All-optical Applications Research Articles

Exploring nonlinear optical properties of RbPbI3 nanorods using SSPM technique: Implications for all-optical switching applications

Nowadays, nanomaterials' nonlinear optical (NLO) properties are a fascinating topic for developing a novel all-optical switching application. Spatial self-phase modulation (SSPM) is an important technique to determine the laser-induced coherent light-matter interaction to determine the NLO properties of nanomaterials. This study successfully synthesized RbPbI3 nanorods (NRs) via a low-cost, less complicated chemical route with all the basic characterizations to confirm its structural and compositional analysis. For the first time, we conducted a comprehensive analysis of the nonlinear refractive index (n2) and third-order susceptibility (χ(3)) for RbPbI3 NRs dissolved in two different solvents, namely N-Methyl-2-pyrrolidone (NMP) and 2-propanol, utilizing the SSPM technique. Our investigation revealed significant nonlinear optical (NLO) responses with n2 = 6.19 × 10−5 cm2 W−1 and χmonolaer(3) = 2.38 × 10−8 esu for RbPbI3. We elucidated the factors contributing to this pronounced NLO behaviour, including variations in parameters such as solvent type, viscosity, wavelength, and cuvette length. Additionally, we successfully demonstrated optical information transfer through an all-optical switching application. This research sheds light on the NLO properties of Perovskite materials and holds promise for the development of advanced all-optical device applications.

Facile Exfoliation of Few-Layer Sn-Based Nanosheets for Self-Powered Photo-Electrochemical and All-Optical Modulation Applications.

Few-layer tin (Sn)-based nanosheets (NSs) with a thickness of ≈2.5nm are successfully prepared using a modified liquid phase exfoliation (LPE) method. Here the first exploration of photo-electrochemical (PEC) and nonlinear properties of Sn NSs is presented. The results demonstrate that the PEC properties are tunable under different experimental conditions. Additionally, Sn NSs are shown to exhibit a unique self-powered PEC performance, maintaining a good long-term stability for up to 1 month. Using electron spin resonance, active species, such as hydroxyl radicals (·OH), superoxide radicals (·O2 -), and holes (h+), are detected during operations, providing a deeper understanding of the working mechanism. Furthermore, measurements of nonlinear response reveal that Sn NSs can be effective for all-optical modulation, as it enables the realization of all-optical switching through excitation spatial cross-phase modulation (SXPM). These findings present new research insights and potential applications of Sn NSs in optoelectronics.

Nonlinear generation of vector beams by using a compact nonlinear fork grating

Vectorial beams have attracted great interest due to their broad applications in optical micromanipulation, optical imaging, optical micromachining, and optical communication. Nonlinear frequency conversion is an effective technique to expand the frequency range of the vectorial beams. However, the scheme of existing methods to generate vector beams of the second harmonic (SH) lacks compactness in the experiment. Here, we introduce a new way to realize the generation of vector beams of SH by using a nonlinear fork grating to solve such a problem. We examine the properties of generated SH vector beams by using Stokes parameters, which agree well with theoretical predictions. Then we demonstrate that linearly polarized vector beams with arbitrary topological charge can be achieved by adjusting the optical axis direction of the half-wave plate (HWP). Finally, we measure the nonlinear conversion efficiency of such a method. The proposed method provides a new way to generate vector beams of SH by using a microstructure of nonlinear crystal, which may also be applied in other nonlinear processes and promote all-optical waveband applications of such vector beams.

Tunable Enhanced Second-Harmonic Generation in InP-InAsP Quantum Well Nanomembranes.

Second-harmonic generation (SHG) offers a convenient approach for infrared-to-visible light conversion in tunable nanoscale light sources and optical communication. Semiconductor nanostructures offer rich possibilities to tailor their nonlinear optical properties. In this study, strong second-harmonic generation in InP nanomembranes with InAsP quantum well (QW) is demonstrated. Compared with bulk InP, up to 100 times enhancement of SHG is achieved in the short-wave infrared range. This enhancement is shown to be predominantly induced by the resonance-enhanced absorption and quantum confinement of fundamental wavelengths in the InAsP QW. The thin nanomembrane structure will also provide nanocavity enhancement for second-harmonic wavelengths. The enhanced SHG peak wavelengths can also be tuned by changing the QW composition. These findings provide an effective strategy for enhancing and manipulating the second-harmonic generation in semiconductor quantum-confined nanostructures for on-chip all-optical applications.

Plasmonic structure assisted all-optical tunable fiber laser

In this paper, we proposed and demonstrated a tunable fiber laser using all-optical plasmonic modulation, where the localized surface plasmon resonance effect of gold nanobipyramids (GNBPs) and polarization maintaining thin-cladding photonic crystal fiber were utilized to realize tunable output wavelength controlled by the 980 nm pump light. The laser achieves a tunability of 2.21 nm in C-band, with a side mode suppression ratio of 27 dB and the peak intensity can also be tuned continuously. The proposed tunable laser shows an average power fluctuation of less than 1 dB and the output wavelength and the power intensity both exhibit high stability. Therefore, the proposed plasmonic structure assisted all-optical tunable laser has advantages such as compact structure, good reproducibility, continuous tuning, and simple operation, which indicates great potential in future all-optical applications.

Experimental study of four-wave mixing based on a quantum dot semiconductor optical amplifier

The article is devoted to the study of four-wave mixing (FWM) in a semiconductor optical amplifier with quantum dots (QD-SOA). Experimental measurements of FWM signals are characterized in nonlinear media of GaAs-based QD-SOA with gain in the 1,550 nm region. Theoretical part of nonlinear effect of FWM is studied and important all-optical communication applications are listed. Experimental studies of a four-wave system are described and an analysis of FWM signals is given for various input powers of pump signals and injection currents. The devices are compared in terms of such parameters as conversion efficiency and signal-to-noise ratio. The results of the study made it possible to reveal the possibility of the effect of FWM signals on useful signals in channels with spectral division multiplexing wavelength division multiplexing (WDM) in the downstream and upstream in a semiconductor optical amplifier. Based on the experimental results, it was concluded that FWM does not affect adjacent channels of WDM signals and does not generate additional optical noise when scaling the WDM gigabit passive optical network (GPON) up to 60 km using semiconductor optical amplifiers (SOAs).

Evolution and dynamics of spatial self-phase modulation in pyrromethene 567 for all-optical photonic diode applications

Spatial self-phase modulation has emerged as a novel and ubiquitous nonlinear optical effect, revealing potential application in all-optical devices for signal processing. The work investigates the evolution and dynamics of SSPM patterns in pyrromethene 567 (PM 567). A temperature-dependent refractive index gradient which induces a phase shift in the incident beam is responsible for the formation of spatial self-phase modulation. The non-linear response of PM 567 in different solvents and concentrations is investigated and tabulated. The effect of wavefront curvature, path length, and mechanical chopper on the formation of the SSPM patterns was studied. To our knowledge, an optical-diode-based unidirectional generation of spatial self-phase modulation in dyes has been reported for the first time. Simply cascading PM 567 dissolved in DMSO and Methanol having distinct nonlinear optical responses, an all-optical diode for unidirectional light propagation based on spatial self-phase modulation in PM 567 was achieved. The work reveals the potential application of PM 567 for achieving spatial asymmetry in light propagation based on SSPM in photonic devices for all-optical signal processing.

Temporal manipulation of period-2 polarization domain wall solitons in a nonlinear fiber Kerr resonator

We report on the experimental demonstration of temporal manipulations of dissipative polarization domain wall solitons in a Kerr nonlinear resonator operated in a period-doubled configuration. Our experiments are performed in a coherently driven normally dispersive fiber ring cavity, in which polarization domains emerge in virtue of a spontaneous symmetry breaking phenomenon. The addition of a lumped birefringent defect into the cavity forces their polarization components to swap on a two-round-trip cycle, thus protecting them from the deleterious impact of the system’s asymmetries. We exploit these symbiotic dynamics in proof-of-concept buffering experiments, in which these dissipative structures are addressed individually and temporally manipulated through phase-encoded perturbations imprinted onto the driving beam. Our results provide new insights into the practical exploitation of spontaneous symmetry breaking mechanisms and the use of two-component dissipative structures for all-optical data storage applications.

Third-Order Optical Nonlinearities of 2D Materials at Telecommunications Wavelengths

All-optical signal processing based on nonlinear optical devices is promising for ultrafast information processing in optical communication systems. Recent advances in two-dimensional (2D) layered materials with unique structures and distinctive properties have opened up new avenues for nonlinear optics and the fabrication of related devices with high performance. This paper reviews the recent advances in research on third-order optical nonlinearities of 2D materials, focusing on all-optical processing applications in the optical telecommunications band near 1550 nm. First, we provide an overview of the material properties of different 2D materials. Next, we review different methods for characterizing the third-order optical nonlinearities of 2D materials, including the Z-scan technique, third-harmonic generation (THG) measurement, and hybrid device characterization, together with a summary of the measured n2 values in the telecommunications band. Finally, the current challenges and future perspectives are discussed.

Spectral pulsation dynamics of soliton molecules in ultrafast fiber lasers based on pump intensity modulation

<sec>This study employs real-time Fourier transform spectroscopy to investigate the pulsation dynamics of soliton molecules in a mode-locked erbium-doped fiber laser, by modulating pump intensity. By controlling the driving voltage of the pump source, we systematically observe and characterize the influence of external modulation signals on the amplitude, period, pulsation frequency, and the relative phase evolution among the pulsating soliton molecules in their spectra.</sec><sec>The results demonstrate that under specific conditions of pump intensity modulation, the pulsation period of soliton molecule spectra can be precisely regulated by the pump modulation frequency. At the same time, the amplitude of soliton molecule pulsations and the evolution of relative phase among the solitons are intricately tied to the pump modulation frequency. At lower modulation frequencies, such as 1 kHz, the relative phase among the pulses in the soliton molecule exhibits a sliding-type dynamics as a function of propagation time.</sec><sec>As the modulation frequency gradually increases to 5 kHz, a scenario emerges where three soliton molecules are generated. Notably, both the soliton spacing and relative phase undergo synchronous adjustments influenced by the pump modulation. With the modulation frequency further increasing, say, to 20 kHz, the relative phase evolution among the pulses within the soliton molecule gradually descends into chaos. This observation suggests the plausible existence of an inherent resonant frequency associated with pulsating soliton molecules, which has direct implications for their stability.</sec><sec>The findings of this research are of significance in advancing our comprehension of soliton molecule generation and enhancing their stability. In addition, they provide valuable insights into the broader domain of all-optical manipulation and applications of soliton molecules, and their application in pulse encoding in mode-locked laser systems.</sec>

Strong non-linear optical response of Sb2Se3 nanorods in a liquid suspension based on spatial self-phase modulation and their all-optical photonic device applications.

The field of nonlinear optics is constantly expanding and gaining new impetus through the discovery of fresh nonlinear materials. Herein, for the first time, we have performed spatial self-phase modulation (SSPM) experiments with an emerging anisotropic Sb2Se3 layered material in a liquid suspension for an all-optical diode and all-optical switching application. The third-order broadband nonlinear optical susceptibility (χ(3)single layer ∼ 10-9 esu) and nonlinear refractive index (n2 ∼ 10-6 cm2 W-1) of Sb2Se3 have been determined using a 671 nm laser beam. This result could be unambiguously explained by the anisotropic hole mobility of Sb2Se3. The linear relationship of χ(3) and carrier mobility emphasizes the establishment of nonlocal hole coherence, the origin of the diffraction pattern. Consequently, the time evolution of diffraction rings follows the 'Wind-Chime' model. A novel photonic diode based on Sb2Se3/SnS2 has been demonstrated using the nonreciprocal propagation of light. The self-phase modulation (SPM) technique uses laser lights of different wavelengths and intensities to demonstrate the all-optical logic gates, particularly OR logic gates. The exploration of nonlinear optical phenomena in Sb2Se3 opens up a new realm for optical information processing and communication. We strongly believe that this result will help to underpin the area of optical nonlinearities among its various applications.

Spectral pulsation dynamics of soliton molecules in ultrafast fiber lasers based on pump intensity modulation

This study employs real-time Fourier transform spectroscopy to investigate the pulsation dynamics of soliton molecules in a mode-locked erbium-doped fiber laser, utilizing pump intensity modulation. By manipulating the driving voltage of the pump source, we systematically observe and characterize the impact of external modulation signals on the amplitude, period, pulsation frequency, and the relative phase evolution among the pulsating soliton molecules within their spectra.The results demonstrate that, under specific conditions of pump intensity modulation, the pulsation period of soliton molecule spectra can be precisely regulated by the pump modulation frequency. Concurrently, the amplitude of soliton molecule pulsations and the evolution of relative phase among the solitons are intricately tied to the pump modulation frequency. At lower modulation frequencies, such as 1 kHz, the relative phase among the pulses within the soliton molecule exhibits a sliding-type dynamics as a function of propagation time.As the modulation frequency gradually increases, e.g., to 5 kHz, a scenario emerges where three soliton molecules are generated. Notably, both the soliton spacing and relative phase undergo synchronous adjustments influenced by the pump modulation. With further escalation of the modulation frequency, such as to 20 kHz, the relative phase evolution among the pulses within the soliton molecule gradually descends into chaos. This observation suggests the plausible existence of an inherent resonant frequency associated with pulsating soliton molecules, which has direct implications for their stability.The findings of this research hold significant relevance for advancing our comprehension of soliton molecule generation and enhancing their stability. Furthermore, they offer valuable insights into the broader domain of all-optical manipulation and applications of soliton molecules, as well as their utilization in pulse encoding within mode-locked laser systems.

Graphene oxide enhanced phase change tolerance of Ge2Sb2Se4Te1 for all-optical multilevel non-volatile photonics memory

The low optical loss of G e 2 S b 2 S e 4 T e 1 (GSST) makes it a potential functional material for all-optical multilevel photonics memory devices that can operate in the optical telecommunication wavelength band. However, the same characteristic also restricted the tolerance of GSST phase change conditions using 1550 nm as an excitation light source. This work reports on the enhancement of GSST phase change condition tolerance using a graphene oxide (GO) intermediate layer on a polymer waveguide platform. The hybrid waveguide exhibits an insertion loss of around 1 dB and a maximum readout contrast of 25% between amorphous and crystalline states, with a step increase in readout contrast of around 5% per step. This work serves as a proof of concept for the implementation of a GSST–GO hybrid structure as an optical functional material in all-optical photonics memory applications.

Fully controllable multichannel waveguides induced by counterpropagating Bessel beams

We theoretically analyze the waveguiding structures photo-induced by two incoherent counter-propagating Bessel beams (BBs) in a biased photorefractive crystal. We demonstrate that the cross-coupling of two BBs enables adressable channels and tunability of the forming guiding structures. The truncation parameter of the BBs, their Bessel orders and the misalignment between the two beams are all key parameters for tailoring the characteristics of the photo-induced waveguides such as the number of outputs, the output intensity levels and the distance between each output channel. Accordingly, we optimized the different parameters for designing not only a fully tunable Y-coupler but also optical splitters with up to five outputs and even more complex star couplers for all-optical interconnect applications. Finally, we report on the stability behavior of the photo-induced platform. The stability threshold depends on the nonlinearity parameter beyond which the beams display time-periodic, quasi-periodic and turbulent dynamics where spatially localized instabilities can be observed. All these results suggest more opportunities for fully controllable complex waveguiding structures and new all-optical solutions for active components in optical telecommunication and innovative ways of performing optical computing based on spatiotemporal chaos.

Real-Time Image Processing Toolbox for All-Optical Closed-Loop Control of Neuronal Activities

The development of in vivo imaging and optogenetic tools makes it possible to control neural circuit activities in an all-optical, closed-loop manner, but such applications are limited by the lack of software for online analysis of neuronal imaging data. We developed an analysis software ORCA (Online Real-time activity and offline Cross-session Analysis), which performs image registration, neuron segmentation, and activity extraction at over 100 frames per second, fast enough to support real-time detection and readout of neural activity. Our active neuron detection algorithm is purely statistical, achieving a much higher speed than previous methods. We demonstrated closed-loop control of neurons that were identified on the fly, without prior recording or image processing. ORCA also includes a cross-session alignment module that efficiently tracks neurons across multiple sessions. In summary, ORCA is a powerful toolbox for fast imaging data analysis and provides a solution for all-optical closed-loop control of neuronal activity.

Graphdiyne-Coated Microfiber All-Optical Temporal Modulator Based on Saturable Absorption

A high-speed all-optical modulator is a key device in next-generation communication systems. Due to easy fabrication and an effective modulation effect, two-dimensional (2D) material–microfiber structure all-optical modulators have aroused much attention. Graphdiyne (GDY) is an excellent nonlinear optical material and is expected to be utilized in all-optical modulators. In this work, we demonstrate a GDY-coated all-optical temporal modulator according to its saturable absorption. Under the pump pulse light of 1,064 nm, the fabricated modulator successfully modulates the continuous-wave (CW) light of 1,550 nm to the waveform of pump light with a pulse width of 4 ns and a repetition rate of 5 kHz. Our results show that GDY could be used in high-speed all-optical modulators and pave a way for the research of GDY in all-optical information processing applications.

Visible optical nonlinearity of vanadium dioxide dispersions.

Vanadium dioxide (VO2), a correlated oxide compound, is one of the functional materials extensively studied in solid state physics due to its attractive physical properties. However, the nonlinear optical response of VO2 and related all-optical applications have been paid less attention. Here, the nonlinear refractive index (n 2) and third-order nonlinear susceptibility (χ (3)) of VO2 dispersions have been acquired to be 3.06 × 10-6 cm2 W-1 and 1.68 × 10-4 esu at a wavelength of 671 nm, and 5.17 × 10-6 cm2 W-1 and 2.83 × 10-4 esu at a wavelength of 532 nm via the spatial self-phase modulation (SSPM) and spatial cross-phase modulation (SXPM) effects in the visible regime, respectively. Based on the excellent nonlinear optical properties of VO2 dispersions, the proof-of-principle functions such as optical logic or-gates, all-optical switches, and inter-channel information transfer are implemented in the visible wavelength. The experimental results on the response time of VO2 to light indicate that the formation of diffraction rings is mainly an electronically coherent third-order nonlinear optical process. The experimental results show that the VO2 dispersions exhibit an excellent nonlinear optical response and may lay the foundation for the application of VO2-based all-optical devices.

Nonlinear Absorption and Refraction of Highly Monodisperse and Luminescent ZnTe Quantum Dots and Their Self-Assembled Nanostructures: Implications for Optoelectronic Devices.

Zinc telluride (ZnTe) quantum dots (QDs) were synthesized by a unique supersaturation-controlled aqueous route. For a given pH, increasing the degree of initial supersaturation led to a decrease in the average diameter (davg) of the QDs and increased monodispersity. Three samples of ZnTe QDs having average sizes of 0.8, 1.7, and 2.2 nm were synthesized (hence named ZnTe_0.8, ZnTe_1.7, and ZnTe_2.2). Nonlinear absorption (NLA) and nonlinear refraction (NLR) of these colloidal ZnTe QDs of different sizes were investigated by the Z-scan technique using a continuous He–Ne laser (632.8 nm, 15 mW). Isotropic assembly of ZnTe_2.2 leads to the formation of nanoballs (hence named ZnTe_NB). The NLA profile of smaller QDs, ZnTe_1.7 and ZnTe_0.8, was found to follow a three-photon absorption (3PA) model, while relatively bigger QDs, ZnTe_2.2, followed a two-photon absorption (2PA) model. On moving from ZnTe_0.8 to ZnTe_1.7, the three-photon absorption coefficient (γ) decreases by 26% (3.00 × 10–4 → 2.21 × 10–4 cm3/MW2). The two-photon absorption coefficient (β) for ZnTe_2.2 is 0.3 cm/MW. For a 63% decrease in average diameter (2.2 → 0.8 nm), the refractive index (n2) increases by 45% (2.48 × 10–2 → 3.6 × 10–2 cm2/MW). Overall, the NLR coefficient shows a decreasing trend with size. Upon isotropic self-assembly, ZnTe_NB, there is a significant increase in the NLR coefficient by 40% (2.48 × 10–2 → 3.48 × 10–2 cm2/MW) and a simultaneous decrease in the NLA coefficient by 45% (0.3 → 0.166 cm/MW). The figure of merit was also determined for all of the samples, and it was found that ZnTe_2.2 and ZnTe_0.8 were best suited for all-optical device applications. Further, the self-assembled nanostructures are promising for making optical waveguides for supercontinuum generation (SCG).

Investigation of the intensity dependent transition from saturable absorption to reverse saturable absorption and ultrafast negative refraction in terthiophene-based chalcone derivatives

Two novel chalcone derivatives C12 & C13 are designed and synthesized. Terthiophene group is employed to provide the planar π-conjugated system in these molecules while the molecular planarity is tuned by the different substitutions at the terminal group. The ultrafast optical nonlinearities are investigated via transient absorption spectrum and Z-scan. It is generally assumed that a large planar π-system and strong intramolecular charge transfer can enhance the optical nonlinearities in organic nonlinear optical materials. However, the molecule with larger planar molecular structure displayed weaker nonlinear absorption due to the competition between saturable absorption and reverse saturable absorption. With DFT calculation, the structure-property relation and the enhancement of π-conjugated system on nonlinear absorption and refraction are discussed. The investigations and discussions may provide a different perspective of the nonlinear absorption and refraction in these organic molecules and the results also suggest that these chalcone derivatives are potential nonlinear refraction materials for all-optical applications. • Two terthiophene-based chalcone derivatives are designed and synthesized. • The transition from SA to RSA and the negative refraction are investigated. • Both compounds are low-loss nonlinear optical refraction materials.

Ultra-large capacity all-optical crossover technology and application analysis

Ultra-large capacity all-optical crossover technology and application analysis