Optical architecture for an acoustooptic correlator

The structure of the acoustic field defines the key parameters of acousto-optical (AO) devices. To confirm their compliance with the expected values in the presence of multiple real factors, AO crystalline cells require accurate experimental investigation of the acoustic field after being totally assembled. For this purpose, we propose to detect and quantify all the acoustic waves propagating in AO cells using an impulse acoustic microscopy technique. To validate this approach, we have analyzed both theoretically and experimentally the modes, amplitudes, propagation trajectories, and other features of the ultrasonic waves generated inside an AO modulator made of fused quartz. Good correspondence between theoretical and experimental data confirms the effectiveness of the proposed technique.

This paper presents a novel thermal tunable bulk-micromachined optical filter. The device has been achieved based on a Fabry-Perot interferometer employing a bulk silicon cavity and high-reflectivity coating (HRC). A dense boron doped silicon resistor has been used as the heater and the cantilever structure has been designed to provide a good thermal isolation. The tunable optical filter has been successfully fabricated using bulk micromachining technology. Tunability is realized by changing the refractive index of the bulk silicon cavity through heating resistor. The maximum wavelength tuning is about 17 nm with driving voltage less than 14 V. The filter linewidth was achieved a value of 0.29 nm and the Free Spectral Range (FSR) was 21.9 nm. The heating and cooling responding times are less than 50 ms.

Tunable fiber optic filter has extensive applications in telecommunications, spectroscopy, and fiber optic sensing. Many research attempts have been devoted to develop a filter with a wide tuning range, a fast tuning speed, a fine tuning resolution, and high reliability. Despite of the progress made so far, a tunable fiber optic filter that combines all these qualities is still a subject of intensive research. This thesis describes the design, fabrication and test results of a high performance tunable fiber optic filter. The filter is piezo-driven using a flexural hinge structure for displacement magnification and an axial strain of a fiber Bragg grating. Finite element analysis was used to design the mechanical structure to achieve the required displacement magnification and reaction force for grating compression. A passive thermal compensation design was implemented with two spacers of different coefficients of thermal expansion to compensate the thermal-induced wavelength drift. A feedback control system with a linear variable differential transformer was employed to control the displacement and to achieve the designed tuning accuracy. A tuning range of 13.7 nm, a maximum closed loop switching time of 17.3 ms, and a wavelength drift of 1.4 pm/C were achieved. The flexural-hinge structure, that offers noise-free motion, no need of lubricants and no wear, ensures its long-term reliability.

The More Effective and the More (bio) Similar: Plerixafor and Filgrastim XM02 (tevagastrim) As First Line PBSC Mobilization Strategy in Patients with Multiple Myeloma and Lymphomas Candidate to ABMT

Hyperspectral imaging was originally developed for use in remote sensing applications. More recently, it has been applied to biological imaging systems, such as fluorescence microscopes. The ability to distinguish molecules based on spectral differences has been especially advantageous for identifying fluorophores in highly autofluorescent tissues. A key component of hyperspectral imaging systems is wavelength filtering. Each filtering technology used for hyperspectral imaging has corresponding advantages and disadvantages. Recently, a new optical filtering technology has been developed that uses multi-layered thin-film optical filters that can be rotated, with respect to incident light, to control the center wavelength of the pass-band. Compared to the majority of tunable filter technologies, these filters have superior optical performance including greater than 90% transmission, steep spectral edges and high out-of-band blocking. Hence, tunable thin-film optical filters present optical characteristics that may make them well-suited for many biological spectral imaging applications. An array of tunable thin-film filters was implemented on an inverted fluorescence microscope (TE 2000, Nikon Instruments) to cover the full visible wavelength range. Images of a previously published model, GFP-expressing endothelial cells in the lung, were acquired using a charge-coupled device camera (Rolera EM-C2, Q-Imaging). This model sample presents fluorescently-labeled cells in a highly autofluorescent environment. Linear unmixing of hyperspectral images indicates that thin-film tunable filters provide equivalent spectral discrimination to our previous acousto-optic tunable filter-based approach, with increased signal-to-noise characteristics. Hence, tunable multi-layered thin film optical filters may provide greatly improved spectral filtering characteristics and therefore enable wider acceptance of hyperspectral widefield microscopy.

A broad-temperature-range wavelength tracking system employing a thermistor monitoring circuit and a tunable optical filter is proposed and experimentally demonstrated. In this scheme, a thermistor monitoring circuit is utilized to acquire the real-time resistance values of a distributed feedback laser diode (DFB-LD). When the mapping relationship curve among thermistor resistance, temperature, and center wavelength of the DFB-LD is established, the drive voltage of the narrowband tunable optical filter is dynamically adjusted to regulate its filter window. Therefore, wavelength tracking is achieved by matching the filter window and the center wavelength of the DFB-LD. The experimental results show that the proposed system can achieve adaptive wavelength tracking within the operation band of 1539.4 nm to 1548.6 nm across a temperature range from −40 °C to 60 °C. The wavelength detection resolution and the minimum step of wavelength control are better than 0.79 pm and 0.1 nm, respectively. By exploiting the conversion characteristics between the thermistor and the center wavelength of the DFB-LD, this approach transforms laser wavelength detection into a low-cost, real-time electrical measurement, significantly enhancing transmission stability and reliability of laser sources in complex thermal environments.

Optical measurements are closely related to the optical signal-to-noise ratio (OSNR) of the laser, which can be improved using a tunable optical filter (TOF) to suppress frequency noise. For an external-cavity tunable laser with a tuning range larger than the TOF bandwidth, the wavelength at the center of the TOF passband must be varied based on the laser tuning. This study proposes a tunable-laser OSNR-enhancement method based on the Fabry-Pérot (FP) interferometer. The FP signal contains the wavelength information of the swept laser, which can be used to determine the real-time driving voltage of the TOF. Notably, the laser needs to be continuously tunable without mode hopping, and the free spectral range of the FP interferometer must be smaller than the TOF bandwidth.

We present an optical fiber voltage sensor by Michelson interferometer (MI) employing a Fabry–Perot (F–P) tunable optical filter and the phase generated carrier demodulation algorithm. By mounting an MI fabricated by an optical fiber coupler on a piezoelectric transducer, a dynamic strain would be generated to change the phase difference of the interferometer when the measured voltage is applied on the piezoelectric. The phase generated carrier demodulation method was used to obtain the phase variation of the interferometer by applying demodulate signal on an F–P tunable optical filter. The measured voltage can be obtained by the variation of the phase; the random phase shift in the interferometer and the intensity fluctuation of the light source of the sensor can be eliminated. The experiment results show that the relation between the phase variation and the voltage applied on the piezoelectric is approximately linear. The dielectric reliability of the sensor has been verified according to the IEC standard.

This processor is oriented to studies in the extra-galactic astronomy as well as to searching the extra-solar planets, so that algorithm of the space-and-time integrating is desirable for a wideband spectrum analysis with an improved resolution. It includes 1D -acousto-optic cells as the input devices for a 2D -optical data processing. The importance of this algorithm is based on exploiting the chirp Z − transform technique providing a 2D -Fourier transform of the input signals. The system produces the folded spectrum, accumulating advantages of both space and time integrating. Its frequency bandwidth is practically equal to the bandwidth of transducers inherent in acousto-optical cells. Then, similar processor is able to provide really high frequency resolution, which is practically equal to the reciprocal of the CCD-matrix photo-detector integration time. Here, the current state of designing the triple product acousto-optical processor in frames of the astrophysical instrumentation is presented.

Magneto-optical devices based on Bragg diffraction of light by magnetostatic waves (MSWs) offer the potential of large time-bandwidth optical signal processing at microwave frequencies of 1 to 20 GHz and higher. A thin-film integrated-optical configuration, with the interacting MSW and guided-optical wave both propagating in a common ferrite layer, is necessary to avoid shape-factor demagnetization effects. The underlying theory of the MSW-optical interaction is outlined, including the development of expressions for optical diffraction efficiency as a function of MSW power and frequency, device geometry, materials properties, and other relevant parameters. Recent experimental observations of anisotropic Bragg diffraction and collinear TE↔TM mode conversion induced by MSWs in yttrium iron garnet (YIG) thin films suggest that high-performance MSW integrated-optical devices are feasible. Diffraction levels as large as 4% (7-mm interaction length) and a modulation dynamic range of ∼30 db have been demonstrated. Potential signal processing applications are mentioned, including: spectrum analyzers, convolvers/correlators, deflectors, non-reciprocal optical isolators, and tunable narrowband optical filters. Advantages of these MSW-based devices over the analogous acousto-optical devices include: much greater operating frequencies, tuning through the MSW dispersion relation by varying either the rf frequency or the applied bias magnetic field, simple MSW transducer structures (e.g., a single stripline), and the potential for very high diffraction efficiencies.

The capability of trapping and collecting airborne particulate matter is of great applications in the fields of environmental engineering, healthcare systems, energy engineering, and so forth. In this work, we show a facile strategy of trapping and collecting airborne particulate matter by a simple and compact ultrasonic device system. In this device, a radiation plate is bonded with a Langevin transducer for generating circular standing flexural waves (CSFWs) in the plate. Under the excitation of the CSFWs in the radiation plate, an acoustic field and an acoustic streaming field can be induced in the air gap formed by the radiation plate and a sampling plate. Through numerical simulations, we find that the multiple acoustic streaming vortices symmetric about the central axis in the air gap are responsible for trapping and collecting airborne particulate matter onto the sampling plate, while acoustic radiation force contributes little. Also, it is numerically found and experimentally verified that the resonant acoustic field and the accompanying acoustic streaming field can be tuned by varying the thickness of air gap. Through experimentation, we investigate and clarify the dependency of collection performance on parameters such as the air gap thickness and radius, sonication time, driving voltage, and the angle between the radiation plate and the sampling plate. Due to its contactless and mild handling attributes, our ultrasonic airborne particulate matter sampler can circumvent the clogging and secondary pollution issues and ensure device reusability and little damage to samples compared with other airborne particulate matter processing methods.

Applications of Gallium Phosphide (GaP) acousto-optic devices, at wavelengths from 570nm - 1.06um seem to be ideal for fiber optic modulators, scanners, deflectors, frequency shifters, Q-switches and mode lockers. One of the major applications are for RF spectrometers in early warning radar receivers and auto-correlators. Longitudinal GaP acousto-optic Bragg cells which have respectively operational frequencies in the range of 200 MHz - 3 GHz and diffraction efficiencies in the range of 120%/RF watt to 1%/RF watt have recently been fabricated. Comparatively, shear GaP devices which have operational frequencies in the range of 200 MHz to 2 GHz and diffraction efficiencies from 80%/RF watt to 7%/RF watt have also been constructed.

Summary form only given. In optical burst switching (OBS) networks, a short switching time is very important for handling fine grain packets such as TCP ACK packets, which are only 40 bytes in length. At data rate of 10 Gbps, such a data burst will occupy a period of only 32 ns. Therefore OXC (optical cross connector) with fast switching speed, for example < 100 ns, are generally required for OBS networks. There are many methods to configure an OXC. Tunable optical filters may used to build large scale OXC. In an optical filter, the tuning ability is usually achieved by introducing extra phase shift via the electro optic, thermo optic, or piezoelectric effect, etc. Up to date, the most commonly used tunable filter structures are interferometric such as Fabry-Perot (FP) and Mach-Zehnder (MZ) interferometers. They are usually poor in the performance of passband flatness and the crosstalk, and require robust electronics to stabilize the central wavelength. Hence, they are rarely practically used as switching elements in the dense wavelength division multiplexing (DWDM) optical networks. In recent years, digitally tunable optical filter (DTOF) has received increasingly attention. Structures based on the arrayed waveguide grating (AWG) and on-off switches have been reported. DTOF based on AWG may require precision thermal control for AWG usually suffers the problem of temperature dependence. In this talk, we present a novel approach to realize the DTOF (digitally tunable optical filter) based on DWDM thin film filters (TTF) and semiconductor optical amplifier (SOA). Apart from the outstanding feature being consistent with the wavelength comb suggested by international telecommunication union-telecommunication (ITU-T), the proposed DTOF is very stable in temperature performance. Furthermore it requires less SOAs in comparison with the reported structures.

Tunable optical filters are important components for controlling light in dense wavelength division multiplex (DWDM) systems. They can be used in many optical components, and their tunability can be realized using mechanical equipment, or/and changing the refractive index in transmission media. In DWDM systems several types of tunable filters are used. They are produced with different technologies, and they have different technical parameters, but the most important one is still their price

Monitoring optical power from the broadened optical spectrum acquired by scanning a low-cost tunable optical filter (TOF) is a practical and challenging task for the management of wavelength-division-multiplexing (WDM) networks. Existing methods, such as least squares (LS) and regularized sparse recovery (RSR) methods, suffer from performance deterioration when the power discrepancies between adjacent channels are significant. In this letter, we formulate it as a maximum a posteriori (MAP) estimation problem under Bayesian framework. A weighted-RSR algorithm is, therefore, proposed to estimate the optimal channel power. Experimental results demonstrate that, using commercial low-cost TOFs, the weighted-RSR can accurately monitor the power of mixed 10-G/40-G WDM channels with 50-GHz channel spacing and 10-dB power difference.