Optical Pressure Research Articles

Intense Star Cluster Formation: Stellar Masses, the Mass Function, and the Fundamental Mass Scale

Within the birth environment of a massive globular cluster, the combination of a luminous young stellar population and a high column density induces a state in which the thermal optical depth and radiation pressure are both appreciable. In this state, the sonic mass scale, which influences the peak of the stellar mass function, is tied to a fundamental scale composed of the Planck mass and the mass per particle. Thermal feedback also affects the opacity-limited minimum mass and how protostellar outflows and binary fragmentation modify stellar masses. Considering the regions that collapse to form massive stars, we argue that thermal stabilization is likely to flatten the high-mass slope of the initial mass function. Among regions that are optically thick to thermal radiation, we expect the stellar population to become increasingly top-heavy at higher column densities, although this effect can be offset by lowering the metallicity. A toy model is presented that demonstrates these effects and in which radiation pressure leads to gas dispersal before all of the mass is converted into stars.

Enhanced Quantum Efficiency via Co-substitution in Sr2[MgAl5N7]:Eu2+ for Spectroscopic Applications including Laser Displays with Ultra-high Luminescence Saturation Threshold.

A series of Sr2[Mg1-xLixAl5-xSixN7]:0.01Eu2+ (SMAN-xLS, 0≤x≤0.5) red phosphors were devised and synthesized via the high temperature solid state reaction and the effects of the co-substitution of [Mg-Al]5+ by [Li-Si]5+ on structural and luminescence properties is investigated. With the entry of [Li-Si]5+ into theSr2[MgAl5N7]:0.01Eu2+ (SMAN) lattice, the substitution of Al3+ by Si4+ shifts the emission peak from 657 nm to 647 nm and reduces the excitation in green region. When the amount of [Li-Si]5+ co-substitution is x=0.1, the luminescence intensity and thermal stability of the sample are enhanced, in which the external quantum efficiency is elevated by 49.6%. The increase in lattice rigidity gives rise to higher luminescence intensity, and the introduced trap levels for the compensation of luminescence enhances the thermal stability. Under blue laser excitation, the SMAN-0.1LS can achieve an ultra-high luminescence saturation threshold of 52.22W/mm2, which is a breakthrough performance that has enormous potential for application in high-power laser display light sources. By measuring the pressure-dependent luminescence of SMAN-0.1LS, the emission peak can be shifted from 650 nm to 702 nm with the increase of pressure, and the sensitivity dλ/dP is 5.07 nm/GPa, which is indicative of the potential application of this system as an optical pressure sensor.

Investigating the Potential of Cr3+-Doped Pyroxene for Highly Sensitive Optical Pressure Sensing.

Luminescent manometry has gained significant popularity in recent years due to its capability to provide in situ pressure measurements in a remote manner. Therefore, there is a growing need to identify phosphors with pressure-dependent spectroscopic properties that can be utilized to develop highly sensitive pressure sensors operating over a wide pressure range. Hence, we present a novel temperature-invariant luminescent manometer based on Cr3+ ion emission in pyroxene Ca0.8Sr0.2MgSi2O6:Cr3+. We utilized two readout modes, including an innovative luminescent pressure sensing ratiometric approach based on the broad emission band associated with the 4T2g → 4A2g electronic transition of Cr3+ ions. This approach provided an exceptionally high sensitivity of SR = 50.7 ± 0.5% GPa-1 and ensured temperature-independent pressure measurements, thus offering highly reliable readouts. Furthermore, the proposed readout mode, which leverages changes in luminescence kinetics, demonstrated high sensitivity at high pressure at around 5 GPa (SR ∼ 8 ± 0.2% GPa-1) surpassing the performance of luminescence kinetics-based manometers reported to date. Consequently, Ca0.8Sr0.2MgSi2O6:Cr3+ emerges as a highly promising phosphor with significant application potential for pressure sensing across a broad pressure range.

Enhanced Quantum Efficiency via Co‐substitution in Sr2[MgAl5N7]:Eu2+ for Spectroscopic Applications including Laser Displays with Ultra‐high Luminescence Saturation Threshold

A series of Sr2[Mg1‐xLixAl5‐xSixN7]:0.01Eu2+ (SMAN‐xLS, 0≤x≤0.5) red phosphors were devised and synthesized via the high temperature solid state reaction and the effects of the co‐substitution of [Mg‐Al]5+ by [Li‐Si]5+ on structural and luminescence properties is investigated. With the entry of [Li‐Si]5+ into theSr2[MgAl5N7]:0.01Eu2+ (SMAN) lattice, the substitution of Al3+ by Si4+ shifts the emission peak from 657 nm to 647 nm and reduces the excitation in green region. When the amount of [Li‐Si]5+ co‐substitution is x=0.1, the luminescence intensity and thermal stability of the sample are enhanced, in which the external quantum efficiency is elevated by 49.6%. The increase in lattice rigidity gives rise to higher luminescence intensity, and the introduced trap levels for the compensation of luminescence enhances the thermal stability. Under blue laser excitation, the SMAN‐0.1LS can achieve an ultra‐high luminescence saturation threshold of 52.22W/mm2, which is a breakthrough performance that has enormous potential for application in high‐power laser display light sources. By measuring the pressure‐dependent luminescence of SMAN‐0.1LS, the emission peak can be shifted from 650 nm to 702 nm with the increase of pressure, and the sensitivity dλ/dP is 5.07 nm/GPa, which is indicative of the potential application of this system as an optical pressure sensor.

Highly Sensitive Gas Pressure Sensing with Temperature Monitoring Using a Slightly Tapered Fiber with an Inner Micro-Cavity and a Micro-Channel

A highly sensitive optical fiber gas pressure sensor with temperature monitoring is proposed and demonstrated. It is based on a slightly tapered fiber with an inner micro-cavity forming an in-fiber Mach–Zehnder interferometer (MZI), and a micro-channel is drilled into the lateral wall of the in-fiber micro-cavity using a femtosecond laser to allow gas to flow in. Due to the dependence of the refractive index (RI) of air inside the micro-cavity on its gas pressure and the high RI sensitivity of the MZI, the device is extremely sensitive to gas pressure. To prevent fiber breakage, the MZI is housed in a silicate capillary tube with an air inlet. Multiple modes are excited by slightly tapering the inner micro-cavity, and the resonance dips in the sensor’s transmission spectrum feature different linear gas pressure and temperature responses, so a sensitivity matrix algorithm can be used to achieve simultaneous demodulation of two parameters, thus resolving the temperature crosstalk. As expected, the experimental results demonstrated the reliability of the matrix algorithm, with pressure sensitivity reaching up to ~−12.967 nm/MPa and temperature sensitivity of ~89 pm/°C. The features of robust mechanical strength and high air pressure sensitivity with temperature monitoring imply that the proposed sensor has good practical and application prospects.

Cuffless Wearable Sphygmomanometers Using Dual Digital Optical Frequency Combs in Chalcogenide Chips

AbstractSphygmomanometers typically use a rubber cuff around the upper arm to measure blood pressure, but this method can be uncomfortable. Thus, cuffless sphygmomanometers for continuous blood pressure monitoring in emergencies and healthcare are desirable. While electrical and optical blood pressure sensors offer high sensitivity, they often face issues like limited pressure range, temperature drift, slow response, and wearability problems. To tackle these limitations, the study designs a unique cuffless wearable blood pressure sensor (12 mm × 2 mm × 0.5 mm) featuring two original components: a GeSbS/AsS chalcogenide dual‐microring chip for high sensitivity, and a dual digital optical frequency comb (DDOFC) system for fast response and cost‐effective detection. The sensor is comparable to reported electrical and optical blood pressure sensors in its detection limit (23 Pa) but has a ten‐times faster response rate (2 kHz), a 1000‐times longer stable operation (>4.3 × 107 cycles), and a well‐compensated temperature drift (<0.012 pm/°C) that eliminates the need for temperature control. This innovation shows promise for wearable electronics and mobile healthcare, enabling the capture of critical cardiovascular details for applications like in‐surgery monitoring, orthostatic hypotension studies, and early detection of myocardial ischemia and strokes.

High sensitivity optical pressure sensor based on graphene/molybdenum disulfide composite film.

In this paper, a high sensitivity optical pressure sensor based on a graphene/molybdenum disulfide (MoS2) composite film is proposed. The sensor is composed of a polydimethylsiloxane (PDMS) pyramid structure, graphene/MoS2 composite film, and lithium niobate waveguide. The pressure deforms the PDMS pyramid structure, which leads to the change of the refractive index of the graphene/MoS2 composite film, and finally be detectable sensitively by the variation of the interference spectrum. Experiments have been carried out using our sensor prototype, and the sensitivity is up to 575.233 nm/kPa in the pressure range of 0 kPa-0.123 kPa, which is much higher than that of typical optical pressure sensors. This shows the advantages of high sensitivity optical pressure sensors based on the graphene/MoS2 composite film, which is expected to be applied in highly sensitive pressure detection environments.

Research on the Fabrication and Parameters of a Flexible Fiber Optic Pressure Sensor with High Sensitivity

In recent years, flexible pressure sensors have garnered significant attention. However, the development of large-area, low-cost, and easily fabricated flexible pressure sensors remains challenging. We designed a flexible fiber optic pressure sensor for contact force detection based on the principle of backward Rayleigh scattering using a single-mode optical fiber as the sensing element and polymer PDMS as the encapsulation material. To enhance the sensor’s sensitivity and stability, we optimized its structural design, parameters, and fabrication process and measured the fiber strain using an optical frequency domain reflectometer (OFDR). The results showed that the sensor achieved a high sensitivity of 6.93247 με/kPa with a PDMS concentration ratio of 10:1, a curing time of 2 h, and a substrate thickness of 5 mm. The sensor demonstrated excellent linearity and repeatability in static performance tests and was successfully used to monitor the plantar pressure distribution in real time. This flexible fiber optic pressure sensor can be developed via a simple fabrication process, has a low cost, and has high sensitivity, highlighting its potential applications in smart wearables and medical diagnostics.

Continuous Space-Time Crystal State Driven by Nonreciprocal Optical Forces.

We show that the continuous time crystal state can arise in an ensemble of linear oscillators from nonconservative coupling via optical radiation pressure forces. This new mechanism comprehensively explains observations of the time crystal state in an array of nanowires illuminated with light [T. Liu et al., Nat. Phys. 19, 986 (2023).NPAHAX1745-247310.1038/s41567-023-02023-5]. Being fundamentally different from regimes of nonlinear synchronization, it has relevance to a wide range of interacting many-body systems, including in the realms of chemistry, biology, weather, and nanoscale matter.

Static pressure response model of fluorescent pressure-sensitive film for underwater surface pressure measurement

The fluorescent pressure-sensitive film (FPSF) is a non-contact, deformation-based optical pressure sensor with high spatial resolution. The pressure response principle of FPSF is to convert pressure change into variations in fluorescent intensity through the deformation of fluorescent microspheres embedded within the film. To quantitatively analyze the pressure–deformation–intensity mechanism, a static pressure response model was established in this study. First, a finite element model was developed to predict the deformation of microspheres within the film under pressure. Second, the deformation-induced variation in fluorescent intensity was modeled with consideration of the light path blockage effect. The pressure calibration curve of the FPSF predicted by the proposed model was noted to be consistent with the experimental results of underwater calibration. In addition, the relationship between pressure sensitivity and the structural parameters of the FPSF were investigated using the pressure response model.

Few-mode optical fiber-based flexible pressure feedback tentacle doped with fluorescence temperature pointer

Abstract In this paper, a flexible fiber pressure feedback whisker is proposed, which consists of a water droplet shaped polydimethylsiloxane (PDMS) elastomer with an embedded balloon shaped few mode fiber. The mechanical sensing performance of the device was analyzed and optimized using a combination of finite element method and beam propagation method (BPM). The built-in cladding corroded few-mode fiber increases pressure sensitivity by more than four times. The collection efficiency of fluorescence signal is improved by cladding corrosion. The PDMS elastomer was doped with upconversion nanoparticles NaYF4:Yb, Er@NaYF4 in order to achieve temperature measurement by fluorescence intensity ratio technology. The combination of fluorescence signal and interference spectrum can not only achieve real-time and accurate pressure detection at different temperatures, but also incorporate fluorescent materials into flexible bionic skin for temperature self-compensation, which has potential application value for the development of bionic fiber micro-nano sensing and control devices.

A Review of Patient Bed Sensors for Monitoring of Vital Signs.

The analysis of biomedical signals is a very challenging task. This review paper is focused on the presentation of various methods where biomedical data, in particular vital signs, could be monitored using sensors mounted to beds. The presented methods to monitor vital signs include those combined with optical fibers, camera systems, pressure sensors, or other sensors, which may provide more efficient patient bed monitoring results. This work also covers the aspects of interference occurrence in the above-mentioned signals and sleep quality monitoring, which play a very important role in the analysis of biomedical signals and the choice of appropriate signal-processing methods. The provided information will help various researchers to understand the importance of vital sign monitoring and will be a thorough and up-to-date summary of these methods. It will also be a foundation for further enhancement of these methods.

Dynamic Wave Measurement With a High Spatial Resolution Distributed Fiber Optic Pressure Sensor

Dynamic Wave Measurement With a High Spatial Resolution Distributed Fiber Optic Pressure Sensor

Study by simulation and realization of a fiber optic pressure sensor based on a PDMS flexible µ-membrane

Study by simulation and realization of a fiber optic pressure sensor based on a PDMS flexible µ-membrane

Characterization of hygrothermal, gas pressure and stress characteristics for poplar wood during unilateral surface densification

Unilateral surface compression in wood presents notable benefits, including reduced wood volume loss and energy consumption, rendering a highly promising and extensive utilization. However, shortcomings in compressed wood arise due to unclear gas pressure, temperature, and moisture content distribution within the wood during hot pressing. In this paper, the temperature and pressure distribution were analyzed utilizing an optical fiber temperature and pressure measurement system within the wood during hot pressing. Moreover, the moisture content, stress and strain in each layer at the end of hot pressing were discussed extensively. The results showed that the wood surface layer (SL) and subsurface layer (SSL) maximum temperature values were similar even with different layer thicknesses. Under sealing conditions, SL and SSL temperatures were generally 6 ℃ to 7 ℃ higher compared to unsealing conditions. The gas pressure maximum value exhibited an opposite order, gradually transferring to the core layer (CL) and declining as the processing time extended. During compression treatment, moisture migrated from the hot end to the cold within the wood. The moisture content displayed significant differences between the middle and end parts of the wood under unsealed conditions, with the disparity becoming more pronounced further away from the hot end. The transition region of the compressed wood served as a stress concentration area, experiencing the highest levels of stress. The dense region followed with the second highest stress levels, while the un-densified region exhibited the least amount of stress. Under the same process parameters, the thickness had little influence on the distribution of dense layers.

Design and performance simulation of a silica microdisk cavity optical pressure sensor

The opto-mechanical system of optical whispering-gallery mode (WGM) microcavities confines resonant photons in micro-scale resonators for a long time, which can strongly enhance the interaction between light and matter, making it an ideal platform for various sensors. To measure the slim optical pressure in the interaction between the laser and matter, a silica microdisk cavity sensor with metal film is designed in this paper. In this study, the finite element method was employed to investigate the opto-mechanical coupling mechanism in a microdisk cavity. From the aspects of optics and mechanics, the structural parameters of the sensor were optimized and the performance was simulated. The simulation results show that at 1550 nm, the sensor’s optical quality factor (Q) can reach ∼104, the free spectral range is ∼5.3nm, the sensing sensitivity is 5.32mPa/Hz1/2, and the optical force resolution is 6.61×10−12N, which is better than the thin-film interferometry and optical lever method.

Extension of optical radiation pressure force exerted on rigid sphere by non-diffracting beams to acoustical domain

Extension of optical radiation pressure force exerted on rigid sphere by non-diffracting beams to acoustical domain

Resonant mechanical vibration of a polymer PVC film under modulated optical excitation

The mechanical response of plasticized thin PVC films under a modulated optical radiation pressure excitation is investigated as a function of the plasticizer content. A resonant behavior with different quality factor depending on the plasticizer content is investigated. The higher the content, the larger the resonant width. A significant thinning of the film is observed, whatever the plasticizer content. The surface tension of the air/solid interface is extracted and shown to hardly vary. The loss factor which is known as the ratio of dissipated energy to stored energy is, on the other hand, dependent on the plasticizer content. In particular, the optical studies reveal that all the energy is always stored at the film interfaces with a dissipation described by the well-known loss factor E′′ of the Young’s modulus.

An FBG-based optical pressure sensor for the measurement of radial artery pulse pressure.

One of the diagnostic tool for clinical evaluation and disease diagnosis is a pulse waveform analysis. High fidelity radial artery pulse waveforms have been investigated in clinical research to compute central aortic pressure, which has been demonstrated to be predictive of cardiovascular diseases. The radial artery must be inspected from several angles in order to obtain the best pulse waveform for estimate and diagnosis. In this study, we present the design and experimental testing of an optical sensor based on Fiber Bragg Gratings (FBG). A 3D printed device along with the FBG is used to measure the radial artery pulses. The proposed sensor is used for the purpose of quantifying the radial artery pulse waveform across major pulse position point. The suggested optical sensing system can measure the pulse signal with good accuracy. The main characteristic parameters of the pulse can then be retrieved from the processed signal for their use in clinical applications. By conducting experiments under the direction of medical experts, the pulse signals are measured. In order to experimentally validate the sensor, we used it to detect the pulse waveforms at Guan position of the wrist's radial artery in accordance with the diagnostic standards. The findings show that combining optical technologies for physiological monitoring and radial artery pulse waveform monitoring using FBG in clinical applications are highly feasible.

Initial experimental testing of a hybrid solar-dish Brayton cycle for combined heat and power (ST-CHP)

The Solar Turbo Combined Heat and Power (ST-CHP) project developed a novel solar-gas hybrid prototype for combined heat and power generation in Pretoria, South Africa. A vacuum-membrane faceted parabolic dish with a large-pipe open-cavity receiver was coupled to a counterflow recuperator, a combustion chamber, a micro gas turbine with air bearings and a phase change thermal energy storage unit containing solar salts. This study aimed to validate the electrical output of the full-scale dish-Brayton prototype, addressing the literature gap on micro-scale dish-Brayton plants' in-field power generation. Solar hybridization of micro gas turbine technology can significantly reduce combustion fuel consumption. A performance analysis under relevant conditions revealed a late afternoon micro gas turbine output intermittently peaking at 0.4kWe and subsequently stabilizing to a steady state of 0.145kWe at 130krpm. A SimuPact numerical model and an analytical model supplemented the telemetry data to reduce interference in the experimental setup and fully characterize the ST-CHP prototype performance, estimating a steady-state turbine isentropic efficiency of 57%, a compressor efficiency of 71% and a collector efficiency of 17% due to the late afternoon steady-state point. Analytical case studies revealed that fuel savings of between 12% and 33% at the combustion chamber were achievable from the solarized preheating. A subsequent test of the micro gas turbine without solar hybridization or a recuperator resulted in 1.05kWe being generated. The study confirms the dish-Brayton prototype's viability for combined heat and power generation, producing an initial full-scale performance characterisation during in-field testing, and highlighting the impact of solar hybridization on turbine electrical output. Optical efficiency, insulation effectiveness, pressure losses, and turbine operating conditions were identified as critical areas requiring optimization to improve electrical output. The lessons learned, and the calibrated numerical model may be used to optimize the performance of the dish-Brayton plant in future work. The successful in-field full-scale power generation of the ST-CHP prototype adds to the available literature on dish-Brayton technology and brings the technology closer to a commercial product.