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Miniaturized sound generators are attractive to realize intriguing functions. Thermoacoustic device's application is seriously limited due to the frequency‐doubling phenomenon. To address this issue, photoacoustic sound generator is considered as a promising alternative. Here, based on vertical single‐wall carbon nanotubes (CNTs) array, we introduce a photoacoustic sound generator with internal nano‐Helmholtz cavity. Different from traditional device that generates sound by periodically heating up the open space air around material, this sound generator produces an audio signal by forming a forced vibration of the air inside the CNTs. Interestingly, anomalous photoacoustic behavior is observed that the sound pressure level (SPL) curve has a resonance peak, the corresponding frequency of which is inversely proportional to the CNTs array's height. Furthermore, the energy conversion efficiency of this photoacoustic device is 1.64 times as large as that of a graphene sponge‐based photoacoustic device. Most importantly, this device can be employed for music playing, bringing a new clew for the development of musical instruments in the future. [ABSTRACT FROM AUTHOR]

A benchmark experiment is reported that demonstrates the shortening of hard X‐ray pulses in a synchrotron‐based optical pump–X‐ray probe measurement. The pulse‐shortening device is a photoacoustic Bragg switch that reduces the temporal resolution of an incident X‐ray pulse to approximately 7.5 ps. The Bragg switch is employed to monitor propagating sound waves in nanometer thin epitaxial films. From the experimental data, the pulse duration, diffraction efficiency and switching contrast of the device can be inferred. A detailed efficiency analysis shows that the switch can deliver up to 109 photons s−1 in high‐repetition‐rate synchrotron experiments. [ABSTRACT FROM AUTHOR]

Background: MIRUS™ is a device for target-controlled inhalational sedation in the ICU in combination with use of isoflurane, or sevoflurane, or desflurane. The feasibility of this device has recently been proven; however, ICU staff exposure may restrict its application. We investigated ICU ambient room pollution during daily work to estimate ICU personnel exposure while using MIRUS™.Methods: This observational study assessed pollution levels around 15 adult surgical patients who received volatile anaesthetics-based sedation for a median of 11 hours. Measurements were performed by photoacoustic gas monitoring in real-time at different positions near the patient and in the personnel's breathing zone. Additionally, the impact of the Clean Air™ open reservoir scavenging system on volatile agent pollution was evaluated.Results: Baseline concentrations [ppm] during intervention and rest periods were isoflurane c¯mean = 0.58 ± 0.49, c¯max = 5.72; sevoflurane c¯mean = 0.22 ± 0.20, c¯max = 7.93; and desflurane c¯mean = 0.65 ± 0.57, c¯max = 6.65. Refilling MIRUS™ with liquid anaesthetic yielded gas concentrations of c¯mean = 2.18 ± 1.48 ppm and c¯max = 13.03 ± 9.37 ppm in the personnel's breathing zone. Air pollution in the patient's room was approximately five times higher without a scavenging system.Conclusion: Ambient room pollution was minimal in most cases, and the measured values were within or below the recommended exposure limits. Caution should be taken during refilling of the MIRUS™ system, as this was accompanied by higher pollution levels. The combined use of air-conditioning and gas scavenging systems is strongly recommended. [ABSTRACT FROM AUTHOR]

We report on the wavelength and time-domain responses of a lumped or distributed fiber-optic modalmetric interferometer under a very smooth pressure ( fingerprint) disturbances in the 1530-1610 nm wavelength range. A simple method to quantify such disturbances is proposed. It is shown that the lateral offset shift of 5.9 mm between the single-mode and the multimode fiber splice makes the device even more sensitive. It was measured an electrical signal power enhancements of 3.5 and 7.5 dB for 1 m and 1.65 km multimode fiber link, respectively. [ABSTRACT FROM AUTHOR]

ABSTRACT This article introduces a new approach for three-dimensional ultrasound imaging using a line-focused ultrasound transducer. Based on Schlieren imaging approach, the presented method demonstrates real-time, two-dimensional optical visualization of ultrasound waves using a CCD camera and presents fast three-dimensional ultrasound imaging capability using a continuous scanning approach. An experimental setup was constructed and a target sample was successfully imaged using the proposed approach. Compared to the conventional ultrasound imaging approaches, this approach can improve the imaging acquisition time significantly and has a potential to be implemented for fast three-dimensional ultrasound imaging. © 2017 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:770-773, 2017 [ABSTRACT FROM AUTHOR]

The poly(maleic anhydride-alt-1-octadecene-poly(ethylene glycol)) (C18PMH-PEG) modified single-walled carbon nanohorns (SWNHs) are designed with high stability and biocompatibility. The as-prepared SWNHs/C18PMH-PEG not only can serve as an excellent photothermal agent but also can be used as a promising photoacoustic imaging (PAI) agent both in vitro and in vivo due to its strong absorption in the near infrared (NIR) region. The PAI result reveals that the SWNHs/C18PMH-PEG possesses ultra long blood circulation time and can significantly be accumulated at the tumor site through the enhanced penetration and retention (EPR) effect. The maximum accumulation of SWNHs/C18PMH-PEG at tumor site could be achieved at the time point of 24 h after intravenous injection, which is considered to be the optimal time for the 808 nm laser treatment. The subsequent photothermal ablation of tumors can be achieved without triggering any side effects. Therefore, a PAI guided PTT platform based on SWNHs is proposed and highlights the potential theranostic application for biomedical uses. [ABSTRACT FROM AUTHOR]

Aim To compare the efficacy of photon-induced photoacoustic streaming (PIPS) technique with conventional, sonic and ultrasonic irrigation on the removal of apically placed dentinal debris from an artificial groove created in a root canal. Methodology Root canal preparation was performed up to size 40 on 48 extracted single-rooted teeth using ProTaper rotary instruments. The specimens were then split longitudinally, and a standardized groove was prepared in the apical part of each segment. Each groove was filled with dentinal debris mixed with 5% NaOCl. Each tooth was reassembled and irrigated as follows: (i) conventional irrigation with 1% NaOCl, (ii) sonic, (iii) ultrasonic irrigation, and (iv) PIPS. The root segments were disassembled, and the amount of remaining dentinal debris was evaluated under a stereomicroscope at 209 magnification, using a four-grade scoring system. The data were evaluated statistically using Kruskal-Wallis and Mann-Whitney U-tests with a 95% confidence level (P = 0.05). Results Photon-induced photoacoustic streaming removed significantly more dentinal debris than conventional irrigation (P < 0.001), sonic irrigation (P < 0.001) or ultrasonic irrigation (P = 0.005). There was no significant difference between sonic and ultrasonic irrigation (P = 0.377). Conclusions Photon-induced photoacoustic streaming was more effective than conventional, sonic and ultrasonic irrigation in the removal of apically placed dentinal debris. [ABSTRACT FROM AUTHOR]

Miniaturized optical detectors of ultrasound represent a promising alternative to piezoelectric technology and may enable new minimally invasive clinical applications, particularly in the field of optoacoustic imaging. However, the use of such detectors has so far been limited to controlled lab environments, and has not been demonstrated in the presence of mechanical disturbances, common in clinical imaging scenarios. Additionally, detection sensitivity has been inherently limited by laser noise, which hindered the use of sensing elements such as optical fibers, which exhibit a weak response to ultrasound. In this work, coherence-restored pulse interferometry (CRPI) is introduced - a new paradigm for interferometric sensing in which shot-noise limited sensitivity may be achieved alongside robust operation. CRPI is implemented with a fiber-based resonator, demonstrating over an order of magnitude higher sensitivity than that of conventional 15 MHz intravascular ultrasound probes. The performance of the optical detector is showcased in a miniaturized all-optical optoacoustic imaging catheter. [ABSTRACT FROM AUTHOR]

Rapid, precise, and globally comparable methods for monitoring greenhouse gas ( GHG) fluxes are required for accurate GHG inventories from different cropping systems and management practices. Manual gas sampling followed by gas chromatography ( GC) is widely used for measuring GHG fluxes in agricultural fields, but is laborious and time-consuming. The photo-acoustic infrared gas monitoring system ( PAS) with on-line gas sampling is an attractive option, although it has not been evaluated for measuring GHG fluxes in cereals in general and rice in particular. We compared N2O, CO2, and CH4 fluxes measured by GC and PAS from agricultural fields under the rice-wheat and maize-wheat systems during the wheat (winter), and maize/rice (monsoon) seasons in Haryana, India. All the PAS readings were corrected for baseline drifts over time and PAS- CH4 (PCH4) readings in flooded rice were corrected for water vapor interferences. The PCH4 readings in ambient air increased by 2.3 ppm for every 1000 mg cm−3 increase in water vapor. The daily CO2, N2O, and CH4 fluxes measured by GC and PAS from the same chamber were not different in 93-98% of all the measurements made but the PAS exhibited greater precision for estimates of CO2 and N2O fluxes in wheat and maize, and lower precision for CH4 flux in rice, than GC. The seasonal GC- and PAS-N2O (PN2O) fluxes in wheat and maize were not different but the PAS-CO2 ( PCO2) flux in wheat was 14-39% higher than that of GC. In flooded rice, the seasonal PCH4 and PN2O fluxes across N levels were higher than those of GC- CH4 and GC-N2O fluxes by about 2- and 4fold, respectively. The PAS (i) proved to be a suitable alternative to GC for N2O and CO2 flux measurements in wheat, and (ii) showed potential for obtaining accurate measurements of CH4 fluxes in flooded rice after making correction for changes in humidity. [ABSTRACT FROM AUTHOR]

Purpose: Image quantification in optoacoustic tomography implies the use of accurate forward models of excitation, propagation, and detection of optoacoustic signals while inversions with high spatial resolution usually involve very large matrices, leading to unreasonably long computation times. The development of fast and memory efficient model-based approaches represents then an important challenge to advance on the quantitative and dynamic imaging capabilities of tomographic optoacoustic imaging. Methods: Herein, a method for simplification and acceleration of model-based inversions, relying on inherent symmetries present in common tomographic acquisition geometries, has been introduced. The method is showcased for the case of cylindrical symmetries by using polar image discretization of the time-domain optoacoustic forward model combined with efficient storage and inversion strategies. Results: The suggested methodology is shown to render fast and accurate model-based inversions in both numerical simulations and post mortem small animal experiments. In case of a full-view detection scheme, the memory requirements are reduced by one order of magnitude while high-resolution reconstructions are achieved at video rate. Conclusions: By considering the rotational symmetry present in many tomographic optoacoustic imaging systems, the proposed methodology allows exploiting the advantages of model-based algorithms with feasible computational requirements and fast reconstruction times, so that its convenience and general applicability in optoacoustic imaging systems with tomographic symmetries is anticipated. [ABSTRACT FROM AUTHOR]

Degradation is among the most important properties of biomaterial scaffolds, which are indispensable for regenerative medicine. The currently used method relies on the measurement of mass loss across different samples and cannot track the degradation of an individual scaffold in situ. Here we report, for the first time, the use of multiscale photoacoustic microscopy to non-invasively monitor the degradation of an individual scaffold. We could observe alterations to the morphology and structure of a scaffold at high spatial resolution and deep penetration, and more significantly, quantify the degradation of an individual scaffold as a function of time, both in vitro and in vivo. In addition, the remodeling of vasculature inside a scaffold can be visualized simultaneously using a dual-wavelength scanning mode in a label-free manner. This optoacoustic method can be used to monitor the degradation of individual scaffolds, offering a new approach to non-invasively analyze and quantify biomaterial-tissue interactions in conjunction with the assessment of in vivo vascular parameters. [ABSTRACT FROM AUTHOR]

The photoacoustic signal from the depletion layer formed within a planar metal-semiconductor-metal (MSM) structure was detected using the photoacoustic method. To measure the distribution of the photoacoustic signal from the depletion layer, the surface of the sample was illuminated and scanned by an intensity-modulated optical beam. The amplitude and phase shifts of the observed signal increased with an increase in the reverse bias in the Schottky barrier. The intensity distribution of the photoacoustic signal corresponded closely to the position of the photocurrent distribution, showing the presence of the depletion layer as measured by the photoelectric method. This demonstrates clearly that the photoacoustic signal reflects the presence of the depletion layer in semiconductor materials, and that the photoacoustic method can be used effectively for the visualization of the depletion layer. © 2013 Wiley Periodicals, Inc. Electron Comm Jpn, 96(2): 65-70, 2013; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/ecj.10402 [ABSTRACT FROM AUTHOR]

Tellurite glasses have long been recognized as interesting materials for fiber and integrated optics, but it is only recently that the first steps toward high-performance planar devices have been taken. This study reviews the opportunities for planar tellurite devices, the current state of the art of planar waveguide devices, and considers the areas of research required to move the materials platform to the level of maturity needed to realize its promise. [ABSTRACT FROM AUTHOR]

Purpose: Recently reported quantitative photoacoustic tomography (PAT) has significantly expanded the utilities of PAT because it allows for recovery of tissue optical absorption coefficient which directly correlates with tissue physiological information. However, the recovery of optical absorption coefficient by the existing quantitative PAT approaches strongly depends on the accuracy of absorbed energy density distribution, and on the knowledge of accurate strength and distribution of incident light source. The purpose of this study is to develop a new algorithm for the reconstruction of optical absorption coefficient that does not depend on these initial parameters. Methods: Here the authors propose a novel one-step reconstruction approach that can directly recover optical absorption coefficient from photoacoustic measurements along boundary domain. The authors validate the method using simulation and phantom experiments. Results: The authors have demonstrated experimental evidence that it is possible to directly recover optical absorption coefficient maps using boundary photoacoustic measurements coupled with the photon diffusion equation in just one step. The authors found that the method described is able to quantitatively reconstruct absorbing objects with different sizes and optical contrast levels. Conclusions: Compared to the authors' previous two-step methods, the reconstruction results obtained here show that the one-step scheme can significantly improve the accuracy of absorption coefficient recovery. [ABSTRACT FROM AUTHOR]

Purpose: Both photoacoustic tomography (PAT) and fluorescence molecular tomography (FMT) can be used for molecular imaging when contrast agents are administrated. The goal of this work is to comparatively evaluate the performance of reflection-mode PAT and FMT in common phantom when indocyanine green (ICG) was used as a contrast agent. Methods: Reflection-mode PAT and FMT systems were developed. Target embedded in a background phantom with different ICG concentration, size, and depth location was examined. Comparisons were made in terms of target morphology, spatial resolution, and sensitivity between the two modalities. Results: Phantom results showed that PAT and FMT gave different image morphology. PAT offered higher spatial resolution, while FMT provided higher sensitivity. Thus, improved target detection could be achieved by correlating the complementary information obtained from the two modalities. Conclusions: The combination of high resolution PAT and high sensitivity FMT will provide a more complete range of pathology spectra for more reliable target detection, suggesting a potentially better diagnostic tool when this combination coupled with the administration of ICG as contrast agent is applied to clinical problems in the future. [ABSTRACT FROM AUTHOR]

Purpose: The authors present the design and evaluation of a second-generation (G2) hybrid photoacoustic tomography (PAT) and diffuse optical tomography (DOT) imaging system for detection of breast cancer. The combined PAT/DOT system takes full advantages of two different modalities to provide complementary information and most accurate recovery of tissue optical properties. Methods: This system was designed to produce cross-section images of breast tissue with a ring-shaped home-made array of 64 wideband acoustic transducers combined with an array of 16/16 source/detector optical fiber bundles. A scanning light delivery system was built to illuminate a large area of breast tissue for optimized tissue penetration. Finite element reconstruction methods for quantitative PAT and DOT were utilized to recover absorption and scattering coefficients of tissue-mimicking phantoms and ex vivo tumor tissue. Results: Performances of the acoustic transducer array and the PAT/DOT system were investigated in detail. Frequency response of the transducers is from 380 kHz to 1.48 MHz and maximum frequency response is up to 2 MHz. Directivity of a single element in the array is ±30°. The PAT/DOT system offers a spatial resolution of ∼0.5 mm for PAT and of ∼4.0 mm for DOT. Quantitatively accurate absorption and scattering coefficients were obtained from both the phantom and ex vivo experiments. Conclusions: The PAT/DOT system provided better PAT images when the targets were smaller in size and located near the center of the background phantom, while better DOT images were obtained when the targets were larger in size and located away from the center of the background. The successful results obtained from both the phantom and ex vivo experiments will allow us to test the hybrid system in humans with breast cancer in the near future. [ABSTRACT FROM AUTHOR]

Purpose: Optoacoustic imaging enables mapping the optical absorption of biological tissue using optical excitation and acoustic detection. Although most image-reconstruction algorithms are based on the assumption of a detector with an isotropic sensitivity, the geometry of the detector often leads to a response with spatially dependent magnitude and bandwidth. This effect may lead to attenuation or distortion in the recorded signal and, consequently, in the reconstructed image. Methods: Herein, an accurate numerical method for simulating the spatially dependent response of an arbitrary-shape acoustic transducer is presented. The method is based on an analytical solution obtained for a two-dimensional line detector. The calculated response is incorporated in the forward model matrix of an optoacoustic imaging setup using temporal convolution, and image reconstruction is performed by inverting the matrix relation. Results: The method was numerically and experimentally demonstrated in two dimensions for both flat and focused transducers and compared to the spatial-convolution method. In forward simulations, the developed method did not suffer from the numerical errors exhibited by the spatial-convolution method. In reconstruction simulations and experiments, the use of both temporal-convolution and spatial-convolution methods lead to an enhancement in resolution compared to a reconstruction with a point detector model. However, because of its higher modeling accuracy, the temporal-convolution method achieved a noise figure approximated three times lower than the spatial-convolution method. Conclusions: The demonstrated performance of the spatial-convolution method shows it is a powerful tool for reducing reconstruction artifacts originating from the detector finite size and improving the quality of optoacoustic reconstructions. Furthermore, the method may be used for assessing new system designs. Specifically, detectors with nonstandard shapes may be investigated. [ABSTRACT FROM AUTHOR]

Knowledge of the optical properties of human skin in the ultraviolet range is fundamental for photobiologic research. However, optical properties of human skin in the ultraviolet spectral range have so far mainly been measured ex vivo. We have determined the absorption spectra of human skin in vivo in the wavelength range from 290 to 341 nm in 3 nm steps using laser optoacoustics. In this technique, optical properties are derived from the pressure profile generated by absorbed light energy in the sample. In a study on 20 subjects belonging to phototypes I–IV, we studied the optical properties at the volar and dorsal aspect of the forearm as well as on the thenar. Analysis of the measured absorption spectra shows that comparable skin areas—like different sides of the forearm—have qualitatively similar optical characteristics. Still, the optical properties may vary substantially within the same area, probably due to the skin structure and inhomogeneities. Comparison of the spectra from different skin sites indicates that the spectral characteristics of the stratum corneum and its chromophores play an important role for the optical properties of human skin in vivo in the ultraviolet B range. [ABSTRACT FROM AUTHOR]

The effects of raised-cosine filtering on the processing gain of acousto-optic correlators (AOC) in direct-sequence spread-spectrum receivers are considered. For ideal AOCs, analytical expressions are derived for the full roll-off filter characteristics. The results are given in terms of the ratio β of the code rate to the filter bandwidth. For real AOCs, results are obtained from numerical simulation and are compared to previous results obtained for other types of filters. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1558–1561, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23431 [ABSTRACT FROM AUTHOR]

Collinear acoustooptic (AO) switches are investigated for use in label recognition system in photonic routing systems. The optical label discussed in this paper uses optical codes which are encoded in the time domain. Short optical pulse trains representing the codes are processed with integrated AO devices. Proposed device configurations for label recognition are described with the basic operation mechanism. A numerical example for the code recognition is also presented. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 159(3): 48–55, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20453 [ABSTRACT FROM AUTHOR]

In this article, we presented a method, which will allow multiple parameter control of the 3-dB bandwidth, centre-notch wavelength, and attenuation level in a fiber-based acousto-optic tunable filter. The method basically involves the variation of the interaction length, RF frequency, and RF power on a single fiber device, to achieve multiple parameter tuning of the optical filter. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 1781–1785, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21783 [ABSTRACT FROM AUTHOR]

An acousto-optic laser deflector was used to image the intensity distribution of a continuous wave laser of microsecond order. Undeflected light was blocked while the deflected light was directed to a CCD camera, which allowed imaging of the incident laser intensity distribution of microsecond order. Experiments using a test pattern showed that there was no distortion in the deflected image. The resolution limit, estimated from diffractive effects, was about 0.2 mrad. Using this method of high-speed imaging, density variations accompanying laser-induced breakdown in air were visualized by shadowgraphy and interferometry. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 156(3): 55–61, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20386 [ABSTRACT FROM AUTHOR]

An acousto-optic laser deflector was used for visualization of high-speed phenomena, such as shock waves and density perturbations accompanying an impulse discharge, or shock waves generated by laser-induced breakdown in air. Using a continuous wave laser as the light source, shadowgraphs of shock waves and density perturbations were obtained at shutter speeds down to 1µs. Results showed that shock waves propagated at a speed of 417 m/s in the case of an impulse discharge, and 485 m/s in the case of laser-induced breakdown. Prebreakdown phenomena such as leaders progressing from the high-voltage electrode were also visualized. Compared to conventional high-speed imaging techniques, this method is useful when using a laser light source, since the acousto-optic crystal can accommodate high-intensity laser light. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 154(3): 9–15, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20279 [ABSTRACT FROM AUTHOR]

A waveguide-type collinear acoustooptic device can work as a wavelength-selective switch for wavelength division multiplexed (WDM) light. Therefore, its applications to WDM routing switching are expected. In this paper, in order to evaluate the wavelength-selective switching characteristics of the device consisting of a directional coupled waveguide and a Y-branch, simulation is carried out by the FDTD method. The results of the simulation are compared with those of the coupled mode theory, and agreement between them is confirmed. A method of propagating an optical pulse is studied in the segment-divided region in order to analyze the acoustooptical coupling characteristics in a long scale interaction region. © 2004 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 87(6): 18–27, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjb.20064 [ABSTRACT FROM AUTHOR]

Kettin is a high molecular mass protein of insect muscle associated with thin filaments and α-actinin in the Z-disc. It is thought to form a link between thin and thick filaments towards its C-terminus, contributing significantly to passive sarcomere stiffness. Here the elastic properties were characterised by mechanical stretches on an antibody-delimited region of the single molecule using two independent optical traps capable of exerting forces up to 150 pN. Step-like events were observed in the force–extension relationships consistent with the unfolding of Ig domains at moderate force and refolding of these domains at significantly higher forces than have been observed for related modular proteins. [Copyright &y& Elsevier]

In this paper, we present a study of the crosstalk level of an acousto-optic tunable filter (AOTF) operating with ultrashort light pulses (2 ps). Initially, we consider the performance of the device, with several lengths, operating in the linear and nonlinear regime without loss. Given low pump power (P0 = 1 W), the crosstalk level (XL) of this device always increases with the length of the AOTF, for three different device configurations: the soliton regime, the dispersionless regime, and the linear regime. For shorter devices (L/10 < ξL < L), the soliton regime presents the lower XL. However, this behavior is reversed for longer devices, where the filter bandwidth is much shorter than the pulse bandwidth. For the dispersionless regime and low pump power, the device with length of ξL = L/10 presents the lowest XL. As one starts increasing the pump power, the XL is increases as a consequence of the increase of the switched pulse's bandwidth. One would expect that the presence of nonlinearity leads to the broadening of the pulse bandwidth associated with the self-phase modulation and, consequently, with the increase of the XL. For high power (P0 = 9 W), the switched pulse is also presenting pulse break up. However, in the limit of high pump powers, all the devices present almost the same XL of around -1.5 dB. For the soliton regime, in all the devices there is a decrease of the XL for pump powers around 1 W, which is the energy of the fundamental soliton. For high pump powers, all devices present a second peak, where again a decrease of the XL is detected. For the ξL = L/10 device, the minimum is around 8 W. The increase of the pump power results in high-order solitons and pulse compression; in this situation, the bandwidth of the pulse increases and we can extrapolate the bandwidth of the device, the XL as increases. The study of the effect of the XL on the AOTF, operating with ultra-short optical solitons, provides possibilities for achieving high efficiency in ultrafast all-optical signal processing, especially for optical switches, filters, and optical transistors. The acoustic-optic tunable filter (AOTF) has attracted great attention in recent years, in part because it appears to be a suitable basis for multiwavelength optical cross-connects. It is probably the only known tunable filter that is capable of selecting several wavelengths simultaneously. This capability can be used to construct a multiwavelength router. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 35: 230–235, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10565 [ABSTRACT FROM AUTHOR]

This paper proposes an optical digital filter using an acousto-optic device which provides the product of the incident light intensity and the amplitude of the acoustic wave in the devices as the first-order diffraction light intensity. From the operating principle that the acoustic wave propagates inside the acousto-optic device, an arbitrary delay time due to the propagation delay of the acoustic wave can be obtained by selection of the incident location of the light. The optical addition can easily be realized by focusing the signal light on the detector. On the other hand, the digital filter can be composed of multipliers, unit delays, and an adder. The acousto-optic device is used as a multiplier and a delay line and a detector is used as an adder so that a digital filter can be made in an optical manner. In this paper, operating principles are presented for two optical digital filters using high-speed analog multiplication and high-accuracy digital multiplication. Optical FIR digital filters are made by the two methods and compared. [ABSTRACT FROM AUTHOR]

Acousto-optic deflectors arc introduced to be used as star couplers that perform broadcasting and routing in local area networks. Configurations for both single-wavelength and multiwavelength broadcast-and-select networks are proposed. A routing network in which both the input and output ports are wavelength tunable is also shown. Acousto-optic devices provide these networks with the advantage of low insertion loss, simplicity, and compactness, because one device can handle a large number of ports. Analysis for these networks is presented and computed simulation results are shown. The proposed routing network is not limited to the use of acousto-optic deflectors, because conventional blazed diffraction gratings can be used. [ABSTRACT FROM AUTHOR]

Observed anomalous acousto-optic frequency multiplication in amorphous materials is explained for the first time. Theoretical models reviewed include the nonresonant standing-wave model, the first-order modulation model, and the second-order modulation model. It is found that only the nonresonant standing-wave model provides an explanation for the observed phenomena, and not the other models. [ABSTRACT FROM AUTHOR]

A multichannel acousto-optic joint transform correlator is presented. On-plane acousto-optic (AO) cells and a square-law converter are employed. The AO cells are driven by frequency multiplexed temporal signals to produce spatially modulated signals. The joint transform power spectrum is generated with a square-law converter. By inverse Fourier transformation with a coherent readout, the cross correlation of input signals can be obtained. Since the architecture can process wideband signals, it may be applied to detect multiple frequency shift keying (MFSK) signals. [ABSTRACT FROM AUTHOR]

A time and wavelength division fiber loop distribution system with acousto-optic tunable filters is proposed. This system can provide a large number of 150 Mb/s HDTV channels with a reliable technology. A theoretical analysis by Gaussian beam approximation shows that one system can distribute 320 HDTV channels to 256 subscribers with a minimum wavelength spacing of 2 nm. An experimental 12 channel (4 time division × 3 wavelength division) system with a wavelength spacing of 20 nm in the 1.3 μm region demonstrates a data rate of 1.2 Gb's with only -4dB loss and -20 dB cross talk at the tunable filter. The experimental loss and cross talk characteristics agree well with the theoretical analysis. [ABSTRACT FROM AUTHOR]

To develop a combined endocavity ultrasound (US) and photoacoustic (PA) imaging system (ECUPSA) for evaluation blood perfusion and oxygenation in the fetus and neonates. Oxygen Saturation; We performed experiments in which blood SO SB 2 sb was altered in fresh, heparinised sheep blood by using O SB 2 sb and N SB 2 sb gas purges in a custom-built blood gas exchange chamber. The ECUSPA probe combined US and PA measurements allowing accurate evaluation of blood oxygen saturation in small vessels with a diameter of 200 µm at a depth of 39 mm. [Extracted from the article]

The high-order-mode coupling of acousto-optic modulations in a tilted fiber grating is experimentally demonstrated to be greatly enhanced due to the superposition of dual acousto-optic-modulations. The performance is based on the phase matching between two acousto-optic-modulations of different frequency in a fiber Bragg grating. The device can be applied in a switchable multiwavelength comb filter or a switchable multiwavelength fiber laser. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 46: 231–233, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20953 [ABSTRACT FROM AUTHOR]

A high-power continuous-wave (CW) laser-diode (LD) pumped acousto-optic Q-switched Nd:YVO4 laser is presented. A short pulse at 1064 nm is obtained. With a repetition rate of 50 kHz, a maximum average output power of 5.72 W is achieved. The optical-conversion efficiency and the slope efficiency are 28% and 32.4%, respectively. At the repetition rate of 10 kHz and the pulse width of 16.3 ns, the maximum single-pulse energy of 286 μJ and the peak power of 13 kW are acquired. The laser can be used as a signal source for free-space optical communication. The output signal agrees well with the modulate signal. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 42: 281–283, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20278 [ABSTRACT FROM AUTHOR]

We propose a novel optical packet synchronizer for use in telecommunication networks at a 1.5 μm wavelength. An experimental setup shows the feasibility of the system using an acousto-optic deflector and a single-mode fiber delay line array. The proposed system achieves an optical transparency to the data bit rate, and is suitable for nonregenerative application within an optical network. © 2000 John Wiley & Sons, Inc. Microwave Opt Technol Lett 26: 394–396, 2000. [ABSTRACT FROM AUTHOR]

An all-fiber antenna using piezoelectric polymer-coated circular core D-fiber has been characterized using finite-element analysis. The response of the D-fiber antenna was determined over a wide frequency range from 1 to 600 MHz. The modeling predicts an electric-field-induced phase shift of 0.00173 rad/V/m at 1 MHz. © 2000 John Wiley & Sons, Inc. Microwave Opt Technol Lett 24: 168–170, 2000. [ABSTRACT FROM AUTHOR]

Lymphatic metastasis of tumor is one of leading causes of cancer‐related death, and diagnosing lymphatic metastasis is of significance in terms of optimal disease management and possible better outcomes for patients. Herein a turn‐on optoacoustic nanoprobe is reported for noninvasively diagnosing and locating lymphatic metastasis in vivo. A positively charged tricyanofuran‐containing polyene chromophore (TCHM) with high extinction coefficient is designed, synthesized, and allowed to form the nanoprobe with a negatively charged hyaluronan. The TCHMs take an aggregated state within the nanoprobe and exhibit weak absorption at 882 nm, the overexpressed hyaluronidase in cancer cells specifically degrades hyaluronan into small fragments and disaggregates TCHMs, thereby greatly enhancing the absorption at 882 nm and generating prominent optoacoustic signals. For multispectral optoacoustic tomography (MSOT) imaging in vivo, mice models with subcutaneous tumor and orthotopic bladder tumor are imaged first to demonstrate the nanoprobe's capability for detecting HAase‐overexpressing tumors. A mouse model of lymphatic metastasis of tumor is then established and the lymphatic metastasis is successfully imaged and tracked optoacoustically. The imaging results were verified using multiple biochemical assays. Moreover, 3D MSOT renderings are obtained for precisely locating and tracking the metastasis of tumor in lymphatic system in a spatiotemporal manner. An activatable nanoprobe has been developed for noninvasively detecting lymphatic metastasis in a mouse model through multispectral optoacoustic tomography (MSOT) imaging. This probe can be used to diagnose orthotopic and metastatic tumors via responding to overexpressed hyalurodinase levels in tumors. With 3D MSOT images the metastatic route from primary tumor to sentinel lymph node via lymphatic vessel can be precisely mapped. [ABSTRACT FROM AUTHOR]

For the first time, we present results on an all-fiber acousto-optic phase modulator using aluminum nitride (AlN) piezoelectric coating. Finite-element analysis has been employed to determine the response of the modulator from 10 kHz to 600 MHz. At frequencies higher than 28 MHz, the response is dominated by radial resonances of the fiber–coating composite. © 2000 John Wiley & Sons, Inc. Microwave Opt Technol Lett 25: 124–125, 2000. [ABSTRACT FROM AUTHOR]

Purpose: Photoacoustic imaging has proven to be able to detect vascularization-driven optical absorption contrast associated with tumors. In order to detect breast tumors located a few centimeter deep in tissue, a sensitive ultrasound detector is of crucial importance for photoacoustic mammography. Further, because the expected photoacoustic frequency bandwidth (a few MHz to tens of kHz) is inversely proportional to the dimensions of light absorbing structures (0.5-10+ mm), proper choices of materials and their geometries and proper considerations in design have to be made to implement optimal photoacoustic detectors. In this study, we design and evaluate a specialized ultrasound detector for photoacoustic mammography. Methods: Based on the required detector sensitivity and its frequency response, a selection of active material and matching layers and their geometries is made leading to functional detector models. By iteration between simulation of detector performances, fabrication and experimental characterization of functional models an optimized implementation is made and evaluated. For computer simulation, we use 1D Krimholtz-Leedom-Matthaei and 3D finite-element based models. Results: The experimental results of the designed first and second functional detectors matched with the simulations. In subsequent bare piezoelectric samples the effect of lateral resonances was addressed and their influence minimized by subdicing the samples. Consequently, using simulations, a final optimized detector was designed, with a center frequency of 1 MHz and a -6 dB bandwidth of 0.4-1.25 MHz (fractional bandwidth of ∼80%). The minimum detectable pressure was measured to be 0.5 Pa. Conclusions: A single-element, large-aperture, sensitive, and broadband detector is designed and developed for photoacoustic tomography of the breast. The detector should be capable of detecting vascularized tumors with 1-2 mm resolution. The minimum detectable pressure is 0.5 Pa, which will facilitate deeper imaging compared to the current systems. Further improvements by proper electrical grounding and shielding and implementation of this design into an arrayed detector will pave the way for clinical applications of photoacoustic mammography. [ABSTRACT FROM AUTHOR]

Purpose: Optoacoustic tomography (OAT) is inherently a three-dimensional (3D) inverse problem. However, most studies of OAT image reconstruction still employ two-dimensional imaging models. One important reason is because 3D image reconstruction is computationally burdensome. The aim of this work is to accelerate existing image reconstruction algorithms for 3D OAT by use of parallel programming techniques. Methods: Parallelization strategies are proposed to accelerate a filtered backprojection (FBP) algorithm and two different pairs of projection/backprojection operations that correspond to two different numerical imaging models. The algorithms are designed to fully exploit the parallel computing power of graphics processing units (GPUs). In order to evaluate the parallelization strategies for the projection/backprojection pairs, an iterative image reconstruction algorithm is implemented. Computer simulation and experimental studies are conducted to investigate the computational efficiency and numerical accuracy of the developed algorithms. Results: The GPU implementations improve the computational efficiency by factors of 1000, 125, and 250 for the FBP algorithm and the two pairs of projection/backprojection operators, respectively. Accurate images are reconstructed by use of the FBP and iterative image reconstruction algorithms from both computer-simulated and experimental data. Conclusions: Parallelization strategies for 3D OAT image reconstruction are proposed for the first time. These GPU-based implementations significantly reduce the computational time for 3D image reconstruction, complementing our earlier work on 3D OAT iterative image reconstruction. [ABSTRACT FROM AUTHOR]

Purpose: Optoacoustic imaging relies on the detection of ultrasonic waves induced by laser pulse excitations to map optical absorption in biological tissue. A tomographic geometry employing a conventional ultrasound linear detector array for volumetric optoacoustic imaging is reported. The geometry is based on a translate-rotate scanning motion of the detector array, and capitalizes on the geometrical characteristics of the transducer assembly to provide a large solid angular detection aperture. A system for three-dimensional whole-body optoacoustic tomography of small animals is implemented. Methods: The detection geometry was tested using a 128-element linear array (5.0/7.0 MHz, Acuson L7, Siemens), moved by steps with a rotation/translation stage assembly. Translation and rotation range of 13.5 mm and 180°, respectively, were implemented. Optoacoustic emissions were induced in tissue-mimicking phantoms and ex vivo mice using a pulsed laser operating in the near-IR spectral range at 760 nm. Volumetric images were formed using a filtered backprojection algorithm. Results: The resolution of the optoacoustic tomography system was measured to be better than 130 μm in-plane and 330 μm in elevation (full width half maximum), and to be homogenous along a 15 mm diameter cross section due to the translate-rotate scanning geometry. Whole-body volumetric optoacoustic images of mice were performed ex vivo, and imaged organs and blood vessels through the intact abdominal and head regions were correlated to the mouse anatomy. Conclusions: Overall, the feasibility of three-dimensional and high-resolution whole-body optoacoustic imaging of small animal using a conventional linear array was demonstrated. Furthermore, the scanning geometry may be used for other linear arrays and is therefore expected to be of great interest for optoacoustic tomography at macroscopic and mesoscopic scale. Specifically, conventional detector arrays with higher central frequencies may be investigated. [ABSTRACT FROM AUTHOR]