Q-switched Neodymium-doped Yttrium Aluminum Garnet Research Articles

Highly efficient electro-optically Q-switched 473 nm blue laser

An external frequency doubling electro-optically Q-switched neodymium-doped yttrium aluminum garnet (Nd:YAG) 473 nm blue laser was demonstrated. With absorbed pump energy of 48 mJ at 100 Hz repetition rate, about 2 mJ of 473 nm blue laser pulse energy was achieved by cascade frequency doubling. The second harmonic conversion efficiency was 64.5%, and overall optical-optical efficiency was 4.2%, respectively. The blue laser pulse width was less than 10 ns, and beam quality factor was less than 2.4.

Investigation of supercontinuum generated in the cladding of highly nonlinear photonic crystal fiber

We present an experimental and numerical investigation of supercontinuum generation in polarization-maintaining highly nonlinear photonic crystal fiber using subnanosecond pulses of a passively Q-switched neodymium-doped yttrium aluminum garnet microlaser. For analysis of temporal and spectral characteristics, we performed spectrogram measurements using a streak camera. Supercontinuum spectrograms revealed the presence of cladding modes in our photonic crystal fiber and showed that part of the supercontinuum light was actually generated in the cladding modes. Moreover, numerical simulations indicated that distinct cladding modes can exhibit different dispersion, which adds more complexity to supercontinuum generation processes.

Q-switched 1064-nm dymium-doped yttrium aluminum garnet laser irradiation induces skin collagen synthesis by stimulating MAPKs pathway.

The 1064-nm Q-switched neodymium-doped yttrium aluminum garnet (Nd:YAG) laser is widely used in clinical practice. However, the effects of 1064-nm Q-switched Nd:YAG laser on skin collagen generation have not been fully elucidated. The objectives of the present study were to investigate whether the 1064-nm Q-switched Nd:YAG laser can be used for non-ablative rejuvenation and to explore the possible mechanism underlying the effects. Six-week-old SKH-1 hairless mice were irradiated by the 1064-nm Nd:YAG laser at fluences of 0, 0.5, 1, 1.5, and 2J/cm2, respectively. The contents of hydroxyproline and hydration were detected after laser irradiation. Moreover, hematoxylin-eosin (HE) staining was preformed to evaluate the dermal thickness. Immunofluorescence was used to detect the expressions of MMP-2 and TIMP-1 in the skin after laser irradiation. Furthermore, qRT-PCR was performed to determine the expressions of TGF-β1 and Smad3. In addition, the expressions of ERK1/2, p-ERK1/2, p38, p-p38, JNK, ERK5, and collagen were evaluated by Western blotting. The results indicated that the levels of hydroxyproline, hydration, and collagen were markedly increased; both the thickness of dermal was enhanced after low dose of laser treatment. Moreover, the expression of TIMP-1 was significantly increased, whereas the expression of MMP-2 was remarkably decreased after laser irradiation. Meanwhile, TGF-β1, Smad3, p-ERK1/2, p-P38, and JNK productions were significantly enhanced in irradiated group compared with the ones non-irradiated. Nevertheless, no significant changes were observed in the expression of ERK5 after irradiation. In summary, our study demonstrated that Q-switched 1064-nm Nd:YAG laser can induce collagen generation, at least in part, through activating TGF-β1/Smad3/MAPK signaling pathway.

Low-fluence Q-switched Nd:YAG laser for the treatment of melasma in Asian patients.

Melasma is a common acquired facial pigmentary disorder that is resistant to various modalities of treatment. Recently, the low-fluence 1064-nm Q-switched neodymium-doped yttrium aluminum garnet laser (QSNY) has emerged as the new gold standard of melasma treatment in Asia. To evaluate the efficacy and safety of low-fluence 1064-nm QSNY in Asian patients with melasma. Data of patients with melasma treated with low-fluence QSNY in the department of dermatology at the Korea University Anam Hospital were reviewed retrospectively. A 1064-nm QSNY with 8mm spot size and fluence of 1.2-2.0J/cm2 at 10Hz was used. The results were evaluated using the modified Melasma Area and Severity Index (mMASI) score and the physician's global assessment (PGA). A total of 40 Korean patients with Fitzpatrick skin type III to IV were included. Patients were treated for a median of 10 sessions at a median of 1-week intervals. The mean mMASI score decreased by 54.23% from a baseline of 3.19±2.64 to 1.46±1.06 after treatment. On PGA, 1 out of 40 patients (2.5%) showed excellent improvement, 14 (35%) good, 15 (37.5%) fair, 6 (15%) poor, and 4 (10%) no improvement. However, two patients showed mottled hypopigmentation and rebound hyperpigmentation. Low-fluence 1064-nm QSNY appears to be a safe and effective treatment for Asian patients with melasma.

High-fluence 1064-nm Q-Switched Nd:YAG laser: Safe and effective treatment of café-au-lait macules in Asian patients.

Café-au-lait macules (CALMs) are benign cutaneous hyperpigmentary disorders. Usually, laser therapies for cosmetic concerns result in more severe side effects in the people of Asian descent than that of Caucasians. Unfortunately, there is no gold standard for the laser treatment of CALMs in skin of people of Asian descent. To investigate the efficacy and safety of a high-fluence 1064-nm Q-switched neodymium-doped yttrium aluminum garnet (Nd:YAG) laser treatment of CALMs in Asian patients. The medical records of 35 Korean patients (age range: 1 to 40years old, mean age: 18.5years) diagnosed with isolated CALMs were reviewed retrospectively. The patients were treated with a 1064-nm Q-switched Nd:YAG laser. The parameters were a spot size of 7mm, a fluence of 2.2-2.4J/cm2 with a slow single sliding-stacking pass, and a pulse rate of 10Hz with a 1-week interval for 20-50 sessions. At the week of the final treatment, all treated CALMs showed considerable pigmentation removal without any permanent side effects, such as scaring, mottled hypopigmentation and postinflammatory hyperpigmentation (PIH). All treated CALMs showed more than 50% clinical improvement. No recurrence was observed in any of the patients after 12months of follow-up. A high-fluence 1064-nm Q-switched Nd:YAG laser treatment of CALMs in Asian patients is a safe and effective method without side effects and recurrence.

A Case of Punctate Leukoderma after 1,064 nm Q-Switched Nd:YAG Laser

Punctate leukoderma is characterized of the destruction of melanocytes after chemical of physical damage. In addition, the term is broadly used to describe hypopigmented lesions induced in vitiligo patients after psolaren administration with ultraviolet A and in psoriasis patients with repetitive ultraviolet B phototherapy. The Q-switched neodymium-doped yttrium aluminum garnet (Nd:YAG) laser in treating melasma is frequently reported to be associated with the cause. A 44-year-old woman presented to the department with numerous confetti-like hypopigmented macules on both cheeks for over a year. Weekly treatment of 1,064 nm Q-switched Nd:YAG laser (2.0–3.4 J, 8 mm spot-size) therapy at a non-dermatologic clinic had induced both hyperpigmentation and hypopigmentation lesions. Biopsy performed at both hyperpigmented and hypopigmented lesions revealed variable melanin pigmentation with segmental loss and infiltration of pigment incontinence. The patient was diagnosed with punctate leukoderma and was directed for narrow-band ultraviolet B phototherapy. Herein, we report a case of punctate leukoderma after inadvertent use of 1,064 nm Q-switched Nd:YAG laser. Key words: Masson-Fontana; Punctate leukoderma; Q-switched Nd:YAG

Enhancement of Laser-Induced Breakdown Spectroscopic Signals in a Liquid Jet with Glow Discharge.

In this work, emission signals of laser-induced breakdown (LIBS) plasma of a flowing liquid jet in the absence and presence of an air-supported glow discharge have been investigated. In combination with a needle-to-needle glow discharge, a Q-switched neodymium-doped yttrium aluminum garnet (Nd:YAG) laser (1064 nm, 5 ns) with power density ∼1010 W/cm2 was used to generate a plasma from a liquid jet. Emission lines of Mg, Ca, Al, Li, Na, and K all showed significant enhancements in the presence of the glow discharge. Lower continuum background was also observed. Mechanisms of the line emission enhancement and continuum radiation reduction were discussed.

Treatment of Café-au-lait Macules Using a Q-switched Laser Followed by Serial Fractional Thulium Laser Treatments

Café-au-lait macules are a benign cutaneous pigmentary disorder with variable responses to laser treatment. We treated a 21-year-old female with recurred café-au-lait macules on the thigh using a combination of frequency-doubled Q-switched neodymium-doped yttrium aluminum garnet laser followed by 10 sessions of fractional laser, via a novel 1,927 nm fractional thulium laser. At the 11-month follow-up after the last treatment, no foci of re-pigmentation were found. We suggest that fractional thulium laser resurfacing, combined with conventional Q-switched laser treatment, can be used as a safe and effective adjuvant therapy in patients with treatment-resistant café-au-lait macules.

Treatment of xanthelasma palpebrarum with a 1064-nm, Q-switched Nd:YAG laser

Xanthelasma palpebrarum is the most common cutaneous xanthoma characterized by soft, yellow papules or plaques that arise on the periorbital skin. As these lesions can be cosmetically disfiguring, many patients seek medical help to remove these lesions. To determine the effectiveness and minimum number of treatment sessions with a 1064-nm, Q-switched neodymium-doped yttrium aluminum garnet (Nd:YAG) laser for the treatment of xanthelasma. A retrospective review of patients with xanthelasma consecutively treated with Q-switched Nd:YAG laser was conducted. Forty-six patients with 103 lesions were identified from January 2012 through August 2015. Photographs taken of patients immediately before treatment and 4-8weeks after treatment were independently evaluated by 2 dermatologists. After a single treatment session, 93.2% of lesions had some degree of clearance. All lesions had excellent-to-complete clearance after at least 4 treatment sessions. Patients usually required 4 treatment sessions for optimal results. This was a retrospective study. Treatment parameters varied, follow-up periods were not uniform, and response was not assessed with a validated scale. The Q-switched Nd:YAG laser is effective and well tolerated in the treatment of xanthelasma in our study population.

Melanogenesis inhibition in mice using a low-fluence 1064-nm Q-switched neodymium-doped yttrium aluminum garnet laser: a pilot study.

A low-fluence 1064-nm Q-switched neodymium-doped yttrium aluminum garnet laser, or laser toning, has yielded favorable outcomes in various benign pigmented disorders. However, the exact mechanism of action of laser toning has not been fully elucidated. We sought to determine the inhibitory effect of laser toning on melanogenesis and to assess how laser passes influence the outcomes. To produce perceptible pigmentation, nine HRM-2 melanin-possessing hairless mice were treated with ultraviolet (UV) B radiation on the dorsal skin. This was followed by zero, two, four, or six passes of laser toning twice in 2weeks on each designated quadrant. The spectrophotometric values and pigmentation-related protein expressions were measured. Pigment changes were found in the mice skin using the Fontana-Masson stain for histopathological analysis. Four- and six-pass laser toning significantly improved the lightness compared to that in the unirradiated control (p<0.002). The Fontana-Masson stain showed that melanin was considerably decreased in laser-irradiated skin. As the number of laser passes increased, the expression of tyrosinase decreased (p<0.008). The following parameters also decreased in proportion to the number of laser passes: MITF, TRP-1, TRP-2, p-ERK, and p-Akt. In contrast, TGF-β increased in proportion to the number of laser passes. However, the changes in these six proteins were not statistically significant. Our study demonstrates that laser toning improves skin pigmentation with increased number of passes in a dose-dependent manner. This effect is mediated by tyrosinase inhibition.

Impact of laser pulse duration on the reduction of intraocular pressure during selective laser trabeculoplasty.

To evaluate the efficacy of selective laser trabeculoplasty (SLT) to lower intraocular pressure (IOP) in patients with primary open-angle glaucoma (POAG), normal tension glaucoma (NTG) or ocular hypertension (OHT), when performed with laser pulse duration of 1ns compared with standard 3-5ns. Bilateral SLT with a 532nm Q-switched neodymium-doped yttrium aluminium garnet laser was conducted in 30 patients (60 eyes) with POAG (n=5), NTG (n=2) or OHT (n=23). Pulse duration was 1ns in the right eye (30 eyes; cases) and 3-5ns in all left eyes (controls). Main outcome measures were IOP at 1h, 1day, 8weeks and 6months, and the rate of adverse ocular tissue reactions in all eyes. Mean 1ns and 3-5ns SLT IOPs were 24.1 and 24.3mmHg, respectively, at baseline. No statistically significant difference in mean 1ns and 3-5ns SLT IOP was observed at 1h (P=0.761), 1day (P=0.758), 8weeks (P=0.352) and 6months postoperatively (P=0.879). No significant difference in postoperative anterior chamber inflammation was observed between the eyes (P=0.529). Treatment with both laser pulse durations resulted in minor ultrastructural changes in the drainage angle. SLT performed with a 1ns laser pulse duration does not appear to be inferior to SLT performed with the standard 3-5ns duration at lowering IOP in treatment-naïve patients with POAG, NTG or OHT.

A review of melasma treatment focusing on laser and light devices.

Melasma is a pigmentary disorder of unclear etiology with numerous treatment options and high recurrence rates. Laser and light therapies may be utilized cautiously as second- or third-line options for recalcitrant melasma, but low-energy settings are preferred due to the risk of postinflammatory hyperpigmentation and melasma stimulation. Commonly used lasers include the low-fluence 1064-nm Q-switched neodymium-doped yttrium aluminum garnet laser, nonablative fractionated lasers, and intense pulsed light. Strict sun protection, concomitant use of bleaching agents, and maintenance treatments are necessary. A variety of other treatments that may also help to improve results are now being more widely adopted, including oral tranexamic acid, pulsed dye laser, antioxidants, and laser-assisted drug delivery.

Guidelines for removing permanent makeup

&lt;p&gt;Permanent makeup (PMU) is a frequently implemented cosmetic procedure performed by beauticians. From a technical point, PMU is considered a facial tattoo. Failed procedures or a change of mind can lead to the desire for removal. The purpose of this retrospective evaluation of patients who came to the clinic with the desire to remove PMU between 2011 and 2015 was to explore the problems, side effects, and results in order to define treatment guidelines for other doctors. We evaluated 87 individual cases in total. In treatable cases, i.e. 52 out of the 87 cases, laser treatments were performed using a nanosecond Q-switched neodymium-doped yttrium aluminium garnet (Nd:YAG) laser. It takes between 1-12 treatments to remove the PMU. In three cases, the colour of the PMU could not be removed by laser and remained after the treatment. In two cases, laser treatment had to be terminated due to colour changes towards the green-blue spectrum. Before PMU removal, laser test shots are urgently recommended as unforeseeable colour changes can cause severe aesthetically unpleasant results. Covered up PMU (skin colour) is particularly susceptible to changes in colour. Heat-induced shrinking of the eye area can cause an ectropium. Surgical solutions also have to be taken into consideration. The use of proper eye protection with intraocular eye shields is mandatory. This article is an attempt to set up some guidelines for the treatment of PMU removal.&lt;/p&gt;

Clinical and Histopathologic Assessment of Facial Melasma After Low-Fluence Q-Switched Neodymium-Doped Yttrium Aluminium Garnet Laser.

Melasma is a frequent and difficult to treat skin disorder. Results of laser therapy are inconsistent. To determine the safety and efficacy of low-fluence Q-switched neodymium-doped yttrium aluminum garnet (QS Nd:YAG) laser for melasma treatment and assess recurrence rates and histopathologic findings before and after treatment. Twenty patients were treated with 10 weekly sessions of low-fluence 1064-nm QS Nd:YAG laser at 1-week intervals. The modified Melasma Area and Severity Index (mMASI) score was evaluated at baseline; 1 week; and 1, 3, and 6 months after treatment. Epidermal melanin quantification was performed on 10 biopsy samples and compared before and after treatment. All patients showed improvement by mMASI scores, range (21%-75%) compared with that at baseline. No permanent side effects occurred. The recurrence rate was 81%. By histopathology, a slight, nonsignificant (p = .305) decrease in melanin deposition was seen in all layers of the epidermis 1 week after the laser treatments ended. The results confirm the safety and effectiveness of low-fluence QS Nd:YAG laser for treating melasma; however, the high recurrence suggests poor long-term results when the laser is used as a monotherapy.

A Retrospective Study on the Characteristics of Treating Nevus of Ota by 1064-nm Q-switched Neodymium-doped Yttrium Aluminum Garnet Laser.

Background:The Q-switched neodymium-doped yttrium aluminum garnet (QS Nd:YAG) laser has a significant effect in treating nevus of Ota, but there is lack of a retrospective study about the characteristics of efficacy.Aims and Objectives:To retrospectively analyze the correlation between the clinical characteristics and efficacy, complications, recurrence of QS Nd:YAG laser in treating nevus of Ota.Materials and Methods:One hundred and seventy-one Chinese patients (144 female, 27 male) of nevus of Ota were treated with the 1064-nm QS Nd:YAG laser. All cases were treated with fluencies of 4–8 J/cm2 and a spot size of 2–4 mm. Clinical photographs were taken before every treatment and patients were followed up by their clinicians.Results:One hundred and forty-five patients (84.8%) acquired more than 75% improvement with an average of 4.6 sessions. The treatment effect has no significant correlation with sex (P > 0.05). The blue-black and brown lesions improved more than the light-brown (P < 0.05). Hyperpigmentation affected two (1.2%) of the patients and hypopigmentation affected one patient (0.6%). No other adverse effect was observed. Recurrence was seen in two patients (1.2%).Conclusion:The 1064-nm QS Nd:YAG laser is effective with rare complications and recurrence in the treatment of nevus of Ota. The efficacy correlated with lesion color, which is meaningful to estimate the prognosis.

Combined vitamin C sonophoresis and neodymium-doped yttrium aluminum garnet (NdYAG) laser for facial hyperpigmentation: An outcome observation study in Asian patients.

The neodymium-doped yttrium aluminum garnet (NdYAG) laser therapy has been a popular technique for facial rejuvenation but certain adverse effects like post-inflammatory hyperpigmentation are issues of concern to Asian patients. To assess the outcome following combined treatment with vitamin C sonophoresis and NdYAG laser, in selected cases of facial hyperpigmentation. Twenty three women with dyschromia or melasma who had undergone five sessions of Q-switched NdYAG laser therapy followed by transdermal delivery of vitamin C via sonophoresis were selected after a retrospective review of case records. The objective and subjective clinical outcomes and the side effects, including erythema, scaling, pruritus, dryness and post-inflammatory hyperpigmentation were evaluated. In both objective or subjective outcomes, 91.3% (21/23) of the patients showed an excellent or better outcome, while 8.7% (2/23) showed no change. A majority of the patients (73.9%, 17/23) experienced no post-inflammatory hyperpigmentation or had slight post-inflammatory hyperpigmentation which quickly resolved within 1 week. Only one (4.3%) patient had extreme post-inflammatory hyperpigmentation which lasted for over a month. This was a retrospective study without a control group; a comparative study with a control group (patients treated with the laser alone, without vitamin C sonopheresis) is needed to determine the difference in the outcome. The use of vitamin C sonophoresis along with NdYAG laser may reduce the incidence of adverse effects in Asian patients. Patients experienced obvious improvement in hyperpigmentation and had lower chances of experiencing extreme or severe post-inflammatory hyperpigmentation.

Study of the grinding performance of laser-trued and dressed bronzed-bonded diamond grinding wheels

A triangulation-based closed-loop control system with high-precision couple charged device (CCD) laser displacement sensors was used to true and dress a bronze-bonded diamond grinding wheel online with an acousto-optic Q-switched neodymium-doped yttrium aluminum garnet (Nd:YAG) laser. The microscopic surface topography of the trued and dressed grinding wheel was observed using a three-dimensional (3D) microscope with an ultra-large depth of field. The results showed that the diamond abrasives were uniformly distributed on and protruded from the surface of the bronze bond, which indicated good topography of the grinding wheel. Orthogonal grinding experiments were conducted on the laser-dressed bronze-bonded diamond wheel, and three quality evaluation indices, the grinding ratio, the grinding force ratio, and the workpiece surface roughness, were measured and calculated. The results of the grinding experiment were systematically analyzed using a gray relational analysis. Under the experimental conditions of this study, the dominant factor that affected the quality evaluation indices was the laser spot diameter, followed by the pulse duration. The laser power was a secondary factor.

Methyl Radical Imaging in Methane-Air Flames Using Laser Photofragmentation-Induced Fluorescence.

Imaging detection of methyl radicals has been performed in laminar premixed methane-air flames at atmospheric pressure. A nanosecond Q-switched neodymium-doped yttrium aluminum garnet (Nd : YAG) laser was employed to provide the fifth-harmonic-generated 212.8 nm laser beam. The intense ultraviolet (UV) laser pulse was sent through the flame front to photodissociate the methyl (CH3) radicals in the reaction zone of the flames stabilized on a piloted jet flame burner. The emission spectra from the photodissociated fragments were collected using an imaging spectrometer with the flame-front structure spatially resolved. Combining the spatial and spectral information, we recognized that the emission from the (A-X) methine (CH) transitions located at 431 nm was generated from the CH3 photolysis and could be used to visualize the distribution of CH3 radicals. With proper filtering, the high-power UV laser (around 15 mJ/pulse) provided by the compact Nd : YAG laser makes it possible to visualize CH3 distribution naturally generated in the reaction zone of laminar methane-air premixed flames.

A low-fluence 1064-nm Q-switched neodymium-doped yttrium aluminium garnet laser for the treatment of café-au-lait macules

Café-au-lait macules (CALMs) are a common pigmentary disorder. Although a variety of laser modalities have been used to treat CALMs, their efficacies vary and dyspigmentation may develop. We evaluated the clinical efficacy and safety of a low-fluence 1064-nm Q-switched neodymium-doped yttrium aluminium garnet (Nd:YAG) laser for the treatment of CALMs. In a preliminary investigation, 6 patients underwent a split-lesion comparative study with 532- and 1064-nm Q-switched Nd:YAG laser treatment. In total, 32 patients with 39 CALMs were enrolled in a subsequent prospective trial to evaluate the treatment with a low-fluence 1064-nm Q-switched Nd:YAG laser. In the preliminary study, the 1064-nm treatment group had a more favorable response and a shorter recovery time. In a subsequent prospective trial of a 1064-nm laser, 74.4% of the lesions showed a clinical response with clearance of ≥50.0%. The treatment regimen was well tolerated; 15.4% of patients experienced adverse events. The study participants were followed for 6 months, and there were no relevant treatment controls in the prospective trial group. Low-fluence 1064-nm Q-switched Nd:YAG laser therapy afforded good clinical improvement for treating CALMs.

Effect of Hydroquinone Plus Neodymium-Doped Yttrium Aluminium Garnet Laser With and Without CO2 Fractional Laser on Resistant Dermal Melasma

Background: The use of different types of lasers in the treatment of refractory melasma is still controversial. The present study was designed according to previous studies and used a combination of treatments. Objectives: The purpose of this study was to compare Q-switched (QS) neodymium-doped yttrium aluminium garnet (Nd: YAG) laser and hydroquinone with or without CO2 fractional laser in refractory melasma. Patients and Methods: Seventeen patients with refractory melasma, in a split-face randomized trial, received topical hydroquinone and Nd: YAG laser treatment on one half of their face and topical hydroquinone, Nd: YAG laser and CO2 fractional laser on the other half of their face. The patients were then assessed by Melasma area and severity index (MASI) over 12 weeks in three treatment sessions with an interval of three to four weeks. Results: Seventeen patients with melasma (14 females and three males) with mean (± SD) age of 38.47 (± 6.29) years (range 29 - 53) were included in this study. The only side effect for the Nd: YAG treatment was erythema observed in two cases (11.8%). The mean MASI scores decreased significantly after six weeks for both therapies. Also, a significant reduction was observed in the mean MASI scores from week six till the end of the study. Controlling for the effect of “MASI score at baseline”, the mean MASI score was significantly lower on the side treated with Nd:YAG + CO2 fractional laser in comparison with the Nd: YAG laser. Conclusions: Our study showed that the triple therapy of ND: YAG and ND: YAG + CO2 fractional and hydroquinone cream had high efficiency and low morbidity compared to twofold treatment with ND: YAG and ND: YAG + CO2 fractional.