- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Development of highly nonlinear polarization-maintaining fibers with normal dispersion across entire transmission window
摘要： A determined polarization state of light is required in nonlinear optics applications related to ultrashort and single-cycle light pulse generation. Such short timescales require up to one full octave of the spectral width of light. A fiber-based, pulse-preserving and linearly polarized supercontinuum can meet these requirements. We report on the development—from linear simulations of the fiber structure, through fabrication of physical fibers to their versatile characterization—of polarization-maintaining, highly nonlinear photonic crystal fibers, intended for femtosecond pumping at a wavelength of 1560 nm. A full octave of linearly polarized light around this wavelength would enable the covering of amplification bandwidths of the three major fiber amplifiers, from ytterbium-doped systems up to thulium- and holmium-doped fiber amplifiers, with a coherent, linearly polarized seed signal. At the same time, an all-normal chromatic dispersion profile over an entire transmission window, and a small dispersion of nonlinearity in the developed fibers, would facilitate use of commercially available femtosecond fiber lasers as pump sources for the developed fibers.
关键词： normal dispersion,birefringence,fibers,nonlinear optics
更新于2025-09-23 15:22:29
-
Wave plate-dependent lasing regimes transitions in an all-normal-dispersion fiber laser mode-locked by nonlinear polarization rotation
摘要： We address the transitions between three different working regimes of an all-normal-dispersion pulsed fiber laser, mode-locked by nonlinear polarization rotation (NPR). In particular, we investigate numerically the dynamics and study in details the transitions induced by solely rotating the cavity wave plates. We analyze the phemomenon by putting forward a model for all-normal-dispersion NPR-moded-locked fiber laser, based on the coupled Ginzburg-Landau equations and Jones matrix. Numerical results show that depending on the values of the cavity parameters, the transitions between the dissipative soliton regime and amplifier similariton one, or the transition between the dissipative soliton regime and the splitting pulse one may be realized by simply rotating the cavity wave plates. We found that the transitions are intrinsically related to the NPR mode-locking mechanism by explicitly evaluating the polarization states across the pulse at different locations of the cavity. Our numerical results are in very good agreement with experimental results reported in the relevant literature, and provide evidence that besides gain saturation and spectral filtering, the orientations of wave plates may be exploited as a suitable degree of freedom to obtain the desired pulse regimes in all-normal-dispersion fiber lasers.
关键词： Amplifier similariton,Splitting pulse,All-normal-dispersion fiber laser,Dissipative soliton,Nonlinear polarization rotation
更新于2025-09-23 15:19:57
-
[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) - Optimisation of Dispersion Flatness in Nanostructured Core Fibres
摘要： Nanostructured optical fibres allow to obtain an arbitrary profile of refraction index in the core. These fibres are composed of several thousands of rods with diameter smaller than incident wavelength. Their optical performance is described with the Maxwell-Garnett effective medium theory. A modification of nanorods distribution or doping level in nanorods allow controlling of chromatic dispersion, polarization and modal properties of the nanostructured fibres. We study an influence of additional microrings in the core on fibre dispersion characteristics. We consider a fibre composed of pure silica nanorods and silica nanorods highly doped with Ge (concentration of GeO2 equals 20% mol). Modification of core internal structure affects electric field distribution in the fundamental mode, and consequently results in changes of its dispersion characteristics. We show that flat, all-normal dispersion characteristics (≈ 2.5 ps/nm/km) in wavelength range from 1.3 up to 2.15 μm can be achieved in the optimized structure. Moreover, within these limits, 1.5 μm to 1.9 μm range was revealed to be ultra-flat (≈ 0.2 ps/nm/km). In contrast to already reported in the literature similar fibres, proposed design is based on fused silica glasses, exhibits spectrally broader and more flat dispersion profile, it is an all-solid construction and it has the effective mode area equal 13μm2 for λ=1.55μm wavelength. Thanks to such characteristics, the fiber allows free from higher order distortions light propagation of highly confined broadband optical pulses, what might find applications in ultrafast optics, or dispersion management systems.
关键词： ultrafast optics,Maxwell-Garnett effective medium theory,chromatic dispersion,nanostructured optical fibres,all-normal dispersion
更新于2025-09-16 10:30:52
-
[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) - Buildup of Noise-Like Pulses in Ultrafast Fiber Lasers
摘要： Noise-like pulses (NLP) - the emission of sub-nanosecond incoherent pulses in ultrafast lasers - are a topic of widespread attention, owing to their fundamental and applied interest [1]. Their existence seems paradoxical, combining the high temporal localization of circulating pulses akin to mode-locking, with a fundamental instability that entails large fluctuations [2]. NLPs can be considered as incoherent dissipative solitons [3]. It is therefore of considerable interest to investigate the self-emergence of these pulses in the laser. We undertake this study experimentally using the time-stretch dispersive Fourier transform (DFT), recording the pulse spectral and temporal information in real time over successive cavity roundtrips [4]. The buildup dynamics of noise-like pulses in both anomalous and normal-dispersion fiber lasers are compared, revealing markedly different stages and timescales in the evolution process.
关键词： anomalous dispersion,normal dispersion,Noise-like pulses,ultrafast fiber lasers,dispersive Fourier transform
更新于2025-09-16 10:30:52
-
Generation of parabolic laser pulses in short fibre amplifiers
摘要： The laser pulse evolution in a normal-dispersion fibre amplifier is studied. The cases of ideal spectrum-homogeneous and transform-limited amplification are considered. It is shown that the envelope transformation of the input pulse to a parabolic form is possible not only for spectrally-flat amplification, but also for transform-limited one. In the latter case, an important parameter is the optimal amplifier length. The results demonstrate that, in the case of a sufficiently wide amplification spectrum, it is always possible to find the optimal amplifier length, after passing through which the output pulse envelope is close to a parabola.
关键词： normal dispersion,fibre amplifiers,parabolic pulses
更新于2025-09-16 10:30:52
-
Simulation of Self-focusing of Femtosecond Laser Pulses with Normal Dispersion in Air Using the Diffraction-Beam Tube Approach
摘要： Based on numerical simulation and qualitative analysis, the effect of the group velocity dispersion on the formation of light structures during self-focusing and filamentation of femtosecond Ti:sapphire laser pulses in air is studied. The main features of the filamentation have been determined at various pulse duration, initial beam radii, and peak radiation powers based on the results of numerical solutions of the nonlinear Schr?dinger equation in a Kerr-plasma dissipative dispersion medium and using the diffraction-beam tube approach. Dispersion is detected in the cases where the dispersion length is not a minimum at the scale of the process. It is shown that the relative (normalized to Rayleigh length) coordinate of the beginning of filamentation increases as the dispersion distortions of the pulse increase, and the filamentation channel length is reduced. For shorter laser pulses (tens of femtoseconds), the filamentation ceases as the laser beam radius increases. The size of the energy-replenishing diffraction-beam tube and the angular divergence of postfilamentation light channels increase for this class of pulses.
关键词： filamentation,self-focusing,femtosecond laser pulses,diffraction-beam tube,normal dispersion
更新于2025-09-12 10:27:22
-
[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) - Hot-Cavity Spectroscopy of Dark Pulse Kerr Combs in Microresonators
摘要： Kerr frequency combs are generated through cascaded four-wave mixing in high-Q microresonators [1]. These devices are pumped with a continuous-wave laser and modulational instability (MI) is responsible for the growth of the initial comb lines. Since it is easier to satisfy the MI phase matching condition in the anomalous dispersion regime, most studies on Kerr combs have focused on anomalous dispersion microresonators. However, coherent microresonator combs can also take place in the normal dispersion regime. In these combs, phase matching is attained with the aid of the mode coupling between transverse modes of the microresonator [2]. One particularly interesting comb state that operates in the normal dispersion regime is the dark pulse Kerr comb [3]. The time domain pulses of these combs arise as interlocking switching waves that connect the upper and lower homogenous steady state solutions of the bi-stability curve in the continuous-wave-driven Kerr cavity [see Fig. (a)] [3]. These combs are of high interest as most nonlinear materials suitable for fabricating microresonators display normal dispersion in the visible and near infrared ranges. Moreover, these combs provide a much higher power conversion efficiency compared to bright-soliton combs, which makes them particularly useful for telecommunications [4]. Nevertheless, the formation of dark-pulse combs and their dynamics remain largely unexplored. In this work, we provide a better physical understanding of the formation of this type of combs by measuring the system’s response as the pump laser is tuned into resonance. We discover that the formation of the dark pulse Kerr combs is associated with the appearance of an extra resonance, in striking similarity to recent observations made for bright temporal solitons in the anomalous dispersion regime [5], and explain the findings based on cross-phase modulation (XPM) induced by the two homogeneous steady state solutions of the Kerr cavity.
关键词： dark pulse Kerr comb,microresonators,normal dispersion regime,Kerr frequency combs,telecommunications
更新于2025-09-12 10:27:22
-
[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) - Power Dependent Noise Performance of fs Supercontinuum Generation in Normal Dispersion Fibers with a Long Zero-Dispersion Wavelength
摘要： One of the requirements for generating a low noise supercontinuum (SC) in a normal dispersion fiber using a femtosecond (fs) pump is to have the minimum absolute dispersion wavelength to be close to zero in order to avoid parametric Raman noise. SC generation in all-normal dispersion fibers can under certain requirements provide a highly coherent spectrum, which is of key importance to a large range of imaging and spectroscopy applications. Key requirements to avoid Raman noise and noise from polarization mode instability (PMI) is to have a sufficiently low peak power (P0), short pulse length (T0), short fiber length, and high fiber birefringence. Silica microstructured fibers (MSFs) pumped with 1550 nm fs lasers is an attractive platform to generate a low noise SC due to their technological maturity. We therefore fabricated a low-loss silica MSF (using 2 cladding sections with different hole sizes) with weak dispersion at 1500 nm and experimentally studied SC generation at low peak powers using a 1550 nm, 125 fs pump. The group velocity dispersion (β2) profile of the fiber is shown in Fig. 1(a). Since the dispersion at the pump is weak, a low P0 can be used to generate a broad SC. A further advantage of using low peak powers is the possibility of avoiding PMI. The requirement of weak dispersion at 1550 nm leads to a fiber design with a zero dispersion wavelength (ZDW) at 1.8 μm. The SC generated with up to P0 =9 kW does not cross the ZDW and has low relative intensity noise (RIN) as was demonstrated numerically and experimentally [see Fig. 1(b)]. To study the effect of higher input power, where the SC crosses into the anomalous dispersion region (ADR), we performed numerical modelling, taking into account both quantum noise and laser amplitude noise by adding 1% fluctuation in P0 with constant P0T0. At P0 =45 kW the broadening is initially from self-phase modulation and optical wave breaking in the normal dispersion region (NDR), but later the SC broadens into the ADR and develops into solitons. These solitons generate trapped dispersive waves that are very noisy and move through the low-noise spectrum in the NDR [see Fig. 1(c+d)]. Our results using the novel MSF for low-noise normal dispersion SC generation at 1550 nm, demonstrate that a long wavelength ZDW can be tolerated, as long as the peak power is sufficiently low to avoid power crossing into the ADR.
关键词： zero-dispersion wavelength,femtosecond pump,low noise,normal dispersion fibers,supercontinuum generation
更新于2025-09-11 14:15:04
-
[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) - Polarization Modulation Instability in All-Normal Dispersion Microstructured Optical Fibers with Quasi-Continuous 1064 nm Pump
摘要： Polarization modulation instability (PMI) is a form of modulation instability that can exist in weakly birefringent optical fibers. Sidebands can be generated by this effect when a polarization mode of the birefringent fiber is excited with an intense optical pump. The polarization state of the sidebands is orthogonal to the polarization of the pump signal. PMI has been observed in microstructured optical fibers (MOFs). PMI was reported in a large-air-filling fraction MOF that was pumped in the normal dispersion regime with visible light. The coherent degradation of femtosecond supercontinuum light generated in all-normal dispersion (ANDi) MOFs due to PMI was recently investigated. Here, we report the experimental observation of PMI effect in ANDi MOFs with picosecond pumping at 1064 nm.
关键词： Polarization modulation instability,microstructured optical fibers,picosecond pumping,all-normal dispersion
更新于2025-09-11 14:15:04