Search

It is still a high challenge to develop a simple, sensitive and portable approach for bioassay in strong scattering medium. Herein, a photoacoustic (PA) device is developed for the detection of alkaline phosphatase (ALP) in serum with silver nanoparticles (AgNPs) as signal probe, without any requirements for expensive equipment, professional operation and pre-processing of real samples. ALP as an important disease marker could catalyze the breakdown of sodium L-ascorbyl-2-phosphate (AAP) into ascorbic acid (AA), thereby reducing Ag+ to AgNPs. AgNPs could generate strong PA signal under the irradiation of modulated 638-nm laser due to their localized plasmon resonance, and detected by the self-made portable PA device. Under the optimized experimental conditions, the present PA device exhibits excellent photostability and reproducibility with the relative standard deviation (RSD) of 2.2% at the concentration of 25 U L−1 ALP. Linear calibration graph is obtained within 5–70 U L−1 for ALP, along with a detection limit of 1.1 U L−1. This portable PA device is applied to detect ALP in serum samples, providing satisfactory spiking recoveries and competitive analytical performances with the current techniques. The PA-based analytical strategy obviously opens up a new avenue to the detection of disease-correlated biomarker in practice. A portable photoacoustic device is developed for the detection of alkaline phosphatase in serum with silver nanoparticles as signal probe. Image 1 • A portable photoacoustic device is developed for the determination of alkaline phosphatase in serum. • Silver nanoparticles as photoacoustic probe exhibit excellent photostability and reproducibility. • This portable device is free from expensive equipment, professional operation and pre-processing of real samples. [ABSTRACT FROM AUTHOR]

Abstract Near-infrared (NIR) absorbing dyes have been attached much importance recently, since the promising prospect in photoacoustic (PA) imaging and photothermal (PT) therapy in cancer treatment. In this work, PA signal and PT effect of pyrene derivatives (C12 and C13) prepared via click reaction were evaluated, systematically. It was studied about the further application of loading the representative trisubstituted pyrene derivative (C13) into biocompatible liposomes and subsequent PA measurement. C13 showed the excellent PA effect, whether it's embedded or not. Since temperature increment of the dyes were remarkable in PT test, the same representative derivative C13 was picked and loaded into PNIPAM-b-PNBM polymer micelles as photothermal conversion agent. Preliminary studies suggested that the trisubstituted pyrene derivatives had great potential to replace the function of temperature stimulus. Graphical abstract Image 1 Highlights • A series of near-infrared dyes based on pyrene derivatives show the excellent PA and PT effect. • Representative pyrene derivative was loaded into biocompatible liposomes and micelles with multiple responses. • Representative pyrene derivative effectively may controllably promote the diffusion rate of Nile Red under NIR irradiation. [ABSTRACT FROM AUTHOR]

Highlights • A photoacoustic and fluorescence dual-mode probe for LTA 4 H sensing was developed. • Cy-ASP has high selectivity and high sensitivity toward LTA 4 H. • Combined with PA technology, Cy-ASP could image the activity of LTA 4 H in mice without dissection. • The probe Cy-ASP could fast locate the inflammation site in mice. Abstract Inflammation widely occurs in various tissues and organs in the human body. Rapid and accurate diagnosis of inflammation is essential to avoid severe complications. This study aims to obtain a non-destructive, fast, and comprehensive tool for the detection of pathogenic sites of inflammation in vivo. A fluorescence and photoacoustic dual-mode imaging probe, Cy-ASP, was first developed to detect inflammatory biomarker LTA 4 H with good sensitivity and selectivity in living small animal. Furthermore, the relationship between LTA 4 H and NF-κB in an LPS-induced cell was investigated. This work provides a new idea for the clinical diagnosis of pneumonia and hepatitis and revealing the upstream regulatory mechanism of LTA 4 H in the pneumonia model. [ABSTRACT FROM AUTHOR]

A diode-pumped acousto-optically (AO) Q-switched 1066 nm laser with a novel Nd:GdTaO 4 crystal was demonstrated for the first time to the best of our knowledge. The optimization selection of output coupler was carried out in the continuous-wave (CW) operation. After that the pulsed Nd:GdTaO 4 laser performances using different modulation repetition rates of 10 kHz and 20 kHz were investigated. At an absorbed pump power of 10 W and repetition rates of 10 kHz, the obtained minimum pulse width was 28 ns and the maximum peak power was 5.4 kW. [ABSTRACT FROM AUTHOR]

Anisotropic piezoelectric superlattices (APSs) with the periodic arrangement of polarized anisotropic piezoelectric domains in a certain direction are presented, in which the coupled polaritonic band gaps (CPBGs) can be obtained in the whole Brillouin Zone and the maximum relative bandwidth (band-gap sizes divided by their midgap frequencies) of 5.1 % can be achieved. The general characteristics of the APSs are similar to those of the phononic crystals composed of two types of materials, with the main difference being the formation mechanism of the CPBGs, which originate from the couplings between lattice vibrations along two different directions and electromagnetic waves rather than from the periodical modulation of density and elastic constants. In addition, there are no lattice mismatches because the APSs are made of the same material. Thus, the APSs can also be extended to the construction of novel acousto-optic devices. [ABSTRACT FROM AUTHOR]

In this work, thermal characterization of centrifuged aromatic citrus oils was studied using thermal lens (TL) and open photoacoustic cell (OPC). The thermal diffusivity ( D ) was obtained by TL, fitting the critical time parameter of the experimental curves to the theoretical values. An experimental arrangement of non-matched mode lasers with a probe and an excitation lasers was used. On the other hand, the thermal effusivity ( e ) of the samples was obtained by using OPC. The thermal conductivity ( k ) was calculated from the relationship between D and e . The thermal parameters obtained were compared with theoretical values ​​in the literature. UV–vis spectroscopy, Attenuated Total Reflectance-Fourier Transform Infrared spectroscopy (ATR-FTIR) and 1 H Nuclear Magnetic Resonance (NMR) were used to determine the absorption coefficients and chemical structure of the citrus oils. The importance of this research work was the determination of the thermal parameters of essential oils as an alternative technique for quality control application. [ABSTRACT FROM AUTHOR]

Smog chamber experiments were conducted to study the changes of the physical properties and chemical composition of biomass burning particles as they evolve in the atmosphere. A Soot Particle Aerosol Mass Spectrometer (SP-AMS) and a Single Particle Soot Photometer (SP2) were used for the chemical characterization of the particles. An Aethalometer and a green and a blue photoacoustic extinctiometer (PAX) were used for the study of the aerosol optical properties. As smoke aged, exposed to UV light, ozone or OH radicals, organic material condensed on the preexisting particles. This coating led to an increase of the absorption of the black carbon-containing particles by as much as a factor of two. The absorption enhancement of biomass burning particles due to their coating with aromatic secondary organic aerosol (SOA) was also studied. The resulting absorption enhancement was determined mainly by the changes in the SOA mass concentration and not the changes of its oxygen to carbon ratio. The measured absorption enhancements were consistent with the predictions of Mie theory assuming core-shell morphology for the aged particles. [ABSTRACT FROM AUTHOR]

We present the development and the characterization of a photoacoustic NO 2 trace gas detection system. The system is based on the implementation of low-cost components, i.e. a mass-produced blue diode laser and a standard MEMS microphone which is commonly built into smartphones, for example. An optimized cell design was realized by means of 3D printing. The linearity of the photoacoustic signal dependency on the analyte concentration was verified from 200 ppbV to 100 ppmV NO 2 . The detection limit (1σ) was determined to 33 pptV and the normalized noise equivalent absorption coefficient was calculated to 7.0 ∙ 10 −10 W cm −1 Hz −1/2 . The dynamic range of the system was verified to be linear over three magnitudes of order and the sensitivity was calculated to 814 μV/ppmV. The system was characterized in view of optimal operating parameters, i.e. lock-in time constant τ LIA and total mass flow rate, optical performance and signal stability. The mass flow dependend response time of the system was specified to 19 s and an idealized step response to a quasi -Heaviside step function was quantified as a function of τ LIA . The quality factor of acoustic resonance was determined to 21.9 and an empirical expression regarding acoustic node shifting is provided. The expression takes into account the radius of the resonator pipe and the radius of the hole, which was drilled into the pipe for microphone coupling. Furthermore, we studied the cross-sensitivity of the photoacoustic signal towards H 2 O and CO 2 , respectively. [ABSTRACT FROM AUTHOR]

Organometallic carbonyl clusters (OMCC) of group VIII elements are water soluble, bio-compatible and stable high-contrast photoacoustic agents for live cell imaging. But, they have limited application due to weak absorption within 700–1000 nm wavelength which is known as the biological window of absorption. In this article, we report that hexa-nuclear iron (Fe 6 ) carbonyl cluster derivatized with sodium thio-propanoate has very good absorption within 700–1600 nm wave length. This modeled compound is water soluble and bio-compatible. The bio-compatibility of this compound is tested through cytotoxicity, Log P and metabolic probability at CYP450-2D6 enzyme. [ABSTRACT FROM AUTHOR]

An ultrasonic probe consisting of two optical fiber-based miniaturized transducers for wideband ultrasound emission and detection is employed for the characterization of in vitro biological tissues. In the probe, ultrasound generation is obtained by thermoelastic emission from patterned carbon films in Micro-Opto-Mechanical-System (MOMS) devices mounted on the tip of an optical fiber, whereas acousto-optical detection is performed in a similar way by a miniaturized polymeric interferometer. The microprobe presents a wide, flat bandwidth that is a very attractive feature for ultrasonic investigation, especially for tissue characterization. Thanks to the very high ultrasonic frequencies obtained, the probe is able to reveal different details of the object under investigation by analyzing the ultrasonic signal within different frequencies ranges, as shown by specific experiments performed on a patterned cornstarch flour sample in vitro. This is confirmed by measurements executed to determine the lateral resolution of the microprobe at different frequencies of about 70 μm at 120 MHz. Moreover, measurements performed with the wideband probe in pulsed-echo mode on a histological finding of porcine kidney are presented, on which two different spectral signal processing algorithms are applied. After processing, the ultrasonic spectral features show a peculiar spatial distribution on the sample, which is expected to depend on different ultrasonic backscattering properties of the analyzed tissues. [ABSTRACT FROM AUTHOR]

Thallium bromide iodide crystal also known as KRS-5 is the well known material used in far infrared radiation applications for optical windows and lenses fabrication. The main advantage of this material is the transparency in wide band of wavelengths from 0.53 to 50 μm. Despite such advantages as transparency and large acousto-optic figure of merit values, KRS-5 is rarely used in acousto-optics. Nevertheless this material seems to be promising for far infrared acousto-optic applications. The acoustic and acousto-optic properties of KRS-5 needed for the full use in optoelectronics are not well understood to date. In this paper the detailed examination of thallium bromide iodide crystal acoustic properties is presented. [ABSTRACT FROM AUTHOR]

Diode-laser pumped Q-switched Nd 3+ -doped vanadate lasers at 0.91 μm and intracavity frequency-doubling of 0.45 μm blue light emissions are studied. Using a compact V-type laser cavity and a miniature acousto-optically (AO) Q-switch, the highest average output powers of 2.2 W 0.912 μm Nd:GdVO 4 laser and 1.59 W 0.914 μm Nd:YVO 4 laser are obtained at repetition rate of 10 kHz, with the optical conversion efficiency of 7.4% and 5.3%, and the slope efficiency of 14.8% and 9.5%. Employing a BiBO crystal as frequency-doubler, 1.3 W, 37 ns 0.456 μm and 0.84W, 37.4 ns 0.457 μm pulsed blue light are emitted at 10 kHz, corresponding to the peak power of 3.51 kW and 2.25 kW, respectively. In addition, stable operation is up to 100 kHz. [ABSTRACT FROM AUTHOR]

A novel numerical study based on the finite element method is developed to demonstrate the beatlengths induced by high frequency acoustic modes inside an optical fiber for the first time. A practical methodology to model, compute and analyze the multimode interaction in the fiber is exemplified with a detailed numerical experiment. The frequency response of 1 mm long standard fiber is evaluated from 30 to 60 MHz, corresponding to the highest attenuation band of experimental fiber optoacoustic devices. The 3D simulated complex ultrasonic fields are decomposed and characterized with the averaged peak-to-peak method and 2D Fourier transform. The resulting dispersion spectra are compared and theoretically validated by the recognized Pochhammer-Chree solutions. The acoustic parameters required to modulate optical fibers are derived from the simulations and discussed. A route to overcome the frequency-induced limitations of the current devices is provided, pointing out new research possibilities for the development of highly efficient and compact all-fiber acousto-optic modulators and fiber-optic ultrasonic sensors. • First study of beatlengths induced by acoustic modes interacting in an optical fiber. • 3D design, modeling, and analysis of high frequency ultrasound with finite elements. • 2D spectral analysis of complex modal interference and dispersion inside the fiber. • Simulated beatlength-tunable acoustic gratings strengthen in-core interaction. • High efficiency for all-fiber acousto-optic modulators and optoacoustic sensors. [ABSTRACT FROM AUTHOR]

Single crystals of mercurous halide were grown by physical vapor transport method (PVT). The orientation and the crystalline quality of the grown crystals were determined using high resolution x-ray diffraction (HRXRD) technique. The full width at half maximum (FWHM) of the grown mercurous bromide crystals was measured to be 0.13 degrees for (004) reflection, which is the best that has been achieved so far for PVT grown mercurous halide single crystals. The extended defects of the crystals were also analyzed using high resolution x-ray diffraction topography. Preliminary studies were carried out to evaluate the performance of the crystals on acousto-optic modulator (AOM) and gamma-ray detector applications. The results indicate the grown mercurous halide crystals are excellent materials for acousto-optic modulator device fabrication. The diffraction efficiencies of the fabricated AOM device with 1152 and 1523 nm wavelength lasers polarizing parallel to the acoustic wave were found to be 35% and 28%, respectively. The results also indicate the grown crystals are a promising material for gamma-ray detector application with a very high energy resolution of 1.86% FWHM. [ABSTRACT FROM AUTHOR]

Significant part of acousto-optic devices apply the acoustic beam reflection to arouse the desired type of acoustic mode propagating along the required direction in crystal. The influence of acoustic beam reflection process on the ultrasound field structure in the acousto-optic cell and the collinear acousto-optic diffraction characteristics is examined in this paper. The investigation is carried on the example of the collinear acousto-optic filter fabricated on the base of calcium molybdate crystal. It is shown that the reflection process changes the acoustic field structure and affects the acousto-optic filter transmission function shape and diffraction efficiency. [ABSTRACT FROM AUTHOR]

Mosquito flight tones occur during locomotion and courtship and are mostly analyzed using microphones. The use of microphones is impractical for analyzing the wingbeat of non-tethered insects especially if one is interested in studying the frequency content of wingbeats of a large number of insects. In this study we present a practical setting based on a novel 2D optical sensor that we embed inside insectary cages to record the wingbeats of three mosquito species belonging to three different genera, namely Culex pipiens molestus , Anopheles gambiae and Aedes albopictus . We show that this setting allows to automatically create distributions of parameters related to wingbeat frequency and harmonic properties derived from many non-tethered wingbeats and therefore characterize the wingbeat properties of a whole species with increased confidence. Implications for potential applications are discussed. [ABSTRACT FROM AUTHOR]

This paper concerns the problem of platform vibration induced band-to-band misregistration with acousto-optic imaging spectrometer in spaceborne application. Registrating images of different bands formed at different time or different position is difficult, especially for hyperspectral images form acousto-optic tunable filter (AOTF) imaging spectrometer. In this study, a motion detection method is presented using the polychromatic undiffracted beam of AOTF. The factors affecting motion detect accuracy are analyzed theoretically, and calculations show that optical distortion is an easily overlooked factor to achieve accurate band-to-band registration. Hence, a reflective dual-path optical system has been proposed for the first time, with reduction of distortion and chromatic aberration, indicating the potential of higher registration accuracy. Consequently, a spectra restoration experiment using additional motion detect channel is presented for the first time, which shows the accurate spectral image registration capability of this technique. [ABSTRACT FROM AUTHOR]

Pathogen analysis in food samples routinely involves lengthy growth-based pre-enrichment and selective enrichment of food matrices to increase the ratio of pathogen to background flora. Similarly, for blood culture analysis, pathogens must be isolated and enriched from a large excess of blood cells to allow further analysis. Conventional techniques of centrifugation and filtration are cumbersome, suffer from low sample throughput, are not readily amenable to automation and carry a risk of damaging biological samples. We report on-chip acoustophoresis as a pre-analytical technique for the resolution of total microbial flora from food and blood samples. The resulting ‘clarified’ sample is expected to increase the performance of downstream systems for the specific detection of the pathogens. A microfluidic chip with three inlets, a central separation channel and three outlets was utilized. Samples were introduced through the side inlets, and buffer solution through the central inlet. Upon ultrasound actuation, large debris particles (10–100 μm) from meat samples were continuously partitioned into the central buffer channel, leaving the ‘clarified’ outer sample streams containing both, the pathogenic cells and the background flora (ca. 1 μm) to be collected over a 30 min operation cycle before further analysis. The system was successfully tested with Salmonella typhimurium -spiked (ca. 10 3 CFU mL − 1 ) samples of chicken and minced beef, demonstrating a high level of the pathogen recovery (60–90%). When applied to S. typhimurium contaminated blood samples (10 7 CFU mL − 1 ), acoustophoresis resulted in a high depletion (99.8%) of the red blood cells (RBC) which partitioned in the buffer stream, whilst sufficient numbers of the viable S. typhimurium remained in the outer channels for further analysis. These results indicate that the technology may provide a generic approach for pre-analytical sample preparation prior to integrated and automated downstream detection of bacterial pathogens. [ABSTRACT FROM AUTHOR]

A miniaturized photoacoustic spectroscopic gas sensor for room climate monitoring is presented with the measurement range of 0 –5000 ppm. The sensor consists of an innovative photoacoustic detection unit with an integrated mobile phone microphone as pressure sensor. As IR-source a broadband thermal emitter is used. The emitter is modulated with 13 Hz at a maximum temperature of about 750 °C. An electronic unit with a microcontroller on a 3D-PCB design has been developed. The sensor reaches a resolution better than 50 ppm CO 2 . A detailed characterization of the setup has been carried out. An integrated temperature compensation is realized to improve the sensor performance under varying environmental conditions. The potential for further miniaturization and the realization as a low-cost mass market sensor is shown. [ABSTRACT FROM AUTHOR]

In this paper, the design and development of a device for thermal diffusivity measurement of fluids exploiting the photoacoustic effect is presented. Compared to similar devices working only at room temperature, the version of the apparatus we present allows precise measurements of thermal diffusivity of fluids from room temperature to 70 °C. The reliability of the measurements is shown by the estimation of thermal diffusivity of well-known test liquids. The possibility to detect slight thermal diffusivity variations (around 1%) is verified by measurements on alumina based water nanofluids showing remarkable advantages in respect to alternative techniques. [ABSTRACT FROM AUTHOR]

Photoacoustic tomography (PAT) is an effective optical biomedical imaging method characterized with non-ionizing and noninvasive, presenting good soft tissue contrast and excellent spatial resolution. To build a full-view photoacoustic (PA) image, numbers of ultrasound sensors are needed to assure the image quality, which will bring difficulties to data acquisition and real-time image display. Compressed sensing (CS) theory breaks the restriction of Nyquist sampling theorem and is capable to rebuild signals with less measurements. In this contribution, we proposed an optimization method to increase image quality of full-view PAT with less ultrasound sensors, which combines the theory of CS and a circularly distributing asymmetric data acquisition frame. The hardware cost can be saved and time efficiency of PAT can be raised without sacrificing the image quality. The feasibility of our proposed method is verified in simulation experiments which yield expected results. Our study might be helpful for clinical medical imaging such as early stage breast cancer detection, endoscopic imaging and in vivo monitoring. [ABSTRACT FROM AUTHOR]

A non-critically phase matched eye-safe KTA optical parametric oscillator intracavity pumped by a dual-wavelength acousto-optically Q-switched Nd:GYSGG laser is demonstrated. Simultaneous dual signal wavelength at 1525.1 nm/1531.2 nm can be realized using only one laser crystal and one nonlinear crystal. When the absorbed diode pump power at 808 nm is 7.48 W, the maximum output power, single pulse energy and peak power are 296 mW, 2.96 μJ and 6.4 kW, respectively. As the signal wavelengths exactly locates at the absorption band of C 2 H 2 , such an Nd:GYSGG/KTA eye-safe laser has good application prospects in differential absorption lidar (DIAL) for C 2 H 2 detection and difference frequency generation for terahertz waves at 0.77 THz. [ABSTRACT FROM AUTHOR]

Temperature dependent acoustic phonon behavior of PbWO 4 and BaWO 4 using Brillouin spectroscopy has been explained for the first time. Low temperature Brillouin studies on PbWO 4 and BaWO 4 have been carried out from 320–20 K. In PbWO 4 , we observe a change in acoustic phonon mode behavior around 180 K. But in the case of BaWO 4 , we have observed two types of change in acoustic phonon mode behavior at 240 K and 130 K. The change in Brillouin shift ω and the slope d ω /d T are the order parameter for all kinds of phase transitions. Since we do not see hysteresis on acoustic phonon mode behavior in the reverse temperature experiments, these second order phase transitions are not related to structural phase change and could be related to acoustic phonon coupled electronic transitions. In PbWO 4, the temperature driven phase transition at 180 K could be due to changes in the environment around the lead vacancy (V Pb 2− ) changes the electronic states. In the case of BaWO 4 , the phase transition at 240 K shows the decrease in penetration depth of WO 3 impurity. So it becomes more metallic. The transition at 130 K could be the same electronic transitions as that of PbWO 4 as function of temperature. The sound velocity and elastic moduli of BaWO 4 shows that it could be the prominent material for acousto-optic device applications. [ABSTRACT FROM AUTHOR]

Abstract: Multispectral optoacoustic tomography enhances the performance of single-wavelength imaging in terms of sensitivity and selectivity in the measurement of the biodistribution of specific chromophores, thus enabling functional and molecular imaging applications. Spectral unmixing algorithms are used to decompose multi-spectral optoacoustic data into a set of images representing distribution of each individual chromophoric component while the particular algorithm employed determines the sensitivity and speed of data visualization. Here we suggest using vertex component analysis (VCA), a method with demonstrated good performance in hyperspectral imaging, as a fast blind unmixing algorithm for multispectral optoacoustic tomography. The performance of the method is subsequently compared with a previously reported blind unmixing procedure in optoacoustic tomography based on a combination of principal component analysis (PCA) and independent component analysis (ICA). As in most practical cases the absorption spectrum of the imaged chromophores and contrast agents are known or can be determined using e.g. a spectrophotometer, we further investigate the so-called semi-blind approach, in which the a priori known spectral profiles are included in a modified version of the algorithm termed constrained VCA. The performance of this approach is also analysed in numerical simulations and experimental measurements. It has been determined that, while the standard version of the VCA algorithm can attain similar sensitivity to the PCA–ICA approach and have a robust and faster performance, using the a priori measured spectral information within the constrained VCA does not generally render improvements in detection sensitivity in experimental optoacoustic measurements. [Copyright &y& Elsevier]

Abstract: Phoxonic crystal is a promising artificial periodic material for optomechanical systems and acousto-optical devices. In this paper, two-dimensional phoxonic crystals with veins in square, triangle and honeycomb lattices are investigated. Detailed discussion is presented on the variation of the photonic and phononic bandgaps with the geometry and lattice form of the structure. The results show that simultaneous large complete photonic and phononic bandgaps can exist over a wide range of geometry parameters for the square and honeycomb lattices. These large regions offer good tolerance for the technological realization and flexibility in designing this phoxonic crystal structure. [Copyright &y& Elsevier]

Abstract: Three-mode opto-acoustic interactions can excite acoustic modes of the mirrors of an optical cavity. This was achieved when the frequency difference between the fundamental and higher order optical mode matches the frequency of appropriate acoustic mode of the mirror. The excitation also critically depends on the spatial overlap between acoustic and optical modes. In this Letter, we use a controlled CO2 laser to thermally change the radius of curvature of one mirror of an 80 m Fabry–Pérot cavity for three-mode interaction. Several acoustic modes of the cavity end mirror were observed with quality factors of at the thermal noise level. [Copyright &y& Elsevier]

• The PA signals intensity is associated with the convex lens (CL) focal length. • The PA signals is associated with the distance between the optical devices. • The PA signals intensity weakens with the increased focal length. • The effect of the distance between the CL and laser head could be ignored. • Provide a reference for the convex lens selection and the optical devices positions. [Display omitted] Photoacoustic (PA) spectroscopy has been extensively applied in gas detection field due to its high sensitivity. However, the stability and repeatability are unsatisfactory in some cases. Herein, it is proposed that the PA signals intensity is associated with the focal length F of the convex lens (CL), the distance l 1 between the CL and the window of the PA cell, and the distance l 2 between the CL and the laser head. Then, the experimental setup was constructed with a distributed feedback semiconductor laser (DFB LD) as the light source, and a cylindrical cavity with its length and diameter are 95 mm and 6 mm, respectively, as the PA cell. And the influence of the above three factors on the PA signals has been analyzed. The results show that the strongest PA signals can be obtained when the F , l 1 , and l 2 are 20 mm, 0 mm and 9 mm, respectively. Additionally, l 1 and l 2 both have an impact on the PA signals and the influence of l 2 seems to be more regular and can be approximately ignored except when F is 20 mm. Especially, the PA signals weaken with the increase of the F , but the l 1 and l 2 have the least effect on the PA signals intensity when the focal length is 50 mm and 63 mm based on the calculation of variance. The results provide a reference for the selection of convex lens and the optical devices positions to improve the stability and sensitivity of the PAS gas detection device. [ABSTRACT FROM AUTHOR]

Highlights: [•] A miniature analog of resonant banana-shaped photoacoustic cell is represented. [•] We study frequency dependence of noise-associated measurement error for the analog. [•] We study frequency dependence of background and useful signals for the analog. [•] We estimate gas-detection performance for the analog. [•] Despite low gas-sensing performance, the analog is a good tool of gas-leak sensing. [ABSTRACT FROM AUTHOR]

Abstract: Silicon cantilever sensors have been designed, fabricated and tested in acoustic wave detection. The principal application of the components is photoacoustic spectroscopy (PAS) which is a highly sensitive method in solid, liquid and gas analysis. The developed microfabrication process of the sensors is based on silicon-on-insulator (SOI) wafer etching, in which the challenge is to control and minimize the residual stress related curving in thin (5μm) but large-area (few mm2) components. The sensitivity of the fabricated cantilevers is investigated in photoacoustic measurements of solid samples, and the signal strength is shown to increase tens of percent compared with the results obtained with previously reported cantilever microphones. Improvement of the signal-to-noise ratio (SNR) verifies the advantage of the presented cantilevers in photoacoustic sensing. [Copyright &y& Elsevier]

Abstract: In the paper, bandwidth parameters of acousto-optical deflectors (AODs) are analyzed from the point of view of acoustical anisotropy. Equations for bandwidth and central frequency of AOD are derived for arbitrary propagation direction of ultrasound in optically uniaxial crystals. The phenomenon of bandwidth shift due to phase mismatch at the central frequency is studied theoretically and verified experimentally. [Copyright &y& Elsevier]

Abstract: We have demonstrated a compact Q-switched Nd:YAG laser at 1064nm with 885nm diode-laser (LD) direct pumping. At a repetition rate of 100kHz, an average output power of 53W with beam quality factor M 2 of 1.6 was achieved under the absorbed pump power of 122W, corresponding to an optical–optical efficiency of 43.5% and a slope efficiency of 57.6%, respectively. The pulse width and the peak power at this output power were 112ns and 4.74kW, respectively. [Copyright &y& Elsevier]

Abstract: ZBLAN fiber has been vastly investigated over the past decades since it has a broad wavelength transparent region. Therefore, to use it at its maximum potential in multiple applications such as in fiber lasers, amplifiers, laser cooling or infrared super continuum generation, it is important to know its intrinsic material properties. We have investigated stimulated Brillouin scattering in a single mode ZBLAN fiber, we believe for the first time, for crucial information on acousto-optic properties. A frequency shift of 7.76GHz from the pump is observed and the Brillouin gain bandwidth is measured to be 38MHz. We compared this data to a standard SMF-28 fiber and bulk ZBLAN. We calculate fundamental properties in the fiber such as phonon lifetime, attenuation and longitudinal velocity, the electrostrictive constant, the longitudinal elasto-optic Pockels coefficient and the maximum Brillouin gain constant. [Copyright &y& Elsevier]

Abstract: The thermal conductivity (K), thermal diffusivity (α), and specific heat capacity (ρc) for a glass prepared from JSC-1A lunar soil simulant were measured using a combination of open photoacoustic cell (OPC) and thermal relaxation techniques. The values of K and α for the JSC-1A glass were (20±3) mW/cmK and (14±2) cm2/s, respectively, and are somewhat larger than those of the comparable silicate glasses. The specific heat capacity (ρc) for this glass was (1.44±0.07) J/cm3K, which is a little smaller than the comparable silicate glasses. Materials with high values of K and α rapidly adjust their temperature with that of their surrounding atmosphere, making them more resistant to mechanical failure occurring due to thermal shock. [Copyright &y& Elsevier]

Abstract: Nanofluid is considered a suitable way for enhancing the heat transfer performance of conventional fluids. In this article photoacoustic technique as a nonintrusive optical method has been used to measure thermophysical properties (diffusivity, effusivity and conductivity) of transparent nanofluids. TiO2 (≈20nm) and Al2O3 (3–7nm) nanoparticles have been prepared and utilized to prepare nanofluids at low volume concentration (0.1–1vol.%). The prepared nanoparticles were characterized by using X-ray diffraction and TEM. The base fluid was dilute solution of dye crystal violet as a light absorber of known extinction coefficient in deionized water. The measured thermal parameters of the base fluid do not significantly differ from that of deionized water. The results show that thermal parameters of both nanofluids increase as the particle concentrations increase and are higher than the values of the base liquid for all concentrations of TiO2 nanoparticles. Also despite thermal conductivity of bulk Al2O3 is larger than that of TiO2, thermal parameters of Al2O3 nanofluids are generally less than those of TiO2 nanofluids. This contradictory can be explained on the bases of particle size effect. Furthermore, using Hashin and Shtrikman lower bound we were able to estimate an order of magnitude reduction of thermal conductivity of Al2O3 nanoparticles relative to its bulk value. [Copyright &y& Elsevier]

Abstract: An integrative fast (Photoacoustic) PA imaging system based on multi-element linear ultrasonic transducer array was developed, which integrates laser delivery, photoacoustic excitation and photoacoustic detection into a portable system. It collects PA signals by a multi-element linear transducer array in a reflection mode. The PA images with high spatial resolution and high contrast were obtained. Compared to other existing PA imaging methods, the integrative PA imaging system is characterized by rapidness, convenience and high practicality. The integrative system is mobile and portable, and it is suitable for imaging samples in natural condition with various different shapes. It will provide a novel and effective PA imaging approach for clinic diagnosis of neoplasm and tissue functional imaging in vivo, and has potential to be developed into a practical apparatus used in the early non-invasive detection of breast-cancer. [Copyright &y& Elsevier]

Abstract: In order to approve the direction property of multi-element linear ultrasonic transducer array, the multi-element phase-controlled technique was adopted. Here we have explored the detected direction influence from dominant frequency, number of multi-element transducer and space between transducer on direction of multi-element linearultrasonic transducer array. These results show that large sub-array has good direction property when the main frequency of detector is low. However it is contrary for high frequency of ultrasonic detector. This will be significative in photoacoustic signal detection and image reconstruction. [Copyright &y& Elsevier]

Abstract: Thermal effects greatly influence the optical properties of the acousto-optic deflectors (AODs). Thermal analysis plays an important role in modern AOD design. However, the lack of an effective method of analysis limits the prediction in the thermal performance. In this paper, we propose a finite element analysis model to analyze the thermal effects of a TeO2-based AOD. Both transducer heating and acoustic absorption are considered as thermal sources. The anisotropy of sound propagation is taken into account for determining the acoustic absorption. Based on this model, a transient thermal analysis is employed using ANSYS software. The spatial temperature distributions in the crystal and the temperature changes over time are acquired. The simulation results are validated by experimental results. The effect of heat source and heat convection on temperature distribution is discussed. This numerical model and analytical method of thermal analysis would be helpful in the thermal design and practical applications of AODs. [Copyright &y& Elsevier]

Abstract: SPICAV IR, a part of SPICAV/SOIR suite on Venus Express, is a compact single pixel spectrometer for the spectral range of 0.65–1.7μm based on acousto-optical tunable filter (AOTF) technology. SPICAV IR is derived from SPICAM IR operating on Mars Express, the first AOTF spectrometer in the deep space, and adapted for Venus atmosphere measurements. The spectrometer sequentially measures spectra of reflected solar radiation from Venus on the dayside and the emitted Venus radiation in spectral “windows” on the nightside, and works also in solar occultation mode. The spectral range is 0.65–1.1μm with spectral resolution of 7.8cm−1, and 1–1.7μm with spectral resolution of 5.2cm−1. A description of this near-IR instrument, its calibration, in-flight performances, and the modes of operations on Venus’ orbit are presented. A brief overview of the science measurements is given: water vapor measurements in the mesosphere on the day-side and near surface on the nightside, mapping of the O2(a 1 Δ g ) emission at 1.27μm, aerosol studies via polarization and scattering solar radiation at the day-side, and measurements of aerosol properties at the tops of the clouds in solar occultations. [Copyright &y& Elsevier]

Abstract: The growth of high quality TeO2 single crystals for acousto-optic devices usually requires a starting powder of relatively high purity (99.995% or better). In addition to foreign metallic impurities, even minute amounts of excess Te precipitating in TeO2 can play a role in the crystal growth behavior and in the resulting properties of the crystal. In this paper, two different approaches for the synthesis of high quality TeO2 starting material have been tested, both using 99.9995% Te as precursor. In the first case, basically a high temperature oxidation process, fine Te powder was subjected to a multi-stage oxidizing process occurring either in vapor or solid phase. In the second case, a hydro-metallurgical method, Te powder was dissolved in nitric acid and then precipitated in form of TeO2. The purity was measured by glow discharge mass spectroscopy and the tellurium fraction in TeO2 was determined by measuring the absorption at 442nm of the gas phase in equilibrium with a solid sample. This technique, used for the first time to measure free Te in TeO2, has proven to apply to this system, leading to good sensitivity and good repeatability. While high temperature oxidation (vapor phase oxidation or solid state diffusion) of 99.9995% Te powder allowed for preserving the purity of the material, the incorporation of impurities was observed when the TeO2 was synthesized through a wet chemical process, leading to a 99.999% purity. This last technique, however, offered the lowest deviation from stoichiometry. [Copyright &y& Elsevier]

Abstract: An extension of the rate equation models for solid-state Raman laser is proposed and investigated with accounting for the dynamics of an acousto-optically (AO) Q-switch modulator and the effects of thermal lens provided by the pump beam. The improved model is aimed at outlining optimization strategies for wonderful laser performance with short pulse width and high peak power. A comparison between traditional intra-cavity and new couple-cavity configurations is made. The simulation results indicate that it is possible to realize an efficient sub-nanosecond coupled-cavity Raman laser by optimizing several important parameters. [Copyright &y& Elsevier]

Abstract: The efficiency of acoustooptic interaction in single-mode strip silica waveguide is analyzed theoretically for the first time by determining the overlap integral between the optical and acoustic field distributions. The results show that there is a good overlap of the optical and SAW fields in the low SAW frequency range. At high acoustic frequencies, the overlap integral decreases with increasing acoustic frequency. At 216MHz, the maximum of 0.8544 for the overlap integral is obtained provided that the H/Λ equals 0.02. [Copyright &y& Elsevier]

Abstract: Due to the long optical wavelengths of the mid-infrared region and to the low acoustic shear wave velocities of mercury halides, the high acoustic frequency solution of the acousto-optic wave-vector diagram can be used to design new high resolution acousto-optic filters, such as reflective AOTFs and AOPDFs, which are technically impossible to realize in the UV, visible and near-infrared regions. [Copyright &y& Elsevier]

Abstract: To establish the methodical basis for the development and certification of fluorescence quantum yield standards, we determined the fluorescence quantum yield Φ f of rhodamine 6G (R6G) with two absolute methods with complementary measurement principles, here optical spectroscopy using an integrating sphere setup and pulsed laser photoacoustic spectroscopy (PAS). For the assessment of aggregation- and reabsorption-induced distortions of measured fluorescence quantum yields and procedures for the reliable consideration of such effects, this systematic comparison was performed in ethanol and in water employing different concentrations of R6G. In addition, the relative and absolute fluorescence quantum yields of these solutions were obtained with a calibrated spectrofluorometer and a commercialized integrating sphere setup. Based upon this systematic comparison, experimental advantages and systematic sources of variation were identified for both methods. [Copyright &y& Elsevier]

Abstract: A compacted size high power CO2 laser has been developed using an acousto-optically (AO) Q-switch. Performance characteristics have been investigated as a function of output mirror transmittance. The theory of six-temperature model for CO2 lasers has firstly been utilized to analyze the dynamical process in the AO Q-switched CO2 laser. This theory perfectly explains the behavior of energy transfer between different molecules in laser gain medium, and describes the shape of pulse laser. The calculated pulse waveforms are in good agreement with the experimental result. Both the experimental and theoretical results present that the optimal value of output mirror transmittance is 39%. Under this condition, the measured peak power is 4750W and pulsed width is 160ns, which is consistent with the calculations. Six-temperature model is a perfect theory for CO2 laser kinetics, which will lay a theoretical foundation for the laser optimum design. [Copyright &y& Elsevier]

Abstract: We propose and experimentally demonstrate a new method for complex-valued wavefield retrieval in off-axis acoustic holography. The method involves use of an intensity-sensitive acousto-optic (AO) sensor, optimized for use at 3.3MHz, to record the acoustic hologram and a computational method for reconstruction of the object wavefield. The proposed method may circumvent limitations of conventional implementations of acoustic holography and may facilitate the development of acoustic-holography-based biomedical imaging methods. [Copyright &y& Elsevier]

Abstract: An acousto-optic modulator (AOM) is used to tune the spectral properties and add a dynamic component to a long period fiber grating (LPG). Most of the physical parameters that an LPG is sensitive to, can be obtained through passive analysis of the spectral changes. Here, we show that by adding a temporal response component to the grating sensitivity, dynamic parameters such as fluid viscosity, can be extracted. By measuring the modulation signal rise time and/or the acousto-optic efficiency, we demonstrate a compact, dip-style, multi-parameter sensor, which is able to measure, among various parameters, the viscosity of a fluid in frequencies up to 700Hz. Further, we show that taking the temporal response into consideration, the sensor has a linear response against viscosity, in contrast to average measurements based on spectral properties. The non-linear component of the average measurements arises from a relaxation of the initial acoustic perturbation on a timescale longer than the initial rise time. [Copyright &y& Elsevier]

Abstract: Here, we describe a combination approach using Two Calibration-Free Methods with reflectance near-infrared (TCFM-NIR), which involves detecting end-points for active pharmaceutical ingredients (APIs) blending by simultaneously monitoring specific NIR peak intensity of APIs and calculating moving block standard deviation (MBSD). After determining the specific NIR peak range of nicaldipine hydrochloride, conditions for TCFM-NIR were established by monitoring the differential intensity of the second peak (1136nm) while MBSD was calculated from the NIR peak intensity between 1100 and 1150nm. In comparison with the validated reference method of UV–VIS spectroscopy, which is particularly destructive, TCFM-NIR was found to be useful in detecting end-points for blending of nicaldipine hydrochloride. TCFM-NIR monitors two important factors for estimation of blend uniformity: API concentration, using specific NIR peak intensity for APIs, and blend homogeneity, using MBSD. Also, the conditions of TCFM-NIR were confirmed to be adequate by using Partial Least Square (PLS). Further, simultaneously monitoring these two blend uniformity factors is more useful in preventing estimation errors for nondestructive monitoring of blend homogeneity than monitoring only one factor, as with NIR spectroscopy. [Copyright &y& Elsevier]

Abstract: An acoustic guidance method for pedicle screw placement during spine fixation surgery was recently investigated, with a view toward preventing complications such as injury to the spinal cord, thecal sac, and spinal nerve roots due to screw misplacement. The method relies upon the change in the ultrasound amplitude reflected at different sites—from the outer posterior cortex, through the pedicle, and towards the distal ventral cortex. The amplitude change was empirically observed through in vitro measurement of ultrasound amplitude at the different sites by inserting a 2.5-MHz single element transducer into a vertebral body through insertion pathway created by an advancing screw. This paper provides a theoretical and experimental rationale behind these empirical findings and distance-dependent correlation coefficients between amplitude and bone mineral density within the vertebral body, which approached 97%. [ABSTRACT FROM AUTHOR]

Abstract: By considering the influence of the acousto-optic (AO) modulator and the nonlinear loss due to harmonic conversion in the intra-cavity frequency-doubling laser, a developed rate equation model for diode-pumped dual-loss-modulated Q-switched and mode-locked (QML) Nd:LuVO4/KTP green laser with acousto-optic (AO) modulator and Cr4+:YAG saturable absorber is presented. With this developed model, the pulse width, single-pulse energy and the other dual-loss-modulated QML green laser characteristics are numerically simulated. The simulation results show that the turnoff time is of great importance for the pulse energy and pulse width of the Q-switched pulse. A diode-pumped dual-loss-modulated QML Nd:LuVO4/KTP laser is constructed to successfully demonstrate the numerical simulation application. [Copyright &y& Elsevier]

Abstract: When an acoustic wave excites a phase-shifted fiber Bragg grating (PSFBG) several properties of the transmission/reflection spectrum, such as transmission notch depth and spectral bandwidth are influenced. In this work, a study on the effect of acoustic waves in PSFBGs is presented. The results are supported by theoretical simulation and experimental work. The technique can be used for different applications, such as in a fast tunable optical notch filter. [ABSTRACT FROM AUTHOR]