1064-nm Wavelength Research Articles

The effect of intra-oral LED device and low-level laser therapy on orthodontic tooth movement in young adults: A randomized controlled trial

This randomized controlled clinical trial aimed to assess the effect of LED5 and LLLT6 in a three-arm parallel setting. Sixty patients who needed the maxillary first premolar extraction were allocated to three groups using the stratified block randomization method. In the LED group, a custom-made device with a wavelength of 640nm and a power density of 40 mW/cm2 was used 5min/day. In the laser group, Ga Al As7 laser with a wavelength of 810nm and a power of 100 mW was used on days 0, 3, 30, and 60 each time for 18seconds. Patients in the control group received placebo treatment as the laser group protocol, using a coated light cure device. Models were made at baseline and monthly until the end of the retraction. The rate of canine retraction was the primary outcome, while canine rotation and pain were secondary outcomes. The final data were anonymous for the outcome assessor and statistical consultant. Data were analyzed per protocol using a linear mixed model. The rate of canine retraction significantly increased by 60.8% in the laser group, while it increased not significantly by 26% in the LED group compared with the control group. There was no significant difference among the groups in terms of tooth rotation and pain. LLLT can accelerate orthodontic tooth movement (OTM). LED with the present setting couldn't increase the rate of OTM. LLLT and LED did not affect canine rotation or pain. IRCT20120220009086N4. On 1 June 2019 was retrospectively registered.

Preliminary assessment of a portable Raman spectroscopy system for post-operative urinary stone analysis.

We aimed to evaluate the reliability of a portable device that applies Raman spectroscopy at an excitation wavelength of 1064nm for the post-operative analysis of urinary stone composition. Urinary stone samples were obtained post-operatively from 300 patients. All samples were analyzed by the portable Raman spectroscopy system at an excitation wavelength of 1064nm as well as by infrared spectroscopy (IR), and the results were compared. Both Raman spectroscopy and IR could detect multiple stone components, including calcium oxalate monohydrate, calcium oxalate dihydrate, calcium phosphate, uric acid, cystine, and magnesium ammonium phosphate hexahydrate. The results from 1064-nm Raman analysis matched those from IR analysis for 96.0% (288/300) of cases. Although IR detected multiple components within samples more often than Raman analysis (239 vs 131), the Raman analysis required less time to complete than IR data acquisition (5min vs 30min). These preliminary results indicate that 1064-nm Raman spectroscopy can be applied in a portable and automated analytical system for rapid detection of urinary stone composition in the post-operative clinical setting. Chinese Clinical Trail Register ID: ChiCTR2000039810 (approved WHO primary register) http://www.chictr.org.cn/showproj.aspx?proj=63662 .

Modeling laser-induced incandescence of Diesel soot\u2014Implementation of an advanced parameterization procedure applied to a refined LII model accounting for shielding effect and multiple scattering within aggregates for {varvec{alpha}}_{{varvec{T}}} and {varvec{E}}left( {varvec{m}} right) assessment

An extensive set of LII signals measured in a Diesel spray flame has been simulated using a refined LII model built upon a comprehensive version of soot heat- and mass-balance equations. This latter includes terms standing for saturation of linear, single- and multi-photon absorption processes, cooling by sublimation, conduction, radiation and thermionic emission in addition to mechanisms depicting soot oxidation and annealing, non-thermal photodesorption of carbon clusters as well as corrective factors allowing considering shielding effect and multiple scattering (MS) within aggregates. A complete parameterization of the so-proposed model has been achieved by means of an advanced optimization procedure coupling design of experiments with a genetic algorithm-based solver. Doing so, the values of different factors involved in absorption and sublimation terms have been assessed for a 1064-nm laser excitation wavelength including the multi-photon absorption cross section for C2 photodesorption and the saturation coefficients for linear- and multi-photon absorption, among others. This parameterized model has then been demonstrated to effectively reproduce signals measured in different combustion media including a CH4/O2/N2 premixed flat flame and a diffusion ethylene flame. As a result of the data derived from the analysis of the Diesel flame, a thermal accommodation coefficient value of 0.49 has been assessed against 0.34 when neglecting the shielding effect. In addition, values of the soot absorption function (Eleft( m right)) comprised between 0.18 and 0.31 have been inferred depending on the particle maturation stage. On the other hand, Eleft( m right) 24% higher on average have been estimated when neglecting MS thus illustrating the importance of aggregate characteristics on soot properties derived through LII modeling. Eventually, the Eleft( m right) evolution observed herein has been compared with results issued from studies conducted with varied hydrocarbons which led to highlight the crucial role played by the soot maturity level over the nature of the burnt fuel as far as optical properties are concerned.

Broadband Nonlinear Optical Response of Nitrogen-Doped Diamond

A nitrogen-doped diamond crystal with (111) orientation was synthesized with an NaN3 additive in the FeNi-C system at a pressure of 6.5 GPa and a temperature of 1,310°C, using the temperature gradient growth (TGG) method. Spectroscopic properties such as the absorption spectrum and the Raman spectrum as well as the Fourier transform infrared (FTIR) spectrum were studied. FTIR spectroscopy of the C-N vibrational modes at 1,344 and 1,130 cm−1 suggested a nitrogen content of 310 ppm. Its nonlinear optical (NLO) response was investigated using the Z-scan technique under the femtosecond regime. Due to the presence of nitrogen defects, the synthesized crystal performed large nonlinear absorption under both 800- and 532-nm wavelength excitations. However, intrinsic diamond only experiences nonlinear refraction under these two wavelength excitations. Its broadband NLO properties indicated that nitrogen-doped diamond crystals were suitable for the application of ultrafast optical devices.

Amplification of femtosecond and picosecond pulses using large mode area Erbium-doped fiber at 1530 nm wavelength

We present amplification of short and ultrashort laser pulses at 1530-nm center wavelength using a large mode area Er-doped fiber (LMA-EDF). The mode area of about 1700 μm2 tremendously increases the power handling capacity of the fiber and helps in achieving up to ∼ 17 dB/m gain with 10 W power of 980-nm wavelength pump. The LMA fiber used here is a 3-layer W-type fiber designed to have effective single mode operation with higher order mode discrimination and sufficient mode spacing between the first few modes to avoid any possible mode coupling. In particular, we numerically demonstrate the amplification of 300 fs, 1 kW peak power pulses to ∼ 20 fs, ∼2.6 MW peak power pulses in 1.5-m propagation distance, and of 50 ps, 1 kW peak power pulses to ∼ 65 ps, ∼26 MW peak power pulses in 3-m propagation distance of the LMA-EDF. The generated pulses would be useful in applications such as eye-safe remote sensing and 3D laser processing of silicon.

Near-infrared Transillumination and Photodynamic Therapy Using Hypericin in Animal Laryngeal Tumors.

We aimed to validate a pilot study of photodiagnosis using near infrared (NIR) transillumination and assess the clinical efficacy of hypericin-mediated photodynamic therapy (HYP-PDT) in a rabbit laryngeal cancer model in order to develop a novel therapeutic modality with complete remission and preservation of the functional organ. (1) In vitro study: VX tumor cells were subcultured and subjected to HYP-PDT. (2) In vivo study: A laryngeal cancer model was developed in which 12 rabbits were inoculated with a VX tumor suspension in the submucosal area of the left vocal fold using a transoral approach. All rabbits underwent NIR transillumination using light with a wavelength of 780nm. The survival periods of the three treatment groups (6 rabbits in Group A: HYP-PDT, 3 each in Groups B and C: laser irradiation or HYP administration only) were analyzed. The higher the HYP concentration, the lower the VX cell viability in response to HYP-PDT using 590nm LED. Following HYP-PDT, small tumors in Group A-1 rabbits healed completely and the animals demonstrated a long survival period, and larger tumors in Group A-2 healed partially with a survival period that extended over 3weeks after inoculation. The survival of Groups B and C were not different over the first 3weeks of the study, and were shorter than in Group A. We found HYP-PDT could be a curative therapy for early-stage cancers that may also preserve organ function, and may inhibit tumor progression and metastasis during advanced stages of laryngeal cancer.

Femtosecond laser-induced spatial-frequency-shifted nanostructures by polarization ellipticity modulation.

We demonstrate a prominent spatial frequency shift (SFS) for the femtosecond laser-induced periodic structures by only changing the polarization ellipticity of the working laser. The nanostructures are fabricated on the surfaces of silicon (Si) and zinc selenide (ZnSe) using elliptically polarized femtosecond laser pulses, with the pulse duration of 35 fs, the central wavelength of 800nm, and the repetition rate of 1kHz. The experimental results show that the red- and blue-shift trends of the SFS are individually represented on silicon and zinc selenide with the increased polarization ellipticity, where low- and high-spatial-frequency nano-ripples are fabricated, respectively. These unique phenomena are explained by using the laser-surface plasmon polariton interference mechanism and the effective medium theory. The proposed nanostructures with regulatable period are further used for creating nano-gratings on silicon which perform chirped characteristics.

Ten-year follow-up of a randomized controlled trial comparing saphenofemoral ligation and stripping of the great saphenous vein with endovenous laser ablation (980 nm) using local tumescent anesthesia

ObjectiveThe long-term results of saphenofemoral ligation and stripping (SFL/S) were compared with 980-nm bare fiber endovenous laser ablation (EVLA) for the treatment of great saphenous vein (GSV) incompetence. MethodsThis was a single-center, randomized, controlled trial with a follow-up time of 10 years. Patients with GSV incompetence were randomized to undergo SFL/S or EVLA under tumescent anesthesia. The primary outcome was recurrence of groin-related varicose veins seen on duplex ultrasound imaging and clinical examination. The secondary outcomes were (changes or improvement in) CEAP clinical class, venous symptoms, cosmetic results, quality of life, reinterventions, and complications. ResultsBetween June 2007 and December 2008, 122 patients (130 limbs) were included; of these, 68 limbs were treated with SFL/S and 62 limbs with EVLA. The 10-year estimated freedom from groin recurrence as seen on duplex ultrasound imaging was higher in the SFL/S group (73% vs 44% in the EVLA group; P = .002), and the same trend was seen for clinically evident recurrence (77% vs 58%, respectively; P = .034). Nine reinterventions (17%) were deemed necessary in the SFL/S group vs 18 (36%) in the EVLA group (P = .059). All reinterventions in the SFL/S group consisted of foam sclerotherapy. Reinterventions in the EVLA group included foam sclerotherapy (n = 5), crossectomy (n = 2), and endovenous procedures (n = 11). There was no significant differences in quality of life and relief of venous symptoms. Cosmetic appearance improved, with a better cosmetic rating in the SFL/S group compared with the EVLA group (P = .026). One patient in the SFL/S group had a persisting neurosensory deficit remaining at 10 years. ConclusionsThis study showed no clear long-term advantage of EVLA with a 980-nm wavelength and bare-tip fiber over high ligation and stripping of the GSV under local tumescent anesthesia.

Optical coherence tomography-surveilled laser ablation using multifunctional catheter and 355-nm optical pulses

An optical coherence tomography (OCT)-monitored laser ablation system is presented in this study. The laser ablation subsystem is constructed using the third harmonic output of a Nd:YAG laser source operating at a 355-nm optical wavelength with a single pulse energy greater than 160 mJ and a 1–10 Hz tunable repetition rate. The imaging subsystem is a typical M-mode swept-source OCT system. Moreover, a type of all-fiber multifunctional integrated catheter is demonstrated. The ablation catheter consists of a fiber bundle including 41 multi-mode fibers with an outer diameter of 0.9 mm. A forward-viewing OCT imaging probe is inserted into the ablation catheter for M-mode imaging. The performance of the system is demonstrated by OCT surveillance of the laser ablation process using expanded polystyrene foam as the sample. The OCT system can be used to record the ablation process and simultaneously count the laser ablation duration. This study proposes an effective potential technique to surveil material laser ablation processes, especially in situations where bulky optics are prohibited and all-fiber devices are required.

Texturized P(VDF-TrFE)/BT membrane enhances bone neoformation in calvaria defects regardless of the association with photobiomodulation therapy in ovariectomized rats.

The purpose of this investigation was to evaluate in vivo the response of bone tissue to photobiomodulation when associated with texturized P(VDF-TrFE)/BT in calvaria defects of ovariectomized rats. Wistar Hannover rats were submitted to ovariectomy/control surgery. Calvaria bone defects of 5-mm diameter were performed after 90days of ovariectomy. The animals were divided into OVX (without laser (L) and membrane), OVX + P(VDF-TrFE)/BT, OVX + P(VDF-TrFE)/BT + L, and OVX + PTFE + L. It was utilized a low-intensity gallium-aluminum-arsenide laser (GaAlAs) with 780-nm wavelength and 30-J/cm2 energy density in 12 sessions (120s). Thirty days after the bone defect the animals were euthanized for histological, microtomographic, and molecular evaluation. Quantitative analysis was analyzed by statistical software for p < 0.05. Histological parameters showed bone tissue formation at the borders of all group defects. The association of photobiomodulation and texturized P(VDF-TrFE)/BT was not synergistic and did not show significant changes in morphometric analysis and biomarkers gene expression. Nevertheless, texturized P(VDF-TrFE)/BT membrane enhanced bone repair regardless of the association with photobiomodulation therapy, with an increase of connectivity density when compared to the OVX + PTFE + L group. The association of photobiomodulation therapy and PTFE was synergistic, increasing the expression of Runx2, Alp, Bsp, Bglap, Sp7, and Rankl, even though not enough to reflect significance in the morphometric parameters. The utilization of texturized P (VDF-TrFE)/BT, regardless of the association with photobiomodulation therapy, enhanced bone repair in an experimental model of osteoporosis.

Intraoperative detection of human meningioma using a handheld visible resonance Raman analyzer.

To report for the first time the preliminary results for the evaluation of a VRR-LRR™ analyzer based on visible resonance Raman technique to identify human meningioma grades and margins intraoperatively. Unprocessed primary and recurrent solid human meningeal tissues were collected from 33 patients and underwent Raman analysis during surgeries. A total of 1180 VRR spectra were acquired from fresh solid tissues using a VRR-LRR™ analyzer. A confocal HR Evolution (HORIBA, France SAS) Raman system with 532-nm excitation wavelength was also used to collect data for part of the ex vivo samples after they were thawed from - 80°C for comparison. The preliminary analysis led to the following observations. (1) The intensity ratio of VRR peaks of protein to fatty acid (I2934/I2888) decreased with the increase of meningioma grade. (2) The ratio of VRR peaks of phosphorylated protein to amid I (I1588/I1639) decreased for the higher grade of meningioma. (3) Three RR vibration modes at 1378, 3174, and 3224cm-1 which were related to the molecular vibrational bands of oxy-hemeprotein, amide B, and amide A protein significantly changed in peak intensities in the two types of meningioma tissues compared to normal tissue. (4) The changes in the intensities of VRR modes of carotenoids at 1156 and 1524cm-1 were also found in the meningioma boundary. The VRR-LRR™ analyzer demonstrates a new approach for label-free, rapid, and objective identification of primary human meningioma in quasi-clinical settings. The accuracy for detecting meningioma tissues using support vector machines (SVMs) was over 70% based on Raman peaks of key biomolecules and up to 100% using principal component analysis (PCA).

Remove Skin Deformities by Using CO2 and Nd:Yag Laser

The treatment of some skin damage have been studied influence the laser beam CO2 and the Nd:Yag with wavelengths (10600nm and 1064 nm) respectively as foundation of radiation. The current research aims to verify effect of altered laser dosages of the skin in an attempt to recognize how the laser achieves medicinal effects to treat skin lesions. And the aims to establish the correlation between laser dose and biological influence and so after that calculate its low dose with higher medical influence and minimal harm to. The number of cases included four different diseases, ranging between 18-50 years. Areas of the body were exposed to laser beams and different wavelengths by type laser user. The first case, represent the image of a girl suffering from autoimmune disease, Nd:YAG laser was used with Q-swtich Nd: YAG to treat this condition and the wavelength is 1064 nm, second case, image of a person suffering from the impact. Fractional Co2 Laser and wavelength 10600 nm where used and third case: An image of a person suffering from costs, treatment by using Q-switch Nd-YAG laser short pulse has a wavelength of 1064nm.

On the challenges of precise velocity measurements in vertical convective wall jets

For the transition of our energy supply towards a higher share of renewables, thermal energy storage (TES) systems are, besides electric batteries and chemical energy storage systems, one promising solution to overcome the volatile nature of renewable energy sources. For the most efficient operation, the liquid storage material in the tank should be stratified by its temperature-dependent density. As a result, the cold fluid remains at the bottom, and the heated fluid rises to the top (Alva et al. (2018)). Typically steel tanks are used for TES, and thus, the wall material has a thermal diffusivity that is one to two orders of magnitudehigher than that of the storage fluid. Consequently, the tank’s sidewalls work as a thermal bridge between the stratified layers. In recent studies, the authors have shown that the resulting heat flux induces two counterdirected, convective wall jets near the sidewalls of the tank, which increase mixing of the stratification and thus lowers the exergy content and the storage efficiency (Otto et al. (2019, 2020)). Using a model experiment of a TES, the entire vertical extent of the detected wall jets is investigated. Hence, the typical flow structures of vertical, natural convection under the influence of non-zero temperature gradients in the ambient fluid can be analyzed, which can help to improve storage tanks in the future. The velocity in the region of the wall jets is measured via 2d particle-image velocimetry (PIV) in a rectangular model experiment of 750mm height on a base area of 375mm×375mm made from polycarbonate. The jets evolve on the surface of an aluminum plate simulating the storage tank’s sidewall. The measuring system consists of four cameras with a resolution of 2160×2560 pixels combined with objective lenses with 100mm focal length capturing the raw images in a plane perpendicular to the aluminum wall. A Nd:YAG laser with a wavelength of 532nm illuminates the measuring plane. Simultaneously using up to four cameras adjacent to each other and stitching their resulting vector fields, the vertical extent of the field of view increases from 38mm up to 140mm. Despite this, the field of view is still much smaller than the vertical extent of the model experiment, so that seven consecutive runs are performed to cover the entire height. Disturbing reflections of the laser light sheet on the aluminum wall are eliminated using optical filters for the cameras that are opaque for the green laser light in combination with fluorescently (Rhodamine B) dyed PMMA tracer particles with a diameter between 1–20μm. The particles emit light at a wavelength of 610nm (orange light) and can therefore be detected through the cameras’ filters. During four separate measuring periods, where each lasts for two minutes, double frame images are captured with a time difference of 19.981 ms (maximum possible value) at a measuring frequency of 7 Hz. Figure 1 shows a schematic of the camera setup next to the model experiment and the measurement and evaluation procedure to finally receive one time-averaged velocity field per measuring period of the full height of the experiment. The raw data evaluation process starts with calculating the vector fields of all cameras used at a certain measuring position and stitching them to one flow field of this position. Since the wall jets’ horizontal extents are with 2–7mm relatively small and they show high velocity gradients, the raw images are evaluated in both single-frame and double-frame mode. With a velocity threshold that corresponds to a pixel displacement of 1/4 of the interrogation window size and the time difference of the single-frames, the resulting vector fields are masked and merged into one final vector field. This vector field consists of high velocities evaluated in double-frame mode and low velocities evaluated in single-frame mode (see Figure 2) thus minimizing the relative error. The algorithm used in this work is similar to the multi-frame PIV approach introduced by Hain and K¨ahler (2007). Figure 3 shows the time-averaged results of the first measuring period for each of the seven measuring positions in height.

Stepwise neuronal network pattern formation in agarose gel during cultivation using non-destructive microneedle photothermal microfabrication

Conventional neuronal network pattern formation techniques cannot control the arrangement of axons and dendrites because network structures must be fixed before neurite differentiation. To overcome this limitation, we developed a non-destructive stepwise microfabrication technique that can be used to alter microchannels within agarose to guide neurites during elongation. Micropatterns were formed in thin agarose layer coating of a cultivation dish using the tip of a 0.7 upmu mathrm{m}-diameter platinum-coated glass microneedle heated by a focused 1064-nm wavelength infrared laser, which has no absorbance of water. As the size of the heat source was 0.7 upmu mathrm{m}, which is smaller than the laser wavelength, the temperature fell to 45 ^circ hbox {C} within a distance of 7.0 upmu mathrm{m} from the edge of the etched agarose microchannel. We exploited the fast temperature decay property to guide cell-to-cell connection during neuronal network cultivation. The first neurite of a hippocampal cell from a microchamber was guided to a microchannel leading to the target neuron with stepwise etching of the micrometer resolution microchannel in the agarose layer, and the elongated neurites were not damaged by the heat of etching. The results indicate the potential of this new technique for fully direction-controlled on-chip neuronal network studies.

Photobiomodulation by Near-Infrared 980-nm Wavelengths Regulates Pre-Osteoblast Proliferation and Viability through the PI3K/Akt/Bcl-2 Pathway.

Background: bone tissue regeneration remains a current challenge. A growing body of evidence shows that mitochondrial dysfunction impairs osteogenesis and that this organelle may be the target for new therapeutic options. Current literature illustrates that red and near-infrared light can affect the key cellular pathways of all life forms through interactions with photoacceptors within the cells’ mitochondria. The current study aims to provide an understanding of the mechanisms by which photobiomodulation (PBM) by 900-nm wavelengths can induce in vitro molecular changes in pre-osteoblasts. Methods: The PubMed, Scopus, Cochrane, and Scholar databases were used. The manuscripts included in the narrative review were selected according to inclusion and exclusion criteria. The new experimental set-up was based on irradiation with a 980-nm laser and a hand-piece with a standard Gaussian and flat-top beam profile. MC3T3-E1 pre-osteoblasts were irradiated at 0.75, 0.45, and 0.20 W in continuous-wave emission mode for 60 s (spot-size 1 cm2) and allowed to generate a power density of 0.75, 0.45, and 0.20 W/cm2 and a fluence of 45, 27, and 12 J/cm2, respectively. The frequency of irradiation was once, three times (alternate days), or five times (every day) per week for two consecutive weeks. Differentiation, proliferation, and cell viability and their markers were investigated by immunoblotting, immunolabelling, fluorescein-FragELTM-DNA, Hoechst staining, and metabolic activity assays. Results and conclusions: The 980-nm wavelength can photobiomodulate the pre-osteoblasts, regulating their metabolic schedule. The cellular signal activated by 45 J/cm2, 0.75 W and 0.75 W/cm2 consist of the PI3K/Akt/Bcl-2 pathway; differentiation markers were not affected, nor do other parameters seem to stimulate the cells. Our previous and present data consistently support the window effect of 980 nm, which has also been described in extracted mitochondria, through activation of signalling PI3K/Akt/Bcl-2 and cyclin family, while the Wnt and Smads 2/3-β-catenin pathway was induced by 55 J/cm2, 0.9 W and 0.9 W/cm2.

Acne keloidalis nuchae treatment

Objectives To compare the efficacy of 1064-nm Nd : YAG laser and intralesional corticosteroid in the treatment of acne keloidalis nuchae (AKN). Background AKN is a chronic inflammatory condition that leads to scarring of the hair follicles, development of keloid-like papules and plaques, and scarring alopecia on the nape of the neck and occipital scalp. Patients and methods The study was conducted on 20 patients with AKN and was studied through the following regimens: group I included 10 patients treated by long pulsed Nd : YAG laser of 1064-nm wavelength, and group II comprised 10 patients treated by intralesional corticosteroid. Sessions were performed every 2 weeks for six sessions. Evaluation included papule count, keloidal plaque size assessment, and patient satisfaction before, at every session, and at the end of treatment. Results Patients' papule and pustule count in Nd : YAG group before treatment ranged between 3 and 30 (10.70±8.43), and after treatment, it was decreased significantly (3.70±3.37), whereas in intralesional corticosteroid group before treatment, it ranged between 2 and 9, and after treatment, it decreased significantly. There were no significant differences before treatment and after treatment, where P=0.218. Conclusion Treatment of AKN by Nd : YAG 1064-nm laser is much more promising than intralesional injection of corticosteroids and much more tolerated by patients.

Photobiomodulation Effect of Different Diode Wavelengths on the Proliferation of Human Gingival Fibroblast Cells.

This study is focused on comparing the effect of various energy densities and wavelengths of diode lasers on the proliferation of human gingival fibroblast (HGF) cells invitro. In this study, 204 sample cells were examined in 4 test groups (laser radiation) and 1 control group (non-laser radiation). The proliferation rate of radiated cells with wavelengths of 635, 660, 808 and 980nm and the densities of 1, 1.5, 2.5 and 4Jcm-2 was measured after 1, 3 and 5days using the MTT assay. The proliferation rate of human gingival fibroblast (HGF) cells in test groups was increased on day 1 at wavelengths of 635, 808 and 980nm and on day 3 at the wavelength of 980nm compared with the control group. Our findings denoted that the photobiomodulation therapy increased the proliferation rate of HGF. The most desirable laser radiation setting, which led to the highest proliferation rate of the cells, included 980nm wavelength with 1, 1.5 and 4Jcm-2 energy densities and 635nm wavelength with 4Jcm-2 energy density.

Laser-induced thermal grating spectroscopy based on femtosecond laser multi-photon absorption

Laser-induced grating spectroscopy (LIGS) is for the first time explored in a configuration based on the crossing of two focused femtosecond (fs) laser pulses (800-nm wavelength) and a focused continuous-wave (cw) laser beam (532-nm wavelength). A thermal grating was formed by multi-photon absorption of the fs-laser pulses by hbox {N}_{{2}} with a pulse energy around 700 upmu J (sim 45 TW/hbox {cm}^{2}). The feasibility of this LIGS configuration was investigated for thermometry in heated nitrogen gas flows. The temperature was varied from room temperature up to 750 K, producing strong single-shot LIGS signals. A model based on the solution of the linearized hydrodynamic equations was used to extract temperature information from single-shot experimental data, and the results show excellent agreement with the thermocouple measurements. Furthermore, the fluorescence produced by the fs-laser pulses was investigated. This study indicates an 8-photon absorption pathway for hbox {N}_{{2}} in order to reach the hbox {B}^{3}Pi _{g} state from the ground state, and 8 + 5 photon excitation to reach the hbox {B}^{2}Sigma _{u}^{+} state of the hbox {N}_{2}^{+} ion. At pulse energies higher than 1 mJ, the LIGS signal was disturbed due to the generation of plasma. Additionally, measurements in argon gas and air were performed, where the LIGS signal for argon shows lower intensity compared to air and hbox {N}_{{2}}.

Two-dimensional waveguides in magneto-optical glasses fabricated by carbon ion implantation and femtosecond laser ablation

The exploration of 2D waveguide structures on optoelectronic materials is important for applications in integrated optics devices. In this work, 2D waveguides on the magneto-optical glass were fabricated via combining the carbon ion implantation and the femtosecond laser ablation. Firstly, the 1D waveguide was formed by the double energy (6.0+5.5) MeV carbon ion implantation with fluences of (8.0+4.0)×1013 ions/cm2. Subsequently, the femtosecond laser ablation with 800-nm central wavelength and 1.0-kHz repetition rate was conducted on the 1D waveguide surface to manufacture 2D guiding structures. The end-facet images were captured by an optical microscope. The near-field modal profiles of the 2D waveguides were recorded by an end-face coupling system at near-infrared (976 nm) and visible (532 nm) bands. The research results provide the feasibility and the experimental basis for the preparation of a magneto-optical waveguide isolator.

UV Light Detection Using Resonance Frequency of Piezoelectric Quartz Crystal

This article reported about the ultraviolet (UV) radiation effect on the resonance frequency response of a AT-cut piezoelectric quartz crystal. A large resonance frequency upshift was observed when the quartz crystal was irradiated by UV light of 355-nm wavelength using a Q-switched pulsed Nd:YVO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> UV laser. The dynamic frequency response behavior was systematically investigated by illuminating the quartz crystal with UV light in which the UV intensity was varied with time in staircase- and linear pulse-shaped patterns. From the experimental analysis, we measured the limit of detection and the sensitivity of the quartz crystal, which are about 0.5 mW/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and 0.706 Hz/(mW/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ), respectively. For a constant UV irradiation, a moderate response (<;10 s) and recovery (<;10 s) times were achieved during the on and off cycles of the UV light. The short-term repeatability and maximum operating limit of AT-cut quartz crystal were also further studied upon exposure to UV light with different intensities. In this work, we not only demonstrate the impact of UV irradiation on quartz crystal but also discuss the mechanism of upshift in resonance frequency upon exposure to UV light. This study shows the applicability of quartz crystal for the detection of UV light.