- 标题
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- 实验方案
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Mega-Hertz repetition rate broadband nano-second pulses from an actively mode-locked Yb-fiber laser
摘要： This work demonstrates an actively mode-locked all-normal dispersion Yb-fiber ring laser, delivering pulses of few nano-seconds (ns) to sub-ns duration at a 4 MHz repetition rate. Employing a filterless cavity architecture and different, long-length intra-cavity nonlinear fibers; a broadband output spectrum in the 1060–1140 nm wavelength region was obtained. With an increasing pump power, the pulse width reduced along with the appearence of new pulses, resulting into a muti-pulsing output. For a fixed pump power, the number of pulses and the amount of spectral broadening varied for different non-linear fibers. In the multi-pulsing state, the pulses were found to be located seperately in both time and wavelength, where Raman stokes corresponding to individual pulses could also be observed. The maximum output pulse energy achieved in a single pulse state was around 8.7 nJ, which increased to 14.5 nJ in a multi-pulse state. To the best of the authors’ knowledge, this is the first demonstration of a filterless active mode-locked fiber ring laser producing high-repetition rate broadband nano-second pulses in single and multi-pulse states at 1 μm.
关键词： broadband laser,fiber laser,actively mode-locked laser,nano-second pulses
更新于2025-11-28 14:23:57
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[IEEE 2018 IEEE Sensors - New Delhi (2018.10.28-2018.10.31)] 2018 IEEE SENSORS - Highly Sensitive Refractometer Using a Fiber Bragg Grating Fabricated by Femtosecond Laser
摘要： A highly localized fiber Bragg grating is inscribed using point-by-point femtosecond laser direct writing technique. By monitoring the location of the cut off wavelength, we demonstrate that the FBG has a highly-linear sensitivity for refractive index (RI) measurement. By monitoring the “peak-to- dip” intensity change near the cut-off wavelength, an ultra-high refractive index sensitivity of 2924.3dB/RIU and a RI resolution of 3.4×10-7 are achieved. As different surrounding refractive index corresponds to different location of the cut off wavelength, this FBG based refractometer can measure RI with wide range measurement range together with high sensitivity.
关键词： Femtosecond laser,Fiber Bragg grating,Refractive index sensors
更新于2025-11-28 14:23:57
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[IEEE IGARSS 2019 - 2019 IEEE International Geoscience and Remote Sensing Symposium - Yokohama, Japan (2019.7.28-2019.8.2)] IGARSS 2019 - 2019 IEEE International Geoscience and Remote Sensing Symposium - Accurate Ground Positioning Obtained From 3d Data Matching Between Airborne and Terrestrial Data for Ground Validation of Satellite Laser
摘要： We present a phase mask inscription technique with two beam interferometry using a lateral nonhomogeneous beam splitter to create gratings with nonhomogeneous periods, the so-called chirped fiber Bragg gratings. Inscription experiments with deep ultraviolet excimer and femtosecond laser sources reveal how this inscription method depends on the coherence properties of the inscription laser. Nonhomogeneous beam splitters are shown to provide a method to generate chirped fiber Bragg gratings with great wavelength versatility, even with the ultraviolet femtosecond laser.
关键词： two-beam interferometry,Femtosecond laser,fiber Bragg gratings,optical fiber filters
更新于2025-09-19 17:13:59
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[IEEE 2019 21st International Conference on Transparent Optical Networks (ICTON) - Angers, France (2019.7.9-2019.7.13)] 2019 21st International Conference on Transparent Optical Networks (ICTON) - Polymer Fiber Lasers
摘要： Polymers doped with laser dyes are promising materials for solid state dye lasers. The development of dye doped polymer optical fibers is presented. Furthermore, experimental results from polymer bulk and fiber lasers based on these optical materials are reported.
关键词： rhodamine B,fiber laser,fiber amplifier,polymer fiber,laser dye
更新于2025-09-16 10:30:52
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[IEEE 2019 IEEE International Conference on Electrical Engineering and Photonics (EExPolytech) - St. Petersburg, Russia (2019.10.17-2019.10.18)] 2019 IEEE International Conference on Electrical Engineering and Photonics (EExPolytech) - Laser Frequency Noise Measurement by Forming an Interference Signal with Subcarrier Frequency
摘要： The paper presents a method for measuring laser frequency noise spectrum with the use of unbalanced fiber-optic interferometer and auxiliary phase modulation, forming a subcarrier signal at the interferometer output. The main features of the proposed method are analyzed. The paper also presents the results of experimental validation of the proposed method by measuring laser frequency noise of a high-coherent optical fiber laser.
关键词： laser frequency noise spectrum,laser frequency noise,coherent laser,fiber-optic interferometer
更新于2025-09-16 10:30:52
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Are we cutting ourselves short? Laser lithotripsy performance based on differences in fiber-tip preparation
摘要： Objectives: To better understand the impact of laser fiber-tip configuration on lithotripsy performance, we undertook an in vitro study comparing three fiber-tip configurations: 1) new (single-use), 2) cleaved (re-usable) and 3) coated (cut with scissors). Methods: Lithotripsy was performed using a Ho:YAG laser utilizing fragmentation (1Jx10Hz) and dusting (0.5Jx20Hz) settings. BegoStones were fragmented with a laser fiber advancing at a speed of 1 mm/s (220 seconds of activation). Three fiber-tip configurations were tested: new single-use standard (242 ?m core) and cleaved (272 ?m core), compared to the same fiber-tip coated/cut flush with scissors, respectively. Study outcome was difference in stone mass before and after each experiment. Power output was measured using a power meter. Results: Fragmentation for new or cleaved fibers was greater than the coated/cut flush fiber-tip (p<0.05). For 1Jx10Hz and 0.5Jx20Hz settings, fragmentation was 59% and 75% higher with new fiber-tip compared to the coated/cut flush fiber-tip, respectively. For 1Jx10Hz and 0.5Jx20Hz settings, fragmentation was 51% and 45% higher with cleaved fiber-tip compared to the coated/cut flush fiber-tip, respectively. Power output at the end of laser activation was higher for new and cleaved fiber-tips. Conclusion: New and cleaved laser fibers demonstrated superior lithotripsy performance compared to fibers that were coated/cut flush with scissors. Cutting single-use laser fibers risks damaging the fiber-tip which can disperse the energy and reduce lithotripsy efficiency.
关键词： Lithotripsy,Equipment,Holmium Laser,Dusting,Laser Fiber
更新于2025-09-16 10:30:52
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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) - Realtime Coherent cw THz System: Phase Modulation without Phase Modulator
摘要： In optoelectronic continuous wave (cw) THz spectroscopy phase measurement is very beneficial, to improve SNR and/or to obtain depth information. Often, the required phase modulation limits the acquisition speed and increases the complexity of existing cw THz systems. Commonly, optical free space delay lines, fibre stretchers [1] or electro optical modulators [2] are used for phase modulation. In this paper we demonstrate that a simple optical fiber delay in combination with a fast sweeping laser source can be used for ultrafast fast phase modulation. With this technique we demonstrate a fully fibre-coupled cw THz spectrometer with 58 Hz update rate covering a bandwidth of 2.5 THz. To the best of our knowledge this is the fastest coherent cw THz system demonstrated so far. This makes cw THz systems competitive to time-domain approaches in terms of acquisition speed and simplifies the system architecture significantly. Therefore, it paves the way for compact, broadband and cost-effective THz systems.
关键词： continuous wave,phase modulation,fast sweeping laser,fiber delay,THz spectroscopy
更新于2025-09-16 10:30:52
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Experimental Demonstration of Single Sideband Modulation Utilizing Monolithic Integrated Injection Locked DFB Laser
摘要： Single sideband (SSB) modulation based on a monolithic integrated optically injection-locked (MOIL) DFB laser is demonstrated experimentally. To our knowledge, this is the first time to realize SSB modulation utilizing a MOIL DFB laser. Tunable SSB signals with large lower-to-upper sideband power ratios are achieved by changing the bias currents of the MOIL DFB laser. The largest lower-to-upper sideband power ratio is measured to be 24.4 dB, which is very useful for improving the transmission performance of a radio-over-fiber link. Due to the generated SSB modulation, the fiber transmission response is flattened significantly and a signal of 25 GHz is transmitted through 85-km fiber without being affected by the fiber chromatic dispersion. 20 MSymbol/s 32-QAM signals with subcarriers of 21 GHz, 23 GHz and 25 GHz are also transmitted by the proposed SSB modulation link, and both the error vector magnitude (EVM) and the bit error rate (BER) of the link are improved distinctly. The proposed method can effectively suppress the fiber chromatic dispersion.
关键词： optical photonic integration,Single sideband modulation (SSB),injection-locked DFB laser,fiber chromatic dispersion
更新于2025-09-16 10:30:52
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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) - Numerical and Experimental Study on the IR Femtosecond Laser and Phase Mask-Based Grating Inscription in Photonic Crystal Fibers
摘要： Femtosecond pulse laser sources enable the fabrication of fiber Bragg gratings (FBGs) in non-photosensitive fibers, allow for through coating grating inscription when working at infrared (IR) wavelengths and can provide for high temperature stable gratings. Target applications for such gratings include, but are not limited to, optical communications, fiber lasers and fiber sensing. When dealing with such grating inscription method in photonic crystal fibers (PCF) however, the presence of air holes in the fiber cladding impedes the delivery of the femtosecond laser pulse energy to the fiber core, which in its turn significantly affects the index change through non-linear absorption processes in the fiber core [1]. Our research focuses on this issue in view of understanding how the grating writing laser pulses interact with the PCF’s holey structure and of enabling more efficient femtosecond laser-based inscription of FBGs in PCFs. Here we report on the inscription of FBGs in a hexagonal lattice PCF using a femtosecond pulse laser operating at 1030 nm with a phase mask and a short focal length cylindrical lens (f=10 mm) that focuses light to the fiber core [2]. We first looked into the influence of the alignment on laser beam focusing in the cross-section of the PCF by comparing the focusing characteristics to those in standard step-index single mode fiber. As a figure of merit, we used the transverse coupling efficiency (TCE), which is defined as the ratio of the integrated core field intensities simulated (using Lumerical FDTD Solutions?) in the presence and absence of holey cladding. Fig. 1b shows how the TCE changes as the fiber is translated along the X and Y axes in the cross-sectional plane. X=0 and Y=0 corresponds to focused to the center of the core, and negative Y indicates translation of the fiber away from the lens (see Fig. 1a). For a step-index fiber we observe a typically elongated region in which we find optimal coupling with TCE=1 (no air holes) for a beam waist of 2.34 μm and a depth of focus of 15.7 μm. Fig. 1c shows an alignment map for a hexagonal lattice PCF (with structure shown in the inset of Fig. 1d), when light is incident along the ΓK axis of the hexagon. We can identify three distinct regions with a TCE around 0.6. Those appear when the fiber is shifted by around 15 μm and 30 μm further from the lens. This offset indicates that optimal coupling of the grating writing beam to the PCF core requires focusing to the edge of the holey cladding or closer to the silica cladding region of the fiber, rather than to the core center. Fig. 1 a) Fiber translational axes and translation dependence of the transverse coupling efficiency (TCE) for b) step-index fiber and c) PCF. d) Spectra of the IR femtosecond pulse inscribed FBG in the PCF (SEM image in the inset). We then inscribed FBGs in the above mentioned hexagonal lattice PCF with a commercial Yb:KGW ultrafast regenerative amplifier system Pharos 6W (Light Conversion) at 1030 nm and 190 fs duration pulses at a repetition rate of 100 Hz. We used high accuracy alignment stages to find the best coupling position by monitoring the luminescence (around 420 nm) from the Ge-doped core. The reflection and transmission spectra of the inscribed FBG are shown in Fig. 1c. We achieved an almost 4 dB strong FBG in around 4 seconds using a laser power of 450 mW. To the best of our knowledge it is the first time that the difference between regular step-index fibers and PCFs in best focusing conditions for IR femtosecond laser-based FBG writing is studied and that such a FBG is realized in a PCF using a 1030 nm source and a phase mask technique with a short focal length cylindrical lens.
关键词： phase mask,photonic crystal fibers,Femtosecond pulse laser,fiber Bragg gratings,transverse coupling efficiency
更新于2025-09-12 10:27:22
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Stress-induced refractive index changes in laser fibers and preforms
摘要： Refractive index profile of the core is a key design parameter in fiber lasers and amplifiers. During manufacturing, the initial information of the index profile is obtained from the preform, while ultimately the performance is defined by the index profile of the fiber. Depending on stresses and diffusion, the two profiles may be different. It is possible to predict more accurately the laser fiber refractive index when we apply a stress-induced index change model to the measured preform index profile data. The improved capability to predict the fiber index from preform increases the confidence in achieving the designed index profile in fiber, which enables faster process feedback and higher fiber yields.
关键词： laser fiber,tension,optical fiber,modelling,thermal stress,preform,Refractive index change,DND,stress
更新于2025-09-11 14:15:04