- 标题
- 摘要
- 关键词
- 实验方案
- 产品
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Nonlinear Fiber Optics || Optical solitons
摘要： A fascinating manifestation of the fiber nonlinearity occurs through optical solitons, formed as a result of the interplay between the dispersive and nonlinear effects. The word soliton refers to special kinds of wave packets that can propagate undistorted over long distances. Solitons have been discovered in many branches of physics. This chapter focuses on pulse propagation inside optical fibers in the regime in which both the group-velocity dispersion (GVD) and self-phase modulation (SPM) are equally important and must be considered simultaneously. It is organized as follows. Section 5.1 considers the phenomenon of modulation instability and shows that propagation of a continuous-wave (CW) beam inside optical fibers is inherently unstable and may convert the CW beam into pulse train under appropriate conditions. The inverse-scattering method is discussed in Section 5.2 together with the soliton solutions. The properties of the fundamental and higher-order solitons are also discussed in this section. Section 5.3 is devoted to other kinds of solitons, with emphasis on dark solitons. Section 5.4 considers the effects of external perturbations on solitons. Perturbations discussed include fiber losses, amplification of solitons, and noise introduced by optical amplifiers. Higher-order nonlinear effects such as self-steepening and intrapulse Raman scattering are the focus of Sections 5.5 and 5.6.
关键词： modulation instability,optical amplifiers,dark solitons,intrapulse Raman scattering,inverse-scattering method,self-steepening,group-velocity dispersion,fiber nonlinearity,self-phase modulation,fiber losses,optical solitons
更新于2025-09-12 10:27:22
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Nonlinear Fiber Optics || Introduction
摘要： This introductory chapter is intended to provide an overview of the fiber characteristics that are important for understanding the nonlinear effects discussed in later chapters. Section 1.1 provides a historical perspective on the progress in the field of fiber optics. Section 1.2 discusses various fiber properties such as optical loss, chromatic dispersion, and birefringence. Particular attention is paid to chromatic dispersion because of its importance in the study of nonlinear effects probed by using ultrashort optical pulses. Section 1.3 introduces various nonlinear effects resulting from the intensity dependence of the refractive index and stimulated inelastic scattering. Among the nonlinear effects that have been studied extensively using optical fibers as a nonlinear medium are self-phase modulation, cross-phase modulation, four-wave mixing, stimulated Raman scattering, and stimulated Brillouin scattering. Each of these effects is considered in detail in separate chapters. Section 1.4 gives an overview of how this book is organized for discussing such a wide variety of nonlinear effects in optical fibers.
关键词： fiber optics,stimulated Raman scattering,four-wave mixing,stimulated Brillouin scattering,chromatic dispersion,nonlinear effects,self-phase modulation,cross-phase modulation,birefringence
更新于2025-09-12 10:27:22
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Nonlinear Fiber Optics || Polarization effects
摘要： A major simplification was made in Section 2.3 while deriving the nonlinear Schr?dinger (NLS) equation. It consisted of assuming that the polarization state of the incident light is preserved during its propagating inside an optical fiber. This is not really the case in practice. In this chapter we focus on the polarization effects and consider the coupling between the two orthogonally polarized components of an optical field induced by the nonlinear phenomenon known as cross-phase modulation (XPM). The XPM is always accompanied with self-phase modulation (SPM) and can also occur between two optical fields of different wavelengths, a situation covered in Chapter 7.
关键词： optical fibers,nonlinear Schr?dinger equation,polarization effects,self-phase modulation,cross-phase modulation
更新于2025-09-12 10:27:22
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Nonlinear Fiber Optics || Stimulated Raman scattering
摘要： Stimulated Raman scattering (SRS) is an important nonlinear process that can turn optical fibers into broadband Raman amplifiers and tunable Raman lasers. It can also severely limit the performance of multichannel lightwave systems by transferring energy from one channel to the neighboring channels. This chapter is devoted to a thorough study of SRS phenomenon in optical fibers. Section 8.1 presents the basic theory behind SRS with emphasis on the pump power required to reach the Raman threshold. SRS under continuous-wave (CW) and quasi-CW conditions is considered in Section 8.2, where we also discuss the performance of fiber-based Raman lasers and amplifiers. Ultrafast SRS occurring for pulses of 100-ps width or less is considered in Sections 8.3 and 8.4 for normal and anomalous group-velocity dispersion (GVD), respectively. In both cases, attention is paid to the walk-off effects together with those resulting from self-phase modulation (SPM) and cross-phase modulation (XPM). Section 8.5 focuses on the polarization effects.
关键词： Raman amplifiers,optical fibers,Stimulated Raman scattering,nonlinear processes,group-velocity dispersion,Raman lasers,polarization effects,self-phase modulation,cross-phase modulation
更新于2025-09-12 10:27:22
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Nonlinear Fiber Optics || Highly nonlinear fibers
摘要： As seen in the preceding chapters of this book, three major nonlinear effects occurring inside optical fibers—self-phase modulation (SPM), cross-phase modulation (XPM), and four-wave mixing (FWM)—are governed by a single nonlinear parameter γ, defined in Eq. (2.3.30). For conventional optical fibers γ has values of ～1 W?1/km. It was realized during the 1990s that this value is too small for optical fibers to be useful as a nonlinear medium for applications requiring short lengths. To solve this problem, several new kinds of fibers with γ > 10 W?1/km were developed; they are collectively referred to as highly nonlinear fibers (HNLFs). This chapter deals with the properties of such fibers. The techniques used to measure the nonlinear parameter are described first in Section 11.1. The following four sections then focus on the four kinds of HNLFs that have been developed to enhance the nonlinear effects. In each case, dispersive properties of the fibers are also described because they play an important role whenever HNLFs are used for practical applications. It will be seen in Chapters 12 and 13 that the combination of unusual dispersive properties and a high value of γ makes HNLFs useful for a variety of novel nonlinear effects. Section 11.6 shows how the design of some HNLFs modifies the effective value of the nonlinear parameter in the case of narrow-core fibers.
关键词： four-wave mixing,highly nonlinear fibers,optical fibers,nonlinear parameter,self-phase modulation,dispersion,cross-phase modulation
更新于2025-09-12 10:27:22
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Nonlinear Fiber Optics || Self-phase modulation
摘要： The ?rst nonlinear effect that we focus on is the self-phase modulation (SPM), a phenomenon that leads to spectral broadening of optical pulses [1–9]. SPM is the temporal analog of self-focusing of CW beams occurring inside any nonlinear medium with n2 > 0. It was ?rst observed in 1967 in the context of transient self-focusing of optical pulses propagating through a CS2-?lled cell [1]. By 1970, SPM had been observed in solids and glasses by using picosecond pulses. The earliest observation of SPM in optical ?bers was made with a ?ber whose core was ?lled with CS2 liquid [7]. This work led by 1978 to a systematic study of SPM in a silica-core ?ber [9]. This chapter considers SPM as a simple example of the nonlinear effects that can occur inside optical ?bers. Section 4.1 is devoted to the case of pure SPM as it neglects the GVD effects and focuses on spectral changes induced by SPM. The combined effects of GVD and SPM are discussed in Section 4.2 with emphasis on the SPM-induced frequency chirp. Section 4.3 presents two analytic techniques and uses them to solve the NLS equation approximately. Section 4.4 extends the analysis to include the higher-order nonlinear effects such as self-steepening.
关键词： GVD,self-steepening,spectral broadening,optical pulses,frequency chirp,SPM,nonlinear effects,NLS equation,self-phase modulation
更新于2025-09-12 10:27:22
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Nonlinear Fiber Optics || Group-velocity dispersion
摘要： The preceding chapter showed how the combined effects of group-velocity dispersion (GVD) and self-phase modulation (SPM) on optical pulses propagating inside a fiber can be studied by solving a pulse-propagation equation. Before considering the general case, it is instructive to study the effects of GVD alone. This chapter considers the pulse-propagation problem by treating fibers as a linear optical medium. In Section 3.1 we discuss the conditions under which the GVD effects dominate over the nonlinear effects by introducing two length scales associated with GVD and SPM. Dispersion-induced broadening of optical pulses is considered in Section 3.2 for several specific pulse shapes, including Gaussian and 'sech' pulses. The effects of initial frequency chirping are also discussed in this section. Section 3.3 is devoted to the effects of third-order dispersion on pulse broadening. An analytic theory capable of predicting dispersive broadening for pulses of arbitrary shapes is also given in this section. We discuss in Section 3.4 how the GVD can limit the performance of optical communication systems and how the technique of dispersion management can be used to combat such limitations.
关键词： dispersion management,dispersion-induced broadening,sech pulses,Group-velocity dispersion,GVD,optical pulses,third-order dispersion,SPM,Gaussian pulses,self-phase modulation,fiber propagation,frequency chirping
更新于2025-09-12 10:27:22
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Investigating the nonlinear optical properties of poly eosin-Y phthalate solution under irradiation with low power visible CW laser light
摘要： In this work, the study of the nonlinear optical properties of poly eosin-Y phthalate solution using the diffraction ring patterns and the Z-scan methods are presented. The diffraction ring patterns were observed when a low power laser beam of wavelength of 473 nm passed through the poly eosin-Y phthalate solution. It was found that the number of rings and diameter of the outer-most ring in each pattern depends on the incident intensity of the laser beam and type of the beam wave front. The Fresnel-Kirchhoff diffraction integral theory was used to simulate the diffraction ring patterns and found good agreement with experimental results. Both diffraction ring patterns and closed aperture Z-scan techniques were used to calculate the nonlinear refractive index, while open aperture Z-scan was used to calculate the nonlinear absorption coefficient of the poly eosin-Y phthalate solution. The possibility of using the sample as an optical limiter is tested.
关键词： Nonlinear refractive index,Self-phase modulation,Optical limiting,Diffraction ring pattern,Z-scan technique,Thermal nonlinearity
更新于2025-09-12 10:27:22
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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) - Label-Free Multiphoton Microscopy in Human Tissue Enabled by an Er:Fiber-Laser Based Tunable Source
摘要： Multiphoton microscopy (MPM) is an important bio-imaging tool. Different modalities can serve as a contrast agent, such as second-/third-harmonic generation (SHG/THG) and two-/three-photon excitation fluorescence (2PEF/3PEF). Ultrafast lasers with flexible wavelength tunability are crucial for driving MPM bio-imaging, and the conventional solution relies on ultrafast Ti:sapphire lasers plus an optical parametric oscillator/amplifier. Recently, we have demonstrated that ultrafast fiber lasers are a potential solution to implementing compact, robust, and wavelength tunable femtosecond sources for driving MPM. To realize wavelength tunability we employ self-phase modulation (SPM) in optical fibers to broaden a narrowband input spectrum of Yb-/Er-doped fiber lasers (YDFLs/EDFLs) up to >400-nm wide with well-isolated spectral lobes; filtering the leftmost/rightmost lobes leads to nearly transform-limited pulses [1–6]. Such a SPM-enabled spectral selection (SESS) allows us to obtain wavelength widely tunable femtosecond pulses for MPM [2,5,6]. In this submission, we representatively demonstrate label-free harmonic generation microscopy (HGM) in human skin and brain tissues. Figure 1(a) depicts a scanning microscope driven by an EDFL-based SESS source. The EDFL operates at 31-MHz repetition rate and generates 290-fs pulses centered at 1550 nm. The narrowband EDFL [blue curve in Fig. 1(a)] is coupled into 9-cm optical fiber (10-μm mode-field diameter and -10 fs2/mm group-velocity dispersion at 1550 nm). The output spectrum is shown as the red curve in Fig. 1(b) under 85-nJ coupled pulse energy. We use optical filters to select the leftmost spectral lobe peaking at 1250 nm, which leads to 11.7-nJ, 47-fs pulses. Then we employ these pulses to drive a scanning microscope and conduct HGM in human skin and brain tissues. Figure 1(c) shows the dermal papilla at the junction of epidermis and upper dermis in human skin. Basal cells are visualized by THG (cyan hot) due to optical inhomogeneity at the interface (e.g., cell membrane); SHG (red hot) originates from the non-centrosymmetric structure of collagen fibers. In Fig. 1(d), neural network and brain vasculature in human brain tissue can be visualized by THG and SHG, respectively [Fig. 1(d)]. THG contrast inside the vasculature shows also red blood cells. In conclusion, we report on MPM deep-tissue imaging enabled by an EDFL-based SESS source. It is noteworthy that besides HGM excited by 1250-nm femtosecond pulses demonstrated here, the SESS source also supports 1300-/1700-nm illumination for 3PEF of green/red fluorescent protein (GFP/RFP) [7,8]. Such a fiber-based solution can be applied to many important applications, such as histopathology, morphology, and neuroscience.
关键词： ultrafast fiber lasers,Multiphoton microscopy,self-phase modulation,bio-imaging,harmonic generation microscopy
更新于2025-09-12 10:27:22
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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) - Pure-Quartic Solitons from a Dispersion Managed Fibre Laser
摘要： In optical fibre resonators, the balance between anomalous quadratic dispersion and self-phase modulation (SPM) gives rise to optical solitons [1]. These pulses have made a significant impact in a wide range of photonic applications including telecommunications and lasers. However, these conventional soliton-based lasers can only deliver modest pulse energy due to the appearance of Kelly sidebands arising from periodical perturbations in the cavity [2] and a fixed energy-width scaling. Recently, a new class of soliton, arising from the balance of anomalous quartic dispersion and SPM, called pure-quartic soliton (PQS), were observed in a dispersion engineered photonic crystal waveguide [3]. PQSs have huge potential for generating ultrashort pulses with high energy due to their generalized area theorem (E ~ 1/(cid:507)(cid:306)3), however they are yet to be observed in fibre platforms [4]. Here we report on the generation of PQS pulses from a passively mode-locked fibre laser incorporating a programmable spectral pulse-shaper that induces a dominant quartic net cavity dispersion. We find that the spectral profile of the generated pulses are in good agreement with the spectral shape of PQSs [3]. We also observe spectral sidebands in this quartic-dispersion cavity, in analogy to the conventional soliton case [2], and find that their positions are in excellent agreement with analytic predictions. These are strong evidences of a novel type of mode-locked laser, the PQS laser, which has the potential to reach dramatically higher energies at short pulse durations than its conventional soliton counterpart [3,4].
关键词： dispersion managed fibre laser,pure-quartic solitons,optical solitons,photonic applications,self-phase modulation
更新于2025-09-11 14:15:04