308-nm Excimer Laser Research Articles

The 308-nm excimer laser treatment does not increase the risk of skin cancer in patients with vitiligo: A population-based retrospective cohort study.

A 308-nm excimer laser (EL) has been widely used to treat patients with localized vitiligo. However, data are rare on the influence of EL treatment on the risks of skin cancer. To evaluate the skin cancer risks after long-term EL treatment, we performed a nationwide population-based retrospective cohort study using the Korean National Health Insurance Claims Database. A total of 5,052 patients with vitiligo were classified into three groups according to the EL treatment sessions between 2009 and 2016: no, 50-99, and 100 or more EL treatments after 2-year washout period (2007 and 2008). Using multivariable Cox proportional hazard models, we found that the risks of actinic keratosis, non-melanoma skin cancers, and melanoma did not significantly differ among the groups, respectively. In conclusion, EL treatment would not increase the risks of premalignant skin lesions and skin cancers in patients with vitiligo. Based on our results, EL is likely to be a safe treatment option for patients with localized vitiligo.

Endothelial cell density and corneal graft thickness following excimer laser vs. femtosecond laser-assisted penetrating keratoplasty\u2014a prospective randomized study

PurposeThe study aims to compare the impact of non-mechanical excimer laser-assisted (EXCIMER) and femtosecond laser-assisted (FEMTO) trephinations on graft endothelial cell density (ECD) and graft thickness before and after suture removal following penetrating keratoplasty (PK).MethodsThe inclusion criteria for this prospective, randomized, clinical study were as follows: (1) surgeries performed by one surgeon; (2) primary central PK; (3) keratoconus (KC) or Fuchs’ dystrophy (FUCHS); (4) no previous intraocular surgery; (5) graft oversize, 0.1 mm; and (6) 16-bite double-running suture. In 68 eyes of 68 patients (mean age: 53.3 ± 19.8 years), PK was performed using either 193-nm MEL70 excimer laser (“EXCIMER”: 17 KC, 18 FUCHS) or 60-KHz femtosecond laser (“FEMTO”: 17 KC, 16 FUCHS) trephination. Specular microscopy (EM 3000) and pachymetry (EM 3000; Pentacam HR; Casia SS-1000) were performed before removing the first suture (11.4 ± 1.9 months) and after removing the second suture (22.6 ± 3.8 months), but before any additional ophthalmic surgery.ResultsECD did not differ significantly (P ≥ 0.436) between EXCIMER and FEMTO either with “all-sutures-in” (1887 ± 409 vs. 1886 ± 438) or with “all-sutures-out” (1703 ± 379 vs. 1737 ± 362). Central corneal thickness and corneal thickness at the thinnest point of the cornea did not differ significantly between EXCIMER and FEMTO either with all-sutures-in (P ≥ 0.096 and P ≥ 0.653) or with all-sutures-out (P ≥ 0.636 and P ≥ 0.717).ConclusionsEXCIMER and FEMTO trephinations from the epithelial side seem to have no disadvantages regarding endothelial cell loss after PK, and both surgical procedures are safe for the endothelium. A larger sample size and longer follow-up are needed to evaluate the long-term impact of EXCIMER and FEMTO trephinations on ECD.

The 308-nm excimer laser stimulates melanogenesis via the wnt/β-Catenin signaling pathway in B16 cells

Background: The mechanism of the 308-nm excimer laser in vitiligo treatment has not yet been adequately studied. In this study, we explored the role of the 308-nm excimer laser in treatment of vitiligo and the molecular mechanisms underlying melanin biosynthesis in melanocytes after 308-nm excimer laser radiation.Materials and methods: The B16 cells were irradiated at doses of 0 mJ/cm2, 100 mJ/cm2, 300 mJ/cm2 and 600 mJ/cm2 using a 308-nm excimer laser and then cultured for an additional 24, 48 or 72 hours. Melanogenesis and tyrosinase activity in cells were measured by biochemical methods. The expression of tyrosinase, MITF, Wnt3α and β-catenin was analyzed by Western blotting.Results: Cell irradiation with the 308-nm excimer laser not only significantly elevated the melanin content (p < .01) but also stimulated the activity of tyrosinase (p < .01). The expressions of tyrosinase and MITF were also significantly increased in cells after 308-nm excimer laser irradiation. We also defined the signaling pathway by which the 308-nm excimer laser stimulates melanin biosynthesis. Increased Wnt3α and β-catenin expression was observed by Western blot analysis.Conclusion: Activation of the Wnt/β-catenin pathway likely led to the activation of MITF and tyrosinase transcription, as well as, the subsequent induction of melanin synthesis.

The effectiveness of topical therapy combined with 308-nm excimer laser on vitiligo compared to excimer laser monotherapy in pediatric patients.

We evaluated the efficiency of using a 308-nm excimer laser with either tacrolimus, pimecrolimus, or halometasone for the treatment of childhood vitiligo. Patients who received combined treatments had significantly higher rates of repigmentation in comparison with individuals who underwent excimer laser alone therapy. Moreover, patients who received treatment with excimer laser and halometasone had significantly higher rates of repigmentation, even higher than individuals who were treated with tacrolimus combined or pimecrolimus combined. This regimen was more effective on the face, neck, and limbs. We conclude that the use of a combined excimer laser and halometasone cream has a greater therapeutic effect than laser alone.

Numerical Modeling of 193-nm Excimer Laser Ablation on CR-39 Polymer

Laser polymer processing has evolved into an important field of applied and fundamental research. Allyl diglycol carbonate or CR-39 is considered an important polymer for use in optical and medical applications since it is a hard and infusible thermoset plastic that is insoluble in all solvents. The temperature distribution of CR-39 when subjected to irradiation during 193-nm excimer laser ablation was investigated. An effective simulation was developed to reflect the effects of polymer thermal diffusion, laser fluence, beam geometry, and number of pulses. A two-dimensional finite element model was used to predict the temperature distribution and ablation depth in the plastic CR-39 polymer under the 193-nm laser ablation process. The photochemical threshold ablation fluence was 750 mJ/cm2 for a single laser pulse, but dropped to 240 mJ/cm2 for repetitive laser pulses. At higher fluence, thermal effects exhibited a slight contribution to the ablation process. For fluence ≥ 750 mJ/cm2, the ablation depth increased abruptly. It can thus be inferred that the rate of temperature increase with pulse number increased concomitantly with the fluence. Thus, thermal effects are a significant factor in the ablation process.

Laser-induced interfacial state changes enable tuning of the Schottky-barrier height in SiC

We used a 193-nm ArF excimer laser to produce a surface functional layer with a tunable Schottky barrier height (SBH) on the n-type 4H-SiC surface. The SBHs of the laser-modified layer/SiC contact ranged from 0.38 ± 0.05 to 1.82 ± 0.1 eV. We evaluated the I-V characteristics of Schottky barrier diodes (SBDs) and investigated their corresponding nanoscale current transport characteristics across the laser-modified layer/4H-SiC interface. We attributed changes of the interfacial transport properties between Au and SiC to the laser-induced formation of SiOx/Si compounds with oxygen vacancies in the nitrogen-doped (N-doped) defective graphitic structure. Density functional theory calculations suggested that defect oxide in the SiOx/Si decreased the Schottky barrier width and increased the direct electron tunneling current. Furthermore, the Fermi level of the laser-induced N-doped defective graphitic structure shifted towards the conduction band compared with that of pristine graphene, which was also beneficial for reducing the SBH. This study provides a novel understanding of the interfacial interactions of a laser-modified layer on SiC through nanoscale electrical analysis. These findings will be useful for further investigations of SiC-based nano-photoelectric devices.

Direct adhesion contrast patterning on PDMS substrate by ArF excimer laser scanning for on-demand printing of functional layers

Adhesion contrast planography (ACP) is a printing method wherein a difference in adhesion forces between a semi-dried ink layer and a polydimethylsiloxane (PDMS) surface is used to form fine patterns. In the present study, direct laser surface modification of PDMS surfaces by a 193-nm excimer laser aiming at the use as an ACP printing plate was investigated in order to realize on-demand printed electronics. Various processing parameters were investigated systematically, including laser energy, laser pulse repetition frequency, scanning rate, and a thin primer film composed of a silane coupling agent. The results showed that appropriate laser conditions for a subsequent ACP process were found such that a cumulative energy density given at silane coupling agent-mediated PDMS surfaces by laser irradiation was in the range of 8–11 mJ/mm2. Under such conditions, the adhesion force on the treated PDMS surface was changed from 2.3 to 3.8 μN against a silica probing sphere. Complementary atomic force microscopy measurements on the laser-treated and pristine PDMS surfaces showed a gradual increase of the surface stiffness of PDMS, validating the idea that laser irradiation induced a conversion of PDMS into a mineralized SiO2 network. To further test the applicability of the present process, several complicated shapes were also examined.

The effectiveness of combination therapy with 308‐nm excimer laser in vitiligo in Han Chinese People

The effectiveness of combination therapy with 308‐nm excimer laser in vitiligo in Han Chinese People

Efficacy of 308-nm excimer laser versus high-intensity ultraviolet radiation for the treatment of active localized vitiligo

Objective To investigate the efficacy and safety of 308-nm excimer laser compared to high-intensity ultraviolet radiation for the treatment of active localized vitiligo, and to observe changes in skin lesions before and after the treatment by confocal laser scanning microscopy. Methods Sixty patients with 203 skin lesions of active localized vitiligo and were enrolled into this study, and the vitiligo disease activity (VIDA) score of these patients ranged from 2 to 3. We selected more than 3 skin lesions from a same anatomical site of each patient, one of lesions served as a control and the other skin lesions (≥ 2) were randomly treated with 308-nm excimer laser (laser group) or high-intensity ultraviolet radiation (ultraviolet group) . The treatment was conducted twice a week for 25 sessions, and a 3-month follow-up was performed. Results A total of 48 patients with 169 skin lesions completed the trial. The marked response rate was significantly higher in the laser group[66.15% (43/65) ]than in the ultraviolet group[44.64% (25/56) , χ2= 8.28, P < 0.01]. The patients with a VIDA score of 2 showed a significantly higher marked response rate[67.69% (44/65) ]compared with those with a VIDA score of 3[44.64% (25/56) , χ2= 6.80, P < 0.01]. During the 3-month follow-up, no relapse was observed. Confocal laser scanning microscopy showed that the number of inflammatory cells increased at the dermal-epidermal junction of the intra- and extra-marginal lesional skin. After treatment, the number of inflammatory cells markedly decreased and returned to normal level in lesions. Conclusion Both 308-nm excimer laser and high-intensity ultraviolet radiation are effective in the treatment of active localized vitiligo, but the 308-nm excimer laser shows a more rapid onset of action and a better therapeutic effect. Key words: Vitiligo; Lasers, excimer; Ultraviolet therapy; Microscopy, confocal

Generation of 8-oxo-7,8-dihydroguanine in G-Quadruplexes Models of Human Telomere Sequences by One-electron Oxidation.

The mechanistic aspects of one-electron oxidation of G-quadruplexes in the basket (Na+ ions) and hybrid (K+ ions) conformations were investigated by transient absorption laser kinetic spectroscopy and HPLC detection of the 8-oxo-7,8-dihydroguanine (8-oxoG) oxidation product. The photo-induced one-electron abstraction from G-quadruplexes was initiated by sulfate radical anions (SO4 ˙- ) derived from the photolysis of persulfate ions by 308nm excimer laser pulses. In neutral aqueous solutions (pH 7.0), the transient absorbance of neutral guanine radicals, G(-H)˙, is observed following the complete decay of SO4 ˙- radicals (~10μs after the actinic laser flash). In both basket and hybrid conformations, the G(-H)˙ decay is biphasic with one component decaying with a lifetime of ~0.1ms, and the other with a lifetime of 20-30ms. The fast decay component (~0.1ms) in G-quadruplexes is correlated with the formation of 8-oxoG lesions. We propose that in G-quadruplexes, G(-H)˙ radicals retain radical cation character by sharing the N1-proton with the O6 -atom of G in the [G˙+ : G] Hoogsteen base pair; this [G(-H)˙: H+ G G˙+ : G] leads to the hydration of G˙+ radical cation within the millisecond time domain, and is followed by the formation of the 8-oxoG lesions.

Bragg Grating Inscription With Low Pulse Energy in Doped Microstructured Polymer Optical Fibers

We demonstrate that fiber Bragg gratings (FBGs) can be written in a doped polymer optical fiber (POF) in a low ultraviolet (UV) pulse energy regime (60Jpulse) using a 248-nm krypton fluoride excimer laser system. The total energy density per inscription necessary to obtain Bragg gratings is between 493.6 and 3825mJcm 2, depending on the number of pulses and the pulse energy. The impact of the pulse energy on the growth of the Bragg grating is investigated, and it is shown that the 248-nm light induces a positive refractive index change. This article demonstrates that the FBGs can be obtained in the POFs without high pulse energy (mJ level) at 248-nm wavelength, which reduces maintenance costs. Furthermore, we can consider it as a solution to increase the lifetime of the laser system without high energy still allowing fast and efficient production of the FBGs for sensing applications.

LASER ASSEMBLY AND PACKAGING OF A MEMS DEVICE

Integration of 3-D devices, IC or MEMS, often requires a handle wafer which is removed before final packaging of the devices. This process usually uses lapping, chemical etch or high temperature heating to de-bond the handle wafer. A new technique to release a Pyrex handle wafer using laser ablation is presented. Pulsed energy, from a 248nm excimer laser is delivered transparently through the Pyrex handle wafer. This causes delamination of the bonded silicon structures from the handle wafer. This technique offers fast throughput at chip and wafer levels and protects the fragile and delicate active devices from harsh physical, chemicals and potential thermal stresses. We present a method wherein the handle wafer used in 3-D assembly of a MEMS device was released using laser micromachining. A Pyrex handle wafer rigidly supports anisotropically etched, through-silicon wafer, vertical mirrors during thermo-compression bonding to active MEMS parts. After this first thermo-compression bond, the Pyrex handle wafer was lifted off using laser ablation, leaving clearance for additional bond steps, which includes additional components and a package frame. Multiple Au-Au thermo-compression bonds of vertical surfaces onto a single MEMS chip were performed, to assemble and package 3-D MEMS devices.

Utility of dermoscopy for evaluating the therapeutic efficacy of tacrolimus ointment plus 308-nm excimer laser combination therapy in localized vitiligo patients.

The aim of the present study was to assess the function of dermoscopy in evaluating the therapeutic efficacy of tacrolimus ointment plus 308-nm excimer laser combination therapy in patients with localized vitiligo. A total of 147 patients with localized vitiligo (progressive disease, n=92; stable period, n=55) were enrolled and received combination therapy for 12 weeks. The condition of the skin lesions was monitored by dermoscopy and visual observation. At the initial visit, skin lesions were observed in 61 progressive and 19 stable patients. Residual perifollicular pigmentation was more abundant in progressive-stage patients than in stable-stage patients, whereas the presence of perilesional hyperpigmentation was obviously lower in patients with progressive vitiligo. After 12 weeks of combination therapy, marked differences in residual perifollicular pigmentation were identified between the progressive- and stable-stage patients. Dermoscopy and visual observation indicated that the 12-week treatment efficacy in patients with progressive disease was significantly higher than in those with stable disease and that assessment by dermoscopy was superior to visual observation at 8 or 12 weeks of treatment. Binary logistic regression analysis revealed that the disease stage, vitiliginous areas and disease course were risk factors associated with the treatment efficacy of the combination therapy. In conclusion, dermoscopy may be used as an effective means of vitiligo therapy assessment to provide an accurate and scientific evaluation of treatment efficacy for localized vitiligo patients.

A review of monochromatic light devices for the treatment of alopecia areata.

There are many laser technologies that are being tested that claim to support hair regrowth for patients with alopecia areata (AA). In this paper, we will determine whether the body of evidence supports the use of devices using monochromatic light sources to treat AA. Articles were gathered from PubMed, Embase, and the Cochrane database using these keywords: lasers, excimer laser, low-level laser therapy (LLLT), low-level light therapy, alopecia, alopecia areata, and hair loss with a category modifier of English. Ten clinical trials and seven case reports/abstracts were assessed. Eight clinical trials and two case reports demonstrated hair regrowth with the 308-nm excimer laser/light in men, women, and children. One case report demonstrated hair regrowth with the ALBA 355® laser. One clinical trial and two case reports demonstrated hair regrowth with LLLT. While two case reports demonstrated hair regrowth with fractional laser therapy, one clinical trial showed no improvement. The 308-nm excimer laser is a safe and effective treatment for men, women, and children with refractory AA of the scalp and beard. Larger, double-blinded clinical trials should be conducted to compare excimer laser therapy to standard treatments. More data is needed to determine the efficacy of LLLT and fractional laser therapy in the treatment of AA.

Comparison of cyclic and continuous 308-nm excimer laser treatments for vitiligo: A randomized controlled noninferiority trial

Comparison of cyclic and continuous 308-nm excimer laser treatments for vitiligo: A randomized controlled noninferiority trial

Treatment of oral lichen planus using 308-nm excimer laser

Oral lichen planus (OLP) is a chronic inflammatory disease, has prolonged courses, repeated attacks and resistance to treatment. The traditional narrow spectrum UVB treatment has an established efficacy on skin lichen planus, and high safety. However, most of ultraviolet phototherapy devices have a huge volume, thereby cannot be used in the treatment of OLP. Lymphocytic infiltration is evident in the lesions of lichen planus, and the direct irradiation of 308-nm excimer laser can induce apoptosis of the T lymphocytes in skin lesions, thereby has a unique therapeutic effect on the diseases involving T lymphocytes. This study aims to investigate the efficacy of 308-nm excimer laser in the treatment of OLP. A total of six OLP patients were enrolled into this study, and further pathological diagnosis was conducted, then 308-nm excimer laser was used in the treatment. The efficacy of 308-nm excimer laser in the treatment of OLP was satisfactory. The clinical symptoms of five patients were significantly improved. In two patients, the erosion surface based on congestion and the surrounding white spots completely disappeared, and clinical recovery was achieved. Three patients achieved partial remission, that is, the erosion surface healed, congestion and white spot area shrunk by more than 1/2 of the primary skin lesions. In the remaining one patient, the erosion surface had not completely healed after treatment, and congestion and white spot area shrunk by less than 1/2 of the primary skin lesions. Only one patients had developed mild pain during the treatment, and this symptom alleviated by itself. The 308-nm excimer laser therapy can serve as a safe and effective treatment for OLP.

Embedded Trench Redistribution Layers at 2– $5~\mu \text{m}$ Width and Space by Excimer Laser Ablation and Surface Planer Processes for 20– $40~\mu \text{m}$ I/O Pitch Interposers

This paper reports on one of the first demonstrations of the formation and metallization of 2–5- $\mu \text{m}$ lines and spaces by an embedded trench method in two dry-film polymer dielectrics, Ajinomoto build-up film and preimidized polyimide, without using chemical mechanical planarization. The trenches and vias in 8–15- $\mu \text{m}$ -thick dry-film dielectrics were formed by 308-nm excimer laser ablation, followed by the metallization of the trenches and vias by copper electrodeposition. A low-cost planarization process was used to remove the copper overburden with a surface planer tool. Using an optimized set of materials and processes, multilayer redistribution layers with 2– $5~\mu \text{m}$ trenches and vias were successfully demonstrated. Although thin film processes on silicon wafers have been able to achieve 40- $\mu \text{m}$ I/O pitch for interposers, the materials and processes integrated in this paper are scalable to large panel fabrication at much higher throughput, for interposers and high-density fan-out packaging at lower cost and higher performance than silicon interposers.

A novel multidose tip and minimal blistering dose protocol for psoriasis with the 308-nm excimer laser

A novel multidose tip and minimal blistering dose protocol for psoriasis with the 308-nm excimer laser

Luminescence of α-quartz crystal and silica glass under excitation of excimer lasers ArF (193 nm), KrF (248 nm)

Luminescence of crystalline α-quartz and silica glass was studied under focused laser excitation. It was found that in crystalline α-quartz the luminescence of self-trapped exciton (STE) is excited in two-photon regime with ArF (193nm) excimer laser. In the case of KrF (248nm) laser excitation mainly luminescence related to near surface area is seen even without laser beam focusing. The near surface luminescence has an emission band similar to that of STE in bulk. Temperature quenching is also similar, therefore this luminescence is attributed to STE created in the area of surface. Luminescence decay kinetic of surface STE is longer than bulk STE decay (tens of ms compared to 1ms at 80K). Electron or/and hole self-trapping near the surface is assumed. Their recombination could provide longer duration of surface STE luminescence. Similar surface luminescence was not excited with ArF (193nm) excimer laser. The nature of absorption for laser 248nm photons at surface is not yet clear.Luminescence of silica glass of III type excited with focused beam of KrF (248nm) laser resembles that of previously studied luminescence of STE in silica.

Al2O3−BaTiO3 nanolaminates fabricated by multistationary target pulsed laser deposition with in situ ellipsometry

Layered oxide materials having alternating repeated layer thicknesses of 10 nm or less are difficult to make, especially with sharp interfaces. Nanostructured thin films having repeated layers of two different oxide materials were obtained by using pulsed laser deposition and two independent stationary targets consisting of Al 2 O 3 and BaTiO 3 . Desired thicknesses were achieved by using a specific number of pulses from a 248-nm KrF excimer laser, at an energy of 450 mJ / pulse , a galvanometer mirror system, and a background pressure of oxygen. Trends in material properties were identified by systematically varying the number of pulses for multiple nanostructured thin films and comparing the resulting properties measured using in-situ spectroscopic ellipsometry and ex-situ capacitance measurements, including relative permittivity and loss. Four films were deposited with a goal of having 0.25-, 1-, 4-, and 10-nm thick layers, and each ∼ 220 nm thick. Ellipsometry data were modeled in situ to calculate thickness, n and k . A representative transmission electron microscopy measurement was also collected for the 10-nm sample with corresponding x-ray photoelectron spectroscopy and energy disperive x-ray spectroscopy. Ellipsometry and capacitance measurements were all performed on each of the samples, with one sample having calculated impedance greater than 30 GOhm at 0.001 Hz.