- 标题
- 摘要
- 关键词
- 实验方案
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Self-starting mode-locked Tm-doped fiber laser using a hybrid structure of no core - graded index multimode fiber as the saturable absorber
摘要： We experimentally demonstrated a passively mode-locked all-fiber Tm laser using a no-core-graded-index multimode fiber structure as a saturable absorber based on the nonlinear multimode interference. Stable fundamentally mode-locking operation was obtained at a pump threshold of 180 mW. The output soliton pulses had a centre wavelength, spectral width, pulse duration, and repetition rate of 1895.7 nm, 3.3 nm, 1.25 ps, and 18.91 MHz, respectively. This is a simple, low-cost, stable, and convenient laser oscillator, with many potential applications in eye-safe ultrafast photonics.
关键词： Nonlinear multimode interference,Fiber laser,Mode-locked laser
更新于2025-11-28 14:24:03
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Large diameter coreless fiber as a saturable absorber for erbium doped fiber laser cavity based on multimode interference
摘要： We demonstrated a Q-switched erbium-doped fiber laser (EDFL) based on large diameter coreless fiber without intra-cavity tuning element for the first time. A single mode fiber –coreless fiber –single mode fiber (SNCFS) structure was employed as a passive Q-switcher relies on Kerr nonlinearity associated with multi-mode interference (MMI) effect. By splicing 10 cm of 125 μm in diameter coreless fiber (NCF) between two single mode fibers (SMFs), C-band Q-switched EDFL with 3-dB bandwidth of 0.138 nm was successfully obtained, making it a simple, compact and easily handling modulation device. A stable Q-switched pulses were achieved with a pump threshold of 188 mW. Pulse repetition rate ranges from 73.3 to 92.0 kHz, minimum pulse width of 3.5 μs and maximum energy of 50.9 nJ were recorded.
关键词： Q-switched,Fiber lasers,Multimode interference
更新于2025-11-28 14:23:57
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Refractive index sensor based on ultrafine tapered single-mode nocladding single-mode fiber structure
摘要： A refractive index (RI) sensor based on a tapered no cladding fiber (NCF) is proposed theoretically and experimentally. The RI sensor is fabricated by splicing a NCF in the middle of two single mode fibers (SMF), and then the NCF is tapered to get lower waist diameter. Due to the lack of cladding, surrounding refractive index (SRI) can directly affect the light propagation of NCF, and the decrease of diameter can further improve the RI sensitivity by strengthening the evanescent field. The sensitivity with different lengths and waist diameters of NCF is investigated. It is observed that there are different linear relationships in different refractive interval and the RI sensitivity increases obviously with the waist diameter decreasing, especially when it is below 30 μm. RI sensitivity of the sensor reaches 686 nm/RIU when the waist diameter is 13 μm and SRI is at the range of 1.333–1.350. The sensor can be widely used in biosensing for its simple operation and high sensitivity at low SRI.
关键词： Refractive index sensor,Multimode interference,No cladding fiber,Tapering
更新于2025-11-28 14:23:57
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[IEEE 2018 IEEE 15th International Conference on Group IV Photonics (GFP) - Cancun (2018.8.29-2018.8.31)] 2018 IEEE 15th International Conference on Group IV Photonics (GFP) - Ultra Low Loss Asymmetric Multimode Interference Power Splitters
摘要： Ultra low loss arbitrary-ratio multimode interference (MMI) splitters are realized by utilizing tilted tapers with minimum excess loss predicted to be 0.05dB and the maximum no more than 0.215dB. the comparison in Fig1(b), (c) and (d), the joggle phenomenon is eased by using tilted tapers and the corresponding excess loss is also reduced.
关键词： multimode interference,arbitrary-ratio power splitter,Silicon Photonics
更新于2025-09-23 15:22:29
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Fiber Vector Bend Sensor Based on Multimode Interference and Image Tapping
摘要： A grating-less fiber vector bend sensor is demonstrated using a standard single mode fiber spliced to a multimode fiber as a multimode interference device. The ring-shaped light intensity distribution at the end of the multimode fiber is subject to a vector transition in response to the fiber bend. Instead of comprehensive imaging processing for the analysis, the image can be tapped out by a seven-core fiber spliced to the other end of the multimode fiber. The seven-core fiber is further guided to seven single mode fibers via a commercial fan-out device. By comparing the relative light intensities received at the seven outputs, both the bend radius and its direction can be determined. Experiment has shown that a slight bend displacement of 10 μm over a 1.2-cm-long multimode fiber in the X direction (bend angle of 0.382°) causes a distinctive power imbalance of 4.6 dB between two chosen outputs (numbered C4 and C7). For the same displacement in the Y direction, the power ratio between the previous two outputs C4 and C7 remains constant, while the imbalance between another pair (C3 and C4) rises significantly to 7.0 dB.
关键词： fiber sensors,bend sensors,multimode interference,fiber imaging
更新于2025-09-23 15:22:29
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Recent progress in all-fiber non-Gaussian optical beam shaping technologies
摘要： Rapid development of fiber lasers are being followed by wide ranges of applications in laser processing technologies. One of the key parameters to determine the laser-matter interaction is beam shape and there have been intense research activities on beam shaping using bulk-optics. However, fiber optic solutions would take clear advantages over bulk-optics especially for fiber laser sources in terms of the beam conversion efficiency, the throughput power, and the compact footprint. In this article, all-fiber optical beam shaping technologies are reviewed and they are categorized as the phase front modification on the fiber facet, the surface plasmonics on fiber, all-fiber Fourier transformation, and multimode interference. Their physical principles, beam shaping capability, and some of the novel applications are explained
关键词： Phase front engineering,Laser beam,Surface plasmon polariton,Beam Shaping,Multimode Interference,Fourier Transform,Fiber Optics,Single mode optical fiber
更新于2025-09-23 15:21:21
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A nanosensor with ultra-high FOM based on tunable malleable multiple Fano resonances in a waveguide coupled isosceles triangular resonator
摘要： A simple plasmonic structure, which is made up of a metal baffle in the middle of the metal–insulator–metal (MIM) waveguide coupled with an isosceles triangular cavity, is reported to achieve triple Fano resonances. These Fano resonances are numerically calculated by the finite element method (FEM). Besides, the multimode interference coupled mode theory (MICMT) and the standing wave theory are used for analyzing the Fano resonances phenomenon. On the one hand, these three Fano resonances can be independently tuned by adjusting the structural parameters, which makes the design of highly integrated photonic circuits more flexible. On the other hand, the proposed structure is well malleable and can be easily extended to a quintuple Fano system by introducing a ring resonator. Furthermore, the suggested structure can act as a high efficient refractive index (RI) sensor, yielding a great sensitivity of 1200 nm/RIU and a ultra-high maximal figure of merit (FOM) value of 3.0 × 106. Comparing with other similar sensors, our structure has relatively good sensitivity and it is superior to other structures in the maximal FOM, which obviously demonstrates its excellent nano-sensing performance.
关键词： Multiple Fano resonances,Multimode interference coupled mode theory (MICMT),Refractive index (RI) sensor,Ultra-high FOM,Surface plasmon polaritons (SPPs)
更新于2025-09-23 15:21:01
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Simultaneous measurement of magnetic field and temperature based on NCF cascaded with ECSF in fiber loop mirror
摘要： In this paper, we propose and experimentally demonstrate a dual-parameter sensor based on no-core fiber (NCF) cascaded with elliptical-core spun fiber (ECSF) in a Sagnac loop. Both NCF and ECSF are sealed in a capillary with the magnetic fluid to detect the magnetic field and temperature simultaneously. By introducing a section of NCF inside an elliptical-core spun fiber loop mirror (E-FLM) with optimizing fiber length, two extinct dips can be observed from 1480 to 1680 nm in the transmission spectrum. One dip is the result of multimode interference (MMI), while the other is induced by Sagnac interference of E-FLM. Hence, the simultaneous measurement of magnetic field and temperature can be realized by monitoring the shift of different wavelengths of two dips. Experimental results show that the dip of MMI is sensitive to the magnetic field (713.07 pm/mT), while the E-FLM has almost no response to magnetic field. For the two dips monitored in the temperature measurement, the sensitivities of proposed sensor are ?34.8 pm/°C and 304.55 pm/°C, respectively.
关键词： Multimode interference,Fiber loop mirror,Magnetic field measurement,Temperature measurement
更新于2025-09-19 17:15:36
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Broadband Mid-Infrared Directional and Multimode Interference Couplers in GLS Glass Fabricated using Femtosecond Laser Direct-Writing
摘要： The first broadband directional and multimode interference couplers for the mid-infrared centred around 4 μm wavelength are demonstrated. The devices are inscribed into commercial chalcogenide glass (Gallium-Lanthanum-Sulfide, GLS) provided by the University of Southampton using a tightly focused 800 nm, 5.1 MHz repetition rate femtosecond laser. Low loss waveguides are formed by placing 3 individual laser written tracks next to each other, resulting in propagation losses as low as 0.22 dB/cm. These waveguides are used to create asymmetric directional couplers, where the propagation constant in one arm is tailored to flatten the chromatic response of the device. By locally changing the feedrate at which the sample is translated through the focus, a change in propagation constant is obtained in the coupling region of the device. This yields a 3 dB coupler with a wavelength flattened response over a 500 nm wavelength band for ±5% variation in the coupling ratio compared to < 200 nm for a symmetric directional coupler. Multimode interference couplers were created by placing 26 laser inscribed tracks next to each other to form a 140 μm wide multimode interference region with lengths ranging from 5 to 10 mm. Asymmetry inside the multimode interference regions induced by the sequential writing process results in port dependent cross coupling ratios. Yet, close to 3 dB coupling was found for an 8.1 mm long device when injecting into the left input. The device features nearly perfect achromaticity across 3.75 to 4.25 μm.
关键词： GLS glass,mid-infrared,multimode interference couplers,femtosecond laser direct-writing,directional couplers
更新于2025-09-12 10:27:22
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Applications of Silicon Photonics in Sensors and Waveguides || New Approach to Mach-Zehnder Interferometer (MZI) Cell Based on Silicon Waveguides for Nanophotonic Circuits
摘要： In this chapter, we present a new scheme for Mach-Zehnder Interferometer (MZI) structure based on only one 4×4 multimode interference (MMI) coupler. We design the new MZI cell on the silicon on insulator (SOI) platform. The MZI based on directional coupler and 2×2 MMI coupler is also investigated in detail. The new MZI cell is a basic building block for photonic applications such as optical quantum gate, optical computing and reconfigurable processors. The numerical simulations show that our approach has advantages of compact size, ease of fabrication with the current complementary metal oxide semiconductor (CMOS) circuitry.
关键词： multimode interference,finite difference time difference,directional coupler,modified effective index method,multimode waveguide,finite difference method,silicon on insulator
更新于2025-09-11 14:15:04