Optical Readout System Research Articles

Opto-mechanical stacked metamaterials for optical readout millimeter wave detection

An opto-mechanical stacked metamaterials is proposed. Different from traditional metamaterials, it adopts a separable design to realize the stacked structure of the lower and upper chips. It can break the metamaterial thickness limit and integrate absorbing/execution units on functional layer with a thickness less than one thousandth of a wavelength, enabling high-performance detection. We design and prepare a millimeter wave opto-mechanical stacked metamaterial array detector, whose upper chip is only 1/2133 of the wavelength, but the absorptivity is about 99 %. Unlike the traditional detectors that convert millimeter wave radiation into electrical signals, it converts the radiation into micromechanical deflections opto-mechanical structures, and then reads them out optically. It’s equivalent to converting the millimeter wave detection into visible light detection. An optical readout system was constructed to verify the detection performance. Experimental results show that the response time can reach 20 ms and the NEP (Noise Equivalent Power) is 1.1 × 10−10 W/Hz1/2.

3D optically-stimulated-luminescence-based dosimetry using LYSO:Ce scintillators

The search for a reusable 3D dosimeter is ongoing and motivated by the impact it would have on development and verification of complex modalities in radiotherapy. We present a proof-of-concept 3D measurement of a proton-irradiated LYSO:Ce scintillator, using the resettable photon-emission mechanism known as optically stimulated luminescence and a novel optical readout system. Through this demonstration, we show that LYSO:Ce, in addition to being capable of real-time beam imaging, can be employed as a reusable post-irradiation 3D dosimeter with high spatial resolution.

Integrated photonic reservoir computing with an all-optical readout.

Integrated photonic reservoir computing has been demonstrated to be able to tackle different problems because of its neural network nature. A key advantage of photonic reservoir computing over other neuromorphic paradigms is its straightforward readout system, which facilitates both rapid training and robust, fabrication variation-insensitive photonic integrated hardware implementation for real-time processing. We present our recent development of a fully-optical, coherent photonic reservoir chip integrated with an optical readout system, capitalizing on these benefits. Alongside the integrated system, we also demonstrate a weight update strategy that is suitable for the integrated optical readout hardware. Using this online training scheme, we successfully solved 3-bit header recognition and delayed XOR tasks at 20 Gbps in real-time, all within the optical domain without excess delays.

Study of radiation effects on SiPM for an optical readout system for the EIC dual-radiator RICH

Silicon photomultipliers (SiPM) are the potential candidate photodetector technology selected for the dual-radiator Ring-Imaging Cherenkov (dRICH) detector of the future Electron-Ion Collider (EIC). SiPM are inexpensive devices, with high detection efficiency and insensitive to the high magnetic field experienced at the expected location of the sensors in the experiment. On the other hand, SiPM are susceptible to radiation damage. The integrated radiation level at the location of the sensors in the experiment is expected to be moderate, nonetheless it should be tested whether the capabilities for single photon-counting can be maintained to ensure the optimal dRICH detector performance across the years keeping the dark count rates under control as well. In this paper, the current status of the research studies performed for the EIC dRICH application and the first results on a sample of commercial and prototype SiPM sensors are presented.

Optomechanical Cooling and Inertial Sensing at Low Frequencies

An inertial sensor design is proposed in this paper to achieve high sensitivity and large dynamic range in the subhertz-frequency regime. High acceleration sensitivity is obtained by combining optical cavity readout systems with monolithically fabricated mechanical resonators. A high-sensitivity heterodyne interferometer simultaneously monitors the test mass with an extensive dynamic range for low-stiffness resonators. The bandwidth is tuned by optical feedback cooling to the test mass via radiation pressure interaction using an intensity-modulated laser. The transfer gain of the feedback system is analyzed to optimize system parameters towards the minimum cooling temperature that can be achieved. To practically implement the inertial sensor, we propose a dynamic cooling mechanism to improve cooling efficiency while operating at low optical power levels. The overall system layout presents an integrated design that is compact and lightweight.

The upgrade of the ASACUSA scintillating bar detector for antiproton annihilation measurements

Antiproton annihilations on matter nuclei are usually detected by tracking the charged pions emitted in the process. A detector made of plastic scintillating bars have been built and used in the ASACUSA experiment for the last 10 years. Ageing, movements and transports caused stress on the internal mechanical structure and impacted mostly on the optical readout system which was eventually upgraded: the so far used multi-anode photo-multiplier tubes (PMTs) have been replaced by silicon photomultipliers (SiPM) and the front-end electronics had to be adapted to cope with the new signal formation. This work describes the design and operations of the upgrade, as well as the validation tests with cosmic rays.

Advancing Electrochemical Screening of Neurotransmitters Using a Customizable Machine Learning-Based Multimodal System

High throughput and automated optical readout systems are already an industry standard in life sciences for screening several reactions at once. However, such high throughput systems are in an inceptive stage for studying electrochemical interactions. This limitation, for example, slows down the process of establishing property-performance relation of novel materials for biochemical sensing. Herein, building on our prior work, we fabricate a low-cost customizable platform to screen response of acetic acid-treated laser induced graphene to identify and quantify four biogenic amine neurotransmitters in artificial saliva, namely dopamine, serotonin, epinephrine, and norepinephrine, which due to similar molecular structures are difficult to differentiate using conventional electrochemical methods. Our analytical platform analyzes multiple sensors at once and processes the data using machine learning to rapidly screen the material–molecule interactions by combining several electrochemical spectral components (fingerprints). Combining multiple spectral features, both within one electrochemical module and across different modules, significantly improves the sensor performance and allows identification of the biomolecules using the same material system. The proposed automated electroanalytical system can be used to screen material–molecule interactions as well as high throughput point-of-care testing for rapid, multiplexed, and low-cost molecular detection.

Phosphorescent Microneedle Array for the Measurement of Oxygen Partial Pressure in Tissue.

The knowledge of the exact oxygen partial pressure in tissue is crucial for patient care and in the treatment of ischemic medical conditions. However, current methods to assess oxygen partial pressure in tissue suffer from a variety of disadvantages, including complex equipment and procedures that necessitate trained personnel. Additionally, the barrier function of the stratum corneum reduces oxygen exchange and can consequently hamper surface measurements of rapidly changing oxygen partial pressure in tissue. To overcome these challenges, a novel, easy-to-use technique to monitor the oxygen partial pressure in tissue using microneedle arrays (MNAs) has been developed. The MNAs can be made from poly(ethyl methacrylate) and poly(propyl methacrylate) and overcome the skin's barrier function to measure oxygen in the capillary bed and interstitial fluid of the skin. The MNAs' tips are embedded with an oxygen-sensitive phosphorescent metalloporphyrin, where the oxygen partial pressure inversely correlates to changes in both emission intensity and phosphorescence lifetime of the in-house developed red emitting Pt-core porphyrin. It was demonstrated that the oxygen-sensing MNAs are sufficiently robust to puncture human skin via rupture of the stratum corneum, and that the MNAs can detect changes in oxygen partial pressure in skin within the physiologically relevant range (0-160 mmHg). Additionally, the MNAs can be combined with a wearable wireless optical readout system, making these oxygen-sensing MNAs a novel wearable and portable method for user-friendly monitoring of oxygen partial pressure in skin.

A SiPM-based optical readout system for the EIC dual-radiator RICH

Silicon photomultipliers (SiPM) are candidates selected as the potential photodetector technology for the dual-radiator Ring-Imaging Cherenkov (dRICH) detector at the future Electron-Ion Collider (EIC). SiPM are cheap devices, highly efficient and insensitive to the high magnetic field at the expected location of the sensors in the experiment. On the other hand, SiPM are not radiation tolerant. Despite the integrated radiation level is expected to be moderate it should be tested whether single photon-counting capabilities and the increase in dark count rate can be kept under control to maintain the optimal dRICH detector performance across the years. The current status of the research for the EIC dRICH application and the first results on studies performed on a sample of commercial and prototype SiPM sensors are presented.

Design Optimization and Characterization of Cold Neutron Imaging Detector Based on Novel Gadolinium Scintillation Glass Fiber Arrays and Infinity Corrected Optics

The use of scintillation glass fiber array in the reported cold neutron imaging detector can suppress lateral spreading of the scintillation light effectively and achieve a high spatial resolution while maintaining high detection efficiency. Theoretical analysis and experiments were combined to investigate influencing factors on the spatial resolution, the imaging contrast, the signal-to-noise ratio (SNR), and the detection efficiency with a cold neutron imaging detector made of new gadolinium scintillation glass fiber array and an infinity corrected optical readout system. The experiments were carried out on the Cold Neutron Radiography Facility at China Academy of Engineering Physics (CAEP). The cold neutron imaging detector made of 0.3-mm-thick Tb3+/Ce3+ co-doped Gd2O3 scintillation glass fiber array with a fiber diameter of 6 mm achieved a spatial resolution of 28.8 lp/mm (17.4 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> ), an SNR of 28.6:1, and a cold neutron detection efficiency of 31.6%, i.e., a cold neutron absorption efficiency of 81.0%.

A Terahertz Optomechanical Detector Based on Metasurface and Bi-Material Micro-Cantilevers.

Terahertz imaging technology has shown great potential in many fields. As the core component of terahertz imaging systems, terahertz detectors have received extensive attention. In this paper, a metasurface-based terahertz optomechanical detector is proposed, which is made of two fabrication-friendly materials: gold and silicon nitride. The optomechanical detector is essentially a thermal detector composed of metasurface absorber, bi-material micro-cantilevers and heat insulation pillars. Compared with traditional thermal terahertz detectors, the optomechanical detector employs a metasurface absorber as the terahertz radiation coupler and obtains an absorptivity higher than 90% from 3.24 to 3.98 THz, which is much higher than that of traditional terahertz detectors with absorbers made from natural materials. Furthermore, the detector is fabricated by MEMS process and its responsivity has been verified by a specifically designed optical read-out system; the measured optomechanical responsivity is 24.8 μm/μW, which agrees well with the multi-physics simulation. These results indicated that the detector can be employed as a pixel to form a terahertz focal plane array in the future, and further realize real-time terahertz imaging at room temperature.

Optical fiber hydrogen sensor using metasurfaces composed of palladium

Palladium-based hydrogen sensors have been typically studied due to the dielectric function that changes with the hydrogen concentration. However, the development of a reliable, integral, and widely applicable hydrogen sensor requires a simple readout mechanism and an optimization of the fast detection of hydrogen. In this work, optical fiber hydrogen sensing platforms are developed using an optimized metasurface, which consists of a layer of palladium nanoantennas array suspended above a gold mirror layer. Since the optical properties of these palladium nanoantennas differ from the traditional palladium films, a high reflectance difference can be achieved when the sensor based on the metasurface is exposed to the hydrogen atmosphere. Finally, the optimized reflectance difference ΔR of ∼0.28 can be obtained when the sensor is exposed in the presence of hydrogen. It is demonstrated that this integrated system architecture with an optimized palladium-based metasurface and a simple optical fiber readout system provides a compact and light platform for hydrogen detection in various working environments.

Wideband MOEMS for the Calibration of Optical Readout Systems.

The paper proposes a technology based on UV-LIGA process for microoptoelectromechanical systems (MOEMS) manufacturing. We used the original combination of materials and technological steps, in which any of the materials does not enter chemical reactions with each other, while all of them are weakly sensitive to the effects of oxygen plasma. This made it suitable for long-term etching in the oxygen plasma at low discharge power with the complete preservation of the original geometry, including small parts. The micromembranes were formed by thermal evaporation of Al. This simplified the technique compared to the classic UV-LIGA and guaranteed high quality and uniformity of the resulting structure. To demonstrate the complete process, a test MOEMS with electrostatic control was manufactured. On one chip, a set of micromembranes was created with different stiffness from 10 nm/V to 100 nm/V and various working ranges from 100 to 300 nm. All membranes have a flat frequency response without resonant peaks in the frequency range 0–200 kHz. The proposed technology potentially enables the manufacture of wide low-height membranes of complex geometry to create microoptic fiber sensors.

Plasmonic biosensor based on a gold nanostripe array for detection of microRNA related to myelodysplastic syndromes

We present a new optical biosensor based on surface plasmons excited on an array of gold nanostripes via attenuated total reflection. We investigate performance of the biosensor using a theoretical model that considers both optical and mass transport aspects. The analysis of optical aspects employs two different approaches: a complex model incorporating optical characteristics of the nanostructure as well as the noise characteristics of the optical readout system and a simple model based solely on the figure of merit of the nanostructure. The theoretical analysis suggests that the optimized biosensor is able to detect molecular analytes at concentrations lower by a factor of ~ 10 than conventional surface plasmon resonance biosensors. In order to validate the theoretical model, we characterize the gold nanostripe arrays of different designs in model refractometric and biosensing experiments. We show that the nanoplasmonic sensor exhibits refractive index sensitivity of 1989 nm/RIU and refractive index resolution down to 3.6×10−7RIU. In addition, we use the nanoplasmonic biosensor for the detection of a microRNA biomarker of myelodysplastic syndromes (miRNA-125b) and demonstrate that the biosensor can detect miRNA-125b at concentrations down to ~ 17 pM.

Multimodal real-time frequency tracking of cantilever arrays in liquid environment for biodetection: Comprehensive setup and performance analysis.

We present a nanomechanical platform for real-time quantitative label-free detection of target biomolecules in a liquid environment with mass sensitivity down to few pg. Newly fabricated arrays of up to 18 cantilevers are integrated in a micromachined fluidic chamber, connected to software-controlled fluidic pumps for automated sample injections. We discuss two functionalization approaches to independently sensitize the interface of different cantilevers. A custom piezo-stack actuator and optical readout system enable the measurement of resonance frequencies up to 2MHz. We implement a new measurement strategy based on a phase-locked loop (PLL), built via in-house developed software. The PLL allows us to track, within the same experiment, the evolution of resonance frequency over time of up to four modes for all the cantilevers in the array. With respect to the previous measurement technique, based on standard frequency sweep, the PLL enhances the estimated detection limit of the device by a factor of 7 (down to 2pg in 5min integration time) and the time resolution by more than threefold (below 15s), being on par with commercial gold-standard techniques. The detection limit and noise of the new setup are investigated via Allan deviation and standard deviation analysis, considering different resonance modes and interface chemistries. As a proof-of-concept, we show the immobilization and label-free in situ detection of live bacterial cells (E. coli), demonstrating qualitative and quantitative agreement in the mechanical response of three different resonance modes.

Quantitative detection system for immunostrips in 180nm standard CMOS technology

In this work, a CMOS based optical read-out system for biomarker on immunostrips detection is presented. For the proposed system, a CMOS integrated circuit containing an on-chip photodiode is designed in standard 180 nm UMC CMOS Technology. The system also contains cost-effective 3D Printed structures for holding both IC and the sample immunostrip together. The proposed system can be operated in two modes (1) light reflectance and (2) light transmittance. In the system, a laser with a wavelength of 637 nm is applied to the CMOS IC through immunostrip. Photovoltaic and photoconductive measurements are carried out for each mode on a custom Gluten biomarker immunostrip. Sensing operation of the biomarker is successfully realized with optical powers from 5 mW to 8 mW. Biomaterial density on the immunostrip is sensed and images of the biomarker with varying intensities are constructed from the measurements. Feasibility of the system for low power biomarker sensing applications is demonstrated.

The first round result from the TianQin-1 satellite

The TianQin-1 satellite (TQ-1), which is the first technology demonstration satellite for the TianQin project, was launched on 20 December 2019. The first round of experiment had been carried out from 21 December 2019 until 1 April 2020. The residual acceleration of the satellite is found to be about 1 × 10−10 m/s2/Hz1/2 at 0.1 Hz and about 5 × 10−11 m/s2/Hz1/2 at 0.05 Hz, measured by an inertial sensor with a sensitivity of 5 × 10−12 m/s2/Hz1/2 at 0.1 Hz. The micro-Newton thrusters has demonstrated a thrust resolution of 0.1 μN and a thrust noise of 0.3 μN/Hz1/2 at 0.1 Hz. The residual noise of the satellite with drag-free control is 3 × 10−9 m/s2/Hz1/2 at 0.1 Hz. The noise level of the optical readout system is about 30 pm/Hz1/2 at 0.1 Hz. The temperature stability at temperature monitoring position is controlled to be about ±3 mK per orbit, and the mismatch between the center-of-mass of the satellite and that of the test mass is measured with a precision of better than 0.1 mm.

Interference: A Much-Neglected Aspect in High-Throughput Screening of Nanoparticles.

Despite several studies addressing nanoparticle (NP) interference with conventional toxicity assay systems, it appears that researchers still rely heavily on these assays, particularly for high-throughput screening (HTS) applications in order to generate "big" data for predictive toxicity approaches. Moreover, researchers often overlook investigating the different types of interference mechanisms as the type is evidently dependent on the type of assay system implemented. The approaches implemented in the literature appear to be not adequate as it often addresses only one type of interference mechanism with the exclusion of others. For example, interference of NPs that have entered cells would require intracellular assessment of their interference with fluorescent dyes, which has so far been neglected. The present study investigated the mechanisms of interference of gold NPs and silver NPs in assay systems implemented in HTS including optical interference as well as adsorption or catalysis. The conventional assays selected cover all optical read-out systems, that is, absorbance (XTT toxicity assay), fluorescence (CytoTox-ONE Homogeneous membrane integrity assay), and luminescence (CellTiter Glo luminescent assay). Furthermore, this study demonstrated NP quenching of fluorescent dyes also used in HTS (2',7'-dichlorofluorescein, propidium iodide, and 5,5',6,6'-tetrachloro-1,1',3,3'-tetraethyl-benzamidazolocarbocyanin iodide). To conclude, NP interference is, as such, not a novel concept, however, ignoring this aspect in HTS may jeopardize attempts in predictive toxicology. It should be mandatory to report the assessment of all mechanisms of interference within HTS, as well as to confirm results with label-free methodologies to ensure reliable big data generation for predictive toxicology.

High-speed focus servo control system using Nyquist aperture mounted on a triaxial actuator for holographic disc drive system

We have developed a holographic data storage system using angular-multiplexing recording that has a large capacity of 2 TB and a data transfer rate of 1 Gbit / s. To read a hologram recorded on a holographic disc at high speed, it is necessary to control the relative position shift between a hologram recorded on a disc and a readout optical system. However, in angular-multiplexing data storage systems, the optical system has no moving mechanism, unlike conventional optical discs such as Blu-ray Discs™. Therefore, it is difficult to control the disc position with high precision and to reduce the settling time of the positioning because the holographic disc has no physical structure for the position control mechanism to control the relative position shift. In the systems, a disc mounted on a disc stage is moved to a position where the signal-to-noise ratio of the reproduced hologram becomes the maximum value. Hence, we present a servo control system based on a shift of the Nyquist aperture using a real-time position error signal to control the disc position. In experiments, a positioning accuracy of ±15 μm and a settling time of 8.5 ms for our angular-multiplexing data storage system using a nonlinear parabolic focus position error signal have been observed.

Optical measurements of bottom shear stresses by means of ferrofluids

The research is focused on the development and on the assessment of a measurement technique for bottom shear stresses. In particular, the wall–fluid interaction is analyzed adopting ferrofluids and using an optical readout system. The principle of operation of this technique is based on the capability of ferrofluids to react to external magnetic field changing their shape and their viscosity. The proposed magneto-rheological sensor, consisting in a magnetized drop of ferrofluid located at the channel bottom, is exposed to different flow conditions and its deformations are video-recorded. Thanks to the application of image analyses processes, the relation between shear stresses and magneto-rheological sensor deformation is investigated. The assessment of the measuring technique is carried out in the presence of different sandy bottoms and by considering several hydraulic (steady current) conditions. The range of measured bottom shear stress is 0.01–0.20 N/m$$^2$$. Tests carried out with different sandy bottoms characterized by different roughness provide insights about the high sensitivity of the sensor, which is able to detect slight changes in the sandy bottom mixture (less than 10$$\%$$ concentration in volume). Statistical analysis on the ferrofluid deformation shows that the sensor deformation is strictly related to the local hydrodynamics. For higher Re number we observed larger mean displacement in the direction of the flow and bigger oscillations. Power spectral densities of the ferrofluid displacement and of the velocity fluctuations measured at the ferrofluid apex point show how the two signals are characterized by the same slope in log–log graph for intermediate and high frequencies (> 0.2 Hz) representative of small-scale eddies.