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q switched laser

Dr Swapnil Deepak Shah, Dr Sanjeev Aurangabadkar, Dr Balkrishna Nikam
Lichen planus pigmentosus (LPP) is a cosmetically disfiguring condition. Many treatment options are available which are effective in halting the progression of the disease. The treatment of persistent pigmentation is still a challenge. We describe the use of Q-switched Nd-YAG laser in 13 patients with stable LPP using a standard protocol. Most of our patients showed complete to near-complete resolution of pigment without much complications.
May 16, 2018: Journal of Cosmetic and Laser Therapy: Official Publication of the European Society for Laser Dermatology
Jingjing Liu, Xiaoyue Feng, Xiuwei Fan, Zhen Zhang, Bo Zhang, Jie Liu, Liangbi Su
An Er3+ -doped CaF2 -SrF2 mixed crystal was grown using the temperature gradient technique, and its laser characteristics were studied. In a compact linear cavity, a continuous-wave output power of 712 mW was obtained with the highest slope efficiency of 41.4%. Using a semiconductor saturable absorber mirror, a passive Q-switched mode-locked Er3+ :CaF2 -SrF2 laser emitting at 2729.5 nm was demonstrated for the first time, to the best of our knowledge. The maximum average output power of 125 mW was obtained at an absorbed pump power of 1...
May 15, 2018: Optics Letters
See Yenn Chong, Michael D Todd
Numerous Lamb wave dispersion curve estimation methods have been developed to support damage detection and localization strategies in non-destructive evaluation/structural health monitoring (NDE/SHM) applications. In this paper, the covariance matrix is used to extract features from an ultrasonic wavefield imaging (UWI) scan in order to estimate the phase and group velocities of S0 and A0 modes. A laser ultrasonic interrogation method based on a Q-switched laser scanning system was used to interrogate full-field ultrasonic signals in a 2-mm aluminum plate at five different frequencies...
May 1, 2018: Ultrasonics
Stephen Akihiro Wirya, Neelam A Vashi
Patients with a history of intravenous drug usage (IVDU) often develop pathognomonic linear hyperpigmented dermatoses near injection sites. This drug use-related pigmentation can be very distressing for patients as they persist for life, are very difficult to treat, and remain a constant reminder of prior drug usage. The difficulty of treatment is due to the location of the deposited material and its exogenous nature. This article reports two cases of linear hyperpigmentation due to IVDU successfully treated using the Q-switched Alexandrite laser...
May 8, 2018: Journal of Cosmetic and Laser Therapy: Official Publication of the European Society for Laser Dermatology
Mei-Ching Lee, Ying-Fang Lin, Sindy Hu, Yau-Li Huang, Shyue-Luen Chang, Chun-Yu Cheng, Chun-Shin Chang
To evaluate efficacy and safety of picosecond 755 nm alexandrite laser as compared to 1064 nm QS-Nd:YAG laser for melasma treatment in Asians. Twelve patients received 4 sessions of treatments at 1-month interval in a split-face manner. The right side of each patient's face received 755 nm picosecond laser, and the other side received 1064 nm QS-Nd:YAG laser. Zoom handpiece of 755 nm picosecond laser at fluence of 0.88-1.18 J/cm2 was applied. The treatment protocol used for 1064 nm QS-Nd:YAG laser was 8 mm spot size at fluence of 2...
May 7, 2018: Lasers in Medical Science
Zainab Laftah, Firas Al-Niaimi
Xanthelasmas are localized accumulation of lipid deposits on the eyelids. Lesions are typically asymptomatic and treatment is often sought for cosmetic purposes. Unfortunately, there is paucity of strong evidence in the literature for the effective treatment of normolipidemic xanthelasmas. A literature search using the term "xanthelasma" was carried out in PubMed and Medline databases. Only articles related to treatment were considered and analyzed for their data. Commonly cited treatments include topical trichloroacetic acid, liquid nitrogen cryotherapy, and various lasers including carbon dioxide, Er:YAG, Q-switched Nd:YAG, and pulse dye laser...
January 2018: Journal of Cutaneous and Aesthetic Surgery
Xiaofa Wang, Xiaoling Peng, Junhong Zhang
In this paper, a multistate passively mode-locked thulium-doped fiber laser with nonlinear amplifying loop mirror is reported. An ultra-high numerical aperture fiber is employed to compensate the cavity abnormal dispersion, and the net cavity dispersion value is fixed at -0.046  ps2 . By changing the pump power, three different mode-locked regions, namely Q-switched mode-locking operation, mode-locking operation, and dual-wavelength mode-locking operation, are observed sequentially. When the pump power is raised to the threshold of 1...
May 1, 2018: Applied Optics
Jin Ok Baek, Il-Joong Park, Kyung Real Lee, Ha Ryeong Ryu, Jeongsoo Kim, Seulki Lee, Yu Ri Kim, Hoon Hur
OBJECTIVES: 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...
May 3, 2018: Journal of Cosmetic Dermatology
Jacopo Rubens Negri, Federico Pirzio, Antonio Agnesi
A compact diode-pumped Nd:YVO4 ring laser was developed for generation of relatively long (few tens nanoseconds) single-frequency pulses for high-spectral-resolution LIDAR applications. Exploiting the feedback from an external mirror and Cr:YAG passive Q-switching with pulsed pump, unidirectional single-frequency operation with high quality ∼50-ns, 80-µJ TEM00 pulses was achieved from 100 Hz to 10 kHz. Amplitude, duration and repetition rate stability of the pulses was better than 1%.
April 30, 2018: Optics Express
Ziqi Li, Yuxia Zhang, Chen Cheng, Haohai Yu, Feng Chen
Two-dimensional (2D) materials have generated great interest in the past few years opening up a new dimension in the development of optoelectronics and photonics. In this paper, we demonstrate 6.5 GHz fundamentally Q-switched mode-locked lasers with high performances in the femtosecond laser-written waveguide platform by applying graphene, MoS2 and Bi2 Se3 as saturable absorbers (SAs). The minimum mode-locked pulse duration was measured to be as short as 26 ps in the case of Bi2 Se3 SA. The maximum slope efficiency reached 53% in the case of MoS2 SA...
April 30, 2018: Optics Express
Jian Liu, Xin Ding, Pengbo Jiang, Quan Sheng, Xuanyi Yu, Bing Sun, Rui Shi, Jingbo Wang, Yuntao Bai, Lei Zhao, Guizhong Zhang, Liang Wu, Jianquan Yao
We report an actively Q-switched Nd:YVO4 /YVO4 intracavity Raman laser at second-Stokes wavelength of 1313.6 nm, which is capable of operating efficiently under pulse repetition frequency higher than 80 kHz. A folded coupled cavity is adopted to optimize the fundamental and the Stokes resonators individually and make full use of the high pump intensity on the Raman crystal. With relatively high output coupling of 82% at 1313 nm, the average output power of 5.16 W at 1313 nm is achieved under the incident pump power of 36...
April 16, 2018: Optics Express
Xavier Mateos, Pavel Loiko, Samir Lamrini, Karsten Scholle, Peter Fuhrberg, Soile Suomalainen, Antti Härkönen, Mircea Guina, Sergei Vatnik, Ivan Vedin, Magdalena Aguiló, Francesc Díaz, Yicheng Wang, Uwe Griebner, Valentin Petrov
A Holmium thin-disk laser based on a 3 at.% Ho:KY(WO4 )2 / KY(WO4 )2 epitaxy and single-bounce pumping by a 1960 nm Tm-fiber laser is passively Q-switched with a GaSb-based quantum-well semiconductor saturable absorber mirror. It generates an average output power of 551 mW at 2056 nm with a slope efficiency of 44% (with respect to the absorbed pump power). The best pulse characteristics (energy and duration) are 4.1 μJ / 201 ns at a repetition rate of 135 kHz and the conversion efficiency with respect to the continuous-wave regime is as high as 93%...
April 2, 2018: Optics Express
Licheng Sun, Lei Huang, Meng Yan, Junbiao Fan, Yamin Zheng, Chuang Sun
The performance of the passively Q-switched (PQS) laser deteriorates under high pumping power for the intracavity thermally induced wavefront distortion (thermal distortion for short). A new intracavity deformable mirror (DM) is proposed to compensate the thermal distortion of a PQS laser in this paper. The thermal distortion of the PQS laser is measured using the active deflectometry method. A simulation model is built to investigate the influences of the DM structure parameters on the surface shape of the DM (DMSS)...
April 2, 2018: Optics Express
Ruiheng Xu, Shengzhi Zhao, Kejian Yang, Guiqiu Li, Tao Li, Dechun Li
By using an Open-Aperture Z-scan technique with both femtosecond and nanosecond laser pulses at 1064nm, the nonlinear optical properties of GaAs and Bi-doped GaAs, including the saturable absorption property and reverse saturable absorption property are systematically measured and analyzed directly in detail. Compared to pure GaAs, Bi-doped GaAs has a lower saturation intensity, wider saturable absorption energy region, lower two-photon absorption coefficient, better saturable absorption response and stronger optical limiting response...
April 2, 2018: Optics Express
Xiang Li, Hong Wang, Zhongliang Qiao, Xin Guo, Wanjun Wang, Geok Ing Ng, Yu Zhang, Yingqiang Xu, Zhichuan Niu, Cunzhu Tong, Chongyang Liu
A two-section InGaSb/AlGaAsSb single quantum well (SQW) laser emitting at 2 μm is presented. By varying the absorber bias voltage with a fixed gain current at 130 mA, passive mode locking at ~18.40 GHz, Q-switched mode locking, and passive Q-switching are observed in this laser. In the Q-switched mode locking regimes, the Q-switched RF signal and mode locked RF signal coexist, and the Q-switched lasing and mode-locked lasing happen at different wavelengths. This is the first observation of these three pulsed working regimes in a GaSb-based diode laser...
April 2, 2018: Optics Express
Zhipeng Qin, Ting Hai, Guoqiang Xie, Jingui Ma, Peng Yuan, Liejia Qian, Lei Li, Luming Zhao, Deyuan Shen
With the proposal of dual-wavelength pumping (DWP) scheme, DWP Er:ZBLAN fiber lasers at 3.5 μm have become a fascinating area of research. However, limited by the absence of suitable saturable absorber, passively Q-switched and mode-locked fiber lasers have not been realized in this spectral region. Based on the layer-dependent bandgap and excellent photoelectric characteristics of black phosphorus (BP), BP is a promising candidate for saturable absorber near 3.5 μm. Here, we fabricated a 3.5-μm saturable absorber mirror (SAM) by transferring BP flakes onto a Au-coated mirror...
April 2, 2018: Optics Express
Jian Liu, Xin Ding, Pengbo Jiang, Quan Sheng, Xuanyi Yu, Bing Sun, Jingbo Wang, Rui Shi, Lei Zhao, Yuntao Bai, Guizhong Zhang, Liang Wu, Jianquan Yao
We report herein an efficient actively Q-switched Nd:YVO4 /YVO4 intracavity Raman laser operating at 1176 nm. Factors such as resonator geometry and pumping scheme are optimized to strengthen the power scalability and the conversion efficiency of the intracavity Raman laser. With a folded coupled cavity adopted to make full use of the high pump intensity on the Raman crystal, the first-order Stokes output of 10.32 W at 1176 nm is achieved under the incident pump power of 39 W and pulse repetition frequency of 160 kHz...
April 20, 2018: Applied Optics
Xiaolan Sun, Bin Zhou, Chuanhang Zou, Wei Zhao, Qianqian Huang, Nana Li, Tianxing Wang, Chengbo Mou, Tingyun Wang, Alan R Kost
We demonstrated a passively Q-switched erbium-doped fiber laser (EDFL) using PbS quantum dots in polystyrene films (QDPFs) as saturable absorbers (SAs). Compared to other SAs, PbS QDPFs have advantages of broad absorption range, high quantum yield, low cost, and facile preparation. We have successfully generated stable Q-switched pulses with an average output power of 40.19 mW, a single pulse energy of 586.1 nJ, a repetition rate of 68.04 kHz, a pulse width of 3.9 μs, and a signal-to-noise ratio of 50...
April 20, 2018: Applied Optics
Xiaojie Wang, Xiaolei Wang, Zhifen Zheng, Xihao Qiao, Jun Dong
A synchronous pulsed, dual-wavelength Raman laser at 1164.4 nm and 1174.7 nm has been demonstrated in a Nd:GdVO4 /Cr4+ :YAG/YVO4 passively Q-switched Raman microchip laser (PQSRML). The 1164.4 nm and 1174.7 nm dual-wavelength first-order Stokes laser oscillation is attributed to the conversion of the 1063.2 nm and 1063.43 nm two-longitudinal-mode fundamental lasers with Raman frequency shifts of 816  cm-1 and 890  cm-1 , respectively. Stable dual-wavelength Raman laser pulses with nearly equal spectral intensities have been achieved independent of the pump power...
April 20, 2018: Applied Optics
Nabil Mokrani, Philippe Gillard
This paper presents a physical and statistical approach to laser-induced breakdown in n-decane/N2  + O2 mixtures as a function of incident or absorbed energy. A parametric study, with pressure, fuel purity and equivalence ratio, was conducted to determine the incident and absorbed energies involved in producing breakdown, followed or not by ignition. The experiments were performed using a Q-switched Nd-YAG laser (1064 nm) inside a cylindrical 1-l combustion chamber in the range of 1-100 mJ of incident energy...
March 26, 2018: Journal of Hazardous Materials
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