Showing papers in "Laser Physics in 2014"
TL;DR: In this paper, mode instability in a 500 W terbium-doped fiber laser is experimentally examined by changing the pumping wavelength, spectral bandwidth of signal light, active fiber temperature and coiling radius.
Abstract: In this paper mode instability in a 500 W ytterbium-doped fiber laser is experimentally examined by changing the pumping wavelength, spectral bandwidth of signal light, active fiber temperature and coiling radius. The magnitude of power transfer from the fundamental mode to the higher order mode due to mode instability is measured as a criterion for its incident. The experiments show that the coiling radius of the first few tens of centimeters of the active fiber plays a significant role in controlling mode instability, and shifting the pumping wavelength from 976 to 973 nm can mitigate mode instability.
68 citations
TL;DR: In this article, a phase-sensitive optical time-domain reflectometer (OTDR) utilizing dual-pulse phase modulations of the probe signal is presented and experimentally demonstrated.
Abstract: A novel configuration of a phase-sensitive optical time-domain reflectometer (OTDR) utilizing dual-pulse phase modulations of the probe signal is presented and experimentally demonstrated. The proposed modulation method enables one to perform the demodulation and reconstruction of an external perturbation signal which impacts the fiber using the phase diversity technique. The proposed phase-sensitive OTDR has some advantages in comparison with conventional solutions, which are discussed. The feasibility of a double pulse OTDR with phase modulation is demonstrated and theoretically proved.
66 citations
TL;DR: In this paper, the influence of target material on the ablation behavior of femtosecond laser pulses was investigated, where three different materials, representing the spectrum of electrical conductivities, were selected: a dielectric (fused silica), a semiconductor (crystalline silicon), and a metal (gold).
Abstract: The influence of target material on the ablation behavior of femtosecond laser pulses was investigated. Three different materials, representing the spectrum of electrical conductivities, were selected: a dielectric (fused silica), a semiconductor (crystalline silicon), and a metal (gold). Ablation was performed in ambient air using a Ti:sapphire laser, which emits radiation at a wavelength of 785 nm and a pulse width of 130 fs. Surface morphology and ablation depth were evaluated using optical and scanning electron microscopy. Significant changes in surface morphology were observed with variation of the fluence and number of laser pulses. In all materials, two different ablation regimes were distinguished depending on the fluence. Ablation threshold, which was determined from the relationship between crater diameter squared and the logarithm of laser energy, was found to depend on the number of laser pulses incident on the same spot (i.e. incubation phenomenon).
64 citations
TL;DR: In this article, femtosecond pulse generation in an Er-doped fiber laser is reported, where the laser is passively mode-locked by an antimony telluride (Sb2Te3) topological insulator (TI) saturable absorber (SA) placed on a side-polished fiber.
Abstract: In this paper, femtosecond pulse generation in an Er-doped fiber laser is reported. The laser is passively mode-locked by an antimony telluride (Sb2Te3) topological insulator (TI) saturable absorber (SA) placed on a side-polished fiber. The Sb2Te3/chitosan suspension used to prepare the SA was obtained via liquid phase exfoliation from bulk Sb2Te3.Ultra-short 449 fs soliton pulses were generated due to the interaction between the evanescent field propagated in the fiber cladding and the Sb2Te3 layers. The optical spectrum is centered at 1556 nm with 6 nm of full-width at half maximum bandwidth. The presented method benefits from a much better repeatability compared to mechanical exfoliation.
61 citations
TL;DR: In this paper, a 1.06-m dissipative-soliton fiber laser incorporating a saturable absorber based on a bulk-structured Bi2Te3 topological insulator (TI) was demonstrated.
Abstract: We experimentally demonstrate a 1.06-?m dissipative-soliton fiber laser incorporating a saturable absorber based on a bulk-structured Bi2Te3 topological insulator (TI). The saturable absorber, which had a bulk-structured Bi2Te3 TI film deposited on a side-polished fiber, provided the dual functions of nonlinear saturable absorption and spectral comb filtering, which are essential for the generation of dissipative solitons. The saturable absorption function was obtained through a micrometer-thick bulk-structured Bi2Te3 TI film, whereas the spectral comb filtering function was through the asymmetric side-polished fiber structure, on top of which a different refractive index film was deposited. The ~17??m-thick Bi2Te3 TI film was prepared using a simple mechanical exfoliation method. The fabrication of the targeted micrometer-thick bulk-structured film was straightforward without needing special care, compared to nanosheet-based film fabrication. Stable dissipative-soliton pulses with a composite temporal shape were readily obtained by incorporating the prepared saturable absorber into an ytterbium-doped fiber ring cavity with all-normal dispersion. The temporal width of the output pulses was measured to be ~230?ps.
51 citations
TL;DR: In this article, the interaction between a Λ-type three-level atom and two quantized electromagnetic fields which are simultaneously injected in a bichromatic cavity surrounded by a Kerr medium in the presence of field-field interaction and detuning parameters is investigated.
Abstract: In this paper, we study the interaction between a Λ-type three-level atom and two quantized electromagnetic fields which are simultaneously injected in a bichromatic cavity surrounded by a Kerr medium in the presence of field–field interaction (parametric down conversion) and detuning parameters. By applying a canonical transformation, the introduced model is reduced to a well-known form of the generalized Jaynes–Cummings model. Under particular initial conditions which may be prepared for the atom and the field, the time evolution of the state vector of the entire system is analytically evaluated. Then, the dynamics of the atom is studied through the evolution of the atomic population inversion. In addition, two different measures of entanglement between the tripartite system (three entities make the system: two field modes and one atom), i.e., von Neumann and linear entropy are investigated. Also, two kinds of entropic uncertainty relations, from which entropy squeezing can be obtained, are discussed. In each case, the influences of the detuning parameters and Kerr medium on the above nonclassicality features are analyzed in detail via numerical results. It is illustrated that the amount of the above-mentioned physical phenomena can be tuned by choosing the evolved parameters, appropriately.
50 citations
TL;DR: In this paper, the transformation of paraxial and non-paraxial Bessel beams in a crystal of Iceland spar is considered theoretically and an optical system is designed for investigating the intensity distribution after passage through the crystal.
Abstract: The transformation of paraxial and nonparaxial Bessel beams in a crystal of Iceland spar is considered theoretically. Calculation formulae for matching the thickness of the crystal and the parameters of the incident beam required for complete conversion of a circularly polarized zero-order Bessel beam into a second-order vortex beam are obtained. An optical system was designed for investigating the intensity distribution after passage through the crystal. Experimental and theoretical results are in good agreement.
45 citations
TL;DR: In this paper, the authors demonstrate a highly stable mode-locked fiber laser based on single wall carbon nanotubes, which is achieved by the evanescent field interaction of the propagating light with a single wall carbide saturable absorber in a microfiber.
Abstract: We demonstrate a highly stable mode locked fiber laser based on single wall carbon nanotubes. The mode locking is achieved by the evanescent field interaction of the propagating light with a single wall carbon nanotube saturable absorber in a microfiber. The pulse width is 66 fs, which, to the best of our knowledge, is the shortest pulse achieved in a carbon nanotube mode locked fiber laser. The maximum average output power is 26 mW, which is about 20 times larger than that of a typical carbon nanotube mode locked fiber laser. The center of the wavelength is 1555 nm, with 54 nm spectral width. The repetition rate is 146 MHz. To investigate the laser's stability, the output pulses are monitored for 120 h and there is no significant degradation of the laser spectral width or shape.
43 citations
TL;DR: In this paper, the authors analyzed the impact of gyration on the mode polarization in plasmonic waveguides containing dielectrics with natural optical activity, or gyration induced by magnetization in the polar configuration or the longitudinal configuration.
Abstract: We analyze the gyration impact on the mode polarization in plasmonic waveguides containing dielectrics with natural optical activity, or gyration induced by magnetization in the polar configuration or the longitudinal configuration. It has been found that the gyration mostly affects the mode polarization that acquires additional optical field components proportional to the gyration coefficient, whereas the mode dispersion remains almost unchanged. Moreover, if the gyration coefficient is rather large, then the mode loses its localization. The polarization transformation can be two orders of magnitude stronger for structures with a thin metal film than that for the solitary interface. The polarization transformation of the plasmonic modes was demonstrated experimentally via measuring optical transmittance through a layered magnetoplasmonic structure. The resonance in the transmittance spectrum corresponding to the excitation of modes of the polarization orthogonal to that of incident light was observed. The polarization transformation is enhanced if the TM and TE modes are excited simultaneously. The described effect can be applied in sensors, plasmonic circuitry, and plasmonic-based light modulators.
42 citations
TL;DR: In this paper, an alternative technique for the preparation of ytterbium (Yb)-doped silica fibers and their characteristics compared to the conventional modified chemical vapor deposition (MCVD) process in combination with solution doping and powder sinter technology (REPUSIL) was reported.
Abstract: In this paper we report on an alternative technique for the preparation of ytterbium (Yb)-doped silica fibers and their characteristics compared to the conventional modified chemical vapor deposition (MCVD) process in combination with solution doping and powder sinter technology (REPUSIL) In the case of the technique applied here, the active core diameter in the preform can be significantly increased via the deposition of Yb and the most important codopant, aluminum (Al), in the gas phase through the high-temperature evaporation of the Yb chelate compound and Al chloride in the MCVD process The prepared preform shows a homogenous distribution of the refractive index and dopant concentration The background loss of the drawn fiber was measured to be 25 dB km−1 at 1200 nm Efficient lasing up to 200 W, showing a slope efficiency of about 80%, was demonstrated, which is comparable to fibers made via MCVD/solution doping and the REPUSIL technique
37 citations
TL;DR: In this article, the interaction between two two-level atoms and a two-mode field in an optical cavity enclosed by a medium with Kerr nonlinearity in the presence of a detuning parameter and Stark effect was studied.
Abstract: An entangled state, as an essential tool in quantum information processing, may be generated through the interaction between light and matter in cavity quantum electrodynamics. In this paper, we study the interaction between two two-level atoms and a two-mode field in an optical cavity enclosed by a medium with Kerr nonlinearity in the presence of a detuning parameter and Stark effect. It is assumed that the atom–field coupling and third-order susceptibility of the Kerr medium depend on the intensity of the light. In order to investigate the dynamics of the introduced system, we obtain the exact analytical form of the state vector of the considered atom–field system under initial conditions which may be prepared for the atoms (in a coherent superposition of their ground and upper states) and the fields (in a standard coherent state). Then, in order to evaluate the degree of entanglement between the subsystems, we investigate the dynamics of the entanglement by employing the entanglement of formation. Finally, we analyze in detail the influences of the Stark shift, the deformed Kerr medium, the intensity-dependent coupling, and also the detuning parameter on the behavior of this measure for different subsystems. The numerical results show that the amount of entanglement between the different subsystems can be controlled by choosing the evolved parameters appropriately.
TL;DR: In this paper, the authors used a Gaussian function-based deconvolution method to analyze the Raman spectrum of the lipid-keratin peak and the least square method was applied for analyzing the petrolatum penetration profile.
Abstract: Human skin pre-treated with petrolatum was analyzed in vivo using confocal Raman microscopy in order to determine the penetration depth of the oil into the skin. The broad Raman peak (2820–3030 cm−1) measured in vivo on human skin in the high wavenumber region exhibits two prominent main Raman peaks at 2880 cm−1 and 2935 cm−1 that originated from cutaneous lipids and keratin and two main peak shoulders at 2850 cm−1 and 2980 cm−1 that originated from lipids and keratin, respectively. Topical application of petrolatum oil onto the skin gives rise to an increase of the intensity of the broad lipid–keratin Raman peak (2820–3030 cm−1). Herewith, not only the intensity of the lipid part but also of the keratin part is increased, making the normalization to keratin and the determination of the petrolatum penetration profile erroneous. To solve this problem, the Gaussian-function-based deconvolution method is introduced in analyzing the Raman spectrum of the lipid–keratin peak and the least square method is applied for analyzing the petrolatum penetration profile. Results obtained in vivo show that the petrolatum oil does not penetrate deeper than 10 µm into intact human skin.
TL;DR: In this paper, a double-clad erbium-ytterbium (EB) ring laser with nonlinear polarization evolution was used for noise-like pulse generation in a km-long fiber ring laser.
Abstract: In this paper, we study noise-like pulse generation in a km-long fibre ring laser including a double-clad erbium?ytterbium fibre and passively mode-locked through nonlinear polarization evolution. Although single noise-like pulsing is only observed at moderate pump power, pulse energies as high as 120?nJ are reached in this regime. For higher pump power, the pulse splits into several noise-like pulses, which then rearrange into a stable and periodic pulse train. Harmonic mode locking from the 2nd to the 48th orders is readily obtained. At pump powers close to the damage threshold of the setup, much denser noise-like pulse trains are demonstrated, reaching harmonic orders beyond 1200 and repetition frequencies in excess of a quarter of a GHz. The mechanisms leading to noise-like pulse breaking and stable high-order harmonic mode locking are discussed.
TL;DR: In this article, photoinduced optical effects, third-order nonlinearity, and optical power limiting of Mn doped and Mn al codoped ZnO thin films were examined by x-ray diffraction studies.
Abstract: We report the photoinduced optical effects, third-order nonlinearity, and optical power limiting of Mn doped and Mn‐Al codoped ZnO thin films. The thin films were prepared by the spray pyrolysis technique. The structural properties of the deposited films were examined by x-ray diffraction studies. Z -scan measurements were conducted to evaluate the nonlinear optical parameters using a He‐Ne laser operating in continuous wave mode at 633 nm wavelength. The present study reveals that the introduction of Mn and Mn‐Al into ZnO leads to significant changes in the third-order nonlinear susceptibility. Photoinduced second-harmonic generation studies also reveal the dependence of the nonlinear optical properties on the Mn content. Switching over from saturable absorption to reverse saturable absorption was observed. The optical limiting studies show that the films possess a lower limiting threshold and clamping level, which is essential for use in eye and sensor protection applications. Hence, the Mn doped and Mn‐Al codoped ZnO thin films investigated here emerge as promising candidates for future optoelectronic and photonic device applications such as optical power limiters.
TL;DR: In this article, the effects of continuous wave He-Ne laser irradiation (632nm, 5mWmm-2, 2min d−1) on the physiological indexes of wheat seedlings exposed to enhanced UV-B radiation (10kJ m−2 d− 1) at the early growth stages were explored.
Abstract: The level of ultraviolet-B (UV-B) radiation on the Earth’s surface has increased due to depletion of the ozone layer. Here, we explored the effects of continuous wave He-Ne laser irradiation (632 nm, 5 mW mm–2, 2 min d–1) on the physiological indexes of wheat seedlings exposed to enhanced UV-B radiation (10 KJ m–2 d–1) at the early growth stages. Wheat seedlings were irradiated with enhanced UV-B, He-Ne laser treatment or a combination of the two. Enhanced UV-B radiation had deleterious effects on wheat photosynthesis parameters including photosystem II (chlorophyll content, Hill reaction, chlorophyll fluorescence parameters, electron transport rate (ETR), and yield), the thylakoid (optical absorption ability, cyclic photophosphorylation, Mg2+-ATPase, and Ca2+-ATPase) and some enzymes in the dark reaction (phosphoenolpyruvate carboxylase (PEPC), carbonic anhydrase (CA), malic dehydrogenase (MDH), and chlorophyllase). These parameters were improved in UV-B-exposed wheat treated with He-Ne laser irradiation; the parameters were near control levels and the enzyme activities increased, suggesting that He-Ne laser treatment partially alleviates the injury caused by enhanced UV-B irradiation. Furthermore, the use of He-Ne laser alone had a favourable effect on seedling photosynthesis compared with the control. Therefore, He-Ne laser irradiation can enhance the adaptation capacity of crops.
TL;DR: The recent results of a 20 GHz bandwidth high performance spectrum monitoring system with the additional capability of broadband direction finding demonstrates the potential for spatial-spectral systems to be the practical choice for solving demanding signal processing problems in the near future.
Abstract: Many storage and processing systems based on spectral holeburning have been proposed that access the broad bandwidth and high dynamic range of spatial-spectral materials, but only recently have practical systems been developed that exceed the performance and functional capabilities of electronic devices. This paper reviews the history of the proposed applications of spectral holeburning and spatial-spectral materials, from frequency domain optical memory to microwave photonic signal processing systems. The recent results of a 20 GHz bandwidth high performance spectrum monitoring system with the additional capability of broadband direction finding demonstrates the potential for spatial-spectral systems to be the practical choice for solving demanding signal processing problems in the near future.
TL;DR: In this article, a method is introduced for quantitatively analyzing photon echo decay measurements to characterize excitation-induced decoherence resulting from the phenomenon of instantaneous spectral diffusion, and detailed analysis is presented that allows fundamental material properties to be extracted that predict and describe excitationinduced decocherence for a broad range of measurements, applications and experimental conditions.
Abstract: A method is introduced for quantitatively analyzing photon echo decay measurements to characterize excitation-induced decoherence resulting from the phenomenon of instantaneous spectral diffusion. Detailed analysis is presented that allows fundamental material properties to be extracted that predict and describe excitation-induced decoherence for a broad range of measurements, applications and experimental conditions. Motivated by the need for a method that enables systematic studies of ultra-low decoherence systems and direct comparison of properties between optical materials, this approach employs simple techniques and analytical expressions that avoid the need for difficult to measure and often unknown material parameters or numerical simulations. This measurement and analysis approach is demonstrated for the 3 H6 to 3 H4 optical transition of three thulium-doped crystals, Tm 3+ :YAG, Tm 3+ :LiNbO3 and Tm 3+ :YGG, that are currently employed in quantum information and classical signal processing demonstrations where minimizing decoherence is essential to achieve high efficiencies and large signal bandwidths. These new results reveal more than two orders of magnitude variation in sensitivity to excitation-induced decoherence among the materials studied and establish that the Tm 3+ :YGG system offers the longest optical coherence lifetimes and the lowest levels of excitation-induced decoherence yet observed for any known thulium-doped material.
TL;DR: An erbium-doped fiber laser based on random distributed feedback through Rayleigh scattering in a long-distance (5-30 km) singlemode fiber (SMF) is demonstrated for the first time in this article.
Abstract: An erbium-doped fiber laser based on random distributed feedback through Rayleigh scattering in a long-distance (5–30 km) single-mode fiber (SMF) is demonstrated for the first time. Under the pump of a 1480 nm laser diode, typical random laser radiation is achieved with an obvious threshold behavior as a function of pump power. Thanks to the fiber Bragg grating (FBG)-based half-opened cavity design and the efficient gain from the pumped erbium-doped fiber, a low threshold power of 10 mW is achieved, which is approximately two orders lower in magnitude than that of previously reported conventional random fiber lasers amplified through distributed Raman effects. Dual-wavelength lasing operation is also achieved by using two FBGs with different reflection wavelengths to collaborate with the distributed Rayleigh output mirror.
TL;DR: In this paper, an alternative scheme for constructing a shortcut to implement the quantum state transfer between two three-level atoms founded on the invariant-based inverse engineering in a cavity quantum electronic dynamics (QED) system was proposed.
Abstract: We propose an alternative scheme for constructing a shortcut to implement the quantum state transfer between two three-level atoms founded on the invariant-based inverse engineering in a cavity quantum electronic dynamics (QED) system. Quantum information can be quickly transferred between atoms by taking advantage of the cavity field as a medium. Through our design of the time-dependent laser pulse and atom–cavity coupling, we send atoms through the cavity within a short time interval, which involves the two processes of the invariant dynamics between each atom and the cavity field simultaneously. We redesign a reasonable Gaussian-type wave form in the atom–cavity coupling for a realistic experimental operation. Numerical simulation shows that the target state can be quickly populated with a high fidelity which is robust against both the parameter fluctuations and the dissipation.
TL;DR: In this article, the authors demonstrate photon echo operation at such a low signal intensity without any preparation step, which allows them to work with mere two-level atoms, and show that very strong control fields can be compatible with extremely weak signals, making ROSE consistent with quantum memory requirements.
Abstract: To store and retrieve signals at the single photon level, various photon echo schemes have resorted to complex preparation steps involving ancillary shelving states in multi-level atoms. For the first time, we experimentally demonstrate photon echo operation at such a low signal intensity without any preparation step, which allows us to work with mere two-level atoms. This simplified approach relies on the so-coined ‘revival of silenced echo’ (ROSE) scheme. Low noise conditions are obtained by returning the atoms to the ground state before the echo emission. In the present paper we manage ROSE in photon counting conditions, showing that very strong control fields can be compatible with extremely weak signals, making ROSE consistent with quantum memory requirements.
TL;DR: In this article, high-axis oriented wurtzite structured ZnO thin films were deposited on silicon substrates using pulsed laser deposition (PLD) by ablating a target in different atmospheres, including vacuum, argon and oxygen in the deposition chamber.
Abstract: Highly c-axis oriented wurtzite structured ZnO thin films were deposited on silicon substrates using pulsed laser deposition (PLD) by ablating a ZnO target in different atmospheres, including vacuum, argon and oxygen in the deposition chamber. The stress in the films was shown to vary from −3.83 to −0.03 GPa as a function of the chamber atmosphere. The minimum compressive stress (−0.03 GPa) was observed for the oxygen atmosphere. X-ray photoelectron spectroscopy data indicated that the O1s peak consists of three components designated as O1 (due to ZnO), O2 (due to defects) and O3 (due to adsorbed species). A small defect level emission was obtained in the luminescence spectra of the ZnO film deposited in the oxygen atmosphere, while strong ultraviolet (UV) emission was observed for the ZnO films deposited in the vacuum and argon atmosphere. These PLD grown ZnO thin films have the potential to be used as sources of UV radiation in light emitting devices.
TL;DR: In this article, the authors used autofluorescence spectroscopy to estimate the concentration of fluorophores in brain tumor tissue and used principal component analysis-linear discriminant analysis (PCA-LDA) for tissue classification.
Abstract: Fluorescence spectroscopy is an emerging tool used to differentiate normal and malignant tissue based on the emission spectral profile from endogenous fluorophores. The goal of this study is to estimate the concentration of fluorophores using autofluorescence spectroscopy and try to utilize its diagnostic potential on samples of clinical importance. Brain tumor tissues from patients who received craniotomy for the removal of astrocytoma, glioma, meningioma and schwannoma were utilized in this study. Fluorescence emissions of the formalin fixed samples were recorded at excitation wavelengths of 320 and 410 nm. The emission characteristics of fluorophores such as collagen, nicotinamide adenine dinucleotide (NADH), flavin adenine dinucleotide (FAD), phospholipids and porphyrins of tumor tissue and adjacent normal tissue were elicited. Exact tissue classification was carried out using the spectral intensity ratio (SIR) and multivariate principal component analysis–linear discriminant analysis (PCA–LDA). The diagnostic algorithm based on PCA–LDA provided better classification efficiency than SIR. Moreover, the spectral data based on an excitation wavelength of 410 nm are found to be more efficient in the classification than 320 nm excitation, using PCA–LDA. Better efficacy of PCA–LDA in tissue classification was further confirmed by the receiver operator characteristic (ROC) curve method. The results of this study establish the feasibility of using fluorescence spectroscopy based real time tools for the discrimination of brain tumors from the adjacent normal tissue during craniotomies, which at present faces a huge challenge.
TL;DR: In this article, the first demonstration of a Ho:YAG (yttrium aluminum garnet) solid-state laser passively Q-switched via a graphene saturable absorber was reported.
Abstract: We report the first demonstration of a Ho:YAG (yttrium aluminum garnet) solid-state laser passively Q-switched via a graphene saturable absorber. The Ho:YAG laser was in-band pumped by a continuous wave diode-pumped Tm:YLF (yttrium lithium fluoride) laser. Double-layer graphene grown by chemical vapor deposition and transferred onto a thin quartz plate was fabricated as the saturable absorber. We observed basically stable Q-switched laser pulses at the center wavelength of 2096.5 nm with the shortest pulse width of 632 ns, a repetition rate of 43 kHz, and the single-pulse energy of 13.3 μJ. Our results illustrate that graphene can be used well as a saturable absorber in a Ho-doped solid-state laser at 2 μm wavelength.
TL;DR: In this paper, a 320m long passively mode-locked erbium-doped figure-eight fiber laser was used for multiple noise-like pulse generation in the normal net dispersion regime.
Abstract: In this work we study multiple noise-like pulse generation in a 320?m long passively mode-locked erbium-doped figure-eight fibre laser in the normal net dispersion regime. The nonlinear optical loop mirror (NOLM) that is used as a mode locker operates through polarization asymmetry, which allows us to control its switching power by birefringence adjustments at the NOLM input, using a half-wave retarder (HWR). Over some range of the HWR orientation, a single noise-like pulse is observed in the cavity. Its peak power is adjustable as it remains clamped to the variable switching power, and its duration varies inversely between ?5 and ?22?ps. Beyond the HWR position, corresponding to the longest duration, the pulse splits into several noise-like pulses. These multiple pulses usually present a walkoff, however they can be synchronized through slight birefringence adjustments, although they are not evenly spaced in time. Up to 12 simultaneous noise-like pulses were observed experimentally, with a duration of ?2?ns. Multiple pulsing and synchronization of the pulses are interpreted in terms of mechanisms of interaction between pulses. Multiple pulsing appears to be indirectly related to the peak power limiting effect of the NOLM.
TL;DR: In this article, a combined Akhmediev breather and Kuznetsov-Ma soliton solution with nonautonomous characteristics for certain functional relations is presented, and different types of controllable excitation behaviors such as limitation excitation, maintenance and postponement are demonstrated.
Abstract: We study the (2 + 1)-dimensional coupled nonlinear Schrodinger equation with variable coefficients in a graded-index waveguide, and present a combined Akhmediev breather and Kuznetsov–Ma soliton solution with nonautonomous characteristics for certain functional relations. From this solution, by modulating the relation between the maximum effective propagation distance Zmax and the periodic locations Zm based on the maximum amplitude of soliton solution, different types of controllable excitation behaviors such as limitation excitation, maintenance and postponement are demonstrated.
TL;DR: In this paper, the effects of Doppler broadening and Kerr nonlinearity on fast light propagation in a spinning medium were investigated and a significant increase was observed in the rotation of the polarization states of the light and images.
Abstract: We propose a four-level experimental N-type atomic configuration to observe the propagation of a light pulse in a spinning dispersive medium. In this model a fast propagating light pulse is observed in which the polarization states of the light and their transmitted images are rotated in the opposite direction to the spinning medium. We investigate the effects of Doppler broadening and Kerr nonlinearity on fast light propagation in a spinning medium. Doppler broadening and Kerr nonlinearity strongly influence the rotation of the polarization states of the light and images of fast light in a spinning medium. A pulse of group velocity −c/2000.5 ms−1 is enhanced to −c/80000 ms−1 due to the the Kerr effect and a significant increase is observed in the rotation of the polarization states of the light and images. At a specific parameter, a 25% fraction change is observed due to the Kerr effect. These results provide different rotation states for image coding.
TL;DR: In this article, the spectral and nonlinear optical properties of a colloidal solution of platinum nanoparticles (Pt NPs) in water are investigated by laser ablation of a Pt metallic target in distilled water using a 1064 nm Nd:YAG laser.
Abstract: In this paper, the spectral and nonlinear optical properties of a colloidal solution of platinum nanoparticles (Pt NPs) in water are presented The Pt NPs were prepared by laser ablation of a Pt metallic target in distilled water using a 1064 nm high frequency Nd:YAG laser The intensity-dependent nonlinear optical absorption and nonlinear refraction behaviors of the sample exposed to the 532 nm nanosecond laser pulses were investigated by applying the Z-scan technique The saturated nonlinear absorption coefficient 54 × 10−7 cm W−1 was obtained in a saturation intensity of 18 × 107 W cm−2 The saturable absorption response of the Pt NPs was switched to the reverse saturable absorption in the higher laser intensities The nonlinear refractive index that has a negative value was increased from −35 × 10−13 cm2 W−1 up to −15 × 10−13 cm2 W−1 by increasing the laser intensity
TL;DR: In this article, the generation of ions during laser ablation of a metallic target (copper) with ≈50 fs Ti:Sa laser pulses of moderate intensity (≈1014 W cm−2) is studied by simultaneous fast-imaging and ion-probe techniques.
Abstract: The generation of ions during laser ablation of a metallic target (copper) with ≈50 fs Ti:Sa laser pulses of moderate intensity (≈1014 W cm−2) is studied by simultaneous fast-imaging and ion-probe techniques. The spatiotemporal distribution of excited ions and neutrals in the laser-produced plasma plume is analyzed by exploiting appropriate band-pass filters in the imaging set-up, while the ion flux angular distribution is characterized by angle-resolved ion probe measurements. An interesting feature of our results is the generation of a fast ion population separated from the neutral component of the atomic plasma plume and characterized by sub-keV kinetic energies, which is interpreted in the frame of a simple model of ambipolar diffusion.
TL;DR: In this paper, the photonic density of states (PDS) of the eigen polarizations (EPs) was calculated using exact analytical expressions for the reflection and transmission matrices for the finite thickness cholesteric liquid crystal (CLC) layer.
Abstract: Using the exact analytical expressions for the reflection and transmission matrices for the finite thickness cholesteric liquid crystal (CLC) layer, we calculated its photonic density of states (PDS) of the eigen polarizations (EPs). We investigated the influence of absorption and gain, as well as the CLC cell thickness and CLC local dielectric anisotropy on PDS. We presented the full picture of distribution of total field in the CLC layer and outside it for two EPs. The possibility of connections between the PDS and the density of the light energy accumulated in the medium was investigated, and it was shown that these characteristics had analogous spectra and, besides, the influences of the problem parameters on these characteristics were also analogous. We showed that there existed a critical value of the parameter characterizing the gain beyond which the lasing mode was quenched and the feedback vanished. We showed that in the presence of gain there existed a critical value of numbers of pitches in the CLC layer beyond which the lasing mode was again quenched and the feedback vanished, too. It is shown that the subject system can work as a low-threshold laser or a multi-position trigger.
TL;DR: In this paper, the laser fabrication of nanostructured materials including the nano-and microclusters for control of electrical, optical and other properties of obtained structures is discussed.
Abstract: The main goal of our work is the laser fabrication of nanostructured materials including the nano- and microclusters for control of electrical, optical and other properties of obtained structures. First, we took an opportunity to select nanoparticles in various sizes and weights and also in topology distribution for some materials (carbon, Ni, PbTe, etc). Second, for a deposited extended array of nanoparticles we used a method of laser-induced nanoparticle fabrication in colloid and deposition metal (and/or oxide) nanoparticles from colloidal systems (LDPCS) to obtain the multilayered nanostructures with controlled topology, including the fractal cluster structures (for Ni, Pb Te et al). Electrophysical properties are analyzed for such nanocluster systems as well. A brief analogy of the obtained nanocluster structures with a quantum correlated state evidence is carried out.