A high-speed Flash-LiDAR CMOS image sensor which is named FLAMES for landing missions is presented. The sensor features 1280(H) × 1024(V) array size with a pixel pitch of 14 µm. It offers a full-frame capture rate of 500 fps, up to 2000 fps for smaller ROI, such as 500(H) × 500(V). The sensor can operate in 3 different modes, and its time gating sharpness is anticipated to be faster than 5 ns. When correlated double sampling (CDS) is utilized, the readout noise is expected to be less than 10 e-. This paper discusses the architecture of FLAMES sensor, the design considerations employed to achieve high speed and fast time gating and presents relevant simulation results.

Neurological conditions such as epilepsy can have a significant impact on people's lives. Here, we discuss a new perspective for the study/treatment of these conditions using photopharmacology. A multimodal, intracranial implant that incorporates fluidic channels for localised drug delivery, electrodes for recording and stimulation, and a light source for photoswitching is used for in vivo administration and deactivation of a photoresponsive AMPA antagonist. We review current advancements in the relevant disciplines and show experimentally that the inhibition of seizure-like events induced in the hippocampus by electrical stimulation can be altered upon switching the drug with light. We discuss the interconnection of the drug's photopharmacological properties with the design of the device by modelling light penetration into the rat brain with Monte Carlo simulations. This work delivers a new perspective, including initial experimental and computational efforts on in vivo photopharmacology to understand and eventually treat neurological conditions.

The mining and metal processing industries are undergoing a transformation through digitization, with sensors and data analysis playing a crucial role in modernization and increased efficiency. Vibration sensors are particularly important in monitoring production infrastructure in metal processing plants. This paper presents the installation of vibration sensors in an actual industrial environment and the results of spectral vibration data analysis. The study demonstrates that vibration sensors can be installed in challenging environments such as metal processing plants and that analyzing vibration patterns can provide valuable insights into predicting machine failures and different machine states. By utilizing dimensionality reduction and dominant frequency observation, we analyzed vibration data and identified patterns that are indicative of potential machine states and critical events that reduce production throughput. This information can be used to improve maintenance, minimize downtime, and ultimately enhance the production process's overall efficiency. This study highlights the importance of digitization and data analysis in the mining and metal processing industries, particularly the capability not only to predict critical events before they impact production throughput and take action accordingly but also to identify machine states for legacy equipment and be part of retrofitting strategies.

Fouling is a phenomenon where material accumulates on the exterior of convective heat exchangers (HX) and other surfaces. In boilers fired by waste-derived or biomass fuels, these surfaces are cleaned frequently to maintain adequate heat transfer between the flue gas and fluid. However, excess cleaning of HX surfaces wastes money and resources, and the common practice of soot removal at fixed time intervals is not an optimal strategy. An adaptive timing method would be beneficial; however, real-time knowledge of HX condition is hard to obtain. In this paper, we present (1) a state estimation approach for fouling monitoring in a Circulating Fluidized Bed (CFB) boiler, fusing knowledge from a physical model with process measurement data, and (2) a novel condition monitoring scheme based on modal-vibrational sensing, with potential for a directly estimating the degree of fouling on heating surfaces. The results are demonstrated on a full-scale commercial CFB. Combining physical models, machine learning, and modal analysis in mutually supporting ways provides a solid basis for future sootblowing optimization efforts and improved fouling management.

Digitisation in the mining and metal processing industries plays a key role in their modernisation. Production processes are more and more supported by a variety of sensors that produce large amounts of data that meant to provide insights into the performance of production infrastructures. In the metal processing industry vibration sensors are essential in the monitoring of the production infrastructure. In this position paper we present the installation of vibration sensors in a real industrial environment and discuss the data quality issues we encountered while using such sensors.

Solar radiation is a challenge for laser-based daylight imaging since it decreases the signal-to-noise ratio (SNR) of the imaging. Here we demonstrate a micro-integrated external-cavity tapered diode laser system for daylight imaging. It emits light at a wavelength of 762 nm, chosen because of its overlap with an oxygen absorption band in the solar radiation spectrum. The integrated laser system consists of a tapered diode amplifier as gain medium and an external volume Bragg grating for spectrum stabilization and narrowing, thus a narrow bandpass optical filter can be used to improve the SNR further. The laser system can be operated in both continuous wave (CW) mode and pulsed mode by modulating the injected current to the amplifier. In CW mode operation, 1.3 W of output power is obtained with an emission spectral linewidth of 4 pm, and a beam propagation factor in the slow axis, M-2, of 1.7 (4 sigma). In pulsed mode operation with a trigger signal of a 50 mu s pulse width and a 10 kHz repetition rate, 2.0 W of peak output power is achieved with an emission spectral bandwidth of 0.2 nm, and an M2 in the slow axis of 1.9 (4 ). The modulation depth is almost 100%.

A speckle-displacement-based wavemeter is combined with a spatial-fundamental-mode-pass filter to eliminate the influence of multimode operation on the directionality of the resulting output from a distributed Bragg reflector (DBR) tapered laser. The proposed setup is characterized theoretically and experimentally, and detections of mode hops and side-mode suppression ratios (SMSRs) in the optical output are demonstrated. The laser illuminates a rough surface at an oblique angle, and a camera observes the corresponding speckle pattern from an almost identical back-scattering direction. As the wavelength of the laser shifts, the speckle pattern responds with a corresponding displacement, which is approximately linear with respect to the shift within the detection area. The wavemeter tracks continuously the shifts of the speckles pattern by tracking the peak of the covariance function of sequentially acquired images. In this way, the speckle-displacement-based wavemeter achieves a spectral resolution of 10.4 MHz. Mode hops in the laser do not cause any impeding decorrelation of the speckle patterns. Interestingly, the actual SMSR is related to the peak height and width of the absolute covariance function. A wavemeter, which is capable of measuring wavelengths, mode hops, and SMSRs, is highly useful for spectroscopy, quantum optics, nonlinear frequency conversion, and other applications requiring stable single-frequency laser light, especially when using diode lasers.

Laser radiation has been shown to be a promising approach for in situ amorphization, i.e., drug amorphization inside the final dosage form. Upon exposure to laser radiation, elevated temperatures in the compacts are obtained. At temperatures above the glass transition temperature (Tg) of the polymer, the drug dissolves into the mobile polymer. Hence, the dissolution kinetics are dependent on the viscosity of the polymer, indirectly determined by the molecular weight (Mw) of the polymer, the solubility of the drug in the polymer, the particle size of the drug and the molecular size of the drug. Using compacts containing 30 wt% of the drug celecoxib (CCX), 69.25 wt% of three different Mw of polyvinylpyrrolidone (PVP: PVP12, PVP17 or PVP25), 0.25 wt% plasmonic nanoaggregates (PNs) and 0.5 wt% lubricant, the effect of the polymer Mw on the dissolution kinetics upon exposure to laser radiation was investigated. Furthermore, the effect of the model drug on the dissolution kinetics was investigated using compacts containing 30 wt% of three different drugs (CCX, indomethacin (IND) and naproxen (NAP)), 69.25 wt% PVP12, 0.25 wt% PN and 0.5 wt% lubricant. In perfect correlation to the Noyes–Whitney equation, this study showed that the use of PVP with the lowest viscosity, i.e., the lowest Mw (here PVP12), led to the fastest rate of amorphization compared to PVP17 and PVP25. Furthermore, NAP showed the fastest rate of amorphization, followed by IND and CCX in PVP12 due to its high solubility and small molecular size.

We present the use of the Douglas-Gunn Alternating Direction Implicit finite difference method for computationally efficient simulation of the electric field propagation through a wide variety of optical fiber geometries. The method can accommodate refractive index profiles of arbitrary shape and is implemented in a tool called BPM-Matlab. We validate BPM-Matlab by comparing it to published experimental, numerical, and theoretical data and to commercially available state-of-the-art software. It is user-friendly, fast, and is available open-source. BPM-Matlab has a broad scope of applications in modeling a variety of optical fibers for diverse fields such as imaging, communication, material processing, and remote sensing.

Cardiovascular disease is one of the leading causes of death in the United States and obesity significantly increases the risk of cardiovascular disease. The measurement of blood pressure (BP) is critical in monitoring and managing cardiovascular disease hence new wearable devices are being developed to make BP more accessible to physicians and patients. Several wearables utilize photoplethysmography from the wrist vasculature to derive BP assessment although many of these devices are still at the experimental stage. With the ultimate goal of supporting instrument development, we have developed a model of the photoplethysmographic waveform derived from the radial artery at the volar surface of the wrist. To do so we have utilized the relation between vessel biomechanics through Finite Element Method and Monte Carlo light transport model. The model shows similar features to that seen in PPG waveform captured using an off the shelf device. We observe the influence of body mass index on the PPG signal. A degradation the PPG signal of up to 40% in AC to DC signal ratio was thus observed.

We report four-wave mixing with different polarization and spatial modes in a single 4H-silicon carbide photonic device. Our device shows great potential to perform high-dimensional multiplexing for optical communication and high-dimensional entanglement in quantum networks. We use a polarization-insensitive grating coupler and a multimode microring resonator that supports three polarization and spatial mode resonances. Finally, we show the polarization dependence of the third-order nonlinearity of 4H-silicon carbide. The measured nonlinear refractive index of the light polarized along the extraordinary axis, which is n2,TM = (13.1 ± 0.7) × 10−19 m2/W, is twice as large as that of the light polarized along the ordinary plane, n2,TE = (7.0 ± 0.3) × 10−19 m2/W, indicating that the extraordinary polarization is more efficient for nonlinear experiments in the 4H-silicon carbide integrated platforms as compared to the ordinary polarization.

The erratum corrects an error in the originally provided equation for ΔT.

Laser diodes, in general, are sensitive to optical feedback, especially with regard to maintaining single-frequency operation. Until now, however, the feedback sensitivity of high-power devices such as single-frequency distributed Bragg reflector (DBR) tapered laser diodes has not been investigated in quantitative detail. In this paper, we analyze the impact of very weak optical feedback between − 105 d B and − 40 d B on a high-power DBR tapered laser diode. The measurement setup is validated using a typical DFB laser diode. The results are in good agreement with the theory at low-feedback levels.

4H‐silicon carbide (SiC) integrated platforms have shown great potential in quantum and nonlinear photonics. However, the thermal properties of 4H‐SiC waveguides are still unknown, even though thermo‐optic effects can play an important role in fundamental measurements and practical applications. Herein, the thermo‐optic effects in a 4H‐SiC microring resonator are comprehensively studied, by means of both temperature tuning and self‐heating. The thermo‐optic coefficient and the ratio between the thermal absorption and the thermal diffusion of 4H‐SiC are quantitatively measured to be and , respectively. Considering the acquired thermal properties, Kerr‐nonlinearity‐based dual‐pump optical parametric oscillation (OPO) is experimentally achieved, and thus, it is demonstrated that broadband solitons can feasibly be generated through thermal tuning of 4H‐SiC‐on‐insulator (SiCOI) microring resonators.

Continuous monitoring of Blood Pressure (BP) is desirable in the management of cardiovascular disease (CVD). Novel tools are exploring Photoplethysmography (PPG) to determine a patient BP. We utilized a Monte Carlo (MC) framework to connect the cardiovascular biomechanics and light transport associated with a PPG signal. Optical properties specific of obese and non-obese groups were used to determine their influence on the PPG waveform. Our simulation shows that the PPG signal is altered in individuals suffering from obesity, which could limit their use in BP monitoring.

SINTEF is developing a flash lidar breadboard for use in space rendezvous operations. This is funded by ESA through the E3P-Expert program. The lidar is based on a 1.3-megapixel gate-able CMOS silicon sensor and a 532nm diode-pumped, Q-switched MOPA laser. The main case in this project is to detect and track a container with samples from Mars - a 280mm diameter, non-cooperative grey ball - at ranges up to 3km. Possible other applications include recovery of spacecraft or space junk and hazard detection during landing operations. If successful, a flash lidar might become part of the Mars Sample Recovery program. A green laser makes it possible to use a high-resolution silicon image sensor. The laser is very compact: 1.3 liters, 2.3kg and draws 48W at 400Hz. It operates from single shot to 1kHz with pulses up to 4 mJ.

Attenuation of optical fields owing to scattering and absorption limits the penetration depth into tissue. Whilst aberration correction may be used this is difficult to implement over a large field of view in heterogeneous tissue. Recently, the novel approach of attenuation-compensation of propagation-invariant light fields has shown increase in depth penetration for light-sheet microscopy. Here we show this powerful approach may be implemented in a facile manner utilizing a graded neutral density filter circumventing the need for expensive beam shaping apparatus. A ‘gold standard’ system utilizing a spatial light modulator for beam shaping is used to benchmark our low-cost implementation.

Systolic and diastolic blood pressure values can be used as an indicator of an individual’s risk for cardiovascular disease. The common practice of blood pressure (BP) measurement using a cuff-based system provides a snapshot of blood pressure at a single instance in time and can be inconvenient and intrusive. The development of optical methods to determine blood pressure could provide continuous monitoring of blood pressure through techniques such as pulse transit time (PTT) or pulse arrival time (PAT) when used with echocardiogram. Cuff based BP devices are known to have variation and inaccuracies when applied to larger arm sizes as seen in individuals with obesity but little is known of the influence of obesity in the PPG/PTT and PAT signals. We propose that accurate waveform replication is required for the derivation of blood pressure applied to individuals with obesity. Here we use the Monte Carlo framework to develop the PPG waveform as a means to derive blood pressure through cuff less techniques. The development of a simulated waveform incorporates realistic changes in the artery related to its biomechanical properties as a pressure wave is propagated through the vessel. It is shown that a change in vessel pressure and geometry directly affects the captured optical signal. The system can account for variations in body-mass index to compensate for geometrical changes in adipose tissue layer and changes in optical properties.

Phase retrieval is a highly useful technique that allows the calculation of the complex electric field of a beam of spatially coherent radiation based only on recordings of intensity profiles with a camera. In this work, we demonstrate what we believe, to the best of our knowledge, is a new technique for single-beam multiple-intensity phase retrieval based on simultaneous propagations that provides improved fidelity results compared to standard methods (0.9931 compared to 0.9646) and a 34 dB reduction in background noise level. The implementation is fast, open source, user friendly, and can be run on either CPUs or GPUs. It is available for download at https://gitlab.gbar.dtu.dk/biophotonics/PhaseRetrieval.

In laser lighting, a major benefit over other lighting techniques is the possibility to achieve very high luminous exitance. Focusing the exciting laser to a very small spot size on the phosphor, however, does not necessarily provide a very small emitting area for the white light. In this study we investigate experimentally and numerically the relationship between the white light spot size and the incident blue laser spot size. We show that the specific phosphor material properties have significant impact on this relationship and on the achievable minimum spot size. This constitutes a limitation on the minimum spot size achievable in laser lighting and has important implications in applications.