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Background Effortful swallowing training (EST) is a remedial method for the training of swallowing-related muscles in the oropharyngeal phase. However, clinical evidence of its effectiveness is insufficient. Aims To investigate the effects of EST on tongue strength and swallowing function in patients with stroke. Methods & procedures Stroke patients with dysphagia were randomly assigned to one of two groups: an experimental group (n = 12) and a control group (n = 12). The experimental group underwent EST, while the control group performed saliva swallowing. Training was conducted 5 days per week for 4 weeks. Both groups underwent conventional dysphagia treatment for 30 min/day, 5 days/week for 4 weeks. Outcomes & results Tongue strength was assessed using the Iowa Oral Performance Instrument. The Videofluoroscopic Dysphagia Scale (VDS), based on a videofluoroscopic swallowing study, was used to analyze oropharyngeal swallowing function. The experimental group showed greater improvements in anterior and posterior tongue strength compared with the control group (p = 0.046 and 0.042, respectively), and greater improvement in the oral phases of the VDS (p = 0.017). Conclusions & implications We recommend EST as a remedial strategy for improving tongue strength and oral swallowing function in patients with stroke.

We demonstrate an acousto-optic mode converter based on a tapered optical fiber to efficiently generate orbital angular momentum states of light. In our scheme an acoustic wave is deployed to the waist of tapered optical fiber where two degenerate HE21 modes leading to +1 and −1 orbital angular momentum eigen-modes are resonantly excited. The excitation of TM01 and TE01 modes is suppressed by enlarging the intermodal index difference between near-degenerate spatial modes. Numerical calculation for optimization of the taper diameter is provided. The experimental characterization of generated states is performed by analyzing the output far-field pattern and the spatial interference fringes with a uniform reference beam.

This letter presents an experimental method to compensate for the differential group delay between the core modes in a multi-core fiber. Optical fiber sections are sequentially spliced with azimuthal offsets such that light initially launched to any cores can propagate through the combination of the same lengths of different cores, resulting in ideally uniform group delay. The differential group delays before and after the compensation are measured by wavelength-domain Mach–Zehnder interferometry through multi-core fiber sections. The experimental results show that the group delay compensation is practically limited by non-uniformity of the multi-core fiber.

We demonstrate time-multiplexing of heralded single-photon sources using switchable optical fiber d elay l ines a ided b y p olarization-space m ultiplexing. Relative-multiplexing HOM interferometry tests the indistinguishability of output photons.

We experimentally demonstrate a time-multiplexing method for pulse-pumped heralded single-photon sources using switchable optical fiber delay lines. The optical fibers constitute a 32-channel binary-division photon buffer that can multiplex time slots into single temporal mode to enhance single-photon generation rate without increasing multi-photon noise. Relative time multiplexing using the same actively controlled variable delay realizes Hong-Ou-Mandel interferometry by two photons produced in arbitrary two time-bins. The interference dip depth in good agreement with theory verifies path length matching within the photonic coherence length and dispersion compensation of the optical fiber delay sections. We independently confirm by low-coherence interferometry that the internal optical path lengths of the optical switches are constant during the switching operations.

We calculate the operation wavelength range of polarization controllers based on rotating wave plates such as paddle-type optical fiber devices. The coverages over arbitrary polarization conversion or arbitrary birefringence compensation are numerically estimated. The results present the acceptable phase retardation range of polarization controllers composed of two quarter-wave plates or a quarter-half-quarter-wave plate combination, and thereby determines the operation wavelength range of a given design. We further prove that a quarter-quarter-half-wave-plate combination is also an arbitrary birefringence compensator as well as a conventional quarter-half-quarter-wave-plate combination, and show that the two configurations have the identical range of acceptable phase retardance within the uncertainty of our numerical method.

We present a practical calibration method of the detection efficiency (DE) of single photon detectors (SPDs) in a wide wavelength range from 480 nm to 840 nm. The setup consists of a GaN laser diode emitting a broadband luminescence, a tunable bandpass filter, a beam splitter, and a switched integrating amplifier which can measure the photocurrent down to the 100 fA level. The SPD under test with a fibre-coupled beam input is directly compared with a reference photodiode without using any calibrated attenuator. The relative standard uncertainty of the DE of the SPD is evaluated to be from 0.8% to 2.2% varying with wavelength (k = 1).

Fibre transport of multi-dimensional photonic quantum states promises high information capacity per photon without space restriction. This work experimentally demonstrates transmission of spatial ququarts through multi-core optical fibres and measurement of the entanglement between two fibres with quantum state analyzers, each composed of a spatial light modulator and a single-mode fibre. Quantum state tomography reconstructs the four-dimension entangled state that verifies the nonlocality through concurrences in two-dimensional subspaces, a lower bound of four-dimensional concurrence and a Bell-type CGLMP inequality.

We demonstrate the measurement of detection efficiency, the probability for the successful detection of a single photon incident on a detector, in a wide wavelength range from 250 nm to 1000 nm. The method is based on the responsivity comparison of two detectors by using a tunable monochromatic light source at a radiant power controlled to the pico-Watt level. As the reference detector, a photodiode with a switched integrating amplifier is used, whose spectral responsivity is calibrated at a photo-current level of pico-Ampere. A fibre-based spatial filter is used to form a beam focus that is focused to a diameter of less than 100 µm at the detector under test. The typical uncertainty of the detection-efficiency measurement for a Si-based single photon avalanche photodiode is evaluated to be less than 1% as a relative standard uncertainty (k = 1), which is currently limited by the characteristics of the tunable source.

We demonstrate an experimental method to control four-dimensional spatially entangled states between two multi-core optical fibers based on spatial beam shaping of a laser that pumps spontaneous parametric down-conversion.

Nanoimprint lithography has been widely used in various applications as a promising micro/nanofabrication tool. In the thermal nanoimprint process, optimization of important process parameters such as temperature, pressure, and pressure holding time is greatly needed to successfully imprint micro-and nanoscale patterns in a resist material. In this study, both experimentation and numerical simulation were performed to extend the understanding of the behaviour of polymer materials and to optimize process condition effectively during the thermal imprint process. The effects of the process conditions on the polymer deformation are discussed to achieve a rapid and high throughput thermal imprint process.

High-dimensional entanglement is a valuable resource for secure and efficient quantum information processing. A major challenge for practical use of multidimensional quantum systems is the establishment of controls over arbitrary superposition states in realistic conditions. This work demonstrates spatially entangled photon pairs propagating through two separate four-core optical fibers with the amplitudes and phases of the superposition being independently controllable. Using quantum state analyzers that can detect arbitrary multicore superposition states, Bell-type CGLMP inequalities in two, three, and four dimensions are directly tested. Enhanced violation of the inequality by slight nonmaximality of entanglement is also demonstrated.

We propose and demonstrate an experimental technique that generates and measures arbitrary superpositions of the core modes in a multi-core fiber. This technique is potentially useful for transmission of high-dimensional quantum states through optical fiber.

This paper describes a novel non-contact laser-ultrasound system which is compact and has a high level of immunity to ambient vibration, based on the use of an optical fibre Fabry–Perot interferometer as an acoustic detector. The new optical acoustic detector was employed for measuring a high-frequency acoustic wave of small amplitude generated by a relatively low output power source using an erbium-doped fibre amplifier. Together with the characteristics of the proposed detector, the preliminary results of 80 MHz laser-ultrasound experiments on an aluminium film are described.

Optical fibre techniques for detecting ultrasonic waves are, in principle, well established. The ultrasonic wave could impose a pressure and/or strain field on an optical fibre in its path and this pressure and/or strain modulation would in turn be observed as a change in optical delay along the fibre length. The delay change may be detected interferometrically, polarimetrically or through using the induced strain changes in Bragg gratings. The resulting fibre optic detection system can perform as well in terms of signal to noise ratio over specified bandwidths as more established piezoelectric ceramic detectors. Additionally fibre systems can also perform some signal processing, particularly beam forming, and have inherently much higher spatial and temporal bandwidth than the piezoceramic precursor. This paper explores some of the options available for the use of fibre optics in detecting ultrasound and demonstrates the elements of basic signal processing techniques including examples of source location (equivalent to fault detection) and optical fibre beam forming. Whilst these functions can be performed using piezoceramics, and indeed can be made more adaptable through electronic element by element processing on large arrays, fibre optic systems in contrast offer substantial benefits in terms of a much simplified array interconnect (only the fibre itself is required) and material compatibility especially for high performance high strain range mechanical systems.

Utilizing time multiplexing of a heralded single-photon source based on spontaneous parametric downconversion pumped by periodic laser pulses, we observed large enhancements in the single-photon probability.

In this paper, we demonstrate a novel all-fiber wavelength-tunable acoustooptic switch utilizing intermodal coupling in a two-mode fiber (TMF). Its all-fiber configuration consisting of a fiber acoustooptic tunable filter and a mode-selective coupler results in the low loss ( 50 nm, the switching time of 40 /spl mu/sec, and the crosstalk of 20 dB were achieved. By controlling the design parameters of the two-mode fiber, the 3-dB bandwidth of the switched signal was varied from 2.5 nm to >35 nm. A novel all-fiber dynamic optical add-drop multiplexer is also demonstrated using two acoustooptic switches in series.

A fiber-optic analogue to an externally driven three-level quantum state is demonstrated by acousto-optic coupling of the spatial modes in a few-mode fiber. Under the condition analogous to electromagnetically induced transparency, a narrow-bandwidth transmission within an absorption band for the fundamental mode is demonstrated. The presented structure is an efficient converter between the fundamental mode and the higher-order modes that cannot be easily addressed by previous techniques, therefore can play a significant role in the next-generation space-division multiplexing communications as an arbitrarily mode-selectable router. (C) 2014 Optical Society of America

Beam recombination characteristics were numerically investigated in array laser amplification using stimulated Brillouin scattering phase conjugation. To clarify the effect of piston errors due to imperfect phase locking, spatial intensity profiles of the beam recombination output were calculated in both the near and the far field on the basis of Rayleigh-Sommerfeld diffraction theory. The analyses indicate that piston errors are seriously detrimental to the quality of a beam recombination output and should be eliminated by a proper phase locking. It is also found that the gap between the beam splitting-combining wedges has a negligible effect.

We report the experimental demonstration of the Young's double-slit type spatial quantum interference of the three-photon N00N state, showing three times denser non-classical spatial interference fringes than that of the single-photon state.

A heralded three-photon NOON state is generated from two pairs of photons produced by spontaneous parametric down-conversion (SPDC). The measured four-photon coincidences reveal fringes three times finer than single-photon interference.

We present a CW optical parametric oscillator (OPO) based on quasi-phase-matching. Pumped at 532 nm, the OPO provides coherent radiation from 800 nm to 900 nm and from 1300 nm to 1600 nm for signal and idler, respectively. Application for calibrating the spectral responsivity of Si and InGaAs photodiodes is demonstrated.

We propose and demonstrate a novel apodization technique for an elliptical-core two-mode fiber acousto-optic filter by twisting the fiber and adjusting the acoustic polarization. The sidelobe suppression in the filter spectrum was improved from -9.7 to -15.5 dB. A theoretical analysis that includes acoustic birefringence explains the experimental results with good agreement.

We describe a novel optical acoustic detector based on a bias-controlled fiber Fabry-Perot interferometer. The detector has a broad bandwidth from 10 Mhz to a few gigahertz and higher sensitivity than conventional systems, which are useful for noncontact characterization of microsamples based on laser ultrasound.

In this work we present a signal processing method applied to totally non-contact laser generated and detected acoustic waves for the estimation of the main elastic properties (Poisson ratio and Young's modulus) of structural materials.