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Helical Long-Period Gratings Inscribed in Polarization-Maintaining Fibers by CO2-Laser
摘要： We demonstrate fabrication of helical long-period gratings (HLPGs) in a polarization-maintaining fiber using CO2-laser. The maximum polarization dependent loss (PDL) of the grating was measured to be more than 30 dB at the resonance wavelength. The HLPG was found to have a high index sensitivity of -7248.6 nm/RIU when the surrounding refractive index changes in the range of 1.4470-1.4600, temperature sensitivity of 158.8 pm/°C, and strain sensitivity of 3.17 pm/με. The twist sensitivities based on intensity variation were measured to be 5.98 dB/ (rad/m) (co-directional twist) and -5.97 dB/ (rad/m) (contra-directional twist), respectively. The demonstrated grating devices have promising applications as high-sensitivity fiber sensors, PDL compensator etc.
关键词： optical fiber sensors,Fiber gratings,polarization-maintaining fibers,helical long-period gratings
更新于2025-11-28 14:24:03
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All-polarization-maintaining dual-wavelength mode-locked fiber laser based on Sagnac loop filter
摘要： We demonstrate an all polarization-maintaining (PM) fiber based dual-wavelength mode-locked Er-fiber laser. A nonlinear amplifying loop mirror (NALM) with an intracavity nonreciprocal phase shifter is used for self-started mode-locking. A short segment of PM fiber is angle-spliced to the NALM, functioning as a PM Sagnac loop filter, thus enabling dual-wavelength mode-locking. The wavelength separation is solely determined by the angle-spliced PM fiber length. Stable dual-wavelength mode-locking operation is switchable between 1570/1581 nm and 1581/1594 nm. The two-color pulse trains oscillating in the same cavity have an inherent offset repetition rate of ~1 kHz owing to cavity dispersion, allowing future high precision dual-comb applications with a simple and robust configuration.
关键词： polarization-maintaining fiber,dual-comb applications,dual-wavelength mode-locked fiber laser,Sagnac loop filter
更新于2025-11-28 14:24:03
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Robust 1.7-μm, all-polarization-maintaining femtosecond fiber laser source based on standard telecom fibers
摘要： We demonstrate a compact 1.7-μm all-polarization-maintaining (PM) ultrafast fiber laser source, which employs soliton self-frequency shift (SSFS) in an optical fiber as the dominant spectral-shifting mechanism. The laser generates stable pulses with 384 fs pulse width and 102 MHz repetition rate centered at 1.7 μm with 7 nm spectral bandwidth. The average power is about 35 mW with a high conversion efficiency of 66 %. The measured root mean square (RMS) output power stability over 10 hours is as low as 0.22 %. Both experimental and simulation results demonstrate that this laser has a potential to improving multiphoton imaging depth.
关键词： all-polarization-maintaining,multiphoton imaging,femtosecond fiber laser,soliton self-frequency shift,1.7-μm
更新于2025-11-28 14:23:57
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An interferometric structure with a dual-resonance long period grating for strain sensing
摘要： Spectral characteristics and amplitude tunability of a long period grating with a dual-resonance inside fiber loop mirror are studied in terms of applied stress caused by elongation. Inserting the polarization controller between grating and part of polarization maintaining fiber in the loop structure enables tuning of resonance and interferometric peaks. The maximum sensitivity of demonstrated sensor is of 1.943 dB/mε for the range of 1.1–4.4 mε. Combination of these two optical components allows to measure strain in a wider range comparing with sensors based on standard long period grating.
关键词： Fiber loop mirror,Polarization controller,Polarization maintaining fiber,Strain sensor,Long period grating
更新于2025-09-23 15:23:52
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Dispersion flattened extremely high-birefringent kagome lattice elliptic core photonic crystal fiber in THz regime
摘要： A highly birefringent elliptic porous-core photonic crystal fiber with kagome lattice cladding has been presented for terahertz (THz) wave transmission. The slotted airholes inside the elliptic core effectively disrupt the symmetry of the porous-core which offers extremely high modal birefringence whereas the kagome cladding structure results in significantly low effective material loss (EML). The birefringence of the proposed structure is 9.73 × 10?2 for y-polarized mode at an operating frequency of 1 THz. The suggested structure also provides very flat dispersion over a bandwidth of 300 GHz. It is highly expected that this elliptic core waveguide would be remarkably useful in numerous polarization maintaining THz applications.
关键词： Photonic crystal fibers,Microstructured fibers,Fibres, polarization-maintaining,Optical communications,Fiber design and fabrication
更新于2025-09-23 15:23:52
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Broadband generation of the first-order OAM modes in two-mode fiber by offset splicing and fiber rotating technology
摘要： We demonstrate a simple, compact, and cost-effective all-fiber structure to generate the first-order orbital angular momentum (OAM) modes over a broad wavelength range. The offset splicing between a polarization-maintaining single mode fiber (PM-SMF) and a two-mode fiber (TMF) is adopted to excite LP11 mode in the TMF from LP01 mode in SMF. Then the OAM ± 1,1 modes are generated by rotating a customized fiber rotator, which can modulate the phase difference of the two degenerate LP11 modes (OAM ± 1,1 = LP11a ± i × LP11b). The interference phenomenon formed between OAM and Gaussian beams, which displays a fork-shape or spiral interference pattern, is used to confirm the generation of OAM modes. It should be noted that a PM fiber coupler and PM-SMFs are utilized in the experiment, which can avoid coupling of modes with orthogonal polarizations and then improves the OAM mode stability. Besides, the complexity of the OAM generation system is also reduced because the devices like polarization controller and half-wave plate are omitted by employing PM fibers. Based on this simple offset splicing and fiber rotating technology, the broadband generation of OAM ± 1,1 modes are experimentally demonstrated in wavelength range of 1530–1566 nm.
关键词： Fiber rotating,Polarization-maintaining single mode fiber,Two mode fiber,Offset-splicing,Orbital angular momentum mode
更新于2025-09-23 15:23:52
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Pulse generation in an Yb-doped polarization-maintaining fiber laser by nonlinear polarization evolution
摘要： We demonstrated a self-started, long-term stable polarization-maintaining mode-locked fiber laser based on nonlinear polarization evolution technique. A polarized beam splitter was inserted into the cavity of the linear polarization-maintaining fiber laser to facilitate self-started mode-locking. Pulses with single pulse energy of 26.9 nJ and average output power of 73.9 mW were obtained at the pump power of 600 mW. The transmission characteristics of artificial saturable absorber used in this laser were analyzed theoretically, as well as the impact of the half wave plate’s state on mode-locking was discussed and the mode-locking range was obtained, which is well consistent with the experimental results.
关键词： nonlinear polarization evolution,Polarization-maintaining,mode-locking
更新于2025-09-23 15:21:01
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Tunable optical frequency comb from a compact and robust Er:fiber laser
摘要： We report on a compact and robust self-referenced optical frequency comb with a tunable repetition rate, generated by an all-polarization-maintaining (PM) mode-locked Er-doped fiber laser. The spacing between comb teeth can be tuned above 300 kHz at a repetition rate of 101 MHz. The repetition rate and the carrier–envelope offset of the laser are stabilized separately, and the relative residual phase noises are determined to be 336 μrad and 713 mrad (1 Hz–1 MHz). The accurate frequency characteristics and the stable structure show great potential for the use of such a comb in applications of precision measurements.
关键词： fiber laser,optical frequency comb,all-polarization-maintaining,mode-locking
更新于2025-09-23 15:21:01
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Panda type few-mode fiber capable of both mode profile and polarization maintenance
摘要： We report the design, fabrication and characterization of panda type few-mode fiber (panda-FMF) capable of both mode profile and polarization maintenance, due to the use of two applied stress rods into the conventional FMF. The panda-FMF can support six spatial modes including LP01, LP11a, LP11b, LP21a, LP21b and LP02, and each possesses two orthogonal linear polarization modes. According to the characterization results of panda-FMF, we theoretically identify that the effective refractive index (RI) difference between either two spatial or orthogonal linear polarization modes is more than 1×10-4 over the C-band. Moreover, the experimental results verify that, both mode profile and polarization of high-order radially asymmetric modes can be perfectly maintained even under severe twist rate of 1.57 rad/m.
关键词： polarization-maintaining,fiber optics,Fiber design and fabrication,fibers
更新于2025-09-23 15:21:01
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Radiation induced attenuation in pure silica polarization maintaining fibers
摘要： Radiation-induced attenuation (RIA) at λ = 1.55 μm is studied in polarization-maintaining (PM) pure-silica-core optical fibers of the Panda-type under γ-irradiation and upon pulsed-X-ray-irradiation. For the first time, the RIA spectrum is compared under γ-irradiation in a Panda and in a non-PM fiber drawn from the same preform before embedding the stress-applying rods. It is found out that the chief RIA origins in the near-IR range in both fibers are an extremely short-lived band centered at ~1 eV and the tails of the classical bands due to strain-assisted self-trapped holes (STHs) at 1.63 and 1.88 eV. The former band is found to be many times more intense in the Panda; the latter bands, somewhat more intense in the non-PM fiber. The ~1-eV band proved to be composed of two Gaussian sub-bands centered at 0.95 and 1.12 eV. Under γ-irradiation, the composite ~1-eV band is found to be photobleached virtually fully by 1.55-μm light of 5-mW power, which results in manifold reduction of the total RIA. Upon pulsed irradiation, RIA in Pandas at large post-pulse times (> 1 ms–1 s) is found to fall off below the record low level demonstrated elsewhere by a non-PM pure-silica-core fiber. This fact is explained as being due to a smaller concentration of strain-assisted STHs in Pandas than in non-PM fibers. The concentration of strain-assisted STHs in Pandas is shown to increase with increasing the value of birefringence.
关键词： Radiation-induced attenuation,Self-trapped holes,Polarization-maintaining fiber
更新于2025-09-19 17:15:36