1064-nm Wavelengths Research Articles

Laser terapêutico associado ou não ao óleo de andiroba no tratamento de feridas cutâneas por segunda intenção em ratos Wistar

This study’s objective was to evaluate the efficacy of treating cutaneous wounds in Wistar rats using a therapeutic laser alone or in combination with topical application of andiroba oil. Twenty-four Wistar rats were distributed into three groups (T4, T7, and T14) of eight animals. To prepare the wounds, a total of four skin fragments per animal were removed using an 8-mm cutaneous biopsy punch. Each animal was inflicted with four surgical wounds, and each wound was subjected to one treatment. The treatments were as follows: saline solution (control, Cn); laser therapy (L), using a 660-nm laser wavelength and 10-J/cm² energy density; fresh andiroba oil (An); laser therapy followed by topical andiroba oil administration (LAn). All treatments in all animals were conducted for 4- (T4), 7- (T7), and 14- (T14) day periods. Edema and purulent secretion were observed in three animals in the An group, and the appearance of an exuberant crust was also observed in one animal from the same group. The LAn group presented the worst wound healing rate and contraction velocity (p < 0.05). Microscopically, there was no difference between groups regarding the presence of inflammation, necrosis, formation of granulation tissue, fibroplasia, and the presence of types 1 and 3 collagen at different treatment times. It was concluded that laser treatment of cutaneous wounds in conjunction with andiroba oil application did not present benefits in reference to the 0.9% NaCl.

Optimization of time domain diffuse correlation spectroscopy parameters for measuring brain blood flow.

.Significance: Time domain diffuse correlation spectroscopy (TD-DCS) can offer increased sensitivity to cerebral hemodynamics and reduced contamination from extracerebral layers by differentiating photons based on their travel time in tissue. We have developed rigorous simulation and evaluation procedures to determine the optimal time gate parameters for monitoring cerebral perfusion considering instrumentation characteristics and realistic measurement noise.Aim: We simulate TD-DCS cerebral perfusion monitoring performance for different instrument response functions (IRFs) in the presence of realistic experimental noise and evaluate metrics of sensitivity to brain blood flow, signal-to-noise ratio (SNR), and ability to reject the influence of extracerebral blood flow across a variety of time gates to determine optimal operating parameters.Approach: Light propagation was modeled on an MRI-derived human head geometry using Monte Carlo simulations for 765- and 1064-nm excitation wavelengths. We use a virtual probe with a source–detector separation of 1 cm placed in the pre-frontal region. Performance metrics described above were evaluated to determine optimal time gate(s) for different IRFs. Validation of simulation noise estimates was done with experiments conducted on an intralipid-based liquid phantom.Results: We find that TD-DCS performance strongly depends on the system IRF. Among Gaussian pulse shapes, pulse length appears to offer the best performance, at wide gates (500 ps and larger) with start times 400 and 600 ps after the peak of the TPSF at 765 and 1064 nm, respectively, for a 1-s integration time at photon detection rates seen experimentally (600 kcps at 765 nm and 4 Mcps at 1064 nm).Conclusions: Our work shows that optimal time gates satisfy competing requirements for sufficient sensitivity and sufficient SNR. The achievable performance is further impacted by system IRF with quasi-Gaussian pulse obtained using electro-optic laser shaping providing the best results.

Optical and Morphological Properties of Silver Nanoparticles Synthesis by Q-Switched Nd-YAG Laser

Abstract. Laser ablation of a silver target immersed in distilled water utilizing Nd: YAG laser with wavelengths of 532nm,1064nm, and 1320nm was carried out to fabricate silver nanoparticles. The synthesis of Ag NPs was carried out using various laser energy (200-1000 mJ) and different pulses (200-1000 pulse). Optical properties for the Ag nanoparticles solution were tested using UV-Visible spectrum, while the morphological properties for the Ag-nanoparticles solution after deposited on glass were tested using the atomic force microscope (AFM). The results showed that the synthesis of the Ag-nanoparticles using pulsed laser ablation in liquid (PLAL) (water) gives nanoparticles with homogeneous grain distribution and uniform surface roughness. It was found that the absorption peaks of Ag NPs increase by increasing the number of pulses shoot for the same laser wavelength and laser energy, and the reported maximum value of absorption peak is 0.363 when using 1000 pulses shoot. AFM results showed that the average diameter of the Ag NPs prepared by PLAL increases with increasing the laser wavelength. However, when using laser wavelengths of 1320nm,1064nm, and 532nm, the resulted average diameter of silver nanoparticles will be 55.38nm, 34.18nm, and 30.3nm, respectively. Finally, the average surface roughness of the Ag NPs prepared by PLAL increased with increasing the laser wavelength. The obtained average surface roughness of silver nanoparticles when using wavelengths of 1320nm,1064nm, and 532nm were 2.75nm, 1.19nm, and1.06nm, respectively.

Spectroscopic Investigation of Laser-Produced Strontium Plasma Using Fundamental and Second Harmonics of Nd:YAG Laser

In the present work, our main focus is to find out an optical window where the plasma is optically thin and the plasma parameters can be determined more reliably. The strontium plasma was generated using the fundamental (1064 nm) and the second harmonic (532 nm) of a Q-switched Nd:YAG laser. The spectra were registered using a set of five miniature spectrometers covering the spectral range from 200 to 720 nm. The intensity ratios of some specific lines have been compared with the theoretically calculated intensities to check the validity of optically thin plasma, free from self-absorption and in local thermodynamic equilibrium. In the selected optical window, the electron number densities have been determined from the Stark broadened line profiles, and the excitation temperatures have been calculated using the Boltzmann plot method for 1064- and 532-nm laser wavelengths. The variations in the electron number density and excitation temperature have been studied as a function of laser energy (8-100 mJ), atmospheric pressure (100-600 mbar), and spatial distribution of the plasma plume (0.5-4.0 mm) for both the lasers. The electron number density is found to be higher for the 532-nm laser than the 1064-nm laser, while the excitation temperature is higher for the 1064-nm laser than the 532-nm laser. We have fitted a power law on the experimental data to analyze the varying trends of excitation temperature.

Could the photobiomodulation therapy induce angiogenic growth factors expression from dental pulp cells?

This study aimed to evaluate the effect of different photobiomodulation (PBM) radiant exposures on the viability, proliferation, and gene expression of pulp fibroblasts from human primary teeth (HPF) involved in the pulp tissue repair. HPF were irradiated with Laser InGaAlP (Twin Flex Evolution, MMOptics®) at 660-nm wavelength (red); single time, continuous mode, 0.04-cm2 laser tip area, and 0.225-cm laser tip diameter, keeping the distance of 1 mm between the laser beam and the cell culture. The doses used were between 1.2 and 6.2 J/cm2 and were evaluated at the 6 h, 12 h, and 24 h after PBM. MTT and crystal violet assays evaluated the cell viability and proliferation. RT-PCR verified VEGF and FGF-2 mRNA expression. A blinded examiner analyzed the data through two-way ANOVA followed by Tukey test (p < 0.05). The groups with higher powers (10 mW, 15 mW, 20 mW, and 25 mW), shortest application periods (10 s), and radiant exposures between 2.5 and 6.2 J/cm2 exhibited statistically higher viability than that of the groups with small power (5 mW), longer application period (50 s), and radiant exposure of 6.2 J/cm2 (p < 0.05). VEGF and FGF-2 mRNA expression were observed at the three evaluated periods (6 h, 12 h, and 24 h) and the highest expression was in the shortest period (p < 0.05). All radiant exposures maintained HPF viable. The period of 6 h after irradiation showed statistically greater gene expression for both growth factors than other periods. VEGF mRNA had no differences among the dosimetries studied. The best radiant exposures for FGF-2 gene expression were 2.5 J/cm2 and 3.7 J/cm2.

Comprehensive Study and Experimental Validation of U-shaped Probe Extrinsic Fiber Optic Sensor for the Measurement of Refractive Index at Various Temperatures using a Tunable Light Source

Extensive detection performances due to sensitivity to external and internal perturbations in the fiber structure makes the optical fiber sensors highly superior over the conventional sensors. The fiber optic sensors with clad removed fibers at some portion along its length play a vital role in the determination of refractive index of various liquids at several wavelengths and at several temperatures. In the present paper a refractive index sensor has been developed to investigate the performance and experimental validation in the measurement of R.I. values of liquids at various temperatures using a tunable light source capable of emitting light at the wavelengths of 630nm, 660nm, 820nm and 850nm. The U-shaped glass probe connected between the tunable light source and an optical detector using two multimode PCS fibers of 200/230μm, acts as a clad removed portion of the sensor which is called as sensing zone or sensing region. In the working principle of the sensor, the U-shaped glass rod immersed into each mixture prepared with the combination of Toluene and Acetonitrile, the light launched from the source reaching the detector was noted at various temperatures and by tuning the wavelength of the source to 630nm, 660nm, 820nm and 850nm. From the data obtained, the sensor was calibrated to measure the refractive index of various liquids at different temperatures and wavelengths. Exploiting all the advantages offered by the fiber optic communication systems, the sensor was expected to be rugged, robust, reliable, and durable offering the sensitivity in the range of the order of 10-5.

Enhanced cavity coupling to silicon vacancies in 4H silicon carbide using laser irradiation and thermal annealing

The negatively charged silicon monovacancy [Formula: see text] in 4H silicon carbide (SiC) is a spin-active point defect that has the potential to act as a qubit in solid-state quantum information applications. Photonic crystal cavities (PCCs) can augment the optical emission of the [Formula: see text], yet fine-tuning the defect-cavity interaction remains challenging. We report on two postfabrication processes that result in enhancement of the [Formula: see text] optical emission from our PCCs, an indication of improved coupling between the cavity and ensemble of silicon vacancies. Below-bandgap irradiation at 785-nm and 532-nm wavelengths carried out at times ranging from a few minutes to several hours results in stable enhancement of emission, believed to result from changing the relative ratio of [Formula: see text] ("dark state") to [Formula: see text] ("bright state"). The much faster change effected by 532-nm irradiation may result from cooperative charge-state conversion due to proximal defects. Thermal annealing at 100 °C, carried out over 20 min, also results in emission enhancements and may be explained by the relatively low-activation energy diffusion of carbon interstitials [Formula: see text], subsequently recombining with other defects to create additional [Formula: see text]s. These PCC-enabled experiments reveal insights into defect modifications and interactions within a controlled, designated volume and indicate pathways to improved defect-cavity interactions.

Effect of low-level laser irradiation on cytotoxicity of benzene in human normal fibroblast cells.

Benzene is volatile organic hydrocarbon which is widely used in a wide range of industries. Studies have shown that exposure to benzene consequences serious health risks for human. Understanding the effect and risks of environmental hazard materials in the laser therapy of skin is interesting which can show useful or harmful role of these effects in therapies. In this study, the effect of low-level laser therapy was investigated on benzene-induced cytotoxicity on human skin fibroblast cells (HU02). Human skin fibroblast cells (HU02) were exposed to various concentrations of benzene (0-100μg/mL) and incubated for 2h. Then the effect of low-level laser therapy (LLLT) at 660-nm wavelength with 3J/cm2 energy for 90s was investigated on the viability of the cells exposed to benzene using MTT assay and inverted light microscope. The effect of low-level laser therapy on the viability of the cells was positive at concentrations 0-15μg/mL but negative at higher concentrations than 15μg/mL. Low-level laser therapy in low concentrations of benzene decreases the cytotoxicity caused by benzene and maintains cell viability. At high concentrations and in the presence of low-level laser therapy, the cell viability decreased compared to dark experiment. The morphology study of the cells using inverted light microscopy has confirmed the MTT results.

Effects of 405-, 532-, 650-, and 940-nm wavelengths of low-level laser therapies on orthodontic tooth movement in rats

BackgroundInvestigating the effects of 405-nm, 532-nm, 650-nm, and 950-nm wavelengths of LLLTs (low-level laser therapies) on the orthodontic tooth movement in rats by using histological and immunohistochemical methods. Forty-five Wistar albino rats were randomly divided into 5 groups: control group (positive control: the left maxillary 1st molar side; negative control: the right maxillary 1st molar side), 405 nm LLLT group (Realpoo), 532 nm LLLT group (Realpoo), 650 nm LLLT group (Realpoo), and 940 nm LLLT group (Biolase). The left maxillary 1st molar teeth of all rats were applied mesially 50-g force. Starting from the 1st day, 48 h intervals, LLLT was applied in continuous wave mode and in contact with the tissue. The application area was approximately 1 cm2. The lasers were performed for 3 min on each surface (buccal, palatal, mesial), totally 9 min (total dose 54 J/cm2). The amount of the molar mesialization, the bone area between the roots, PDL (periodontal ligament) measurements, TRAP (tartrate-resistant acid phosphatase), and ALP (alkaline phosphatase) immunoreactivity intensity were calculated.ResultsThe amount of the molar mesialization was significantly higher in the 650 nm LLLT group (mean 0.878 ± 0.201 mm; 95% CI (confidence interval) 0.724 and 1.032) than in the groups of positive control (mean 0.467 ± 0.357 mm; 95% CI 0.192 and 0.741) and 405 nm LLLT (mean 0.644 ± 0.261 mm; 95% CI 0.443 and 0.845) (p < 0.001). There were significant differences in the PDL-mesial (p = 0.042) and PDL-distal (p = 0.007) regions between the groups. The immunoreactivity intensity for TRAP-mesial was significantly higher in the positive control group (mean 109,420.33 ± 8769.17; 95% CI 100,217.65 and 118,623.02) than in the 405 nm (mean 91,678.83 ± 7313.39; 95% CI 84,003.9 and 99,353.77) and the 650 nm LLLT (mean 87,169.17 ± 4934.65; 95% CI 81,990.56 and 92,347.77) groups (p = 0.002). There was no statistically significant difference between the groups on immunoreactivity intensity with ALP staining.ConclusionsThe results of this study show that LLLT with 650-nm wavelength increases orthodontic tooth movement more than 405-nm, 532-nm, and 940-nm LLLTs. The 940-nm and 650-nm LLLTs also increase the bone area between the roots by more than 405-nm and 532-nm wavelengths.

Photobiomodulation enhances the Th1 immune response of human monocytes

This study aims to evaluate the effects of photobiomodulation (PBM) on human monocytes, assessing the oxidative burst and ultimate fungicidal potential of these cells, as well as the gene expression at the mRNA level of CD68, CD80, CD163, CD204, IL-6, TNF-α and IL-10 in derived macrophages. Primary cultures of human monocytes were irradiated with an InGaAlP (660nm)/GaAlAs (780nm) diode laser (parameters: 40mW, 0.04cm2, 1W/cm2; doses: 200, 400 and 600J/cm2). Cells were submitted to the chemiluminescence assay, and a microbicidal activity assay against Candida albicans was performed. Reactive oxygen species (ROS) and nitric oxide (NO) production were measured, and cell viability was assessed by the exclusion method using 0.2% Trypan blue reagent. Irradiated monocytes were cultured for 72h towards differentiation into macrophages. Total RNA was extracted, submitted to reverse transcription and real-time PCR. The results were analysed by ANOVA and the Tukey test (α = 0.05). Irradiated monocytes revealed a significant increase in their intracellular and extracellular ROS (P < 0.001). The 660nm wavelength and 400J/cm2 dose were the most relevant parameters (P < 0.001). The fungicidal capacity of the monocytes was shown to be greatly increased after PBM (P < 0.001). PBM increased the expression of TNF-α (P = 0.0302) and the production of NO (P < 0.05) and did not impair monocyte viability. PBM induces a pro-inflammatory Th1-driven response in monocytes and macrophages.

In vivo combined virtual histology and vascular imaging with dual-wavelength photoacoustic remote sensing microscopy

Histological evaluation of tissues is currently a lengthy process that typically precludes intraoperative margin assessment. While numerous approaches have aimed to address the need for intraoperative virtual histology, none have yet proved sufficiently efficacious. We demonstrate the use of a new all-optical imaging modality, photoacoustic remote sensing (PARS), capable of virtual histopathological imaging, while simultaneously providing visualization of microvasculature in both freshly resected tissues and live animal subjects. We demonstrate high resolutions of 0.44µm and 1.2µm for 266-nm and 532-nm excitation wavelengths, respectively, as well as the characterization of maximum permissible exposure limits for both excitation wavelengths.

Non-ablative photorejuvenation of lips by a 660-nm diode laser: two-case report

This cases report introduces new technique of lip rejuvenation, we studied the non-ablative photorejuvenation effect on lip, which keep the superficial layer intact and patient can resume their lifestyle after photorejuvenation, with totally painless procedure. The procedure was done on lips of two female patients, with 660nm diode laser, the sessions were repeated four times for each patient, photographs were taken before and after, then measurements of overall lip index were obtained for upper and lower lips. The overall volume of lips was increased, the lip’s texture was improved. This case report shows that 660nm wavelength with our protocol was successful to rejuvenate and augment the lips.

Dual-wavelength fiber-optic technique to assist needle cricothyroidotomy

The traditional needle cricothyroidotomy procedure is performed blindly without any medical equipment. Complications including posterior tracheal wall perforation, accidental vessel puncture, and missed tracheal puncture are reported. Therefore, we proposed a dual-wavelength fiber-optic technique based on the technique of near-infrared spectroscopy to assist operators performing needle cricothyroidotomy in a swine model. We embedded optical fibers in a 16-gauge intravenous needle catheter. Real-time data were displayed on an oscilloscope, and we used the program to analyze the data immediately. The change of optical density corresponding to 690-nm and 850-nm wavelengths and hemoglobin parameters (HbO2 and Hb concentrations) was analyzed immediately using the program in the laptop. Unique and significant optical differences were presented in this experiment. We could easily identify every different tissue by the change of optical density corresponding to 690-nm and 850-nm wavelengths and hemoglobin parameters (HbO2 and Hb concentrations). Statistical method (Kruskal-Wallis H test) was used to compare differences in tissues at each time-point, respectively. The p values in every tissue in optical density change corresponding to 690 nm and 850 nm were all < 0.001. Furthermore, the p values in every tissue in Hb and HbO2 were also all < 0.001. The results were statistically significant. This is the first and novel study to introduce a dual-wavelength embedded fibers into a standard cricothyroidotomy needle. This proposed system might be helpful to provide us real-time information of the advanced needle tip to decrease possible complications.

Scotch broom (Cytisus scoparius) germination and growth responses to light: implications for logging debris retention after forest harvesting

AbstractScotch broom [Cytisus scoparius (L.) Link] is a large nonnative, leguminous shrub that threatens native plant communities by rapidly invading recently disturbed sites, competing vigorously for soil water and nutrients, and imparting soil legacy effects that inhibit native plants. In the Pacific Northwest, logging debris retention after forest harvesting prevents or slows C. scoparius invasions. A series of studies were conducted to determine potential mechanisms by which logging debris modifies the light environment to limit germination and growth of C. scoparius. In laboratory studies, seed germination did not vary significantly (P &gt; 0.05): (1) between presence and absence of light for several temperature regimes, (2) when exposed to red (660-nm wavelength) versus far-red (730-nm wavelength) light, and (3) across a range of red/far-red light (R/FR) ratios. These results indicate that modification of the light environment by logging debris or plant canopies has little or no influence on C. scoparius germination. In a study to simulate effects of variable mass of logging debris, “heavy” debris (2 kg m−2) caused biologically relevant reductions in photosynthetic photon flux density (PPFD) and R/FR relative to conditions under “light” debris (1 kg m−2). Cytisus scoparius germination did not differ significantly between simulated heavy and light debris; however, values of seedling root and shoot biomass under heavy debris were 16% and 71% of those observed under light debris, respectively. These results indicate that heavy debris limits biomass of C. scoparius seedlings, particularly roots, by reducing both PPFD and R/FR, which increases seedling vulnerability to summer drought or other stressors. Retention of heavy logging debris after forest harvesting has potential application on sites likely to be invaded by C. scoparius, as well as those sites with seedbanks containing C. scoparius.

Acoustic Oscillations of Aluminum Membranes Laser-Excited by a Thermoelastic Mechanism

A theoretical model of photoacoustic response signal formation from laser-irradiated metal membranes is proposed with allowance for the excitation of defect states. Theoretical results obtained for 197-μm-thick aluminum membranes in a frequency range from 20 Hz to 7 kHz are compared to experimental data for membranes excited by laser radiation at a 660-nm wavelength. The proposed theoretical model provides quite adequate coincidence with experiment for membrane oscillations under the assumption of a purely surface character of laser radiation absorption.

Low-level laser irradiation potentiates anticancer activity of p-coumaric acid against human malignant melanoma cells.

p-Coumaric acid (PCA) is a kind of phenolic compound, and as one of the cinnamic acid derivatives, it has many biological functions such as antioxidants, anti-inflammatory, antiplatelet, and anticancer activity. Low-level laser irradiation has received increasing interest in the fields of tissue regeneration and wound healing. In this study, the effect of low-level laser irradiation on human fibroblast cells (human dermal fibroblast) and human melanoma cancer cells (A375 and SK-MEL-37) treated with PCA was investigated. The human dermal fibroblast, A375, and SK-MEL-37 cells were exposed to low-level laser at 660-nm wavelength with 3 J/cm for 90 s, and then the cells were treated with different concentrations of PCA (0-1000 μg/ml for 24 h), separately. In another experiment, first the cells were treated by PCA and then irradiated with low-level laser as described before. The effect of various irradiation energy (1-6 J/cm) on the melanoma cells, which were then treated by PCA, was studied. The cell viability using MTT assay and lactate dehydrogenase assay was determined. Morphological changes owing to apoptosis induction by irradiation and PCA were detected by fluorescence microscopy using acridine orange/ethidium bromide double staining. The results showed that pretreatment with low-level laser irradiation and then PCA reduced the survival and growth of melanoma cells more than the early treatment with PCA and then low-level laser irradiation. Lactate dehydrogenase activity was reduced significantly by preirradiation and then PCA treatment in comparison with the dark group in melanoma cells. The cell cytotoxicity at different irradiation energy and then IC50 concentration of PCA was increased up to 3 J/cm and then decreased following increasing irradiation energy. The morphology study with light microscopy and apoptotic assay using acridine orange/ethidium bromide dual staining confirmed the MTT results. This study showed that low-level laser irradiation alone is not able to kill human normal fibroblast and human melanoma cancer cells. Preirradiation followed by treatment with PCA did not change the cell viability in human fibroblast significantly but reduced the cell viability in melanoma cells presumably through the apoptosis pathway.

Investigation of the time interval of plasma generation for a high repetition rate laser ion source.

To apply a laser ion source that generates a high-intensity pulsed beam to high-dose applications, such as ion implantation, a high repetition rate operation with a short pulse interval is required. However, when the pulse interval is shortened, there is a concern that a plasma, which is different from a single pulse plasma generation, may be formed due to the interaction between the preceding and following pulses. We investigated the time interval in which plasma pulses are generated without pulse-to-pulse interaction using a laser ion source with two lasers. In the experiment, a graphite target was irradiated by two laser beams (1064-nm wavelengths) with the same pulse widths (5.4 ns) and energies (15 mJ, 30 mJ, and 45 mJ) at different time intervals ranging from 1000 μs to 0 µs, and the time integrated value corresponding to the total charge amount was calculated from the measured time-of-flight signal of the generated carbon ion current. It was observed that the total charge did not change when the time interval was as low as approximately 100 µs, and the total charge rapidly decreased when the time interval was below approximately 100 µs. Thus, it was determined that the interaction occurs within a time interval of approximately 100 µs.

Angiogenic protein synthesis after photobiomodulation therapy on SHED: a preliminary study.

This study evaluated the viability, proliferation, and protein expression after photobiomodulation (PBM) of stem cell from human exfoliated deciduous teeth (SHED). The groups were the following: G1 (2.5J/cm2), G2 (3.7J/cm2), and control (not irradiated). According to the groups, cells were irradiated with InGaAlP diode laser at 660nm wavelength, continuous mode, and single time application. After 6h, 12h, and 24h from irradiation, the cell viability and proliferation, and the protein expression were analyzed by MTT, crystal violet, and ELISA multiplex assay, respectively. Twenty-four hours after PBM, SHED showed better proliferation. Over time in the supernatant, all groups had an increase at the levels of VEGF-C, VEGF-A, and PLGF. In the lysate, the control and G2 exhibited a decrease of the VEGF-A, PECAM-1, and PLGF expression, while control and G3 decreased VEGF-C, VEGF-A, and PDGF expression. The dosimetries of 2.5J/cm2 and 3.7J/cm2 maintained viability, improved proliferation, and synthesis of the angiogenic proteins in the supernatant in the studied periods on SHED.

Passive Fiber Optic Evanescent Wave Sensor for the Measurement of Refractive Index at Various Temperatures Using a Tunable Light Source

The study of refractive index of liquids over a range of 10oC to 60oC shows very interesting results to design and develop a highly sensitive passive fiber optic sensor based on a U-shaped glass probe. The depth of penetration of light that escaping from the core of the fiber into the cladding plays a crucial role in the development of a highly sensitive fiber optic evanescent wave sensor. The depth of penetration of an optical fiber striped off its cladding is directly related to the wavelength of the light, the index of refraction of the surrounding medium, the angle of incidence of light, the bending radius and thickness of the U-shaped probe. In the design of the sensor a U-shaped glass probe is used to replace the core of the fiber in the region of sensing, the diameter of which is same as that of the cores of a pair of insensitive fibers which in-turn connected to a tunable light source and an optical detector. The sensor is highly reliable, robust and easy to configure using multimode PCS fibers and the source operating at the wavelengths of 630nm, 660nm, 820nm and 850nm.

Multifunctional Extrinsic Fiber Optic Sensor to Measure Various Parameters of Liquids at the Operating Wavelength of 660nm Employing a U-Shaped Glass Rod as a Sensing Element

Fiber Optic sensor technology has become more popular since early 1970’s during which the mechanism of losses from optical fibers was exploited to construct a new class of fiber optic sensors and systems. A novel fiber optic sensor has been developed by connecting a U-shaped glass element of specific dimensions between a light source of 660nm wavelength and an optical power detector by using a couple of PCS optical fibers of 200/230μm diameters of core and cladding respectively. The sensor can be employed to measure several parameters such as Refractive Index, Density, Viscosity, Ultrasonic Velocity, Molar Volume, Molar Refraction, Dielectric Constant, Acoustic Impendence, Adiabatic Compressibility, Viscous Relaxation Time, Intermolecular Free Length, Absorption Coefficient, Gibb’s Free Energy, Free Volume, Internal Pressure and their excess parameters of Toluene and tert-Butanol mixtures at 30℃ temperature and at the operating wavelength of 660nm