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We investigate the soliton stability in multimode fiber with an optically induced temporal potential (TP). The soliton experiences a cross-phase-modulation-induced TP when co-propagating with a pump pulse. While without the TP both the spatiotemporal soliton and continuous wave are stable, the TP makes only the spatiotemporal soliton stationary and stable.

Optical nanotapers fabricated by tapering optical fibers have attracted considerable interest as an ultimate platform for high-efficiency light-matter interactions. While previously demonstrated applications relied exclusively on the low-loss transmission of only the fundamental mode, the implementation of multimode tapers that adiabatically transmit several modes has remained very challenging, hindering their use in various emerging applications in multimode nonlinear optics and quantum optics. Here, we report the realization of multimode submicron tapers that permit the simultaneous adiabatic transmission of multiple higher-order modes including the LP02 mode, through introducing deep wet-etching of conventional fiber before fiber tapering. Furthermore, as a critical application, we demonstrate fundamental-to-fundamental all-fiber third-harmonic generation with high conversion efficiencies. Our work paves the way for ultrahigh-efficiency multimode nonlinear and quantum optics, facilitating nonclassical light generation in the multimode regime, multimode soliton interactions and photonic quantum gates, and manipulation of the evanescent-field-induced optical trapping potentials of atoms and nanoparticles. Low-loss multimode optical nanofibers could provide a platform for studying and technologically exploiting nonlinear light-matter interactions. Here, adiabatic transport of multiple modes and highly efficient fundamental-to-fundamental third harmonic generation is demonstrated in a submicron silica fiber.

Vector beams, structured optical beams with nonuniform polarization distributions over the cross-section, have been recently found to be more beneficial than the scalar beams to many applications r...

Silica nanofibers fabricated by tapering optical fibers have attracted considerable interest as an ultimate platform for high-efficiency light-matter interactions. While previously demonstrated applications relied exclusively on the low-loss transmission of only the fundamental mode, the implementation of multimode tapers that adiabatically transmit several modes has remained very challenging, hindering their use in various emerging applications in multimode nonlinear optics and quantum optics. Here, we report the first realization of multimode submicron tapers that permit the simultaneous adiabatic transmission of multiple higher-order modes including the LP02 mode, through introducing deep wet-etching of conventional fiber before fiber tapering. Furthermore, as a critical application, we demonstrate 'fundamental-to-fundamental' all-fiber third-harmonic generation with high conversion efficiencies. Our work paves the way for ultrahigh-efficiency multimode nonlinear and quantum optics, facilitating nonclassical light generation in the multimode regime, multimode soliton interactions and photonic quantum gates, and manipulation of the evanescent-field-induced optical trapping potentials of atoms and nanoparticles., 22 pages, 6 figures

We report the generation of a supramolecular structure of 3.2-ns-spaced multiple cavity solitons via the interplay between the Kerr effect and Brillouin scattering in a fiber Kerr resonator. Pulsed pumping and continuous-wave pumping are compared.

We successfully demonstrate a widely all-parameter-tunable ultra-narrow-linewidth nearly transform-limited mode-locked erbium-doped fiber laser. Pulse-width-adjustable (100–150 ps) low-repetition-rate (~2 MHz) dissipative solitons are generated over the pulse-breakup-free wavelength tuning range of 34.3 nm (1529.3–1563.6 nm). © 2020 The Author(s)

We demonstrate the manipulation of quasi-continuous-wave background in a mode-locked fiber laser using optoacoustically excited acoustic impulses. The properties of the resulting intensity modulations of the background can be tailored by changing the fiber parameters.

We use intense optoacoustic interactions involving the acoustic resonances confined in high-quality 51-cm-long silica microfibers to stabilize the harmonic mode-locking of fiber lasers at gigahertz repetition rates, which is controllable via tuning the microfiber thickness.

We successfully fabricate silica nanofibers that permit adiabatic transmission of the higher-order spatial modes by tapering wet-etched optical fibers. Phase-matched intermodal third-harmonic generation in a 760-nm-thick nanofiber is demonstrated with an efficiency higher than 1.05*10-4.

Noise-like quasi-continuous-wave background (qCWB) in a mode-locked fiber laser mediates various multi-pulse dynamics via long-range inter-pulse interactions. This raises a possibility to control multi-pulse phenomena through manipulation of the qCWB, while it has been rarely studied yet. Here, we investigate the qCWB engineering by imposing optomechanically induced impulsive intensity modulations on the qCWB. The mode-locked pulses excite electrostrictively several transverse acoustic resonance modes inside the fiber cavity, which eventually leads to the formation of sharp qCWB modulations regularly spaced in the time domain. In particular, we experimentally demonstrate that the characteristics of the optomechanical qCWB modulations can be adjusted by controlling the in-fiber optomechanical interactions via changing the structure of the fiber core, cladding, and coating. Our observations are supported by directly measured forward stimulated Brillouin scattering spectra of the intracavity fibers.

Photonic devices exhibiting all-optically reconfigurable polarization dependence with a large dynamic range would be highly attractive for active polarization control. Here, we report that strongly polarization-selective nonlinear optomechanical interactions emerge in subwavelength waveguides. By using full-vectorial finite element analysis, we find that at certain core ellipticities (aspect ratios) the forward simulated light scattering mediated by a specific acoustic mode is eliminated for one polarization mode, whereas that for the other polarization mode is rather enhanced. This intriguing phenomenon can be explained by the interplay between the electrostrictive force and radiation pressure and turns out to be tailorable by choice of waveguide materials., Comment: 5 pages, 5 figures

Mass sensing offering both a broad detection range and a high resolving power is essential for quantitative precision content analysis and high-yield mass production of various kinds of materials. Here, we propose and successfully demonstrate a novel type of simple low-cost optomechanical mass sensing employing an optical displacement detector that consists of a free-space Fabry-Perot optical cavity and an intra-cavity wedge prism pair, which provides an enhanced resolution and an extended capacity simultaneously. By implementing the null-method-based scheme of mass measurement, we achieve a resolution higher than 5000:1 (mass range from 1 kg) and an excellent linearity of R2>0.99998 in the prototype demonstration.

A variety of nonequilibrium multi-pulse states can emerge in a mode-locked laser through the interactions between the quasi-continuous-wave background (qCWB) and optical pulses inside the laser cavity. However, they have been long regarded as unpredictable and hardly controllable due to the noise-like nature of the qCWB, and relevant previous studies thus lack a clear understanding of their underlying mechanisms. Here, we demonstrate that the qCWB landscape can be manipulated via optoacoustically mediated interactions between the qCWB and mode-locked pulses, which dramatically alters the behaviors of multi-pulse dynamics in unprecedented manners. In this process, impulsive qCWB modulations are created at well-defined temporal locations, which act as the point emitters and attractive potentials for drifting pulse bunches and soliton rains. Hence, we can transport a single pulse bunch from a certain temporal position to another on the qCWB, and also make the soliton rain created and collided exclusively at specific temporal locations, in sharp contrast to the conventional cases. Our study opens up new possibilities to control the nonequilibrium multi-pulse phenomena precisely in the time domain, which would not only help the observation and clear understanding of undiscovered features of multi-pulse dynamics but offer a practical means of advanced optical information processing., Comment: 23 pages, 6 figures, 1 table

We experimentally demonstrate optomechanically driven nonlinear mechanical intermodal coupling by using high-Q square nano-membranes. Pumping via radiation forces as low as 34 pN, we achieve ultrahigh-efficiency coupling of the first-order mode into the higherorder ones.

An all-optically reconfigurable generation of optical vortices would be highly beneficial to the implementation of next-generation optical communication and advanced information processing. The previously demonstrated approaches based on the parametric nonlinear optical processes, however, have exhibited limited conversion efficiency due to the group velocity mismatch and nonlinear phase shifts, and require the cumbersome preparation of either the optical element or initial seed beam having a non-zero topological charge. Here, we propose and analyze a novel scheme for highly efficient all-optical generation and control of optical vortices based on the dynamic acoustic vortex grating created by forward stimulated intermodal Brillouin scattering in a subwavelength-hole photonic waveguide. The dual-frequency pump beams in two different hybrid optical modes drive an acoustic vortex mode, which transforms a signal in the fundamental optical mode into an optical vortex mode. This scheme not only eliminates the need for the initial preparation of an angular-momentum-carrying medium or an optical vortex seed but also guarantees high modal purity and nearly 100% conversion efficiency assisted by the energy-momentum conservation. We also investigate the feasibility and practicability of the subwavelength-hole waveguides by examining the intermodal conversion efficiency and robustness of guidance of the optical vortices, taking into account the impact of the Kerr-type nonlinear effects on the intermodal Brillouin interactions based on our rigorous full-vectorial analytical theory.

Objectives: The purpose of the study was to quantify lower limb foot kinematics, Center Of Mass (COM) and Center Of Pressure (COP) across three different surface terrain. Methods/Statistical Analysis: Thirty-one female walked over 7 m walkway at self-selected speed on three different surface terrain randomly A) Levelled surface, B) Soft urethane mat, C) Destabilising rock surface. A total of 8 infrared motion capture cameras and pressure measurement system were used to record the participant’s gait. As a statistical measure, one-way repeated measure ANOVA with Bonferroni post hoc test was used to observe differences across three surface terrains. Findings: The effect of surface condition on decreased speed and shorter stride length was observed. The difference was much larger on uneven surface condition with ankle externally rotated and shorter cop trajectory than even and control surface terrain. Surface characteristics imposed a greater challenge for maintaining dynamic balance by the control system which presumably changed the gait pattern for reducing the risk of fall. Application/Improvements: When designing footwear for outdoor, manufacturers should consider on the mechanism of the ankle joint which is prone to external rotation during destabilizing conditions. Thus, braces, lacing technique as well as outsole should be designed accordingly to reduce the risk of being injured.

The purpose of this study was to determine the effects of landing height information on landing strategy during a drop landing. Ten healthy male subjects(age: , height: , mass: ) participated in this study. Each participant was asked to jump with both legs off a 40 cm high box on one of the three plates with different thickness (0 cm, 13 cm, 26 cm). In the first condition, subjects were given both cognitive and visual information about the jumping heights. In the second, they were given only cognitive information without visual one, and in the third, no information about the height was provided to subjects. (Only the data collected from the 40 cm height landing were analyzed and reported in the present study.) The results showed that landing strategies during a double-leg drop landing from 40 cm height were not significantly affected by visual and cognitive information blockages. Also, there were no statistically significant differences in landing strategies between the three conditions even though the mean differences attained in this study seemed to warrant further studies investigating the relationship between landing strategies and cognitive information.

Scientists experimentally demonstrate a reconfigurable all-optical isolator based on the optical excitation of a gigahertz guided acoustic mode in a micrometre-sized photonic crystal fibre core. The work is expected to benefit advanced optical communications and all-optical signal-processing systems.

We report that extremely polarization-sensitive stimulated Brillouin scattering (SBS) emerges in subwavelength elliptical waveguides when mediated by surface acoustic waves. We find based on the full-vectorial finite element analysis that the SBS driven by a specific surface acoustic wave can be eliminated for one polarization mode, whereas for the other polarization mode, it is kept significant, while such strongly polarization-dependent Brillouin gain has not been observed in conventional SBS by bulk acoustic waves. We explain the origin of these intriguing polarization-selective phenomena in terms of the counter-balance between the photoelastic and moving-boundary effects. Our findings provide a host of unique possibilities of highly efficient all-optical control and stabilization of the polarization state of light.We report that extremely polarization-sensitive stimulated Brillouin scattering (SBS) emerges in subwavelength elliptical waveguides when mediated by surface acoustic waves. We find based on the full-vectorial finite element analysis that the SBS driven by a specific surface acoustic wave can be eliminated for one polarization mode, whereas for the other polarization mode, it is kept significant, while such strongly polarization-dependent Brillouin gain has not been observed in conventional SBS by bulk acoustic waves. We explain the origin of these intriguing polarization-selective phenomena in terms of the counter-balance between the photoelastic and moving-boundary effects. Our findings provide a host of unique possibilities of highly efficient all-optical control and stabilization of the polarization state of light.

The scattering of laser light by acoustic phonons confined within a photonic crystal fibre reveals unexpected highly nonlinear acoustic modes that behave like the Raman-active modes of a molecule.

We describe two methods for evaluating the dead time of a time-to-amplitude converter (TAC). The dead time is obtained by measuring either the corresponding time interval in an oscilloscope trace or the relation between the single count rate and the coincidence count rate. Values for the TAC dead time are obtained in the range from 3.4 µs to 14.3 µs for the two methods with respective standard uncertainties of 2.9 × 10−8 s and 3.3 × 10−9 s. The TAC dead time is applied to the calibration of coincidence-counting measurements of optical transmission and photon-heralding efficiency.

We demonstrate direct excitation and broadband guidance of polarization vector beams (PVBs) in commercially stock-available small-core ultrahigh-NA optical fibers. A simple numerical analysis supports the experimental results and provides criteria for stable guidance of PVBs.

We experimentally demonstrate the 3rd-order seeded parametric down-conversion in a silica submicro-wire. Amplification of a 1597.38 nm seed beam is observed upon co-launching a 532.46 nm pump beam in the HE12 mode of the wire.

This paper demonstrates and characterizes a novel wavelength-tunable single-frequency erbium-doped fiber ring laser incorporating an all-fiber acoustooptic tunable bandpass filter and a self-constructed saturable absorption grating (SAG). Stable single-longitudinal-mode operation was achieved over the wavelength range of 48 nm with a sidemode suppression ratio higher than 50 dB. The wavelength tuning characteristics, and the laser dynamics in wavelength switching and sweeping are analyzed in detail. A theoretical analysis on the effect of the SAG is also described.

We propose and demonstrate methods for suppressing the polarization dependence in the interrogation of birefringent fiber Bragg gratings. A wavelength-swept fiber laser with a polarized output was used as the light source. Two polarization-averaging methods, a depolarization scheme and a polarization scrambling scheme, were investigated and compared. The proposed techniques successfully stabilized the reflection spectrum of a birefringent grating regardless of the polarization state of the source laser and birefringence of the lead fiber. The results of this work eliminate one of the major practical difficulties in current fiber Bragg grating interrogation.

We investigated the loss modulation effect on the second-harmonically mode-locked erbium-doped fiber laser based on the Sagnac loop reflector with a Y-branch LiNbO/sub 3/ phase modulator. We found that even a small loss modulation originating from the phase modulator could cause severe peak power difference between two output pulses in a modulation period. It was also found that the peak power difference was sensitively dependent on the modulation frequency. By numerical simulation, we quantitatively analyzed the relation between the peak power difference and the amount of loss modulation, which agreed well with the experimental results.

Dynamics of a coupled-cavity mode-locked soliton fiber laser is experimentally investigated at both the single-pulsing and multi-pulsing regimes. In particular, multi-pulsing dynamics can be widely controlled by tuning the cavity coupling strength and intra-cavity loss.

We propose and experimentally demonstrate a novel configuration for an acoustooptic tunable bandpass filter based on intermodal coupling in a two-mode fiber. The double-pass scheme provides zero frequency-shift, bandwidth narrowing, and enhanced extinction ratio. A 3-dB bandwidth of 2.0 nm, insertion loss of 5.6 dB, and sidelobe suppression ratio of 14 dB were achieved. The wavelength tuning range was greater than 90 nm for the transmission dynamic range larger than 20 dB. Multiwavelength operation of a single device is achieved by simply applying multifrequency electrical signal. Unwanted intensity modulation of the multiwavelength filter is also investigated

We demonstrate a narrow-bandwidth acoustooptic tunable filter with very low polarization-sensitivity using a dispersion-compensating fiber that has a large group index difference between the core and the cladding modes with a specific stress distribution. The 3-dB bandwidth of the filter is 0.8 nm with the interaction length of 10 cm, and the polarization-dependent center-wavelength splitting is 0.04 nm at the wavelength around 1550 nm. The origin of the low polarization-dependence is successfully explained through the analysis on the stress field in the fiber.

Coherent optically-driven GHz acoustic waves, tightly guided in the micron-sized core of photonic crystal fibre, enable reconfigurable dynamic optical isolation and switching, providing new functionality that is useful in various types of all-optical fibre systems.

Recent results on optomechanical and optoacoustic nonlinearities in optical fibres are reported. In a new type of a microstructured silica fibre, comprising two ultra-thin closely spaced glass waveguides, an extremely high and optically broadband optomechanical nonlinearity is shown to occur. This nonlinearity originates from the optical gradient forces between coupled waveguides, can exceed the Kerr effect by many orders of magnitude and allows the formation of stable self-trapped optical modes that represent a novel kind of optical soliton. Furthermore, optoacoustic interaction via electrostriction in the micron-sized core of a photonic crystal fibre is studied. It is demonstrated, that coherent optically-driven acoustic waves, tightly guided in the core, can facilitate in-fibre dynamic optical isolation and all-optical switching.

I will discuss some recent experimental studies on novel types of light-matter interactions in micro/nano-structured silica optical waveguides, in particular focusing on new nonlinear optomechanical effects and their applications.

A novel kind of nanostructured optical fiber, displaying an extremely high and optically broadband optomechanical nonlinearity, is presented. It comprises two closely spaced ultrathin glass membranes (webs) suspended in air and attached to the inner walls of a glass fiber capillary. Light guided in this dual-web structure can exert attractive or repulsive pressure on the webs, causing them to be pushed together or pulled apart. The elastic deflection of the webs is, in turn, coupled to the electromagnetic field distribution and results in a change in the effective refractive index within the fiber. Employing a pump-probe technique in an interferometric setup, optomechanically induced refractive index changes more than 10^{4} times larger than the Kerr effect are detected. Theoretical estimates of the optomechanical nonlinearity agree well with the experimental results. The dual-web fiber combines the sensitivity of a microoptomechanical device with the versatility of an optical fiber and could trigger new developments in the fields of nonlinear optics, optical metrology, and sensing.

We will present our recent progress in nonlinear optomechanics in a platform of microstructured optical fibers. By tightly confining transverse mechanical motion and guided laser light simultaneously in a micron-sized glass fiber core, we have successfully demonstrated novel types of nonlinear optomechanical effects at modest optical powers, thanks to the strongly enhanced optomechanical interactions. We will describe the principles, characteristics and potential applications of the effects.

Leaky orbital angular momentum (OAM) resonances cause a series of sharp dips in the transmission spectrum of a twisted PCF. Analysis shows that these OAM resonances are precisely quantized, despite the complexity of the structure.

Fiber with a Twist Optic fibers provide the backbone of communication networks. Controlling light propagation through the fiber is key to maximizing the capacity of information flow. By introducing a literal twist on the photonic crystal fiber, Wong et al. (p. 446 ) show that adding chirality to the cladding surrounding the core may provide another route to manipulating the transmission of light. Coupling between the twisted cladding and the core results in dips in the transmission spectrum, which are dependent on the degree of twist introduced into the fiber. Such twisted microstructure fibers may offer opportunities for coupling, filtering and manipulating light.

The non-resonant optomechanical nonlinearity is enhanced in dual-nanoweb fibers by improved design. A 10-fold increase in Q-factor, resulting in a resonant nonlinearity 200,000 times larger than the Kerr effect, is observed after evacuating the fiber.

Forward stimulated light scattering by GHz acoustic resonances (ARs) guided in a µm-sized photonic crystal fiber (PCF) core gives rise to two classes of scattering: forward stimulated Raman-like scattering (SRLS) between pump and Stokes waves in the same optical mode [1], and forward stimulated inter-polarization scattering (SIPS) between orthogonally polarized pump and Stokes waves [2]. Here we study for the first time the transient switching dynamics of forward SIPS, building on previous studies that were restricted to the steady-state regime [2].

A continuously twisted PCF can be viewed as a one-dimensional metamaterial in which both ϵ and μ tensors develop off-diagonal elements. Finite-element calculations confirm the appearance of unique loss peaks in the experimental transmission spectrum.