Nano-pulsed Laser Research Articles

Simple and highly accurate measuring method for evaluating the cleanliness levels of laser-cleaned surfaces according to the ISO standard

Surface cleaning is highly demanded in the construction, mechanical, and automotive industries. Laser surface cleaning is increasingly being used due to its advantages such as high selectivity, fast cleaning, and efficient response to many different materials. However, if pulsed lasers with a high peak power are used for surface cleaning, they can damage the surface material if the technological parameters are not controlled appropriately. Therefore, it is necessary to develop accurate and high-speed measurement methods to evaluate the surface quality after cleaning. In this paper, a steel cleaning system using a nano-pulsed laser with a wavelength of 1064 nm was proposed. To evaluate the cleanliness of samples, a simple and rapid measurement system based on image processing was developed. The ISO 8501 standard was chosen as the standard cleanliness level. The surface after cleaning was captured using a scientific camera. The percentage of dark pixels in the captured image was determined using the histogram method. The surface quality after cleaning was determined by comparing it with the cleanliness level of the ISO 8501 standard. Thus, this proposed method is used to evaluate the influence of the average power of the laser source on the cleanliness of the steel surface. This method was observed to be compact, cost-effective, and highly accurate; it also proved to be easy to integrate into cleaning systems.

The Role of Nanotechnology in Understanding the Pathophysiology of Traumatic Brain Injury.

Recently, traumatic brain injury (TBI) has been a growing disorder due to frequent brain dysfunction. The Glasgow Coma Scale expresses TBI as classified as having mild, moderate, or severe brain effects, according to the effects on the brain. Brain receptors undergo various modifications in their pathology through chemical synaptic pathways, leading to depression, Alzheimer's, and Parkinson's disease. These brain disorders can be controlled using central receptors such as dopamine, glutamate, and γ-aminobutyric acid, which are clearly explained in this review. Furthermore, there are many complications in TBI's clinical trials and diagnostics, leading to insignificant treatment, causing permanent neuro-damage, physical disability, and even death. Bio-screening and conventional molecular-based therapies are inappropriate due to poor preclinical testing and delayed recovery. Hence, modern nanotechnology utilizing nanopulsed laser therapy and advanced nanoparticle insertion will be suitable for TBI's diagnostics and treatment. In recent days, nanotechnology has an important role in TBI control and provides a higher success rate than conventional therapies. This review highlights the pathophysiology of TBI by comprising the drawbacks of conventional techniques and supports suitable modern alternates for treating TBI.

Excited state absorption induced optical limiting behavior of pure, single, and co-doped copper oxide nanoparticles

Underneath nano pulsed green laser (Nd: YAG), nonlinear absorption and optical limiting behavior were analyzed using Z-scan technique for pure CuO, Ag, and Mn-doped CuO (single dopant), and Ag/Mn-doped CuO (co-dopant) nanoparticles intermediated from M. Oleifera leaf extract. X-ray diffraction pattern confirmed that the synthesized nanoparticles were in good crystalline nature with a monoclinic phase and the average crystallite size was estimated in the range of nanometer. FE-SEM analysis displayed that the pure CuO, Ag-doped CuO, and Ag/Mn-doped CuO appear as nanospheres whereas Mn-doped CuO forms themselves as nanorods. The existence of Cu, O, Ag, and Mn elements in synthesized nanoparticles was affirmed by an EDAX spectrum. FT-IR analysis confirms the presence of functional groups. In zeta potential analysis the negative (-ve) potential values −34.23 mV to −34.80 mV indicate the stability of the nanoparticles. The optical study revealed that the nanoparticles possess absorbance maxima in the UV region between 260 nm to 294 nm. The occurrence of a single ionized oxygen vacancy defect was affirmed by the photoluminescence studies. Z-scan studies with nano pulsed Nd: YAG lasers show all the samples exhibit two-photon absorption (2 PA) and optical limiting behavior. In contrast with pure and co-dopant materials (Ag/Mn-doped CuO), the dominant nonlinear absorption coefficients (0.90 × 10−10 m/W, & 0.98 × 10−10 m/W) and submissive values of optical limiting threshold (1.69 × 1012 W/m2 & 1.31 × 1012 W/m2) were found for single dopant materials (Ag & Mn-doped CuO). Thus single metal doped CuO finds potential application in the creation of laser safety devices against massive power nano pulsed green laser beams.

Insights into nonlinear absorption transitions in a silver-incorporated reduced graphene oxide-molybdenum disulfide (Ag-rGO-MoS2) hybrid.

Optical nonlinearity in a silver-decorated reduced graphene oxide-molybdenum disulfide (Ag-rGO-MoS2) nanocomposite was experimentally investigated via the Z-scan technique using a Q-switched Nd:YAG nanopulsed green laser. An interesting switching behaviour from saturable to reverse saturable absorption with varying input on-axis intensity of the laser was demonstrated. Under low-intensity laser excitation, Ag-rGO-MoS2 displayed ground-state bleaching, which resulted in saturable absorption (SA) behaviour. Here, the prominent SPR phenomenon of Ag enforced plasmon absorption and is assigned to the SA process. Interestingly at higher intensity, the material switched its nonlinearity to reverse saturable absorption (RSA), attributed to two different mechanisms of two-photon absorption (2PA). At moderate laser pulse energies, the sample underwent sequential 2PA, which is underpinned by calculated varying nonlinear optical parameters and excited-state absorption cross-sections. However, at higher intensities, nonlinear absorption coefficients and excited-state absorption cross-sections remained constant, indicating the occurrence of genuine 2PA. In addition, theoretical estimation of the 2PA cross-section validates the observed transition. Thus, experimental evidence for the validity of nonlinear absorption theory (intensity-dependent transition from linear to nonlinear SA to nonlinear RSA to genuine 2PA via sequential 2PA) is provided for the first time in the literature.

Optic pit maculopathy: incidence and clinical course

The aim of this case series was to investigate the clinical course of patients with optic pit maculopathy. The medical records of all patients diagnosed with optic pit maculopathy in the past 10years were reviewed. Optic pit maculopathy was diagnosed when localized intraretinal or/and subretinal fluid spread from the optic nerve to the macula. Outcome measures included changes in best corrected visual acuity (BCVA), central retinal thickness (RT) as well as nasal parafoveal and perifoveal RT. An optic disc pit was detected in 18patients (9female, 9male, mean age: 33 ± 23years). Retinal fluid accumulation was present in 6(33.3%) of the patients (1intraretinal, 1subretinal, 4intraretinal and subretinal). Pars plana vitrectomy with removal of peripapillary vitreous traction and peeling of the internal limiting membrane (ILM) was indicated in 5patients and was performed in 4patients. One patient underwent nanopulse laser treatment instead. The patients with optic pit maculopathy were 47 ± 16years old. In this group of patients, mean BCVA (decimal) improved from 0.3 ± 0.2 before treatment to 0.5 ± 0.2 3months after treatment (p = 0.03). Visual acuity improved in all patients with optic disc pit maculopathy after pars plana vitrectomy. The mean central RT decreased from 796 ± 214 before treatment to 324 ± 57 3months after treatment (p = 0.005). The mean nasal parafoveal RT decreased from 683 ± 87 before treatment to 372 ± 41 (p = 0.0003) and the mean nasal perifoveal RT decreased from 547 ± 89 before treatment to 360 ± 48 (p = 0.007). Acompletely dry macula was achieved in 4eyes after amean follow-up of 3months. At long-term follow-up (2.5 ± 1.2years), no recurrence occurred in the vitrectomized eyes. This case series showed that more than one third of the patients had optic pit maculopathy presumably caused by disruption of the Kuhnt intermediate tissue. Interventional treatment was indicated in all cases, of which 4were surgically treated and resulted in significant improvement of function and anatomical retinal structures.

Demonstration of Enhanced Saturable Absorption in Upconverter Integrated MoS2 Heterostructure Thin Film Using Nanopulsed Green Laser

Upconverter/MoS2 heterostructure thin films fabricated by hydrothermal technique are confirmed by X‐ray diffraction and Raman studies. Field‐emission scanning electron microscopy (FESEM) and high‐resolution transmission electron microscopy (HRTEM) reveal the nanobelt structured MoS2 mingled with trapezoid structure fluoride upconverters and sphere‐shaped oxide upconverters. The films exhibit green () and red () emission. The influence of upconverters on the nonlinear absorption of MoS2 is exploited by Z‐scan technique using nanopulsed laser. Estimated ground‐state absorption cross section is higher than the excited‐state absorption cross section of the samples and it confirms the occurrence of saturable absorption. CeO2:Yb,Er@MoS2 exhibits stronger saturable absorption due to synergetic effects like higher linear absorption coefficient at 532 nm, stronger green emission, and reduced size. Results pave way for the design of optical switches, Q‐switches, and mode lockers using upconverter integrated MoS2 thin films.

A Comparative Study on the Effect of Peri-Implant Infection Management Lasers (1064-nm Q-Switch Nd:YAG, 1064-nm Nd:YAG and 980-nm Diode) on Titanium Grade 4 Surface

Over the past 10 years, the number of dental implants has grown significantly. This increase has consequently led to an elevation of the statistics related to cases of peri-implantitis. Laser therapy has conquered a place among the therapies of excellence to treat peri-implantitis. However, the laser device used could influence the therapy’s success. The aim of this comparative experimental work was to highlight the differences in the work on grade 4 titanium surfaces of the most commonly used laser lights in this field, taking into consideration any structural damage that lasers could cause to implant surfaces. The lasers examined were a 980 nm diode laser; a 1064 nm Nd:YAG laser; and a new generation of 1064 nm Nd:YAG Q-switch nano pulsed laser. We evaluated the titanium temperature increase, the pre- and post-treatment two-dimensional surface appearance observed under the scanning electron microscope; finally, the three-dimensional pre- and post-treatment topographic analysis was assessed using atomic force microscopy. We showed that the 1064-nm Q-switch Nd:YAG nanosecond pulsed laser appears to be more suitable for the preservation of implant morphology because of the absence of the induction of metal damage.

Light-Controlled Direction of Distributed Feedback Laser Emission by Photo-Mobile Polymer Films.

We report on the realization of Distributed Feedback (DFB) lasing by a high-resolution reflection grating integrated in a Photomobile Polymer (PMP) film. The grating is recorded in a recently developed holographic mixture basically containing halolakanes/acrylates and a fluorescent dye molecule (Rhodamine 6G). The PMP-mixture is placed around the grating spot and a subsequent curing/photo-polymerization process is promoted by UV-irradiation. Such a process brings to the simultaneous formation of the PMP-film and the covalent link of the PMP-film to the DFB-grating area (PMP-DFB system). The PMP-DFB allows lasing action when optically pumped with a nano-pulsed green laser source. Moreover, under a low-power light-irradiation the PMP-DFB bends inducing a spatial readdressing of the DFB-laser emission. This device is the first example of a light-controlled direction of a DFB laser emission. It could represent a novel disruptive optical technology in many fields of Science, making feasible the approach to free standing and light-controllable lasers.

A comparative analysis on electrical and nonlinear optical properties of pure and Co–Ni co-doped SnO2 nanoparticles

Compared to bulk materials, nanostructured materials possess ultrafast optical response and strong two-photon absorption which leads to the utility of materials in various laser related applications. Hence, Cobalt (Co)-Nickel (Ni) co-doped SnO2 nanoparticles were synthesized via co-precipitation technique and its optical limiting behavior was studied. PXRD confirms the formation of tetragonal rutile SnO2with space group P42/mnm with decrease in crystallite size due to co-doping. Shift in PXRD peak position towards higher angle and suppression of Sn–O–Sn vibrational peaks confirm the intervention of Co2+ and Ni2+ ions into the SnO2 lattice. Upon co-doping, the band gap decreases (3.35, 3.28 and 3.20 eV) and the PL intensity of blue-green emission increases due to the increase in density of oxygen vacancies on the surface of SnO2. Low dielectric constant, dielectric loss and ac conductivity indicates the prepared materials are having lesser defects. Nonlinear optical (NLO) absorption and optical limiting behavior of developed NPs were recorded by Z-scan method (open aperture) using nano pulsed green laser excitation. Open aperture Z-scan curves with a valley-like pattern indicate the presence of reverse saturable nonlinear absorption due to the sequential two-photon absorption (2PA) process. The 2PA coefficient increases (0.27–0.56 ×10−10W/m) and onset optical limiting threshold decreases (4.5 –1.7 ×10−12W/m2) with increasing dopant concentration of Co–Ni (2 & 4 wt%) in SnO2 NPs. These results demonstrate that Co–Ni (4 wt%) NPs have virtuous dielectric and efficient NLO absorption and limiting properties which suggest that it could be an eminent candidate for the potential applications such as high-performance dielectric material and optical limiting components in optical devices.

The anticancer activity of doxorubicin-loaded levan-functionalized gold nanoparticles synthesized by laser ablation

Here, gold nanoparticles (AuNPs) were synthesized upon exposure to nano-pulsed Nd-YAG laser irradiation in de-ionized water (PLAL) and functionalized with levan polysaccharide for assessing the anticancer efficacy of doxorubicin (DOX)-conjugated levan-capped AuNPs complexes to MCF-7 breast cancer cells. According to the physicochemical test results, the increments in levan amount enhanced the colloidal stability and the drug encapsulation efficiency (DEE) significantly. For the 10L-AuNP group having the highest levan amount (10 mg/mL levan), DEE was calculated as 92.21 ± 0.56%. The lean levan, uncapped AuNPs, and 10L-AuNP were found non-cytotoxic (>80% cell viability) in the studied concentrations with 48 h MTT assays. At higher DOX loadings (25, 50, and 100 μg/mL) of 10L-AuNP, the cell viability reduced significantly compared to free DOX. Overall, these nanoparticle complexes could be proposed as potent drug delivery vehicles for cancer drugs such as DOX, as well as other drugs in the prospective studies.

Treating hippocampal neural stem cells with nano‐pulsed laser therapy generates neurons with decreased sensitivity to toxic Aβ oligomers

Synaptic dysfunction driven by toxic amyloid oligomers (Abo and Tauo) is an early event leading to cognitive decline in Alzheimer's disease (AD). We have shown that transcranial treatment of adult wt mice with near-infrared light decreases synaptic vulnerability to Aβo. We have also shown that preserved neurogenesis correlates with synaptic resilience and preserved cognitive function in non-demented individuals with AD neuropathology. Here we sought to determine whether treating hippocampal neural stem cells (NSCs), the primary source of neurogenesis in the adult brain, with Nano-Pulsed Laser Therapy (NPLT), combining near-infrared light irradiation (808nm) with ultrasonic optoacoustic waves, could lead to the generation of neurons with decreased synaptic vulnerability to Aβo toxicity.Adult rat hippocampal NSCs were treated for five minutes with NPLT (10ms pulse duration, 20Hz pulse frequency, 4.3mJ total energy) or sham treatment and allowed to differentiate into mature neurons (MN) for five days. For analysis of Abo binding, MNs were exposed to 2.5µM Fluor-647-labeled Aβo for 30 minutes at 37⁰C and immunostained for βIII-tubulin. The number of Aβo puncta on neurites was quantified using ImageJ. For analysis of mitochondrial function, Aβo-treated MNs were incubated with the mitochondrial membrane potential-dependent dye, MitoTracker Deep Red (MTDR) and potential-independent MitoTracker Green (MTG). Flow cytometric analyses of MTDR (healthy mitochondria) and MTG (total mitochondria) was conducted at 30 minutes post-Aβo treatment.MNs generated from NPLT-treated NSCs showed significantly fewer Aβo puncta per neurite compared to MNs from sham-treated NSCs (p=0.0049), and lower percentage of total neurites with bound Aβo (p<0.0001) (Figure 1). We also found that Aβo treatment induced a significant reduction in both total mitochondria and mitochondrial membrane potential in MNs from sham-treated NSCs but not in MNs from NPLT-treated NSCs (Figure 2).Here we show that NSCs treated with NPLT generate MNs resistant to Aβo binding and to Ab-induced mitochondrial dysfunction. These data suggest that NPLT, which is currently approved for use in humans for unrelated clinical applications, could be a valuable therapeutic tool for inducing cognitive resilience to AD neuropathology.

Excited state absorption induced optical limiting action of MoS2-rGO nanocomposites

Molybdenum sulphide-reduced graphene oxide nanocomposite made of microsphere MoS2 with varying concentration of layered (15, 30, 45 wt%) rGO was prepared by hydrothermal method. XRD confirms the molecular formation of mixed phase MoS2 having rich semiconducting hexagonal phase with traces of metallic tetragonal phase (1T@2H MoS2) and reduced graphene oxide (2θ = 25.7°, (002)). Further EDS also ascertains the reduction of Mo and S with increase in C content with respect to rGO concentration. As the rGO concentration increases (15–45 wt%), strengthening of characteristic Raman peaks of rGO (G and D band) and weakening of MoS2 (E1g, E2g1 and A1g modes) in composite was observed. Estimated ID/IG (1.04) and I2D/IG (0.62) ratio suggest the formation of 2–3 layers of graphene. SEM depicts layered morphology of rGO, floret like microstructure of MoS2 and floret microspheres MoS2 decorated rGO layers of MoS2 – rGO nanocomposite. Optical studies show absorption peaks at 266 nm (π-π* transition of the CC aromatic bonds of graphene), 370 nm (and n-π* transition of the CO bond of graphene) and 330 nm (direct transitions in valence to conduction band of MoS2). Liquid dispersion of both pristine and composite depicted strong absorption in UV–Visible region and available electronic state favours the opportunity for two-photon absorption. Intensity dependent Z-Scan with nano-pulsed green laser excitation shows the existence of excited state absorption involved two-photon absorption. Variation of saturation intensity and nonlinear absorption coefficient with on-axis peak intensity (620 –2160 GW/cm2) confirms the involvement of sequential 2PA process (1PA + ESA). MoS2-(30 wt%)rGO nanocomposite exhibited higher 2PA coefficient (9.42 × 10−10 m/W) and lower onset optical limiting threshold (3.15 × 1012 W/m2) than its pristine counterparts and other well-known TMDC’s and graphene derivatives. Enhanced NLO response is due to synergistic effects of rGO (higher defect induced states, extended conjugation for charge transfer) and MoS2 (floret morphology, uniform decoration and strong visible absorption). Observed excited state absorption induced energy absorbing optical limiting action of MoS2-rGO nanocomposite with augmented NLO coefficients open up potential horizon for developing laser goggles against most sensitive and widely used nanopulsed green laser.

A novel chlorocadmate hybrid cocrystal delivering intermolecular charge transfer enhanced nonlinear optical properties and optical limiting

Employing the donor-acceptor configuration of cocrystals, the intermolecular charge transfer enhanced third order nonlinear optical properties and the optical limiting behaviour of a novel chlorocadmate cocrystal Cd 2 Cl 6 OH 2 2 C 4 H 12 N 2 n ( 1 ) are reported. Optimization of crystal growth parameters is discussed to achieve bulk single crystal with reduced crystal defects by slow solvent evaporation technique. The acid hydrolysis of the piperazine molecule during the pH optimization converted it into piperazine-1,4-diium, which is neutralized by Cd 2 Cl 6 OH 2 2 2 - via hydrogen bond interactions. The intermolecular charge transfer responsible for optical nonlinearity in 1 is proved possible by calculating the intermolecular interaction energies at HF/3-21G level of quantum mechanical calculations. The two-photon absorption coefficient measured at different nanosecond pulsed laser intensities is found to vary, which explicitly confirmed sequential 2 PA in 1 . Lower optical limiting threshold of 1 measured under CW and nanosecond pulsed green laser regime ( ( 1.027 ± 0.02 ) × 10 3 Wcm -2 and ( 1.87 ± 0.02 ) × 10 12 Wm -2 respectively) with coherent dielectric, thermal, mechanical, linear absorption and emission properties showed its suitability for an efficient optical limiting device application. • A Novel intermolecular charge transfer cocrystal for NLO applications is reported. • Sequential two-photon absorption was conclusively proved from intensity-dependent β. • Intermolecular charge transfer interactions assisted optical nonlinearity is proved possible in the title material. • Third order nonlinear optical susceptibility (χ (3) ) of title cocrystal is found to be (0.527 ± 0.008) × 10 −6 esu. • Optical limiting threshold of title cocrystal for nano pulsed (100 mJ, 532 nm) and CW (100 mW, 532 nm) laser irradiance are calculated.

A study on the electrical, magnetic and optical limiting behaviour of Pure and Cd-Fe co-doped CuO NPs

Copper Oxide (CuO) Nanoparticles (NPs) in pure and doped form (cadmium (Cd) - iron (Fe)) co-doped (2 & 4 wt%)) were developed via employing simple co-precipitation method. PXRD pattern shows that there is no impurity in the single-phase monoclinic structure. The agglomeration of needle-like, flake-like and spherical-like morphologies for undoped and Cd-Fe (2 & 4 wt%) co-doped CuO NPs are examined through SEM analysis. From UV–Vis DRS spectra, the obtained optical band gap of the synthesized materials was found to be 2.38, 2.62 and 2.77 eV for undoped and Cd-Fe (2 & 4 wt%) co-doped CuO NPs. PL spectrum confirms the slight variation in emission wavelength compared to undoped CuO NPs. At different temperatures, electrical conductivity measurements of synthesized samples are estimated by the dielectric constant, dielectric loss and ac conductivity with different frequencies. VSM analysis exhibits a maximum saturation magnetization (0.02159 emu/g) for Cd-Fe co-doped CuO NPs (4 wt%), which reveals the synthesized samples can be a probable candidate for optoelectronics and spintronic device fabrication. The nonlinear absorption and optical limiting properties were investigated by using open aperture Z-scan method under nano pulsed green laser excitation. With increased Cd-Fe concentration, the two-photon absorption coefficient increases from 3.0×10−10W/m to 4.8×10−10W/m. Both undoped and Cd-Fe co-doped CuO NPs exhibit two-photon absorption induced optical limiting action with lower onset optical limiting threshold and thus can be used for the development of the laser protection devices against widely used high power nano pulsed green laser.

Excited state absorption of Cu-doped barium borate nanostructures under nanopulsed laser excitation

Intensity- and concentration-dependent nonlinear absorption of Cu-doped ( $$\gamma $$ and $$\beta )$$ - $$\hbox {BaB}_{2}\hbox {O}_{4}$$ nanostructures was measured by a standard open aperture Z-scan setup under nanopulsed (9 ns, 10 Hz) laser excitation (532 nm) at various peak intensities (1.26–2.52 GW/ $$\hbox {cm}^{2})$$ . Intensity-dependent 2PA coefficient exposes the involvement of accumulative 2PA process rather than genuine 2PA. From ground state absorption studies, existence of new energy states due to Cu incorporation has availed a near-resonant state favoring excited state absorption leading to sequential 2PA. Among the samples, 0.05 M Cu-doped $$\gamma $$ - $$\hbox {BaB}_{2}$$ $$\hbox {O}_{4}$$ $$(2.6\times 10^{-10}$$ m/W, $$0.78\times 10^{12}$$ $$\hbox {W}/\hbox {m}^{2})$$ and 0.03 M Cu-doped $$\beta $$ - $$\hbox {BaB}_{2} \hbox {O}_{4}$$ $$(2.5\times 10^{-10}$$ m/W, $$1.21\times 10^{12}\hbox {W}/\hbox {m}^{2})$$ exhibit higher 2PA coefficient and lower onset limiting threshold. The presence of CT and intragap states of $$\hbox {Cu}^{2+}$$ ions-induced strain in visible region transformed genuine 2PA in pristine ( $$\gamma $$ and $$\beta )$$ - $$\hbox {BaB}_{2}$$ $$\hbox {O}_{4}$$ nanorods into sequential 2PA (1PA $$+$$ 2PA) in Cu-doped ( $$\gamma $$ and $$\beta )$$ - $$\hbox {BaB}_{2}$$ $$\hbox {O}_{4}$$ . By simple hydrothermal process, concentration-dependent Cu-doped ( $$\gamma $$ and $$\beta )$$ - $$\hbox {BaB}_{2}$$ $$\hbox {O}_{4}$$ nanostructures were prepared and their structural and optical properties were studied. Thus, Cu-doped ( $$\gamma $$ and $$\beta )$$ - $$\hbox {BaB}_{2}$$ $$\hbox {O}_{4}$$ exhibit sequential 2PA (1PA $$+$$ ESA)-based optical limiting with enhanced 2PA coefficient than its pristine ( $$\gamma $$ and $$\beta )$$ - $$\hbox {BaB}_{2}$$ $$\hbox {O}_{4}$$ nanorods.

Non-Invasive Transcranial Nano-Pulsed Laser Therapy Ameliorates Cognitive Function and Prevents Aberrant Migration of Neural Progenitor Cells in the Hippocampus of Rats Subjected to Traumatic Brain Injury.

Traumatic brain injury (TBI) can lead to chronic diseases, including neurodegenerative disorders and epilepsy. The hippocampus, one of the most affected brain region after TBI, plays a critical role in learning and memory and is one of the only two regions in the brain in which new neurons are generated throughout life from neural stem cells (NSC) in the dentate gyrus (DG). These cells migrate into the granular layer where they integrate into the hippocampus circuitry. While increased proliferation of NSC in the hippocampus is known to occur shortly after injury, reduced neuronal maturation and aberrant migration of progenitor cells in the hilus contribute to cognitive and neurological dysfunctions, including epilepsy. Here, we tested the ability of a novel, proprietary non-invasive nano-pulsed laser therapy (NPLT), that combines near-infrared laser light (808 nm) and laser-generated, low-energy optoacoustic waves, to mitigate TBI-driven impairments in neurogenesis and cognitive function in the rat fluid percussion injury model. We show that injured rats treated with NPLT performed significantly better in a hippocampus-dependent cognitive test than did sham rats. In the DG, NPLT significantly decreased TBI-dependent impaired maturation and aberrant migration of neural progenitors, while preventing TBI-induced upregulation of specific microRNAs (miRNAs) in NSC. NPLT did not significantly reduce TBI-induced microglia activation in the hippocampus. Our data strongly suggest that NPLT has the potential to be an effective therapeutic tool for the treatment of TBI-induced cognitive dysfunction and dysregulation of neurogenesis, and point to modulation of miRNAs as a possible mechanism mediating its neuroprotective effects.

Laser excitation dependent nonlinear absorption of 2-Amino 5-Nitropyridinium dihydrogen phosphate

Laser excitation and intensity-dependent third-order nonlinear optical (NLO) absorption properties of 2-amino 5-nitropyridinium dihydrogen phosphate (2A5NPDP) in both pulsed (532 nm, 5 ns, 100 µJ) and continuous wave (532 nm, 50 mW) regime were studied by Z-scan experiment. Under CW laser excitation, 2A5NPDP exhibits saturable absorption (SA) ascribed to be of thermo-optic origin. Interestingly the sample show reverse saturable absorption (RSA) due to genuine two-photon absorption (2PA) process under nano pulsed laser excitation. Earlier thermodynamic properties such as thermal conductivity (51 W/m.K), specific heat capacity (3894 J/Kg.K) and thermal diffusivity (7.5 × 10−6 m2/s) were estimated theoretically from the DSC curves. Thus 2A5NPDP with excellent thermal stability and high NLO coefficients can be utilized as an energy-absorbing optical limiter and saturable absorber under nano pulsed and CW green laser excitation.

Nanosecond Laser Treatment in Chorioretinopathia Centralis Serosa without RPE Defects: A Retrospective Case Series

Chorioretinopathia centralis serosa (CCS) is a uni- or bilateral disease of the macula which is characterized by detachment of the neuro-sensory retina. The spontaneous resolution rate is 68% after four months and 84% after six months. To investigate the efficacy of subthreshold nanopulse laser treatment for central serous chorioretinopathy (CCS) in the absence of any atrophy in the retinal pigment epithelium (RPE). This retrospective study comprised 23 eyes of 23patients without previous treatment. Patients were followed up to 12 months. Laser treatment was performed with the 2RT® nanolaser using a grid stimulation. Changes in corrected visual acuity (VA), microperimetry and subretinal fluid height in optical coherence tomographic images were measured. Saliences in autofluorescence images and angiographic images were observed. All results were documented 1, 3, 6 and 12 months after the first treatment. Patients did not receive any supplementary treatment. Two months after the first treatment, 74% of the patients showed complete SRF resolution and 91% of the patients within 6 months had complete resorption of the SRF. Central visual acuity and macula sensitivity significantly improved from 0.18 ± 0.16 logMAR to 0.09 ± 0.17 logMAR and 24.19 ± 3.96 dB to 27.59 ± 2.89 dB. The SRF decreased within one month significantly. No CNV was documented during the observation time. The baseline subretinal fluid height is a predictive factor of faster resolution. The evaluation of our treatment results shows that the therapy is a safe and promising method. Patients with a CCS without existing RPE defects benefit from the treatment with the 2RT® nanolaser, which is associated with an improvement of the macula function.

Energy absorbing and energy spreading optical limiting action of 2-amino 5-nitropyridinium derivatives

By Nd:YAG green laser driven Z-scan experiment, nonlinear optical properties of 2-amino 5-nitropyridinium derivatives (2A5NPCl and 2A5NPBr) are studied. Both the samples exhibit genuine 2 PA induced electro-optic based optical limiting action process under pulsed (5 ns, 100 μJ) mode. And they display self-defocusing promoted thermo-optic based optical limiting action under continuous wave (50 mW) mode. NLO coefficients and thermodynamic properties of 2A5NPBr is higher than 2A5NPCl. Results show 2A5NPBr molecular liquids are superior for energy absorbing and energy spreading optical limiting applications to prevent the laser damages from nano pulsed and CW green laser excitation.

Preparation of Superhydrophobic 35CrMo Surface and Its Tribological Properties in Water Lubrication

The process of oil exploitation is often accompanied by the generation of the corrosive gases, metal particles and minerals, which results in very serious corrosion and wear of petroleum machinery and equipment, which can be greatly reduced by modification of the surface properties of the materials. According to the theory of molecular interaction, the friction effect of a rough surface is better than that of a smooth surface, while fabrication of surfaces with appropriate roughness may reduce the friction. We present the construction of a grooved texture on the surface of 35CrMo using a nano-pulse laser. We found that some micro-/nano-structures were created on the surface, and that a superhydrophobic surface with a water contact angle of 156° and a sliding angle of less than 10° was obtained. Groove textures of different depths produced by using various laser energy densities, the friction coefficient of the superhydrophobic samples was significantly reduced from 0.55 to 0.28 after laser surface texturing under water lubrication conditions. This shows the improvement of the tribological properties.