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Switchable dual-wavelength mode-locked fiber laser using Saganc loop mirror
摘要： We report an all-fiber switchable dual-wavelength mode-locked laser using a Sagnac loop mirror. In this laser, the Sagnac loop mirror acts as a tunable periodic filter, in which the wavelength spacing is determined by the length of the polarization maintaining fiber. With appropriate pump power, the mode-locked fiber laser can operate in both the tunable single-wavelength mode locking regime and the dual-wavelength mode locking regime by properly setting the states of the polarization controllers. In the single-wavelength mode locking regime, the laser achieves continuously tunable wavelength range from ～1551 nm to ～1562 nm. In the dual-wavelength mode locking regime, the laser can emit two stable asynchronous pulse trains with the central wavelengths of 1561.4 nm and 1551.1 nm, respectively. Due to the net negative dispersion of the laser cavity, the mode-locked pulse trains with different central wavelengths have different group velocities leading to a repetition rate difference of ～530 Hz.
关键词： Tunable wavelength,Dual-wavelength,Sagnac loop mirror,Mode-locked fiber laser
更新于2025-09-19 17:13:59
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[IEEE 2019 PhotonIcs & Electromagnetics Research Symposium - Spring (PIERS-Spring) - Rome, Italy (2019.6.17-2019.6.20)] 2019 PhotonIcs & Electromagnetics Research Symposium - Spring (PIERS-Spring) - Repetition Rate Adjustable Dual-wavelength Solitons Fiber Laser Based on Highly Nonlinear Fiber
摘要： A dual-wavelength soliton ?ber ring laser with adjustable repetition rate was reported. Through adding highly nonlinear ?ber (HNLF) as nonlinear medium in the ?ber ring cavity, the dual-wavelength bright-dark soliton pair can be formed. The 1st to 4th, 5th to 8th and 9th to 11th harmonics bright-dark solitons pairs were obtained by rotating the Polarization controller (PC) when the power are 160 mW, 230 mW and 340 mW, respectively. To investigate the in?uence of loss on the laser system, a variable optical attenuator (VOA) was embedded in the ring laser cavity. Then the dual-wavelength with Kelly sidebands was obtained by properly adjusting the PC and VOA. The center wavelengths of the dual-wavelength laser were located at 1557.8 nm and 1568.5 nm and the 3 dB bandwidths of two wavelengths are 2.2 nm and 2.1 nm, respectively. The spacing between the two wavelengths was 10.7 nm. Due to the existence of nonlinearity, the 1st to 22th harmonics bright solitons sequence (corresponding to the repetition rate tunable from 196.8 kHz to 4.33 MHz) was obtained by increasing the pump power. The intervals of bright-dark solitons pair and bright solitons all were 5.08 μs, which corresponds to fundamental repetition rates are 196.8 kHz. The signal-to-noise ratio of the bright solitons was approximately 58 dB, which means the operation of laser was stable.
关键词： harmonic solitons,dual-wavelength soliton,adjustable repetition rate,fiber ring laser,highly nonlinear fiber,bright-dark soliton pair
更新于2025-09-19 17:13:59
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Dual-wavelengths filter operating at visible wavelength region using subwavelength grating on waveguide structure
摘要： A dual-wavelength filter was experimentally demonstrated using subwavelength grating (SWG)/waveguide structure. We designed the structural parameters of the SWG and the waveguide to find the reflection peaks in the visible wavelength region. To investigate the optical response of the designed SWG/waveguide structure, finite-difference time-domain (FDTD) numerical calculations were performed for electromagnetic field distribution. The dual reflection peaks from our proposed structure were predicted in visible wavelength regions by the FDTD calculation. The calculated electromagnetic field distribution also revealed that the reflection peaks were associated with resonances in the SWG and waveguides. We fabricated the SWG/waveguide with typical electron-beam lithography techniques, and two reflection peaks were observed at wavelengths of 486 nm and 590 nm with bandwidths of 45 nm and 58 nm, respectively. These experimental results indicate that dual-wavelength filters can be successfully realized without complex fabrication processes.
关键词： Dual-wavelength filter,Waveguide,Guided mode,Subwavelength grating
更新于2025-09-19 17:13:59
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Generation of sub-nanosecond pulse in dual-wavelength praseodymium fluoride fibre laser
摘要： In this paper, we demonstrate a stable dual-wavelength pulsed output from a praseodymium doped fluoride fiber laser. These dual functions are induced by intensity-dependent transmission and loss due to the cavity birefringence. The two lasing wavelengths centered at 1298.26 nm and 1299.91 nm with a spacing of 1.65 nm and a 3 dB bandwidth of 0.11 nm and 0.13 nm respectively are obtained. The pulse width induced by the dual-wavelength laser falls within the picosecond region, with a repetition rate of 389 KHz and a maximum average pulse energy of 5.4 nJ.
关键词： fibre lasers,praseodymium doped fluoride (PDFFL),dual-wavelength
更新于2025-09-19 17:13:59
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Simulation and design of a compact GaAs based tunable dual-wavelength diode laser system
摘要： We present our design of a compact, integrated and tunable dual-wavelength diode laser system emitting around 785 nm, which is of interest for several applications like Raman spectroscopy and the generation of THz radiation. To achieve a more compact device compared to previous GaAs based designs two etch depths are realized, leading to shallowly etched ridge waveguides in regions were optical gain is applied and deeply etched waveguides used to enable compact integrated waveguide components. The device parameters are optimized using a numerically efficient simulation tool for passive waveguides. Subsequently, the entire laser system is further analyzed applying a sophisticated traveling-wave equation based model for active devices giving access to internal intensity and carrier density distributions. It is shown that active laser simulations are crucial to deduce critical and performance limiting design aspects not accessible via an all-passive simulation.
关键词： Tunable laser diodes,Dual-wavelength laser,Traveling-wave model
更新于2025-09-16 10:30:52
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Hybrid Integrated Semiconductor Lasers with Silicon Nitride Feedback Circuits
摘要： Hybrid integrated semiconductor laser sources offering extremely narrow spectral linewidth, as well as compatibility for embedding into integrated photonic circuits, are of high importance for a wide range of applications. We present an overview on our recently developed hybrid-integrated diode lasers with feedback from low-loss silicon nitride (Si3N4 in SiO2) circuits, to provide sub-100-Hz-level intrinsic linewidths, up to 120 nm spectral coverage around a 1.55 μm wavelength, and an output power above 100 mW. We show dual-wavelength operation, dual-gain operation, laser frequency comb generation, and present work towards realizing a visible-light hybrid integrated diode laser.
关键词： low-loss Si3N4 waveguides,dual-wavelength laser,laser frequency comb,InP semiconductor optical amplifier,integrated photonic circuits,semiconductor laser,hybrid integration,narrow intrinsic linewidth
更新于2025-09-16 10:30:52
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Debris and Smear Layer Removal in Curved Root Canals Using the Dual Wavelength Er,Cr:YSGG/Diode 940a??nm Laser and the XP-Endoshaper and Finisher Technique
摘要： Objective: To validate the capability of the dual wavelength laser (Er,Cr:YSGG and diode 940 nm) and the XP-Endoshaper and finisher in removing the smear layer from curved canals. Methods: Forty curved root canals were prepared using the R25 file of the Reciproc system. The teeth were randomly divided into five groups: G1: negative control irrigated with distilled water, G2: positive control irrigated with EDTA 17% and a final rinse of NaOCl 3%, G3: XP-Endoshaper and finisher with EDTA 17%, G4: dual wavelength Er,Cr:YSGG (1.25 W, 50 Hz, 50 ls) and diode 940 nm (2 W, 50% DC), and G5: dual wavelength Er,Cr:YSGG (2 W, 20 Hz, 50 ls) and diode 940 nm (2 W, 50% DC). Laser scanning microscope images (1000 · ) were scored with the Hu¨lsmann scoring system. Results: Superior smear layer removal was observed in G5 in comparison with G4, especially in the apical third of the canal. Furthermore, the XP-Endoshaper and finisher exhibited positive results in all parts of the canal. Conclusions: The higher power output of the Er,Cr:YSGG in the dual wavelength laser may be a suitable approach to remove the smear layer from the apical third of curved canals. Moreover, the XP-Endoshaper and finisher with EDTA could expose the dentinal tubules, however, the negative side effects of applying EDTA 17% for longer periods must be taken into consideration. This work is clinically significant as it addresses the main aim of endodontic treatment and provides a suitable method to remove the debris, smear layer, and bacterial remnants from the clinically challenging curved root canals.
关键词： diode 940 nm,dual wavelength laser,smear layer,Er,Cr:YSGG,curved canals
更新于2025-09-16 10:30:52
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Frequency expansion of efficient passively Q-switched orthogonally-polarized dual-wavelength laser
摘要： We report on the frequency expansion of e?cient passively Q-switched (PQS) orthogonally-polarized dual-wavelength laser for the ?rst time, to our knowledge. The dynamic of pulse synchronization for the PQS dual-wavelength laser was analyzed theoretically. With two Nd:YLF crystals, the simultaneous PQS orthogonally-polarized dual-wavelength laser at 1047 and 1053 nm was obtained with the maximum output powers of 4.5 and 4.2 W, respectively, resulting in a total optical-to-optical conversion e?ciency of 18.7%. The timing jitter between the 1047 nm main pulse and 1053 nm main pulse was 26.6 ns. Furthermore, substituting one of the Nd:YLF crystals for a Nd:YAG crystal, two sets of simultaneous orthogonally-polarized dual-wavelength lasers at 1047, 1064 nm and 1053, 1064 nm were generated with near 6 W of output power.
关键词： Passively Q-switched,Dual-wavelength laser,Diode-pumped lasers
更新于2025-09-16 10:30:52
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S/S+-Band Tunable Dual-wavelength Thulium doped Fluoride Fiber Laser
摘要： A simple S/S+-band dual-wavelength thulium doped fluoride fiber laser (DWFL) with tunable channel spacing is demonstrated. The system utilizes a 24 channel arrayed waveguide grating to control the spacing between the two lasing wavelengths. The widest spacing that can obtained between two lasing wavelengths is 17.49 nm, while the narrowest is 0.75 nm. The cavity loss in the DWFL is controlled using two variable optical attenuators to equalize the power of the two lasing wavelengths. The DWFL has a maximum signal to noise ratio (SNR) of approximately 49.60 dB and good stability over long periods of operation, with only minor SNR fluctuations of less than 5.00 dB observed. The DWFL’s output also has side-mode suppression ratio (SMSR) of between 0.12 dB and 1.56 dB, indicating that there is little to no suppression of one wavelength over another, as well as a balanced power output that is highly desirable when used as reference or signal sources.
关键词： S/S+-band,arrayed waveguide grating,Dual-wavelength,Thulium-doped fluoride fiber
更新于2025-09-12 10:27:22
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Dual-Wavelength (UV and Blue) Controlled Photopolymerization Confinement for 3D-Printing: Modeling and Analysis of Measurements
摘要： The kinetics and modeling of dual-wavelength (UV and blue) controlled photopolymerization con?nement (PC) are presented and measured data are analyzed by analytic formulas and numerical data. The UV-light initiated inhibition e?ect is strongly monomer-dependent due to di?erent C=C bond rate constants and conversion e?cacies. Without the UV-light, for a given blue-light intensity, higher initiator concentration (C10) and rate constant (k’) lead to higher conversion, as also predicted by analytic formulas, in which the total conversion rate (RT) is an increasing function of C1 and k’R, which is proportional to k’[gB1C1]0.5. However, the coupling factor B1 plays a di?erent role that higher B1 leads to higher conversion only in the transient regime; whereas higher B1 leads to lower steady-state conversion. For a ?xed initiator concentration C10, higher inhibitor concentration (C20) leads to lower conversion due to a stronger inhibition e?ect. However, same conversion ? b2C20]. Conversion of blue-only are much higher than that of UV-only and UV-blue combined, in which high C20 results a strong reduction of blue-only-conversion, such that the UV-light serves as the turn-o? (trigger) mechanism for the purpose of spatial con?rmation within the overlap area of UV and blue light. For example, UV-light controlled methacrylate conversion of a glycidyl dimethacrylate resin is formulated with a tertiary amine co-initiator, and butyl nitrite. The system is subject to a continuous exposure of a blue light, but an on-o? exposure of a UV-light. Finally, we developed a theoretical new ?nding for the criterion of a good material/candidate governed by a double ratio of light-intensity and concentration, [I20C20]/[I10C10].
关键词： additive manufacturing,kinetic model,photopolymerization,dual-wavelength,spatial con?rmation,3D printing
更新于2025-09-12 10:27:22