In this work, an octagonal Penrose-type photonic quasi-crystal fiber (PQF) with dual-cladding is proposed. By optimizing three geometric degrees of freedom, the PQF exhibits ultra-flattened near-zero dispersion of 0.014±0.293  ps/nm/km, ultra-low order confinement loss of 10−4  dB/km, and large effective mode area of over 16.2  μm2 in a broadband of wavelength from 1.27 to 1.67 μm, covering almost all optical communication bands. At the common communication wavelength 1.55 μm, completely opposite trends of the dispersion and the confinement loss varying with the air-filling factor in the inner cladding are demonstrated. In addition, the robustness of optical properties including dispersion, confinement loss, and effective mode area in this PQF is discussed, assuming a deviation ±3% of all air holes.

Broadband ultra-flattened dispersion, ultra-low confinement loss and large effective mode area in an octagonal photonic quasi-crystal fiber.

A novel polarization filter based on a sunflower-type photonic quasi-crystal fiber (PQF) is proposed in this paper. We also discuss different methods to tune the filter wavelength. The proposed filter can efficiently produce polarized light with visible wavelengths by using the resonance between the second-order surface plasmon polariton mode and the core mode of the PQF. The filtered wavelength can be tuned between 0.55 µm and 0.68 µm by adjusting the thickness of the gold film. When the thickness of the gold film is 25.3 nm, the resonance loss in the y-polarized direction reaches 11707 dB m−1 for a wavelength of 0.6326 µm, and the full width at half maximum is only 5 nm. Due to the flexible design and absence of both polarization coupling and polarization dispersion, this polarization filter can be used in devices that require narrow-band filtering.

https://iopscience.iop.org/article/10.1088/1361-6463/aab4ce/pdf

Polarization filtering in the visible wavelength range using surface plasmon resonance and a sunflower-type photonic quasi-crystal fiber

We propose the use of an erbium-doped fiber laser based on a polarization-maintaining fiber Bragg grating (PM-FBG) and all-fiber Mach–Zehnder interferometer (MZI) to realize a quadruple-wavelength 1.5-μm laser output. In the proposed system configuration, a 1535-nm center wavelength PM-FBG acts as the wavelength selector. The dual-pass MZI is fabricated using two couplers with a 50:50 splitting ratio, and the wavelength spacing of the comb is varied by using a spectrum power-driven optical fiber delay line inserted in MZI. The working threshold in the experiment is 82 mW. Tunable lasers of single-, dual-, triple-, and quadruple-wavelengths can be realized by adjusting the polarization controller. The generated wavelengths are in the range of 1534 to 1534.6 nm, the wavelength space is 0.2 nm, and the 3 dB linewidth is less than 0.05 nm. The power fluctuation is observed to be less than 0.912 dB, and the signal-to-noise ratio (SNR) is larger than 34.9 dB at 26 °C over a scan time of 10 min.

Tunable Multiwavelength Erbium-Doped Fiber Laser Employing PM-FBG and Mach–Zehnder Interferometer with Optical Fiber Delay Line

https://iopscience.iop.org/article/10.1088/1361-6463/ab2369/pdf

Robust transmission of orbital angular momentum mode based on a dual-cladding photonic quasi-crystal fiber

An all-fiber comb filter using a tapered-erbium-doped fiber in a Mach-Zehnder interferometer structure is presented. The free spectral range, extinction ratio, bandwidth, and interference pattern of the comb filter can be shaped by controlling the taper waist length and the length of up and down taper transition regions. By varying the taper waist length from 5 to 25 mm, the free spectral range changes from 14.7 to 1.0 nm, and the linewidth varies from 3.3 to 0.3 nm, respectively. We demonstrate a tunable dual-wavelength laser by using the tapered-erbium-doped fiber as a gain medium as well as a wavelength-selective element. The laser can be tuned at a resolution of 0.2 nm with a side-mode suppression ratio of up to 46.88 dB and a linewidth of 0.09 nm.

Tapered-EDF-Based Mach–Zehnder Interferometer for Dual-Wavelength Fiber Laser

A stable and switchable dual-wavelength polarization-maintaining erbium-doped fiber ring laser is proposed and demonstrated experimentally by using a novel filter, which is formed from dual-pass Mach-Zehnder interferometer incorporating a sagnac loop. By adjusting the polarization controllers, the output laser can be switched between single- and dual-wavelength. The wavelength spacing of the dual-wavelength can be tuned from 0.084 to 4.26 nm. Its 3-dB bandwidth and side mode suppression ratio are less than 0.015 nm and higher than 64 dB, respectively. In addition, the peak power fluctuation and wavelength shift are monitored to be less than 0.5 dB and 0.01 nm during an hour, respectively. The characteristics of the novel filter in experimental measurement accord with the result of theoretical analysis.

Switchable Dual-Wavelength PM-EDF Ring Laser Based on a Novel Filter

Design of a highly nonlinear twin bow-tie polymer photonic quasi-crystal fiber with high birefringence

A highly nonlinear photonic quasi-crystal fiber with low confinement loss and flattened dispersion

Highly birefringent ZBLAN photonic quasi-crystal fiber with four circular air holes in the core

A dual-pass Mach–Zehnder interferometer filter using a section of twin-core fiber (TCF) loop mirror is proposed. The filter is theoretically and experimentally studied for various interferometer arm difference when TCF length is constant. Theoretical results are validated by the experimental demonstration and in good agreement with the experimental results. And then, by using the filter in a ring fiber laser, a stable and switchable dual-wavelength lasing is obtained experimentally. The 3-dB bandwidth and the SMSR of the output laser are 0.015 nm and higher than 62.4 dB, respectively. The peak power fluctuation and wavelength shift are also monitored to be less than 0.04 dB and 0.02 nm over an hour at room temperature. Furthermore, the output laser can be switched between single and dual wavelength by carefully adjusting the PCs. The experimental results show that the filter can suppress mode competition effectively, improve the SMSR availably, and enhance the stability of the output lasing.

https://link.springer.com/content/pdf/10.1007%2Fs00340-013-5454-x.pdf

Wei Su

Papers

Switchable Dual-Wavelength PM-EDF Ring Laser Based on a Novel Filter

Design of a highly nonlinear twin bow-tie polymer photonic quasi-crystal fiber with high birefringence

A highly nonlinear photonic quasi-crystal fiber with low confinement loss and flattened dispersion

Highly birefringent ZBLAN photonic quasi-crystal fiber with four circular air holes in the core

A dual-pass Mach–Zehnder interferometer filter using a TCF loop mirror for double-wavelength fiber lasers