of gold layer. At the resonance wavelength 1.55 μm, the loss of y-polarized mode is much larger than the loss of x-polarized mode. When the fiber length is set to 2 mm, the value of extinction ratio reaches to −118.7 dB, the y-polarized mode is suppressed and only x-polarized mode can be guided. The fiber is applicable in the production of single-polarization filter. The PCF has a simple structure and a big error tolerance, it has a good practicability.

Broadband Single-Polarization Photonic Crystal Fiber Based on Surface Plasmon Resonance for Polarization Filter

A broadband single-polarization photonic crystal fiber polarized filter based on surface plasmon resonance is proposed based on finite element method. Numerical simulations show the confinement loss of y-PCM (y-polarized core mode) is much higher than that of x-PCM (x-polarized core mode) in the wavelength range 1.20–1.63 μm. The confinement loss of y-polarized mode is 45,240 and 10,200 dB/m at the communication wavelength 1.31 and 1.55 um, respectively, and the corresponding loss of x-polarized mode is just 90 and 80 dB/m. When the fiber length is 3 mm, the bandwidth of extinction ratio better than -20 dB is greater than 430 nm covering almost all the communication wavelength. To our best knowledge, the bandwidth is the widest. The impacts of structural parameters on the resonance characteristics are also discussed. The structure could be further optimized for better result.

Amplifier similariton oscillator using 10 m photonic crystal fiber

Ultrashort pulse laser with a repetition rate of below 10 MHz is suitable for a variety of micromachining applications to avoid plasma shielding effects. Besides, the parabolic pulse possesses clean wings, short pulse duration, and large peak power because only the linear chirp is accumulated during the propagation. Based on these two points, a similariton oscillator with a repetition rate of below 10 MHz is a most perfect seed source of an amplification system for micromachining. In this paper, an amplifier similariton oscillator with dispersion map based on a piece of 10 m Yb-doped large-mode-area single-polarization photonic crystal fiber is demonstrated. The semiconductor saturable absorber mirror is employed in the linear cavity as an end mirror to initiate and maintain the mode-locking operation. An adjustable slit is adopted between the end mirror and grating pair in another arm, as a central wavelength adjuster and the spectral filter to ensure the laser operational wavelength in accordance with the working wavelength of semiconductor saturable absorber mirror and the stability of mode-locking operation. The stable single-pulse mode-locking operation can be achieved by adjusting the intracavity dispersion and the operating wavelength. With the net cavity dispersion of-0.89 ps2, a spectrum with steep and smooth edges is obtained, which means that the laser does not operate in the soliton regime but in the dispersion-mapped amplifier similariton regime. A highest output power of 820 mW is obtained with a pulse duration of 6.2 ps and spectral width of 3.84 nm under a pump power of 12.8 W. The repetition rate is 8.6 MHz, corresponding to a pulse energy of 95 nJ. It is the first time that the similariton with a repetition rate of lower than 10 MHz and a highest pulse energy of 95 nJ from a similariton laser has been achieved, to the best of our knowledge. Numerical simulation results confirm that the self-similar evolution is achieved in the gain fiber, and the parabolic-and gauss-shaped pulse can be emitted at the zero-order reflection of the grating and after the slit, respectively.

Design for a Single-Polarization Photonic Crystal Fiber Wavelength Splitter Based on Hybrid-Surface Plasmon Resonance

A novel single-polarization photonic crystal fiber wavelength splitter based on hybrid-surface plasmon resonance is proposed. A full-vector finite-element method is applied to analyze the guiding properties. Numerical simulations show that the proposed splitter, which is only several hundred microns in length, gives single polarization in the 1.31-μm and 1.55-μm bands. The loss of the unwanted polarized mode is 102.6 and 245.0 dB/cm in the two aforementioned communication windows, respectively, and the corresponding insertion loss is as low as 3.5 and 1.7 dB/cm, respectively. Moreover, the dependence of the bandwidth on the fiber length is given, and according to that function, the bandwidth can reach 40 nm (1.31-μm band) and 100 nm (1.55-μm band) when the fiber length is up to 1 mm. Additionally, the tolerances for a realistic fabrication are analyzed. In the last part, we discuss other methods to deal with an anticrossing phenomenon in detail.

Single-polarization photonic crystal fibers with a multiplex structure

A new kind of single-polarization photonic crystal fiber (PCF) is proposed. Two kinds of multi-component glasses and the air are selected as working materials. Through using the full vector finite element method (FEM) and the perfectly matched layers (PML), the polarization-maintaining characteristic and the confinement loss of the fiber are analyzed, respectively. In addition, the single-polarization region of the fiber around 1.55 im is discussed. Numerical simulations show that the fiber maintains single-polarization operation within the wavelength range of 1.421 1.696 im. The birefringence can reach 6.988×10−3, and the confinement loss is as low as 0.012 dB/m when 7 layers of ring holes are arranged in the cladding at e=1.55 im.

Numerical investigation on single-mode single-polarization photonic crystal fiber using resonant absorption effect

In this paper, a novel single-mode single-polarization photonic crystal fiber using resonant absorption effect has been put forward for the first time. A full vector finite element method is employed to simulate the fiber properties, including mode field distribution, confinement loss，bandwidth and extinction ratio. Numerical results show that very large bandwidth of single-mode single-polarization operation can be attained and extremely high extinction ratio can be achieved with low loss penalty. The influence of structural parameters on the fiber performance has been investigated. The research results will be instructive for the design and fabrication of new high performance single-mode single-polarization fibers.

Microjoule-level all-polarization-maintaining femtosecond fiber source

We report on a high-power, high-energy femtosecond fiber source based on direct amplification of parabolic pulses from an environmentally stable passively mode-locked fiber oscillator in an Yb-doped single-polarization photonic crystal fiber. The special pulse shape allows for the generation of high-quality femtosecond pulses beyond nonlinearity limits. The system delivers a pulse energy of 1.2 microJ (21 W average power) at a repetition rate of 17 MHz and a pulse duration of 240 fs in a linearly polarized beam with diffraction-limited quality.

Absolutely Single Polarization Photonic Crystal Fiber

An optical fiber that guides only one polarization mode of a light signal is realized by using highly birefringent pure silica photonic crystal fiber. The fiber guides only one polarization mode at wavelengths longer than 1450 nm. A polarization dependent loss of 196 dB/km with a 28 dB/km transmission loss is achieved at a wavelength of 1550 nm.