Diode Laser Sensor Research Articles

Integrated Pacemaker System with Piezoelectric Energy Harvesting and Laser-Based Heartbeat Abnormality Detection

Cardiovascular diseases remain the leading cause of mortality globally, highlighting the critical need for innovative cardiac care technologies. This study presents an advanced pacemaker system integrating piezoelectric energy harvesting, chemical sensors, and laser-based heartbeat abnormality detection. By converting body thermal and mechanical energy into electrical power, the system ensures continuous operation. The integration of diode laser sensors provides non-invasive, real-time monitoring of blood flow and oxygen saturation, enabling early detection of arrhythmias. A mobile application supports remote monitoring and emergency alerts, enhancing patient safety. The system's novel architecture aims to reduce surgical interventions and improve cardiac outcomes, setting a benchmark for future advancements in biomedical engineering.

On the determination of the standing oblique detonation wave in an engine combustor using laser absorption spectroscopy of hydroxyl radical

Freejet experiments were conducted in the hypersonic flight-duplicated shock tunnel (JF-12) to understand the detonation combustion mode in the combustor of a standing oblique detonation ramjet (Sodramjet) engine prototype. Besides the traditional schlieren imaging to capture the oblique shock positions in the combustor, we implemented laser absorption spectroscopy of hydroxyl (OH) radical with three laser beams around the shock front. The Sodramjet engine combustor provides an ideal condition to measure OH because its molar fraction within the detonation front is estimated to exceed 0.03, which is much higher than other combustors. However, the harsh environment of freejet shock tunnel test poses a great challenge to the reliability of measurement systems. In this work, near-infrared tunable laser diode sensors centered at 1528 nm were chosen to measure the line-of-sight average of OH partial pressure. Continuous absorption measurements were conducted near the shock front, indicating a thin OH region after shock compression that could only be achieved by detonation combustion. The time-varied OH partial pressure was well predicted by the computational fluid dynamics (CFD) prediction. Our measurement results verified the detonation combustion of Sodramjet engine prototype and showed that in situ, real-time detonation diagnostics based on laser absorption spectroscopy is possible in freejet experiments of shock tunnel.

Development of combustion gas measurement systems for micro-rocket torch using a diode laser sensor

Development of combustion gas measurement systems for micro-rocket torch using a diode laser sensor

A sensor based on high-sensitivity multi-pass resonant photoacoustic spectroscopy for detection of hydrogen sulfide

A high-sensitive tunable diode laser sensor based on photoacoustic spectroscopy and multi-pass absorption spectroscopy is developed for hydrogen sulfide (H2S) detection using a target absorption line at 6287.005 cm−1. Two spherical concave mirrors are utilized as the reflectors to make the laser beam pass through the photoacoustic cell for 24 times. The wavelength modulation spectroscopy technique with second harmonic detection (WMS-2f) method is employed to reduce external interference and increase the detection sensitivity. With the enhancement of the effective laser power in the multi-pass PA cell, the photoacoustic 2f signal of the target H2S absorption line has a ∼ 8 times improvement compared to the sensor system without multi-pass cell. Based on the results of Allan variance analysis, the minimum detection concentration of the system could reach 0.68 ppm with a 10-s average time and it can be further lowered down to ∼ 0.1 ppm when a 1-minute averaging time is used. The linear responsivity of the multi-pass PA spectroscopy sensor is estimated to be ∼ 0.00112 mV/ppm by linear fitting for a continuous flow gas measurement results. The excellent performance validates the potential of the sensor for field application.

A microfluidic serial dilutor (MSD): Design optimization and application to tuning of liposome nanoparticle preparation

Dilution of a sample over several orders of magnitude in concentration is a routine procedure in many analytical, bioanalytical, diagnostics, and formulation laboratories. Microfluidics offer the opportunity to automate the dilution procedure with many successful designs to be found in literature, yet fast microfluidic generation of a dilution series over several orders of magnitude remains so far unaddressed. This study realized a microfluidic serial dilutor (MSD) having up to 4 outlets and able to generate fast a serial dilution of a sample up to 4 orders of magnitude. The core design based on a cascade dilution of sample to diluent in a 1:10 volume ratio was fully characterized experimentally and using Computational Fluid Dynamics (CFD). The MSD was interfaced with a new absorbance measuring device based on a laser diode and spectral sensor, which enabled evaluating the dilution performance and confirming the effectiveness of the design. The MSD was applied to the synthesis of liposome nanoparticles by solvent diffusion method, enabling fine-tunning of synthesis of a popular drug and vaccine delivery microcarrier on a wide range of sizes by simply adjusting the flow rate and flow rate ratio. The MSD design showed to be simple, reliable, with operation at reduced pressure drops, and delivery of highly reproducible results.

An Infrared Laser Sensor for Monitoring Gas-Phase CO2 in the Headspace of Champagne Glasses under Wine Swirling Conditions

In wine tasting, tasters commonly swirl their glasses before inhaling the headspace above the wine. However, the consequences of wine swirling on the chemical gaseous headspace inhaled by tasters are barely known. In champagne or sparkling wine tasting, starting from the pouring step, gas-phase carbon dioxide (CO) is the main gaseous species that progressively invades the glass headspace. We report the development of a homemade orbital shaker to replicate wine swirling and the upgrade of a diode laser sensor (DLS) dedicated to monitoring gas-phase CO in the headspace of champagne glasses under swirling conditions. We conduct a first overview of gas-phase CO monitoring in the headspace of a champagne glass, starting from the pouring step and continuing for the next 5 min, with several 5 s swirling steps to replicate the natural orbital movement of champagne tasters. The first results show a sudden drop in the CO concentration in the glass headspace, probably triggered by the liquid wave traveling along the glass wall following the action of swirling the glass.

Spectral Processing of Self-Mixing Interferometric Signal Phase for Improved Vibration Sensing Under Weak- and Moderate-Feedback Regime

In this paper, spectral processing of laser Self-Mixing (SM) interferometric signal phase has been carried out allowing better measurement accuracy for harmonic and arbitrarily shaped vibrations for an optical feedback based SM interferometric Laser Diode (LD) sensor. The resulting algorithm not only improves the measurement accuracy but also reduces the processing time (by a factor 3.45) as compared with a previous time-domain based displacement retrieval technique called the Phase Unwrapping Method (PUM). Fourier series based analysis of laser feedback phase is carried out to determine processing limits. The proposed algorithm has also been found to be robust against variation in optical feedback coupling C as well as additive noise. This use of spectral analysis not only increases the measurement accuracy but also retrieves information about target movement harmonics which can also be used in modal analysis applications of remote mechanical targets. Using an SM vibration sensor based on a LD emitting at 785 nm, this technique has provided an average RMS error of 12.5 nm (while that of PUM is 39 nm RMS) for harmonic target vibrations of $5~\mu \text{m}$ amplitude. For reduced range of $1 , an average RMS error of ~8 nm ( $\sim \lambda $ /100) is obtained.

OH radical measurements in combustion environments using wavelength modulation spectroscopy and dual-frequency comb spectroscopy near 1491 nm

Hydroxyl radical (OH) is a key intermediate reactive species during combustion processes relevant to power production, transportation, and manufacturing. We demonstrate an OH sensor based on in situ laser absorption spectroscopy for deployment in industrial conditions. The sensor relies on telecommunications-fiber-coupled, tunable-diode-laser absorption spectroscopy of an OH transition near 1491 nm. By employing wavelength modulation spectroscopy, the sensor is capable of in situ, quantitative detection of OH down to mole fraction values of 10−5 over a 75-cm pathlength. To increase the accuracy of the OH sensor, we perform the first dual-comb spectroscopy measurement above a flame and use the results to create an absorption database of water vapor transitions from 1489.2 to 1492.5 nm at temperatures up to 2165 K. The database is included in the analysis procedure for the tunable diode laser sensor to account for the water vapor absorption that overlaps with the OH absorption. The utility of the laser sensor is demonstrated by characterizing the concentration of OH radical above a catalytic combustor under different operating conditions.

Development of a tunable diode laser sensor for CO concentration analysis at laboratory-scale conditions for in situ combustion tests of heavy crude oils.

A tunable diode laser-based sensor is reported to monitor carbon monoxide (CO) concentration under conditions similar to those of laboratory-scale tests used to characterize the behavior of heavy crude oil during in situ combustion (ISC). The sensor uses a DFB diode laser operating over the spectral range of the rotational transition R(11) of the first overtone, wherein simulations of spectral absorption bands for CO, CO2, and H2O showed minimal spectral interference. The absorption spectra were calculated using the HiTran 2008 database at temperatures varying between 150°C and 800°C, pressures from 1 to 5atm, and the typical concentration of major species in ISC characterization experiments. The measurements of CO concentration were conducted at ambient temperature and pressure in a static glass cell of borosilicate, with a path length of 3.81cm, to validate the CO sensor architecture under controlled laboratory environments. The calibration curve for CO obtained by quantifying the optical density at the line center of R(11) for a molar-concentration range between 0.7% and 3.4% demonstrated a linear response (coefficient of determination of 0.9986). Experiments at 4atm and 600K were carried out in a custom-designed optical chamber with two optical wedged sapphire windows (2°) to avoid the etalon effect. CO-absorption spectra were validated by a comparative study with the HiTran database, while a calibration-free methodology using scanned-wavelength direct absorption was investigated for future characterizing experiments involving ISC. Signal to noise ratios (SNRs) were above 40 in the optical chamber and higher than 14 in the glass cell. The TDL sensor was also successfully validated during real ISC experiments involving Colombian heavy crude oil. The calibration and oxidation experiments showed the potential of TDL-based sensors in the region of 2.3μm for non-invasive, real-time, and in situ measurements of carbon monoxide generated at similar conditions to those of lab-scale experimental ISC tests.

Laser based measurement of water film thickness for the application in exhaust after-treatment processes

In this work, an absorption based laser sensor for the investigation of dynamically changing liquid film thicknesses is developed and validated. For the wavelength selection of the single-ended, fibre-coupled, diode-laser sensor, near-infrared spectra of liquid water are measured at various thicknesses and temperatures. To reduce the influence of the film temperature, the evaluation is supported by a calibration procedure. Unknown film thicknesses of up to 440 µm could then be measured. To adapt the sensor to particular boundary conditions of different systems, the single-ended setup can be changed to a transmissive configuration. The sensor is validated in both configurations against a commercially available chromatic confocal resonance (CHR) sensor. A comparison with respect to the CHR sensor leads to an accuracy of 2.8 µm and a precision of 3.9% of the new laser based sensor.

DESIGN OF DETECTION DEVICE FOR CU CONTAMINATED WATER USING RED DIODA LASER AND PHOTODIODA SENSOR

<p class="abstrak">The research on making detection system of Cu contaminated water based on red diode laser and photodiode sensor has been done. The purpose of this research was to know the characteristic of photodiode sensor, to make and to test the detection system of Cu contaminated water based on red diode laser and photodiode sensor. This research was conducted in five phases: characterization of photodiode sensor, making data acquisition system, processing and analyzing of training sample data, making of the detection system, and implementation of detection system on test samples. The results of research showed that photodiode sensor used in this research has transfer function of V = 0,0156 * I + 1,1897 with relation of input-output was very strong (r = 0,989); sensitivity was 0,0156 volts / lux; repeatability was 98,31 %; and saturation for the light intensity >200 lux. Meanwhile, the success rate of detection system implementation on Cu contaminated water was 97,5 %.</p>

Experimental Study of Broadening Coefficients for the v3 Band of CO by Tunable Diode Laser Spectroscopy

A diode laser sensor based on absorption spectroscopy is developed for measurement of self-broadening coefficients for the three lines of v3 band of CO at high temperature. the spectra of CO at 6390.8152 cm-1, 6393.1767 cm-1 and 6395.4312 cm-1 at temperatures ranging from 323K to 873K with different pressures are recorded. The line widths are acquired by the line shape fittings based on Voigt function, and the collitional broadening coefficients and temperature dependences of the three lines are also derived.

Development and validation of a diode laser sensor for gas-phase CO2 monitoring above champagne and sparkling wines

Champagne and sparkling wines are multicomponent hydroalcoholic systems supersaturated with dissolved carbon dioxide (CO2). Under standard tasting conditions, CO2 progressively invades the headspace above glasses, thus progressively modifying the chemical headspace perceived by the consumer. Monitoring in situ, and as accurately as possible the level of gas-phase CO2 above liquid is therefore a challenge of importance aimed at better understanding the close relationship between the release of gas-phase CO2 and a collection of various parameters such as glass-shape, and champagne temperature, for example. The development and validation of an instrument which combines two infrared diode lasers coupled with an optical fiber and devoted to real-time monitoring of gas-phase CO2 above sparkling beverages are reported. A first set of data showing the impact of liquid phase temperature on the release of gas-phase CO2 found in the headspace of champagne glasses is presented.

Detection System Design for Cu Contaminated Water Based on Red Diode Laser and LDR (Light Dependent Resistor) Sensor

The research on making detection system of Cu contaminated water based on red diode laser and LDR sensor has been done. The purpose of this research was to know the characteristic of LDR sensor, to make the detection system of Cu contaminated water, and to test the detection system of Cu contaminated water. This research was conducted in five phases: characterization of LDR sensor, making data acquisition system, processing and analyzing of train sample data, making detection system, and implementation of detection system on test sample. The result of LDR sensor characterization in this research showed transfer function V = 0,004I + 2,1861 with relation of input-output relation which was very strong (r = 0,99267); sensitivity was 0,004 volt/lux; repeatability was 99,015%, and saturation for the light intensity ˃ 500 lux. Meanwhile, the succes rate of detection implementation on Cu contaminated water was 97,5%.

An open-path tunable diode laser absorption spectrometer for detection of carbon dioxide at the Bonanza Creek Long-Term Ecological Research Site near Fairbanks, Alaska

We have developed a low-power, open-path, near-infrared (NIR) tunable diode laser sensor for the measurement of near ground-level concentrations of greenhouse gases. Here, we report on instrument design, characterization, and initial measurements of carbon dioxide concentrations during deployment to a thermokarst collapse scar bog near Fairbanks, AK (USA). The optics “launch-box” portion of the instrument couples radiation from an NIR, distributed feedback diode laser operating near 1572 nm with a visible laser for alignment purposes. The outgoing beam is directed through a 3.2-mm hole in a parabolic mirror and the launch-box is oriented using a two axis, altitude-azimuth telescope mount such that the beam strikes a retroreflector target at a set distance downfield. The beam then retraces the path back to the launch-box where the light is collected on the surface of the parabolic mirror and focused onto a multimode fiber that transfers the radiation to an InGaAs detector. Sweeps over a ~1.6 cm−1 spectral region were collected at a rate of 500 scans per second and were typically stored as 10 s sweep averages. These averaged sweeps could be individually spectrally fit for CO2 concentration or averaged into a single spectrum for fitting (after correction for slight frequency drift). Field data reported here was averaged for 2.5 min and was found to follow trends in diurnal cycles of CO2 concentration cycles reported by sensors located nearby in the field site.

Measurement of CO2 concentration at high-temperature based on tunable diode laser absorption spectroscopy

A diode laser sensor based on absorption spectroscopy has been developed for sensitive measurement of CO2 concentration at high-temperature. Measurement of CO2 can provide information about the extent of combustion and mix in a combustor that may be used to improve fuel efficiency. Most methods of in-situ combustion measurement of CO2 use the spectroscopic parameters taken from database like HITEMP which is mainly derived from the theoretical calculation and remains a high degree of uncertainty in the spectroscopic parameters. A fiber-coupled diode laser system for measurement of CO2 in combustion environment by use of the high-temperature spectroscopic parameters which are obtained by experiment was proposed. Survey spectra of the R(50) line of CO2 at 5007.787cm−1 were recorded at high-temperature and various pressures to determine line intensities. The line intensities form the theoretical foundation for future applications of this diode laser sensor system. Survey spectra of four test gas mixtures containing 5.01%CO2, 10.01%CO2, 20.08%CO2, and 49.82%CO2 were measured to verify the accuracy of the diode laser sensor system. The measured results indicate that this sensor can measure CO2 concentration with 2% uncertainty in high temperatures.

Robust Detection of Non-Regular Interferometric Fringes From a Self-Mixing Displacement Sensor Using Bi-Wavelet Transform

An innovative signal processing method based on custom-made wavelet transform (WT) is presented for robust detection of fringes contained in the interferometric signal of self-mixing (SM) laser diode sensors. It enables the measurement of arbitrarily-shaped vibrations even in the corruptive presence of speckle. Our algorithm is based on the pattern recognition capability of bespoke WTs for detecting SM fringes. Once the fringes have been correctly detected, phase unwrapping methods can be applied to retrieve the complete instantaneous phase of the SM signals. Here, the novelty consists in using two distinct mother wavelets $\Psi _{r}$ ( ${t}$ ) and $\Psi _{d}$ ( ${t}$ ) specifically designed to distinguish SM patterns as well as the displacement direction. The peaks, i.e. the maxima modulus of WT, then allow the detection of the fringes.

Characterization of CO2 flow in a hypersonic impulse facility using DLAS

This work documents diode laser absorption measurements of CO2 flow in the free stream of the Longshot hypersonic impulse facility at Mach numbers ranging from 10 to 12. The diode laser sensor was designed to measure absorption of the P12 (30013) \(\leftarrow\) (00001) transition near 1.6 \(\upmu\)m, which yields relatively weak direct absorption levels (3.5 % per meter at peak Longshot free-stream conditions). Despite this weak absorption, measurements yielded valuable flow property information during the first 20 ms of facility runs. Simultaneous measurements of static temperature, pressure, and velocity were acquired in the inviscid core flow region using a laser wavelength scanning frequency of 600 Hz. The free-stream values obtained from DLAS measurements were then compared to Longshot probe-derived values determined from settling chamber and probe measurements. This comparison enabled an assessment of the traditional method of flow characterization in the facility, which indicated negligible influence from possible vibrational freezing of reservoir gases.

Fiber-coupled diode-laser sensors for calibration-free stand-off measurements of gas temperature, pressure, and composition.

A fiber-coupled near-infrared diode-laser sensor for stand-off measurements of gas temperature, pressure, and composition is presented. This sensor utilizes a fiber bundle with six multimode catch fibers surrounding one single-mode pitch fiber to transmit and receive backscattered laser light in a handheld transmitter/receiver. Scanned-wavelength-modulation spectroscopy with 1f-normalized 2f-detection and fast (80-200 kHz) wavelength modulation were used to provide calibration-free measurements and reduce the influence of spurious cavity noise formed by the overlapping transmitted and reflected laser light. Demonstrations include two-color measurements of temperature, pressure, and H(2)O near 1.4 μm in a propane flame at 2 kHz (SNR=200) and measurements of CH(4) near 1.65 μm (SNR=20 to 1500) at stand-off distances of 15 cm and 10 m, respectively. The fraction of photons collected ranged from 10(4) to 1 parts per million at stand-off distances from 10 cm to 10 m, respectively, and is similar for aluminum and paper reflectors.

Subsonic In-Flight Temperature and Pressure Measurements Using a Scramjet Inlet Flow Sensor

The performance of a scramjet inlet sensor based on tunable diode laser absorption spectroscopy of oxygen in the A-band near 760 nm during a low-altitude, subsonic flight test is discussed. Though the scramjet did not reach the targeted hypersonic flight regime due to the malfunction of the first-stage booster, analysis of the spectral absorption data acquired during the descent flight below 3 km successfully determined pressure and temperature in the inlet and demonstrated that the system was capable of producing an adequate signal-to-noise ratio to allow temperature, pressure, and velocity measurements under the expected hypersonic flight conditions at altitudes up to at least 30 km. This is the first flight-tested tunable diode laser sensor for a scramjet inlet flow, and the robustness and stability of the sensor design in dynamic load conditions were made evident by the quality of the data recorded after a very unstable and high- launch scenario.