Laser Irradiation Research Articles

Time-dependent 532 nm laser irradiation for tuning in optical, structural, and surface wettability changes of Te/In2Se3 thin films for optoelectronic applications

Laser irradiation for tuning the optoelectronic parameters of semiconducting thin films is widely applicable and has many benefits. The aim of the study is 532 nm laser irradiation of Te/In2Se3 film at different laser exposure time scales. The bilayer structure and its conversion to a single layer with laser annealing were confirmed from cross-sectional scanning electron microscopy. At the same time, the element's appearance was found in the EDX analysis. FESEM probed the corresponding surface structure change. XRD and Raman's spectroscopy analyzed the increase in crystallinity with laser irradiation by mixing Te into the In2Se3 layer and related microstructural changes. The shift in Raman peak with lasing time signifies the effect of time of exposure. There is a systematic decrement in the transmittance of the films. Also, the absorption edge shift resulted in the decrement in bandgap with laser irradiation. The static refractive index and optical density increased as well. The skin depth was decreased with a minimal change in the optical electronegativity. The nonlinear refractive index increased from 1.638 × 10–9 esu to 1.773 × 10–9 esu by 60 min laser irradiation. Similarly, there was an increment in 3rd-order nonlinear susceptibility from 1.58 × 10–10 esu to 1.73 × 10–10 esu. The surface wettability test confirmed the hydrophilic nature of the samples with decreasing hydrophilicity by laser irradiation. The tuning in different properties of the Te/In2Se3 film by laser irradiation is suitable for various optoelectronic applications.

Irradiating the Path to High-Efficiency Zn-Ion Batteries: An Electrochemical Analysis of Laser-Modified Anodes.

Global energy consumption is increasing yearly, yet the world is trying to move toward carbon neutrality to mitigate global warming. More research is being done on energy storage devices to advance these efforts. One well-known and widely studied technology is Zn-ion batteries (ZIBs). Therefore, this paper demonstrates how laser irradiation at wavelengths of 266 and 1064nm, in the presence of air or water, can enhance the electrochemical performance of metallic zinc anode in alkaline electrolyte. The obtained samples are characterized using X-ray diffraction analysis, scanning electron microscopy, and Raman spectroscopy. Then, the electrochemical properties are studied by cyclic voltammetry and impedance measurements. Results indicate that the laser processing of the Zn sample increases surface-specific capacity by up to 30% compared to the non-irradiated Zn sample. Furthermore, electrochemical measurements reveal enhanced participation of metallic Zn grains in the oxidation and reduction processes in irradiated samples. In future research, integrating laser treatment into electrode preparation processes can become essential for optimizing anode battery materials.

Enhanced SERS performance of Ag nanoparticles using hybrid dewetting process for melamine detection

A thermal evaporation system was used to deposit Ag thin films on glass substrates. The films were dewetted using both a regular laser irradiation approach and a hybrid dewetting process that involved laser irradiation followed by Ag thermal deposition. The study would evaluate and compare the optical characteristics and efficiency in melamine detection within these dewetted films. In the traditional dewetting process, as the laser power increased from 15 to 25 W, the nanoparticles (NPs) size decreased from 162 to 125 nm. Furthermore, an evident optical absorption peak range of 540–600 nm was also observed. Through the hybrid dewetting process, a mixture of small NPs (20 nm) and larger NPs (142–167 nm) were formed. It resulted in two distinct Surface Plasmon Resonance (SPR) peaks at 460 nm and 660 nm, respectively. Notably, a strong Raman peak at 701 cm−1 emerged when a melamine aqueous solution was placed on the hybrid dewetted surface. Comparing the two methods, the hybrid dewetted sample exhibited enhanced fingerprint peak intensity and a higher analytical enhancement factor (AEF). When operating at laser power of 25 W and a scanning speed of 100 mm/s, the maximum AEF value reached 1.9 × 105. The limit of detection for melamine solution in the hybrid dewetted sample was established at 10−7 M. Hence, the hybrid dewetting process is a potential method to produce the mixed-sized nanoparticles for diverse applications.

Nd: YAG laser irradiation in the treatment of live pulp preservation in pediatric cariogenic pulpitis.

Dental pulpitis significantly impacts oral function and quality of life. Treatments like direct pulp capping aim to preserve pulp vitality. This study aims to investigate the application value of Nd:YAG laser irradiation in preserving pulp vitality in children with caries-induced pulpitis. This study, conducted from June 2019 to June 2023, included 89 children undergoing pulp vitality preservation treatment for caries-induced pulpitis. The children were divided into two groups using sealed envelopes: 44 in the control group received pulp capping treatment, while the study group received Nd:YAG laser-assisted pulp capping treatment. The efficacy, oral indicators, oral function, changes in root apex diameter and root length, changes in gingival crevicular fluid inflammatory factors, and incidence of complications were compared between the two groups before and 3 months after treatment. The total effective rates were 97.78% in the study group and 95.45% in the control group, with no significant difference between the groups (p> 0.05). Before treatment, there were no differences in gingival index, plaque index, and probing bleeding index between the groups (p> 0.05). After treatment, both groups showed decreased periodontal indexes compared to before treatment, with the study group showing lower values than the control group (p< 0.05). Chewing and biting function scores were similar between the groups before and after treatment (p> 0.05), but both groups showed decreased scores after treatment (p< 0.05). The study group had a higher percentage decrease in root apex diameter and a greater increase in root length compared to the control group (p< 0.05). During treatment, one case of tooth discoloration occurred in the study group (2.27%), while the control group had two cases of tooth discoloration and one case of secondary caries, resulting in a complication rate of 6.67%. There was no significant difference in the incidence of complications between the groups (p> 0.05). Nd:YAG laser irradiation effectively preserves pulp vitality in children with caries-induced pulpitis, improving periodontal health, reducing root apex diameter, and increasing root length with high safety.

Silica-Ti3C2Tx MXene Nanoarchitectures with Simultaneous Adsorption and Photothermal Properties.

Layered Ti3C2Tx MXene has been successfully intercalated and exfoliated with the simultaneous generation of a 3D silica network by treating its cationic surfactant intercalation compound (MXene-CTAB) with an alkoxysilane (TMOS), resulting in a MXene-silica nanoarchitecture, which has high porosity and specific surface area, together with the intrinsic properties of MXene (e.g., photothermal response). The ability of these innovative MXene silica materials to induce thermal activation reactions of previously adsorbed compounds is demonstrated here using NIR laser irradiation. For this purpose, the pinacol rearrangement reaction has been selected as a first model example, testing the effectiveness of NIR laser-assisted photothermal irradiation in these processes. This work shows that Ti3C2Tx-based nanoarchitectures open new avenues for applications that rely on the combined properties inherent to their integrated nanocomponents, which could be extended to the broader MXene family.

Experimental and simulation studies on damage characteristics, crack development patterns, and strength reduction mechanisms of sandstone under laser irradiation

In order to explore the damage characteristics and crack development laws of hard rock under laser irradiation, laser irradiation experiments on sandstone were conducted considering the interaction of three laser parameters: spot diameter, laser power, and irradiation time. Subsequently, uniaxial compression experiments were conducted on sandstone samples before and after laser irradiation. In addition, based on the maximum principal stress intensity criterion and finite element software, laser induced fracturing sandstone simulation experiments were conducted. Research has found that: Laser irradiation significantly reduces the uniaxial compressive strength of sandstone, with a maximum reduction of about 88.9%, and is also accompanied by a significant decrease in elastic modulus. The degree of sandstone damage escalates with increasing laser power and irradiation time, alongside a reduction in spot diameter. Strong correlations were observed between the strength reduction rate and crack metrics like opening, area, and depth, enabling the establishment of a high-precision regression model. Cracks originate internally within sandstone, initially extending diagonally upwards toward the specimen’s surface before propagating outward. These findings elucidate the mechanisms behind sandstone’s strength reduction and crack propagation under laser irradiation, providing some insights for the practical application of laser rock breaking technology in engineering.

Distinguishing optical and acoustic phonon temperatures of supported 2D materials by nanosecond time-resolved Raman scattering.

Upon laser irradiation, 2D materials experience a cascading energy transfer from electrons to optical phonons (OPs) and then to acoustic phonons (APs), resulting in a significant thermal non-equilibrium among energy carriers. This non-equilibrium presents challenges for Raman-based thermal characterization, as Raman scattering measures only OP temperature rise, while APs are the primary energy carriers. Despite recent efforts to address this issue, OP-AP thermal non-equilibrium in supported 2D materials remains poorly resolved. Here, we develop a method to distinguish the OP and AP temperature rises based on their different temporal thermal responses under laser irradiation: the OP-AP temperature difference responds almost immediately (∼a few to tens of ps), while the AP temperature rise takes longer to establish (∼tens of ns). Using energy transport-state resolved Raman, we probe the transient thermal response of Si-supported nm-thick MoS2 from 20 to 100 ns. We find that the OP-AP temperature difference exceeds 120% of the AP temperature rise under ∼0.439 µm radius laser heating. The intrinsic interfacial thermal conductance of the samples, based on the true AP temperature rise, varies from 0.199 to 1.46 MW·m-2·K-1, showing an increasing trend with sample thickness.

Evaluation of the effect of self-assembling peptide and fluoride varnish, alone or in combination with laser irradiation, on artificial enamel caries: a SEM/EDS and Micro-CT study.

The aim of this study was to investigate the effect of remineralization agents such as fluoride varnish and P11-4, alone and in combination with Er: YAG laser, on in-vitro hard tissue repair in artificial enamel lesions. A total of sixty enamel surfaces of 4 × 5mm in size were created on both the buccal and lingual sides of thirty extracted wisdom teeth. Remineralization agents were applied to the specimens that were grouped as follows: Group 1, control; Group 2, fluoride varnish (FV); Group 3, P11-4; Group 4, laser; Group 5, laser + FV; and Group 6, laser + P11-4. The fluorescence level was determined with DiagnoDent. The enamel mineral density, area and volume, and caries lesion area and volume were determined with micro-computed tomography (µCT), surface features were evaluated using scanning electron microscopy (SEM), and elemental analysis was performed using energy dispersive x-ray spectroscopy (EDS) . For specimens treated only with self-assembling peptide P11-4, the caries lesion area (mm2) values were 38.19 and 21.62, and the caries lesion volume (mm3) values were 6.27 and 2.99, respectively for pre- and post-treatment. In combination usage of self-assembling peptide P11-4 and laser, the caries lesion area (mm2) values were 38.39 and 16.91, and the caries lesion volume (mm3) values were 11.15 and 3.64, respectively for pre- and post-treatment. In the application of the P11-4 alone and in combination with laser, there was a statistically significant decrease in DiagnoDent values, an increase in enamel volume(mm3),enamel area(mm2) and mineral density(g/cm3) values and a decrease in caries lesion volume(mm3) and area(mm2) obtained by µCT, and an increase in %Ca and %F values obtained by SEM/EDS analysis (p < 0.05). It was discovered that the samples treated with P11-4 had a considerably higher rise in the Ca/P ratio than the samples treated with FV (p < 0.05). The calcium content increased significantly more when P11-4 application was combined with laser irradiation (p < 0.05). The combined use of self-assembling peptide P11-4 and laser accelerated the remineralization process and increased the remineralization capacity. FV and P11-4, alone or in combination with laser, can be successfully used as remineralization agents in initial enamel caries.

Phase transitions and guest positions state in the nanodisperse TiO2 caused by laser irradiation

Phase transitions and guest positions state in the nanodisperse TiO2 caused by laser irradiation

Reversible modulations of insulator–metal transition in an epitaxial VO2 film through thermal crystallization and femtosecond laser-induced-amorphization of capping Ge2Sb2Te5 layer

We demonstrate reversible modulation of an insulator–metal transition (IMT) of a VO2 film grown on an Al2O3 (001) substrate through crystallization and re-amorphization of a chalcogenide germanium–antimony–telluride (Ge2Sb2Te5: GST) capping layer. After succeeding in the negative shift of IMT temperature (Tr) of the VO2 film through the crystallization of the GST layer accompanied by volume reduction, we performed re-amorphization of the crystalline GST by femtosecond laser irradiation. Under the optimized conditions of laser irradiation considering the penetration depth, re-amorphization of the GST layer was fully achieved, resulting in the shift-back of Tr toward a high-temperature side. Such a reversal of IMT through the crystallization and re-amorphization of the capping GST layer was demonstrated over two cycles. It was suggested that capping GST effectively induces interfacial strain modifications in the VO2 film underneath. Although the shifts in the IMT are still small, reversible modulation of IMT shown here will be beneficial for applications of VO2 films with controllable IMT.

Nanocarrier-based drug delivery system with dual targeting and NIR/pH response for synergistic treatment of oral squamous cell carcinoma

Oral squamous cell carcinoma (OSCC) is highly heterogeneous and aggressive, but therapies based on single-targeted nanoparticles frequently address these tumors as a single illness. To achieve more efficient drug transport, it is crucial to develop nanodrug-carrying systems that simultaneously target two or more cancer biomarkers. In addition, combining chemotherapy with near-infrared (NIR) light-mediated thermotherapy allows the thermal ablation of local malignancies via photothermal therapy (PTT), and triggers drug release to improve chemosensitivity. Thus, a novel dual-targeted nano-loading system, DOX@GO-HA-HN-1 (GHHD), was created for synergistic chemotherapy and PTT by the co-modification of carboxylated graphene oxide (GO) with hyaluronic acid (HA) and HN-1 peptide and loading with the anticancer drug doxorubicin (DOX). Targeted delivery using GHHD was shown to be superior to single-targeted nanoparticle delivery. NIR radiation will encourage the absorption of GHHD by tumor cells and cause the site-specific release of DOX in conjunction with the acidic microenvironment of the tumor. In addition, chemo-photothermal combination therapy for cancer treatment was realized by causing cell apoptosis under the irradiation of 808-nm laser. In summary, the application of GHHD to chemotherapy combined with photothermal therapy for OSCC is shown to have important potential as a means of combatting the low accumulation of single chemotherapeutic agents in tumors and drug resistance generated by single therapeutic means, enhancing therapeutic efficacy.

Analysis and Research on Energy Consumption of a Non-Contact High-Efficiency Tunnel De-Icing Device

In this paper, a laser deicing device for tunnel is designed to solve the inconvenience of deicing the tunnel roof wall. First of all, Solidworks software was used to create a 3D model of the laser deicing device, namely the track module, the base platform, and the work platform. Then, ANSYS simulation software is used to simulate the process of laser deicing. When the initial temperature of icicle is -5℃, -10℃, -15℃ and -20℃, the distance between laser and icicle is 1.5m, 2m, 2.5m and 3m, and the wind speed is 2m/s, 3m/s, 4m/s and 5m/s, respectively. The depth of 200s of laser irradiation and the time of full penetration were simulated under three variables. It is concluded that the higher the initial temperature, the closer the distance and the smaller the wind speed, the lower the deicing energy consumption. Finally, the experiment results are consistent with the simulation results, which further verifies the accuracy of the simulation. The laser deicing detection device studied in this paper provides a certain theoretical basis and reference value for the application and development of intelligent deicing equipment in tunnels.

Docetaxel-Encapsulated Catalytic Pt/Au Nanotubes for Synergistic Chemo-Photothermal Therapy of Triple-Negative Breast Cancer.

The combination of photothermal therapy with chemotherapy has emerged as a promising therapeutic modality for addressing triple-negative breast cancer (TNBC). This manuscript describes a novel hybrid nanoplatform comprising ultrathin catalytic platinum/gold (Pt/Au) nanotubes encapsulated with docetaxel and phase-change materials (PCMs) for the photoacoustic imaging-guided synergistic chemo-photothermal therapy of TNBC. Upon irradiation of near-infrared laser, the photothermal heating of nanotubes converts solid-state PCM into liquid, triggering the controlled release of the encapsulated docetaxel. The thin Pt layer within nanotubes enhances the nanotube's thermal stability, thus prolonging the photothermal ablation of tumors. Furthermore, platinum effectively mitigates tumor hypoxia by catalyzing the decomposition of hydrogen peroxides to generate oxygen in the tumor microenvironment, thus improving the efficiency of chemotherapy. It is demonstrated that the drug-loaded nanotubes achieve significant tumor inhibition rates of 75.4% in vivo on 4T1 tumor-bearing mice, significantly surpassing control groups. These nanotubes also notably extend survival, attributable to the synergistic effects of prolonged photothermal therapy facilitated by platinum and oxygenation-enhanced chemotherapy. This combination leverages the unique properties of the Pt/Au NTs-DTX/PCM nanoplatform, optimizing therapeutic outcomes. It is envisioned that this nanoplatform may find important applications in managing superficial malignant solid tumors in general.

Nucleic acid-functionalized gold nanoparticles as intelligent photothermal therapy agents for precise cancer treatment.

We present an intelligent photothermal therapy agents by functionalizing gold nanoparticles with specific nucleic acid sequences. Hairpin nucleic acids are modified to the nanoparticles, forming AuNPs-1 and AuNPs-2. Upon infiltrating cancer cells, these nanoparticles undergo catalytic hairpin assembly in the presence of target miRNA, leading to aggregation and subsequent photothermal conversion. Under near-infrared laser irradiation, aggregated gold nanoparticles exhibit efficient photothermal conversion, selectively damaging cancer cells. This approach offers heightened selectivity, as nanoparticles only aggregate in environments with cancer biomarkers present, sparing normal cells. Cytotoxicity assays confirm minimal toxicity to normal cells. In vivo studies on mice bearing solid tumors validate the system's efficacy in tumor regression. Overall, this study highlights the potential of nucleic acid-functionalized gold nanoparticles in intelligent and selective cancer photothermal therapy, offering insights for targeted diagnosis and treatment development.

Improving the surface characteristics of metallic glass thin ribbons by laser gas nitriding

The single-roll cooling method excels in producing metallic glass ribbons (MGRs), offering rapid cooling rates and exceptional thickness consistency. Nevertheless, a large number of defects including micro-pits and micro-gaps usually appear on the surface of MGRs after the roll forming process, significantly impacting their service life and performance. Laser gas nitriding is a cutting-edge surface modification technology that has been extensively used to improve the comprehensive performance of various metal components. Herein, an attempt was made to simultaneously improve the surface quality and mechanical properties of Zr41.2Ti13.8Cu12.5Ni10Be22.5 MGRs by nanosecond pulsed laser irradiation in a flowing nitrogen atmosphere. The effects of laser irradiation parameters on the surface characteristics of the laser gas nitrided regions were systematically investigated. The experimental results showed that the surface quality of MGRs after laser gas nitriding was enhanced, accompanied by a simultaneous improvement in hardness and scratch resistance. This study underscores laser gas nitriding as a potent strategy to augment the comprehensive surface characteristics of MGRs. This enhancement is poised to significantly extend their service life and reinforce their reliability when utilized as structural and functional materials in sectors such as machinery, national defense, and aerospace.

NIR-II femtosecond laser-induced nonlinear absorption facilitates foreground-extraction photoacoustic imaging by monolayer WS2-PVP nanosheets

Exogenous contrast agents have been extensively applied in photoacoustic (PA) molecular imaging for disease diagnosis, benefiting from their advantageous optical, thermal, and internal delivery properties. However, their in vivo performance was inevitably interfered by background tissue optical absorption, resulting in low imaging contrast and sensitivity. Here, we report a NIR-II femtosecond laser-induced nonlinearly enhanced PA imaging technique based on two-photon absorption of monolayer WS2-PVP nanosheets (NSs), which facilitates foreground extraction of the targeting region with the background signal being significantly suppressed. The optical nonlinearity of the monolayer WS2-PVP NSs was first demonstrated by a Z-scan system under the irradiation of a femtosecond laser to be 0.38, with an antithesis of virtually zero for the tissue-mimicking sample. Experiments on tissue-mimicking phantoms and in vitro chicken breast showed that the nonlinear PA enhancement of monolayer WS2-PVP NSs can facilitate foreground-extraction imaging at deep-seated position up to 4 mm. In addition, the in vivo foreground-extraction imaging ability by using monolayer WS2-PVP NSs was further demonstrated by mouse tumor models, where the tumor regions were specifically extracted with high imaging contrast. This work proposed a nonlinearly enhanced contrast mechanism of PA nanoprobes, prefiguring great potential for high-contrast and high-specificity PA molecular imaging.

NIR laser-activated phthalocyanine loaded lipid nanoparticles targeting M2 macrophage for improved photoacoustic imaging-guided photothermal therapy

The development of novel phototheranostic agents with significant potential in bioimaging-guided therapy is highly desirable for precise tumor therapy. Herein, NIR laser-activated ruthenium phthalocyanine (PcRu) loaded sub-30 nm targeting lipid nanoparticles (α-PcRu-NPs) were fabricated for photoacoustic imaging (PAI)-guided photothermal therapy (PTT). Due to the formation of J-type aggregation of PcRu in the core of the nanostructure, the α-PcRu-NPs exhibited high stability, efficient NIR absorption, reduced singlet oxygen generation, high photothermal activity, and intense photoacoustic signal. With the M2 macrophage target peptide (M2pep) modification and small size of α-PcRu-NPs, in vivo evaluations reveal that α-PcRu-NPs can specifically target and deeply penetrate the tumor foci. Under a high contrast PAI guidance with α-PcRu-NPs (744 nm, 0.35 μW), it also realizes superior photothermal therapy (PTT) for breast cancer under 670 nm laser irradiation (0.5 W/cm2). The prominent therapeutic efficacy of α-PcRu-NP-based PTT not only directly kills tumor cells, but also enhances the immune response by promoting dendritic cell maturation and increasing cytotoxic T cell infiltration. Thus, this work broadens the applications of phthalocyanine derivatives as phototheranostics in the PAI-guided PTT field.

Highly Sensitive Biosensors Based on All-PEDOT:PSS Organic Electrochemical Transistors with Laser-Induced Micropatterning.

Recent advances in numerous biological applications have increased the accuracy of monitoring the level of biologically significant analytes in the human body to manage personal nutrition and physiological conditions. However, despite promising reports about costly wearable devices with high sensing performance, there has been a growing demand for inexpensive sensors that can quickly detect biological molecules. Herein, we present highly sensitive biosensors based on organic electrochemical transistors (OECTs), which are types of organic semiconductor-based sensors that operate consistently at low operating voltages in aqueous solutions. Instead of the gold or platinum electrode used in current electrochemical devices, poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) was used as both the channel and gate electrodes in the OECT. Additionally, to overcome the patterning resolution limitations of conventional solution processing, we confirmed that the irradiation of a high-power IR laser (λ = 1064 nm) onto the coated PEDOT:PSS film was able to produce spatially resolvable micropatterns in a digital-printing manner. The proposed patterning technique exhibits high suitability for the fabrication of all-PEDOT:PSS OECT devices. The device geometry was optimized by fine-tuning the gate area and the channel-to-gate distance. Consequently, the sensor for detecting ascorbic acid (vitamin C) concentrations in an electrolyte exhibited the best sensitivity of 125 μA dec-1 with a limit of detection of 1.3 μM, which is nearly 2 orders of magnitude higher than previous findings. Subsequently, an all-plastic flexible epidermal biosensor was established by transferring the patterned all-PEDOT:PSS OECT from a glass substrate to a PET substrate, taking full advantage of the flexibility of PEDOT:PSS. The prepared all-plastic sensor device is highly cost-effective and suitable for single-use applications because of its acceptable sensing performance and reliable signal for detecting vitamin C. Additionally, the epidermal sensor successfully obtained the temporal profile of vitamin C in the sweat of a human volunteer after the consumption of vitamin C drinks. We believe that the highly sensitive all-PEDOT:PSS OECT device fabricated using the accurate patterning process exhibits versatile potential as a low-cost and single-use biosensor for emerging bioelectronic applications.

Protecting celtuce (Lactuca sativa L. var. augustana) slices against storage-induced oxidative stress and discoloration by using diode laser exposure

Diode laser irradiation is a novel approach applied to preserve the quality of fresh commodities and minimise oxidative processes, including browning in fresh-cut products. The objective of this study was to investigate the efficacy of diode laser treatment in enhancing the quality of celtuce slices during refrigerated storage at 4 °C. The celtuce slices were subjected to a 660 or 450 nm diode laser for 5 min and then stored for 10 d. Both laser treatments hindered the progression of weight loss and firmness increase in the celtuce slices. The use of a 450 nm diode laser effectively prevented the development of browning and preserved the surface colour by inhibiting the increase in a* and overall colour difference values, as compared to other treatments, during storage for 10 d. The diode laser treatment suppressed the increase in oxidative stress by lowering the levels of MDA, H2O2, and O-2 while retaining a high level of DPPH scavenging activity, AsA, and antioxdant enzyme activities, including SOD, CAT, APX, and GR, in comparison to the untreated slices. The treatment enhanced chlorophylls content due to the up-regulation of LsHEMA1 gene and down-regulation of LsNYC1 gene. The treatment also inhibited factors involving enzymatic browning reaction by suppressing PAL activity, total phenols content, PPO activity and LsPPO gene expression. These suggest that the blue diode laser exposure at 450 nm for 5 min is an effective approach hindering oxidative stress and discoloration of celtuce slices during storage.

Infrared microlens formation on chalcogenide polymer surface via femtosecond laser pulse ablation

In this study, we introduced micro-optical surface formation via femtosecond (fs) laser pulse scanning to chalcogenide polymer (ChP), a promising material for cost-effective infrared applications. Employing this method, we successfully fabricated a large-area poly(sulfur-random-(1,3-diisopropenylbenzene)) (S-r-DIB) microlens array (MLA) component. Each micro-concave spherical surface was crafted with a single fs laser pulse, serving as a micro-concave lens surface. We achieved a quasi-periodic MLA sample with over 2 × 105 micro-lenslets within a 10 mm × 10 mm footprint. Additionally, precise locating of laser pulse irradiation enabled us to create a hexagonal MLA with a filling factor over 37 %. Morphological investigations and imaging tests confirmed the adequate surface quality of the fabricated components, with its uniformity revealed by the virtual foci grid in near infrared region. To elucidate the forming conditions and mechanisms, we studied the evolution of surface morphology under various laser irradiation conditions. Laser induced damage thresholds of S70-r-DIB30 were experimentally determined for both 800 nm and 400 nm wavelengths under single- and multi-pulse irradiation scenarios. We identified the optimal fabrication fluence window as 115–205 mJ/cm2 with 800 nm single-pulse irradiation. The bandgap of the S70-r-DIB30 was estimated as 2.06 eV, and energy band analysis confirmed distinctions in ablation morphology. Furthermore, we investigated sub-surface morphology evolution using orthogonal ultrafast pump–probe imaging, revealing diversity compared to traditional inorganic and polymeric optical materials due to differing absorption and etching mechanisms. The elastic wave velocity of 3.2 km/s in this ChP and etching velocity of 0.7 μm/pulse were experimentally determined. These findings deepen our understanding of ChP material interaction with fs lasers, offering insights for potential applications such as surface engineering, substrate cutting, and micro-structure formation.