Q-switched Alexandrite Laser Research Articles

Tarnish tattoos - localised cutaneous argyria from sterling silver in fresh piercings: a case series.

Tarnish tattoo is a form of localised cutaneous argyria resulting from the deposition of silver into the skin following exposure to silver jewellery in fresh piercings. This report presents the clinical presentation, diagnosis, and management of 4 female patients with tarnish tattoos on the nose and ear from wearing silver jewellery. All four patients wore silver studs or rings immediately following the piercing. Two of the four patients underwent treatment with nanosecond Q-switched 1064nm Neodymium: Yttrium Garnet laser (QS Nd: YAG) and Q-switched Alexandrite 755nm lasers with minimal improvement. Tarnish tattoos are an under-recognized side-effect of wearing silver jewellery in fresh piercings. The grey-blue discolouration from tarnish tattoos can be challenging to treat with nanosecond QS lasers.

Drug-Induced Pigmentation: A Review.

Drug-induced pigmentation (DIP) is estimated to account for 20% of all cases of acquired hyperpigmentation. Over 50 agents have been implicated, including antibiotics, antimalarials, antiretrovirals, antipsychotics, prostaglandin analogs, heavy metals, and chemotherapeutic agents. The skin, mucosal surfaces, nails, and hair can all be affected, with the color, distribution, onset, and duration of pigmentation varying between offending agents. Both a thorough physical examination and medication history are necessary to determine the offending agent. In terms of mechanism, DIP occurs most frequently through the accumulation of melanin within the dermis but also by drug accumulation, pigment synthesis, and iron deposition. Photoprotection, including applying a broad-spectrum sunscreen, wearing photoprotective clothing, and seeking shade, plays an important role in the prevention of exacerbation of DIP. Multiple lasers, including the picosecond alexandrite, Q-switched Nd:YAG, Q-switched alexandrite, and Q-switched ruby lasers, have been successful in obtaining clearance of DIP. In this review, we examine the unique characteristics of each of the inciting agents in terms of incidence, clinical presentation, time to onset and resolution, and pathogenesis.

Efficient intra-cavity frequency doubled, diode-pumped, Q-switched alexandrite laser directly emitting in the UV.

We present an intra-cavity frequency doubled Q-switched diode-pumped alexandrite ring-laser directly emitting in the UV at 386 nm. Using LBO as nonlinear crystal, the laser yields a pulse energy up to 3 mJ at 500 Hz with an excellent beam quality of M2 = 1.1. The pulse length is about 920 ns, allowing for very narrow bandwidth in single longitudinal mode operation. The optical-to-optical efficiency for the UV laser is > 9% and almost unchanged compared to the fundamental laser. First injection-seeding experiments show single longitudinal mode operation. The parameters of the laser are suitable for the use as an emitter in a multi-purpose atmospheric Doppler lidar system.

Diode-pumped, Q-switched Alexandrite laser as emitter for general purpose atmospheric Lidar systems

We present design and performance of four prototypes of narrow-bandwidth emitters based on diode-pumped Alexandrite lasers for atmospheric Doppler-Mie, -Rayleigh and -resonance lidar systems. Furthermore, lab results for efficient frequency-doubling into the UV are presented.

High-energy acousto-optic Q-switched alexandrite laser with wavelength tunable fundamental and UV second harmonic generation

We investigate high-energy mJ-class diode-pumped acousto-optic (AO) Q-switched alexandrite lasers with broad tunability at both the fundamental near-IR wavelength range and second harmonic generation (SHG) in the UV wavelength range. An AO Q-switched alexandrite laser with continuous-wave diode-pumping has been operated at up to 10 kHz and producing pulse energy of 700 µJ at repetition rate of 1 kHz. With pulsed double-pass diode-pumping, we demonstrate higher pulse energy of 2.6 mJ. With wavelength tuning, this laser system demonstrated broad fundamental tuning range from 719 to 787 nm with diffraction-limited beam quality (M2 = 1.05). By external cavity second harmonic generation in a Type-I LBO crystal, pulse energy of 0.66 mJ is generated at 375 nm and with UV tuning range from 361 to 391 nm. To our knowledge, this is the first demonstration of AO Q-switched alexandrite laser with broad wavelength tuning in the near-IR and UV wavelength ranges and shows its excellent potential as a pulsed source for future applications.

Exogenous Ochronosis: Characterizing a Rare Disorder in Skin of Color.

Exogenous ochronosis is a rare dyschromia that primarily impacts those with skin of color. It is characterized by blue-black pigmentation and is associated with the long-term application of skin-lightening creams containing hydroquinone. Commonly confused with other dyschromias, the use of skin lightening topicals can cause paradoxical skin darkening in patients with known exogenous ochronosis. This is highly distressing to patients, often worsening the underlying dyschromia and making treatment more difficult. A 10-year retrospective analysis was conducted that revealed 25 patients with exogenous ochronosis. The average patient used a skin lightening cream for 9.2 years, with exogenous ochronosis most commonly arising on the cheeks (68%), forehead (24%), and temples (20%). Furthermore, this study identified that patients with exogenous ochronosis may respond well to treatment with Q-switched Alexandrite laser and microneedling. The incidence of exogenous ochronosis is likely to increase as demographics shift and access to a wide range of over-the-counter topicals becomes more available, both in the United States and worldwide. Therefore, it is imperative to better characterize exogenous ochronosis to identify best treatment practices for all patients.

Skin barrier function and changes of serum inflammatory factor level in hyperpigmentation disorders treated with Nd:YAG laser.

It was to compare the differences in efficacy and safety for the treatment of hyperpigmentation disorders by Q-switched alexandrite (Q-SA) laser and Neodymium-doped Yttrium Aluminium Garnet (Nd:YAG) laser. The clinical data of 86 patients with hyperpigmentation disorders were collected and grouped: in the Q-SA laser and Nd:YAG laser groups according to the treatment methods, with 43 cases in each group. The clinical efficacy, skin barrier function (transdermal water loss (TEWL), stratum corneum water content, pH value, proteoglycan content), degree of pigmentation, serum inflammatory factors (high-sensitivity C-reactive protein (hs-CRP), tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6)), and adverse reaction rate were compared after treatment. Compared with the Q-SA laser group, Nd:YAG laser group had decreased scab formation, healing, and scab shedding time, TEWL, pH value, and proteoglycan content, the increased water content of stratum corneum, decreased pigmentation score and area, and decreased serum levels of hs-CRP, TNF-α, and IL-6 (P<0.05). The total effective rates were 76.74% and 95.35%, and the adverse reaction rates were 30.23% and 6.98%, respectively in the Q-SA laser and Nd:YAG laser groups. Compared with the Q-SA laser group, Nd:YAG laser group had a higher total effective rate and lower incidence rate of adverse reactions (P<0.05). Nd:YAG laser plus rhEGF gel in the treatment of hyperpigmentation disorders can effectively protect the skin barrier function, reduce skin pigmentation, reduce the inflammatory response, and improve the therapeutic effect, with high safety.

LD-Pumped Watt-Level SESAM Passively Q-Switched Alexandrite Laser

Alexandrite lasers are attractive choices for 700-800 nm band, and they are necessary in many applications. A red laser diode (LD) pumped watt-level passively Q-switched Alexandrite laser with a semiconductor saturable absorber mirror (SESAM) is presented. A continuous wave (CW) laser with an average power of 2.5 W was obtained. Customized SESAMs were employed to enable a 749.6-nm pulsed Alexandrite laser with an average power of 0.904 W, a repetition rate of 20.27 kHz, and a pulse energy of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$44.59\mu \text{J}$ </tex-math></inline-formula> , when the pump power was 26.5 W. To the best of our knowledge, this is the highest average power from SESAM passively Q-switched Alexandrite laser, which is one order of magnitude higher than previous reported results.

Efficacy and safety of Q-switched lasers for the treatment of naevus of Ota in children: a retrospective analysis.

To identify factors influencing the efficacy of Q-switched laser in the treatment of naevus of Ota in children and to compare the efficacy, safety, and recurrence rate between 1064nm Q-switched Nd:YAG laser (QSNL) and 755nm Q-switched alexandrite laser (QSAL). We retrospectively analysed 160 children with naevus of Ota who completed QSAL or QSNL laser treatment at our centre. Age at initial treatment (P = 0.004), colour of lesions (P = 0.025), and number of treatments (P = 0.002) were related to efficacy. Compared with patients aged 0-11months at initial treatment, patients who started treatment at 1-3years (OR adj = 0.47), 4-8years (OR adj = 0.20), and 9-12years (OR adj = 0.27) had inferior efficacy. The efficacy of brown-violet (OR adj = 2.67) and blue-violet lesions (OR adj = 2.51) was better than that of brown lesions. Moreover, patients who received 3-4 (OR adj = 2.83) or 5-6 (OR adj = 7.35) treatment sessions showed a better response than those who received 1-2 sessions. Additionally, as the age at initial treatment increased, the rate of complications increased from 2.0 to 14.3%, while the recurrence rate decreased from 8.2 to 0%. In addition, the complication rate increased with an increase in the number of treatments. There were no significant differences in clinical efficacy (P = 0.94), risk of complications (P = 0.752), or recurrence (P = 0.834) between QSAL and QSNL for treating naevus of Ota in children. QSAL and QSNL are equally effective for children's naevus of Ota, with low complications and recurrence rates. Younger age at initial treatment and a greater number of treatments are beneficial for efficacy, whereas brown lesions are a negative factor.

High-performance cavity-dumped Q-switched Alexandrite laser CW diode-pumped in double-pass configuration.

We present a high-performance Alexandrite laser for LIDAR applications with repetition rates up to 20 kHz in cavity-dumped Q-switched operation continuous-wave diode-pumped in the red spectral region. With a double-pass pump configuration, short pulses with 2.8 ns duration at repetition frequencies ranging from 1 kHz to 20 kHz could be demonstrated. At 5 kHz a - to our knowledge - record pulse energy of over 500 µJ could be achieved at 755 nm in TEM00. Furthermore, a stability measurement at an energy of around 350 µJ with 5 kHz showed no degradation over 150 Mega-shots. The influence of the crystal temperature on the laser performance is also investigated, first in continuous-wave and secondly in cavity-dumped Q-switched operation.

Dual-Wavelength Continuous-Wave and Passively Q-Switched Alexandrite Laser at 736.7 nm and 752.8 nm

A dual-wavelength continuous-wave (CW) and passively Q-switched alexandrite laser based on a MoS2 saturable absorber (SA) operating at 736.7 nm and 752.8 nm with a simple and compact 18 mm plano–plano resonator is reported. In the CW mode, the output power is 1014 mW at the linear-polarized pump power of 5.44 W, with a slope efficiency of 28.7%. In the pulsed operation, the narrowest pulse width and the maximal peak power are 154 ns and 10.6 W, respectively. This laser can be used to generate 8.71 THz-wave light based on a suitable nonlinear optical crystal.

LD Pumped Watt-Level Actively Q-switched Alexandrite Laser

LD Pumped Watt-Level Actively Q-switched Alexandrite Laser

Beneficial Effects of Treatment With Low-Fluence 755-nm Q-Switched Alexandrite Laser for Nevus of Ota.

Nevus of Ota is a benign dermal and mucosal melanocytic nevus that can be cured by Q-switched lasers. However, the incidence rate of post-treatment hyperpigmentation in Asian patients remains high. Low-fluence Q-switched Nd:YAG laser (QSNY) has been proved effective in the early treatment of nevus of Ota. Q-switched alexandrite laser (QSAL) was found to achieve a higher successrate and lower complication rate than QSNY. This study aims to evaluate the efficacy and safety of low-fluence 755 nm QSAL in the treatment of nevus of Ota. A total of 81 patients with nevus of Ota were retrospectively evaluated. Among them, 39 went through the high-fluence QSAL (3 mm spot, 5.0-8.0 J/cm2 ) and 42 were treated by low-fluence QSAL (5 mm spot, 2.2-2.8 J/cm2 ). Treatments were given every 6 months three times. Standard photos of the lesions were taken to evaluate the efficacy. All adverse events were noted. The low-fluence QSAL group achieved a significantly higher mean efficacy score than the high-fluence QSAL group after the first treatment (3.62 ± 0.85 vs. 2.9 ± 0.79, P < 0.001) and at the final follow-up visit (4.52 ± 0.63 vs. 4.03 ± 0.96, P < 0.05). Post-inflammation hyperpigmentation rate was significantly lower in the low-fluence QSAL group than in the high-fluence QSAL group (4.8% vs. 25.6%, P < 0.001). No patient reported hyperkeratosis, scarring, bleeding, skin textural change, or recurrence at the final visit in either group. The low-fluence QSAL is more effective and safer than the traditional high-fluence QSAL because of its better clinical outcome and lower complication rate in the treatment of nevus of Ota. Lasers Surg. Med. © 2021 Wiley Periodicals LLC.

Efficacy and safety of 755nm Q-switched Alexandrite Laser for Hori's nevus: a retrospective analysis of 482 Chinese women.

To evaluate the efficacy and safety of 755nm Q-Switched alexandrite laser for Hori's nevus in a large cohort of Chinese women. We retrospectively analyzed the efficacy and safety of 755nm Q-Switched alexandrite laser for Hori's nevus. Reduction in pigment was evaluated using a 4-score method. A total of 482 patients, aged 16 to 52years, were included in this analysis. Patients were treated with 755nm Q-Switched alexandrite laser at fluence levels of 5-8J/cm2 for 2-4 treatment sessions. Following the treatments, 53% of patients showed over 75% reductions in pigment while 50-75% reductions in pigment were observed in 28% of patients. The rest displayed less than 50% improvements. Efficacy was positively correlated with the number of treatment sessions (p < 0.0001). Adverse reactions were temporary, mild erythema, and edema. A small portion of patients (15%) had hyperpigmentation, which disappeared within 2-6months. 755nm Q-Switched alexandrite laser is safe and has moderate benefits for Hori's nevus. Because its efficacy is positively correlated with the number of treatment sessions, increase in treatment sessions possibly could achieve a better outcome.

Assessing the safety of the Q-switched 755-nm alexandrite laser in darker skin: A retrospective study

To the Editor: Q-switched alexandrite laser (QSAL) devices are well-established as a cosmetic treatment modality for a diverse array of pigment abnormalities 1 Hu S. Yang C.S. Chang S.L. Huang Y.L. Lin Y.F. Lee M.C. Efficacy and safety of the picosecond 755-nm alexandrite laser for treatment of dermal pigmentation in Asians-a retrospective study. Lasers Med Sci. 2020; 35: 1377-1383 Crossref PubMed Scopus (12) Google Scholar ; however, studies evaluating adverse effects and modifiable factors, particularly among patients with skin of color, are limited. The increased likelihood of unwanted side effects makes treatment more difficult and nuanced among patients with skin of color. 2 Wang Y. Qian H. Lu Z. Treatment of café au lait macules in Chinese patients with a Q-switched 755-nm alexandrite laser. J Dermatolog Treat. 2012; 23: 431-436 Crossref PubMed Scopus (14) Google Scholar

Use of Reflectance Confocal Microscopy to Predict Treatment Efficacy in Café Au Lait Macules.

Multiple lasers have been used for the treatment of café au lait macules (CALMs) with various results. Objective tools to predict therapeutic efficacy of CALMs treatment is lacking. To determine whether reflectance confocal microscopy (RCM) characteristics correlate with CALMs response to laser treatment. All CAMLs underwent RCM examination of length and density of dermal papillae followed by 3 sessions of Q-switched alexandrite laser (QSAL). A visual analog scale was used to assess clinical treatment efficacy. Forty-three patients were included, 22 had CALMs with irregular borders and 21 with smooth borders. Café au lait macules with irregular border had shorter rete pegs and less papillae (p < .05) on RCM compared with smooth border CAMLs and responded better to QSAL treatment (2.32 vs 1.10). Reflectance confocal microscopy measurement of length and density of papillae were inversely correlated with treatment response. Reflectance confocal microscopy may be a useful tool to predict CALMs response to laser treatment.

Comparing the efficacy and safety of Q-switched and picosecond lasers in the treatment of nevus of Ota: a systematic review and meta-analysis.

Nevus of Ota is cosmetically burdensome and often prompts patients to seek treatment. Lasers are commonly used in removing these lesions; however, no systemic analysis has been conducted to support a gold standard laser. To conduct a meta-analysis of the efficacy and safety of Q-switched Nd:YAG lasers (QSNL), Q-switched ruby lasers (QSRL), Q-switched alexandrite lasers (QSAL), and picosecond alexandrite lasers (PSAL) in removing nevus of Ota. Inclusion criteria were nevus of Ota patients treated with QSNL, QSRL, QSAL, or PSAL and documentation of percent clearance and the rate of at least one adverse event. Articles in English, Chinese, or Japanese were included. The prespecified outcome measures were efficacy (percent clearance) and safety (rates of hyperpigmentation, hypopigmentation, scarring, and recurrence). The review included 57 studies and 13,417 patients. The pooled success rate was 64% for QSNL (95% CI 52-76%), 54% for QSRL (95% CI 39-69%), 58% for QSAL (95% CI 44-72%), and 100% for PSAL (95% CI 98-102%). The pooled adverse event rate was 5% for QSNL (95% CI 4-6%), 14% for QSRL (95% CI 9-19%), 9% for QSAL (95% CI 6-12%), and 44% (95% CI 31-57%) for PSAL. QSNL has the most evidence for effectively and safely treating nevus of Ota. PSAL potentially has a superior efficacy; however, further studies are needed to elucidate its side effect profile when treating nevus of Ota.

755-nm Q-switched alexandrite laser does not markedly benefit Becker's nevus: a retrospective analysis of 59 cases.

755-nm Q-switched alexandrite laser does not markedly benefit Becker's nevus: a retrospective analysis of 59 cases.

Comparison of a picosecond alexandrite laser versus a Q-switched alexandrite laser for the treatment of nevus of Ota: A randomized, split-lesion, controlled trial

Novel picosecond lasers have been available for various pigmentary disorders. However, there are limited data directly comparing picosecond lasers and Q-switched lasers for treatment of nevus of Ota. To compare the efficacy and safety of a picosecond alexandrite laser (PSAL) with a Q-switched alexandrite laser (QSAL) for the treatment of nevus of Ota. Each lesion of 56 enrolled participants was split into 2 parts and randomly assigned to either the PSAL or QSAL treatment arm. Each lesion was treated in up to 6 sessions in 12-week intervals. Efficacy and safety were determined using blinded visual evaluation and self-report at each follow-up visit. The PSAL arm achieved a significantly better clearance (5-point scale, PSAL 4.53 vs QSAL 4.0) with fewer sessions (PSAL 5.26 vs QSAL 5.87) and less severe pain (Visual Analog Scale, PSAL 5.61 vs QSAL 6.40). Patients were more satisfied with PSAL than QSAL (Likert scale, 4.5 vs 4.0). Occurrences of postinflammatory hyperpigmentation (PSAL 26% vs QSAL 34%) and hypopigmentation (PSAL 21% vs QSAL 47%) were also lower in PSAL than QSAL arm. Lack of objective assessments and outcome measures. PSAL demonstrated better clinical results and fewer adverse events than QSAL for the treatment of nevus of Ota.

Diode-pumped Q-switched Alexandrite laser in single longitudinal mode operation with Watt-level output power.

We present significantly improved performance data of a diode-pumped Q-switched Alexandrite laser in single longitudinal mode operation developed as a beam source for resonance lidar systems. The average output power of the laser-operating at the potassium resonance at 770 nm with a linewidth below 10 MHz-could be increased by a factor of five to the Watt-level by means of an optimized resonator design and pump scheme. The pulse energy is 1.7 mJ with a beam quality of M2≤1.1 in both spatial directions at a repetition rate of 500 Hz.