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Sample records for synchronized dual-wavelength q-switched

  1. Dual-wavelength synchronously Q-switched solid-state laser with multi-layered graphene as saturable absorber.

    PubMed

    Zhao, Yongguang; Li, Xianlei; Xu, Miaomiao; Yu, Haohai; Wu, Yongzhong; Wang, Zhengping; Hao, Xiaopeng; Xu, Xinguang

    2013-02-11

    Using multilayered graphene as the saturable absorber (SA), Nd:LYSO crystal as the laser material, we demonstrated a laser-diode (LD) pumped, dual-wavelength passively Q-switched solid-state laser. The maximum average output power is 1.8 W, the largest pulse energy and highest peak power is 11.3 μJ, 118 W, respectively. As we have known, they are the best results for passively Q-switched operation of graphene. The pulse laser is strong enough to realize extra-cavity frequency conversions. With a KTP crystal as the sum-frequency generator, the dual wavelengths are proved to be well time overlapped, which manifests the synchronous modulation to the dual-wavelength with multi-layered graphene.

  2. Switchable dual-wavelength CNT-based Q-switched using arrayed waveguide gratings (AWG)

    NASA Astrophysics Data System (ADS)

    Ahmad, H.; Hamdan, K. Z.; Muhammad, F. D.; Harun, S. W.; Zulkifli, M. Z.

    2015-02-01

    In this paper, a dual-wavelength synchronously pulsed fiber laser Q-switched by carbon nanotube-based saturable absorber with switchable wavelength spacing enabled using arrayed waveguide grating (AWG) is proposed and demonstrated. By just switching the channels of the AWG, discrete tuning in wavelength spacing of the dual-wavelength Q-switched laser operation can be attained over several nanometers, ranging from 1.6 to 4.0 nm in a stable dual-wavelength regime without employing any modulation technique or intracavity spectral filters. Our experimental results show that the fiber laser can generate Q-switched microsecond pulses with a wide repetition rate range, starting from 12.0 kHz to a maximum value of 54.9 kHz. This proposed system is also reasonably simple to realize at low cost.

  3. Graphene-based passively Q-switched dual-wavelength erbium-doped fiber laser.

    PubMed

    Luo, Zhengqian; Zhou, Min; Weng, Jian; Huang, Guoming; Xu, Huiying; Ye, Chenchun; Cai, Zhiping

    2010-11-01

    We demonstrate a compact Q-switched dual-wavelength erbium-doped fiber (EDF) laser based on graphene as a saturable absorber (SA). By optically driven deposition of graphene on a fiber core, the SA is constructed and inserted into a diode-pumped EDF laser cavity. Also benefiting from the strong third-order optical nonlinearity of graphene to suppress the mode competition of EDF, a stable dual-wavelength Q-switching operation has been achieved using a two-reflection peak fiber Bragg grating as the external cavity mirror. The Q-switched EDF laser has a low pump threshold of 6.5 mW at 974 nm and a wide range of pulse-repetition rate from 3.3 to 65.9 kHz. The pulse duration and the pulse energy have been characterized. This is, to the best of our knowledge, the first demonstration of a graphene-based Q-switched laser.

  4. Dual-wavelength passively Q-switched Nd:GYSGG laser by tungsten disulfide saturable absorber.

    PubMed

    Gao, Y J; Zhang, B Y; Song, Q; Wang, G J; Wang, W J; Hong, M H; Dou, R Q; Sun, D L; Zhang, Q L

    2016-06-20

    A dual-wavelength passively Q-switched Nd:GYSGG laser using vacuum evaporating tungsten disulfide (WS2) as a saturable absorber was demonstrated for the first time to the best of our knowledge. The WS2 saturable absorber was prepared simply by evaporating nanometer WS2 powders onto a quartz substrate in a vacuum. By inserting the WS2 saturable absorber into the laser cavity, stable Q-switched laser operation was achieved with a maximum average output power of 367 mW, a pulse repetition rate of 70.7 kHz, the shortest pulse width of 591 ns, and pulse energy of about 1.05 μJ. By vacuum evaporation method, a high-quality WS2 saturable absorber can be produced, and it seems to be a suitable method for fabrication of 2D transition metal dichalcogenides.

  5. Simultaneous dual-wavelength Q-switched Nd:YAG laser at 1052 and 1073  nm.

    PubMed

    Lin, Haifeng; Zhu, Wenzhang; Xiong, Feibing; Ruan, Jianjian

    2017-02-01

    We report a continuous-wave dual-wavelength Nd:YAG laser at 1052 and 1073 nm, for the first time to the best of our knowledge, in free-running mode. The maximum output power reaches 6.64 W with slope efficiency of about 42.1% with respect to the absorbed power. Inserting a Cr:YAG saturable absorber, the dual-wavelength laser can operate in the Q-switching regime with maximum average output power of 880 mW. The minimum pulse width and the highest pulse repetition rate are 28 ns and 17.12 kHz, respectively. The dual-wavelength laser has potential to generate a 5.7 THz wave via the difference-frequency method.

  6. Using a black phosphorus saturable absorber to generate dual wavelengths in a Q-switched ytterbium-doped fiber laser

    NASA Astrophysics Data System (ADS)

    Rashid, F. A. A.; Azzuhri, Saaidal R.; Salim, M. A. M.; Shaharuddin, R. A.; Ismail, M. A.; Ismail, M. F.; Razak, M. Z. A.; Ahmad, H.

    2016-08-01

    Using a few-layer black phosphorus (BP) thin film that acts as a saturable absorber (SA) in an ytterbium-doped fiber laser setup, we experimentally demonstrated a passively dual-wavelength Q-switching laser operation. The setup also incorporated a D-shaped polished fiber as a wavelength selective filter. As the SA was used in the ring cavity, a dual-wavelength Q-switch produced consistent outputs at 1038.68 and 1042.05 nm. A maximum pulse energy of 2.09 nJ with a shortest pulse width of 1.16 µs was measured for the achieved pulses. In addition, the repetition rate increased from 52.52 to 58.73 kHz with the increment of the pump level. Throughout the measurement process, the results were obtained consistently and this demonstrates that the BP film is a very good candidate to produce Q-switching pulses for the 1 micron region.

  7. Dual-wavelength continuous-wave and passively Q-switched Nd,Y:SrF2 ceramic laser

    NASA Astrophysics Data System (ADS)

    Zhang, Feng; Liu, Jie; Li, Weiwei; Mei, Bingchu; Jiang, Dapeng; Qian, Xiaobo; Su, Liangbi

    2016-10-01

    A polycrystalline ceramic based on an Nd,Y:SrF2 single crystal was successfully fabricated and its laser performance was experimentally investigated. We obtained dual-wavelength continuous-wave operation at the wavelengths of 1050.5 and 1058.0 nm. The maximum output power and slope efficiency were 750 mW and 31.5%, respectively. In the passively Q-switched operation, the shortest pulse with a 169-ns duration was also obtained, and the corresponding maximum repetition rate and single pulse energy were 7.3 kHz and 19.2 μJ, respectively.

  8. LD end-pumped acousto-optic Q-switched 1319 nm/1338 nm dual-wavelength Nd:YAG laser

    NASA Astrophysics Data System (ADS)

    Wu, C. T.; Yu, M.; Wang, C.; Yu, K.; Yu, Y. J.; Chen, X. Y.; Jin, G. Y.

    2016-10-01

    Laser characteristics of acousto-optic Q-switched operation of 1319 nm/1338 nm dual-wavelength composite Nd:YAG laser were studied. Maximum output power of 5.77 W was achieved in CW operation. Under Q-switched operation, the maximum peak power of 3.96 kW and minimum pulse width of 65.6 ns was obtained at repetition frequency of 20 kHz with the duty ratio of 96%. The influence of the duration of the ultrasonic field acted on the Q-switch to the output characteristics of dual-wavelength composite Nd:YAG laser had been reported first time.

  9. Photonic crystal fiber based dual-wavelength Q-switched fiber laser using graphene oxide as a saturable absorber.

    PubMed

    Ahmad, H; Soltanian, M R K; Pua, C H; Alimadad, M; Harun, S W

    2014-06-01

    A Q-switched dual-wavelength fiber laser with narrow channel spacing is proposed and demonstrated. The fiber laser is built around a 3 m long erbium doped fiber as the gain medium and a 10 cm long photonic crystal fiber (PCF) as the element used to generate the dual-wavelength output. The PCF has a solid core approximately 4.37 μm in diameter and is surrounded by microscopic air-holes with a diameter of about 5.06 μm each as well as a zero-dispersion wavelength of about 980 nm. A graphene oxide based saturable absorber is used to generate the desired pulsed output. At the maximum pump power of 72 mW the laser is capable of generating pulses with a repetition rate and pulse-width of 31.0 kHz and 7.0 μs, respectively, as well as an average output power and pulse energy of 0.086 mW and 2.8 nJ, respectively. The proposed fiber laser has substantial potential for use in applications that require longer duration pulsed outputs such as in range finding and terahertz radiation generation.

  10. Passively Q-switched dual-wavelength Yb:LSO laser based on tungsten disulphide saturable absorber

    NASA Astrophysics Data System (ADS)

    Jing-Hui, Liu; Jin-Rong, Tian; He-Yang, Guoyu; Run-Qin, Xu; Ke-Xuan, Li; Yan-Rong, Song; Xin-Ping, Zhang; Liang-Bi, Su; Jun, Xu

    2016-03-01

    We demonstrate a passively Q-switched Yb:LSO laser based on tungsten disulphide (WS2) saturable absorber operating at 1034 nm and 1056 nm simultaneously. The saturable absorbers were fabricated by spin coating method. With low speed, the WS2 nanoplatelets embedded in polyvinyl alcohol could be coated on a BK7 glass substrate coated with high-refractive-index thin polymer. The shortest pulse width of 1.6 μs with a repetition rate of 76.9 kHz is obtained. As the pump power increases to 9 W, the maximum output power is measured to be 250 mW, corresponding to a single pulse energy of 3.25 μJ. To the best of our knowledge, this is the first time to obtain dual-wavelength Q-switched solid-state laser using few-layer WS2 nanoplatelets. Project supported by the National Scientific Research Project of China (Grant No. 61177047), Beijing Municipal Natural Science Foundation, China (Grant No. 1102005), and the Basic Research Foundation of Beijing University of Technology, China (Grant No. X3006111201501).

  11. Switchable dual-wavelength Q-switched and mode-locked fiber lasers using a large-angle tilted fiber grating.

    PubMed

    Zhang, Zuxing; Mou, Chengbo; Yan, Zhijun; Wang, Yongjin; Zhou, Kaiming; Zhang, Lin

    2015-01-26

    We proposed and demonstrated pulsed fiber lasers Q-switched and mode-locked by using a large-angle tilted fiber grating, for the first time to our best knowledge. Owing to the unique polarization properties of the large-angle tilted fiber grating (LA-TFG), i.e. polarization-dependent loss and polarization-mode splitting, switchable dual-wavelength Q-switched and mode-locked pulses have been achieved with short and long cavities, respectively. For the mode-locking case, the laser was under the operation of nanosecond rectangular pulses, due to the peak-power clamping effect. With the increasing pump power, the durations of both single- and dual-wavelength rectangular pulses increase. It was also found that each filtered wavelength of the dual-wavelength rectangular pulse corresponds to an individual nanosecond rectangular pulse by employing a tunable bandpass filter.

  12. Diode-pumped passively dual-wavelength Q-switched Nd:GYSGG laser using graphene oxide as the saturable absorber.

    PubMed

    Song, Qi; Wang, Guoju; Zhang, Bingyuan; Wang, Wenjun; Wang, Minghong; Zhang, Qingli; Sun, Guihua; Bo, Yong; Peng, Qinjun

    2015-04-01

    The performance of a diode end-pumped passively Q-switched dual-wavelength Nd:GYSGG laser operating at 1057.28 and 1060.65 nm with graphene oxide as the saturable absorber was demonstrated. The maximum dual-wavelength average output power of 521 mW was achieved under the absorbed pump power of 5.4 W, corresponding to the optical-to-optical conversion and slope efficiency of 9.8% and 21%, respectively. The minimum pulse width was 115 ns with a pulse repetition rate of 338 kHz.

  13. All-fiber dual wavelength passive Q-switched fiber laser using a dispersion-decreasing taper fiber in a nonlinear loop mirror.

    PubMed

    Ahmad, Harith; Dernaika, Mohamad; Harun, Sulaiman Wadi

    2014-09-22

    This paper describes a proposal and successful demonstration of a dual wavelength all-fiber passively Q-switched erbium-doped fiber ring laser. The Q-switch operation was realized by using a nonlinear loop mirror that incorporated an unbalanced dispersion-decreasing taper fiber to act as a saturable absorber without additional elements. This setup enabled a fiber ring laser to achieve a performance of 48.7 kHz repetition rate with pulse duration of around 3.2 μs and approximate pulse energy of 20 nJ.

  14. Dual-wavelength Q-switched Er:SrF2 laser with a black phosphorus absorber in the mid-infrared region.

    PubMed

    Liu, Jingjing; Liu, Jie; Guo, Zhinan; Zhang, Han; Ma, Weiwei; Wang, Jingya; Su, Liangbi

    2016-12-26

    An efficient Er:SrF2 crystal, lightly Er-doped to a concentration of 4at.%, was successfully grown by the traditional Bridgman method and displayed excellent spectral properties. A diode-end-pumped passively Q-switched dual-wavelength laser, operating at 2.79 μm wavelength, was demonstrated with this crystal by using black phosphorus as the saturable absorber (BP-SA). In the compact passively Q-switched Er:SrF2 laser, the maximum average output power of 180 mW was achieved at an absorbed pump power of 2.47 W, with a pulse duration of 702 ns and a repetition rate of 77.03 kHz. To the best of our knowledge, this is the first reported application of BP-SA to dual-wavelength pulse laser operation in the mid-infrared region.

  15. All-fiber dual-wavelength Q-switched and mode-locked EDFL by SMF-THDF-SMF structure as a saturable absorber

    NASA Astrophysics Data System (ADS)

    Latiff, A. A.; Kadir, N. A.; Ismail, E. I.; Shamsuddin, H.; Ahmad, H.; Harun, S. W.

    2017-04-01

    We demonstrate all-fiber dual-wavelength Q-switched and mode-locked erbium-doped fiber laser (EDFL) by utilizing the thulium-holmium-doped fiber (THDF) as a fiber saturable absorber (SA) and also a Mach-Zehnder interferometer (MZI) element. The 19 cm long THDF has a core diameter of 11.5 μm, refractive index difference of 0.005, and cutoff wavelength of 1810 nm. Stable dual-wavelength Q-switching operation was generated at 1555.14 nm and 1557.64 nm with free spectral range (FSR) of 2.5 nm. The repetition rate of 14.45-78.49 kHz was obtained between 12 and 100 mW pump power. At maximum pump power, the maximum output power and pulse energy were 2.58 mW and 32.87 nJ, respectively. By adding 195 cm long SMF in the same cavity, the stable dual-wavelength mode-locking operation was started at 166 mW and continue stable to 201 mW pump power. This mode-locking operation produced stable dual-wavelength pulses at 1530.34 nm and 1532.84 nm with a repetition rate of 1 MHz with a pulse duration of 128 ns and signal-to-noise ratio (SNR) of 62 dB. It shares the same value of FSR in Q-switching operation. The highest output power of 1.57 nJ corresponds to the maximum output power of 1.57 mW was obtained. Our results validate the linear absorption characteristic at C-band region and multimode fiber effect of THDF can be utilized as SA to generate stable all-fiber dual-wavelength pulsed lasers. Remarkably, these findings expand a fiber gain medium application in short pulse generation.

  16. Q-switched dual-wavelength fiber laser using a graphene oxide saturable absorber and singlemode-multimode-singlemode fiber structure

    NASA Astrophysics Data System (ADS)

    Ahmad, H.; Zulkifli, A. Z.; Yasin, M.; Thambiratnam, K.

    2016-10-01

    A Q-switched dual-wavelength fiber laser using a graphene oxide-based saturable absorber to generate the desired output pulses is proposed and demonstrated. The system utilizes a singlemode-multimode-singlemode fiber structure to control the net losses in the cavity so that only two dominant wavelengths are allowed to oscillate. The proposed system is capable of generating an output with a high repetition rate of 27.1 kHz and a narrow pulse width of 4.03 µs. The output pulses also have average output power and pulse energy of up to 0.5 mW and 18.5 nJ, respectively. The 1st harmonic obtained has a high signal-to-noise ratio of 33.2 dB, indicating a highly stable pulse output with minimum mode hopping.

  17. Stable narrow spacing dual-wavelength Q-switched graphene oxide embedded in a photonic crystal fiber

    NASA Astrophysics Data System (ADS)

    Ahmad, H.; Soltanian, M. R. K.; Alimadad, M.; Harun, S. W.

    2014-10-01

    An ultra-stable dual-wavelength saturable absorber based on a cladding-embedded commercial graphene oxide (GO) solution by capillary action in a solid core photonic crystal fiber (PCF) is demonstrated for the first time. The saturation absorption property is achieved through evanescent coupling between the guided light and the cladding-filled graphene layers. Stable spacing dual-wavelength fiber lasing is attained by controlling the polarization state of a simple 0.9 m long ring of highly doped Leikki Er80-8/125 erbium-doped fiber as the primary gain medium with PCF, polarization controller and tunable bandpass filter. Embedded GO is used to generate the desired pulsed output, and the laser is capable of generating pulses having a repetition rate of 24 kHz with an average output power and pulse energy of 0.167 mW and 8.98 nJ, respectively, at the maximum pump power of 220 mW.

  18. InGaAs/GaAs saturable absorber for diode-pumped passively Q-switched dual-wavelength Tm:YAP lasers.

    PubMed

    Yao, Baoquan; Tian, Yi; Li, Gang; Wang, Yuezhu

    2010-06-21

    We demonstrate the first use of InGaAs/GaAs as a saturable absorber in the Q-switching of a diode pumped Tm(3+) doped laser operating at the wavelengths of 1940 nm and 1986 nm. The influence of the semiconductor saturable absorber's (SESA) position and thermal lens effect on the Q-switch characteristics was investigated. With a pump power of 35 W, the maximum pulse energy of 28.1 microJ with a pulse width of 447 ns at the pulse repetition frequency (PRF) of 43.7 kHz was obtained by selecting the appropriate position of the SESA.

  19. Synchronized dual tunable wavelength Q-switched Nd:Glass laser.

    PubMed

    Men, Shaojie; Liu, Zhaojun; Cong, Zhenhua; Liu, Yang; Zhang, Sasa; Li, Yongfu; Lu, Qingming; Zhang, Xingyu

    2014-12-15

    A flash-lamp pumped electro-optically Q-switched dual tunable wavelength Nd:Glass laser is demonstrated. An Nd:Glass rod was selected as the laser medium and a DKDP crystal was employed as the Q-switch. A cubic polarizer was placed in the cavity to divide the randomly polarized radiation into two orthogonally polarized beams. The two beams were tuned by two Littman-gratings and output independently. For Q-switched operation, the tuning range was 1050.1 - 1061.6 nm and 1050.5 - 1060.2 nm for the horizontal and vertical polarizations, respectively. When the horizontally polarized output was fixed at 1059.1 nm, the synchronized vertically polarized one can be tuned from 1051.5 to 1057.5 nm.

  20. Dual-wavelength synchronously mode-locked Nd:CNGG laser.

    PubMed

    Xie, G Q; Tang, D Y; Luo, H; Zhang, H J; Yu, H H; Wang, J Y; Tao, X T; Jiang, M H; Qian, L J

    2008-08-15

    We have experimentally demonstrated a dual-wavelength synchronously mode-locked Nd:CNGG laser based on the semiconductor saturable absorber mirror technique. Mode locking was achieved simultaneously on two gain bands of the crystal that have a central wavelength separation of 2.4 nm. The fundamental mode-locked pulse train has a repetition rate of 88 MHz and pulse duration of 5 ps, with an average output power of approximately 90 mW. Autocorrelation measurements show that each of the synchronously mode-locked pulses consists of a train of quasi-periodic beat pulses with a 660 fs pulse width and a 0.63 THz repetition rate.

  1. Temporal synchronization and spectral combining of pulses from fiber lasers Q-switched by independent MEMS micro-mirrors.

    PubMed

    Fabert, Marc; Desfarges-Berthelemot, Agnès; Kermène, Vincent; Crunteanu, Aurelian

    2012-09-24

    We present what we believe to be the first demonstration of spectral combining of multiple fiber lasers Q-switched by independent micro-electro-mechanical system (MEMS). By correlating the actuation of the individual MEMS devices, the associated Q-switched lasers can be operated in either synchronous or asynchronous modes in such a way that their overall combined output may result in high energy emission pulses or in laser emission with higher pulse repetition rate. In a proof-of-principle experiment, we demonstrate the combination of four individual Q-switched lasers (each of them operating at 20 kHz repetition rate) leading to a final laser system generating pulses with a repetition rate of 80 kHz.

  2. Dual-wavelength asynchronous and synchronous mode-locking operation by a Nd:CLTGG disordered crystal

    NASA Astrophysics Data System (ADS)

    Xu, J.-L.; Guo, S.-Y.; He, J.-L.; Zhang, B.-Y.; Yang, Y.; Yang, H.; Liu, S.-D.

    2012-04-01

    We have developed a diode-pumped passively mode-locked Nd3+:CLTGG laser operated at 1059 and 1061 nm with a semiconductor saturable absorber mirror (SESAM). The relative intensity of the two spectrum wavelengths is adjustable, allowing asynchronous and synchronous generation of the dual-wavelength pulses. In synchronous mode-locking regime, a total average output power of 383 mW was obtained with pulse duration of 3.5 ps and repetition rate of 42 MHz. The two spectral bands of 1059 and 1061 nm had the same intensities and areas, indicating 1:1 for the pulse energy ratio. It is desirable for efficiently generating a terahertz wave by difference-frequency generation.

  3. Dual Wavelength Lasers

    NASA Technical Reports Server (NTRS)

    Walsh, Brian M.

    2010-01-01

    Dual wavelength lasers are discussed, covering fundamental aspects on the spectroscopy and laser dynamics of these systems. Results on Tm:Ho:Er:YAG dual wavelength laser action (Ho at 2.1 m and Er at 2.9 m) as well as Nd:YAG (1.06 and 1.3 m) are presented as examples of such dual wavelength systems. Dual wavelength lasers are not common, but there are criteria that govern their behavior. Based on experimental studies demonstrating simultaneous dual wavelength lasing, some general conclusions regarding the successful operation of multi-wavelength lasers can be made.

  4. Passively synchronized Q-switched and mode-locked dual-band Tm3+:ZBLAN fiber lasers using a common graphene saturable absorber

    NASA Astrophysics Data System (ADS)

    Jia, Chenglai; Shastri, Bhavin J.; Abdukerim, Nurmemet; Rochette, Martin; Prucnal, Paul R.; Saad, Mohammed; Chen, Lawrence R.

    2016-11-01

    Dual-band fiber lasers are emerging as a promising technology to penetrate new industrial and medical applications from their dual-band properties, in addition to providing compactness and environmental robustness from the waveguide structure. Here, we demonstrate the use of a common graphene saturable absorber and a single gain medium (Tm3+:ZBLAN fiber) to implement (1) a dual-band fiber ring laser with synchronized Q-switched pulses at wavelengths of 1480 nm and 1840 nm, and (2) a dual-band fiber linear laser with synchronized mode-locked pulses at wavelengths of 1480 nm and 1845 nm. Q-switched operation at 1480 nm and 1840 nm is achieved with a synchronized repetition rate from 20 kHz to 40.5 kHz. For synchronous mode-locked operation, pulses with full-width at half maximum durations of 610 fs and 1.68 ps at wavelengths of 1480 nm and 1845 nm, respectively, are obtained at a repetition rate of 12.3 MHz. These dual-band pulsed sources with an ultra-broadband wavelength separation of ~360 nm will add new capabilities in applications including optical sensing, spectroscopy, and communications.

  5. Passively synchronized Q-switched and mode-locked dual-band Tm(3+):ZBLAN fiber lasers using a common graphene saturable absorber.

    PubMed

    Jia, Chenglai; Shastri, Bhavin J; Abdukerim, Nurmemet; Rochette, Martin; Prucnal, Paul R; Saad, Mohammed; Chen, Lawrence R

    2016-11-02

    Dual-band fiber lasers are emerging as a promising technology to penetrate new industrial and medical applications from their dual-band properties, in addition to providing compactness and environmental robustness from the waveguide structure. Here, we demonstrate the use of a common graphene saturable absorber and a single gain medium (Tm(3+):ZBLAN fiber) to implement (1) a dual-band fiber ring laser with synchronized Q-switched pulses at wavelengths of 1480 nm and 1840 nm, and (2) a dual-band fiber linear laser with synchronized mode-locked pulses at wavelengths of 1480 nm and 1845 nm. Q-switched operation at 1480 nm and 1840 nm is achieved with a synchronized repetition rate from 20 kHz to 40.5 kHz. For synchronous mode-locked operation, pulses with full-width at half maximum durations of 610 fs and 1.68 ps at wavelengths of 1480 nm and 1845 nm, respectively, are obtained at a repetition rate of 12.3 MHz. These dual-band pulsed sources with an ultra-broadband wavelength separation of ~360 nm will add new capabilities in applications including optical sensing, spectroscopy, and communications.

  6. Passively synchronized Q-switched and mode-locked dual-band Tm3+:ZBLAN fiber lasers using a common graphene saturable absorber

    PubMed Central

    Jia, Chenglai; Shastri, Bhavin J.; Abdukerim, Nurmemet; Rochette, Martin; Prucnal, Paul R.; Saad, Mohammed; Chen, Lawrence R.

    2016-01-01

    Dual-band fiber lasers are emerging as a promising technology to penetrate new industrial and medical applications from their dual-band properties, in addition to providing compactness and environmental robustness from the waveguide structure. Here, we demonstrate the use of a common graphene saturable absorber and a single gain medium (Tm3+:ZBLAN fiber) to implement (1) a dual-band fiber ring laser with synchronized Q-switched pulses at wavelengths of 1480 nm and 1840 nm, and (2) a dual-band fiber linear laser with synchronized mode-locked pulses at wavelengths of 1480 nm and 1845 nm. Q-switched operation at 1480 nm and 1840 nm is achieved with a synchronized repetition rate from 20 kHz to 40.5 kHz. For synchronous mode-locked operation, pulses with full-width at half maximum durations of 610 fs and 1.68 ps at wavelengths of 1480 nm and 1845 nm, respectively, are obtained at a repetition rate of 12.3 MHz. These dual-band pulsed sources with an ultra-broadband wavelength separation of ~360 nm will add new capabilities in applications including optical sensing, spectroscopy, and communications. PMID:27804993

  7. Dual-wavelength synchronously mode-locked laser of a Nd:Y3ScAl4O12 disordered crystal

    NASA Astrophysics Data System (ADS)

    Feng, Chao; Zhang, Huanian; Wang, Qingpu; Fang, Jiaxiong

    2017-04-01

    We demonstrated a dual-wavelength passively mode-locked Nd:YSAG laser using a semiconductor saturable absorber mirror as the modulator. The maximum average output power was about 470 mW under the absorbed pump power of 4.2 W. The laser exhibited stable double wavelength synchronous mode-locked oscillation at 1060.8 nm and 1063.2 nm. The pulsed repetition rate was about 87.4 MHz, and the single pulse energy was calculated to be 5.38 nJ. The envelope of the autocorrelation interference pattern presented a Gaussian pulse shape and the pulse width was about 3.8 ps. The beat pulse had a repetition rate of 0.67 THz and the beat pulse width was about 800 fs. Additionally, numerical simulation was conducted to analyze the autocorrelation trace.

  8. High-power dual-wavelength laser with disordered Nd:CNGG crystals.

    PubMed

    Yu, Haohai; Zhang, Huaijin; Wang, Zhengping; Wang, Jiyang; Yu, Yonggui; Shi, Zibin; Zhang, Xingyu; Jiang, Minhua

    2009-01-15

    We demonstrate the high-power dual-wavelength laser output with disordered Nd:CNGG laser crystals. Continuous-wave output power of 4.03 W was obtained under the incident pump power of 15.62 W. In the passively Q-switched operation, the shortest pulse width, largest pulse energy, and highest peak power were achieved to be 12.9 ns, 173.16 microJ, and 12.3 kW, respectively, with Cr(4+):YAG crystals as the saturable absorbers. By spectral analysis, the output lasers were found to have dual wavelengths. We believed that the passively Q-switched dual-wavelength laser should be possible to be used as a source for the generation of terahertz radiation.

  9. Coherent THz Repetitive Pulse Generation in a GaSe Crystal by Dual-wavelength Nd:YLF Laser

    NASA Astrophysics Data System (ADS)

    Bezotosnyi, V. V.; Cheshev, E. A.; Gorbunkov, M. V.; Koromyslov, A. L.; Krokhin, O. N.; Mityagin, Yu. A.; Popov, Yu. M.; Savinov, S. A.; Tunkin, V. G.

    We present modification of difference frequency generator of coherent THz radiation in a nonlinear GaSe crystal using dual-wavelength diode-pumped solid-state Nd:YLF laser. Generation at the two wavelengths (1.047 and 1.053 μm) was carried out by equalization of the gains at these wavelengths near the frequency degeneracy of the transverse modes in resonator cavity, Q-switched by acousto-optical modulator. The main parameters of the device were measured: angular synchronism (width 0.6 degrees), polarization ratio (1:100), conversion efficiency (10-7), pulse power (0.8 mW), frequency and width (53,8 сm-1, 0,6 сm-1), pulse width and repetition rate (10 ns,7 kHz). The method is promising for practical purposes.

  10. Dual-wavelength eye-safe Nd:GYSGG/YVO4 intracavity Raman laser under in-band pumping

    NASA Astrophysics Data System (ADS)

    Jiang, P. B.; Sheng, Q.; Ding, X.; Sun, B.; Liu, J.; Zhao, C.; Zhang, G. Z.; Yu, X. Y.; Li, B.; Wu, L.; Yao, J. Q.

    2017-01-01

    An acousto-optic (AO) Q-switched dual-wavelength laser operating at 1.5 μm eye-safe region is demonstrated via stimulated Raman scatting of a-cut YVO4-Nd:YVO4 crystal within an end-pumped dual-wavelength Nd:GYSGG laser cavity. The in-band pumping absorption peak and coefficient of the dual-wavelength laser crystal Nd:GYSGG are measured in order to carry out efficient pumping, thus overcoming the drawbacks of short thermal focal length of the crystal and scale up the eye-safe output. Under 23.2 W absorbed pump power, 2.11 W of simultaneous dual-wavelength outputs at 1497 and 1516 nm are obtained with a pulse repetition rate of 23 kHz and a corresponding conversion efficiency of 9.1%.

  11. Continuous-wave and actively Q-switched Nd:LSO crystal lasers

    NASA Astrophysics Data System (ADS)

    Zhuang, S.; Li, D.; Xu, X.; Wang, Z.; Yu, H.; Xu, J.; Chen, L.; Zhao, Y.; Guo, L.; Xu, X.

    2012-04-01

    With a fiber coupled laser diode array as the pump source, Nd-doped Lu2SiO5 (Nd:LSO) crystal lasers at 4F3/2→4I11/2 and 4F3/2→4I13/2 transitions were demonstrated. The active Q-switched dual-wavelength lasers at about 1.08 μm, as well as continuous-wave (CW) and active Q-switched lasers at 1357 nm are reported for the first time, to the best of our knowledge. Considering the small emission cross-sections and long fluorescence lifetime, this material possesses large energy storage ability and excellent Q-switched properties. The special emission wavelength at 1357 nm will have promising applications to be used in many fields, such as THz generation, pumping of Cr3+:LiSAF, repumping of strontium optical clock, laser Doppler velocimeter and distributed fiber sensor.

  12. Nd:(Gd0.3Y0.7)2SiO5 crystal: A novel efficient dual-wavelength continuous-wave medium

    NASA Astrophysics Data System (ADS)

    Xu, Xiaodong; Di, Juqing; Zhang, Jian; Tang, Dingyuan; Xu, Jun

    2016-05-01

    Efficient dual-wavelength continuous-wave (CW) and passively Q-switched laser operation of Nd:(Gd0.3Y0.7)2SiO5 crystal were investigated for the first time to our knowledge. Maximum CW output power of 2.3 W was obtained under the absorbed pump power of 4.6 W, corresponding to the slope efficiency of 55%. Dual-wavelength CW laser with respective wavelengths around 1074 nm and 1078 nm were achieved. With Cr4+:YAG as the saturable absorber, passive Q-switched performance was obtained. The slope efficiency of passively Q-switched operation was 45%. The shortest pulse width, the corresponding pulse energy and peak power were calculated to be 13.1 ns, 50.2 μJ and 3.8 kW, respectively.

  13. Electro-optic Q-switch

    NASA Technical Reports Server (NTRS)

    Zou, Yingyin (Inventor); Chen, Qiushui (Inventor); Zhang, Run (Inventor); Jiang, Hua (Inventor)

    2006-01-01

    An electro-optic Q-switch for generating sequence of laser pulses was disclosed. The Q-switch comprises a quadratic electro-optic material and is connected with an electronic unit generating a radio frequency wave with positive and negative pulses alternatively. The Q-switch is controlled by the radio frequency wave in such a way that laser pulse is generated when the radio frequency wave changes its polarity.

  14. Laser with optically driven Q-switch

    NASA Technical Reports Server (NTRS)

    Hemmati, Hamid (Inventor)

    1993-01-01

    An optically driven interactive Q-switch, i.e., a Q-switch that responds to a short pulse of light, for example, from external light-emitting diodes (LEDs) or diode lasers, is provided for producing an output laser pulse from electronic energy stored in a laser medium. Q-switching is thus achieved on demand by electrically pulsing the light source to produce a pulse of light directed onto a Q-switch medium in the laser cavity. Electronic control of the light pulse from the external source will thus provide not only efficient Q-switching frequency but also independent control of output laser pulse width with a fast rise time for each output laser pulse.

  15. Laser with optically driven Q-switch

    NASA Technical Reports Server (NTRS)

    Hemmati, Hamid (Inventor)

    1995-01-01

    An optically driven interactive Q-switch, i.e., a Q-switch that responds to a short pulse of light, for example, from external light-emitting diodes (LED's) or diode lasers, is provided for producing an output laser pulse from electronic energy stored in a laser medium. Q-switching is thus achieved on demand by electrically pulsing the light source to produce a pulse of light directed onto a Q-switch medium in the laser cavity. Electronic control of the light pulse from the external source will thus provide not only efficient Q-switching frequency but also independent control of output laser pulse width with a fast rise time for each output laser pulse.

  16. Two-wavelength passively Q-switched ytterbium doped fiber laser.

    PubMed

    Pan, Lei; Utkin, Ilya; Fedosejevs, Robert

    2008-08-04

    A high power passively Q-switched dual wavelength Yb fiber laser using a Cr4+:YAG saturable absorber has been realized. Two wavelengths centered at 1040 nm and 1070 nm are generated directly from the cladding pumped Yb doped fiber laser. The pulse trains exhibit regions of stability and instability dependent on the pump power. At a pump power of 7.8 W, 1040 nm and 1070 nm pulses are generated alternatively, with pulse durations of 105 ns, pulse-repetition rates of 32 KHz and average pulse energies of 56 microJ and 47 microJ, respectively. A theoretical model is developed to simulate the two-wavelength Q-switched operation, which gives qualitative agreement with the experimental observations.

  17. Q-Switched Nd: YAG Laser Micro-Machining System

    SciTech Connect

    Messaoud, S.; Allam, A.; Siserir, F.; Bouceta, Y.; Kerdja, T.; Ouadjaout, D.

    2008-09-23

    In this paper, we present the design of a low cost Q-switched Nd: YAG laser micro-machining system for photo masks fabrication. It consists of: Nd:YAG laser source, beam delivery system, X-Y table, PC, The CCD camera and TV monitor. The synchronization between the laser source and the X-Y table is realised by NI PCI-7342, the two axis MID-7602 and LabVIEW based program. The first step of this work consists of engraving continuous and discontinuous lines on a thin film metal with a 100 {mu}m resolution by using the YG 980 Quantel Q-switched Nd:YAG laser.

  18. Continuous-wave and passively Q-switched Nd:LYSO lasers

    NASA Astrophysics Data System (ADS)

    Zhuang, S. D.; Xu, X. D.; Wang, Z. P.; Li, D. Z.; Yu, H. H.; Xu, J.; Guo, L.; Chen, L. J.; Zhao, Y. G.; Xu, X. G.

    2011-04-01

    Continuous-wave (CW) and passively Q-switched performance of a Nd-doped oyorthosilicate mixing crystal, (Nd0.005Lu0.4975Y0.4975)2SiO5 (Nd:LYSO), were reported. As a result, new dual-wavelength all-solid-state lasers at 1075 and 1079 nm were achieved. When the absorbed pump power was 3.87 W, the CW laser produced 1.1 W output, corresponding to an optical conversion efficiency of 28.4% and a slope efficiency of 32.4%. By using a Cr4+:YAG wafer as the saturable absorber, we achieved Q-switching operation of Nd:LYSO crystal. The maximal average output power, shortest pulse width, largest pulse energy and highest peak power were measured to be 294 mW, 27.5 ns, 34.3 μJ and 1.18 kW, respectively. By difference frequency, these dual-wavelength lasers have potential applications for the generation of a broadband coherent radiation from 0.7-1.3 THz.

  19. Terahertz source at 9.4 THz based on a dual-wavelength infrared laser and quasi-phase matching in organic crystals OH1

    SciTech Connect

    Majkić, A. Zgonik, M.; Petelin, A.; Jazbinšek, M.; Ruiz, B.; Medrano, C.; Günter, P.

    2014-10-06

    We present a compact, room temperature, and narrowband terahertz source, based on difference-frequency generation in the organic nonlinear optical crystals OH1 (2-[3-(4-hydroxystyryl)-5,5-dimethylcyclohex-2-enylidene]malononitrile). The system employs a specific dual-wavelength infrared laser that emits coaxial, synchronous 10-ns pulses of similar energy and duration at wavelengths of 1064 nm and 1030 nm by using Nd:YAG and Yb:YAG crystals within the split laser cavity. The common part of the laser cavity comprises an acousto-optic Q-switch and an output coupler. The output is frequency-mixed in a stack of several OH1 crystals in a quasi-phase-matching configuration, which is determined on the basis of refractive index and absorption measurements in the 1–11 THz range. The system generates terahertz radiation in pulse trains with 1.0 μW average power and a near-Gaussian intensity profile.

  20. Q-Switching in a Neodymium Laser

    ERIC Educational Resources Information Center

    Holgado, Warein; Sola, Inigo J.; Jarque, Enrique Conejero; Jarabo, Sebastian; Roso, Luis

    2012-01-01

    We present a laboratory experiment for advanced undergraduate or graduate laser-related classes to study the performance of a neodymium laser. In the experiment, the student has to build the neodymium laser using an open cavity. After that, the cavity losses are modulated with an optical chopper located inside, so the Q-switching regime is…

  1. Use of a vacuum-planar photodiode to drive an electro-optic Q switch directly.

    PubMed

    Stankov, K A; Milev, I Y

    1991-12-20

    A vacuum photodiode was used to drive a Pockels cell directly in an optical-feedback arrangement. This technique was used to achieve Q switching and a single-longitudinal-mode operation in a flash-lamp-pumped Nd:YAG laser. Synchronization within 2 ns with an external short-pulse laser source was demonstrated.

  2. Dual-wavelength laser with topological charge

    NASA Astrophysics Data System (ADS)

    Yu, Haohai; Xu, Miaomiao; Zhao, Yongguang; Wang, Yicheng; Han, Shuo; Zhang, Huaijin; Wang, Zhengping; Wang, Jiyang

    2013-09-01

    We demonstrate the simultaneous oscillation of different photons with equal orbital angular momentum in solid-state lasers for the first time to our knowledge. Single tunable Hermite-Gaussian (HG0,n) (0 ≤ n ≤ 7) laser modes with dual wavelength were generated using an isotropic cavity. With a mode-converter, the corresponding Laguerre-Gaussian (LG0,n) laser modes were obtained. The oscillating laser modes have two types of photons at the wavelengths of 1077 and 1081 nm and equal orbital angular momentum of nħ per photon. These results identify the possibility of simultaneous oscillation of different photons with equal and controllable orbital angular momentum. It can be proposed that this laser should have promising applications in many fields based on its compact structure, tunable orbital angular momentum, and simultaneous oscillation of different photons with equal orbital angular momentum.

  3. Multiple acousto-optic q-switch

    DOEpatents

    Deason, Vance A.

    1993-01-01

    An improved dynamic moire interferometer comprised of a lasing medium providing a plurality of beams of coherent light, a multiple q-switch producing multiple trains of 100,000 or more pulses per second, a combining means collimating multiple trains of pulses into substantially a single train and directing beams to specimen gratings affixed to a test material, and a controller, triggering and sequencing the emission of the pulses with the occurrence and recording of a dynamic loading event.

  4. Multiple acousto-optic q-switch

    DOEpatents

    Deason, Vance A.

    1993-12-07

    An improved dynamic moire interferometer comprised of a lasing medium providing a plurality of beams of coherent light, a multiple q-switch producing multiple trains of 100,000 or more pulses per second, a combining means collimating multiple trains of pulses into substantially a single train and directing beams to specimen gratings affixed to a test material, and a controller, triggering and sequencing the emission of the pulses with the occurrence and recording of a dynamic loading event.

  5. All fiber passively Q-switched laser

    DOEpatents

    Soh, Daniel B. S.; Bisson, Scott E

    2015-05-12

    Embodiments relate to an all fiber passively Q-switched laser. The laser includes a large core doped gain fiber having a first end. The large core doped gain fiber has a first core diameter. The laser includes a doped single mode fiber (saturable absorber) having a second core diameter that is smaller than the first core diameter. The laser includes a mode transformer positioned between a second end of the large core doped gain fiber and a first end of the single mode fiber. The mode transformer has a core diameter that transitions from the first core diameter to the second core diameter and filters out light modes not supported by the doped single mode fiber. The laser includes a laser cavity formed between a first reflector positioned adjacent the large core doped gain fiber and a second reflector positioned adjacent the doped single mode fiber.

  6. Actively Q-switched Raman fiber laser

    NASA Astrophysics Data System (ADS)

    Kuznetsov, A. G.; Podivilov, E. V.; Babin, S. A.

    2015-03-01

    A new scheme providing actively Q-switched operation of a Raman fiber laser (RFL) has been proposed and tested. The RFL consists of a 1 km single-mode fiber with a switchable loop mirror at one end and an angled cleaved output end. An 1080 nm pulse with microsecond duration is generated at the output by means of acousto-optic switching of the mirror at ~30 kHz in the presence of 6 W backward pumping at 1030 nm. In the proposed scheme, the generated pulse energy is defined by the pump energy distributed along the passive fiber, which amounts to 30 μJ in our case. The available pump energy may be increased by means of fiber lengthening. Pulse shortening is also expected.

  7. Injection Seeding Of A Q-Switched Alexandrite Laser

    NASA Technical Reports Server (NTRS)

    Zukowski, Barbara J. K.; Glesne, Thomas R.; Schwemmer, Geary; Czechanski, James P.; Kay, Richard B.

    1992-01-01

    Experiment demonstrates that standing-wave, Q-switched, tunable alexandrite laser can be injection-seeded to increase stability of output frequency and significantly reduce bandwidth from 750 GHz to 180 MHz. Injecting laser acts as oscillator or master, while Q-switched laser into which ouput of seed laser injected acts as amplifier or slave.

  8. A high performance micro-dual-wavelength-spectrophotometer (MDWS).

    PubMed

    Schmidt, Werner

    2004-01-30

    The dual wavelength spectrophotometer (DWS) has proven to be the most sensitive device to monitor minute optical absorbance changes, which are inaccessible to conventional single or double beam spectrophotometers. The typical set ups, e.g. extensively used for Ca2+ or phytochrome measurements, are huge, expensive and cumbrous. Therefore, a novel high performance micro-dual-wavelength spectrophotometer (MDWS) was developed. It is miniaturized and no moving parts such as vibrational mirrors or rotating filter wheels involved. Its specifications are superior compared to the conventional set up being capable of detecting minute optical changes (reflection, absorbance, transmittance) at particular wavelengths.

  9. Thermal and laser properties of Nd:Lu₃Sc₁.₅Ga₃.₅O₁₂ for high power dual-wavelength laser.

    PubMed

    Wu, K; Hao, L Z; Yu, H H; Wang, Z P; Wang, J Y; Zhang, H J

    2012-03-26

    We measured the thermal properties of Nd:Lu₃Sc₁.₅Ga₃.₅O₁₂ (Nd:LuSGG) crystal, including the thermal expansion coefficient, specific heat, and thermal diffusion coefficient. The calculated thermal conductivity is 4.4 W/mK at room temperature. A high-power continuous-wave and passively Q-switched Nd:LuSGG laser was also demonstrated. Continuous-wave output power of 6.96 W is obtained which is the highest power with this material. For the first time to our knowledge, the passively Q-switched Nd:LuSGG laser is reported with the shortest pulse width, largest pulse energy, and highest peak power are achieved to be 5.1 ns, 62.5 μJ, and 12 kW, respectively. By spectral analysis, it has been found that the Nd:LuSGG laser was located at 1059 nm under low pump power, and became dual-wavelength at 1061.5 and 1059 nm when the incident pump power is over 2.27 W. The generating mechanism of dual-wavelength laser is also discussed.

  10. CW and passively Q-switched laser performance of Nd:Lu2SiO5 crystal

    NASA Astrophysics Data System (ADS)

    Xu, Xiaodong; Di, Juqing; Zhang, Jian; Tang, Dingyuan; Xu, Jun

    2016-01-01

    We demonstrated an efficient and controllable dual-wavelength continuous-wave (CW) laser of Nd:Lu2SiO5 (Nd:LSO) crystal. The maximum output power was 3.02 W at wavelength of 1075 nm and 1079 nm, and with increasing of absorbed pump power, the ratio of 1079 nm laser rose. The slope efficiency of 65.6% and optical-to-optical conversion efficiency of 63.3% were obtained. The passively Q-switched laser properties of Nd:LSO were investigated for the first time. The shortest pulse, maximum pulse energy and peak power were 11.58 ns, 29.05 μJ and 2.34 kW, respectively.

  11. Compact High-Repetition-Rate Monochromatic Terahertz Source Based on Difference Frequency Generation from a Dual-Wavelength Nd:YAG Laser and DAST Crystal

    NASA Astrophysics Data System (ADS)

    Zhong, Kai; Mei, Jialin; Wang, Maorong; Liu, Pengxiang; Xu, Degang; Wang, Yuye; Shi, Wei; Yao, Jianquan; Teng, Bing; Xiao, Yong

    2017-01-01

    Although high-repetition-rate dual-wavelength Nd:YAG lasers at 1319 and 1338 nm have been realized for quite a long time, we have employed it in generating monochromatic terahertz (THz) wave in this paper for the first time. The dual-wavelength laser was LD-end-pumped and acousto-optically (AO) Q-switched with the output power of watt level operating at different repetition rates from 5.5 to 30 kHz. Using a 0.6-mm-thick organic nonlinear crystal DAST for difference frequency generation (DFG), a compact terahertz source was achieved at 3.28 THz. The maximum average output power was about 0.58 μW obtained at a repetition rate of 5.5 kHz, corresponding to the conversion efficiency of about 6.4 × 10-7. The output power scaling is still feasible with higher pump power and a longer nonlinear DFG crystal. Owing to the compactness of the dual-wavelength laser and the nonlinear crystal, a palm-top terahertz source is expected for portable applications such as imaging and so on.

  12. Broadly, independent-tunable, dual-wavelength mid-infrared ultrafast optical parametric oscillator.

    PubMed

    Jin, Yuwei; Cristescu, S M; Harren, Frans J M; Mandon, Julien

    2015-08-10

    We demonstrate a two-crystal mid-infrared dual-wavelength optical parametric oscillator, synchronously pumped by a high power femtosecond Yb:fiber laser. The singly-resonant ring cavity, containing two periodically poled lithium niobate crystals, is capable of generating two synchronized idler wavelengths, independently tunable over 30 THz in the 2.9 - 4.2 μm wavelength region, due to the cascaded quadratic nonlinear effect. The independent tunability of the two idlers makes the optical parametric oscillator a promising source for ultrafast pulse generation towards the THz wavelength region, based on different frequency generation. In addition, the observed frequency doubled idler within the crystal indicates the possibility to realize a broadband optical self-phase locking between pump, signal, idler and higher order generated parametric lights.

  13. Diode-pumped actively Q-switched thulium laser

    NASA Astrophysics Data System (ADS)

    Jabczynski, J. K.; Zendzian, W.; Kwiatkowski, J.; Jelinkova, H.; Sulc, J.; Nemec, M.

    2007-06-01

    The properties of several Tm doped crystals regarding application in Q-switched tunable laser were analyzed theoretically. The acousto-optically Q-switched Tm:YLF laser is described in experimental part. The fiber coupled (0.4-mm core diameter) laser diode bar at 792-nm wavelength was deployed for pumping. The uncoated, with 3.5% dopant of thulium YLF rod of ø3x8mm size wrapped with indium foil was mounted in copper heat-sink maintaining 293 K temperature of coolant water. Above 6 W of output power and near 50% slope efficiency with respect to absorbed pump power was demonstrated in free-running mode for a short, 40-mm long resonator. The quartz acousto-optic modulator with above 80% diffraction efficiency for 25-W power of RF was taken as the Q-switch for such a laser. In the best case of Q-switching mode up to 2-mJ output energy with 15-ns pulse duration corresponding to 100-kW peak power was demonstrated for rep. rate of a few Hz. Emission wavelength was around 1904 nm for both free-running and Q-switching regimes

  14. Analysis of a dual-wavelength surface reference radar technique

    NASA Technical Reports Server (NTRS)

    Meneghini, Robert; Jones, Jeffrey A.; Gesell, Leslie H.

    1987-01-01

    The use of the single-wavelength surface reference technique (SRT), the standard dual-wavelength technique (DWT), and dual-wavelength surface reference technique (DSRT) for measuring precipitation from space is analyzed, and the results are compared. The characteristics of the three methods are described, and the surface return powers during clear air conditions are measured. It is observed that the rain rate estimates obtained with the DWT and DSRT are identical in form, and the surface reflectance can be derived from the estimates by replacing the rain reflectivity statistics with those of the backscattering cross section of the surface. The data reveal that the DSRT is more applicable than the SRT when the wavelength correlation in the backscattering cross section of the surface is high or when the mean values of the backscattering cross section at the two wavelengths are nearly equal.

  15. Linear programming phase unwrapping for dual-wavelength digital holography.

    PubMed

    Wang, Zhaomin; Jiao, Jiannan; Qu, Weijuan; Yang, Fang; Li, Hongru; Tian, Ailing; Asundi, Anand

    2017-01-20

    A linear programming phase unwrapping method in dual-wavelength digital holography is proposed and verified experimentally. The proposed method uses the square of height difference as a convergence standard and theoretically gives the boundary condition in a searching process. A simulation was performed by unwrapping step structures at different levels of Gaussian noise. As a result, our method is capable of recovering the discontinuities accurately. It is robust and straightforward. In the experiment, a microelectromechanical systems sample and a cylindrical lens were measured separately. The testing results were in good agreement with true values. Moreover, the proposed method is applicable not only in digital holography but also in other dual-wavelength interferometric techniques.

  16. Use of Dual-wavelength Radar for Snow Parameter Estimates

    NASA Technical Reports Server (NTRS)

    Liao, Liang; Meneghini, Robert; Iguchi, Toshio; Detwiler, Andrew

    2005-01-01

    Use of dual-wavelength radar, with properly chosen wavelengths, will significantly lessen the ambiguities in the retrieval of microphysical properties of hydrometeors. In this paper, a dual-wavelength algorithm is described to estimate the characteristic parameters of the snow size distributions. An analysis of the computational results, made at X and Ka bands (T-39 airborne radar) and at S and X bands (CP-2 ground-based radar), indicates that valid estimates of the median volume diameter of snow particles, D(sub 0), should be possible if one of the two wavelengths of the radar operates in the non-Rayleigh scattering region. However, the accuracy may be affected to some extent if the shape factors of the Gamma function used for describing the particle distribution are chosen far from the true values or if cloud water attenuation is significant. To examine the validity and accuracy of the dual-wavelength radar algorithms, the algorithms are applied to the data taken from the Convective and Precipitation-Electrification Experiment (CaPE) in 1991, in which the dual-wavelength airborne radar was coordinated with in situ aircraft particle observations and ground-based radar measurements. Having carefully co-registered the data obtained from the different platforms, the airborne radar-derived size distributions are then compared with the in-situ measurements and ground-based radar. Good agreement is found for these comparisons despite the uncertainties resulting from mismatches of the sample volumes among the different sensors as well as spatial and temporal offsets.

  17. Ultrafast laser-written dual-wavelength waveguide laser.

    PubMed

    Ams, Martin; Dekker, Peter; Marshall, Graham D; Withford, Michael J

    2012-03-15

    We report the performance of a dual-wavelength waveguide laser based on a phase-modulated sampled-grating architecture fabricated using the femtosecond laser direct-write technique. The waveguide laser was written in Yb-doped phosphate glass and had a narrow linewidth (<10 pm), high signal-to-noise ratio (>60 dB), 5 mW output power per channel, and wavelength separation of 10 nm.

  18. Q-switched Nd:YAG optical vortex lasers.

    PubMed

    Kim, D J; Kim, J W; Clarkson, W A

    2013-12-02

    Q-switched operation of a high-quality Nd:YAG optical vortex laser with the first order Laguerre-Gaussian mode and well-determined helical wavefronts using a fiber-based pump beam conditioning scheme is reported. A simple two-mirror resonator incorporating an acousto-optic Q-switch was employed, along with an etalon and a Brewster plate to enforce the particular helicity of the output. The laser yielded Q-switched pulses with ~250 μJ pulse energy and ~33 ns pulse duration (FWHM) at a 0.1 kHz repetition rate for 5.1 W of absorbed pump power. The handedness of the helical wavefronts was preserved regardless of the repetition rates. The prospects of further power scaling and improved laser performance are discussed.

  19. Magnetic domains driving a Q-switched laser

    PubMed Central

    Morimoto, Ryohei; Goto, Taichi; Pritchard, John; Takagi, Hiroyuki; Nakamura, Yuichi; Lim, Pang Boey; Uchida, Hironaga; Mina, Mani; Taira, Takunori; Inoue, Mitsuteru

    2016-01-01

    A 10-mm cavity length magnetooptically Q-switched Nd:GdVO4 laser was demonstrated using a single-crystalline ferrimagnetic rare-earth iron garnet film. To design the Q-switching system, the magnetic, optical, and magnetooptical properties of the garnet film were measured. The diode pumped solid-state laser cavity was constructed using a 190-μm-thick garnet film with 58% transmittance. The garnet film had maze-shaped magnetic domains, and the domain walls disappeared when a field of over 200 Oe was applied. Therefore, the polarization state of the transmitted light was modified by modulating the magnetization, and a Q-switched pulse output with a pulse width of 5 ns and peak power of 255 W was achieved in the 10-mm-long cavity. The physical limitation of the pulse width was discussed with the calculated results. PMID:27929119

  20. Magnetic domains driving a Q-switched laser

    NASA Astrophysics Data System (ADS)

    Morimoto, Ryohei; Goto, Taichi; Pritchard, John; Takagi, Hiroyuki; Nakamura, Yuichi; Lim, Pang Boey; Uchida, Hironaga; Mina, Mani; Taira, Takunori; Inoue, Mitsuteru

    2016-12-01

    A 10-mm cavity length magnetooptically Q-switched Nd:GdVO4 laser was demonstrated using a single-crystalline ferrimagnetic rare-earth iron garnet film. To design the Q-switching system, the magnetic, optical, and magnetooptical properties of the garnet film were measured. The diode pumped solid-state laser cavity was constructed using a 190-μm-thick garnet film with 58% transmittance. The garnet film had maze-shaped magnetic domains, and the domain walls disappeared when a field of over 200 Oe was applied. Therefore, the polarization state of the transmitted light was modified by modulating the magnetization, and a Q-switched pulse output with a pulse width of 5 ns and peak power of 255 W was achieved in the 10-mm-long cavity. The physical limitation of the pulse width was discussed with the calculated results.

  1. New continuous-wave and Q-switched eye-safe Nd:YAG lasers at 1.4 μm spectral region

    NASA Astrophysics Data System (ADS)

    Lan, Jinglong; Zhou, Zhiyong; Guan, Xiaofeng; Xu, Bin; Xu, Huiying; Cai, Zhiping

    2017-04-01

    We report new results concerning 1.4 μm eye-safe laser sources based on a conventional Nd:YAG crystal. In free-running laser mode, we obtain the highest output power of 4.64 W at 1413 nm with slope efficiency of about 23.1%. With the aid of an etalon, we achieve a simultaneous dual-wavelength laser at 1413 and 1443 nm with maximum output power of 3.18 W and slope efficiency of about 16.7%. In addition, a single wavelength laser at 1431 nm is also yielded with maximum output power of 1.96 W and slope efficiency of about 11.8%. The dual-wavelength laser and single-wavelength laser (1431 nm) are believed to be the first demonstrations from diode-pumped Nd:YAG crystal. Using a single-wall carbon nanotube as the saturable absorber, we achieve dual-wavelength Q-switched laser operation at 1413 and 1443 nm with the narrowest pulse width of about 0.49 μs, for the first time to our knowledge.

  2. Diode-pumped Alexandrite lasers in Q-switched and cavity-dumped Q-switched operation.

    PubMed

    Thomas, G M; Minassian, A; Sheng, X; Damzen, M J

    2016-11-28

    We present the first study of Q-switched Alexandrite lasers under continuous-wave diode-pumping with operation up to 10 kHz repetition rates in TEM00, with spatial quality M2 1.15. With a pulsed-diode dual-end-pumped design, pulse energy is scaled to a record level of 3 mJ. We also demonstrate, for the first time, cavity-dumped Q-switching of diode-pumped Alexandrite lasers under continuous-wave and pulsed diode-pumping, up to 10 kHz. Pulse energy of 510 μJ is demonstrated with 3 ns pulse duration and 170 kW peak power, in TEM00 with M2 < 1.2. Second harmonic generation of the cavity-dumped Q-switched pulses was used to generate UV wavelength 379 nm with conversion efficiency of 47%.

  3. Dual-wavelength quantum cascade laser for trace gas spectroscopy

    SciTech Connect

    Jágerská, J.; Tuzson, B.; Mangold, M.; Emmenegger, L.; Jouy, P.; Hugi, A.; Beck, M.; Faist, J.; Looser, H.

    2014-10-20

    We demonstrate a sequentially operating dual-wavelength quantum cascade laser with electrically separated laser sections, emitting single-mode at 5.25 and 6.25 μm. Based on a single waveguide ridge, this laser represents a considerable asset to optical sensing and trace gas spectroscopy, as it allows probing multiple gas species with spectrally distant absorption features using conventional optical setups without any beam combining optics. The laser capability was demonstrated in simultaneous NO and NO{sub 2} detection, reaching sub-ppb detection limits and selectivity comparable to conventional high-end spectroscopic systems.

  4. Modelling of graphene Q-switched Tm lasers

    NASA Astrophysics Data System (ADS)

    Yasukevich, A. S.; Loiko, P.; Gusakova, N. V.; Serres, J. M.; Mateos, X.; Yumashev, K. V.; Kuleshov, N. V.; Petrov, V.; Griebner, U.; Aguiló, M.; Díaz, F.

    2017-04-01

    We report on a model of diode-pumped Thulium lasers passively Q-switched by a graphene saturable absorber applicable also for any other ;fast; saturable absorber. It reasonably predicts the dependence of the pulse duration, pulse energy and pulse repetition frequency on the absorbed power. The model is applied in the present work for a Tm: KLuW microchip laser passively Q-switched with a multi-layer graphene saturable absorber. The laser generates 1 W at 1926 nm with a slope efficiency of 39%. Stable 190 ns /4.1 μJ pulses are achieved at a pulse repetition frequency of 260 kHz. The potential of graphene for the generation of few-ns pulses at 2 μm is discussed.

  5. Dual-kind Q-switching of erbium fiber laser

    SciTech Connect

    Barmenkov, Yuri O. Kir'yanov, Alexander V.; Cruz, Jose L.; Andres, Miguel V.

    2014-03-03

    Two different regimes of Q-switching in the same implementation of an actively Q-switched erbium-doped fiber laser are demonstrated. Depending on the active fiber length and repetition rate of an intracavity Q-cell (acousto-optic modulator), the laser operates either in the regime of common, rather long and low-power, pulses composed of several sub-pulses or in the one of very short and powerful stimulated Brillouin scattering-induced pulses. The basic physical reason of the laser system to oscillate in one of these two regimes is the existence or absence of CW narrow-line “bad-cavity” lasing in the intervals when the Q-cell is blocked.

  6. Efficient Q-switched Tm:YAG ceramic slab laser.

    PubMed

    Zhang, Shuaiyi; Wang, Mingjian; Xu, Lin; Wang, Yan; Tang, Yulong; Cheng, Xiaojin; Chen, Weibiao; Xu, Jianqiu; Jiang, Benxue; Pan, Yubai

    2011-01-17

    Characteristics of Tm:YAG ceramic for high efficient 2-μm lasers are analyzed. Efficient diode end-pumped continuous-wave and Q-switched Tm:YAG ceramic lasers are demonstrated. At the absorbed pump power of 53.2W, the maximum continuous wave (cw) output power of 17.2 W around 2016 nm was obtained with the output transmission of 5%. The optical conversion efficiency is 32.3%, corresponding to a slope efficiency of 36.5%. For Q-switched operation, the shortest width of 69 ns was achieved with the pulse repetition frequency of 500 Hz and single pulse energy of 20.4 mJ, which indicates excellent energy storage capability of the Tm:YAG ceramic.

  7. Graphene Q-switched Yb:KYW planar waveguide laser

    SciTech Connect

    Kim, Jun Wan; Young Choi, Sun; Jun Ahn, Kwang; Yeom, Dong-Il E-mail: rotermun@ajou.ac.kr; Rotermund, Fabian E-mail: rotermun@ajou.ac.kr; Aravazhi, Shanmugam; Pollnau, Markus; Griebner, Uwe; Petrov, Valentin; Bae, Sukang

    2015-01-15

    A diode-pumped Yb:KYW planar waveguide laser, single-mode Q-switched by evanescent-field interaction with graphene, is demonstrated for the first time. Few-layer graphene grown by chemical vapor deposition is transferred onto the top of a guiding layer, which initiates stable Q-switched operation in a 2.4-cm-long waveguide laser operating near 1027 nm. Average output powers up to 34 mW and pulse durations as short as 349 ns are achieved. The measured output beam profile, clearly exhibiting a single mode, agrees well with the theoretically calculated mode intensity distribution inside the waveguide. As the pump power is increased, the repetition rate and pulse energy increase from 191 to 607 kHz and from 7.4 to 58.6 nJ, respectively, whereas the pulse duration decreases from 2.09 μs to 349 ns.

  8. Tungsten diselenide Q-switched erbium-doped fiber laser

    NASA Astrophysics Data System (ADS)

    Chen, Bohua; Zhang, Xiaoyan; Guo, Chaoshi; Wu, Kan; Chen, Jianping; Wang, Jun

    2016-08-01

    We report a tungsten diselenide (WSe2) polyvinyl alcohol (PVA)-based, saturable absorber and related experiment results of a Q-switched fiber laser. WSe2-PVA film is synthesized by liquid phase exfoliation method, and its saturable absorption is measured via a nonlinear transmission experiment. The result shows that WSe2-PVA saturable absorber has a modulation depth of 3.5%, which means it has potential for generating an ultrafast pulse laser. We apply this absorber into a ring-cavity erbium-doped fiber laser and obtain Q-switched pulses under appropriate pump power. Our work demonstrates the reliable nonlinear optical characteristics of WSe2 and the feasibility for this two-dimensional material to be applied in the field of nonlinear optics.

  9. Modeling of a dual-wavelength pumped metastable argon laser

    NASA Astrophysics Data System (ADS)

    Gao, Jun; Sun, PengFei; Wang, XinBing; Zuo, DuLuo

    2017-03-01

    Optically pumped metastable argon laser is an attractive research topic of innovative gas lasers, but the slow collisional relaxation rates of 1s 4–1s 5 (in Paschen notation) may form a bottleneck on the cycling of active atoms and decrease the laser output at room temperature. Here, by employing a method of a dual-wavelength pump, we demonstrate the removal of accumulation on the 1s 4 level and the improvement of output power in the simulation. The simulated results show that a large increase in laser output is possible with a relatively weak assistant pump intensity. This method offers a feasible way to scale the laser to higher gain.

  10. Motion compensation for detecting glucose through dual wavelength polarimetric system

    NASA Astrophysics Data System (ADS)

    Dixon, J. B.; Wan, Qiujie; Cote, Gerard L.

    2005-03-01

    The increasing prevalence of diabetes in the United States has led many to pursue methods for non-invasive glucose detection using various optical approaches such as NIR absorption spectroscopy, Raman spectroscopy, fluorescence spectroscopy, and polarization. Polarization approaches using the aqueous humor as the sensing site have been previously shown to achieve 5 mg/dl accuracy in vitro, however accuracy in vivo has yet to be obtained due to motion induced birefringence changes in the cornea. A dual-wavelength close-looped system was developed to compensate for motion artifact. This method has shown 15 mg/dl accuracy in the presence of birefringence changes in the optical path in vitro similar to those that occur in the cornea -- something previous systems were not capable of doing.

  11. Dual-wavelength InP quantum dot lasers

    SciTech Connect

    Shutts, S.; Smowton, P. M.; Krysa, A. B.

    2014-06-16

    We have demonstrated a two-section dual-wavelength diode laser incorporating distributed Bragg reflectors, with a peak-wavelength separation of 62.5 nm at 300 K. Each lasing wavelength has a different temperature dependence, providing a difference-tuning of 0.11 nm/K. We discuss the mechanisms governing the light output of the two competing modes and explain how the short wavelength can be relatively insensitive to output changes at the longer wavelength. Starting from an initial condition when the output at both wavelengths are equal, a 500% increase in the long wavelength output causes the short wavelength output to fall by only 6%.

  12. Tunable dual-wavelength passively mode-locked thulium-doped fiber laser using carbon nanotube

    NASA Astrophysics Data System (ADS)

    Niu, Chuanning; Wang, Zhaokun; Zhang, Jiayang; Yu, Ting; Zhou, Jun; Li, Nan; Qin, Guanshi; Ning, Ding; Zhang, Fujun; Feng, Dejun

    2016-10-01

    A tunable dual-wavelength passively mode-locked thulium-doped fiber laser (TDFL) based on single-wall carbon nanotube is demonstrated. By properly tuning the pump power and the polarization controller, both single- and dual-wavelength mode-locked operation can be achieved. The repetition rates of the single- and dual-wavelength mode-locked operation are both 17.64 MHz. The duration of the ultrashort soliton pulse is about 3.7 ps. By appropriately adjusting the polarization state of the laser, the dual wavelength can be tuned from 1879.8 and 1894.5 nm to 1903.3 and 1914.1 nm.

  13. Dual-wavelength photoacoustic imaging of a photoswitchable reporter protein

    NASA Astrophysics Data System (ADS)

    Dortay, Hakan; Märk, Julia; Wagener, Asja; Zhang, Edward; Grötzinger, Carsten; Hildebrandt, Peter; Friedrich, Thomas; Laufer, Jan

    2016-03-01

    Photoacoustic (PA) imaging has been shown to provide detailed 3-D images of genetically expressed reporters, such as fluorescent proteins and tyrosinase-induced melanin. Their unambiguous detection in vivo is a vital prerequisite for molecular imaging of biological processes at a cellular and molecular level. This typically requires multiwavelength imaging and spectral unmixing techniques, which can be computationally expensive. In addition, fluorescent proteins often exhibit fluence-dependent ground state depopulation and photobleaching which can adversely affect the specificity of unmixing methods. To overcome these problems, a phytochrome-based reporter protein and a dual-wavelength excitation method have been developed to obtain reporter-specific PA contrast. Phytochromes are non-fluorescent proteins that exhibit two isomeric states with different absorption spectra. Using dual-wavelength excitation pulses in the red and near-infrared wavelength region, these states can be switched, resulting in a modulation of the total absorption coefficient, and hence the PA signal amplitude. Since this is not observed in endogenous chromophores, signals acquired using simultaneous pulses can be subtracted from the sum of signals obtained from separate pulses to provide a reporterspecific contrast mechanism and elimination of the tissue background. PA signals measured in protein solutions using separate and simultaneous excitation pulses at 670 nm and 755 nm (< 6 mJ cm-2) showed a difference in amplitude of a factor of five. Photobleaching was not observed. To demonstrate suitability for in vivo applications, mammalian cells were transduced virally to express phytochrome, and imaged in tissue phantoms and in mice in an initial preclinical study. The results show that this method has the potential to enable deep-tissue PA reporter gene imaging with high specificity.

  14. Q-Switched Alexandrite Laser-induced Chrysiasis

    PubMed Central

    Victor Ross, E.

    2015-01-01

    Background: Chyriasis is an uncommon side effect that occurs in patients who are receiving prolonged treatment with either intravenous or intramuscular gold as a distinctive blue-gray pigmentation of light-exposed skin. Laser-induced chrysiasis is a rarely described phenomenon in individuals who have received systemic gold and are subsequently treated with a Q-switched laser. Purpose: To describe the characteristics of patients with laser-induced chrysiasis. Methods: The authors describe a 60-year-old woman who developed chrysiasis at Q-switched alexandrite laser treatment sites. They also reviewed the medical literature using PubMed, searching the terms chrysiasis, gold, and laser-induced. Patient reports and previous reviews of these subjects were critically assessed and the salient features are presented. Results: Including the authors’ patient, laser-induced chrysiasis has been described in five Caucasian arthritis patients (4 women and 1 man); most of the patients had received more than 8g of systemic gold therapy during a period of 3 to 13 years. Gold therapy was still occurring or had been discontinued as long as 26 years prior to laser treatment. All of the patients immediately developed blue macules at the Q-switched laser treatment site. Resolution of the dyschromia occurred in a 70-year-old woman after two treatment sessions with a long-pulsed ruby laser and the authors’ patient after a sequential series of laser sessions using a long-pulsed alexandrite laser, followed by a nonablative fractional laser and an ablative carbon dioxide laser. Conclusion: Laser-induced chrysiasis has been observed following treatment with Q-switched lasers in patients who are receiving or have previously been treated with systemic gold. It can occur decades after treatment with gold has been discontinued. Therefore, inquiry regarding a prior history of treatment with gold—particularly in older patients with arthritis—should be considered prior to treatment with a Q-switched

  15. Influence of output coupling on the performance of a passively Q-switched Nd:YAG laser with intracavity optical parametric oscillator.

    PubMed

    Huang, Y P; Huang, Y J; Cho, C Y; Chen, Y F

    2013-03-25

    A singly-resonant intracavity optical parametric oscillator (OPO), pumped by a passively Q-switched Nd:YAG laser, is systematically investigated by means of a series of the output mirrors with various reflectivities for the fundamental wavelength at 1064 nm. Experimental results reveal that the output mirror with partial reflectivity instead of high reflection at 1064 nm not only is practicable to avoid the optical coatings damaged, but also enhances the dual-wavelength output efficiency for the OPO signal and fundamental laser waves. The overall optical-to-optical conversion efficiency is enhanced from 6.4% to 8.2% for the reflectivity decreasing from 99.8% to 90%.

  16. A non-critically phase matched KTA optical parametric oscillator intracavity pumped by an actively Q-switched Nd:GYSGG laser with dual signal wavelengths

    NASA Astrophysics Data System (ADS)

    Zhong, Kai; Guo, Shibei; Wang, Maorong; Mei, Jialin; Xu, Degang; Yao, Jianquan

    2015-06-01

    A non-critically phase matched eye-safe KTA optical parametric oscillator intracavity pumped by a dual-wavelength acousto-optically Q-switched Nd:GYSGG laser is demonstrated. Simultaneous dual signal wavelength at 1525.1 nm/1531.2 nm can be realized using only one laser crystal and one nonlinear crystal. When the absorbed diode pump power at 808 nm is 7.48 W, the maximum output power, single pulse energy and peak power are 296 mW, 2.96 μJ and 6.4 kW, respectively. As the signal wavelengths exactly locates at the absorption band of C2H2, such an Nd:GYSGG/KTA eye-safe laser has good application prospects in differential absorption lidar (DIAL) for C2H2 detection and difference frequency generation for terahertz waves at 0.77 THz.

  17. Tm:germanate Fiber Laser: Tuning And Q-switching

    NASA Technical Reports Server (NTRS)

    Barnes, Norman P.; Walsh, Brian M.; Reichle, Donald J.; DeYoung, R. J.; Jiang, Shibin

    2007-01-01

    A Tm:germanate fiber laser produced >0.25 mJ/pulse in a 45 ns pulse. It is capable of producing multiple Q-switched pulses from a single p ump pulse. With the addition of a diffraction grating, Tm:germanate f iber lasers produced a wide, but length dependent, tuning range. By s electing the fiber length, the tuning range extends from 1.88 to 2.04 ?m. These traits make Tm:germanate lasers suitable for remote sensin g of water vapor.

  18. Switchable dual-wavelength fiber laser based on PCF Sagnac loop and broadband FBG

    NASA Astrophysics Data System (ADS)

    Chen, Weiguo; Lou, Shuqin; Feng, Suchun; Wang, Liwen; Li, Honglei; Guo, Tieying; Jian, Shuisheng

    2009-11-01

    Switchable dual-wavelength fiber laser with photonic crystal fiber (PCF) Sagnac loop and broadband fiber Bragg grating (BFBG) at room temperature is demonstrated. By adjusting the polarization controller (PC) appropriately, the laser can be switched between the stable single- and dual-wavelength lasing operations by exploiting polarization hole burning (PHB) and spectral hole burning effects (SHB).

  19. Continuous 1052, 1064 nm dual-wavelength Nd:YAG laser

    NASA Astrophysics Data System (ADS)

    Wang, Xiaozhong; Yuan, Haiyang; Wang, Mingshan; Huang, Wencai

    2016-10-01

    Dual-wavelength lasers are usually obtained through balancing the net gain of the two oscillating lines. Competition between transitions 1052 nm, 1061 nm and 1064 nm is utilized to realize a continuous wave 1052 and 1064 nm dual-wavelength Nd:YAG laser firstly in this paper. A specially designed Fabry-Perot band-pass filter is exploited as output coupler to control the thresholds of the oscillating wavelengths. The maximum power of the dual-wavelength laser is 1.6 W and the slope efficiency is about 10%. The power instability of the output dual-wavelength laser is smaller than ±4% in half an hour. The mechanism presented in this paper may provide a new way to obtain dual-wavelength lasers.

  20. Experimental and theoretical study of passively Q-switched Yb:YAG laser with GaAs saturable absorber near 1050 nm

    NASA Astrophysics Data System (ADS)

    Chu, Hongwei; Zhao, Shengzhi; Yang, Kejian; Li, Yuefei; Li, Dechun; Li, Guiqiu; Zhao, Jia; Qiao, Wenchao; Xu, Xiaodong; Di, Juqing; Zheng, Lihe; Xu, Jun

    2014-03-01

    A diode-end-pumped passively Q-switched ytterbium-doped yttrium aluminum garnet (Yb:YAG) laser with gallium arsenide (GaAs) wafer as saturable absorber has been realized. In the experiment, two pieces of GaAs wafers with respective thicknesses of 400 and 700 μm were used respectively. The output laser characteristics such as the pulse duration, single pulse energy and peak power, have been measured. By using thicker GaAs wafer as saturable absorber, a minimum pulse duration of 3.5 ns was obtained with an average output power of 361 mW and a pulse repetition rate (PRR) of 25 kHz, corresponding to a single pulse energy of 19.6 μJ and a peak power of 5.7 kW. With a 400 μm-thick GaAs wafer as saturable absorber, a maximum output power of 469 mW was achieved. The central wavelength of the laser was measured to be 1050.4 nm at pump power of 7.8 W and dual wavelength operation peaked at 1049.3 nm and 1051.6 nm was observed at a high pump power of 10 W. By considering Gaussian spatial distribution and the thermal effects in the gain medium, the coupled rate equations for passively Q-switched Yb:YAG laser with GaAs saturable absorber were given.

  1. Topography and Vegetation Characterization using Dual-Wavelength Airborne Lidar

    NASA Astrophysics Data System (ADS)

    Neuenschwander, A. L.; Bradford, B.; Magruder, L. A.

    2014-12-01

    Monitoring Earth surface dynamics at an ever increasing resolution has helped to support the characterization of local topography, including vegetated and urban environments. Airborne remote sensing using light detection and ranging (LIDAR) is naturally suited to characterize vegetation and landscapes as it provides detailed three-dimensional spatial data with multiple elevation recordings for each laser pulse. The full waveform LIDAR receiver is unique in this aspect as it can capture and record the complete temporal history of the reflected signal, which contains detailed information about the structure of the objects and ground surfaces illuminated by the beam. This study examines the utility of co-collected, dual-wavelength, full waveform LIDAR data to characterize vegetation and landscapes through the extraction of waveform features, including total waveform energy, canopy energy distribution, and foliage penetration metrics. Assessments are performed using data collected in May 2014 over Monterey, CA, including the Naval Postgraduate School campus area as well as the Point Lobos State Natural Reserve situated on the Monterey coast. The surveys were performed with the Chiroptera dual-laser LIDAR mapping system from Airborne Hydrography AB (AHAB), which can collect both green (515nm) and near infrared (1064nm) waveforms simultaneously. Making use of the dual waveforms allows for detailed characterization of the vegetation and landscape not previously possible with airborne LIDAR.

  2. Repetitively Q-switched Nd:BeL lasers

    NASA Technical Reports Server (NTRS)

    Degnan, J.; Birnbaum, M.; Deshazer, L. G.

    1979-01-01

    The thermal and mechanical characteristics which will ultimately limit the performance of Nd:BeL at high average power levels were investigated. The output beam characteristics (pulse width, peak power, beam dimensions and collimation) were determined at high repetition rates for both Nd:BeL and Nd:YAG. The output of Nd:BeL was shown to exceed that of Nd:YAG by a factor of 2.7 at low Q-switched repetition rates (1 Hz). This result follows from the smaller stimulated emission cross section of x-axis Nb:BeL compared to that of NdYAG by the same factor. At high repetition rates (10 Hz) the output of Nd:Bel falls to a level of three-fifths of its low repetition rate value while under similar tests the output of Nd:YAG remains essentially constant. A comparison of the measured values of the elasto-optic coefficients, the dn/dT values and the linear expansion coefficients for BeL and YAG failed to provide an explanation for the performance of BeL; however, thermal lensing was observed in Nd:BeL. Results imply that the output of a high repetition rate Q-switched Nd:BeL laser (high thermal loading) could be dramatically increased by utilization of a resonator design to compensate for the thermal lensing effects.

  3. Simulation of tunable Cr:YSO Q-switched Cr:LiSAF laser

    NASA Astrophysics Data System (ADS)

    Chen, Hsiu-Fen; Hsieh, Shang-Wei; Kuo, Yen-Kuang

    2005-01-01

    In this work, we numerically investigate the passive Q-switching performance of the tunable Cr:YSO Q-switched Cr:LiSAF laser over its entire tuning range. Specifically, the optical performance of the Cr:YSO Q-switched Cr:LiSAF laser as functions of the initial population in the ground state of the Cr:YSO saturable absorber, the pumping rate, the reflectivity of the output coupler, and the dissipative loss inside the laser cavity are studied. Simulation results show that the Cr:YSO is an effective saturable absorber Q switch for the Cr:LiSAF laser over its entire tuning range. Unlike the Cr:YSO Q-switched alexandrite laser and the Cr:YSO Q-switched Cr:LiCAF laser, the Cr:YSO Q-switched Cr:LiSAF laser has similar passive Q-switching performance when the laser polarization is along each of the three principal axes of the Cr:YSO. The results obtained numerically in this work are in good agreement with those obtained experimentally by other researchers. Our simulation results indicate that, a Q-switched laser pulse with an output energy of 10 mJ and a pulse width of 17 ns may be obtained at 850 nm, the peak of its tuning spectrum.

  4. Inverse-Gaussian apodized fiber Bragg grating for dual-wavelength lasing.

    PubMed

    Lin, Bo; Zhang, Han; Tjin, Swee Chuan; Tang, Dingyuan; Hao, Jianzhong; Tay, Chia Meng; Liang, Sheng

    2010-03-10

    A fiber Bragg grating (FBG) with an inverse-Gaussian apodization function is proposed and fabricated. It is shown that such a FBG possesses dual-wavelength narrow transmission peaks and the wavelength spacing between the two peaks is easily controllable during fabrication. Incorporating such a FBG filter into a fiber laser with a linear cavity, we obtain stable dual-wavelength emission with 0.146 nm wavelength spacing. This arrangement provides a simple and low cost way of achieving dual-wavelength fiber laser operation.

  5. Diode-Pumped, Q-Switched, Frequency-Doubling Laser

    NASA Technical Reports Server (NTRS)

    Hemmati, Hamid; Lesh, James R.

    1993-01-01

    Experimental Q-switched, diode-pumped, intracavity-frequency-doubling laser generates pulses of radiation at wavelength of 532 nm from excitation at 810 nm. Principal innovative feature distinguishing laser from others of its type: pulsed operation of laser at pulse-repetition frequencies higher than reported previously. Folded resonator keeps most of second-harmonic radiation away from Q-switcher, laser crystal, and laser diodes. Folding mirror highly reflective at fundamental laser wavelength and highly transmissive at second-harmonic laser wavelength. By virtue of difference of about 0.6 percent between reflectivities in two polarizations at fundamental wavelength, folding mirror favors polarized oscillation at fundamental wavelength. This characteristic desirable for doubling of frequency in some intracavity crystals.

  6. Theory of the optimally coupled Q-switched laser

    NASA Technical Reports Server (NTRS)

    Degnan, John J.

    1989-01-01

    The general equations describing Q-switched laser operation are transcendental in nature and require numerical solutions, which greatly complicates the optimization of real devices. Here, it is shown that, using the mathematical technique of Lagrange multipliers, one can derive simple analytic expressions for all of the key parameters of the optimally coupled laser, i.e., one which uses an optimum reflector to obtain maximum laser efficiency for a given pump level. These parameters can all be expressed as functions of a single dimensionless variable z, defined as the ratio of the unsaturated small-signal gain to the dissipative (nonuseful) optical loss, multiplied by a few simple constants. Laser design tradeoff studies and performance projections can be accomplished quickly with the help of several graphs and a simple hand calculator. Sample calculations for a high-gain Nd:YAG and a low-gain alexandrite laser are presented as illustrations of the technique.

  7. Passively Q-switched side pumped monolithic ring laser

    NASA Technical Reports Server (NTRS)

    Li, Steven X. (Inventor)

    2012-01-01

    Disclosed herein are systems and methods for generating a side-pumped passively Q-switched non-planar ring oscillator. The method introduces a laser into a cavity of a crystal, the cavity having a round-trip path formed by a reflection at a dielectrically coated front surface, a first internal reflection at a first side surface of the crystal at a non-orthogonal angle with the front, a second internal reflection at a top surface of the crystal, and a third internal reflection at a second side surface of the crystal at a non-orthogonal angle with the front. The method side pumps the laser at the top or bottom surface with a side pump diode array beam and generates an output laser emanating at a location on the front surface. The design can include additional internal reflections to increase interaction with the side pump. Waste heat may be removed by mounting the crystal to a heatsink.

  8. Q-switching with single crystal photo-elastic modulators

    NASA Astrophysics Data System (ADS)

    Bammer, F.; Petkovsek, R.

    2010-09-01

    An overview is given about experiments with a new method for Q-switching lasers at a constant pulse repetition frequency. It uses inside the laser resonator a Single Crystal Photo-Elastic Modulator (SCPEM). This consists of one piezo-electric crystal electrically excited on a mechanical resonance frequency. In resonance mechanical stresses are induced that lead via the photo-elastic effect to a strongly modulated birefringence. Polarized light going through such an oscillating crystal will experience a significant modulation of its polarization and of transmission through a polarizer. Suitable materials should not be optically active, as it is for example the case for SiO2, and should allow the excitation of a longitudinal oscillation with an electric field perpendicular to the travelling direction of the light. Crystals of the group 3m, like LiTaO3 and LiNbO3, proved to be ideally suited for SCPEMS for the NIR- and VIS-region. For the infrared GaAs can be used. We demonstrated SCPEM-Q-switching for a Nd:YAG-fiber, a Nd:YVO4-slab- and a Nd:YAG-rod-laser with typical pulse repetition rates of 100-200kHz, pulse enhancement factors of ~100 and pulse durations ~1/100 of the period time. Typically the average power during pulsed operation is nearly the same as the cw-power, when the modulator is switched off. The most stable results were achieved up to now with the Nd:YVO4-slab-laser at 10W average power, 1.1 kW peak power, 127 kHz pulse repetition rate, and 70ns pulse durations.

  9. Q-switching with single crystal photo-elastic modulators

    NASA Astrophysics Data System (ADS)

    Bammer, F.; Petkovsek, R.

    2011-02-01

    An overview is given about experiments with a new method for Q-switching lasers at a constant pulse repetition frequency. It uses inside the laser resonator a Single Crystal Photo-Elastic Modulator (SCPEM). This consists of one piezo-electric crystal electrically excited on a mechanical resonance frequency. In resonance mechanical stresses are induced that lead via the photo-elastic effect to a strongly modulated birefringence. Polarized light going through such an oscillating crystal will experience a significant modulation of its polarization and of transmission through a polarizer. Suitable materials should not be optically active, as it is for example the case for SiO2, and should allow the excitation of a longitudinal oscillation with an electric field perpendicular to the travelling direction of the light. Crystals of the group 3m, like LiTaO3 and LiNbO3, proved to be ideally suited for SCPEMS for the NIR- and VIS-region. For the infrared GaAs can be used. We demonstrated SCPEM-Q-switching for a Nd:YAG-fiber, a Nd:YVO4-slab- and a Nd:YAG-rod-laser with typical pulse repetition rates of 100-200kHz, pulse enhancement factors of 100 and pulse durations {1/100 of the period time. Typically the average power during pulsed operation is nearly the same as the cw-power, when the modulator is switched off. The most stable results were achieved up to now with the Nd:YVO4-slab-laser at 10W average power, 1.1 kW peak power, 127 kHz pulse repetition rate, and 70ns pulse durations.

  10. Tunable Cr:YSO Q-Switched Cr:BeAl2O4 Laser: Numerical Study on Laser Performance along Three Principal Axes of the Q Switch

    NASA Astrophysics Data System (ADS)

    Kuo, Yen-Kuang; Chang, Jih-Yuan; Lin, Chia-Ching; Chen, Horng-Min

    2000-07-01

    Numerical simulation of the Cr:YSO Q-switched Cr:BeAl2O4 tunable laser is studied along the three principal axes of the Cr:YSO saturable absorber. The n1 axis has the best Q-switching performance when compared to the n2 and n3 axes. Theoretical expressions of important parameters such as the laser population inversion at various stages, the peak photon number inside the laser resonator, and the output energy and the pulsewidth of the Q-switched laser pulses are derived and used to evaluate the characteristics of the Cr:YSO Q-switched Cr:BeAl2O4 laser system.

  11. Dual Wavelength Lidar Observation of Tropical High-Altitude Cirrus Clouds During the ALBATROSS 1996 Campaign

    NASA Technical Reports Server (NTRS)

    Beyerle, G.; Schafer, J.; Neuber, R.; Schrems, O.; McDermid, I. S.

    1998-01-01

    Dual wavelength aerosol lidar observations of tropical high-altitude cirrus clouds were performed during the ALBATROSS 1996 campaign aboard the research vessel POLARSTERN on the Atlantic ocean in October-November 1996.

  12. Harnessing spectral property of dual wavelength white LED to improve vertical scanning interferometry.

    PubMed

    Chong, Wee Keat; Li, Xiang; Soh, Yeng Chai

    2013-07-01

    Unlike a conventional white light source that emits a continuous and broad spectrum of light, the dual wavelength white light emitting diode (LED) generates white light by mixing blue and yellow lights, so there are two distinct peaks in its intensity spectrum. Prior works had shown that the spectral property of the dual wavelength white LED can affect the vertical scanning interferometry negatively if the spectral effects are not compensated. In this paper, we shall examine this issue by modeling the spectral property and variation of the dual wavelength white LED, followed by investigating its effects on the interference signal of vertical scanning interferometry. Instead of compensating the spectral effects of the dual wavelength white LED, we harness its spectral property to improve the performance of a phase-based height reconstruction algorithm in vertical scanning interferometry.

  13. Dual-wavelength retinal image registration based on vessel segmentation and optic disc detection

    NASA Astrophysics Data System (ADS)

    Xian, Yong-li; Dai, Yun; Gao, Chun-ming; Du, Rui

    2016-09-01

    The dual-wavelength retinal image registration is one of the critical steps in the spectrophotometric measurements of oxygen saturation in the retinal vasculature. The dual-wavelength images (570 nm and 600 nm) are simultaneously captured by dual-wavelength retinal oximeter based on commercial fundus camera. The retinal oxygen saturation is finally measured after vessel segmentation, image registration and calculation of optical density ratio of the two images. Because the dual-wavelength images are acquired from different optical path, it is necessary to go through image registration before they are used to analyze the oxygen saturation. This paper presents a new approach to dual-wavelength retinal image registration based on vessel segmentation and optic disc detection. Firstly, the multi-scale segmentation algorithm based on the Hessian matrix is used to realize vessel segmentation. Secondly, after optic disc is detected by convergence index filter and the center of the optic disc is obtained by centriod algorithm, the translational difference between the images can be determined. The center of the optic disc is used as the center of rotation, and the registration based on mutual information can be achieved using contour and gray information of vessels through segmented image. So the rotational difference between the images can be determined too. The result shows that the algorithm can provide an accurate registration for the dual-wavelength retinal image.

  14. Method and apparatus for detection and control of prelasing in a Q-switched laser

    NASA Astrophysics Data System (ADS)

    Lockard, George E.

    1992-12-01

    The present invention detects prelasing in a Q-switch laser and terminates laser operation upon such detection. A detector senses the presence of light beyond a Q-switch and generates an appropriate electrical signal. A comparison stage circuit compares this detector signal with an established threshold value indicative of prelasing and generates a trigger signal if this detector signal exceeds this threshold value. A control stage circuit receives both this trigger value and a sampled Q-switch signal indicative of an opening of the Q-switch. The control stage circuit terminates operation of the laser if the trigger signal from the comparison stage is received while the sampled Q-switch signal is being received to avoid the effects of prelasing. Appropriate delays and timing sequencies are established.

  15. Method and apparatus for detection and control of prelasing in a Q-switched laser

    NASA Astrophysics Data System (ADS)

    Lockard, George E.

    1994-10-01

    The present invention detects prelasing in a Q-switch laser and terminates laser operation upon such detection. A detector senses the presence of light beyond a Q-switch and generates an appropriate electrical signal. A comparison stage circuit compares this detector signal with an established threshold value indicative of prelasing and generates a trigger signal if this detector signal exceeds this threshold value. A control stage circuit receives both this trigger value and a sampled Q-switch signal indicative of an opening of the Q-switch. The control stage circuit terminates operation of the laser if the trigger signal from the comparison stage is received while the sampled Q-switch signal is being received to avoid the effects of prelasing. Appropriate delays and timing sequences are established.

  16. Regulation of a pulsed random fiber laser in the Q-switched regime

    NASA Astrophysics Data System (ADS)

    Zeng, X. P.; Zhang, W. L.; Ma, R.; Yang, Z. J.; Zeng, X.; Dong, X.; Rao, Y. J.

    2016-11-01

    A random fiber laser with regulated Q-switched pulses has been proposed and realized through a half-open cavity, which is formed between a compound fiber-based optic ring resonator (ORR) and a segment of 500 m dispersion compensation fiber (DCF). The compound fiber-based ORR provides frequency filtered feedback, which together with Brillouin scattering of the DCF forms a Q-switched mechanism. As a result, Q-switched pulses are generated randomly. Nevertheless, each Q-switched event typically consists of several ordered sub-pulses with the same pulse interval thanks to resonant interferences of the compound fiber-based ORR. Compared with former reports, the shape and the interval of pulses in each Q-switch event are regulated greatly.

  17. Q-switched Nd:YAG/V:YAG monolith microlaser

    NASA Astrophysics Data System (ADS)

    Sulc, Jan; Jelinkova, Helena; Nejezchleb, Karel; Skoda, Vaclav

    2005-03-01

    A specially developed monolith crystal, which combines in one piece cooling undoped part (undoped YAG crystal), active laser part (YAG crystal doped with Nd3+ ions) and saturable absorber (YAG crystal doped with V3+ ions), was used for construction of longitudinally diode pumped Q-switched Nd:YAG laser operating at wavelength 1342 nm. The monolith consists of 4 mm long undoped part bounded to the V:YAG saturable absorber 530 μm thick which gives the initial transmission of saturable absorber 88%. The diameter of whole monolith was 5 mm. This combination of active crystal and saturable absorber allows to realize more compact resonator with the shortest cavity length of 33 mm only. The monolith was mounted in an adjustable water-cooled cupreous ring. Temperature of cooling water was in a range from 12 to 14 °C. As a pumping source the CW-operating laser diode emitting radiation at wavelength 808 nm with the maximum output power 20 W at the end of the fiber (fiber core diameter 400 &mum, numerical aperture 0.22) was used. The diode radiation was focused into the active Nd:YAG crystal by two achromatic doublet lenses with the focal length of 75 mm. The measured diameter of pumping beam focus inside the crystal was 360 μm. The resonator of the Nd:YAG laser was formed by a planar dielectric mirror with high transmission for the pumping radiation (T>98%@808nm) together with the high reflectance for the generated radiation (R=100%@1340nm), and by a concave (100mm or 146 mm) dielectric mirror serving as an output coupler. As this coupler a various dielectric reflectors (with the reflectivity from 82% up to 94%) was used with the reason to obtain the shortest giant pulse with the maximum power. As the optimal, the stable CW Q-switched output at wavelength 1342 nm with length of pulses 11 ns with repetition rate 6.4kHz and peak power 6.1kW, was obtained.

  18. Field Deployments of DWEL, A Dual-Wavelength Echidna Lidar

    NASA Astrophysics Data System (ADS)

    Howe, G.; Hewawasam, K.; Strahler, A. H.; Douglas, E. S.; Martel, J.; Cook, T.; Chakrabarti, S.; Li, Z.; Schaaf, C.; Paynter, I.; Saenz, E.; Wang, Z.; Yang, X.; Erb, A.

    2013-12-01

    We describe the construction and operation of a terrestrial scanning lidar used for automated retrieval of forest structure. The Dual Wavelength Echidna Lidar (DWEL) distinguishes between leaf hits and those of trunks and branches by using simultaneous, co-axial laser pulses at 1548 nm, where leaf water content produces strong absorption, and at 1064 nm where leaves and trunks have similar reflectances. The DWEL instrument obtains three-dimensional locations and characteristics of scattering events by using an altitudinal scan mirror on an azimuthal rotating mount along with full waveform digitization. The instrument has seen two successful field deployments: to the Sierra National Forest, California in June of 2013 and to both the Karawatha Forest Park and Brisbane Forest Park near Brisbane, Australia in July/August 2013 as part of the Terrestrial Laser Scanner International Interest Group (TLSIIG) conference. Measurements of tree leaves, branches, and trunks were successfully made. Panels of known reflectance were used to calibrate and characterize the back scattered waveforms in the field. Preliminary maximum range measurements were shown to be over 75 meters for both wavelengths. To obtain accurate waveform data, the two lasers are triggered simultaneously and each has a full-width-half-max length of less than 10 meters. The light is then collimated and expanded to a diameter of 6 mm before diverging in user-selectable optics with divergences of either 1.25- or 2.5-mrad enabling scan resolutions of 1- and 2-mrad. The durations of complete scans are approximately 164 and 41 minutes, respectively. Mirrors and dichroic filters co-align the two NIR wavelength laser beams along with a continuous-wave green marker laser. The outgoing beams are directed by a rotating 10 cm scan mirror with effective field of view of ×110 degrees attitudinally while the instrument itself rotates for an effective azimuthal field of view of 360 degrees. Optical encoders in both planes

  19. Theory of the optimally coupled Q-switched laser

    SciTech Connect

    Degnan, J.J.

    1989-02-01

    The general equations describing Q-switched laser operation are transcendental in nature and require numerical solutions. This greatly complicates the optimization of real devices. In this paper, we demonstrate that, using the mathematical technique of Lagrange multipliers, one can derive simple analytic expressions for all of the key parameters of the optimally coupled laser, i.e., one which uses an optimum reflector to obtain maximum laser efficiency for a given pump level. These parameters (which include the optimum reflectivity, output energy, extraction efficiency, pulsewidth, peak power, etc.) can all be expressed as functions of a single dimensionless variable z, defined as the ratio of the unsaturated small-signal gain to the dissipative (non-useful) optical loss, multiplied by a few simple constants. Laser design tradeoff studies and performance projections can be accomplished quickly with the help of several graphs and a simple hand calculator. Sample calculations for a high-gain Nd:YAG and a low-gain alexandrite laser are presented as illustrations of the technique.

  20. Q-switched ruby laser in cosmetic dermatology

    NASA Astrophysics Data System (ADS)

    Kopera, Daisy

    1996-12-01

    The q-switched ruby laser has shown promising results in the treatment of blue and black tattoos. The red light of the ruby laser, 694 nm wavelength, selectively absorbed by dark pigments, is converted into heat and pigments are immediately vaporized. Energy levels range between 4, 5 and 12 J/cm2. Short exposure time does not exceed the thermal relaxation time of the target structures. Thus, thermal damage of the surrounding tissue is minimal. Not only exogenous pigment as tattoo ink but also physiological pigmented structures as melanocytes, melanosome loaden keratinocytes, and melanophages are affected by this type of laser application. Therefore the ruby laser represents a new option in the treatment of a variety of benign pigmented lesions in cosmetic dermatology. The benefit of this source can be seen in efficient clearing of the lesions without scarring. As a side effect transient hypopigmentation may occur. Ruby laser treatment of melanocytic lesions cannot be recommended because unpigmented nevus cells do not absorb red light and persist unaltered. They still bear the potency of further transformation, as into malignancy.

  1. Synchronizable Q-switched, mode-locked, and cavity-dumped ruby laser for plasma diagnostics

    NASA Astrophysics Data System (ADS)

    Houtman, H.; Meyer, J.

    1985-06-01

    We report on the design and operation of an optimized version of a Q-switched, mode-locked, and cavity-dumped ruby-laser oscillator. The modulator window is much narrower than that assumed in conventional active mode-lock theory, and is shown to yield much shorter pulses than the latter in cases where the number of round trips is restricted. To allow a high-power pulse (≊1 GW) to evolve in the oscillator, and to allow simple synchronization to a (˜100 ns fixed delay) CO2 laser, a limit of 23 round trips was chosen, but similar limits may be imposed by lasers having short-gain duration as in an excimer laser. Details are given on the single spark gap switching element and Pockels cells, with an analysis of their expected switching speeds, in order to establish the effectiveness of the modulator, as compared to conventional sinusoidally driven active mode lockers. Single pulses of 50-70 mJ are reliably cavity-dumped after only 100-ns delay (23 round trips) with pulse length adjustable from 50-100 ps with ±5-ps stability. Relative timing between the main (CO2) and probe (ruby) pulses allows a measurement accuracy of ±50 ps to be attained.

  2. Investigations of morphological features of picosecond dual-wavelength laser ablation of stainless steel

    NASA Astrophysics Data System (ADS)

    Zhao, Wanqin; Wang, Wenjun; Mei, Xuesong; Jiang, Gedong; Liu, Bin

    2014-06-01

    Investigations on the morphological features of holes and grooves ablated on the surface of stainless steel using the picosecond dual-wavelength laser system with different powers combinations are presented based on the scarce researches on morphology of dual-wavelength laser ablation. The experimental results show the profiles of holes ablated by the visible beam appear V-shaped while those for the near-infrared have large openings and display U-shaped, which are independent of the ablation mechanism of ultrafast laser. For the dual-wavelength beam (a combination of visible beam and near-infrared), the holes resemble sunflower-like structures and have smoother ring patterns on the bottom. In general, the holes ablated by the dual-wavelength beam appear to have much flatter bottoms, linearly sloped side-walls and spinodal structures between the bottoms of the holes and the side-walls. Furthermore, through judiciously combining the powers of the dual-wavelength beam, high-quality grooves could be obtained with a flat worm-like structure at the bottom surface and less resolidified melt ejection edges. This study provides insight into optimizing ultrafast laser micromachining in order to obtain desired morphology.

  3. Modeling and optimization of actively Q-switched Nd-doped quasi-three-level laser

    NASA Astrophysics Data System (ADS)

    Yan, Renpeng; Yu, Xin; Li, Xudong; Chen, Deying; Gao, Jing

    2013-09-01

    The energy transfer upconversion and the ground state absorption are considered in solving the rate equations for an active Q-switched quasi-three-level laser. The dependence of output pulse characters on the laser parameters is investigated by solving the rate equations. The influence of the energy transfer upconversion on the pulsed laser performance is illustrated and discussed. By this model, the optimal parameters could be achieved for arbitrary quasi-three-level Q-switched lasers. An acousto-optical Q-switched Nd:YAG 946 nm laser is constructed and the reliability of the theoretical model is demonstrated.

  4. Fiber-laser pumped actively Q-switched Er:LuYAG laser at 1648 nm

    NASA Astrophysics Data System (ADS)

    Yang, X. F.; Wang, Y.; Zhao, T.; Zhu, H. Y.; Shen, D. Y.

    2016-02-01

    We demonstrated an acousto-optic Q-switched 1648 nm Er:LuYAG laser resonantly pumped by a cladding-pumped Er,Yb fiber laser at 1532 nm. Stable Q-switching operation was obtained with the pulse repetition rate (PRR) varying from 200 Hz to 10 kHz. At PRR of 200 Hz, the laser yielded Q-switched pulses with 3.3 mJ pulse energy and 65 ns pulse duration, corresponding to a peak power of 50.7 kW for 10.4 W of incident pump power.

  5. Passive Q-Switching of CO2 Tea Laser Using Sulfur Hexafluoride (SF6).

    DTIC Science & Technology

    1986-10-01

    SWITCHING WITH 60 CM GAS CELL 4 3 PASSIVE Q-SWITCHING WITH GRATING 5 Passive Q-Switching of CO2 TEA Laser Using Sulfur Hexafluoride I. Introduction The...a grating. The laser was then tuned to the strongest line of the 10.6 jan, 10.2 an, an, 9.6 an branches of the CO2 laser . The SF 6 gas cell pressure...lines of the 10.2 pam and 9.6 jm branches of the CO2 emission spectrum. It has also been shown that SF, can passively Q-switch the CO, TEA laser at

  6. Room-temperature dual-wavelength lasing from single-nanoribbon lateral heterostructures.

    PubMed

    Xu, Jinyou; Ma, Liang; Guo, Pengfei; Zhuang, Xiujuan; Zhu, Xiaoli; Hu, Wei; Duan, Xiangfeng; Pan, Anlian

    2012-08-01

    Nanoscale dual-wavelength lasers are attractive for their potential applications in highly integrated photonic devices. Here we report the growth of nanoribbon lateral heterostructures made of a CdS(x)Se(1-x) central region with epitaxial CdS lateral sides using a multistep thermal evaporation route with a moving source. Under laser excitation, the emission of these ribbons indicates sandwich-like structures along the width direction, with characteristic red emission in the center and green emission at both edges. More importantly, dual-wavelength lasing with tunable wavelengths is demonstrated at room temperature based on these single-nanoribbon heterostructures for the first time. These achievements represent a significant advance in designing nanoscale dual-wavelength lasers and have the potential to open up new and exciting opportunities for diverse applications in integrated photonics, optoelectronics, and sensing.

  7. Oscillatory phenomena and Q switching in a model for laser with a saturable absorber

    SciTech Connect

    Antoranz, J.C.; Gea, J.; Velarde, M.G.

    1981-12-28

    Sufficiently long population decay times and sufficiently short dipole decay times in a single-mode laser with saturable absorber permit passive Q switching in the form of a hard-mode sustained relaxation oscillation.

  8. Experimental study of electro-optical Q-switched pulsed Nd:YAG laser

    NASA Astrophysics Data System (ADS)

    A, Maleki; M Kavosh, Tehrani; H, Saghafifar; M, H. Moghtader Dindarlu

    2016-03-01

    We report the specification of a compact and stable side diode-pumped Q-switched pulsed Nd:YAG laser. We experimentally study and compare the performance of the pulsed Nd:YAG laser in the free-running and Q-switched modes at different pulse repetition rates from 1 Hz to 100 Hz. The laser output energy is stabilized by using a special configuration of the optical resonator. In this laser, an unsymmetrical concave-concave resonator is used and this structure helps the mode volume to be nearly fixed when the pulse repetition rate is increased. According to the experimental results in the Q-switched operation, the laser output energy is nearly constant around 70 mJ with an FWHM pulse width of 7 ns at 100 Hz. The optical-to-optical conversion efficiency in the Q-switched regime is 17.5%.

  9. Stable dual-wavelength microlaser controlled by the output mirror tilt angle

    NASA Astrophysics Data System (ADS)

    Pallas, Florent; Herault, Emilie; Zhou, Jie; Roux, Jean-Francois; Vitrant, Guy

    2011-12-01

    A continuous-wave dual-wavelength solid-state microlaser is presented and a technique for regulating the gain competition between the two wavelengths is proposed, based on the angular tilt of the laser cavity output mirror. Laser behavior is studied and balanced dual-wavelength emission is obtained with output power levels as high as 200 mW for 2 W pump power. Sum frequency mixing is demonstrated making the source promising for Terahertz generation in the 0.5-0.7 THz range through difference frequency generation.

  10. Dual Wavelength High Power Double-Clad Ytterbium-Doped Fiber Laser

    NASA Astrophysics Data System (ADS)

    Moghaddam, M. R. A.; Harun, S. W.; Shahi, S.; Ahmad, H.

    A dual wavelength high power double-clad erbium/ytterbium-doped fiber laser with a narrowest spacing of 0.4 nm and a M2 value of close to unity is presented in the region of 1565 nm. This result can be realized with a significant improvement of the mode competition problem using a loop mirror as a comb filter. The wavelength region can also be varied using polarization controllers in the loop mirror. This dual-wavelength fiber laser with side mode suppression ratio (SMSR) of 40 dB is quite stable, and the output power variance is as low as 0.46 dB.

  11. Repetitive modulation and passive Q-switching of diode end-pumped Nd-KGW laser

    NASA Astrophysics Data System (ADS)

    Kalisky, Yehoshua Y.; Kravchik, Leonid; Waichman, Karol; Labbe, Christophe

    2001-05-01

    We report the operation of a passively Q-switched diode end pumped Nd3+:KGW laser, which was obtained by using a Cr4+:YAG or Cr4+:GGG saturable absorbers in the multi-kHz frequency domain. The free-running (with maximum slope efficiency of 46%), and the passively Q-switched characteristics of Nd:KGW were investigated and the use of Nd:KGW as microlasers will be discussed.

  12. One joule per Q-switched pulse diode-pumped laser

    NASA Technical Reports Server (NTRS)

    Holder, Lonnie E.; Kennedy, Chandler; Long, Larry; Dube, George

    1992-01-01

    Q-switched 1-J output has been achieved from diode-pumped zig-zag Nd:YAG slabs in an oscillator-amplifier configuration. The oscillator was single transverse and longitudinal model. This laser set records for Q-switched energy per pulse, and for average power from a diode-pumped laser. The laser was constructed in a rugged configuration suitable for routine laboratory use.

  13. Low Fluence Q-Switched Nd: YAG Laser Toning and Q-Switched Ruby Laser in the Treatment of Melasma:A Comparative Split-Face Ultrastructural Study

    PubMed Central

    Yamashita, Rie; Kawana, Seiji; Sato, Shigeru; Naito, Zenya

    2012-01-01

    Background: Melasma still presents as a difficult entity to treat, especially in the Asian skin phe-notype. Recently laser toning with the Q-switched Nd:YAG has attracted attention. The present study investigated the efficacy of Q-switched Nd:YAG laser toning for melasma, with a histopathological comparison with the Q-switched ruby laser. Subjects and Methods: Eight Japanese females (41–57 yr, mean 52.5 yr) with Fitzpatrick skin type III and bilateral melasma participated in the study. One half of each subject's face (randomly chosen) was treated with Q-switched 1064 nm Nd:YAG laser toning (pulse width 5–20 ns; spot size, 6 mm diameter; fluence, 3.0 J/cm2, 5–7 passes, once/week, 4 weeks: QS:YAG group), and the contralateral half with a single treatment using a Q-switched ruby laser (694.5 nm, pulse width 20 ns, spot size 4 mm diameter; fluence 4.0 J/cm2, 1 pass with approximately 20% overlap: QS:Ruby group). Skin biopsies were taken immediately after the 4th Nd:YAG session and the single ruby session, and histopathological comparison was performed with light- and transmission electron microscopy (TEM). Results: Improvement in melasma pigmentation was seen in both the QS:YAG- and QS:Ruby-treat-ed sides, and this was well-maintained in the QS:YAG group. Ultrastructurally, melanin granules were destroyed in both groups, but there was considerably more morphological epidermal and dermal damage in the QS:Ruby specimens compared with minimal epidermal disruption and cellular damage in the QS:YAG specimens. Conclusions: Q-switched 1064 nm Nd:YAG laser toning offered superior results in the treatment of melasma in the Japanese skin type compared with the Q-switched ruby laser, both ultrastructurally with less immediately post-treatment cellular damage and macroscopically, and a longer recurrence-free interval. PMID:24610976

  14. Studies on output characteristics of stable dual-wavelength ytterbium-doped photonic crystal fiber laser

    NASA Astrophysics Data System (ADS)

    Tian, Hongchun; Zhang, Sa; Hou, Zhiyun; Xia, Changming; Zhou, Guiyao; Zhang, Wei; Liu, Jiantao; Wu, Jiale; Fu, Jian

    2016-06-01

    A stable dual-wavelength ytterbium-doped photonic crystal fiber laser pumped by a 976 nm laser diode has been demonstrated at room temperature. Single-wavelength, dual-wavelength laser oscillations are observed when the fiber laser operates under different pump power by using different length of fibers. Stable dual-wavelength radiation around 1045 nm and 1075 nm has been generated simultaneously at a high pump power directly from an ytterbium-doped fiber laser without using any spectral control mechanism. A small core ytterbium-doped PCF fabricated by the powder sinter direction drawn rod technology is used as gain medium. The pump power and fiber length which can affect the output characteristics of dual-wavelength fiber laser are analyzed in the experiment. Experiments confirm that higher pump power and longer fiber length favors 1075 nm output; lower pump power and shorter fiber length favors 1045 nm output. Those results have a good reference in multi-wavelength fiber laser.

  15. Real-time, closed-loop dual-wavelength optical polarimetry for glucose monitoring

    PubMed Central

    Malik, Bilal H.; Coté, Gerard L.

    2010-01-01

    The development of a real-time, dual-wavelength optical polarimetric system to ultimately probe the aqueous humor glucose concentrations as a means of noninvasive diabetic glucose monitoring is the long-term goal of this research. The key impact of the work is the development of an approach for the reduction of the time-variant corneal birefringence due to motion artifact, which is still a limiting factor preventing the realization of such a device. Our dual-wavelength approach utilizes real-time, closed-loop feedback that employs a classical three-term feedback controller and efficiently reduces the effect of motion artifact that appears as a common noise source for both wavelengths. In vitro results are shown for the open-loop system, and although the dual-wavelength system helps to reduce the noise, it is shown that closed-loop control is necessary to bring the noise down to a sufficient level for physiological monitoring. Specifically, in vitro measurement results with the closed-loop dual-wavelength approach demonstrate a sensitivity of 12.8 mg∕dl across the physiologic glucose range in the presence of time-variant test cell birefringence. Overall, it is shown that this polarimetric system has the potential to be used as a noninvasive measure of glucose for diabetes. PMID:20210476

  16. Repetitive modulation and passively Q-switching of diode-pumped Nd-KGW laser

    NASA Astrophysics Data System (ADS)

    Kalisky, Y.; Kravchik, L.; Labbe, C.

    2001-03-01

    We report the operation of a passively Q-switched diode end pumped Nd 3+:KGW laser. Passive Q-switching operation was obtained by using a Cr 4+:YAG or Cr 4+:GGG as saturable absorbers. The free-running and the passively Q-switched characteristics of Nd:KGW were investigated and analyzed. At a free-running mode, a maximum slope efficiency of 46%, and an absorbed pumping threshold of 380 mW were obtained for 4.1 at.% doping level, with 1.5-W maximum output power at 3.60-W absorbed pumping power. The Nd:KGW laser beam quality exhibited a TEM 00 with M2=1.6. The laser parameters were further analyzed as a function of the crystal heat sink temperature and the pump wavelengths. A passive Q-switched laser has been designed and operated, with a variety of Cr 4+ doped garnets employed as saturable absorbers. The laser produced modulated output in the multi-kHz frequency domain. The pulse width and the modulation frequency dependence of the passively Q-switched, repetitively modulated laser output vs. the diode pump power for Nd:KGW crystals, provides the conditions needed to enhance the modulation frequency and the peak power of diode-pumped Nd:KGW laser.

  17. High-power thulium fiber laser Q switched with single-layer graphene.

    PubMed

    Tang, Yulong; Yu, Xuechao; Li, Xiaohui; Yan, Zhiyu; Wang, Qi Jie

    2014-02-01

    We report high-power 2 μm Tm3+ fiber lasers passively Q switched by double-piece single-layer graphene transferred onto a glass plate. Through manipulating intracavity laser beam size and increasing pump ratios, an average power of 5.2 W is directly achieved from the laser oscillator with an optical-to-optical slope efficiency of 26%. The laser pulse energy can be as high as ∼18  μJ, comparable to that from actively Q-switched fiber lasers. The narrowest pulse width is 320 ns, and the pulse repetition rate can be tuned from tens of kilohertz to 280 kHz by changing the pump power. To the best of our knowledge, this is the highest average power and pulse energy, as well as the narrowest pulse width, from graphene-based Q-switched 2 μm fiber lasers.

  18. Q-switched all-fiber laser based on magnetostriction modulation of a Bragg grating.

    PubMed

    Pérez-Millán, P; Díez, A; Andrés, M; Zalvidea, D; Duchowicz, R

    2005-06-27

    We report an actively Q-switched all-fiber laser based on magnetostriction modulation of a Bragg grating. The laser employs a pair of Bragg gratings as reflective mirrors, one of which is bonded to a magnetostrictive element. Lengthening of the magnetostrictive element when a magnetic field is applied shifts the Bragg wavelength of the grating, allowing control of the Q-factor of the cavity and, thus, performing active Q-switching. The magnetostrictive modulator is small, compact and requires less than 300 mW electrical drive power. Using erbium-doped fiber and a maximum pump power of 120 mW, Q-switch pulses of more than 1 W peak power were obtained, with a pulse repetition rate that can be continuously varied from 1 Hz to 125 kHz.

  19. High power VCSEL array pumped Q-switched Nd:YAG lasers

    NASA Astrophysics Data System (ADS)

    Xiong, Yihan; Van Leeuwen, Robert; Watkins, Laurence S.; Seurin, Jean-Francois; Xu, Guoyang; Miglo, Alexander; Wang, Qing; Ghosh, Chuni

    2012-03-01

    Solid-state lasers pumped by high-power two-dimensional arrays of vertical-cavity surface-emitting lasers (VCSELs) were investigated. Both end-pumping and side-pumping schemes of Nd:YAG lasers with high power kW-class 808 nm VCSEL pump modules were implemented. For one application 10 mJ blue laser pulses were obtained from a frequencydoubled actively Q-switched VCSEL-array dual side-pumped Nd:YAG laser operating at 946 nm. For another application 10 mJ green laser pulses were obtained from a frequency-doubled passively Q-switched VCSEL-array endpumped Nd:YAG laser operating at 1064 nm. Both QCW and CW pumping schemes were investigated to achieve high average Q-switched power.

  20. Doubly active Q switching and mode locking of an all-fiber laser.

    PubMed

    Cuadrado-Laborde, Christian; Díez, Antonio; Cruz, Jose L; Andrés, Miguel V

    2009-09-15

    Simultaneous and independent active Q switching and active mode locking of an erbium-doped fiber laser is demonstrated using all-fiber modulation techniques. A magnetostrictive rod attached to the output fiber Bragg grating modulates the Q factor of the Fabry-Perot cavity, whereas active mode locking is achieved by amplitude modulation with a Bragg-grating-based acousto-optic device. Fully modulated Q-switched mode-locked trains of optical pulses were obtained for a wide range of pump powers and repetition rates. For a Q-switched repetition rate of 500 Hz and a pump power of 100 mW, the laser generates trains of 12-14 mode-locked pulses of about 1 ns each, within an envelope of 550 ns, an overall energy of 0.65 microJ, and a peak power higher than 250 W for the central pulses of the train.

  1. Injection-seeded operation of a Q-switched Cr,Tm,Ho:YAG laser

    NASA Technical Reports Server (NTRS)

    Henderson, Sammy W.; Hale, Charley P.; Magee, James R.

    1991-01-01

    Single-frequency Tm,Ho:YAG lasers operating near 2 microns are attractive sources for several applications including eye-safe laser radar (lidar) and pumping of AgGaSe2 parametric oscillators for efficient generation of longer wavelengths. As part of a program to develop a coherent lidar system using Tm,Ho:YAG lasers, a diode laser-pumped tunable CW single-longitudinal-mode (SLM) Cr:Tm:Ho:YAG laser and a flashlamp-pumped single-transverse-mode Q-switched Cr,Tm,Ho:YAG laser were developed. The CW laser was used to injection-seed the flashlamp-pumped laser, resulting in SLM Q-switched output. Operational characteristics of the CW and Q-switched lasers and injection-seeding results are reported.

  2. Passive Q-switching of Yb bulk lasers by a graphene saturable absorber

    NASA Astrophysics Data System (ADS)

    Loiko, P. A.; Serres, J. M.; Mateos, X.; Liu, J.; Zhang, H.; Yasukevich, A. S.; Yumashev, K. V.; Petrov, V.; Griebner, U.; Aguiló, M.; Díaz, F.

    2016-04-01

    Compact Yb:KLu(WO4)2 and Yb:LuVO4 lasers diode-pumped at 978 nm are passively Q-switched by a single-layer graphene saturable absorber. The Yb:KLu(WO4)2 laser generated 165 ns/0.49 μJ pulses at 1030 nm with 170 mW average output power and 12 % slope efficiency. With the Yb:LuVO4 laser, 152 ns/0.83 μJ pulses were achieved. The output power reached 300 mW at 1024 nm, and the slope efficiency was 10 %. Laser operation in a plano-plano cavity is achieved with both crystals with thermal lensing playing a key role in their performance. A model describing graphene Q-switched Yb lasers is developed. Our results indicate the potential of graphene for passive Q-switching of ~1 μm bulk lasers.

  3. Erbium-doped CW and Q-switched fiber ring laser with fiber grating Michelson interferometer

    NASA Astrophysics Data System (ADS)

    Wang, Anting; Ming, Hai; Xie, Jianping; Xu, Lixin; Huang, Wencai; Lv, Liang; Chen, Xiyao; Li, Feng; Wu, Yunxia; Xing, Meishu

    2003-01-01

    The band-pass characteristic of fiber grating Michelson interferometer is analyzed, which acts as both band-pass filter and Q-switch. An erbium-doped fiber ring laser based on fiber grating Michelson interferometer is implemented for producing single longitudinal mode CW operation with 5 MHz spectral linewidth and up to 6 mW output power. In Q-switched operation, stable fiber laser output pulses with repetition rate of 800 Hz, pulse width of 0.6 ?s, average power of 1.8 mW and peak power of 3.4 W are demonstrated. The peak power and average power of the Q-switched pulses are varied with the repetitionrate.

  4. Theoretical and experimental analysis of injection seeding a Q-switched alexandrite laser

    NASA Technical Reports Server (NTRS)

    Prasad, C. R.; Lee, H. S.; Glesne, T. R.; Monosmith, B.; Schwemmer, G. K.

    1991-01-01

    Injection seeding is a method for achieving linewidths of less than 500 MHz in the output of broadband, tunable, solid state lasers. Dye lasers, CW and pulsed diode lasers, and other solid state lasers have been used as injection seeders. By optimizing the fundamental laser parameters of pump energy, Q-switched pulse build-up time, injection seed power and mode matching, one can achieve significant improvements in the spectral purity of the Q-switched output. These parameters are incorporated into a simple model for analyzing spectral purity and pulse build-up processes in a Q-switched, injection-seeded laser. Experiments to optimize the relevant parameters of an alexandrite laser show good agreement.

  5. Graphene Q-switched Ho(3+)-doped ZBLAN fiber laser at 1190  nm.

    PubMed

    Liu, Shujing; Zhu, Xiushan; Zhu, Gongwen; Balakrishnan, Kaushik; Zong, Jie; Wiersma, Kort; Chavez-Pirson, Arturo; Norwood, R A; Peyghambarian, N

    2015-01-15

    We report Q-switched pulse operation of holmium (Ho(3+))-doped ZrF(4)-BaF(2)-LaF(3)-AlF(3)-NaF (ZBLAN) at ∼1190  nm in an all-fiber ring laser by using a fiber-optic graphene saturable absorber, which was fabricated by depositing graphene onto the flat surface of a side-polished D-shaped fiber. Stable Q-switched operation was established at a pump power of 180 mW with a repetition rate of 24 kHz and pulse width of 5.7 μs. When the pump power was increased to 1125 mW, 0.44 μJ Q-switched pulses with a repetition rate of 111 kHz and a pulse width of 0.8 μs were generated.

  6. Efficient use of Q-switched lasers in the treatment of cutaneous lesions

    NASA Astrophysics Data System (ADS)

    Hu, Xin-Hua

    1995-05-01

    The use of Q-switched laser has been well documented in the treatment of pigmented lesions, particularly in the tattoo removal. To better understand the ablation process by Q-switched lasers, we carried out an analysis on the states and other physical properties of certain tissue/pigment under the action of a strong transient electric field associated with the high energy nanosecond laser pulses. The dependence of the ablation threshold of transient electric field on the chromophore absorption has been found to be weak. A plasma ablation model is used to interpret previous experimental results. The comparison of the plasma model with the conventional selective photothermolysis model has led to a new design concept of Q-switched lasers for dermatology surgery.

  7. Passively Q-Switched Yb:YAG Laser with Cr(4+):YAG as the Saturable Absorber.

    PubMed

    Dong, J; Deng, P; Liu, Y; Zhang, Y; Xu, J; Chen, W; Xie, X

    2001-08-20

    By using a continuous-wave Ti:sapphire laser as a pumping source, we demonstrated a passively Q-switched Yb:YAG laser at room temperature with Cr(4+):YAG as the saturable absorber. We achieved an average output power of as much as 55 mW at 1.03 mum with a pulse width (FWHM) as short as 350 ns. The initial transmission of the Cr(4+):YAG has an effect on the pulse duration (FWHM) and the repetition rate of the Yb:YAG passively Q-switched laser. The Yb:YAG crystal can be a most promising passively Q-switched laser crystal for compact, efficient, solid-state lasers.

  8. Graphene Q-switched Tm:KY(WO4)2 waveguide laser

    NASA Astrophysics Data System (ADS)

    Kifle, E.; Mateos, X.; Loiko, P.; Yumashev, K.; Yasukevich, A.; Petrov, V.; Griebner, U.; Aguiló, M.; Díaz, F.

    2017-04-01

    We report on the first Tm3+-doped double tungstate waveguide laser passively Q-switched by a graphene saturable absorber using a 12.4 µm-thick 3 at.% Tm:KY0.58Gd0.22Lu0.17(WO4)2 epitaxial layer grown on a (0 1 0)-oriented pure KY(WO4)2 substrate. This laser generated 5.8 nJ/195 ns pulses at 1831.8 nm corresponding to a pulse repetition frequency of 1.13 MHz. These are the shortest pulses achieved in passively Q-switched Tm waveguide lasers. The laser slope efficiency was 9% and the Q-switching conversion efficiency reached 45%. Graphene is promising for the generation of ns pulses at ~2 µm in Tm3+-doped double tungstate waveguide lasers operating in the MHz-range.

  9. Tungsten disulphide based all fiber Q-switching cylindrical-vector beam generation

    SciTech Connect

    Lin, J.; Yan, K.; Zhou, Y.; Xu, L. X. Gu, C.; Zhan, Q. W.

    2015-11-09

    We proposed and demonstrated an all fiber passively Q-switching laser to generate cylindrical-vector beam, a two dimensional material, tungsten disulphide (WS{sub 2}), was adopted as a saturable absorber inside the laser cavity, while a few-mode fiber Bragg grating was used as a transverse mode-selective output coupler. The repetition rate of the Q-switching output pulses can be varied from 80 kHz to 120 kHz with a shortest duration of 958 ns. Attributed to the high damage threshold and polarization insensitivity of the WS{sub 2} based saturable absorber, the radially polarized beam and azimuthally polarized beam can be easily generated in the Q-switching fiber laser.

  10. Simultaneous Q-switching and mode-locking in the CW Nd:YAG laser

    NASA Technical Reports Server (NTRS)

    Kuizenga, D. J.; Phillion, D. W.; Siegman, A. E.; Lund, T.

    1973-01-01

    The theory of transient mode-locking for an active modulator in a laser with a homogeneously broadened line is presented. The theory is applied to simultaneously Q-switched and mode-locked Nd:YAG lasers and good agreement between theory and experiment is obtained. The main conclusion is that under usual Q-switched operating conditions the mode-locking process does not have sufficient time to build up to steady-state conditions. We also present a method to overcome this problem by allowing the laser to prelase before the Q-switch is opened. Mode-locked pulses whose width approaches the steady-state value are obtained. The transient mode-locking theory presented here also applies to actively mode-locking TEA CO2 lasers and to other types of simultaneously pulsed and mode-locked lasers.

  11. Ocular dynamics and visual tracking performance after Q-switched laser exposure

    NASA Astrophysics Data System (ADS)

    Zwick, Harry; Stuck, Bruce E.; Lund, David J.; Nawim, Maqsood

    2001-05-01

    In previous investigations of q-switched laser retinal exposure in awake task oriented non-human primates (NHPs), the threshold for retinal damage occurred well below that of the threshold for permanent visual function loss. Visual function measures used in these studies involved measures of visual acuity and contrast sensitivity. In the present study, we examine the same relationship for q-switched laser exposure using a visual performance task, where task dependency involves more parafoveal than foveal retina. NHPs were trained on a visual pursuit motor tracking performance task that required maintaining a small HeNe laser spot (0.3 degrees) centered in a slowly moving (0.5deg/sec) annulus. When NHPs reliably produced visual target tracking efficiencies > 80%, single q-switched laser exposures (7 nsec) were made coaxially with the line of sight of the moving target. An infrared camera imaged the pupil during exposure to obtain the pupillary response to the laser flash. Retinal images were obtained with a scanning laser ophthalmoscope 3 days post exposure under ketamine and nembutol anesthesia. Q-switched visible laser exposures at twice the damage threshold produced small (about 50mm) retinal lesions temporal to the fovea; deficits in NHP visual pursuit tracking were transient, demonstrating full recovery to baseline within a single tracking session. Post exposure analysis of the pupillary response demonstrated that the exposure flash entered the pupil, followed by 90 msec refractory period and than a 12 % pupillary contraction within 1.5 sec from the onset of laser exposure. At 6 times the morphological threshold damage level for 532 nm q-switched exposure, longer term losses in NHP pursuit tracking performance were observed. In summary, q-switched laser exposure appears to have a higher threshold for permanent visual performance loss than the corresponding threshold to produce retinal threshold injury. Mechanisms of neural plasticity within the retina and at

  12. Passive Q-switched cw diode-pumped Nd-doped YAG and YVO4 lasers

    NASA Astrophysics Data System (ADS)

    Kalisky, Yehoshua Y.; Levy, Shuki; Kravchik, Leonid

    1999-05-01

    CW diode pumped solid state lasers have sought for various scientific, medical and military applications, where compact reliable, stable, and highly efficient sources are desirable. There are several applications such as fiber- optic sensing or range finding which require short bursts of high peak power densities at multi-kilohertz repetition rates, and with a good beam quality. An extensive research on the properties of passively Q-switched, CW diode-pumped, ND-lasers has been conducted. We have used various pumping schemes to diode pump the Q-switched Nd:YAG and Nd:YVO4 laser crystals. Such schemes are transverse pumping by a cylindrical microlens-coupled diode array or longitudinally pumping by a fiber-coupled diode array. The passive Q- switching elements were Cr4+:YAG (polished, uncoated) and Cr4+:GGG (polished, coated), which were inserted inside the laser resonator. The 1.06 micrometers laser emission shows a repetitive modulation in the kHz frequency domain, and temporal bandwidth, full width at half maximum, in the range of 50 - 600 nsec. The modulation frequency and bandwidth depend on the characteristics of the Q-switching material (e.g. Cr4+ concentration, sample thickness) and on the input power level of the diode array used. We shall report design parameters and performance of various types of passively Q-switched and free-running diode pumped Nd-lasers. We shall present and discuss methods to increase the efficiency of Q-switched solid state lasers.

  13. A diode-pumped Nd:YAlO3 dual-wavelength yellow light source

    NASA Astrophysics Data System (ADS)

    Zhang, Jing; Fu, Xihong; Zhai, Pei; Xia, Jing; Li, Shutao

    2013-11-01

    We present what is, to the best of our knowledge, the first diode-pumped Nd:YAlO3 (Nd:YAP) continuous-wave (cw) dual-wavelength yellow laser at 593 nm and 598 nm, based on sum-frequency generation between 1064 and 1339 nm in a-axis polarization using LBO crystal and between 1079 and 1341 nm in c-axis polarization using PPKTP crystal, respectively. At an incident pump power of 17.3 W, the maximum output power obtained at 593 nm and 598 nm is 0.18 W and 1.86 W, respectively. The laser experiment shows that Nd:YAP crystal can be used for an efficient diode-pumped dual-wavelength yellow laser system.

  14. Dual-wavelength passively mode-locked Nd:LuYSiO5 laser with SESAM.

    PubMed

    Cong, Zhenhua; Tang, Dingyuan; De Tan, Wei; Zhang, Jian; Xu, Changwen; Luo, Dewei; Xu, Xiaodong; Li, Dongzhen; Xu, Jun; Zhang, Xingyu; Wang, Qingpu

    2011-02-28

    A diode-end-pumped dual-wavelength mode-locked laser based on Nd:LuYSiO5 crystal is demonstrated. With a SESAM, simultaneous mode locking at the 1075.8 nm and 1078.1 nm is achieved and the dual-wavelength mode locked pulses have a pulse width of 8.9 ps. Due to frequency beating, ultrahigh repetition rate ultrafast pulses with 997 fs pulse width and 0.59 THz repetition rate are further formed. Under 12.7 W absorbed pump power 1.7 W mode-locked output power was obtained, the slope efficiency of the mode locked laser was 24.3%.

  15. Single- and dual-wavelength switchable linear polarized Yb(3+)-doped double-clad fiber laser.

    PubMed

    Liu, Guanxiu; Feng, Dejun

    2015-05-10

    A single- and dual-wavelength switchable linear polarized Yb-doped double-clad fiber laser is proposed, in which the resonance cavity was composed of a fiber Bragg grating fabricated in a polarization-maintaining fiber and a dichromatic mirror with high reflectivity. The polarization hole burning is enhanced through selective polarization feedback by the polarization-maintaining fiber Bragg grating. The switchover of single and dual wavelengths is realized by tuning the rotation angle of a cubic polarization beam splitter that is inserted between the dichromatic mirror and the collimator in the cavity. The laser features wavelengths of 1070.08 and 1070.39 nm, output power of 1.0 W, signal to noise ratio of 45 dB, and slope efficiency of 34%, as well as a very narrow linewidth of 0.022 nm. The polarization characteristics are analyzed by measuring the laser power transmitted through a Glan-Thomson polarizer during rotation.

  16. Novel spectrophotometric method for selective determination of compounds in ternary mixtures (dual wavelength in ratio spectra).

    PubMed

    Saad, Ahmed S

    2015-08-05

    A simple selective spectrophotometric method for determination of compounds in ternary mixture was developed by combining the resolution power of two well-known methods that are commonly used for binary mixtures; namely ratio difference method and dual wavelength. The new method (dual wavelength in ratio spectra) was successfully applied for the determination of a ternary mixture of betamethasone dipropionate (BM), clotrimazole (CT) and benzyl alcohol (BA) in pure powder form and in their pharmaceutical preparation. The difference in amplitudes (ΔP) in the ratio spectra at 252.0 and 258.0 nm (ΔP(252.0-258.0 nm)) corresponds to BM, while ΔP(266.8-255.4 nm) and ΔP(254.2-243.5 nm) corresponds to CT and BA, respectively. The method was validated as per the USP 2005 guidelines. The developed method can be used in quality control laboratories for routine analysis of compounds in ternary mixtures.

  17. LASERS Dual-wavelength laser diodes based on epitaxially stacked heterostructures

    NASA Astrophysics Data System (ADS)

    Davydova, Evgeniya I.; Konyaev, V. P.; Ladugin, M. A.; Lebedeva, E. I.; Marmalyuk, Aleksandr A.; Padalitsa, A. A.; Petrov, S. V.; Sapozhnikov, S. M.; Simakov, V. A.; Uspenskii, Mikhail B.; Yarotskaya, I. V.

    2010-10-01

    AlGaAs/GaAs double laser heterostructures containing two different active regions have been grown by metalorganic vapour phase epitaxy in a single growth process, and their properties have been studied. A typical slope of their power — current curves is 2.3 W A-1, which is almost twice that for a laser diode (1.2 W A-1). We demonstrate lasing of the emitter regions of the dual-wavelength lasers in the range 800 — 815 nm, with a separation between the peaks of ~7 nm. The observed effect of pump current on the lasing wavelength of the active regions in the dual-wavelength and single lasers indicates that the emitter region farther away from the heat sink is more sensitive to pump current variations.

  18. Dual-wavelength tunable fibre laser with a 15-dBm peak power

    SciTech Connect

    Latif, A A; Awang, N A; Zulkifli, M Z; Harun, S W; Ghani, Z A; Ahmad, H

    2011-08-31

    A high-power dual-wavelength tunable fibre laser (HP-DWTFL) operating in the C-band at wavelengths from 1536.7 nm to 1548.6 nm is proposed and demonstrated. The HP-DWTFL utilises an arrayed waveguide grating (AWG) (1 x 16 channels) and is capable of generating eight different dual-wavelength pairs with eight possible wavelength spacings ranging from 0.8 nm (the narrowest spacing) to 12.0 nm (the widest spacing). The average output power and side mode suppression ratio (SMSR) of the HP-DWTFL are measured to be 15 dBm and 52.55 dB, respectively. The proposed HP-DWTFL is highly stable with no variations in the chosen output wavelengths and has minimal changes in the output power. Such a laser has good potential for use in measurements, communications, spectroscopy and terahertz applications. (control of radiation parameters)

  19. Optical design of f-theta lens for dual wavelength selective laser melting

    NASA Astrophysics Data System (ADS)

    Feng, Lianhua; Cao, Hongzhong; Zhang, Ning; Xu, Xiping; Duan, Xuanming

    2016-10-01

    F-theta lens is an important unit for selective laser melting (SLM) manufacture. The dual wavelength f-theta lens has not been used in SLM manufacture. Here, we present the design of the f-theta lens which satisfies SLM manufacture with coaxial 532 nm and 1030 nm 1080 nm laser beams. It is composed of three pieces of spherical lenses. The focal spots for 532 nm laser and 1030 nm 1080 nm laser are smaller than 35 μm and 70 μm, respectively. The results meet the demands of high precision SLM. The chromatic aberration could cause separation between two laser focal spots in the scanning plane, so chromatic aberration correction is very important to our design. The lateral color of the designed f-theta lens is less than 11 μm within the scan area of 150 mm x 150 mm, which meet the application requirements of dual wavelength selective laser melting.

  20. Q-switching an all-fiber laser using acousto-optic null coupler

    NASA Astrophysics Data System (ADS)

    Berg, Yuval; Goldring, Sharone; Pearl, Shaul; Arie, Ady

    2013-05-01

    A new method for Q-switching an all-fiber laser is presented. It is based on induced acoustic long period grating operating on a null coupler, which acts as acoustically controlled tunable output coupler. Q-switching is achieved by switching on and off the acoustic wave in a burst mode, thereby generating laser pulses that are ~400 times shorter than the acoustically controlled coupler's rise time. Output pulse energy of 22 μJ and temporal width of ~100 ns were measured at a wavelength of 1.54 μm.

  1. High Power Q-Switched Thulium Doped Fibre Laser using Carbon Nanotube Polymer Composite Saturable Absorber.

    PubMed

    Chernysheva, Maria; Mou, Chengbo; Arif, Raz; AlAraimi, Mohammed; Rümmeli, Mark; Turitsyn, Sergei; Rozhin, Aleksey

    2016-04-11

    We have proposed and demonstrated a Q-switched Thulium doped fibre laser (TDFL) with a 'Yin-Yang' all-fibre cavity scheme based on a combination of nonlinear optical loop mirror (NOLM) and nonlinear amplified loop mirror (NALM). Unidirectional lasing operation has been achieved without any intracavity isolator. By using a carbon nanotube polymer composite based saturable absorber (SA), we demonstrated the laser output power of ~197 mW and pulse energy of 1.7 μJ. To the best of our knowledge, this is the highest output power from a nanotube polymer composite SA based Q-switched Thulium doped fibre laser.

  2. Passively Q-switched Nd:GdTaO4 laser by graphene oxide saturable absorber

    NASA Astrophysics Data System (ADS)

    Zhang, Bingyuan; Song, Qi; Wang, Guoju; Gao, Yajing; Zhang, Qingli; Wang, Minghong; Wang, Wenjun

    2016-08-01

    We experimentally demonstrated a laser diode-pumped Q-switched Nd:GdTaO4 crystal laser at 1066 nm using a multilayer graphene oxide as the saturable absorber (GOSA). The GOSA is fabricated by transferring the liquid-phase-exfoliated GO nanosheets onto a K9 glass substrate. When the GOSA was inserted into the plano-plano laser cavity, a stable Q-switched laser operation is achieved with a maximum average output power of 0.382 W and repetition rate of 362 kHz. The shortest pulse duration is 194 ns and the single pulse energy is about 1.05 μJ.

  3. Diode pumped passively Q-switched Nd:LuAG laser at 1442.6 nm

    NASA Astrophysics Data System (ADS)

    Guan, Chen; Liu, Zhaojun; Cong, Zhenhua; Liu, Yang; Xu, Xiaodong; Xu, Jun; Huang, Qingjie; Rao, Han; Chen, Xia; Zhang, Yanmin; Wu, Qianwen; Bai, Fen; Zhang, Sasa

    2017-02-01

    A diode-end-pumped passively Q-switched Nd:LuAG laser at 1442.6 nm was demonstrated with a V3+:YAG crystal as the saturable absorber. Under continuous-wave (CW) operation, the maximum output power of 1.83 W was obtained with an absorbed pumping power of 11.1 W. The corresponding optical-to-optical conversion efficiency was 16.5%. Under Q-switched operation, the maximum average output power of 424 mW was obtained at the same pumping power. The pulse duration and pulse repetition rate were 72 ns and 17.4 kHz, respectively.

  4. Diode pumped CW and passively Q-switched Nd:LGGG laser at 1062 nm

    NASA Astrophysics Data System (ADS)

    Yang, H.; Jia, Z. T.; Zhang, B. T.; He, J. L.; Liu, S. D.; Yang, Y.; Tao, X. T.

    2012-05-01

    We report a Nd:LGGG laser at 1062 nm in the operations of the continuous-wave (CW) and passively Q-switching. The maximum CW output power of 5.62 W was obtained, corresponding to an optical-to-optical conversion efficiency of 49.0% and slope efficiency of 55.9%. By using Cr4+:YAG with initial transmission of 94% as the saturable absorber, for the first time, we got the maximum passively Q-switched output power of 1.21 W, accompanied with a highest pulse repetition rate of 27.1 kHz and a shortest pulse width of 9.1 ns.

  5. High Power Q-Switched Thulium Doped Fibre Laser using Carbon Nanotube Polymer Composite Saturable Absorber

    PubMed Central

    Chernysheva, Maria; Mou, Chengbo; Arif, Raz; AlAraimi, Mohammed; Rümmeli, Mark; Turitsyn, Sergei; Rozhin, Aleksey

    2016-01-01

    We have proposed and demonstrated a Q-switched Thulium doped fibre laser (TDFL) with a ‘Yin-Yang’ all-fibre cavity scheme based on a combination of nonlinear optical loop mirror (NOLM) and nonlinear amplified loop mirror (NALM). Unidirectional lasing operation has been achieved without any intracavity isolator. By using a carbon nanotube polymer composite based saturable absorber (SA), we demonstrated the laser output power of ~197 mW and pulse energy of 1.7 μJ. To the best of our knowledge, this is the highest output power from a nanotube polymer composite SA based Q-switched Thulium doped fibre laser. PMID:27063511

  6. Optimization Of Output Q-Switched Nd:YAG Laser Based On Switching Time

    NASA Astrophysics Data System (ADS)

    Tamuri, Abd Rahman; Daud, Yaacob Mat; Bidin, Noriah

    2010-07-01

    This paper reports the optimization of output Q-switch Nd:YAG. A free running Nd:YAG laser was employed as source of light. KD*P crystal was utilized as a Pockels cell. Avalanche transistor pulser was designed to switch a high voltage power supply. The switching time was conducted via a control unit based PIC16F84A microcontroller. The pulser was able to switch the voltage within 3 ns. The optimum switching time of Q-switching is obtained at 182.34 μs. The corresponding laser output is 40 mJ with pulse duration of 25 ns.

  7. High Power Q-Switched Thulium Doped Fibre Laser using Carbon Nanotube Polymer Composite Saturable Absorber

    NASA Astrophysics Data System (ADS)

    Chernysheva, Maria; Mou, Chengbo; Arif, Raz; Alaraimi, Mohammed; Rümmeli, Mark; Turitsyn, Sergei; Rozhin, Aleksey

    2016-04-01

    We have proposed and demonstrated a Q-switched Thulium doped fibre laser (TDFL) with a ‘Yin-Yang’ all-fibre cavity scheme based on a combination of nonlinear optical loop mirror (NOLM) and nonlinear amplified loop mirror (NALM). Unidirectional lasing operation has been achieved without any intracavity isolator. By using a carbon nanotube polymer composite based saturable absorber (SA), we demonstrated the laser output power of ~197 mW and pulse energy of 1.7 μJ. To the best of our knowledge, this is the highest output power from a nanotube polymer composite SA based Q-switched Thulium doped fibre laser.

  8. Compact frequency-modulation Q-switched single-frequency fiber laser at 1083 nm

    NASA Astrophysics Data System (ADS)

    Zhang, Yuanfei; Feng, Zhouming; Xu, Shanhui; Mo, Shupei; Yang, Changsheng; Li, Can; Gan, Jiulin; Chen, Dongdan; Yang, Zhongmin

    2015-12-01

    A compact frequency-modulation Q-switched single-frequency fiber laser is demonstrated at 1083 nm. The short linear resonant cavity consists of a 12 mm long homemade Yb3+-doped phosphate fiber and a pair of fiber Bragg gratings (FBGs) in which the Q-switching and the frequency excursion is achieved by a tensile-induced period modulation. Over 375 MHz frequency-tuning range is achieved with a modulation frequency varying from tens to hundreds of kilohertz. The highest peak power of the output pulse reaching 6.93 W at the repetition rate of 10 kHz is obtained.

  9. One-Joule-per-Pulse Q-Switched 2-micron Solid State Laser

    NASA Technical Reports Server (NTRS)

    Yu, Jirong; Trieu, Bo C.; Modlin, Ed A.; Singh, Upendra N.; Kavaya, Michael J.; Chen, Songsheng; Bai, Yingxin; Petzar, Pual J.; Petros, Mulugeta

    2005-01-01

    Q-switched output of 1.1 J per pulse at 2-micron wavelength has been achieved in a diode pumped Ho:Tm:LuLF laser using a side-pumped rod configuration in a Master-Oscillator-Power-Amplifier (MOPA) architecture. This is the first time that a 2-micron laser has broken the Joule per pulse barrier for Q-switched operation. The total system efficiency reaches 5% and 6.2% for single and double pulse operation, respectively. The system produces excellent 1.4 times of transform limited beam quality.

  10. A stopped-flow dual-wavelength spectrophotometer suitable for the study of respiratory chains.

    PubMed Central

    Garland, P B; Littleford, S J; Haddock, B A

    1976-01-01

    The requirements for a dual-wavelength stopped-flow spectrophotometer to be suitable for studying limited quantities of respiratory-chain preparations are described. They can be met by a design using mainly commercially available components. The constructed apparatus has a dead-time of approx. 2.6 ms, a mixing ratio of 17:1, and a minimal requirement for 0.5 ml of mixed reactants per flow. PMID:938452

  11. On Study of Air/Space-borne Dual-Wavelength Radar for Estimates of Rain Profiles

    NASA Technical Reports Server (NTRS)

    Liao, Liang; Meneghini, Robert

    2004-01-01

    In this study, a framework is discussed to apply air/space-borne dual-wavelength radar for the estimation of characteristic parameters of hydrometeors. The focus of our study is on the Global Precipitation Measurements (GPM) precipitation radar, a dual-wavelength radar that operates at Ku (13.8 GHz) and Ka (35 GHz) bands. As the droplet size distributions (DSD) of rain are expressed as the Gamma function, a procedure is described to derive the median volume diameter (D(sub 0)) and particle number concentration (N(sub T)) of rain. The correspondences of an important quantity of dual-wavelength radar, defined as deferential frequency ratio (DFR), to the D(sub 0) in the melting region are given as a function of the distance from the 0 C isotherm. A self-consistent iterative algorithm that shows a promising to account for rain attenuation of radar and infer the DSD without use of surface reference technique (SRT) is examined by applying it to the apparent radar reflectivity profiles simulated from the DSD model and then comparing the estimates with the model (true) results. For light to moderate rain the self-consistent rain profiling approach converges to unique and correct solutions only if the same shape factors of Gamma functions are used both to generate and retrieve the rain profiles, but does not converges to the true solutions if the DSD form is not chosen correctly. To further examine the dual-wavelength techniques, the self-consistent algorithm, along with forward and backward rain profiling algorithms, is then applied to the measurements taken from the 2nd generation Precipitation Radar (PR-2) built by Jet Propulsion Laboratory. It is found that rain profiles estimated from the forward and backward approaches are not sensitive to shape factor of DSD Gamma distribution, but the self-consistent method is.

  12. Dual-Wavelength Terahertz Metasurfaces with Independent Phase and Amplitude Control at Each Wavelength

    PubMed Central

    Ding, Jun; Xu, Ningning; Ren, Han; Lin, Yuankun; Zhang, Weili; Zhang, Hualiang

    2016-01-01

    We have designed, fabricated and characterized dual-wavelength metasurfaces that function at two assigned terahertz wavelengths with independent phase and amplitude control at each wavelength. Specifically, we have designed a dual-wavelength achromatic metasurface-based deflector deflecting the incident wave to the same direction at two selected wavelengths, which has circumvented the critical limitation of strong wavelength dependence in the planar metasurface-based devices caused by the resonant nature of the plasmonic structures. As a proof of concept demonstration, the designed dual-wavelength achromatic deflector has been fabricated, and characterized experimentally. The numerical simulations, theoretical predictions, and experimental results agree very well with each other, demonstrating the property of independently manipulating the phase profiles at two wavelengths. Furthermore, another unique feature of the designed metasurface is that it can independently tailor both the phase and amplitude profiles at two wavelengths. This property has been numerically validated by engineering a metasurface-based device to simultaneously generate two diffraction orders at two desired wavelengths. PMID:27659800

  13. Study of dual wavelength composite output of solid state laser based on adjustment of resonator parameters

    NASA Astrophysics Data System (ADS)

    Wang, Lei; Nie, Jinsong; Wang, Xi; Hu, Yuze

    2016-10-01

    The 1064nm fundamental wave (FW) and the 532nm second harmonic wave (SHW) of Nd:YAG laser have been widely applied in many fields. In some military applications requiring interference in both visible and near-infrared spectrum range, the de-identification interference technology based on the dual wavelength composite output of FW and SHW offers an effective way of making the device or equipment miniaturized and low cost. In this paper, the application of 1064nm and 532nm dual-wavelength composite output technology in military electro-optical countermeasure is studied. A certain resonator configuration that can achieve composite laser output with high power, high beam quality and high repetition rate is proposed. Considering the thermal lens effect, the stability of this certain resonator is analyzed based on the theory of cavity transfer matrix. It shows that with the increase of thermal effect, the intracavity fundamental mode volume decreased, resulting the peak fluctuation of cavity stability parameter. To explore the impact the resonator parameters does to characteristics and output ratio of composite laser, the solid-state laser's dual-wavelength composite output models in both continuous and pulsed condition are established by theory of steady state equation and rate equation. Throughout theoretical simulation and analysis, the optimal KTP length and best FW transmissivity are obtained. The experiment is then carried out to verify the correctness of theoretical calculation result.

  14. Tunable dual-wavelength fiber laser with ultra-narrow linewidth based on Rayleigh backscattering.

    PubMed

    Zhu, Tao; Zhang, Baomei; Shi, Leilei; Huang, Shihong; Deng, Ming; Liu, Jianguo; Li, Xiong

    2016-01-25

    Dual-wavelength fiber lasers with ultra-narrow linewidth find wide applications in high-speed optical communications, fiber optic sensors, high resolution measurements and medical instruments and microwave or terahertz generation systems. Based on the linewidth compression mechanism due to Rayleigh backscattering, this paper adopts a simple ring structure cooperated with two fiber Bragg gratings centered at 1550 nm and 1530 nm respectively, achieving a dual-wavelength fiber laser with ultra-narrow linewidth, with a 3dB linewidth of ~700 Hz for each wavelength, and the SNR of 60dB. Tuning the center wavelength of one of the two FBGs while the other one keeps unchanged, the fiber laser keeps stable dual-wavelength lasing and the linewidth is still ~700 Hz. It can be seen that the compression for the linewidth based on the Rayleigh backscattering can be used in multi-wavelength laser systems, and because of the characteristic of the Rayleigh backscattering, the method has great potential in the application of wide wavelength range linewidth compression from the ultraviolet to the far infrared.

  15. Dual-Wavelength Terahertz Metasurfaces with Independent Phase and Amplitude Control at Each Wavelength

    NASA Astrophysics Data System (ADS)

    Ding, Jun; Xu, Ningning; Ren, Han; Lin, Yuankun; Zhang, Weili; Zhang, Hualiang

    2016-09-01

    We have designed, fabricated and characterized dual-wavelength metasurfaces that function at two assigned terahertz wavelengths with independent phase and amplitude control at each wavelength. Specifically, we have designed a dual-wavelength achromatic metasurface-based deflector deflecting the incident wave to the same direction at two selected wavelengths, which has circumvented the critical limitation of strong wavelength dependence in the planar metasurface-based devices caused by the resonant nature of the plasmonic structures. As a proof of concept demonstration, the designed dual-wavelength achromatic deflector has been fabricated, and characterized experimentally. The numerical simulations, theoretical predictions, and experimental results agree very well with each other, demonstrating the property of independently manipulating the phase profiles at two wavelengths. Furthermore, another unique feature of the designed metasurface is that it can independently tailor both the phase and amplitude profiles at two wavelengths. This property has been numerically validated by engineering a metasurface-based device to simultaneously generate two diffraction orders at two desired wavelengths.

  16. The space-dependent model and output characteristics of intra-cavity pumped dual-wavelength lasers

    NASA Astrophysics Data System (ADS)

    He, Jin-Qi; Dong, Yuan; Zhang, Feng-Dong; Yu, Yong-Ji; Jin, Guang-Yong; Liu, Li-Da

    2016-01-01

    The intra-cavity pumping scheme which is used to simultaneously generate dual-wavelength lasers was proposed and published by us and the space-independent model of quasi-three-level and four-level intra-cavity pumped dual-wavelength lasers was constructed based on this scheme. In this paper, to make the previous study more rigorous, the space-dependent model is adopted. As an example, the output characteristics of 946 nm and 1064 nm dual-wavelength lasers under the conditions of different output mirror transmittances are numerically simulated by using the derived formula and the results are nearly identical to what was previously reported.

  17. High-power continuous-wave dual-wavelength operation of a diode-pumped Yb:KGW laser.

    PubMed

    Akbari, Reza; Zhao, Haitao; Major, Arkady

    2016-04-01

    High-power dual-wavelength diode-pumped Yb:KGW laser using a single birefringent filter plate was demonstrated. Two oscillating wavelengths maintained the same polarization and stable dual-wavelength operation at 1014.6 and 1041.3 nm (7.57 THz of frequency offset) with 3.4 W of average output power and a diffraction-limited beam profile was obtained. Dual-wavelength laser operation at shorter- or longer-wavelength pairs with lower average output power could also be realized for other output-coupling transmissions.

  18. Compact high-repetition-rate terahertz source based on difference frequency generation from an efficient 2-μm dual-wavelength KTP OPO

    NASA Astrophysics Data System (ADS)

    Mei, Jialin; Zhong, Kai; Wang, Maorong; Liu, Pengxiang; Xu, Degang; Wang, Yuye; Shi, Wei; Yao, Jianquan; Norwood, Robert A.; Peyghambarian, Nasser

    2016-11-01

    A compact optical terahertz (THz) source was demonstrated based on an efficient high-repetition-rate doubly resonant optical parametric oscillator (OPO) around 2 μm with two type-II phase-matched KTP crystals in the walk-off compensated configuration. The KTP OPO was intracavity pumped by an acousto-optical (AO) Q-switched Nd:YVO4 laser and emitted two tunable wavelengths near degeneracy. The tuning range extended continuously from 2.068 μm to 2.191 μm with a maximum output power of 3.29 W at 24 kHz, corresponding to an optical-optical conversion efficiency (from 808 nm to 2 μm) of 20.69%. The stable pulsed dual-wavelength operation provided an ideal pump source for generating terahertz wave of micro-watt level by the difference frequency generation (DFG) method. A 7.84-mm-long periodically inverted quasi-phase-matched (QPM) GaAs crystal with 6 periods was used to generate a terahertz wave, the maximum voltage of 180 mV at 1.244 THz was acquired by a 4.2-K Si bolometer, corresponding to average output power of 0.6 μW and DFG conversion efficiency of 4.32×10-7. The acceptance bandwidth was found to be larger than 0.35 THz (FWHM). As to the 15-mm-long GaSe crystal used in the type-II collinear DFG, a tunable THz source ranging from 0.503 THz to 3.63 THz with the maximum output voltage of 268 mV at 1.65 THz had been achieved, and the corresponding average output power and DFG conversion efficiency were 0.9 μW and 5.86×10-7 respectively. This provides a potential practical palm-top tunable THz sources for portable applications.

  19. Dual-wavelength passive and hybrid mode-locking of 3, 4.5 and 10 GHz InAs/InP(100) quantum dot lasers.

    PubMed

    Tahvili, M S; Du, L; Heck, M J R; Nötzel, R; Smit, M K; Bente, E A J M

    2012-03-26

    We present an investigation of passive and hybrid mode-locking in Fabry-Pérot type two-section InAs/InP(100) quantum dot lasers that show dual wavelength operation. Over the whole current and voltage range for mode-locking of these lasers, the optical output spectra show two distinct lobes. The two lobes provide a coherent bandwidth and are verified to lead to two synchronized optical pulses. The generated optical pulses are elongated in time due to a chirp which shows opposite signs over the two spectral lobes. Self-induced mode-locking in the single-section laser shows that the dual-wavelength spectra correspond to emission from ground state. In the hybrid mode-locking regime, a map of locking range is presented by measuring the values of timing jitter for several values of power and frequency of the external electrical modulating signal. An overview of the systematic behavior of InAs/InP(100) quantum dot mode-locked lasers is presented as conclusion.

  20. A compact and efficient four-wavelength Q-switched Nd:YAP laser

    NASA Astrophysics Data System (ADS)

    Huang, C. H.; Zhang, G.; Wei, Y.; Zhu, H. Y.; Huang, L. X.

    2010-04-01

    In this paper, a four-wavelength electro-optic (E-O) Q-switched solid-state laser system was presented. This laser system only use one Nd:YAP laser crystal, which irradiates 1079.5 nm and 1341.4 nm fundamental wavelengths. Both of these wavelength lasers and their second harmonic generation (SHG) compose a four-wavelength Nd:YAP Q-switched laser. The Q-switched output energies of 277 mJ for 1079.5 nm and 61 mJ for 539.8 nm and that of 190 mJ for 1341.4 nm and 51 mJ for 670.7 nm wavelengths were achieved. The pulse durations of 1079.5 and 539.8 nm lasers and that of 1341.4 and 670.7 nm lasers are 20 and 40 ns, respectively. Due to this laser system has the larger chance and convenience for selecting the wavelengths and operation modes by moving a stepping motor and controlling the Q-switched devices, it will broaden applications in the fields of laser cosmetology, dermatotis therapy, material processing and laser display etc.

  1. A robust all-fiber active Q-switched 1-µm Yb3+ fiber laser

    NASA Astrophysics Data System (ADS)

    Sintov, Yoav; Goldring, Sharone; Pearl, Shaul; Lebiush, Eyal; Sfez, Bruno; Malka, Dror; Zalevsky, Zeev

    2015-09-01

    An all-fiber active Q-switched Yb3+-doped fiber laser at 1 µm is presented. The laser is composed of a ring resonator with an embedded all-fiber Q-switch element, based on a null coupler with an attached piezoelectric transducer (PZT). The PZT is used as an acoustic actuator, for inducing longitudinal acoustic disturbance along the null coupler and causing light coupling between the null coupler's ports. A stable operation is achieved with an overall average output power of up to 275 mW at various pulse repetition rates (PRR), ranging from 10 to 35 kHz and typical pulse energy of 15 μJ. In addition, a self-monitoring method is implemented by an embedded microcontroller, in order to maintain stable Q-switch performance, in changing environmental conditions. An average power of 8.5 W and pulse energy of 420 μJ at a PRR of 20 kHz are demonstrated in a master oscillator power amplifier containing the Q-switched laser, followed by a power amplifier.

  2. Optical modeling of the Q-switch lasers with a coherent gain model

    NASA Astrophysics Data System (ADS)

    Lawrence, George N.; Yu, Anthony; Schwarz, Jens

    2011-10-01

    Q-switch lasers are traditionally modeled using the rate equation approximation[1]. This model is effective in relating the energy of the population inversion to the energy in the optical pulse. It is especially effective when augmented by the Frantz-Nodvik theory that effectively builds in conservation of energy. However, the rate equation approximation theory cannot independently describe the formation of longitudinal modes and, because it does not correctly consider the finite response time of the medium, its accuracy in predicting the very fast rise time of Q-switch pulses is suspect. A more powerful based on the laser gain in terms of radiating, resonant dipoles-the coherent gain model-is needed. This paper reports progress to incorporate the more advanced coherent gain into a 3D, time resolved numerical model that can predict both sub-nanosecond effects, the growth of longitudinal modes in the Q-switched laser, and other coherent effects. Work remains to be done to explore the capabilities of this model to its full range of possibilities. Sandia National Laboratories has been interested in short pulse modeling and provided support for the development of the coherent gain model which is now being applied to the NASA Q-switch program to address fast rise times and the formation of longitudinal modes[2]-[6].

  3. Passive Q Switching of a Solar-Pumped Nd:YAG Laser

    NASA Astrophysics Data System (ADS)

    Lando, Mordechai; Shimony, Yehoshua; Noter, Yoram; Benmair, Roth M. J.; Yogev, Amnon

    2000-04-01

    Passive Q switching is a preferable choice for switching the Q factor of a solar-pumped laser because it requires neither a driver nor an electrical power supply. The superior thermal characteristics and durability of Cr 4 :YAG single crystals as passive Q switches for lamp and diode-pumped high-power lasers has been demonstrated. Here we report on an average power of 37 W and a switching efficiency of 80% obtained by use of a solar-pumped Nd:YAG laser Q switched by a Cr 4 :YAG saturable absorber. Concentration of the pumping solar energy on the laser crystal was obtained with a three-stage concentrator, composed of 12 heliostats, a three-dimensional compound parabolic concentrator (CPC) and a two-dimensional CPC. The water-cooled passive Q switch also served as the laser rear mirror. Repetition rates of as much as 50 kHz, at pulse durations between 190 and 310 ns (FWHM) were achieved. From the experimental results, the saturated single-pass power absorption of the Cr 4 :YAG device was estimated as 3 1%.

  4. Performance of passive Q-switched solar-pumped high-power Nd:YAG lasers

    NASA Astrophysics Data System (ADS)

    Noter, Yoram; Naftali, Nir; Pe'er, Idit L.; Yogev, Amnon; Lando, Mordechai; Shimony, Yehoshua

    1997-09-01

    Q-switched, solar-pumped, high power Nd:YAG lasers are attractive for a variety of applications requiring high instantaneous peak power density. The Q-switching can be obtained by an acousto-optic, electro-optic or passive device. Passive Q-switching seems an excellent choice for space as well as for other applications since it neither requires an external driver nor an electrical power supply. In recent years Cr+4:YAG single crystals were extensively used as passive Q-switches for flashlamp-pumped high power Nd:YAG lasers, demonstrating their superior thermal superior thermal characteristics and durability. In this work we report the first operation of passive Q- switched, solar-pumped, high power Nd:YAG lasers. The concentrated solar energy for he optical pumping of the laser was obtained by a 3-stage combination of imaging and non-imaging optics. It included: i) Weizmann Institute solar tower heliostats, ii) 3D compound parabolic concentrator, and iii) 2D compound parabolic concentrator in which the laser rod was placed. 72 mm long laser rods with either 3 mm or 4 mm diameter were used. The passive Q-switch was made from a Cr$=+4):YAG single crystal having a low- intensity transmission of 72 percent at 1.06 (mu) . Its rear surface was coated by a high reflectivity coating, serving as the rear mirror of the cavity. Output coupling mirrors with various reflectivities were used. The passive Q-switch demonstrated excellent durability and reliability during all the experiments. Repetition rates of 6-39 kHz were measured, showing higher repetition rates at higher laser power levels. The pulses demonstrated shorter full width at half maximum (FWHM) time for higher laser power elves, and the FWHM time range was 190-310 nsec. The maximal measured average power was 14 W. Thermal lensing was measured as a function of the absorbed solar power in the laser rod. It is estimated that laser peak power densities of approximately 100 kW/cm2 were achieved in the experiments. It is

  5. Evaluating UV-C LED disinfection performance and investigating potential dual-wavelength synergy.

    PubMed

    Beck, Sara E; Ryu, Hodon; Boczek, Laura A; Cashdollar, Jennifer L; Jeanis, Kaitlyn M; Rosenblum, James S; Lawal, Oliver R; Linden, Karl G

    2017-02-01

    A dual-wavelength UV-C LED unit, emitting at peaks of 260 nm, 280 nm, and the combination of 260|280 nm together was evaluated for its inactivation efficacy and energy efficiency at disinfecting Escherichia coli, MS2 coliphage, human adenovirus type 2 (HAdV2), and Bacillus pumilus spores, compared to conventional low-pressure and medium-pressure UV mercury vapor lamps. The dual-wavelength unit was also used to measure potential synergistic effects of multiple wavelengths on bacterial and viral inactivation and DNA and RNA damage. All five UV sources demonstrated similar inactivation of E. coli. For MS2, the 260 nm LED was most effective. For HAdV2 and B. pumilus, the MP UV lamp was most effective. When measuring electrical energy per order of reduction, the LP UV lamp was most efficient for inactivating E. coli and MS2; the LP UV and MP UV mercury lamps were equally efficient for HAdV2 and B. pumilus spores. Among the UV-C LEDs, there was no statistical difference in electrical efficiency for inactivating MS2, HAdV2, and B. pumilus spores. The 260 nm and 260|280 nm LEDs had a statistical energy advantage for E. coli inactivation. For UV-C LEDs to match the electrical efficiency per order of log reduction of conventional LP UV sources, they must reach efficiencies of 25-39% or be improved on by smart reactor design. No dual wavelength synergies were detected for bacterial and viral inactivation nor for DNA and RNA damage.

  6. Phase retrieval without unwrapping by single-shot dual-wavelength digital holography

    NASA Astrophysics Data System (ADS)

    Min, Junwei; Yao, Baoli; Zhou, Meiling; Guo, Rongli; Lei, Ming; Yang, Yanlong; Dan, Dan; Yan, Shaohui; Peng, Tong

    2014-12-01

    A phase retrieval method by using single-shot dual-wavelength digital holography is proposed. Each single wavelength hologram is extracted from the color CCD recorded hologram at one exposure, and the unwrapped phase image of object can be reconstructed directly. Different from the traditional multiple wavelength phase unwrapping techniques, any single complex wave-fronts at different wavelengths have no need to be calculated any more. Thus, the phase retrieval is computationally fast and straightforward, and the limitations on the total optical path difference are significantly relaxed. The practicability of the proposed method is demonstrated by both simulated and experimental results.

  7. Simulation experiments to generate broadband chaos using dual-wavelength optically injected Fabry-Perot laser

    NASA Astrophysics Data System (ADS)

    Obaid, Hafiz Muhammad; Khawar Islam, Muhammad; Obaid Ullah, Muhammad

    2016-08-01

    Broadband chaos can be generated by beating two wavelengths in a hybrid arrangement of Fabry-Perot (FP) Laser and Fiber ring cavity by injecting dual wavelengths. The bandwidth of generated chaos can be controlled by detuning different modes of FP Laser for beating. The bandwidth of generated chaos increased to many folds depending upon the injected strength and wavelength spacing matched to FP laser modes. The bandwidth enhancement in different simulation experiments conducted is optimized by varying different parameters of FP laser and cavity. The waveforms are analyzed and Lyapunov exponents are calculated in order to validate the existence of high bandwidth non-pulsating chaos.

  8. Compact dual-wavelength thulium-doped fiber laser employing a double-ring filter.

    PubMed

    Fan, Xuliang; Zhou, Wei; Wang, Siming; Liu, Xuan; Wang, Yong; Shen, Deyuan

    2016-04-20

    In this paper, we report on stable dual-wavelength operation of a thulium-doped compact all-fiber laser using a double-ring filter as the wavelength selective element. Simultaneously lasing at 2014.4 and 2018.4 nm has been obtained via tuning the polarization controllers to adjust the relative gain and loss of the laser cavity. The side mode suppression ratios are greater than 52 dB and the output power difference between the two lasing lines is less than 0.08 dB under 2.6 W of incident pump power.

  9. Tunable dual-wavelength filter and its group delay dispersion in domain-engineered lithium niobate

    NASA Astrophysics Data System (ADS)

    Shao, Guang-hao; Song, Jing; Ruan, Ya-ping; Cui, Guo-xin; Lu, Yan-qing

    2016-12-01

    A tunable dual-wavelength filter is experimentally demonstrated in domain-engineered lithium niobate. Application of an electric field on the y-surfaces of the sample results in the optical axes rotating clockwise and anticlockwise, which makes selective polarization rotation. The quasi phase-matching wavelengths could be adjusted through suitable domain design. A unique dual valley spectrum is obtained in a periodically poled lithium niobate structure with a central defect if the sample is placed between two parallel polarizers. The expected bandwidth could be varied from ˜1 nm to ˜40 nm. Moreover, both the spectral response and group delay dispersion could be engineered.

  10. Failure of Q-switched ruby laser to eradicate atypical-appearing solar lentigo: report of two cases.

    PubMed

    Lee, P K; Rosenberg, C N; Tsao, H; Sober, A J

    1998-02-01

    Cutaneous lasers, including argon, Q-switched Nd:YAG, Q-switched ruby, Q-switched alexandrite, and short pulsed dye lasers, have been used to treat solar lentigines and other benign melanocytic lesions. However, the effects of these lasers at standard fluences on atypical melanocytic lesions have not been examined. We describe two patients in whom the Q-switched ruby laser failed to successfully treat clinically atypical-appearing solar lentigines. In both, clinically atypical-appearing melanocytic lesions were treated with excellent initial cosmetic results. In the first patient, the pigmentation returned several months after treatment and continued to increase in size and color. A biopsy specimen 30 months after Q-switched ruby laser therapy revealed a lentigo maligna melanoma. In the second patient, the lesion recurred 6 months after Q-switched ruby laser therapy, and a biopsy specimen 1 year after treatment showed an early lentigo maligna. Thus Q-switched ruby lasers and other cutaneous lasers capable of targeting melanin may be inadequate to eliminate lentigo maligna and other atypical melanocytic lesions completely. These cases emphasize the importance of careful clinical assessment before any laser surgery and the need to advise patients to return for evaluation should pigmentation return.

  11. Zinc oxide (ZnO) nanoparticles as saturable absorber in passively Q-switched fiber laser

    NASA Astrophysics Data System (ADS)

    Ahmad, H.; Lee, C. S. J.; Ismail, M. A.; Ali, Z. A.; Reduan, S. A.; Ruslan, N. E.; Ismail, M. F.; Harun, S. W.

    2016-12-01

    We demonstrate a passively Q-switched erbium-doped fiber laser using zinc oxide (ZnO) nanoparticles thin film as saturable absorber (SA). ZnO exhibits high nonlinear optical response and fast recovery time, fulfilling the requirements of an ideal SA. The nonlinear optical absorption is characterised by modulation depth of 3.5% with saturation intensity of 0.016 MW cm-2. We insert the SA into the laser cavity and obtain stable Q-switched pulse whereby the repetition rate increases from 41.7 kHz to 77.2 kHz while the pulse width decreases from 9.6 μs to 3.0 μs as the pump power is increased from 60 mW to 360 mW. This result suggests that ZnO could be a promising SA for photonic applications.

  12. Picosecond pulse generation in a hybrid Q-switched laser source by using a microelectromechanical mirror.

    PubMed

    Couderc, Vincent; Crunteanu, Aurelian; Fabert, Marc; Doutre, Florent; El Bassri, Farid; Pagnoux, Dominique; Jalocha, Alain

    2012-02-27

    We present a novel Q-switched laser source using a micro-optical-electromechanical mirror (MOEM) designed for short pulse emission. It is based on a hybrid configuration including a passively Q-switched microchip laser coupled to a fiber cavity closed by a cantilever type MOEM acting as an active modulator. This specially designed mirror with a single reflecting gold membrane is switched by low bias voltage ~50 V (peak to peak). This device emits pulses at tunable repetition rates up to 1.6 kHz, with ~564 ps duration and 3.4 kW peak power, which constitutes the shortest pulse duration ever reported with MOEMs based pulsed lasers.

  13. Black phosphorus-based saturable absorber for Q-switched Tm:YAG ceramic laser

    NASA Astrophysics Data System (ADS)

    Xie, Yixuan; Kong, Lingchen; Qin, Zhipeng; Xie, Guoqiang; Zhang, Jian

    2016-08-01

    We have experimentally demonstrated a passively Q-switched Tm-doped YAG ceramic laser with black phosphorus (BP) as saturable absorber (SA). According to the measurement, the BP saturable absorber mirror has a modulation depth of 5% and a saturation fluence of 20 μJ/cm2. The generated Q-switched pulse has a maximum average power of 38.5 mW and pulse energy of 3.32 μJ, with the corresponding repetition rate of 11.6 KHz and pulse width of 3.12 μs at 2 μm wavelength. The results show that BP is a promising SA for midinfrared-pulsed lasers.

  14. CONTROL OF LASER RADIATION PARAMETERS: Passive Q switches for a diode-pumped erbium glass laser

    NASA Astrophysics Data System (ADS)

    Kisel', V. E.; Shcherbitskii, V. G.; Kuleshov, N. V.; Postnova, L. I.; Levchenko, V. I.; Galagan, B. I.; Denker, B. I.; Sverchkov, S. E.

    2005-07-01

    A diode-pumped, passively Q-switched 1.54-μm erbium glass laser is studied. Zinc selenide (ZnSe) crystals doped with Co2+ and Cr2+ ions and magnesium—aluminium spinel (MgAl2O4) crystals doped with Co2+ ions were used as saturable absorbers in Q switches. It is shown that, depending on the type of a saturable absorber, the pump power, and the resonator design, the laser pulse energy can vary from 0.2 to 13 μJ, the pulse duration from 16 to 980 ns, and the pulse repetition rate from 0.1 to 30 kHz.

  15. Compressed 6 ps pulse in nonlinear amplification of a Q-switched microchip laser

    NASA Astrophysics Data System (ADS)

    Diao, Ruxin; Liu, Zuosheng; Niu, Fuzeng; Wang, Aimin; Taira, Takunori; Zhang, Zhigang

    2017-02-01

    We present a passively Q-switched Nd:YVO4 crystal microchip laser with a 6 ps pulse width, which is based on SPM-induced spectral broadening and pulse compression. The passive Q-switching is obtained by a semiconductor saturable absorber mirror. The laser’s seed source centered at 1064 nm pulses with a duration of 80 ps, at a repetition rate of 600 kHz corresponding to an average output power of 10 mW. After amplification and compression, the pulses were compressed to 6 ps with a maximum pulse energy of 0.5 µJ.

  16. The output beam quality of a Q-switched Nd:glass slab laser

    NASA Technical Reports Server (NTRS)

    Reed, Murray K.; Byer, Robert L.

    1990-01-01

    The authors have constructed and tested a flashlamp pumped, Q-switched, Nd:glass zigzag slab laser. The thermally induced optical distortion through the slab is minimized by uniform pumping and cooling and the use of corrective pump shields at the slab ends. The laser spatial output for Q-switched resonators has been measured and modeled. It is shown that a larger aperture planar oscillator has an output divergence many times above the diffraction limit. Operation as a one-dimensional unstable resonator in the wide direction of the slab allows the efficient extraction of energy in a high-quality beam. Near-diffraction-limited laser output of 5 J at 4 Hz is achieved with a resonator that includes an intracavity telescope to correct for residual defocusing in the thin direction of the slab.

  17. Diode-pumped continuous wave tunable and graphene Q-switched Tm:LSO lasers.

    PubMed

    Feng, T L; Zhao, S Z; Yang, K J; Li, G Q; Li, D C; Zhao, J; Qiao, W C; Hou, J; Yang, Y; He, J L; Zheng, L H; Wang, Q G; Xu, X D; Su, L B; Xu, J

    2013-10-21

    We have investigated the lasing characteristics of Tm:LSO crystal in three operation regimes: continuous wave (CW), wavelength tunable and passive Q-switching based on graphene. In CW regime, a maximum output power of 0.65 W at 2054.9 nm with a slope efficiency of 21% was achieved. With a quartz plate, a broad wavelength tunable range of 145 nm was obtained, corresponding to a FWHM of 100 nm. By using a graphene saturable absorber mirror, the passively Q-switched Tm:LSO laser produced pulses with duration of 7.8 μs at 2030.8 nm under a repetition rate of 7.6 kHz, corresponding to pulse energy of 14.0 μJ.

  18. Passively Q-switching induced by the smallest single-walled carbon nanotubes

    SciTech Connect

    Xu, X. T.; Zhai, J. P.; Wang, J. S.; Chen, Y. P.; Yu, Y. Q.; Zhang, M.; Li, I. L.; Ruan, S. C.; Tang, Z. K.

    2014-04-28

    We report a passively Q-switched erbium-doped fiber laser (EDFL) by using the smallest single-walled carbon nanotubes (SWNTs) with a diameter of 0.3 nm as the saturable absorber. These small SWNTs are fabricated in the nanochannels of a ZnAPO-11 (AEL) single crystal. By inserting one of the AEL crystal into an EDFL cavity pumped by a 980 nm laser diode, stable passive Q-switching is achieved for a threshold pump power of 206.2 mW, and 4.73 μs pulses with a repetition rate of 41.78 kHz and an average output power of 3.75 mW are obtained for a pump power of 406 mW.

  19. Laser-Tissue Interaction in Tattoo Removal by Q-Switched Lasers

    PubMed Central

    Barua, Shyamanta

    2015-01-01

    Q-switched (QS) lasers are widely considered the gold standard for tattoo removal, with excellent clinical results, impressive predictability, and a good safety profile. The generation of giant pulses by the method of Q-switching is responsible for the unique laser-tissue interaction that is seen in tattoo removal by QS lasers. The QS lasers work by impaction and dissolution of the tattoo pigments. Mechanical fragmentation of the tattoo pigments encased in intracellular lamellated organelles followed by their phagocytosis by macrophages is thought to be the major event in the clearance of pigments by QS lasers. A few novel techniques have been tried in recent times to hasten the clearance of tattoo pigments. PMID:25949016

  20. Injection seeding of a Q-switched alexandrite laser: Study of frequency stabilization

    NASA Technical Reports Server (NTRS)

    Brown, Lamarr A.

    1992-01-01

    AlGaAs diode lasers were used to injection seed a pulsed Q-switched alexandrite laser which produces a narrowband of radiation. Injection seeding is a method for achieving linewidths of less than 500 mega-Hz in the output of the broadband, tunable solid state laser. When the laser was set at a current of 59.8 milli-A and a temperature of 14.04 C, the wavelength was 767.6 nano-m. The Q-switched alexandrite laser was injection seeded and frequency stabilization was studied. The linewidth requirement was met, but the stability requirement was not due to drifting in the feedback voltage. Improvements on injection seeding should focus on increasing the feedback voltage to the laser diode, filtering the laser diode by using temperature controlled narrowband filters, and the use of diamond (SiC) grating placed inside the alexandrite laser's resonator cavity.

  1. Treatment of tattoos by Q-switched ruby laser. A dose-response study

    SciTech Connect

    Taylor, C.R.; Gange, R.W.; Dover, J.S.; Flotte, T.J.; Gonzalez, E.; Michaud, N.; Anderson, R.R. )

    1990-07-01

    Tattoo treatment with Q-switched ruby laser pulses (694 nm, 40 to 80 nanoseconds) was studied by clinical assessment and light and electron microscopy. Fifty-seven blue-black tattoos or portions thereof (35 amateur and 22 professional) were irradiated with 1.5 to 8.0 J/cm2 at a mean interval of 3 weeks. Substantial lightening or total clearing occurred in 18 (78%) of 23 amateur tattoos and 3 (23%) of 13 professional tattoos in which the protocol was completed. Response was related to exposure dose. Scarring occurred in one case, and persistent confettilike hypopigmentation was frequent. Optimal fluence was 4 to 8 J/cm2. Clinicohistologic correlation was poor. Q-switched ruby laser pulses can provide an effective treatment for tattoos.

  2. Laser-tissue interaction in tattoo removal by q-switched lasers.

    PubMed

    Barua, Shyamanta

    2015-01-01

    Q-switched (QS) lasers are widely considered the gold standard for tattoo removal, with excellent clinical results, impressive predictability, and a good safety profile. The generation of giant pulses by the method of Q-switching is responsible for the unique laser-tissue interaction that is seen in tattoo removal by QS lasers. The QS lasers work by impaction and dissolution of the tattoo pigments. Mechanical fragmentation of the tattoo pigments encased in intracellular lamellated organelles followed by their phagocytosis by macrophages is thought to be the major event in the clearance of pigments by QS lasers. A few novel techniques have been tried in recent times to hasten the clearance of tattoo pigments.

  3. High repetition rate Q-switched radially polarized laser with a graphene-based output coupler

    SciTech Connect

    Li, Lifei; Jin, Chenjie; Qi, Mei; Chen, Xiaoming; Ren, Zhaoyu E-mail: rzy@nwu.edu.cn; Zheng, Xinliang E-mail: rzy@nwu.edu.cn; Bai, Jintao; Sun, Zhipei

    2014-12-01

    We demonstrate a Q-switched radially polarized all-solid-state laser by transferring a graphene film directly onto an output coupler. The laser generates Q-switched radially polarized beam (QRPB) with a pulse width of 192 ns and 2.7 W average output power. The corresponding single pulse energy is up to 16.2 μJ with a high repetition rate of 167 kHz. The M{sup 2} factor and the polarization purity are ∼2.1 and 96%, respectively. Our QRPB source is a simple and low-cost source for a variety of applications, such as industrial material processing, optical trapping, and microscopy.

  4. Passively Q-switched 1.57-microm intracavity optical parametric oscillator.

    PubMed

    Yashkir, Y; van Driel, H M

    1999-04-20

    We demonstrate an eye-safe KTP-based optical parametric oscillator (OPO) driven intracavity by a diode-pumped 1064-nm Nd:YAG laser, passively Q-switched by a Cr4+:YAG crystal. The characteristics of this system, which operates at 1570 nm with a repetition rate as high as 50 Hz, are studied as a function of Cr4+:YAG optical density. Under optimum conditions the OPO generates 1.5-mJ, 3.4 +/- 0.1-ns pulses in a single transverse mode. For a Cr4+:YAG Q-switch element with an optical density of 0.5 the conversion efficiency of the intracavity energy is approximately 45% with the ratio of OPO to Nd:YAG peak-pulse intensity exceeding unity. These and other OPO characteristics compare favorably with a simple rate equation model of the OPO dynamics.

  5. Passively Q -Switched 1.57- m Intracavity Optical Parametric Oscillator

    NASA Astrophysics Data System (ADS)

    Yashkir, Yuri; van Driel, Henry M.

    1999-04-01

    We demonstrate an eye-safe KTP-based optical parametric oscillator (OPO) driven intracavity by a diode-pumped 1064-nm Nd:YAG laser, passively Q -switched by a Cr 4 :YAG crystal. The characteristics of this system, which operates at 1570 nm with a repetition rate as high as 50 Hz, are studied as a function of Cr 4 :YAG optical density. Under optimum conditions the OPO generates 1.5-mJ, 3.4 0.1-ns pulses in a single transverse mode. For a Cr 4 :YAG Q -switch element with an optical density of 0.5 the conversion efficiency of the intracavity energy is 45% with the ratio of OPO to Nd:YAG peak-pulse intensity exceeding unity. These and other OPO characteristics compare favorably with a simple rate equation model of the OPO dynamics.

  6. Passively Q-switched nd:YAG laser via a WS2 saturable absorber

    NASA Astrophysics Data System (ADS)

    Wang, Xi; Wang, Yonggang; Duan, Lina; Li, Lu; Sun, Hang

    2016-05-01

    In this work, we report a passively Q-switched Nd:YAG laser at 1064 nm by using WS2 solution as the saturable absorber (SA). The WS2 solution with different concentrations (0.25, 0.5, and 1 mg/ml) were fabricated by the liquid-phase-exfoliated method and injected into quartz cells. Such liquid absorbers have the virtues of adjustable optical absorption, high heat dissipation and non-contact damage. By inserting those WS2 solutions in the laser cavity, stable Q-switched laser operations were obtained. The corresponding pulse duration as short as 922 ns was obtained. The result shows that the WS2 material can be act as absorber for solid-state lasers.

  7. Dual-wavelength pump-probe microscopy analysis of melanin composition

    PubMed Central

    Thompson, Andrew; Robles, Francisco E.; Wilson, Jesse W.; Deb, Sanghamitra; Calderbank, Robert; Warren, Warren S.

    2016-01-01

    Pump-probe microscopy is an emerging technique that provides detailed chemical information of absorbers with sub-micrometer spatial resolution. Recent work has shown that the pump-probe signals from melanin in human skin cancers correlate well with clinical concern, but it has been difficult to infer the molecular origins of these differences. Here we develop a mathematical framework to describe the pump-probe dynamics of melanin in human pigmented tissue samples, which treats the ensemble of individual chromophores that make up melanin as Gaussian absorbers with bandwidth related via Frenkel excitons. Thus, observed signals result from an interplay between the spectral bandwidths of the individual underlying chromophores and spectral proximity of the pump and probe wavelengths. The model is tested using a dual-wavelength pump-probe approach and a novel signal processing method based on gnomonic projections. Results show signals can be described by a single linear transition path with different rates of progress for different individual pump-probe wavelength pairs. Moreover, the combined dual-wavelength data shows a nonlinear transition that supports our mathematical framework and the excitonic model to describe the optical properties of melanin. The novel gnomonic projection analysis can also be an attractive generic tool for analyzing mixing paths in biomolecular and analytical chemistry. PMID:27833147

  8. Dual-wavelength pump-probe microscopy analysis of melanin composition

    NASA Astrophysics Data System (ADS)

    Thompson, Andrew; Robles, Francisco E.; Wilson, Jesse W.; Deb, Sanghamitra; Calderbank, Robert; Warren, Warren S.

    2016-11-01

    Pump-probe microscopy is an emerging technique that provides detailed chemical information of absorbers with sub-micrometer spatial resolution. Recent work has shown that the pump-probe signals from melanin in human skin cancers correlate well with clinical concern, but it has been difficult to infer the molecular origins of these differences. Here we develop a mathematical framework to describe the pump-probe dynamics of melanin in human pigmented tissue samples, which treats the ensemble of individual chromophores that make up melanin as Gaussian absorbers with bandwidth related via Frenkel excitons. Thus, observed signals result from an interplay between the spectral bandwidths of the individual underlying chromophores and spectral proximity of the pump and probe wavelengths. The model is tested using a dual-wavelength pump-probe approach and a novel signal processing method based on gnomonic projections. Results show signals can be described by a single linear transition path with different rates of progress for different individual pump-probe wavelength pairs. Moreover, the combined dual-wavelength data shows a nonlinear transition that supports our mathematical framework and the excitonic model to describe the optical properties of melanin. The novel gnomonic projection analysis can also be an attractive generic tool for analyzing mixing paths in biomolecular and analytical chemistry.

  9. Simultaneous determination of Cinnarizine and Domperidone by area under curve and dual wavelength spectrophotometric methods.

    PubMed

    Abdelrahman, Maha M

    2013-09-01

    Accurate, selective and sensitive spectrophotometric methods have been developed and validated for simultaneous determination of Cinnarizine and Domperidone, a binary mixture with overlapping spectra, without preliminary separation. These methods include area under the curve (AUC) and dual wavelength spectrophotometry. For the AUC method, the area under curve of mixture solutions in the wavelength ranges 241-258 nm and 280-292 nm were selected for determination of Cinnarizine and Domperidone and by applying Cramer's rule, concentration of each drug was obtained. In dual wavelength method, two wavelengths were selected for each drug in a way so that the difference in absorbance is zero for another drug. Domperidone shows equal absorbance at 240.2 nm and 273.2 nm, where the differences in absorbance were measured for the determination of Cinnarizine. Similarly, differences in absorbance at 230.8 nm and 259.2 nm were measured for determination of Domperidone. The proposed methods were applied for determination of Cinnarizine and Domperidone over the concentration ranges of 2-20 and 2-22 μg mL(-1), respectively. The suggested methods were validated as per USP guidelines and the results revealed that they are reliable, reproducible and precise for routine use with short analysis time. The results obtained by the proposed methods were statistically compared to the reported method, and there was no significant difference between them regarding both accuracy and precision.

  10. Dual-wavelength retinal images denoising algorithm for improving the accuracy of oxygen saturation calculation

    NASA Astrophysics Data System (ADS)

    Xian, Yong-Li; Dai, Yun; Gao, Chun-Ming; Du, Rui

    2017-01-01

    Noninvasive measurement of hemoglobin oxygen saturation (SO2) in retinal vessels is based on spectrophotometry and spectral absorption characteristics of tissue. Retinal images at 570 and 600 nm are simultaneously captured by dual-wavelength retinal oximetry based on fundus camera. SO2 is finally measured after vessel segmentation, image registration, and calculation of optical density ratio of two images. However, image noise can dramatically affect subsequent image processing and SO2 calculation accuracy. The aforementioned problem remains to be addressed. The purpose of this study was to improve image quality and SO2 calculation accuracy by noise analysis and denoising algorithm for dual-wavelength images. First, noise parameters were estimated by mixed Poisson-Gaussian (MPG) noise model. Second, an MPG denoising algorithm which we called variance stabilizing transform (VST) + dual-domain image denoising (DDID) was proposed based on VST and improved dual-domain filter. The results show that VST + DDID is able to effectively remove MPG noise and preserve image edge details. VST + DDID is better than VST + block-matching and three-dimensional filtering, especially in preserving low-contrast details. The following simulation and analysis indicate that MPG noise in the retinal images can lead to erroneously low measurement for SO2, and the denoised images can provide more accurate grayscale values for retinal oximetry.

  11. Switchable single-polarization dual-wavelength TDFL using PM Fabry-Perot filter

    NASA Astrophysics Data System (ADS)

    Liu, Shuo; Yan, Fengping; Liu, Peng; Zhang, Luna; Bai, Zhuoya; Yin, Bin; Zhou, Hong

    2016-05-01

    A switchable single-polarization (SP), dual-wavelength thulium-doped fiber laser using polarization maintaining (PM) Fabry-Perot (F-P) filter is proposed. A combination of the PM F-P filter, a polarization controller (PC) and a polarizer is used to ensure the SP lasing operation. A stable dual-wavelength lasing operation is obtained at 1941.82 nm and 1942.21 nm. By adjusting the PCs, the proposed laser can achieve SP single-wavelength lasing operation; the polarization extinction ratios are higher than 33 dB. When the pump power is higher than 2.98 W, the optical signal-to-noise ratios of the SP single-wavelength operation can reach 60 dB, and the output power variations are less than 0.32 dB (X-polarization) and 0.30 dB (Y-polarization). The slope efficiencies of SP lasing operation are 6.26% (X-polarization) and 8.79% (Y-polarization), respectively.

  12. Radiometric Calibration of a Dual-Wavelength, Full-Waveform Terrestrial Lidar.

    PubMed

    Li, Zhan; Jupp, David L B; Strahler, Alan H; Schaaf, Crystal B; Howe, Glenn; Hewawasam, Kuravi; Douglas, Ewan S; Chakrabarti, Supriya; Cook, Timothy A; Paynter, Ian; Saenz, Edward J; Schaefer, Michael

    2016-03-02

    Radiometric calibration of the Dual-Wavelength Echidna(®) Lidar (DWEL), a full-waveform terrestrial laser scanner with two simultaneously-pulsing infrared lasers at 1064 nm and 1548 nm, provides accurate dual-wavelength apparent reflectance (ρ(app)), a physically-defined value that is related to the radiative and structural characteristics of scanned targets and independent of range and instrument optics and electronics. The errors of ρ(app) are 8.1% for 1064 nm and 6.4% for 1548 nm. A sensitivity analysis shows that ρ(app) error is dominated by range errors at near ranges, but by lidar intensity errors at far ranges. Our semi-empirical model for radiometric calibration combines a generalized logistic function to explicitly model telescopic effects due to defocusing of return signals at near range with a negative exponential function to model the fall-off of return intensity with range. Accurate values of ρ(app) from the radiometric calibration improve the quantification of vegetation structure, facilitate the comparison and coupling of lidar datasets from different instruments, campaigns or wavelengths and advance the utilization of bi- and multi-spectral information added to 3D scans by novel spectral lidars.

  13. Radiometric Calibration of a Dual-Wavelength, Full-Waveform Terrestrial Lidar

    PubMed Central

    Li, Zhan; Jupp, David L. B.; Strahler, Alan H.; Schaaf, Crystal B.; Howe, Glenn; Hewawasam, Kuravi; Douglas, Ewan S.; Chakrabarti, Supriya; Cook, Timothy A.; Paynter, Ian; Saenz, Edward J.; Schaefer, Michael

    2016-01-01

    Radiometric calibration of the Dual-Wavelength Echidna® Lidar (DWEL), a full-waveform terrestrial laser scanner with two simultaneously-pulsing infrared lasers at 1064 nm and 1548 nm, provides accurate dual-wavelength apparent reflectance (ρapp), a physically-defined value that is related to the radiative and structural characteristics of scanned targets and independent of range and instrument optics and electronics. The errors of ρapp are 8.1% for 1064 nm and 6.4% for 1548 nm. A sensitivity analysis shows that ρapp error is dominated by range errors at near ranges, but by lidar intensity errors at far ranges. Our semi-empirical model for radiometric calibration combines a generalized logistic function to explicitly model telescopic effects due to defocusing of return signals at near range with a negative exponential function to model the fall-off of return intensity with range. Accurate values of ρapp from the radiometric calibration improve the quantification of vegetation structure, facilitate the comparison and coupling of lidar datasets from different instruments, campaigns or wavelengths and advance the utilization of bi- and multi-spectral information added to 3D scans by novel spectral lidars. PMID:26950126

  14. Fast and sensitive optical toxicity bioassay based on dual wavelength analysis of bacterial ferricyanide reduction kinetics.

    PubMed

    Pujol-Vila, F; Vigués, N; Díaz-González, M; Muñoz-Berbel, X; Mas, J

    2015-05-15

    Global urban and industrial growth, with the associated environmental contamination, is promoting the development of rapid and inexpensive general toxicity methods. Current microbial methodologies for general toxicity determination rely on either bioluminescent bacteria and specific medium solution (i.e. Microtox(®)) or low sensitivity and diffusion limited protocols (i.e. amperometric microbial respirometry). In this work, fast and sensitive optical toxicity bioassay based on dual wavelength analysis of bacterial ferricyanide reduction kinetics is presented, using Escherichia coli as a bacterial model. Ferricyanide reduction kinetic analysis (variation of ferricyanide absorption with time), much more sensitive than single absorbance measurements, allowed for direct and fast toxicity determination without pre-incubation steps (assay time=10 min) and minimizing biomass interference. Dual wavelength analysis at 405 (ferricyanide and biomass) and 550 nm (biomass), allowed for ferricyanide monitoring without interference of biomass scattering. On the other hand, refractive index (RI) matching with saccharose reduced bacterial light scattering around 50%, expanding the analytical linear range in the determination of absorbent molecules. With this method, different toxicants such as metals and organic compounds were analyzed with good sensitivities. Half maximal effective concentrations (EC50) obtained after 10 min bioassay, 2.9, 1.0, 0.7 and 18.3 mg L(-1) for copper, zinc, acetic acid and 2-phenylethanol respectively, were in agreement with previously reported values for longer bioassays (around 60 min). This method represents a promising alternative for fast and sensitive water toxicity monitoring, opening the possibility of quick in situ analysis.

  15. Passive Q switching of Er-Yb fiber laser with semiconductor saturable absorber.

    PubMed

    Huang, J Y; Huang, S C; Chang, H L; Su, K W; Chen, Y F; Huang, K F

    2008-03-03

    A high-performance AlGaInAs quantum-well saturable absorber is developed for passively Q-switched Er-Yb double-clad fiber lasers at 1560 nm. With an incident pump power of 13.5 W, an average output power of 1.26 W with a pulse repetition rate of 12 kHz is obtained. The maximum peak power is greater than 500 W.

  16. A graphene passively Q-switched Nd:YAG ceramic laser at 1123 nm

    NASA Astrophysics Data System (ADS)

    Men, Shaojie; Liu, Zhaojun; Zhang, Xingyu; Wang, Qingpu; Shen, Hongbin; Bai, Fen; Gao, Liang; Xu, Xiangang; Wei, Rusheng; Chen, Xiufang

    2013-03-01

    A 1123 nm ceramic Nd:YAG laser passively Q-switched by graphene grown on SiC wafer was demonstrated. With a pump power of 8.1 W, an average output power of 332 mW was obtained, corresponding to an optical-to-optical conversion efficiency of 4.1% and a slope efficiency of 7.8%. The pulse width was 875.7 ns with a pulse repetition rate of 46.8 kHz.

  17. Q-switched pulse laser generation from double-cladding Nd:YAG ceramics waveguides.

    PubMed

    Tan, Yang; Luan, Qingfang; Liu, Fengqin; Chen, Feng; Vázquez de Aldana, Javier Rodríguez

    2013-08-12

    This work reports on the Q-switched pulsed laser generation from double-cladding Nd:YAG ceramic waveguides. Double-cladding waveguides with different combination of diameters were inscribed into a sample of Nd:YAG ceramic. With an additional semiconductor saturable absorber, stable pulsed laser emission at the wavelength of 1064 nm was achieved with pulses of 21 ns temporal duration and ~14 μJ pulse energy at a repetition rate of 3.65 MHz.

  18. Photoconductive semiconductor switches: Laser Q-switch trigger and switch-trigger laser integration

    SciTech Connect

    Loubriel, G.M.; Mar, A.; Hamil, R.A.; Zutavern, F.J.; Helgeson, W.D.

    1997-12-01

    This report provides a summary of the Pulser In a Chip 9000-Discretionary LDRD. The program began in January of 1997 and concluded in September of 1997. The over-arching goal of this LDRD is to study whether laser diode triggered photoconductive semiconductor switches (PCSS) can be used to activate electro-optic devices such as Q-switches and Pockels cells and to study possible laser diode/switch integration. The PCSS switches we used were high gain GaAs switches because they can be triggered with small amounts of laser light. The specific goals of the LDRD were to demonstrate: (1) that small laser diode arrays that are potential candidates for laser-switch integration will indeed trigger the PCSS switch, and (2) that high gain GaAs switches can be used to trigger optical Q-switches in lasers such as the lasers to be used in the X-1 Advanced Radiation Source and the laser used for direct optical initiation (DOI) of explosives. The technology developed with this LDRD is now the prime candidate for triggering the Q switch in the multiple lasers in the laser trigger system of the X-1 Advanced Radiation Source and may be utilized in other accelerators. As part of the LDRD we developed a commercial supplier. To study laser/switch integration we tested triggering the high gain GaAs switches with: edge emitting laser diodes, vertical cavity surface emitting lasers (VCSELs), and transverse junction stripe (TJS) lasers. The first two types of lasers (edge emitting and VCSELs) did activate the PCSS but are harder to integrate with the PCSS for a compact package. The US lasers, while easier to integrate with the switch, did not trigger the PCSS at the US laser power levels we used. The PCSS was used to activate the Q-switch of the compact laser to be used in the X-1 Advanced Radiation Source.

  19. Stress waves generated in thin metallic films by a Q-switched ruby laser

    NASA Technical Reports Server (NTRS)

    Yang, L. C.

    1974-01-01

    Investigation results on stress waves generated by Q-switched ruby laser irradiated thin metal films under confinement, studied over a wide range of film materials and film thicknesses, are reviewed. The results indicate that the dependence on these parameters is much weaker than is predicted by heat transfer estimations commonly used to describe the interaction of laser irradiation with unconfined bulk-solid surfaces.

  20. Clinical efficacy of the dual-pulsed Q-switched neodymium:yttrium-aluminum-garnet laser: Comparison with conservative mode.

    PubMed

    Kim, Byung Wook; Lee, Mi Hye; Chang, Sung Eun; Yun, Woo Jin; Won, Chong Hyun; Lee, Mi Woo; Choi, Jee Ho; Moon, Kee Chan

    2013-12-01

    The quality (Q)-switched neodymium:yttrium-aluminum-garnet (Nd:YAG) laser is one of the first non-ablative lasers to be used for facial resurfacing and photorejuvenation. Recently, the method of low-fluence Q-switched Nd:YAG lasers known as 'laser toning' has been used for non-ablative skin rejuvenation and for the treatment of melasma in Asian countries. We report our experience of using a novel Q-switched Nd:YAG laser that was operated as a dual pulse at half fluence and 140-μs intervals compared with conservative mode laser.

  1. Finite-difference time-domain methods to analyze ytterbium-doped Q-switched fiber lasers.

    PubMed

    Hattori, Haroldo T; Khaleque, Abdul

    2016-03-01

    Q-switched lasers are widely used in material processing, laser ranging, medicine, and nonlinear optics--in particular, Q-switched lasers in optical fibers are important since they cannot only generate high peak powers but can also concentrate high peak powers in small areas. In this paper, we present new finite-difference time-domain methods that analyze the dynamics of Q-switched fiber lasers, which are more flexible and robust than previous methods. We extend the method to analyze fiber ring lasers and compare the results with our experiments.

  2. Theoretical calculation and experimental study of acousto-optically Q-switched CO2 laser.

    PubMed

    Xie, Jijang; Guo, Ruhai; Li, Dianjun; Zhang, Chuansheng; Yang, Guilong; Geng, Yumin

    2010-06-07

    Using resonator inserted with acousto-optically modulator, the experiments of the compacted CO(2) laser were performed with Q-switch. According to various factors that influenced the output of laser, the theoretical calculation of its main parameters was conducted by Q-switched pulsed laser rate equations. Based on the results, the technical route and approach were presented for optimization design of this laser. The measured peak power of this laser device was more than 4000W and pulsed width was 180ns which agreed well with the theoretical calculation. The range of repetition frequency could adjust from 1 Hz to 100 kHz. The theoretical analyzes and experimental results showed that the acoustic traveling time of ultrasonic field could not influence the pulse width of laser so that it did not require inserting optical lens in the cavity to reduce the diameter of beam. The acoustic traveling time only extended the establishingtime of laser pulse. The optimum working frequency of laser is about 1 kHz, which it matched with the radiation life time (1 ms) of CO(2) molecular upper energy level. When the frequency is above 1 kHz, the pulse width of laser increased with the frequency. The full band of wavelength tuning between 9.2 microm and 10.8 microm was obtained by grating selection one by one which the measured spectrum lines were over 30 in the condition of Q-switch.

  3. Study on a new type of electro-optical Q-switch of Langasite crystal

    NASA Astrophysics Data System (ADS)

    Ding, Yunfeng; Qiao, Liang; Diao, Zhi; Xie, Haorui; Jia, Zhe; Li, Yeqiu

    2005-12-01

    A new type of electro-optical Q-switch of Langasite (La 3Ga 5SiO 14,LGS) single crystal is introduced in this paper. LGS has been used as a type of piezoelectric crystal for a long time. It has attracted much attention due to its low acoustic velocity, zero temperature. We make a kind of electro-optical Q-switch of LGS single crystal by using its typically optical activity. LGS is compared with a common type of electric-optical crystal DKDP and LN. LGS has some characteristics that DKDP and LN don't have. For example, LGS is non-deliquescent and can be exposed in the air. It can be coated on the end faces. This helps to increase the transmissivity obviously. But DKDP is deliquescent. The packaging technologies are more complex. The application of DKDP is inconvenient. The anti-damaged threshold of LGS is about 900 MW/cm2. It is much higher than LN. A new set of experimental system was developed based on the characteristics of LGS, including Pockels' cell for LGS driving circuit, Q-switch circuit, etc. The detailed experimental data and oscillograms with this system is got and practical conclusion is made from the experiment. Due to the particular characters of LGS, it has vast application, especially in military realm.

  4. Efficient graphene Q switching and mode locking of 1.34 μm neodymium lasers.

    PubMed

    Xu, Jin-Long; Li, Xian-Lei; He, Jing-Liang; Hao, Xiao-Peng; Yang, Ying; Wu, Yong-Zhong; Liu, Shan-De; Zhang, Bai-Tao

    2012-07-01

    We demonstrate that few-layered graphene sheets used as a saturable absorber can provide efficient Q-switching and mode-locking modulation in 1.34 μm Nd:GdVO(4) bulk lasers. The minimum Q-switched pulses were 450 ns for 260 mW average power, 43 kHz repetition rate, and 2.5 μJ pulse energy. For the mode-locked laser, an average power of 1.29 W was achieved with 11 ps pulse duration and 13 nJ pulse energy. To our knowledge, this average power is the highest yet obtained from a graphene mode-locked laser, and the corresponding optical-optical efficiency of 23% is the best result among 1.3 μm neodymium mode-locked lasers. The quality factor M(2) of the Q-switched beam was 1.4 and 1.6 in the horizontal and longitudinal planes, respectively, and the M(2) of the mode-locked beam reached 1.1 and 1.0. These results clearly indicate the advantages of few-layered graphene as a saturable absorber.

  5. Multi-Billion Shot, High-Fluence Exposure of Cr(4+): YAG Passive Q-Switch

    NASA Technical Reports Server (NTRS)

    Stephen, Mark A.; Dallas, Joseph L.; Afzal, Robert S.

    1997-01-01

    NASA's Goddard Space Flight Center is developing the Geoscience Laser Altimeter System (GLAS) employing a diode pumped, Q-Switched, ND:YAG laser operating at 40 Hz repetition rate. To meet the five-year mission lifetime goal, a single transmitter would accumulate over 6.3 billion shots. Cr(4+):YAG is a promising candidate material for passively Q-switching the laser. Historically, the performance of saturable absorbers has degraded over long-duration usage. To measure the multi-billion shot performance of Cr(4+):YAG, a passively Q-switched GLAS-like oscillator was tested at an accelerated repetition rate of 500 Hz. The intracavity fluence was calculated to be approximately 2.5 J/cm(exp 2). The laser was monitored autonomously for 165 days. There was no evidence of change in the material optical properties during the 7.2 billion shot test.. All observed changes in laser operation could be attributed to pump laser diode aging. This is the first demonstration of multi-billion shot exposure testing of Cr(4+):YAG in this pulse energy regime

  6. Passively Q-switched waveguide lasers based on two-dimensional transition metal diselenide.

    PubMed

    Cheng, Chen; Liu, Hongliang; Tan, Yang; Vázquez de Aldana, Javier R; Chen, Feng

    2016-05-16

    We reported on the passively Q-switched waveguide lasers based on few-layer transition metal diselenide, including molybdenum diselenide (MoSe2) and tungsten diselenide (WSe2), as saturable absorbers. The MoSe2 and WSe2 membranes were covered on silica wafers by chemical vapor deposition (CVD). A low-loss depressed cladding waveguide was produced by femtosecond laser writing in a Nd:YAG crystal. Under optical pump at 808 nm, the passive Q-switching of the Nd:YAG waveguide lasing at 1064 nm was achieved, reaching maximum average output power of 115 mW (MoSe2) and 45 mW (WSe2), respectively, which are corresponding to single-pulse energy of 36 nJ and 19 nJ. The repetition rate of the Q-switched waveguide lasers was tunable from 0.995 to 3.334 MHz (MoSe2) and 0.781 to 2.938 MHz (WSe2), and the obtained minimum pulse duration was 80ns (MoSe2) and 52 ns (WSe2), respectively.

  7. Self-Q-switching behavior of erbium-doped tellurite microstructured fiber lasers

    SciTech Connect

    Jia, Zhi-Xu; Yao, Chuan-Fei; Kang, Zhe; Qin, Guan-Shi Qin, Wei-Ping; Ohishi, Yasutake

    2014-06-14

    We reported self-Q-switching behavior of erbium-doped tellurite microstructured fiber (EDTMF) lasers and further demonstrated a self-Q-switched EDTMF laser with a high repetition rate of more than 1 MHz. A 14 cm EDTMF was used as the gain medium. Upon a pump power of ∼705 mW at 1480 nm, output pulses with a lasing wavelength of ∼1558 nm, a repetition rate of ∼1.14 MHz, and a pulse width of ∼282 ns were generated from the fiber by employing a linear cavity. The maximum output power was ∼316 mW and the slope efficiency was about 72.6% before the saturation of the laser power. Moreover, the influence of the fiber length on laser performances was investigated. The results showed that self-Q-switching behavior in our experiments was caused by the re-absorption originated from the ineffectively pumped part of the active fiber.

  8. Ag-nanoparticle as a Q switched device for tunable C-band fiber laser

    NASA Astrophysics Data System (ADS)

    Ahmad, H.; Ruslan, N. E.; Ali, Z. A.; Reduan, S. A.; Lee, C. S. J.; Shaharuddin, R. A.; Nayan, N.; Ismail, M. A.

    2016-12-01

    The use of silver (Ag)-nanoparticle as saturable absorber (SA) to induce tunable Q-switched fiber laser in C-band is demonstrated. The Ag-nanoparticle SA exhibits modulation depth of 31.6% and saturation intensity of 0.54 MW cm-2. The SA is integrated into the laser cavity by sandwiching it between two fiber ferrules. Lasing in CW region starts at 10 mW, whereas stable self-starting Q-switching with a central wavelength of 1558.4 nm begins at 20 mW. As the pump power increases, the repetition rate varies from 10.5 kHz to 24.4 kHz and the narrowest pulse width obtained is around 6.5 μs. The Q-switched laser has a tuning range of 27.3 nm (1552.9-1580.2 nm). The stability of the pulse is verified from the radio-freqeuncy (RF) spectrum with a measured signal-to-noise ratio (SNR) of 46.22 dB. The ability of Ag-nanoparticle as an effective SA may lead to further development of pulsed fiber laser in the field of photonics.

  9. High precision materials processing using a novel Q-switched CO2 laser

    NASA Astrophysics Data System (ADS)

    Gräf, Stephan; Staupendahl, Gisbert; Krämer, André; Müller, Frank A.

    2015-03-01

    Holes with diameters of about 400 μm have been laser trepanned in Ti6Al4V and carbon fibre reinforced polymer (CFRP) thin sheets with a thickness of 0.5 mm. A commercial CO2 laser (SM1500E, FEHA LaserTec, Germany) and a novel Q-switched CO2 laser (μ-storm, IAI, Netherlands) were used as radiation sources. Optical microscopy, scanning electron microscopy and replicas of the processed holes were used to investigate the influence of the CO2 laser pulse parameters (e.g. pulse energy, duration and peak power) on the processing quality. It was shown that melt formation and high temperature oxidation reactions of Ti6Al4V during thermal laser processing were reduced significantly by using short and high intense Q-switched CO2 laser pulses. During trepanning of CFRP heat affected zones resulting from the extremely different thermal properties (melting and vaporisation temperature, heat conduction) of the reinforcing carbon fibres and the polymer matrix were reduced significantly by using the Q-switched CO2 laser. The results demonstrate that Ti6Al4V and CFRP can be processed very precisely with CO2 laser radiation and air as processing gas without melt formation and thermal damage.

  10. Study on the output of LD-pumped passively Q-switched subnanosecond microlasers

    NASA Astrophysics Data System (ADS)

    Cheng, He-jiao; Chen, Hui-min; Ding, Bo-sheng; Cai, De

    2013-09-01

    Caliber mortar projectiles and bombs are now tend to use the laser fuze because of its high accuracy in distance measurement,the strong ability to resist electromagnetic interference, the high angular resolution and the good concealment. Otherwise, the microlaser can bring about some alluring benefits. For instance, it can generate high quality laser beam, which has small divergence angle and high power. So, This paper summarizes some key factors which have impacts on the output of LD-pumped passively Q-switched subnanosecond microlasers, including the initial transmission of the absorber, the reflection of output coupler, the length of the cavity and the radius of the pumping laser beam, and gives the conclusion of the simulation based on the variation of the density of the reversal particle in the resonant cavity derived from the oscillation equation of the LD-pumped passively Q-switched Cr4+:YAG/ Nd:YAG laser, which provides the basis for the design of the passive Q-switched micro lasers which have high power, high repetition frequency and narrow pulse width.

  11. Passively Q-switched diode-pumped Yb:YAG laser using Cr 4+-doped garnets

    NASA Astrophysics Data System (ADS)

    Kalisky, Y.; Labbe, C.; Waichman, K.; Kravchik, L.; Rachum, U.; Deng, P.; Xu, J.; Dong, J.; Chen, W.

    2002-06-01

    We investigate the repetitive modulation in the kHz frequency domain of a passively Q-switched, diode-pumped Yb:YAG laser, by Cr 4+:YAG, Cr 4+:LuAG, and Cr 4+:GSGG saturable absorbers. The results presented here are focused towards the design of a passively Q-switched Yb:YAG microlaser. The free-running performance of both rod and a disk Yb:YAG is characterized and experimental parameters such as gain and loss are evaluated. These values, together with the value of the stimulated emission cross-section, e.g. σem=3.3×10 -20 cm 2 were found to fit between our experimental results and an existing numerical model which relates the experimental and physical parameters to the minimal threshold pumping power. Q-switched pulses with maximum peak power of ≈10.4 kW, with energy of ≈0.5 mJ/pulse, were extracted with 30% extraction efficiency.

  12. Narrow-linewidth Q-switched random distributed feedback fiber laser.

    PubMed

    Xu, Jiangming; Ye, Jun; Xiao, Hu; Leng, Jinyong; Wu, Jian; Zhang, Hanwei; Zhou, Pu

    2016-08-22

    A narrow-linewidth Q-switched random fiber laser (RFL) based on a half-opened cavity, which is realized by narrow-linewidth fiber Bragg grating (FBG) and a section of 3 km passive fiber, has been proposed and experimentally investigated. The narrow-linewidth lasing is generated by the spectral filtering of three FBGs with linewidth of 1.21 nm, 0.56 nm, and 0.12 nm, respectively. The Q switching of the distributed cavity is achieved by placing an acousto-optical modulator (AOM) between the FBG and the passive fiber. The maximal output powers of the narrow-linewidth RFLs with the three different FBGs are 0.54 W, 0.27 W, and 0.08 W, respectively. Furthermore, the repetition rates of the output pulses are 500 kHz, and the pulse durations are about 500 ns. The corresponding pulse energies are about 1.08 μJ, 0.54 μJ, and 0.16 μJ, accordingly. The linewidth of FBG can influence the output characteristics in full scale. The narrower the FBG, the higher the pump threshold; the lower the output power at the same pump level, the more serious the linewidth broadening; and thus the higher the proportion of the CW-ground exists in the output pulse trains. Thanks to the assistance of the band-pass filter (BPF), the proportion of the CW-ground of narrow-linewidth Q-switched RFL under the relative high-pump-low-output condition can be reduced effectively. The experimental results indicate that it is challenging to demonstrate a narrow-linewidth Q-switched RFL with high quality output. But further power scaling and linewidth narrowing is possible in the case of operating parameters, optimization efforts, and a more powerful pump source. To the best of our knowledge, this is the first demonstration of narrow-linewidth generation in a Q-switched RFL.

  13. Minimization of thermomechanical side effects in IR ablation by use of Q-switched double pulses

    NASA Astrophysics Data System (ADS)

    Vogel, Alfred; Schmidt, Peter; Flucke, Barbara

    2001-07-01

    Holmium laser pulses (λ= 2.1 m) are often used for medical laser applications inside the human body, because they can be transmitted through low-OH quartz fibers, and they are relatively well absorbed in water and biological tissues. However, large thermal damage zones were observed after application of free-running holmium laser pulses for arthroscopic surgery. The aim of our study is to reduce thermal damage without introducing additional mechanical damage and without impairing the hemostatic action of the laser radiation. For that purpose we use double pulses from a custom-made acousto-optically Q- switched thulium laser (λ = 2.0 μm) that can emit pulses with energies of up to 150 mJ. The penetration depth of the thulium laser radiation (170 μm) as well as the thermal damage zone are only half as large as that of the holmium laser. The use of Q-switched pulses creates stress confinement conditions leading to a more efficient ablation than with free running pulses. For a given ablation depth, the residual heat deposited in the tissue is therefore smaller than with free running pulses and, hence, also the thermal damage zone. This reduction of thermal damage is possible even though the free-running pulses already fulfil the condition for thermal confinement. The thermal damage zone was only 100 μm for the Q-switched thulium pulses but 200 μm for the free-running pulses. The degree of thermal damage was, in addition, much more severe for the free-running pulses. Q-switched pulses lead to an explosive ablation of the target material. In a liquid environment, this gives rise to the formation of cavitation effects, we release a pre-pulse with small energy (40 mJ) before each ablation pulse of up to 150 mJ. The pre-pulse produces a small cavity that is then filled by the ablation products of the main pulse. The ablation pulse is emitted about 100 μs after the pre-pulse when the bubble is maximally expanded. This way, no additional cavitation effects are induced

  14. Characterization of the Q-switched MOBLAS Laser Transmitter and Its Ranging Performance Relative to a PTM Q-switched System

    NASA Technical Reports Server (NTRS)

    Degnan, J. J., III; Zagwodski, T. W.

    1979-01-01

    A prototype Q-switched Nd:YAG laser transmitter intended for use in the NASA mobile laser ranging system was subjected to various tests of temporal pulse shape and stability, output energy and stability, beam divergence, and range bias errors. Peak to peak variations in the mean range were as large as 30 cm and drift rates of system bias with time as large as 6 mm per minute of operation were observed. The incorporation of a fast electro-optic cavity dump into the oscillator gave significantly improved results. Reevaluation of the ranging performance after modification showed a reduction in the peak to peak variation in the mean range to the 2 or 3 cm level and a drift rate of system time biases of less than 1 mm per minute of operation. A qualitative physical explanation for the superior performance of cavity dumped lasers is given.

  15. Passively Q-switched flashlamp pumped Nd:YAG laser using liquid graphene oxide as saturable absorber

    NASA Astrophysics Data System (ADS)

    Adnan, N. N.; Bidin, N.; Taib, N. A. M.; Haris, H.; Fakaruddin, M.; Hashim, A. M.; Krishnan, G.; Harun, S. W.

    2016-06-01

    The performance of passively Q-switched Nd:YAG laser operating at 1060 nm is demonstrated using liquid graphene oxide (GO) composite solution as saturable absorber for the first time. The Q-switched Nd:YAG laser is pumped by a xenon flashlamp. The GO was prepared using the simplified Hummer's method and then mixed with polyethylene oxide to form a composite solution. The Q-switched pulsed laser operates at wavelength of 1064.5 nm with a threshold pump energy of 33.64 J. The maximum output Q-switched laser energy of 41.6 mJ achieved at the maximum pump energy of 81 J. The corresponding pulse width is 98.67 ns.

  16. Dual-loss-modulated Q-switched Tm:LuAG laser with AOM and monolayer graphene.

    PubMed

    Luan, Chao; Yang, Ke Jian; Zhao, Jia; Zhao, Sheng Zhi; Qiao, Wen Chao; Li, Tao; Feng, Tian Li; Liu, Cheng; Qiao, Jun Peng; Zheng, Li He; Xu, Jun; Wang, Qing Guo; Su, Liang Bi

    2015-09-20

    A laser-diode-pumped dual-loss-modulated Q-switching Tm:LuAG laser with an acousto-optic modulator (AOM) and monolayer graphene saturable absorber (SA) around 2 μm is presented for the first time to the best of our knowledge. The average output power and the pulse widths for different repetition rates have been measured. In comparison with the singly Q-switching laser with AOM or with monolayer graphene SA, the dual-loss-modulated Q-switching laser could generate shorter pulse width and higher peak power. The maximum pulse width compression ratio was found to be 3.11, and the highest peak power was enhanced 97.4 times. The experimental results show that the dual-loss-modulated technology is an efficient method for compressing the pulse width, improving the peak power, and enhancing the pulse stability for the Q-switched lasers at 2 μm.

  17. Methods of Attenuation Correction for Dual-Wavelength and Dual-Polarization Weather Radar Data

    NASA Technical Reports Server (NTRS)

    Meneghini, R.; Liao, L.

    2007-01-01

    In writing the integral equations for the median mass diameter and number concentration, or comparable parameters of the raindrop size distribution, it is apparent that the forms of the equations for dual-polarization and dual-wavelength radar data are identical when attenuation effects are included. The differential backscattering and extinction coefficients appear in both sets of equations: for the dual-polarization equations, the differences are taken with respect to polarization at a fixed frequency while for the dual-wavelength equations, the differences are taken with respect to frequency at a fixed polarization. An alternative to the integral equation formulation is that based on the k-Z (attenuation coefficient-radar reflectivity factor) parameterization. This-technique was originally developed for attenuating single-wavelength radars, a variation of which has been applied to the TRMM Precipitation Radar data (PR). Extensions of this method have also been applied to dual-polarization data. In fact, it is not difficult to show that nearly identical equations are applicable as well to dualwavelength radar data. In this case, the equations for median mass diameter and number concentration take the form of coupled, but non-integral equations. Differences between this and the integral equation formulation are a consequence of the different ways in which attenuation correction is performed under the two formulations. For both techniques, the equations can be solved either forward from the radar outward or backward from the final range gate toward the radar. Although the forward-going solutions tend to be unstable as the attenuation out to the range of interest becomes large in some sense, an independent estimate of path attenuation is not required. This is analogous to the case of an attenuating single-wavelength radar where the forward solution to the Hitschfeld-Bordan equation becomes unstable as the attenuation increases. To circumvent this problem, the

  18. Tunable Terahertz-wave generation from DAST crystal pumped by a monolithic dual-wavelength fiber laser.

    PubMed

    Tang, Ming; Minamide, Hiroaki; Wang, Yuye; Notake, Takashi; Ohno, Seigo; Ito, Hiromasa

    2011-01-17

    For developing a continuous-wave (CW) tunable Terahertz-wave (THz-wave) source using difference-frequency generation (DFG) in highly nonlinear optical crystals, we proposed and demonstrated a dual-wavelength fiber ring laser system operating around 1060 nm based on wideband chirped fiber Bragg gratings (CFBGs) and semiconductor optical amplifier (SOA). Thermo-induced phase shift along the CFBG produces a very sharp transmission spike therefore two lasing wavelengths with single longitudinal mode operation are oscillating simultaneously within the fiber ring cavity. Due to the inhomogeneous gain broadening property of SOA, the wavelength spacing of our dual-wavelength fiber laser can be continuously adjusted from 0.3 to 9.5 nm. By using this single emitter dual-wavelength fiber laser to pump an organic nonlinear DAST crystal, type-0 collinear phase matching of DFG process can be fulfilled and monochromatic THz wave ranging from 0.5 to 2 THz has been successfully generated.

  19. Simultaneous dual-wavelength eye-safe KTP OPO intracavity pumped by a Nd:GYSGG laser

    NASA Astrophysics Data System (ADS)

    Wang, Maorong; Zhong, Kai; Mei, Jialin; Guo, Shibei; Xu, Degang; Yao, Jianquan

    2016-02-01

    A simultaneous dual-wavelength intracavity pumped non-critical eye-safe optical parametric oscillator (OPO) is realized using a Nd:GYSGG laser crystal and a KTP nonlinear crystal. A folded cavity is used for thermal stability and mode matching, which greatly improves the output characteristics versus a linear cavity. The maximum output power of the 1562.1 nm/1567.4 nm dual-wavelength eye-safe laser is 750 mW at 10 kHz, corresponding to the optical-to-optical conversion efficiency, single-pulse-energy and peak power of 5.8%, 75 μJ and 22.7 kW. Such a dual-wavelength OPO provides a good laser source for remote sensing for CO and CO2 gases or difference frequency generation for terahertz wave at the important 0.65 THz band.

  20. Orthogonally polarized dual-wavelength Nd:LuVO4 laser at 1086 nm and 1089 nm.

    PubMed

    Huang, Y P; Cho, C Y; Huang, Y J; Chen, Y F

    2012-02-27

    A comparison between the fluorescence spectra of the Nd-doped vanadate crystals (Nd:YVO4, Nd:GdVO4, Nd:LuVO4) for the 4F3/2 → 4I11/2 transition is studied. We numerically analyze the condition of gain-to-loss balance via an uncoated intracavity etalon to achieve the dual-wavelength operation. We further experimentally demonstrate the orthogonally polarized dual-wavelength laser with a single Nd:LuVO4 crystal. The simultaneous dual-wavelength Nd:LuVO4 laser at 1085.7 nm in σ polarization and 1088.5 nm in π polarization is realized. At an incident pump power of 12 W, the average output power obtained at 1085.7 nm and 1088.5 nm is 0.4 W and 1.7 W, respectively.

  1. On the possibility of a new passively Q-switched laser operation mode with periodic wavelength switching

    SciTech Connect

    Fedorov, A V; Fomichev, A A; Doroshenko, M E

    2015-06-30

    The possibility of cw-pumped passively Q-switched laser operation has been examined theoretically. Also, we have proposed laser operation mode in which the output wavelength automatically switches between two values without any changes in cavity parameters. Using numerical simulation and an Er:YAG laser with a Co:ZnSe passive Q-switch as an example, we have found parameters that ensure such operation mode. (lasers)

  2. Experimental demonstration of a passive all-fiber Q-switched erbium- and samarium-doped laser.

    PubMed

    Preda, Cristina Elena; Ravet, Gautier; Mégret, Patrice

    2012-02-15

    Self-Q-switched operation of the all-fiber laser using erbium and samarium fibers in the cavity is realized experimentally. This passively Q-switched all-fiber laser produces very stable pulses with energy of 142 nJ and duration of 450 ns. The experimental results were well reproduced by the results obtained through the numerical integration of a rate-equations model.

  3. A self-Q-switched all-fiber erbium laser at 1530 nm using an auxiliary 1570-nm erbium laser.

    PubMed

    Tsai, Tzong-Yow; Fang, Yen-Cheng

    2009-11-23

    We demonstrate a self-Q-switched, all-fiber, tunable, erbium laser at 1530 nm with high pulse repetition rates of 0.9-10 kHz. Through the use of an auxiliary 10-mW, 1570 nm laser that shortened the relaxation time of erbium, sequentially Q-switched pulses with pulse energies between 4 and 6 microJ and pulse widths of 40 ns were steadily achieved. A peak pulse power of 165 W was obtained.

  4. Q-switching of a thulium-doped fibre laser using a holmium-doped fibre saturable absorber

    SciTech Connect

    Sadovnikova, Ya E; Kamynin, V A; Kurkov, A S; Medvedkov, O I; Marakulin, A V; Minashina, L A

    2014-01-31

    We have proposed and demonstrated a new passively Q-switched thulium-doped fibre laser configuration. A distinctive feature of this configuration is the use of a heavily holmium-doped fibre for Q-switching. Lasing was obtained at 1.96 μm, with a pulse energy of 3 μJ and pulse duration of 600 ns. The highest pulse repetition rate was 80 kHz. (control of laser radiation parameters)

  5. Efficient energy extraction from a diode-pumped Q-switched Tm,Ho:YLiF4 laser

    NASA Technical Reports Server (NTRS)

    Mcguckin, B. T.; Menzies, R. T.; Hemmati, H.

    1991-01-01

    The operation of a diode-laser pumped thulium, holmium yttrium-lithium-fluoride laser (Tm,Ho:YLF) in Q-switched mode is reported. Output energies of 200 microjoules in pulses of 22 ns duration are recorded at Q-switch frequencies commensurate with an effective upper laser level lifetime of 6 ms. This lifetime is appreciably longer than that observed in other hosts permitting stored energy extraction of 64 percent, close to the projected maximum performance from these materials.

  6. Efficient high repetition rate electro-optic Q-switched laser with an optically active langasite crystal

    PubMed Central

    Ma, Shihui; Yu, Haohai; Zhang, Huaijin; Han, Xuekun; Lu, Qingming; Ma, Changqin; Boughton, Robert I.; Wang, Jiyang

    2016-01-01

    With an optically active langasite (LGS) crystal as the electro-optic Q-switch, we demonstrate an efficient Q-switched laser with a repetition rate of 200 kHz. Based on the theoretical analysis of the interaction between optical activity and electro-optic property, the optical activity of the crystal has no influence on the birefringence during Q-switching if the quarter wave plate used was rotated to align with the polarization direction. With a Nd:LuVO4 crystal possessing a large emission cross-section and a short fluorescence lifetime as the gain medium, a stable LGS Q-switched laser was designed with average output power of 4.39 W, corresponding to a slope efficiency of 29.4% and with a minimum pulse width of 5.1 ns. This work represents the highest repetition rate achieved so far in a LGS Q-switched laser and it can provide a practical Q-switched laser with a tunable high repetition rates for many applications, such as materials processing, laser ranging, medicine, military applications, biomacromolecule materials, remote sensing, etc. PMID:27461819

  7. Gain structuration in dual-wavelength Nd:YSAG ceramic lasers.

    PubMed

    Jaffres, Lionel; Labruyère, Alexis; Couderc, Vincent; Carreaud, Julie; Maître, Alexandre; Boulesteix, Rémi; Brenier, Alain; Boulon, Georges; Guyot, Yannick; Rabinovitch, Yoël; Sallé, Christian

    2012-11-05

    We demonstrate a dual-wavelength Nd:YSAG ceramic laser in which the gain volume is structurated into two different regions providing gain at the wavelength of 1061 nm and 1064 nm respectively. We discuss the role of the nonuniform distribution of the temperature in structurating the gain region via the Boltzmann effect. We show that the two laser wavelengths can be switched by adjusting the size of the pump beam or by slightly modifying the geometrical parameters of the laser cavity, either the length of the cavity or the orientation of a mirror. Additionally, we demonstrate that the transverse modes at the two wavelengths are shaped according to the effect of gain filtering caused by the structuration of the gain region.

  8. Dual-wavelength single-frequency laser emission in asymmetric coupled microdisks

    PubMed Central

    Wang, Haotian; Liu, Sheng; Chen, Lin; Shen, Deyuan; Wu, Xiang

    2016-01-01

    The gain and loss in a microcavity laser play an important role for the modulation of laser spectrum. We show that dual-wavelength single mode lasing can be achieved in an asymmetric coupled system consisted of two size-mismatched microdisks. The amount of eigenmodes in this coupled-microdisk system is reduced relying on the Vernier effect. Then a single mode is selected to lase by controlling the gain branching in the supermodes. The supermodes are formed by the coupling between different transverse whispering-gallery modes (WGMs). When the gain/loss status between the two mirodisks is changed through selectively pumping process, the modulated gain branching for various supermodes leads to the switchable single-frequency laser emission. The results obtained in this work will provide the further understand for the spectral modulation mechanism in the coupled microcavity laser system. PMID:27905506

  9. Tunable microwave generation of a monolithic dual-wavelength distributed feedback laser.

    PubMed

    Lo, Yen-Hua; Wu, Yu-Chang; Hsu, Shun-Chieh; Hwang, Yi-Chia; Chen, Bai-Ci; Lin, Chien-Chung

    2014-06-02

    The dynamic behavior of a monolithic dual-wavelength distributed feedback laser was fully investigated and mapped. The combination of different driving currents for master and slave lasers can generate a wide range of different operational modes, from single mode, period 1 to chaos. Both the optical and microwave spectrum were recorded and analyzed. The detected single mode signal can continuously cover from 15GHz to 50GHz, limited by photodetector bandwidth. The measured optical four-wave-mixing pattern indicates that a 70GHz signal can be generated by this device. By applying rate equation analysis, the important laser parameters can be extracted from the spectrum. The extracted relaxation resonant frequency is found to be 8.96GHz. With the full operational map at hand, the suitable current combination can be applied to the device for proper applications.

  10. Determination of ultra-low milk fat content using dual-wavelength ultraviolet spectroscopy.

    PubMed

    Xiong, Shiqiong; Adhikari, Benu; Chen, Xiao Dong; Che, Liming

    2016-12-01

    A precise determination of milk fat content in dairy products is of great practical importance. Several studies have reported methods to determine the milk fat content in commercial dairy products. However, very few of them validated or tested cases where the fat milk fat content was ultra-low. Here we present an approach to determine ultra-low milk fat content. This method involves extracting milk fat using n-heptane and determining its content using dual-wavelength UV spectroscopy. The results showed that milk fat at ultra-low concentrations (i.e., as low as 0.148 g/L) could be extracted completely and quantified accurately using the proposed approach. This method is reproducible and sufficiently precise. We expect that this method can be adapted by industries to determine ultra-low concentration of fat in milk and other dairy products with confidence.

  11. Dual-wavelength single-frequency laser emission in asymmetric coupled microdisks

    NASA Astrophysics Data System (ADS)

    Wang, Haotian; Liu, Sheng; Chen, Lin; Shen, Deyuan; Wu, Xiang

    2016-12-01

    The gain and loss in a microcavity laser play an important role for the modulation of laser spectrum. We show that dual-wavelength single mode lasing can be achieved in an asymmetric coupled system consisted of two size-mismatched microdisks. The amount of eigenmodes in this coupled-microdisk system is reduced relying on the Vernier effect. Then a single mode is selected to lase by controlling the gain branching in the supermodes. The supermodes are formed by the coupling between different transverse whispering-gallery modes (WGMs). When the gain/loss status between the two mirodisks is changed through selectively pumping process, the modulated gain branching for various supermodes leads to the switchable single-frequency laser emission. The results obtained in this work will provide the further understand for the spectral modulation mechanism in the coupled microcavity laser system.

  12. Dual-wavelength photothermal optical coherence tomography for imaging microvasculature blood oxygen saturation

    PubMed Central

    Yin, Biwei; McElroy, Austin B.; Kazmi, Shams; Dunn, Andrew K.; Duong, Timothy Q.; Milner, Thomas E.

    2013-01-01

    Abstract. A swept-source dual-wavelength photothermal (DWP) optical coherence tomography (OCT) system is demonstrated for quantitative imaging of microvasculature oxygen saturation. DWP-OCT is capable of recording three-dimensional images of tissue and depth-resolved phase variation in response to photothermal excitation. A 1,064-nm OCT probe and 770-nm and 800-nm photothermal excitation beams are combined in a single-mode optical fiber to measure microvasculature hemoglobin oxygen saturation (SO2) levels in phantom blood vessels with a range of blood flow speeds (0 to 17  mm/s). A 50-μm-diameter blood vessel phantom is imaged, and SO2 levels are measured using DWP-OCT and compared with values provided by a commercial oximeter at various blood oxygen concentrations. The influences of blood flow speed and mechanisms of SNR phase degradation on the accuracy of SO2 measurement are identified and investigated. PMID:23640076

  13. Simultaneous dual-wavelength reflection digital holography applied to the study of the porous coal samples.

    PubMed

    Khmaladze, Alexander; Restrepo-Martínez, Alejandro; Kim, Myung; Castañeda, Roman; Blandón, Astrid

    2008-06-10

    We present a simultaneous dual-wavelength phase-imaging digital holographic technique demonstrated on porous coal samples. The use of two wavelengths enables us to increase the axial range at which the unambiguous phase imaging can be performed, but also increases the noise. We employ a noise reduction "fine map" algorithm, which uses the two-wavelength phase map as a guide to correct a single-wavelength phase image. Then, the resulting noise of a fine map is reduced to the level of single-wavelength noise. A comparison to software unwrapping is also presented. A simple way of correcting a curvature mismatch between the reference and the object beams is offered.

  14. Dual wavelength erbium-doped fiber laser using a tapered fiber

    NASA Astrophysics Data System (ADS)

    Harun, S. W.; Lim, K. S.; Jasim, A. A.; Ahmad, H.

    2010-12-01

    A tapered fiber is fabricated by heating and stretching a piece of optical fiber after the polymer protective cladding has been removed. An equidistant comb-like transmission spectrum, with a spacing of 1.6 nm and an extinction ratio of more than 5 dB, was obtained by the tapered fiber due to the multibeam interferences of the cladding modes. The tapered fiber was applied in a ring erbium-doped fiber laser (EDFL) to generate dual-wavelength lasing oscillations. The EDFL operates at wavelengths of 1557.0 nm and 1558.6 nm with a stable peak power and a signal-to-noise ratio of more than 40 dB.

  15. Tunable and switchable dual-wavelength Tm-doped mode-locked fiber laser by nonlinear polarization evolution.

    PubMed

    Yan, Zhiyu; Li, Xiaohui; Tang, Yulong; Shum, Perry Ping; Yu, Xia; Zhang, Ying; Wang, Qi Jie

    2015-02-23

    We propose and demonstrate a tunable and switchable dual-wavelength ultra-fast Tm-doped fiber laser. The tunability is based on nonlinear polarization evolution (NPE) technique in a passively mode-locked laser cavity. The NPE effect induces wavelength-dependent loss in the cavity to effectively alleviate mode competition and enables the multiwavelength mode locking. The laser exhibits tunable dual-wavelength mode locking over a wide range from 1852 to 1886 nm. The system has compact structure and both the wavelength tuning and switching capabilities can be realized by controlling the polarization in the fiber ring cavity.

  16. A switchable dual-wavelength fiber laser based on asymmetric fiber Bragg grating Fabry-Perot cavity with a SESAM

    NASA Astrophysics Data System (ADS)

    Huang, Kaiqiang; Li, Qi; Chen, Haiyan

    2016-04-01

    A switchable dual-wavelength fiber laser with an asymmetric fiber Bragg grating (FBG)-Fabry-Perot (FP) cavity based a semiconductor saturable absorber mirror (SESAM) is proposed and experimentally demonstrated. The proof of concept device consists of a FGB laser with an asymmetric FBG-FP cavity, a SESAM as mode loss modulator, and a intracavity FBG as wavelength selector by changing its operation temperature. The results demonstrate the new concept of dual-wavelength fiber laser based SESAM with asymmetric FBG-FP cavity and the technical feasibility.

  17. Switchable dual-wavelength fiber laser based on semiconductor optical amplifier and polarization-maintaining fiber Bragg grating

    NASA Astrophysics Data System (ADS)

    Feng, Suchun; Xu, Ou; Lu, Shaohua; Ren, Wenhua; Jian, Shuisheng

    2008-12-01

    Switchable dual-wavelength with orthogonal polarizations fiber laser based on semiconductor optical amplifier (SOA) and polarization-maintaining fiber Bragg grating (PMFBG) at room temperature is proposed. Owing to the polarization dependent loss of the PMFBG, the laser can be designed to operate in stable dual-wavelength or wavelength-switching modes with a wavelength spacing of 0.336 nm at room temperature by adjusting the polarization controller (PC). The amplitude variation in nearly half an hour is less than 0.1 dB for both wavelengths, which is more stable than that of erbium doped fiber (EDF)-based laser with similar configuration.

  18. Continuous-wave dual-wavelength operation of a diode-end-pumped Nd:GGG laser

    NASA Astrophysics Data System (ADS)

    Sun, G. C.; Li, Y. D.; Zhao, M.; Jin, G. Y.; Wang, J. B.

    2011-08-01

    A diode-end-pumped continuous-wave (CW) simultaneous dual-wavelength laser operation at 1062 and 1331 nm in a single Nd:GGG was demonstrated. A total output power of 1.08 W at the two fundamental wavelengths was achieved at the incident pump power of 18.2 W. The optical-to-optical conversion is up to 5.9% with respect to the incident pump power. To the best of our knowledge, this is first work on CW simultaneous dual-wavelength operation of a diode pumped Nd:GGG laser. The article is published in the original.)

  19. Simultaneous dual-wavelength laser operation at 937 and 1062 nm in Nd3+:Gd3Ga5O12

    NASA Astrophysics Data System (ADS)

    Gao, F.; Sun, G. C.; Li, Y. D.; Dong, Y.; Li, S. T.

    2013-08-01

    Diode-end-pumped continuous-wave (cw) simultaneous dual-wavelength laser operation at 937 and 1062 nm in a single Nd3+:Gd3Ga5O12 (Nd:GGG) crystal was demonstrated. A total output power of 1.12 W at the two fundamental wavelengths was achieved at incident pump power of 17.6 W. The optical-to-optical conversion was up to 6.4% with respect to the incident pump power. To the best of our knowledge, this is first work on cw simultaneous dual-wavelength operation at 937 and 1062 nm in Nd:GGG crystal.

  20. Switchable single-longitudinal-mode dual-wavelength erbium-doped fiber ring laser incorporating a semiconductor optical amplifier.

    PubMed

    Pan, Shilong; Zhao, Xiaofan; Lou, Caiyun

    2008-04-15

    We propose and demonstrate a novel single-longitudinal-mode (SLM) dual-wavelength erbium-doped fiber ring laser incorporating a semiconductor optical amplifier. The SOA biased in its low-gain regime greatly reduces the gain competition of the two wavelengths. The stable SLM operation is guaranteed by a passive triple-ring cavity and a fiber Fabry-Perot filter. The dual-wavelength output with a 40 GHz wavelength spacing is switchable in the range of 1533-1565.4 nm.

  1. Dual wavelength multiple-angle light scattering system for cryptosporidium detection

    NASA Astrophysics Data System (ADS)

    Buaprathoom, S.; Pedley, S.; Sweeney, S. J.

    2012-06-01

    A simple, dual wavelength, multiple-angle, light scattering system has been developed for detecting cryptosporidium suspended in water. Cryptosporidium is a coccidial protozoan parasite causing cryptosporidiosis; a diarrheal disease of varying severity. The parasite is transmitted by ingestion of contaminated water, particularly drinking-water, but also accidental ingestion of bathing-water, including swimming pools. It is therefore important to be able to detect these parasites quickly, so that remedial action can be taken to reduce the risk of infection. The proposed system combines multiple-angle scattering detection of a single and two wavelengths, to collect relative wavelength angle-resolved scattering phase functions from tested suspension, and multivariate data analysis techniques to obtain characterizing information of samples under investigation. The system was designed to be simple, portable and inexpensive. It employs two diode lasers (violet InGaN-based and red AlGaInP-based) as light sources and silicon photodiodes as detectors and optical components, all of which are readily available. The measured scattering patterns using the dual wavelength system showed that the relative wavelength angle-resolved scattering pattern of cryptosporidium oocysts was significantly different from other particles (e.g. polystyrene latex sphere, E.coli). The single wavelength set up was applied for cryptosporidium oocysts'size and relative refractive index measurement and differential measurement of the concentration of cryptosporidium oocysts suspended in water and mixed polystyrene latex sphere suspension. The measurement results showed good agreement with the control reference values. These results indicate that the proposed method could potentially be applied to online detection in a water quality control system.

  2. Improving Canopy Vertical Structure Measurements with Dual-Wavelength Laser Scanning

    NASA Astrophysics Data System (ADS)

    Li, Z.; Strahler, A. H.; Schaaf, C.; Jupp, D. L. B.; Howe, G.; Hewawasam, K.; Chakrabarti, S.; Cook, T.; Paynter, I.; Saenz, E. J.; Yang, X.; Yao, T.

    2015-12-01

    Forest canopy structure regulates radiation interception through the canopy, affects the canopy microclimate, and consequently influences the energy, water, and carbon fluxes between soil, vegetation and atmosphere through its interaction with leaf physiological functioning. To observe vertical canopy forest structure in finer and more accurate detail, we retrieved vertical profiles of leaf and woody components separately with a terrestrial laser scanner, the Dual-Wavelength Echidna Lidar (DWEL). DWEL scans of a hardwood site at the Harvard Forest, Petersham, Massachusetts, USA, in early May and in late September in 2014, revealed the spatial heterogeneity of the canopy vertical structure of the two vegetation components: leaves and woody materials. The DWEL collects simultaneous scans of forests with two lasers at different wavelengths, 1064 nm (NIR) and 1548 nm (SWIR). Power returned from leaves is much lower than from woody materials such as trunks and branches at the SWIR wavelength due to the liquid water absorption by leaves, whereas returned power at the NIR wavelength is similar from both leaves and woody materials. This spectral contrast between leaves and woody materials, along with spatial context information. discriminates leaves and woody materials accurately in 3-D space, thus allowing the measurement of separate leaf and woody area profiles. We also captured the change in the canopy vertical structure over the seven years by a comparison between the current measurements by the DWEL in 2014 and past measurements in 2007 at the same site by the DWEL's predecessor, a single-wavelength terrestrial lidar, the Echidna Validation Instrument. The comparison also demonstrates the advantage of dual-wavelength laser scanning by the DWEL for canopy structure measurements.

  3. A Study on Feasibility of Dual-Wavelength Radar for Identification of Hydrometeor Phases

    NASA Technical Reports Server (NTRS)

    Liao, Liang; Meneghini, Robert

    2010-01-01

    An important objective for the Dual-wavelength Ku-/Ka-band Precipitation Radar (DPR) that will be on board the Global Precipitation Measuring (GPM) core satellite, is to identify the phase state of hydrometeors along the range direction. To assess this, radar signatures are simulated in snow and rain to explore the relation between the differential frequency ratio (DFR), defined as the difference of radar reflectivity factors between Ku- and Ka-bands, and the radar reflectivity factor at Ku-band, ZKu, for different hydrometeor types. Model simulations indicate that there is clear separation between snow and rain in the ZKu-DFR plane assuming that the snow follows the Gunn-Marshall size distribution (1958) and rain follows the Marshall-Palmer size distribution (1948). In an effort to verify the simulated results, the data collected by the Airborne Second Generation Precipitation Radar (APR-2) in the Wakasa Bay AMSR-E campaign are employed. Using the signatures of Linear Depolarization Ratio (LDR) at Ku-band, the APR-2 data can be easily divided into the regions of snow, mixed phase and rain for stratiform storms. These results are then superimposed onto the theoretical curves computed from the model in the ZKu-DFR plane. It has been found that in 90% of the cases, snow and rain can be distinguished if the Ku-band radar reflectivity exceeds 18 dBZ (the minimum detectable level of GPM DPR at Ku-band). This is also the case for snow and mixed-phase hydrometeors. Although snow can be easily distinguished from rain and melting hydrometeors by using Ku- and Ka-band radar, the rain and mixed-phase particles are not always separable. It is concluded that Ku- and Ka-band dual-wavelength radar might provide a potential means to identify the phase state of hydrometeors.

  4. Pigmented guinea pig skin irradiated with Q-switched ruby laser pulses. Morphologic and histologic findings

    SciTech Connect

    Dover, J.S.; Margolis, R.J.; Polla, L.L.; Watanabe, S.; Hruza, G.J.; Parrish, J.A.; Anderson, R.R.

    1989-01-01

    Q-switched ruby laser pulses cause selective damage to cutaneous pigmented cells. Repair of this selective damage has not been well described. Therefore, using epilated pigmented and albino guinea pig skin, we studied the acute injury and tissue repair caused by 40-ns, Q-switched ruby laser pulses. Gross observation and light and electron microscopy were performed. No specific changes were evident in the albino guinea pigs. In pigmented animals, with radiant exposures of 0.4 J/cm2 or greater, white spots confined to the 2.5-mm exposure sites developed immediately and faded over 20 minutes. Delayed depigmentation occurred at seven to ten days, followed by full repigmentation by four to eight weeks. Regrowing hairs in sites irradiated at and above 0.4 J/cm2 remained white for at least four months. Histologically, vacuolation of pigment-laden cells was seen immediately in the epidermis and the follicular epithelium at exposures of 0.3 J/cm2 and greater. Melanosomal disruption was seen immediately by electron microscopy at and above 0.3 J/cm2. Over the next seven days, epidermal necrosis was followed by regeneration of a depigmented epidermis. By four months, melanosomes and melanin pigmentation had returned; however, hair follicles remained depigmented and devoid of melanocytes. This study demonstrates that selective melanosomal disruption caused by Q-switched ruby laser pulses leads to transient cutaneous depigmentation and persistent follicular depigmentation. Potential exists for selective treatment of pigmented epidermal and dermal lesions with this modality.

  5. Cardiovascular damage after cw and Q-switched 2μm laser irradiation

    NASA Astrophysics Data System (ADS)

    Rohde, Ingo; Masch, Jennifer-M.; Theisen-Kunde, Dirk; Marczynski-Bühlow, Martin; Lutter, Georg; Brinkmann, Ralf

    2013-06-01

    Aiming for laser-assisted resection of calcified aortic valve structures for Transcatheter Aortic Valve Implantation (TAVI), a Q-switched Tm:YAG laser emitting at a wavelength of 2.01 μm was used to evaluate the cutting efficiency on highly calcified human aortic leaflets in-vitro. The calcified aortic leaflets were examined regarding ablation rates and debris generation, using a pulse energy of 4.3 mJ, a pulse duration of 0.8-1 μs and a repetition rate of 1 kHz. The radiation was transmitted via a 200 μm core diameter quartz fiber. Resection was performed in a fiber-tissue contact mode on water-covered samples in a dish. The remnant particles were analyzed with respect to quantity and size by light microscopy. Additionally, soft tissue of porcine aortic vessels was examined for histologically detectable thermo-mechanical damage after continuous wave and Q-switched 2μm laser irradiation. An ablation rate of 36.7 +/- 25.3 mg/min could be realised on highly calcified aortic leaflets, with 85.4% of the remnant particles being <6 μm in diameter. The maximum damaged area of the soft tissue was < 1 mm for both, cw and pulsed laser irradiation. This limits the expected collateral damage of healthy tissue during the medical procedure. Overall, the Q-switched Tm:YAG laser system showed promising results in cutting calcified aortic valves, transmitting sufficient energy through a small flexible fibre.

  6. Single Longitudinal Mode, High Repetition Rate, Q-switched Ho:YLF Laser for Remote Sensing

    NASA Technical Reports Server (NTRS)

    Bai, Yingxin; Yu, Jirong; Petzar, Paul; Petros, M.; Chen, Songsheng; Trieu, Bo; Lee, Nyung; Singh, U.

    2009-01-01

    Ho:YLF/LuLiF lasers have specific applications for remote sensing such as wind-speed measurement and carbon dioxide (CO2) concentration measurement in the atmosphere because the operating wavelength (around 2 m) is located in the eye-safe range and can be tuned to the characteristic lines of CO2 absorption and there is strong backward scattering signal from aerosol (Mie scattering). Experimentally, a diode pumped Ho:Tm:YLF laser has been successfully used as the transmitter of coherent differential absorption lidar for the measurement of with a repetition rate of 5 Hz and pulse energy of 75 mJ [1]. For highly precise CO2 measurements with coherent detection technique, a laser with high repetition rate is required to averaging out the speckle effect [2]. In addition, laser efficiency is critically important for the air/space borne lidar applications, because of the limited power supply. A diode pumped Ho:Tm:YLF laser is difficult to efficiently operate in high repetition rate due to the large heat loading and up-conversion. However, a Tm:fiber laser pumped Ho:YLF laser with low heat loading can be operated at high repetition rates efficiently [3]. No matter whether wind-speed or carbon dioxide (CO2) concentration measurement is the goal, a Ho:YLF/LuLiF laser as the transmitter should operate in a single longitudinal mode. Injection seeding is a valid technique for a Q-switched laser to obtain single longitudinal mode operation. In this paper, we will report the new results for a single longitudinal mode, high repetition rate, Q-switched Ho:YLF laser. In order to avoid spectral hole burning and make injection seeding easier, a four mirror ring cavity is designed for single longitudinal mode, high repetition rate Q-switched Ho:YLF laser. The ramp-fire technique is chosen for injection seeding.

  7. Transform-limited pulses generated by an actively Q-switched distributed fiber laser.

    PubMed

    Cuadrado-Laborde, C; Pérez-Millán, P; Andrés, M V; Díez, A; Cruz, J L; Barmenkov, Yu O

    2008-11-15

    A single-mode, transform-limited, actively Q-switched distributed-feedback fiber laser is presented, based on a new in-line acoustic pulse generator. Our technique permits a continuous adjustment of the repetition rate that modulates the Q factor of the cavity. Optical pulses of 800 mW peak power, 32 ns temporal width, and up to 20 kHz repetition rates were obtained. The measured linewidth demonstrates that these pulses are transform limited: 6 MHz for a train of pulses of 10 kHz repetition rate, 80 ns temporal width, and 60 mW peak power. Efficient excitation of spontaneous Brillouin scattering is demonstrated.

  8. Q-switched Nd:glass-laser-induced acoustic pulses in lithotripsy

    NASA Astrophysics Data System (ADS)

    D'yakonov, G. I.; Mikhailov, B. A.; Pak, S. K.; Shcherbakov, Ivan A.; Andreev, Valeri G.; Rudenko, O. V.; Sapozhnikov, A. V.

    1991-07-01

    This paper describes preliminary experimental data of kidney stone fragmentation by the laser induced shock acoustic pulses. Acoustic pulses were produced in a thin layer of liquid as a result of absorption process of 1.06 micrometers radiation pulses. The phosphate Nd:glass laser operated in a pulse Q-switched regime with the pulse energy up to 10 J and pulse duration $OM 30 ns. The pressure induced by acoustic pulses on stones surface was reached up to 1-2 kbar in focal area, that was sufficient for stone destruction.

  9. Improvement in encrustation removal from artworks using multi pulse Q-switched laser

    NASA Astrophysics Data System (ADS)

    Marczak, Jan; Jach, Karol; Sarzyński, Antoni

    2005-09-01

    The paper presents application of laser radiation for cleaning of monuments and art works, using Q -switched Nd:YAG laser generating high power series of pulses in so called "burst mode". The time width of pulse train is 200 ÷ 300 μs. The oscilloscope traces of pulse repetition frequency and the results of energy measurements are shown. Numerical model of interaction of high power laser pulse with graphite layer of aluminium substrate on the base of equations in one-dimensional hydrodynamic approximation is presented. The results of calculations of graphite removal process for single pulse and train of laser pulses are in qualitative agreement with the results of measurements.

  10. High efficient actively Q-switched Ho:LuAG laser.

    PubMed

    Duan, Xiaoming; Yao, Baoquan; Li, Gang; Ju, Youlun; Wang, Yuezhu; Zhao, Guangjun

    2009-11-23

    We present the room temperature Q-switched performances of a Ho:LuAG laser operated at 2.1 microm. At the repetition rate of 10 kHz, the maximum average output power of 9.9 W with a slope efficiency of 69.9% relative to absorbed pump power was obtained in Ho:LuAG laser. Also, the minimum pulse width of 33.0 ns was obtained, corresponding to the peak power was 30.0 kW.

  11. Visible light stimulating dual-wavelength emission and O vacancy involved energy transfer behavior in luminescence for coaxial nanocable arrays

    SciTech Connect

    Yang, Lei; Dong, Jiazhang; Jiang, Zhongcheng; Pan, Anlian; Zhuang, Xiujuan

    2014-06-14

    We report a strategy to investigate O vacancy (V{sub O}) involved energy transfer and dual-wavelength yellow emission in coaxial nanocable. By electric field deposition and subsequent sol-gel template approach, ZnO:Tb/Y{sub 2}O{sub 3}:Eu coaxial nanocable arrays are synthesized. After visible light excitation, system is promoted to O vacancy charge transfer state of V{sub O}(0/+). In the following cross relaxation, energy transfer from V{sub O} to the excitation energy level of Tb{sup 3+} in ZnO:Tb core area. While in Y{sub 2}O{sub 3}:Eu shell area, energy transfer to the excitation energy level of Eu{sup 3+}. Subsequently, dual-wavelength emission is observed. By constructing nanocable with dual-wavelength emission, yellow luminescence is obtained. Adjust doping concentration of Eu{sup 3+} or Tb{sup 3+} in the range of 0.01–0.05, chromaticity coordinates of ZnO:Tb/Y{sub 2}O{sub 3}:Eu nanocable stably stays at yellow region in color space except ZnO:Tb{sub 0.01}/Y{sub 2}O{sub 3}:Eu{sub 0.01}. As Vo states act as media in energy transfer process in nanocablers, visible light can stimulate dual-wavelength emissions. Yellow luminescent nanocable arrays will have great applications in light-emitting diode luminescence.

  12. Visible light stimulating dual-wavelength emission and O vacancy involved energy transfer behavior in luminescence for coaxial nanocable arrays

    NASA Astrophysics Data System (ADS)

    Yang, Lei; Dong, Jiazhang; Jiang, Zhongcheng; Pan, Anlian; Zhuang, Xiujuan

    2014-06-01

    We report a strategy to investigate O vacancy (VO) involved energy transfer and dual-wavelength yellow emission in coaxial nanocable. By electric field deposition and subsequent sol-gel template approach, ZnO:Tb/Y2O3:Eu coaxial nanocable arrays are synthesized. After visible light excitation, system is promoted to O vacancy charge transfer state of VO(0/+). In the following cross relaxation, energy transfer from VO to the excitation energy level of Tb3+ in ZnO:Tb core area. While in Y2O3:Eu shell area, energy transfer to the excitation energy level of Eu3+. Subsequently, dual-wavelength emission is observed. By constructing nanocable with dual-wavelength emission, yellow luminescence is obtained. Adjust doping concentration of Eu3+ or Tb3+ in the range of 0.01-0.05, chromaticity coordinates of ZnO:Tb/Y2O3:Eu nanocable stably stays at yellow region in color space except ZnO:Tb0.01/Y2O3:Eu0.01. As Vo states act as media in energy transfer process in nanocablers, visible light can stimulate dual-wavelength emissions. Yellow luminescent nanocable arrays will have great applications in light-emitting diode luminescence.

  13. Optimization of a Fabry-Perot Q-switch fiber optic laser

    NASA Astrophysics Data System (ADS)

    Armas Rivera, Ivan; Beltrán Pérez, Georgina; Kuzin, Evgene; Castillo Mixcóatl, Juan; Muñoz Aguirre, Severino

    2013-11-01

    Optical fiber Q-Switch lasers have been used in a variety of application areas in science as well as in industry owing to their multiple characteristics. A possible application is that owing to their high output power they can be used as pumping sources for supercontinuum generation. Such source can be employed in optical coherence tomography (OCT) focused to dermatology. Therefore it is important to develop sources with emission wavelength that are not injurious to human skin. In the present work erbium doped fiber (EDF) was used owing that its emission wavelength (1550 nm) is adequate for this purpose. The most efficient way of achieving high power in a Q-Switch laser is optimizing all the parameters involved in the pulses generation, such as pumping power, active medium length and modulation frequency. The results show that using a fiber length of 7 meters is possible to get 10 μJ of energy, a peak power of 140 W, an average power of 27.5mW with temporal widths of 500 ns. The laser uses an acousto-optic device to modulate the internal loses inside the cavity. As highly reflecting mirrors, a Sagnac Interferometer and a Fiber Bragg Grating was employed.

  14. LD-pumped acousto-optical Q-switched burst-mode Nd:YAG laser

    NASA Astrophysics Data System (ADS)

    Pan, Hu; Yan, Renpeng; Li, Xudong; Ma, Yufei; Yu, Xin; Chen, Deying

    2016-04-01

    A high-repetition-rate, high-peak-power burst-mode laser for laser-based measurement applications is presented by using a master oscillator power amplifier structure. An laser diode arrays (LDA) side-pumped Nd:YAG acousto-optical (A-O) Q-switched laser serves as the master oscillator. Under pulsed pumping, pulse trains with 2-25 pulses are obtained when the repetition rate changes from 10 kHz to 100 kHz. The maximum pulse burst energy of 31.2 mJ is achieved in the A-O Q-switched pulse burst laser oscillator at 10 kHz. Two LDA side pumped Nd:YAG modules are employed in the amplification stage. After the amplification, the pulse burst energy at 10 kHz reaches ~170 mJ with a single pulse energy of 85.2 mJ and a pulse width of 14.5 ns, generating a peak power of 6.1 MW. At 100 kHz, the total burst energy reaches 220 mJ with a single pulse energy of 8.8 mJ in the pulse burst laser system.

  15. Melanosomes are a primary target of Q-switched ruby laser irradiation in guinea pig skin

    SciTech Connect

    Polla, L.L.; Margolis, R.J.; Dover, J.S.; Whitaker, D.; Murphy, G.F.; Jacques, S.L.; Anderson, R.R.

    1987-09-01

    The specific targeting of melanosomes may allow for laser therapy of pigmented cutaneous lesions. The mechanism of selective destruction of pigmented cells by various lasers, however, has not been fully clarified. Black, brown, and albino guinea pigs were exposed to optical pulses at various radiant exposure doses from a Q-switched, 40 nsec, 694 nm ruby laser. Biopsies were analyzed by light and electron microscopy (EM). Albino animals failed to develop clinical or microscopic evidence of cutaneous injury after irradiation. In both black and brown animals, the clinical threshold for gross change was 0.4 J/cm2, which produced an ash-white spot. By light microscopy, alterations appeared at 0.3 J/cm2 and included separation at the dermoepidermal junction, and the formation of vacuolated epidermal cells with a peripheral cytoplasmic condensation of pigment. By EM, enlarged melanosomes with a central lucent zone were observed within affected epidermal cells at 0.3 J/cm2. At 0.8 and 1.2 J/cm2, individual melanosomes were more intensely damaged and disruption of melanosomes deep in the hair papillae was observed. Dermal-epidermal blisters were formed precisely at the lamina lucida, leaving basal cell membranes and hemidesmosomes intact. Possible mechanisms for melanosomal injury are discussed. These observations show that the effects of the Q-switched ruby laser are melanin-specific and melanin-dependent, and may be useful in the selective destruction of pigmented as well as superficial cutaneous lesions.

  16. Coherent polarization locking of Q-switched Ho:YAG laser

    NASA Astrophysics Data System (ADS)

    Chua, C. F.; Tan, L. H.; Phua, P. B.

    2013-03-01

    We had demonstrated the use of Coherent Polarization Locking (CPL) to mitigate the intra-cavity optical damage in a Q-switched Ho:YAG laser. By splitting the available pump power into two individual Ho:YAG laser rods, we had passively coherent combined two orthogonal polarized lasers with output pulse energy of 9.13mJ, pulse width of 14ns, operating at 800Hz pulse repetition rate. In contrast, when all the pump power was pumped on a single Ho:YAG laser rod built with the same cavity configuration, severe optical damage was observed. It was occurred at the surface coating of the laser rod when operating at < 2kHz pulse repetition rate, thus limiting the output pulse energy to < 5mJ. We also demonstrated, first to our knowledge, that by performing Q-switching only in one of the laser arms, it resulted in pulse operation for the entire CPL laser cavity.

  17. High brightness sub-nanosecond Q-switched laser using volume Bragg gratings

    NASA Astrophysics Data System (ADS)

    Anderson, Brian M.; Hale, Evan; Venus, George; Ott, Daniel; Divliansky, Ivan; Glebov, Leonid

    2016-03-01

    The design of Q-switched lasers capable of producing pulse widths of 100's of picoseconds necessitates the cavity length be shorter than a few centimeters. Increasing the amount of energy extracted per pulse requires increasing the mode area of the resonator that for the same cavity length causes exciting higher order transverse modes and decreasing the brightness of the output radiation. To suppress the higher order modes of these multimode resonators while maintaining the compact cavity requires the use of intra-cavity angular filters. A novel Q-switched laser design is presented using transmitting Bragg gratings (TBGs) as angular filters to suppress the higher order transverse modes. The laser consists of a 5 mm thick slab of Nd:YAG, a 3 mm thick slab of Cr:YAG with a 20% transmission, one TBG aligned to suppress the higher order modes along the x-axis, and a 40% output coupler. The gratings are recorded in photo-thermo-refractive (PTR) glass, which has a high damage threshold that can withstand both the high peak powers and high average powers present within the resonator. Using a 4.1 mrad TBG in a 10.8 mm long resonator with an 800μm x 400 μm pump beam, a nearly diffraction limited beam quality of M2 = 1.3 is obtained in a 0.76 mJ pulse with a pulse width of 614 ps.

  18. Treatment of infraorbital dark circles using 694-nm fractional Q-switched ruby laser.

    PubMed

    Xu, Tian-Hua; Li, Yuan-Hong; Chen, John Z S; Gao, Xing-Hua; Chen, Hong-Duo

    2016-12-01

    The objective of this study was to evaluate the efficacy and safety of using a 694-nm fractional Q-switched ruby laser to treat infraorbital dark circles. Thirty women with infraorbital dark circles (predominant color: dark/brown) participated in this open-labeled study. The participants received eight sessions of 694-nm fractional Q-switched ruby laser treatment using a fluence of 3.0-3.5 J/cm(2), at an interval of 7 days. The melanin deposition in the lesional skin was observed in vivo using reflectance confocal microscopy (RCM). The morphological changes were evaluated using a global evaluation, an overall self-assessment, and a Mexameter. Twenty-eight of the 30 patients showed global improvements that they rated as excellent or good. Twenty-six patients rated their overall satisfaction as excellent or good. The melanin index indicated a substantial decrease from 240.44 (baseline) to 194.56 (P < 0.05). The RCM results showed a dramatic decrease in melanin deposition in the upper dermis. The adverse effects were minimal. The characteristic finding of dark/brown infraorbital dark circles is caused by increased melanin deposition in the upper dermis. The treatment of these infraorbital dark circles using a 694-nm fractional QSR laser is safe and effective.

  19. S-band Q-switched fiber laser using MoSe2 saturable absorber

    NASA Astrophysics Data System (ADS)

    Ahmad, H.; Ismail, M. A.; Sathiyan, S.; Reduan, S. A.; Ruslan, N. E.; Lee, C. S. J.; Zulkifli, M. Z.; Thambiratnam, K.; Ismail, M. F.; Harun, S. W.

    2017-01-01

    A passively Q-switched S-band fiber laser using Molybdenum Diselenide (MoSe2) saturable absorber (SA) is proposed and demonstrated. The SA is fabricated by depositing MoSe2 onto two fiber ferrules using the drop-cast method before heating and connecting the two fiber ferrules to form the SA. The passively Q-switched fiber laser designed using the MoSe2 SA has an operational range of 1491.0-1502.0 nm. The output pulse train has a pulse-width ranging from 2.0 μs to 1.0 μs and corresponding repetition rate of between 34.5 kHz and 90 kHz with increasing pump powers, as well as a signal-to-noise of about 35.97 dB. The peak performance of the proposed laser is between 1480.0 and 1490.0 nm, corresponding to the first peak gain region with the S-band.

  20. Energy enhancement of mixed Nd:LuYSGG crystal in passively Q-switched lasers.

    PubMed

    Wang, Baolin; Tian, Li; Yu, Haohai; Zhang, Huaijin; Wang, Jiyang

    2015-07-01

    The continuous-wave (cw) and passively Q-switched laser performances of mixed Nd:Lu(2)YSc(1.5)Ga(3.5)O(12) (Nd:LuYSGG) crystal at 1.06 μm were reported for the first time. The cw output power reached 4.39 W at the absorbed pump power of 10.34 W with slope efficiency of 48.0%. With a Cr(4+):YAG crystal as both the saturable absorber and output coupler, a passively Q-switched laser was realized with the maximum average output power of 1.43 W and slope efficiency of 21.0%. The shortest pulse width, largest pulse energy, and highest peak power were 4.1 ns, 157.1 μJ, and 38.3 kW, respectively. Compared with Nd:Lu(3)Sc(1.5)Ga(3.5)O(12) (Nd:LuSGG) crystal, the pulse energy and peak power are enhanced over more than two times for Nd:LuYSGG. The results show that Nd:LuYSGG crystal is a promising laser material with large energy storage capacities and suitable for the application of pulsed lasers with shorter pulses and larger energies.

  1. Nanosecond passively Q-switched Nd:YVO4 laser based on WS2 saturable absorber

    NASA Astrophysics Data System (ADS)

    Wang, Xi; Li, Lu; Wang, Yonggang; Zhang, Ling; Wen, Qiao; Yang, Guowen

    2017-04-01

    We report on a nanosecond pulse generation in a diode end-pumped passively Q-switched Nd:YVO4 laser using a tungsten disulfide (WS2) solution saturable absorber (SA). The WS2 suspension is fabricated by the liquid-phase-exfoliated method and injected into a quartz cell for the use of SA. Compared with solid absorber, such solution absorber has the virtues of good optical transparency, high heat dissipation and long term stability. By inserting the WS2 solution SA in the laser cavity, a stable Q-switched laser operation centered at 1064.45 nm wavelength is obtained with the shortest pulse duration of 788 ns and corresponding repetition rate of 333.5 kHz. The maximum average output power is registered to be 720 mW with the slope efficiency of 7.8%. To the best of our knowledge, it is the highest output power so far among pulsed lasers based on transition metal dichalcogenides (TMDs) SAs. The results demonstrate that WS2 solution absorber is a promising saturable absorber for the generation of high output power pulsed lasers.

  2. Q-switched Erbium-doped fiber laser at 1600 nm for photoacoustic imaging application

    NASA Astrophysics Data System (ADS)

    Piao, Zhonglie; Zeng, Lvming; Chen, Zhongping; Kim, Chang-Seok

    2016-04-01

    We present a nanosecond Q-switched Erbium-doped fiber (EDF) laser system operating at 1600 nm with a tunable repetition rate from 100 kHz to 1 MHz. A compact fiber coupled, acousto-optic modulator-based EDF ring cavity was used to generate a nanosecond seed laser at 1600 nm, and a double-cladding EDF based power amplifier was applied to achieve the maximum average power of 250 mW. In addition, 12 ns laser pulses with the maximum pulse energy of 2.4 μJ were obtained at 100 kHz. Furthermore, the Stokes shift by Raman scattering over a 25 km long fiber was measured, indicating that the laser can be potentially used to generate the high repetition rate pulses at the 1.7 μm region. Finally, we detected the photoacoustic signal from a human hair at 200 kHz repetition rate with a pulse energy of 1.2 μJ, which demonstrates that a Q-switched Er-doped fiber laser can be a promising light source for the high speed functional photoacoustic imaging.

  3. Tailoring the performance of q-switched solid state lasers: why and how

    NASA Astrophysics Data System (ADS)

    Geiger, Stephan

    2006-02-01

    Diode-pumped, solid state, q-switched lasers now enable a very diverse array of precision materials-processing applications. An important key to ongoing market growth and applications diversification is the development of lasers whose performance is optimally tailored to meet the needs of specific applications. For example, long output pulses are preferable for soft wafer marking, whereas short pulses are desirable for solar cell scribing and creating gray-scale pictures for passports and other personal identity applications. The pulsewidth and overall output power are interdependent performance characteristics determined by laser design parameters such as resonator length, repetition rate, and pumping intensity. This interdependence leads to trade-offs when optimizing the laser performance, meaning that no single resonator configuration can simultaneously meet the needs of all applications. This paper reviews the basics of q-switched, diode-pumped laser operation, and examines some of their most important applications in terms of performance requirements. We then present a modular laser design approach that enables niche markets and prototype applications to be serviced with optimum performance, without incurring significant costs for custom laser development.

  4. Compact MEMS mirror based Q-switch module for pulse-on-demand laser range finders

    NASA Astrophysics Data System (ADS)

    Milanović, Veljko; Kasturi, Abhishek; Atwood, Bryan; Su, Yu; Limkrailassiri, Kevin; Nettleton, John E.; Goldberg, Lew; Cole, Brian J.; Hough, Nathaniel

    2015-02-01

    A highly compact and low power consuming Q-switch module was developed based on a fast single-axis MEMS mirror, for use in eye-safe battery-powered laser range finders The module's 1.6mm x 1.6mm mirror has <99% reflectance at 1535nm wavelength and can achieve mechanical angle slew rates of over 500 rad/sec when switching the Er/Yb:Glass lasing cavity from pumping to lasing state. The design targeted higher efficiency, smaller size, and lower cost than the traditional Electro-Optical Q-Switch. Because pulse-on-demand capability is required, resonant mirrors cannot be used to achieve the needed performance. Instead, a fast point-to-point analog single-axis tilt actuator was designed with a custom-coated high reflectance (HR) mirror to withstand the high intra-cavity laser fluence levels. The mirror is bonded on top of the MEMS actuator in final assembly. A compact MEMS controller was further implemented with the capability of autonomous on-demand operation based on user-provided digital trigger. The controller is designed to receive an external 3V power supply and a digital trigger and it consumes ~90mW during the short switching cycle and ~10mW in standby mode. Module prototypes were tested in a laser cavity and demonstrated high quality laser pulses with duration of ~20ns and energy of over 3mJ.

  5. Multi-species trace gas analysis with dual-wavelength quantum cascade laser

    NASA Astrophysics Data System (ADS)

    Jágerská, Jana; Tuzson, Béla; Looser, Herbert; Jouy, Pierre; Hugi, Andreas; Mangold, Markus; Soltic, Patrik; Faist, Jérôme; Emmenegger, Lukas

    2015-04-01

    Simultaneous detection of multiple gas species using mid-IR laser spectroscopy is highly appealing for a large variety of applications ranging from air quality monitoring, medical breath analysis to industrial process control. However, state-of-the-art distributed-feedback (DFB) mid-IR lasers are usually tunable only within a narrow spectral range, which generally leads to one-laser-one-compound measurement strategy. Thus, multi-species detection involves several lasers and elaborate beam combining solutions [1]. This makes them bulky, costly, and highly sensitive to optical alignment, which limits their field deployment. In this paper, we explore an alternative measurement concept based on a dual-wavelength quantum cascade laser (DW-QCL) [2]. Such a laser can emit at two spectrally distinct wavelengths using a succession of two DFB gratings with different periodicities and a common waveguide to produce one output beam. The laser design was optimized for NOx measurements and correspondingly emits single-mode at 5.26 and 6.25 μm. Electrical separation of the respective laser sections makes it possible to address each wavelength independently. Thereby, it is possible to detect NO and NO2 species with one laser using the same optical path, without any beam combining optics, i.e. in a compact and cost-efficient single-path optical setup. Operated in a time-division multiplexed mode, the spectrometer reaches detection limits at 100 s averaging of 0.5 and 1.5 ppb for NO2 and NO, respectively. The performance of the system was validated against the well-established chemiluminescence detection while measuring the NOx emissions on an automotive test-bench, as well as monitoring the pollution at a suburban site. [1] B. Tuzson, K. Zeyer, M. Steinbacher, J. B. McManus, D. D. Nelson, M. S. Zahniser, and L. Emmenegger, 'Selective measurements of NO, NO2 and NOy in the free troposphere using quantum cascade laser spectroscopy,' Atmospheric Measurement Techniques 6, 927-936 (2013

  6. Dual wavelength lidar observation of tropical high-altitude cirrus clouds during the ALBATROSS 1996 Campaign

    NASA Astrophysics Data System (ADS)

    Beyerle, G.; Schäfer, H.-J.; Neuber, R.; Schrems, O.; McDermid, I. S.

    Dual wavelength aerosol lidar observations of tropical high-altitude cirrus clouds were performed during the ALBATROSS 1996 campaign aboard the research vessel “POLARSTERN” on the Atlantic ocean in October-November 1996. On the basis of 57 hours of night-time observations between 23.5°N and 23.5°S we find in 72% of the altitude profiles indications of the presence of cirrus cloud layers. This percentage drops to 32% at subtropical latitudes (23.5°-30°) based on 15 hours of data. About one-half of the subtropical and tropical cirrus layers are subvisual with an optical depth of less than 0.03 at a wavelength of 532 nm. In general the clouds exhibit high spatial and temporal variability on scales of a few tens of meters vertically and a few hundred meters horizontally. No clouds are observed above the tropopause. An abrupt change in the relation between the color ratios of the parallel and perpendicular backscatter coefficients at about 240 K is interpreted in terms of changes of particle shape and/or size distribution. At temperatures between 195 and 255 K only a small fraction of the observations are consistent with the presence of small particles with dimensions of less than 0.1 µm.

  7. Capabilities and performance of dual-wavelength Echidna® lidar

    NASA Astrophysics Data System (ADS)

    Howe, Glenn A.; Hewawasam, Kuravi; Douglas, Ewan S.; Martel, Jason; Li, Zhan; Strahler, Alan; Schaaf, Crystal; Cook, Timothy A.; Chakrabarti, Supriya

    2015-01-01

    We describe the capabilities and performance of a terrestrial laser scanning instrument built for the purpose of recording and retrieving the three-dimensional structure of forest vegetation. The dual-wavelength Echidna® lidar characterizes the forest structure at an angular resolution as fine as 1 mrad while distinguishing between leaves and trunks by exploiting their differential reflectances at two wavelengths: 1 and 1.5 μm. The instrument records the full waveforms of return signals from 5 ns laser pulses at half-nanosecond time resolution; obtains ±117 deg zenith and 360 deg azimuth coverage out to a radius of more than 70 m provides single-target range resolution of 4.8 and 2.3 cm for the 1 and 1.5 μm channels, respectively (1σ) and separates adjacent pulse returns in the same waveform at a distance of 52.0 and 63.8 cm apart for the 1 and 1.5 μm channels, respectively. The angular resolution is in part controlled by user-selectable divergence optics and is shown to be <2 mrad for the instrument's standard resolution mode, while the signal-to-noise ratio is 10 at 70 m range for targets with leaf-like reflectance for both channels. The portability and target differentiation make the instrument an ideal ground-based lidar suited for vegetation sensing.

  8. Dual wavelength fluorescent ratiometric pH measurement by scanning near-field optical microscopy

    NASA Astrophysics Data System (ADS)

    Li, Yongbo; Shinohara, Ryosuke; Iwami, Kentaro; Ohta, Yoshihiro; Umeda, Norihiro

    2010-08-01

    A novel method to observe pH distribution by dual wavelength fluorescent ratiometric pH measurement by scanning near-field optical microscopy (SNOM) is developed. In this method, in order to investigate not only the pH of mitochondrial membrane but also its distribution in the vicinity, a pH sensitive fluorescent reagent covers mitochondria instead of injecting it to mitochondria. This method utilizes a dual-emission pH sensitive dye and SNOM with a themally-pulled and metal-coated optical fiber to improve the spatial resolution. Time-dependence of Fluorescent intensity ratio (FIR) under acid addition is investigated. As the distances between the dropped point and the SNOM probe becomes closer, the time when FIR changes becomes earlier. The response of mitochondria under supplement of nutrition is studied by using this method. While the probe is near to mitochondria, the ratio quickly becomes to increase. In conclusion, it was confirmed that the temporal variation of pH can be detected by this method, and pH distribution in the vicinity of mitochondria is able to be measured by this method.

  9. Dual-wavelength Digital Holography for quantification of cell volume and integral refractive index (RI)

    NASA Astrophysics Data System (ADS)

    Boss, Daniel; Kuehn, Jonas; Depeursinge, Christian; Magistretti, Pierre J.; Marquet, Pierre

    2011-07-01

    Quantitative Phase Imaging techniques such as DHM have emerged recently in life sciences and can be aimed at monitoring and quantifying non-invasively dynamic cellular processes modifying cell morphology and/or content. Concretely, the DHM phase signal depends on two cell parameters: cell thickness and integral refractive index. Consequently, due to its dual origin, the interpretation of the phase signal variations remain difficult. Since a net water flux across the cell membrane causes a variation of both parameters, the phase signal cannot be related directly to cellular RI or thickness variations, but must be understood as a coupled signal of these two parameters. We have developped a Dual-wavelength Digital Holographic Microscopy (DHM) setup to separately measure in a single shot fashion cellular thickness and integral RI of living cells. The method is based on the use of an absorbing dye that causes a high RI dispersion in the extracellular medium at the two recording wavelength. Consequently, the phase signals measured at the two wavelengths, differ significantly from each other. Practically, both cell RI and thickness can be univocally determined from the two phase measurements. Important biophysical parameters of living cells, including dry mass concentrations and water membrane permeability can be deduced.

  10. Retrieve Optically Thick Ice Cloud Microphysical Properties by Using Airborne Dual-Wavelength Radar Measurements

    NASA Technical Reports Server (NTRS)

    Wang, Zhien; Heymsfield, Gerald M.; Li, Lihua; Heymsfield, Andrew J.

    2005-01-01

    An algorithm to retrieve optically thick ice cloud microphysical property profiles is developed by using the GSFC 9.6 GHz ER-2 Doppler Radar (EDOP) and the 94 GHz Cloud Radar System (CRS) measurements aboard the high-altitude ER-2 aircraft. In situ size distribution and total water content data from the CRYSTAL-FACE field campaign are used for the algorithm development. To reduce uncertainty in calculated radar reflectivity factors (Ze) at these wavelengths, coincident radar measurements and size distribution data are used to guide the selection of mass-length relationships and to deal with the density and non-spherical effects of ice crystals on the Ze calculations. The algorithm is able to retrieve microphysical property profiles of optically thick ice clouds, such as, deep convective and anvil clouds, which are very challenging for single frequency radar and lidar. Examples of retrieved microphysical properties for a deep convective clouds are presented, which show that EDOP and CRS measurements provide rich information to study cloud structure and evolution. Good agreement between IWPs derived from an independent submillimeter-wave radiometer, CoSSIR, and dual-wavelength radar measurements indicates accuracy of the IWC retrieved from the two-frequency radar algorithm.

  11. Low-cost scheme for high-precision dual-wavelength laser metrology.

    PubMed

    Kok, Yitping; Ireland, Michael J; Robertson, J Gordon; Tuthill, Peter G; Warrington, Benjamin A; Tango, William J

    2013-04-20

    A method capable of delivering relative optical path length metrology with nanometer precision is demonstrated. Unlike conventional dual-wavelength metrology, which employs heterodyne detection, the method developed in this work utilizes direct detection of interference fringes of two He-Ne lasers as well as a less precise stepper motor open-loop position control system to perform its measurement. Although the method may be applicable to a variety of circumstances, the specific application in which this metrology is essential is in an astrometric optical long baseline stellar interferometer dedicated to precise measurement of stellar positions. In our example application of this metrology to a narrow-angle astrometric interferometer, measurement of nanometer precision could be achieved without frequency-stabilized lasers, although the use of such lasers would extend the range of optical path length the metrology can accurately measure. Implementation of the method requires very little additional optics or electronics, thus minimizing the cost and effort of implementation. Furthermore, the optical path traversed by the metrology lasers is identical to that of the starlight or science beams, even down to using the same photodetectors, thereby minimizing the noncommon path between metrology and science channels.

  12. Noncontact simultaneous dual wavelength photoplethysmography: A further step toward noncontact pulse oximetry

    NASA Astrophysics Data System (ADS)

    Humphreys, Kenneth; Ward, Tomas; Markham, Charles

    2007-04-01

    We present a camera-based device capable of capturing two photoplethysmographic (PPG) signals at two different wavelengths simultaneously, in a remote noncontact manner. The system comprises a complementary metal-oxide semiconductor camera and dual wavelength array of light emitting diodes (760 and 880nm). By alternately illuminating a region of tissue with each wavelength of light, and detecting the backscattered photons with the camera at a rate of 16frames/wavelengths, two multiplexed PPG wave forms are simultaneously captured. This process is the basis of pulse oximetry, and we describe how, with the inclusion of a calibration procedure, this system could be used as a noncontact pulse oximeter to measure arterial oxygen saturation (SpO2) remotely. Results from an experiment on ten subjects, exhibiting normal SpO2 readings, that demonstrate the instrument's ability to capture signals from a range of subjects under realistic lighting and environmental conditions are presented. We compare the signals captured by the noncontact system to a conventional PPG signal captured concurrently from a finger, and show by means of a J. Bland and D. Altman [Lancet 327, 307 (1986); Statistician 32, 307 (1983)] test, the noncontact device to be comparable to a contact device as a monitor of heart rate. We highlight some considerations that should be made when using camera-based "integrative" sampling methods and demonstrate through simulation, the suitability of the captured PPG signals for application of existing pulse oximetry calibration procedures.

  13. Noncontact simultaneous dual wavelength photoplethysmography: A further step toward noncontact pulse oximetry

    SciTech Connect

    Humphreys, Kenneth; Ward, Tomas; Markham, Charles

    2007-04-15

    We present a camera-based device capable of capturing two photoplethysmographic (PPG) signals at two different wavelengths simultaneously, in a remote noncontact manner. The system comprises a complementary metal-oxide semiconductor camera and dual wavelength array of light emitting diodes (760 and 880 nm). By alternately illuminating a region of tissue with each wavelength of light, and detecting the backscattered photons with the camera at a rate of 16 frames/wavelength s, two multiplexed PPG wave forms are simultaneously captured. This process is the basis of pulse oximetry, and we describe how, with the inclusion of a calibration procedure, this system could be used as a noncontact pulse oximeter to measure arterial oxygen saturation (S{sub p}O{sub 2}) remotely. Results from an experiment on ten subjects, exhibiting normal S{sub p}O{sub 2} readings, that demonstrate the instrument's ability to capture signals from a range of subjects under realistic lighting and environmental conditions are presented. We compare the signals captured by the noncontact system to a conventional PPG signal captured concurrently from a finger, and show by means of a J. Bland and D. Altman [Lancet 327, 307 (1986); Statistician 32, 307 (1983)] test, the noncontact device to be comparable to a contact device as a monitor of heart rate. We highlight some considerations that should be made when using camera-based ''integrative'' sampling methods and demonstrate through simulation, the suitability of the captured PPG signals for application of existing pulse oximetry calibration procedures.

  14. Dual-wavelength photoacoustic technique for monitoring tissue status during thermal treatments

    NASA Astrophysics Data System (ADS)

    Hsiao, Yi-Sing; Wang, Xueding; Deng, Cheri X.

    2013-06-01

    Photoacoustic (PA) techniques have been exploited for monitoring thermal treatments. However, PA signals depend not only on tissue temperature but also on tissue optical properties which indicate tissue status (e.g., native or coagulated). The changes in temperature and tissue status often occur simultaneously during thermal treatments, so both effects cause changes to PA signals. A new dual-wavelength PA technique to monitor tissue status independent of temperature is performed. By dividing the PA signal intensities obtained at two wavelengths at the same temperature, a ratio, which only depends on tissue optical properties, is obtained. Experiments were performed with two experimental groups, one with untreated tissue samples and the other with high-intensity focused ultrasound treated tissue samples including thermal coagulated lesion, using ex vivo porcine myocardium specimens to test the technique. The ratio of PA signal intensities obtained at 700 and 800 nm was constant for both groups from 25 to 43°C, but with distinct values for the two groups. Tissue alteration during thermal treatment was then studied using water bath heating of tissue samples from 35 to 60°C. We found that the ratio stayed constant before it exhibited a marked increase at around 55°C, indicating tissue changes at this temperature.

  15. Mach-Zehnder modulator modulated radio-over-fiber transmission system using dual wavelength linearization

    NASA Astrophysics Data System (ADS)

    Zhu, Ran; Hui, Ming; Shen, Dongya; Zhang, Xiupu

    2017-02-01

    In this paper, dual wavelength linearization (DWL) technique is studied to suppress odd and even order nonlinearities simultaneously in a Mach-Zehnder modulator (MZM) modulated radio-over-fiber (RoF) transmission system. A theoretical model is given to analyze the DWL employed for MZM. In a single-tone test, the suppressions of the second order harmonic distortion (HD2) and third order harmonic distortion (HD3) at the same time are experimentally verified at different bias voltages of the MZM. The measured spurious-free dynamic ranges (SFDRs) with respect to the HD2 and HD3 are improved simultaneously compared to using a single laser. The output P1 dB is also improved by the DWL technique. Moreover, a WiFi signal is transmitted in the RoF system to test the linearization for broadband signal. The result shows that more than 1 dB improvement of the error vector magnitude (EVM) is obtained by the DWL technique.

  16. Experimental validation of a theoretical model of dual wavelength photoacoustic (PA) excitation in fluorophores

    NASA Astrophysics Data System (ADS)

    Märk, Julia; Theiss, Christoph; Schmitt, Franz-Josef; Laufer, Jan

    2015-03-01

    Fluorophores, such as exogenous dyes and genetically expressed proteins, exhibit radiative relaxation with long excited state lifetimes. This can be exploited for PA detection based on dual wavelength excitation using pump and probe wavelengths that coincide with the absorption and emission spectra, respectively. While the pump pulse raises the fluorophore to a long-lived excited state, simultaneous illumination with the probe pulse reduces the excited state lifetime due to stimulated emission (SE).This leads to a change in thermalized energy, and hence PA signal amplitude, compared to single wavelength illumination. By introducing a time delay between pump and probe pulses, the change in PA amplitude can be modulated. Since the effect is not observed in endogenous chromophores, it provides a contrast mechanism for the detection of fluorophores via PA difference imaging. In this study, a theoretical model of the PA signal generation in fluorophores was developed and experimentally validated. The model is based on a system of coupled rate equations, which describe the spatial and temporal changes in the population of the molecular energy levels of a fluorophore as a function of pump-probe energy and concentration. This allows the prediction of the thermalized energy distribution, and hence the time-resolved PA signal amplitude. The model was validated by comparing its predictions to PA signals measured in solutions of rhodamine 6G, a well-known laser dye, and Atto680, a NIR fluorophore.

  17. Dual-wavelength mode-locking of novel chirped multilayer quantum-dot lasers

    NASA Astrophysics Data System (ADS)

    Chiang, Chun-Ping; Lin, Gray; Chen, Yu-Chen; Cheng, Hsu-Chieh

    2016-09-01

    Monolithic passively mode-locked lasers are investigated based on chirped multilayer InAs/InGaAs QDs. Three chirped wavelengths, with stacking numbers of 2, 3 and 5 layers, are designed with capped InGaAs thickness of 4, 3 and 1 nm, respectively. The ridge-waveguide devices of 5-μm width and 3-mm length are fabricated to have absorber-to-gain length ratio of 1:9. A curve tracer is used to analyze the hysteresis on the light-current curve. Two kinks in the L-I curve are observed at threshold current near 50 mA and at higher current of about 150 mA. The lasing wavelength just above threshold is centered at 1268 nm and the RF spectrum of mode-locking is peaked at 13.32 GHz. At well above threshold of 200 mA, another RF peak at 13.21 GHz occurs that corresponds to shorter lasing wavelength around 1233 nm. The two lasing wavelengths are originated from ground-state transitions of two groups of InAs/InGaAs QDs. Simultaneous dual-wavelength mode-locking is therefore achieved at rather low forward current and low reverse bias by incorporating this novel design of QD structure.

  18. Structure of picosecond pulses of a Q-switched and mode-locked diode-pumped Nd:YAG laser

    SciTech Connect

    Donin, V I; Yakovin, D V; Gribanov, A V

    2015-12-31

    The pulse duration of a diode-pumped Nd:YAG laser, in which Q-switching with mode-locking (QML regime) is achieved using a spherical mirror and a travelling-wave acousto-optic modulator, is directly measured with a streak camera. It is found that the picosecond pulses can have a non-single-pulse structure, which is explained by excitation of several competing transverse modes in the Q-switching regime with a pulse repetition rate of 1 kHz. In the case of cw mode-locking (without Q-switching), a new (auto-QML) regime is observed, in which the pulse train repetition rate is determined by the frequency of the relaxation oscillations of the laser field while the train contains single picosecond pulses. (control of laser radiation parameters)

  19. Study on characteristics of diode-pumped continuous-wave tunable and passively Q-switched Tm:SSO laser

    NASA Astrophysics Data System (ADS)

    Feng, T. L.; Zhao, S. Z.; Yang, K. J.; Li, G. Q.; Li, D. C.; Zhao, J.; Qiao, W. C.; Zheng, L. H.; Xu, J.; Wang, Q. G.; Xu, X. D.; Su, L. B.

    2014-10-01

    In this paper, we present a diode-pumped continuous-wave tunable and Q-switched Tm:SSO laser with a semiconductor saturable absorber mirror. In continuous-wave regime, a maximum output power of 340 mW at 1,980.7 nm was obtained. With a quartz plate, wavelength-tunable continuous-wave operation was achieved from 1,922 to 2,020 nm. In Q-switched regime, a maximum output pulse energy of 14.7 μJ under a repetition rate of 800 Hz and a minimum pulse width of 7.6 μs corresponding to a repetition rate of 8.8 kHz around 1,974.4 nm were obtained from the passively Q-switched Tm:SSO laser.

  20. All-optical Q-switching limiter for high-power gigahertz modelocked diode-pumped solid-state lasers.

    PubMed

    Klenner, Alexander; Keller, Ursula

    2015-04-06

    Passively modelocked diode-pumped solid-state lasers (DPSSLs) with pulse repetition rates in the gigahertz regime suffer from an increased tendency for Q-switching instabilities. Low saturation fluence intracavity saturable absorbers - such as the semiconductor saturable absorber mirrors (SESAMs) - can solve this problem up to a certain average output power limited by the onset of SESAM damage. Here we present a passive stabilization mechanism, an all-optical Q-switching limiter, to reduce the impact of Q-switching instabilities and increase the potential output power of SESAM modelocked lasers in the gigahertz regime. With a proper cavity design a Kerr lens induced negative saturable absorber clamps the maximum fluence on the SESAM and therefore limits the onset of Q-switching instabilities. No critical cavity alignment is required because this Q-switching limiter acts well within the cavity stability regime. Using a proper cavity design, a high-power diode-pumped Yb:CALGO solid-state laser generated sub-100 fs pulses with an average output power of 4.1 W at a pulse repetition rate of 5 GHz. With a pulse duration of 96 fs we can achieve a peak power as high as 7.5 kW directly from the SESAM modelocked laser oscillator without any further external pulse amplification and/or pulse compression. We present a quantitative analysis of this Kerr lens induced Q-switching limiter and its impact on modelocked operation. Our work provides a route to compact high-power multi-gigahertz frequency combs based on SESAM modelocked diode-pumped solid-state lasers without any additional external amplification or pulse compression.

  1. Q-switching of a high-power solid-state laser by a fast scanning Fabry-Perot interferometer

    SciTech Connect

    Baburin, N V; Borozdov, Yu V; Danileiko, Yu K; Denker, B I; Ivanov, A D; Osiko, Vyacheslav V; Sverchkov, S E; Sidorin, A V; Chikov, V A; Ifflander, R; Hack, R; Kertesz, I; Kroo, N

    1998-07-31

    An investigation was made of the suitability of a Q-switch, based on a piezoelectrically scanned short-base Fabry-Perot interferometer, for an Nd{sup 3+}:YAG laser with an average output radiation power up to 2 kW. The proposed switch made it possible to generate of giant pulses of 60 - 300 ns duration at a repetition rate of 20 - 100 kHz. Throughout the investigated range of the pulse repetition rates the average power was at least equal to that obtained by cw lasing. Special requirements to be satisfied by the interferometer, essential for efficient Q-switching, were considered. (control of laser radiation parameters)

  2. Theoretical and experimental investigation of actively Q-switched Nd:YAG 946 nm laser with considering ETU effects

    NASA Astrophysics Data System (ADS)

    Yan, R.; Yu, X.; Li, X.; Chen, D.; Yu, J.

    2012-09-01

    A theoretical model on actively Q-switched Nd3+-doped quasi-three-level laser including the energy transfer upconversion and the ground state reabsorption is developed. The analytical expressions of the fractional thermal loading and the average output power are obtained, and the influence of ETU effects on laser performance for different repetition rate is analyzed. The average output power and the thermal focal length of the Q-switched 946 nm laser are acquired in experiment. The good agreement between the experimental data and theoretical results demonstrates the reliability of the theoretical model.

  3. Ytterbium-doped Q-switched fiber laser based upon manganese dioxide (MnO2) saturable absorber.

    PubMed

    Hattori, Haroldo T; Khaleque, Abdul; Liu, Liming; Greck, Michael R

    2016-11-10

    Manganese dioxide (MnO2) is an abundant material that is widely used in many devices, such as alkaline batteries. At infrared frequencies, MnO2 is lossy and strongly absorbs light. These characteristics make MnO2 a potential candidate as a low-cost saturable absorber in Q-switched lasers. In this paper, we examine the performance of MnO2 as a saturable absorber in an ytterbium-doped Q-switched fiber laser: we show that it can produce pulses with durations ranging from 300 to 1800 ns.

  4. Enhancement of passive Q-switching performance with mixed Nd:LuxGd1-xVO4 laser crystals.

    PubMed

    Yu, Haohai; Zhang, Huaijin; Wang, Zhengping; Wang, Jiyang; Yu, Yonggui; Shao, Zongshu; Jiang, Minhua

    2007-08-01

    Passive Q-switching operation has been demonstrated with a class of mixed Nd:Lu(x)Gd(1-x)VO(4) laser crystals. With respect to that obtained with Nd:GdVO(4), the passive Q-switching performance, including threshold, pulse energy, and peak power, was found to be greatly enhanced with the mixed vanadate crystals. The shortest pulse width of 6.2 ns, largest pulse energy of 192.5 microJ, and highest peak power of 31.1 kW were obtained at the incident pump power of 13.75 W with the mixed crystal for x=0.5.

  5. Diode-pumped Q-switched Nd:YLF laser at 1313 nm

    NASA Astrophysics Data System (ADS)

    Xu, Shan; Gao, Shufang; Zheng, Chunyan

    2016-06-01

    In this letter, we describe the operation of an end-pumped acousto-optic Q-switched Nd:YLF laser. According to the theoretical analysis and calculation for Nd:YLF crystal, the thermal focal length of σ-polarized laser is positive in plane-parallel resonator, while that of π-polarized laser is negative. Hence laser operation at σ-polarized 1313 nm should be stable in plane-parallel cavity. When absorbed pump power is 12.45 W and the pulse repetition frequency is 10 kHz, 3.1 W output laser at 1313 nm is achieved. As a result, the optical-optical conversion efficiency is 25.4 % and slope efficiency is 31.2 %, respectively.

  6. A high repetition rate passively Q-switched microchip laser for controllable transverse laser modes

    NASA Astrophysics Data System (ADS)

    Dong, Jun; Bai, Sheng-Chuang; Liu, Sheng-Hui; Ueda, Ken-Ichi; Kaminskii, Alexander A.

    2016-05-01

    A Cr4+:YAG passively Q-switched Nd:YVO4 microchip laser for versatile controllable transverse laser modes has been demonstrated by adjusting the position of the Nd:YVO4 crystal along the tilted pump beam direction. The pump beam diameter-dependent asymmetric saturated inversion population inside the Nd:YVO4 crystal governs the oscillation of various Laguerre-Gaussian, Ince-Gaussian and Hermite-Gaussian modes. Controllable transverse laser modes with repetition rates over 25 kHz and up to 183 kHz, depending on the position of the Nd:YVO4 crystal, have been achieved. The controllable transverse laser beams with a nanosecond pulse width and peak power over hundreds of watts have been obtained for potential applications in optical trapping and quantum computation.

  7. Permanent makeup removal using Q-switched Nd:YAG laser.

    PubMed

    Lee, C N; Bae, E Y; Park, J G; Lim, S H

    2009-12-01

    Red-brown tattoos are usually treated with a frequency-doubled Q-switched (QS) neodymium:yttrium-aluminum-garnet Nd:YAG laser (532 nm), because red and pink pigments show maximum absorption between 500 and 570 nm. Using a QS laser for red-brown tattoo removal has sometimes led to paradoxical darkening of the tattoo pigments, and this darkened grey-black colour may be difficult to remove. A woman with red-brown cosmetic tattoos on her eyebrows was treated using a QS Nd:YAG laser (1064 nm) initially with low fluence and subsequently with increasing fluences at 6-weekly intervals. After the first treatment, a slight darkening of the tattoo pigments was seen, but this faded and complete clearance was achieved after five treatments. There was no downtime during every treatment and there were no scars, pigmentary alterations or textural changes.

  8. Natural Gas Engine Performance Ignited by a Passively Q-Switched Microlaser

    SciTech Connect

    Bihari, Bipin; Biruduganti, Munidhar; Gupta, Sreenath

    2015-04-01

    A robust end pumped, passively Q-switched, air-cooled, microlaser was designed and prototyped to yield a 1064 nm pulsed laser output of 21 mJ/P with a pulse width of 4.2 ns FWHM. This microlaser was coupled to a standard laser plug carrying a sapphire lens with 13 mm back focal length. This assembly was tested in a natural gas fueled single-cylinder engine, and in one cylinder of a turbocharged 6-cylinder engine. Single cylinder engine tests showed extension of the lean ignition limit which enabled an efficiency improvement of 0.2% while meeting emission regulations. The tests conducted in the 6-cylinder engine showed highly improved ignition stability.

  9. Intracavity optical parametric oscillator pumped by an actively Q-switched Nd:YAG laser

    NASA Astrophysics Data System (ADS)

    Liu, Z. J.; Wang, Q. P.; Zhang, X. Y.; Liu, Z. J.; Wang, H.; Chang, J.; Fan, S. Z.; Ma, F. S.; Jin, G. F.

    2008-03-01

    A non-critically phase-matched KTiOPO4 optical parametric oscillator (OPO) intracavity pumped by a laser diode end-pumped acousto-optically Q-switchedNd:YAG laser is experimentally demonstrated. The highest average power is obtained at the pulse repetition rate (PRR) of around 15 kHz, which is different from the widely reported Nd:YVO4 laser pumped OPO in which the highest average power is obtained at a very high PRR, e.g. 80 kHz. With an incident laser diode power of 6.93 W and a pulse repetition rate of 15 kHz, an average signal power of 0.72 W is obtained with a peak power of 7.7 kW and an optical-to-optical conversion efficiency of 10.4%.

  10. Q-switched 1064nm laser source for photomechanical ablation in obsidianus lapis

    NASA Astrophysics Data System (ADS)

    Aguilar-Morales, A. I.; Álvarez-Chávez, J. A.; Morales-Ramírez, A. J.; Panzner, Michael; Ortega-Delgado, M. A.

    2015-09-01

    The process of ablation in obsidianus lapis is mainly governed by pulse energy from the laser source and scanning speed. The rate of material ablation is influenced by chemical and physical properties. In this work, laser energy at 1064 nm, has been used for ablation behavior in Q-switch regime. A >40 W, average power Nd:YAG source with pulse energies ranging from 3mJ to nearly 7 mJ, achieved surface damages up to 160 μm of depth. Photo-mechanical ablation in terms of scan speed showed a maximum depth of nearly 500 μm at 130 mm/s. The maximum pulse energy of 12 mJ resulted in ablation of 170 μm depth. Highly efficient ablation in obsidianus lapis for artistic work is an interesting field of application.

  11. Intraoperative localized urticarial reaction during Q-switched Nd:YAG laser tattoo removal.

    PubMed

    Wilken, Reason; Ho, Derek; Petukhova, Tatyana; Jagdeo, Jared

    2015-03-01

    Q-switched lasers, such as the neodymium:yttrium-aluminum-garnet (Nd:YAG) laser, are the gold standard for tattoo removal. Allergy to tattoo pigment is well-documented, but adverse allergic reactions during or shortly after laser tattoo removal are rare with few reports in the medical literature. Here we describe an intraoperative, localized urticarial reaction that developed during treatment of a tattoo using a 1064-nm Nd:YAG laser. As laser tattoo removal becomes increasingly popular amongst our patients, it is important for dermatologists to be aware of urticarial allergic reactions as well as their management. We outline our recommendations for medical management of this condition and hope that these guidelines will facilitate patient care by dermatologists who encounter this immune skin reaction to laser tattoo removal

  12. Q-switched laser removal of tattoos: a clinical and spectroscopic investigation of the mechanism

    NASA Astrophysics Data System (ADS)

    Siomos, Konstadinos; Bailey, Raymond T.; Cruickshank, Frank R.; Murphy, Michael

    1996-01-01

    The liquid phase spectra of tatoo pigments are shown to be unreliable as a basis for mechanistic deductions. The reflectance spectra of the solids from 2000 nm to 500 nm (5000 to 20,000 cm-1) are shown to accurately assess the relative loss of laser light for different pigments and to be useful in examining these to check for similarities in the pigments. The absorbance differences between the pigments are shown to be largely irrelevant in assessing the ease of tatoo removal by laser radiation of a variety of wavelengths. A multiphoton absorption mechanism with its concomitant shock wave is proposed to be responsible for the reduction of pigment particles to small sizes which the lymph system can remove. The different behavior of blue and green tattoos, treated by Q-switched ruby and Nd:YAG lasers, is attributed to the particle aggregation size of the pigments in the tattoo.

  13. Experimental investigation on CFRP milling by low power Q-switched Yb:YAG laser source

    NASA Astrophysics Data System (ADS)

    Genna, S.; Tagliaferri, F.; Papa, I.; Leone, C.; Palumbo, B.

    2016-05-01

    In the present study, laser milling of CFRP plate by means of a 30W Q-Switched Yb:YAG fiber laser is investigated through statistical analysis. Milling tests were performed at the nominal power changing the pulse power; the scanning speed, the hatch distance and the released energy. Design of Experiments (DoE) and ANalysis Of VAriance (ANOVA) were applied with the aim to improve the process performances in term of material removal rate and heat affected zone extension. The results show that, the adopted laser is an effective solution for the CFRP milling. Moreover, adopting an accurate approach to the problem, process variability and material damages can be easily reduced.

  14. Compact, passively Q-switched Nd:YAG laser for the MESSENGER mission to Mercury.

    PubMed

    Krebs, Danny J; Novo-Gradac, Anne-Marie; Li, Steven X; Lindauer, Steven J; Afzal, Robert S; Yu, Anthony W

    2005-03-20

    A compact, passively Q-switched Nd:YAG laser has been developed for the Mercury Laser Altimeter, an instrument on the Mercury Surface, Space Environment, Geochemistry, and Ranging mission to the planet Mercury. The laser achieves 5.4% efficiency with a near-diffraction-limited beam. It passed all space-flight environmental tests at subsystem, instrument, and satellite integration testing and successfully completes a postlaunch aliveness check en route to Mercury. The laser design draws on a heritage of previous laser altimetry missions, specifically the Ice Cloud and Elevation Satellite and the Mars Global Surveyor, but incorporates thermal management features unique to the requirements of an orbit of the planet Mercury.

  15. Hybrid Nd 3+-doped passively Q-switched waveguide laser made by ion exchange

    NASA Astrophysics Data System (ADS)

    Salas-Montiel, Rafael; Bastard, Lionel; Broquin, Jean-Emmanuel

    2008-02-01

    In the mid 80's, the doping of optical fiber's core with rare earth atoms has been a major breakthrough in the field of optical telecommunications since it allowed the realization of in-line optical amplifiers. However, erbium-doped fiber amplifiers are a few meters long and a huge effort has been made in order to realize compact and efficient active devices based on rare-earth-doped waveguides. For this purpose the use of phosphate glasses instead of silicate ones has been investigated because they allow a better solubility of the inserted rare earths. In this paper we present the realization of a hybrid Neodymium-doped passively Q-switched waveguide laser made by ion exchange on a Schott IOG-1 phosphate laser glass combined with the deposition of a BDN saturable absorber diluted in a cellulose acetate polymer cladding. In a first step, we present the CW operation of the laser with an undoped cladding. We show that for a 3.5-μm wide, 1.4-cm long waveguide realized by a silver-sodium ion exchange, a 6 mW output has been achieved by creating a Fabry-Perot cavity with dielectric multilayers mirrors sticked to the chip facets. Then, the characterizations performed on the BDN doped layers are presented. It is shown that a proper selection of the hybrid guiding structure and saturable absorber concentration entail an excess absorption ranging from 1 to 10 dB/cm at zero flux. Finally, results on Q-switched behavior are presented. Optical pulse duration of 2-ns (FWHM) was obtained with repetition rates ranging from 5 to around 50 kHz for a 22 W pulse peak power.

  16. High performance fiber optic sensor based on self referenced FBGs and high-speed dual-wavelength pulse coding

    NASA Astrophysics Data System (ADS)

    Zaidi, Farhan; Nannipieri, Tiziano; Di Pasquale, Fabrizio

    2015-07-01

    We propose and experimentally demonstrate the feasibility of a highly efficient FBG-based quasi-distributed sensing system employing dual-wavelength cyclic pulse coding. Significant improvement in the measurement range, resolution and TDM multiplexing capabilities can be achieved, as well as crosstalk reduction with respect to a single wavelength TDM-based FBG interrogation scheme. The mechanism of noise reduction by quasi-periodic cyclic coding is experimentally demonstrated, pointing out significant improvement in accuracy with respect to dual-wavelength single pulse TDM-based FBG interrogation. The proposed technique can also enhance the sensing range of hybrid fiber optic sensor systems in which continuous monitoring of distributed and discrete points are simultaneously measured over the same sensing fiber.

  17. Dual-wavelength waveguide lasers at 1064 and 1079 nm in Nd:YAP crystal by direct femtosecond laser writing.

    PubMed

    Nie, Weijie; Cheng, Chen; Jia, Yuechen; Romero, Carolina; Vázquez de Aldana, Javier R; Chen, Feng

    2015-05-15

    Low-loss depressed cladding waveguides have been produced in Nd:YAP laser crystal by using direct femtosecond laser writing. Under optical pump at 812 nm at room temperature, continuous-wave simultaneous dual-wavelength laser oscillations at 1064 and 1079 nm, both along TM polarization, have been realized in the waveguiding structures. It has been found that, with the variation of pump polarization, the intensity ratio of 1064 and 1079 nm emissions varies periodically, while the polarization of output dual-wavelength laser remains unchanged. The maximum output power achieved for the Nd:YAP waveguide lasers is ∼200  mW with a slope efficiency of 33.4%.

  18. Theoretical and experimental analysis of tunable Sagnac high-birefringence loop filter for dual-wavelength laser application.

    PubMed

    Álvarez-Tamayo, R I; Durán-Sánchez, M; Pottiez, O; Kuzin, E A; Ibarra-Escamilla, B; Flores-Rosas, A

    2011-01-20

    We present detailed investigations of the spectral dependencies of the transmission of a fiber optical loop mirror (FOLM) consisting of a coupler with output ports spliced at arbitrary angles to a high-birefringence (Hi-Bi) fiber. The application for dual-wavelength lasers is discussed. For this aim, the spectral dependence of the reflection is tuned by the temperature of the Hi-Bi fiber that allows a fine adjustment of the cavity loss for generated wavelengths. The ratio between maximum and minimum reflection can be adjusted by the twist angle of the fiber at the splices, which also provides useful possibilities for the adjustment of cavity losses. We used the twist and temperature variation of the Hi-Bi fiber to change the operation from single wavelength to stable dual-wavelength generation with either equal or unequal powers of wavelengths.

  19. Broadly tunable dual-wavelength erbium-doped ring fiber laser based on a high-birefringence fiber loop mirror

    NASA Astrophysics Data System (ADS)

    Sun, H. B.; Liu, X. M.; Gong, Y. K.; Li, X. H.; Wang, L. R.

    2010-02-01

    A broadly tunable dual-wavelength erbium-doped ring fiber laser based on a high-birefringence fiber loop mirror (HiBi-FLM) and a polarization controller is demonstrated experimentally. The measured transmission spectrum of HiBi-FLM covers a wide range from 1525 to 1575 nm. The wavelength of proposed laser can be flexibly tunable during this range of ˜50 nm by adjusting the polarization controller. In addition, the spacing of two wavelengths is adjustable by changing the length of HiBi fiber. The dual-wavelength lasers with the HiBi fiber length of 1 and 2 m are experimentally demonstrated and compared. The experimental results show that the proposed laser can stably operate on two wavelengths simultaneously at room temperature, and the output peak power variation is about 0.5 dB during 40 min.

  20. Dual-wavelength laser operation in a-cut Nd:MgO:LiNbO3

    NASA Astrophysics Data System (ADS)

    Fan, M. Q.; Li, T.; Zhao, S. Z.; Li, G. Q.; Li, D. C.; Yang, K. J.; Qiao, W. C.; Li, S. X.

    2016-03-01

    Diode-pumped dual-wavelength a-cut Nd:MgO:LiNbO3 lasers near 1085 and 1093 nm were experimentally and theoretically investigated. The simultaneous dual-wavelength emitting was mainly attributed to the Boltzmann distribution of the occupation in the Stark-split energy-levels in manifold 4I11/2. Under an absorbed pump power of 7.45 W, a maximum continuous wave (CW) output power of 1.23 W was obtained, giving a slope efficiency of 21.2%. Using Cr:YAG as saturable absorber, the shortest pulse duration of 28 ns was obtained with a repetition rate of 24 kHz, resulting in a peak power of 729 W.

  1. A 100 mW-level single-mode switchable dual-wavelength erbium-doped fiber laser

    NASA Astrophysics Data System (ADS)

    Cheng, Jianqun; Zhang, Liaolin; Sharafudeen, Kaniyarakkal; Qiu, Jianrong

    2013-10-01

    A switchable dual-wavelength CW erbium-doped fiber laser with two cascaded fiber Bragg gratings has been proposed and demonstrated experimentally at room temperature. The laser uses a linear resonant cavity configuration incorporating a Sagnac loop with a polarization controller (PC) and can switch flexibly to output a single wavelength or dual wavelengths based on the polarization hole burning (PHB) effect. The slope efficiency and maximum output power can reach 23% and 96 mW, respectively. The two lasing peaks of the laser, with a narrow linewidth output and an optical signal-to-noise ratio of more than 50 dB, are located in the C and L bands of the optical communication window, respectively. The laser shows good stability with respect to the wavelength and output power.

  2. The Dual Wavelength Ratio knee: a signature of multiple scattering in airborne Ku-Ka observations

    NASA Astrophysics Data System (ADS)

    Battaglia, Alessandro; Tanelli, Simone; Heymsfield, Gerald; Tian, Lin

    2014-05-01

    Deep convective systems observed by the HIWRAP radar during the 2011 MC3E field campaign in Oklahoma provide the first evidence of multiple scattering effects simultaneously at Ku and Ka band. One feature is novel and noteworthy: often, in correspondence to shafts with strong convection and when moving from the top of the cloud downward, the dual wavelength ratio (DWR) first increases as usual in Ku-/Ka-band observations, but then it reaches a maximum and after that point it steadily decreases all the way to the surface, forming what will be hereinafter referred to as a knee. This DWR knee cannot be reproduced by single-scattering theory under almost any plausible cloud microphysical profile, on the other hand it is explained straightforwardly with the help of multiple scattering theory when simulations involving hail-bearing convective cores with large horizontal extents are performed. The DWR reduction in the lower troposphere (i.e., DWR increasing with altitude) is interpreted as the result of multiple scattering pulse stretching caused by the highly-diffusive hail layer positioned high up in the atmosphere, with Ka multiple scattering typically exceeding that occurring in the Ku channel. Since the effects of multiple scattering increase with increasing footprint size, if multiple scattering effects are present in the aircraft measurements, they are likely to be more pronounced in the space-borne dual-frequency Ku - Ka radar observations, envisaged for the NASA-JAXA Global Precipitation (GPM) Measurement Mission, whose launch is expected in February 2014. Our notional study supports the idea that DWR knees will be observed by the GPM radar when overflying high-density ice shafts embedded in large convective systems and suggests that their explanation must not be sought in differential attenuation or differential Mie but via multiple scattering effects.

  3. Minimally Invasive Treatment of Infrabony Periodontal Defects Using Dual-Wavelength Laser Therapy

    PubMed Central

    Hughes, Francis J.; Wadia, Reena

    2016-01-01

    Introduction. Surgical management of infrabony defects is an invasive procedure, frequently requiring the use of adjunctive material such as grafts or biologics, which is time-consuming and associated with expense and morbidity to the patient. Lasers in periodontal regeneration have been reported in the literature, with each wavelength having potential benefits through different laser-tissue interactions. The purpose of this case series was to assess the efficacy of a new dual-wavelength protocol in the management of infrabony defects. Materials and Methods. 32 defects (one in each patient) were treated using ultrasonic debridement, followed by flapless application of Erbium, Chromium:Yttrium, Scandium, Gallium, Garnet (Er,Cr:YSGG) laser (wavelength 2780 nm), and final application of diode laser (wavelength 940 nm). Pocket depths (PD) were measured after 6 months and repeat radiographs taken after one year. Results. The mean baseline PD was 8.8 mm (range 6–15 mm) and 6 months later was 2.4 mm (range 2–4 mm), with mean PD reduction being 6.4 ± 1.7 mm (range 3–12 mm). There was a significant gain in relative linear bone height (apical extent of bone), with mean percentage bone fill of 39.7 ± 41.2% and 53% of sites showing at least 40% infill of bone. Conclusion. The results compare favourably with traditional surgery and require further validation through randomised clinical controlled trials. PMID:27366790

  4. Dual-wavelength photothermal optical coherence tomography for blood oxygen saturation measurement

    NASA Astrophysics Data System (ADS)

    Yin, Biwei; Kuranov, Roman V.; McElroy, Austin B.; Milner, Thomas E.

    2013-03-01

    We report design and demonstration of a dual wavelength photothermal (DWP) optical coherence tomography (OCT) system for imaging of a phantom microvessel and measurement of hemoglobin oxygen saturation (SO2) level. The DWP-OCT system contains a swept-source (SS) two-beam phase-sensitive (PhS) OCT system (1060 nm) and two intensity modulated photothermal excitation lasers (770 nm and 800 nm). The PhS-OCT probe beam (1060 nm) and photothermal excitation beams are combined into one single-mode optical fiber. A galvanometer based two-dimensional achromatic scanning system is designed to provide 14 μm lateral resolution for the PhS-OCT probe beam (1060 nm) and 13 μm lateral resolution for photothermal excitation beams. DWP-OCT system's sensitivity is 102 dB, axial resolution is 13 μm in tissue and uses a real-time digital dispersion compensation algorithm. Noise floor for optical pathlength measurements is 300 pm in the signal frequency range (380-400 Hz) of photothermal modulation frequencies. Blood SO2 level is calculated from measured optical pathlength (op) signal in a 300 μm diameter microvessel phantom introduced by the two photothermal excitation beams. En-face and B-scan images of a phantom microvessel are recorded, and six blood samples' SO2 levels are measured using DWP-OCT and compared with values provided by a commercial blood oximeter. A mathematical model indicates thermal diffusion introduces a systematic artifact that over-estimates SO2 values and is consistent with measured data.

  5. Structure Measurements of Leaf and Woody Components of Forests with Dual-Wavelength Lidar Scanning Data

    NASA Astrophysics Data System (ADS)

    Strahler, A. H.; Li, Z.; Schaaf, C.; Howe, G.; Martel, J.; Hewawasam, K.; Douglas, E. S.; Chakrabarti, S.; Cook, T.; Paynter, I.; Saenz, E. J.; Wang, Z.; Woodcock, C. E.; Jupp, D. L. B.; Schaefer, M.; Newnham, G.

    2014-12-01

    Forest structure plays a critical role in the exchange of energy, carbon and water between land and atmosphere and nutrient cycle. We can provide detailed forest structure measurements of leaf and woody components with the Dual Wavelength Echidna® Lidar (DWEL), which acquires full-waveform scans at both near-infrared (NIR, 1064 nm) and shortwave infrared (SWIR, 1548 nm) wavelengths from simultaneous laser pulses. We collected DWEL scans at a broadleaf forest stand and a conifer forest stand at Harvard Forest in June 2014. Power returned from leaves is much lower than from woody materials such as trunks and branches at the SWIR wavelength due to the liquid water absorption by leaves, whereas returned power at the NIR wavelength is similar from both leaves and woody materials. We threshold a normalized difference index (NDI), defined as the difference between returned power at the two wavelengths divided by their sum, to classify each return pulse as a leaf or trunk/branch hit. We obtain leaf area index (LAI), woody area index (WAI) and vertical profiles of leaf and woody components directly from classified lidar hits without empirical wood-to-total ratios as are commonly used in optical methods of LAI estimation. Tree heights, diameter at breast height (DBH), and stem count density are the other forest structure parameters estimated from our DWEL scans. The separation of leaf and woody components in tandem with fine-scale forest structure measurements will benefit studies on carbon allocation of forest ecosystems and improve our understanding of the effects of forest structure on ecosystem functions. This research is supported by NSF grant, MRI-0923389

  6. Dual wavelength imaging of a scrape-off layer in an advanced beam-driven field-reversed configuration

    NASA Astrophysics Data System (ADS)

    Osin, D.; Schindler, T.

    2016-11-01

    A dual wavelength imaging system has been developed and installed on C-2U to capture 2D images of a He jet in the Scrape-Off Layer (SOL) of an advanced beam-driven Field-Reversed Configuration (FRC) plasma. The system was designed to optically split two identical images and pass them through 1 nm FWHM filters. Dual wavelength images are focused adjacent on a large format CCD chip and recorded simultaneously with a time resolution down to 10 μs using a gated micro-channel plate. The relatively compact optical system images a 10 cm plasma region with a spatial resolution of 0.2 cm and can be used in a harsh environment with high electro-magnetic noise and high magnetic field. The dual wavelength imaging system provides 2D images of either electron density or temperature by observing spectral line pairs emitted by He jet atoms in the SOL. A large field of view, combined with good space and time resolution of the imaging system, allows visualization of macro-flows in the SOL. First 2D images of the electron density and temperature observed in the SOL of the C-2U FRC are presented.

  7. Self Powered Highly Enhanced Dual Wavelength ZnO@CdS Core-Shell Nanorod Arrays Photodetector: An Intelligent Pair.

    PubMed

    Sarkar, Sanjit; Basak, Durga

    2015-08-05

    On the face of the impending energy crisis, developing low-energy or even zero-energy photoelectronic devices is extremely important. A multispectral photosensitivity feature of a self-powered device provides an additional powerful tool. We have developed an unprecedented high performance dual wavelength self-powered ZnO@CdS/PEDOT:PSS core-shell nanorods array photodetector through a simple aqueous chemical method wherein a suitable band alignment between an intelligent material pair, i.e. ZnO and CdS, has been utilized. Besides a noteworthy advantage of the devices being that they show a very sharp and prominent dual wavelength photosensitivity, both the ultraviolet and visible light sensitivity (ratio of current under illumination (Iphoto)/current under dark (Idark)) of the device are two orders of higher magnitude than those of pristine ZnO, attaining values of 2.8 × 10(3) and 1.07 × 10(3), respectively. At the same time, temporal responses faster than 20 ms could be achieved with these solution-processed photodetectors. The present study provides a very important direction to engineer core-shell nanostructured devices for dual wavelength high photosensitivity.

  8. Dual-wavelength excitation for fluorescence-based quantification of zinc protoporphyrin IX and protoporphyrin IX in whole blood.

    PubMed

    Hennig, Georg; Gruber, Christian; Vogeser, Michael; Stepp, Herbert; Dittmar, Stephan; Sroka, Ronald; Brittenham, Gary M

    2014-07-01

    Quantification of erythrocyte zinc protoporphyrin IX (ZnPP) and protoporphyrin IX (PPIX), individually or jointly, is useful for the diagnostic evaluation of iron deficiency, iron-restricted erythropoiesis, lead exposure, and porphyrias. A method for simultaneous quantification of ZnPP and PPIX in unwashed blood samples is described, using dual-wavelength excitation to effectively eliminate background fluorescence from other blood constituents. In blood samples from 35 subjects, the results of the dual-wavelength excitation method and a reference high performance liquid chromatography (HPLC) assay were closely correlated both for ZnPP (rs = 0.943, p < 0.0001; range 37-689 μmol ZnPP/mol heme, 84-1238 nmol/L) and for PPIX (rs = 0.959, p < 0.0001; range 42-4212 μmol PPIX/mol heme, 93-5394 nmol/L). In addition, for ZnPP, the proposed method is compared with conventional single-wavelength excitation and with commercial front-face fluorimetry of washed erythrocytes and whole blood. We hypothesize that dual-wavelength excitation fluorimetry will provide a new approach to the suppression of background fluorescence in blood and tissue measurements of ZnPP and PPIX.

  9. In Vivo Glucose Monitoring Using Dual-Wavelength Polarimetry to Overcome Corneal Birefringence in the Presence of Motion

    PubMed Central

    Malik, Bilal H.; Gresham, Vincent C.; Coté, Gerard L.

    2012-01-01

    Abstract Objective Over the past 35 years considerable research has been performed toward the investigation of noninvasive and minimally invasive glucose monitoring techniques. Optical polarimetry is one noninvasive technique that has shown promise as a means to ascertain blood glucose levels through measuring the glucose concentrations in the anterior chamber of the eye. However, one of the key limitations to the use of optical polarimetry as a means to noninvasively measure glucose levels is the presence of sample noise caused by motion-induced time-varying corneal birefringence. Research Design and Methods In this article our group presents, for the first time, results that show dual-wavelength polarimetry can be used to accurately detect glucose concentrations in the presence of motion-induced birefringence in vivo using New Zealand White rabbits. Results In total, nine animal studies (three New Zealand White rabbits across three separate days) were conducted. Using the dual-wavelength optical polarimetric approach, in vivo, an overall mean average relative difference of 4.49% (11.66 mg/dL) was achieved with 100% Zone A+B hits on a Clarke error grid, including 100% falling in Zone A. Conclusions The results indicate that dual-wavelength polarimetry can effectively be used to significantly reduce the noise due to time-varying corneal birefringence in vivo, allowing the accurate measurement of glucose concentration in the aqueous humor of the eye and correlating that with blood glucose. PMID:22691020

  10. Stable dual-wavelength single-longitudinal-mode ring erbium-doped fiber laser for optical generation of microwave frequency

    NASA Astrophysics Data System (ADS)

    Wang, T.; Liang, G.; Miao, X.; Zhou, X.; Li, Q.

    2012-05-01

    We demonstrate a simple dual-wavelength ring erbium-doped fiber laser operating in single-longitudinal-mode (SLM) at room temperature. A pair of reflection type short-period fiber Bragg gratings (FBGs), which have two different center wavelengths of 1545.072 and 1545.284 nm, are used as the wavelength-selective component of the laser. A segment of unpumped polarization maintaining erbium-doped fiber (PM-EDF) is acted as a narrow multiband filter. By turning the polarization controller (PC) to enhance the polarization hole burning (PHB), the single-wavelength and dual-wavelength laser oscillations are observed at 1545.072 and 1545.284 nm. The output power variation is less than 0.6 dB for both wavelengths over a five-minute period and the optical signal to noise ratio (OSNR) is greater than 50 dB. By beating the dual-wavelengths at a photodetector (PD), a microwave signal at 26.44 GHz is demonstrated.

  11. The Selection of Q-Switch for a 350mJ Air-borne 2-micron Wind Lidar

    NASA Technical Reports Server (NTRS)

    Petros, Mulugeta; Yu, Jirong; Trieu, Bo; Bai, Yingxin; Petzar, Paul; Singh, Upendra N.

    2008-01-01

    In the process of designing a coherent, high energy 2micron, Doppler wind Lidar, various types of Q-Switch materials and configurations have been investigated for the oscillator. Designing an oscillator with a relatively low gain laser material, presents challenges related to the management high internal circulating fluence due to high reflective output coupler. This problem is compounded by the loss of hold-off. In addition, the selection has to take into account the round trip optical loss in the resonator and the loss of hold-off. For this application, a Brewster cut 5mm aperture, fused silica AO Q-switch is selected. Once the Q-switch is selected various rf frequencies were evaluated. Since the Lidar has to perform in single longitudinal and transverse mode with transform limited line width, in this paper, various seeding configurations are presented in the context of Q-Switch diffraction efficiency. The master oscillator power amplifier has demonstrated over 350mJ output when the amplifier is operated in double pass mode and higher than 250mJ when operated in single pass configuration. The repetition rate of the system is 10Hz and the pulse length 200ns.

  12. Coupled-cavity electro-optically {ital Q}-switched Nd:YVO{sub 4} microchip lasers

    SciTech Connect

    Zayhowski, J.J.; Dill, C. III

    1995-04-01

    Nd:YVO{sub 4} microchip lasers have been electro-optically {ital Q} switched to produce 12-{mu}J pulses of 115-ps duration at repetition rates of up to 1 kHz. At a repetition rate of 2.25 MHz, 0.16-{mu}J pulses with an 8.8-ns duration were obtained.

  13. Processing of Diamond for Integrated Optic Devices Using Q-Switched Nd:YAG Laser at Different Wavelengths

    NASA Astrophysics Data System (ADS)

    Sudheer, S. K.; Pillai, V. P. Mahadevan; Nayar, V. U.

    In the present investigation, a Q-switched Nd:YAG laser is used to study the various aspects of diamond processing for fabricating integrated optic and UV optoelectronic devices. Diamond is a better choice of substrate compared to silicon and gallium arsenide for the fabrication of waveguides to perform operations such as modulation, switching, multiplexing, and filtering, particularly in the ultraviolet spectrum. The experimental setup of the present investigation consists of two Q-Switched Nd:YAG lasers capable of operating at wavelengths of 1064 nm and 532 nm. The diamond cutting is performed using these two wavelengths by making the "V"-shaped groove with various opening angle. The variation of material loss of diamond during cutting is noted for the two wavelengths. The cut surface morphology and elemental and structural analysis of graphite formed during processing in both cases are compared using scanning electron microscopy (SEM) and laser Raman spectroscopy. Both the Q-Switched Nd:YAG laser systems (at 1064 nm and 532 nm) show very good performance in terms of peak-to-peak output stability, minimal spot diameter, smaller divergence angle, higher peak power in Q-switched mode, and good fundamental TEM00 mode quality for processing natural diamond stones. Less material loss and minimal micro cracks are achieved with wavelength 532 nm whereas a better diamond cut surface is achieved with processing at 1064 nm with minimum roughness.

  14. Laser diode and pumped Cr:Yag passively Q-switched yellow-green laser at 543 nm

    NASA Astrophysics Data System (ADS)

    Yao, Y.; Ling, Zhao; Li, B.; Qu, D. P.; Zhou, K.; Zhang, Y. B.; Zhao, Y.; Zheng, Q.

    2013-03-01

    Efficient and compact yellow green pulsed laser output at 543 nm is generated by frequency doubling of a passively Q-switched end diode-pumped Nd:YVO4 laser at 1086 nm under the condition of sup-pressing the higher gain transition near 1064 nm. With 15 W of diode pump power and the frequency doubling crystal LBO, as high as 1.58 W output power at 543 nm is achieved. The optical to optical conversion efficiency from the corresponding Q-switched fundamental output to the yellow green output is 49%. The peak power of the Q-switched yellow green pulse laser is up to 30 kW with 5 ns pulse duration. The output power stability over 8 hours is better than 2.56% at the maximum output power. To the best of our knowledge, this is the highest watt-level laser at 543 nm generated by frequency doubling of a passively Q-switched end diode pumped Nd:YVO4 laser at 1086 nm.

  15. Tunable Q-switched thulium-doped Fiber Laser using multiwall carbon nanotube and Fabry-Perot Etalon filter

    NASA Astrophysics Data System (ADS)

    Ahmad, H.; Muhamad, A.; Sharbirin, A. S.; Samion, M. Z.; Ismail, M. F.

    2017-01-01

    In this paper, we demonstrate an electro-tunable Thulium-doped Fiber Laser (TDFL) using a voltage-controlled Fabry-Perot Etalon (FPE) filter with passive Q-switching capability, obtained by using a multi-walled carbon-nanotube (MWCNT) thin-film as a saturable absorber (SA). To the best of our knowledge, this is the first demonstration of a wavelength-tunable Q-switched TDFL using an FPE filter. The tunable TDFL has a wavelength-tuning range of 41.95 nm, from 1965.40 nm up to 2007.35 nm. Q-switching operation starts at a pump power of 94.72 mW and destabilizes at a maximum input pump power of 146.39 mW. By varying the pump power, the repetition rate and the pulse width can be tuned with a maximum tuning range of 15.5 kHz and 7.0 μs respectively. The laser also has a maximum pulse energy of 82.6 nJ and a peak power of 27.52 mW. The use of the MWCNT thin-film as an SA generates a stable Q-switching operation, which is verified by its relatively high signal-to-noise ratio at a value of 55.0 dB.

  16. Treatment of early-stage erythematotelangiectatic rosacea with a Q-switched 595-nm Nd:YAG laser.

    PubMed

    Goo, Boncheol Leo; Kang, Jin-Soo; Cho, Sung Bin

    2015-06-01

    Erythematotelangiectatic rosacea presents as persistent erythema and telangiectasia with frequent flushing and blushing on the facial and extrafacial skin. Additionally, papulopustular rosacea shows acneiform papules, pustules, and nodules with persistent plaque-form edema. Despite garnering only grade-C or -D level recommendations, a 585-nm or 595-nm flashlamp-pumped pulsed-dye laser can be considered as an effective therapeutic modality for the treatment of rosacea in patients who are refractory to topical and/or systemic treatments. In this report, treatment with a Q-switched 595-nm neodymium-doped yttrium aluminum garnet (Nd:YAG) laser with low non-purpuragenic fluence proved to be safe and effective in treating early-stage erythematotelangiectatic rosacea in two female Korean patients. Laser treatment for rosacea was delivered with the settings of pulse energy of 0.4-0.5 J/cm(2), pulse duration of 5-10 ns, 5-mm spot size, 5 Hz, and 500 shots. Additionally, we found that remarkable therapeutic effects were achieved for both rosacea and melasma by combining Q-switched quick pulse-to-pulse 1,064-nm Nd:YAG and Q-switched 595-nm Nd:YAG laser treatments, which required only the changing of handpieces equipped with solid dye. In conclusion, we suggest that treatment with a Q-switched 595-nm Nd:YAG laser with low fluence may provide an additional therapeutic option for treating early-stage erythematotelangiectatic rosacea.

  17. Treatment of nasal ala nodular congenital melanocytic naevus with carbon dioxide laser and Q-switched Nd:YAG laser.

    PubMed

    Zeng, Ying; Ji, Chenyang; Zhan, Kui; Weng, Weili

    2016-11-01

    Total excision of congenital melanocytic nevi (CMN) is not always feasible. We here present our experience of using carbon dioxide laser and Q-switched neodymium-doped yttrium-aluminum-garnet (Nd:YAG) laser to treat nodular CMN of the nasal ala. Q-switched Nd:YAG laser and/or carbon dioxide laser were used to treat eight cases of nasal ala nodular CMN. Carbon dioxide laser was utilized to ablate all visible melanocytic tissue within one session. Ablation was performed so as to reproduce the original anatomical contours as closely as possible. Recurrences were treated in the same way. Q-switched Nd:YAG laser was also used to irradiate all target lesions to achieve the desired end point within one session. The intervals between treatments were at least 8 weeks. Recurrence of melanocytic tissue, scar formation, pigmentation, depigmentation, and the degree of patient satisfaction were recorded at every visit. Two of the eight patients were treated with Q-switched Nd:YAG laser. Although, the lesion lightened in one of them, the hyperplastic tissue persisted. Eventually, these two patients, along with the remaining six patients, were successfully treated with a carbon dioxide laser. We recommend carbon dioxide laser treatment for nodular nasal CMN. This simple treatment does not involve skin flap transplantation and has good cosmetic outcomes. Although Q-switched Nd:YAG laser does lighten some nasal nodular CMNs, it does not eradicate the hyperplastic tissue, and is therefore not an effective treatment for nodular nasal CMN.

  18. Solid state saturable absorbers for Q-switching at 1 and 1.3μm: investigation and modeling

    NASA Astrophysics Data System (ADS)

    Šulc, Jan; Arátor, Pavel; Jelínková, Helena; Nejezchleb, Karel; Škoda, Václav; Kokta, Milan R.

    2008-02-01

    Yttrium and Lutecium garnets (YAG and LuAG) doped by Chromium or Vanadium ions (Cr 4+ or V 3+) were investigated as saturable absorbers potentially useful for passive Q-switching at wavelengths 1 μm and/or 1.3 μm. For comparison also color center saturable absorber LiF:F - II and Cobalt doped spinel (Co:MALO) were studied. Firstly, low power absorption spectra were recorded for all samples. Next, absorbers transmission in dependence on incident energy/power density was measured using the z-scan method. Crystals Cr:YAG, Cr:LuAG, V:YAG, and LiF:F - II were tested at wavelength 1064 nm. Therefore Alexandrite laser pumped Q-switched Nd:YAG laser was used as a radiation source (pulse length 6.9 ns, energy up to 1.5 mJ). Crystals V:YAG, V:LuAG, and Co:MALO were tested at wavelength 1338 nm. So diode pumped Nd:YAG/V:YAG microchip laser was used as a radiation source (pulse length 6.2 ns, energy up to 0.1 mJ). Using measured data fitting, and by their comparison with numerical model of a "thick" saturable absorber transmission for Q-switched Gaussian laser beam, following parameters were estimated: saturable absorber initial transmission T 0, saturation energy density w s, ground state absorption cross-section σ GSA, saturated absorber transmission T s, excited state absorption cross-section σ ESA, ratio γ = σ GSA/σ ESA, and absorbing ions density. For V:YAG crystal, a polarization dependence of T s was also investigated. With the help of rate equation numerical solution, an impact of saturable absorber parameters on generated Q-switched pulse properties was studied in plane wave approximation. Selected saturable absorbers were also investigated as a Q-switch and results were compared with the model.

  19. A self-injection locked, Q-switched, line-narrowed Ti:Al/sub 2/O/sub 3/ laser

    SciTech Connect

    Barnes, N.P.; Williams, J.A.; Barnes, J.C.; Lockard, G.E.

    1988-06-01

    Line-narrowing, Q-switched, and self-injection locking are studied independently and as a system. Line narrowing is shown both theoretically and experimentally to depend on the inverse square root of the pulse evolution time interval. Q switching of the Ti:Al/sub 2/O/sub 3/ laser is demonstrated and the laser output energy as a function of the Q-switch delay is investigated. Self-injection is demonstrated and the operation of the laser is explored as a function of loss and the Q-switch delay. Finally, self-injection locking is demonstrated and the performance as a function of the Q-switch delay is determined.

  20. Monitoring tree health with a dual-wavelength terrestrial laser scanner

    NASA Astrophysics Data System (ADS)

    Hancock, S.

    2013-12-01

    harvesting). Trees were arranged so that some were clearly visible to the scanner and could be analysed individually (a best case scenario) whilst others were grouped to form a denser, more realistic canopy (a worse case scenario). A method was developed to simultaneously extract canopy structure (leaf area, tree height and clumping) and leaf biochemistry (EWT) from the laser scanner data. These results were compared to ground to assess their accuracy. References Danson, F. M., Hetherington D., Morsdorf F., Koetz B., Allgower B., 2007. Forest canopy gap fraction from terrestrial laser scanning. IEEE Geoscience and Remote Sensing Letters, 4, 157-160. Gaulton R., Danson F. M., Ramirez F. A., Gunawan O., 2013. The potential of dual-wavelength laser scanning for estimating vegetation moisture content. Remote Sensing of Environment, 132, 32-39.

  1. Q-switched resonantly pumped Er:YAG laser with a fiber-like geometry

    NASA Astrophysics Data System (ADS)

    Bigotta, Stefano; Eichhorn, Marc

    2010-10-01

    Er3+:YAG eye-safe laser emitting at 1.6 μm is an interesting source for various applications such as remote sensing, ranging, designation and free-space communications for two main reasons: its emitting wavelength lies in a region of high atmospheric transmission and high sensor sensitivity and the resonant pumping into the 4I13/2 upper laser manifold ensures highly efficient operation. The recent availability of internal grating stabilized narrow linewidth, high-power laser diodes in the 1.53 μm range, makes this laser even more appealing. The only shortcoming to be solved for a really efficient resonantly diode pumped Er3+:YAG laser is how to have a good overlap between the pump radiation and the laser cavity mode. Indeed, due to up-conversion processes among the Er3+ ions, to achieve efficient lasers it is necessary to use low doped samples. This requires the use of rods with lengths of several cm that are not compatible with the low beam quality of the diode lasers. In this work, we report on a resonantly diode pumped Q-switched Er3+:YAG laser with a crystalline fibre-like geometry emitting at 1.64 μm. In this scheme, the pump radiation is confined into a 60 mm long crystal with a diameter of 1.2 mm thanks to the multiple total internal reflections (TIR) that occur on the barrel surface, allowing efficiently pumping of such a long crystal. A maximum output power of more than 14 W in continuous wave mode and pulse energies of 8 mJ in Q-switching mode have been observed, when pumped with - 40 W of absorbed power. Even if these values are still far from the performances reported using hybrid fibre-bulk laser scheme, these results clearly show that TIR-based Er3+:YAG fibre-shaped crystalline rod laser is a promising technology for the development of efficient high-power and high-energy eye-safe laser. Finally, the effect of thermal lensing on such crystalline fibre geometry is discussed.

  2. Water content contribution in calculus phantom ablation during Q-switched Tm:YAG laser lithotripsy.

    PubMed

    Zhang, Jian J; Rajabhandharaks, Danop; Xuan, Jason Rongwei; Wang, Hui; Chia, Ray W J; Hasenberg, Tom; Kang, Hyun Wook

    2015-01-01

    Q-switched (QS) Tm:YAG laser ablation mechanisms on urinary calculi are still unclear to researchers. Here, dependence of water content in calculus phantom on calculus ablation performance was investigated. White gypsum cement was used as a calculus phantom model. The calculus phantoms were ablated by a total 3-J laser pulse exposure (20 mJ, 100 Hz, 1.5 s) and contact mode with N=15 sample size. Ablation volume was obtained on average 0.079, 0.122, and 0.391  mm3 in dry calculus in air, wet calculus in air, and wet calculus in-water groups, respectively. There were three proposed ablation mechanisms that could explain the effect of water content in calculus phantom on calculus ablation performance, including shock wave due to laser pulse injection and bubble collapse, spallation, and microexplosion. Increased absorption coefficient of wet calculus can cause stronger spallation process compared with that caused by dry calculus; as a result, higher calculus ablation was observed in both wet calculus in air and wet calculus in water. The test result also indicates that the shock waves generated by short laser pulse under the in-water condition have great impact on the ablation volume by Tm:YAG QS laser.

  3. Accidental bilateral Q-switched neodymium laser exposure: treatment and recovery of visual function

    NASA Astrophysics Data System (ADS)

    Zwick, Harry; Stuck, Bruce E.; Dunlap, Weldon; Scales, David K.; Lund, David J.; Ness, James W.

    1998-05-01

    A 21 year old female was accidentally exposed in both eyes when she looked into the 10 cm exit aperture of a military laser designator emitting 1064 nm q-switched (30 ns) pulses at a 10 pulse per second rate. Steroid therapy (methylprednisolone sodium succinate) was initiated within 6 hours post exposure. Initial ophthalmoscopic observation revealed small contained macular hemorrhages in each eye. Fluorescein angiography (FA) showed minimal leakage. Visual acuity was 20/100 and 20/60 in OD and OS respectively. Contrast sensitivity in both eyes was depressed across all spatial frequencies by more than 1.5 log units. At four weeks post exposure, no significant macular scarring was apparent and visual acuity returned to 20/25 in both eyes. Contrast sensitivity had improved to normal levels with a peak at 3 cycles/degree. At one year post exposure, visual acuity was 20/13 in both eyes and measures of contrast sensitivity were within normal limits. During the course of recovery, the patient's fixation shifted from a slightly superior temporal site back to the central foveal region. The foveal lesion sites were still evident by ophthalmoscopy and Amsler grid measurements but were deemed functional when the patient placed small targets generated by the scanning laser ophthalmoscope in the lesion site for discrimination. This outcome indicates remarkable recovery of visual function and suggests that early administration of steroids may assist in preserving the natural neural recovery process of the photoreceptor matrix by minimizing intraretinal scar formation.

  4. Passively Q-switched Ho:YLF laser pumped by Tm3+-doped fiber laser

    NASA Astrophysics Data System (ADS)

    Yang, Chao; Ju, Youlun; Yao, Baoquan; Dai, Tongyu; Duan, Xiaoming; Li, Jiang; Ding, Yu; Liu, Wei; Pan, Yubai; Li, Chaoyu

    2016-03-01

    We demonstrate a compact and efficient passively Q-switched (PQS) Ho:YLF laser pumped by a self-made all-fiber laser. Firstly, we design and make an all-fiber laser operating at 1940 nm with a slope efficiency of 40.6%. Then, the all-fiber laser was used to pump Ho:YLF laser directly. In the CW (continues-wave) operation Ho:YLF laser, the maximum output power was 7.79 W, corresponding to the slope efficiency of 55.2%. Using Cr2+:ZnS as the saturable absorber, the average power of 6.03 W was achieved with the slope efficiency of 45.9%. The shortest pulse duration was 15.6 ns and the pulse repetition frequency was 2.3 kHz at the pump power of 20.4 W. The pulse energy was a constant as 2.7 mJ when the pump power exceeded 15 W. The beam quality factor of M2 was 1.05, indicating nearly diffraction limited beam propagation.

  5. Highly efficient high power CW and Q-switched Ho:YLF laser

    NASA Astrophysics Data System (ADS)

    Kwiatkowski, J.

    2015-06-01

    An efficient operation of a Ho:YLF laser pumped by a Tm-doped fibre laser is reported. The research in a continuous-wave (CW) operation was done for two crystals of the same 0.5 at.%Ho dopant concentration and with different lengths (3×3×30 mm3 and 3×3×50 mm3). For an output coupling transmission of 20% and a crystal length of 50 mm, the maximum CWoutput power of 38.9 W for 81.4 W of incident pump power, corresponding to the slope efficiency of 52.3% and optical-to-optical conversion efficiency of 47.8% (determined with respect to the incident pump power) was achieved. The highest opti- cal-to-optical conversion efficiency of 70.2% with respect to the absorbed pump power was obtained. The influence of a heat-sink cooling water temperature on theCWlaser performance was studied. For a Q-switched operation the pulse repe- tition frequency (PRF) was changed from 2 to 10 kHz. The maximum average output power of 34.1 W at the PRF of 10 kHz was obtained for a 50 mm holmium crystal length. For 2 kHz PRF and 71.9 W of incident pump power, pulse energies of 13.7 mJ with a 21 ns FWHM pulse width corresponding to 652 kW peak power were recorded.

  6. Simulation of medical Q-switch flash-pumped Er:YAG laser

    NASA Astrophysics Data System (ADS)

    -Yan-lin, Wang; Huang-Chuyun; Yao-Yucheng; Xiaolin, Zou

    2011-01-01

    Er: YAG laser, the wavelength is 2940nm, can be absorbed strongly by water. The absorption coefficient is as high as 13000 cm-1. As the water strong absorption, Erbium laser can bring shallow penetration depth and smaller surrounding tissue injury in most soft tissue and hard tissue. At the same time, the interaction between 2940nm radiation and biological tissue saturated with water is equivalent to instantaneous heating within limited volume, thus resulting in the phenomenon of micro-explosion to removal organization. Different parameters can be set up to cut enamel, dentin, caries and soft tissue. For the development and optimization of laser system, it is a practical choice to use laser modeling to predict the influence of various parameters for laser performance. Aim at the status of low Erbium laser output power, flash-pumped Er: YAG laser performance was simulated to obtain optical output in theory. the rate equation model was obtained and used to predict the change of population densities in various manifolds and use the technology of Q-switch the simulate laser output for different design parameters and results showed that Er: YAG laser output energy can achieve the maximum average output power of 9.8W under the given parameters. The model can be used to find the potential laser systems that meet application requirements.

  7. Linearly polarized Q-switched ceramic laser made with anisotropic nanostructured thin films.

    PubMed

    Doucet, Alexandre; Beydaghyan, Gisia; Ashrit, Pandurang V; Bisson, Jean-François

    2016-07-01

    A polarizing laser mirror was made of an alternating sequence of low and high refractive index layers of titanium oxide using glancing angle deposition (GLAD). Large refractive index contrast and large birefringence, reaching 0.5 and 0.1, respectively, could be obtained from one single raw material by changing the deposition conditions. The laser mirror could withstand a train of 2.7 ns, single-mode pulses at 680 Hz, λ=1030  nm, and peak power density of 670  MW/cm2 when used as an output coupler of a passively Q-switched (Yb0.1Y0.9)3Al5O12 ceramic laser. The polarization extinction ratio was found to be better than 30 dB both in continuous-wave and pulsed regimes. These results indicate that polarizing laser mirrors made from nanostructured thin films with GLAD, in addition to being simple to fabricate, can withstand high pulse energy density.

  8. High-damage-resistant tungsten disulfide saturable absorber mirror for passively Q-switched fiber laser.

    PubMed

    Chen, Hao; Chen, YuShan; Yin, Jinde; Zhang, Xuejun; Guo, Tuan; Yan, Peiguang

    2016-07-25

    In this paper, we demonstrate a high-damage-resistant tungsten disulfide saturable absorber mirror (WS2-SAM) fabricated by magnetron sputtering technique. The WS2-SAM has an all-fiber-integrated configuration and high-damage-resistant merit because the WS2 layer is protected by gold film so as to avoid being oxidized and destroyed at high pump power. Employing the WS2-SAM in an Erbium-doped fiber laser (EDFL) with linear cavity, the stable Q-switching operation is achieved at central wavelength of 1560 nm, with the repetition rates ranging from 29.5 kHz to 367.8 kHz and the pulse duration ranging from 1.269 μs to 154.9 ns. For the condition of the maximum pump power of 600 mW, the WS2-SAM still works stably with an output power of 25.2 mW, pulse energy of 68.5 nJ, and signal-noise-ratio of 42 dB. The proposed WS2-SAM configuration provides a promising solution for advanced pulsed fiber lasers with the characteristics of high damage resistance, high output energy, and wide tunable frequency.

  9. High-power passively Q-switched Nd:KGW laser pumped at 877 nm

    NASA Astrophysics Data System (ADS)

    Huang, K.; Ge, W. Q.; Zhao, T. Z.; Feng, C. Y.; Yu, J.; He, J. G.; Xiao, H.; Fan, Z. W.

    2016-06-01

    In this work, we demonstrate, for the first time, a high-power passively Q-switched Ng-cut Nd3+:KGd(WO4)2/Cr4+:YAG laser pumped at 877 nm. The maximum average output power of ~1.6 W is obtained at the pump power of 5.22 W, when a saturable absorber with 98 % of initial transmission is used. The corresponding pulse energy is up to 16 µJ. The maximum pulse energy of 25.3 µJ is achieved at a repetition rate of 59 kHz, by employing a saturable absorber with 95 % of initial transmission. The corresponding pulse width and average output power are 89.0 ns and 1.5 W, respectively. A careful cavity design and a good thermal management ensure nearly TEM00 output with M 2 ≤ 1.22 within the whole range of operation in both N p and N m directions at 877 nm pump.

  10. Short-term effects of Q-switched ruby laser on monkey anterior chamber angle

    SciTech Connect

    Bonney, C.H.; Gaasterland, D.E.; Rodrigues, M.M.; Raymond, J.J.; Donohoo, P.

    1982-03-01

    Three Q-switched ruby laser pulses were applied to the trabecular meshwork of 10 monkey eyes. Pulse energies ranging from 20 to 110 mJ were studied. The spot size ranged from 100 to 200 micrometer (in air), and the pulse durations was 28 sec. Gonioscopic examinations showed a graded response from no appreciable change at 20 mJ per pulse to marked disruption of anterior chamber angle structures at 100 mJ or more per pulse. Perfusions done within an hour of treatment showed no consistent alteration of the outflow facility. Scanning electron microscopy demonstrated the graded anterior chamber angle response. No disruption of the angle structures was seen after the 20 mJ treatment, but discrete trabecular damage occurred after treatments with 25 mJ. After pulses equal to or greater than 45 mJ the anterior chamber angle structures were markedly altered. The power density causing extensive tissue disruption was equal to or greater than 150 X 10(8) watts/cm2. In each specimen with an identifiable trabecular lesion, tissue debris and endothelial edema were found on the adjacent inner surface of the cornea. Tearing of Descemet's membrane next to the trabecular meshwork occurred with the 100 mJ pulses.

  11. Multiparameter bifurcations and mixed-mode oscillations in Q-switched CO2 lasers.

    PubMed

    Doedel, Eusebius J; Pando L, Carlos L

    2014-05-01

    We study the origin of mixed-mode oscillations and related bifurcations in a fully molecular laser model that describes CO2 monomode lasers with a slow saturable absorber. Our study indicates that the presence of isolas of periodic mixed-mode oscillations, as the pump parameter and the cavity-frequency detuning change, is inherent to Q-switched CO2 monomode lasers. We compare this model, known as the dual four-level model, to the more conventional 3:2 model and to a CO2 laser model for fast saturable absorbers. In these models, we find similarities as well as qualitative differences, such as the different nature of the homoclinic tangency to a relevant unstable periodic orbit, where the Gavrilov-Shilnikov theory and its extensions may hold. We also show that there are isolas of periodic mixed-mode oscillations in a model for CO2 lasers with modulated losses, as the pump parameter varies. The coarse-grained bifurcation diagrams of the periodic mixed-mode oscillations in these models suggest that these oscillations belong to similar classes.

  12. In vitro assessment of fiber sweeping angle during Q-switched 532-nm laser tissue ablation

    NASA Astrophysics Data System (ADS)

    Rajabhandharaks, Danop; Kang, Hyun Wook; Ko, Woo Jin; Stinson, Douglas; Choi, Benjamin

    2011-03-01

    Photoselective vaporization of the prostate (PVP) has been widely used to treat benign prostatic hyperplasia (BPH). It is well regarded as a safe and minimally invasive procedure and an alternative to the gold standard transurethral resection of the prostate (TURP). Despite of its greatness, as well aware of, the operative procedure time during the PVP is still prolonged. Such attempts have been tried out in order to shorten the operative time and increase its efficacy. However, scientific study to investigate techniques used during the PVP is still lacking. The objective of this study is to investigate how sweeping angle might affect the PVP performance. Porcine kidneys acquired from a local grocery store were used (N=140). A Q-switched 532-nm GreenLight XPSTM (American Medical Systems, Inc., MN, USA), together with 750- μm core MoXyTM fiber, was set to have power levels of 120 W and 180 W. Treatment speed and sweeping speed were fixed at 2 mm/s and 0.5 sweep/s, respectively. Sweeping angles were varied from 0 (no sweeping motion) to 120 degree. Ablation rate, depth, and coagulation zone were measured and quantified. Tissue ablation rate was peaked at 15 and 30 degree for both 120- and 180-W power levels and dramatically decreased beyond 60 degree. At 180 W, ablation rate increased 20% at 30 degree compared to 0 degree. This study demonstrated that ablation rate could be maximized and was contingent upon sweeping angle.

  13. Low-energy, Q-switched ruby laser iridotomies in Macaca mulatta.

    PubMed

    Bonney, C H; Gaasterland, D E

    1979-03-01

    Laser iridotomies have been pursued as a means of performing anterior segments surgery as a virtually noninvasive procedure. An ideal single laser pulse technique has been elusive. In this study, iridotomies in rhesus monkeys were produced with a single exposure to a Q-switched ruby laser pulse. The iridotomy formation was accompanied by acoustic wave generation, bubble formation, and explosive tissue disruption, evidence of a nonlinear laser-iris interaction. The average energies at which these iridotomies were produced ranged between 18 and 48 mJ, some of the lowest energies reported for a laser iridotomy. Corneal changes were observed both at the epithelium and at the endothelium in some, but not all, of the eyes exposed. The epithelial changes morphologically resembled nonlinear damage reported for transparent solids. Damage to physical materials has been attributed to stimulated Brillouin scattering, a mechanism that may also play a role at the cornea. Consideration of such phenomena should be a part of the clinical evaluation prior to exposure of a cornea to high-power laser pulses. Although the endothelial change was more difficult to analyze, a shock-wave effect could not be discounted.

  14. Q -switched laser at 912 nm using ground-state-depleted neodymium in yttrium orthosilicate

    SciTech Connect

    Beach, R.; Albrecht, G.; Solarz, R.; Krupke, W.; Comaskey, B.; Mitchell, S. ); Brandle, C.; Berkstresser, G. )

    1990-09-15

    A ground-state-depleted laser is demonstrated in the form of a {ital Q}-switched oscillator operating at 912 nm. By using Nd{sup 3+} as the active ion and Y{sub 2}SiO{sub 5} as the host material, the laser transition is from the lowest-lying Stark level of the Nd{sup 3+} {sup 4}{ital F}{sub 3/2} level to a Stark level 355 cm{sup {minus}1} above the lowest-lying one in the {sup 4}{ital I}{sub 9/2} manifold. The necessity of depleting the ground {sup 4}{ital I}{sub 9/2} manifold is evident for this level scheme as transparency requires a 10% inversion. To achieve the high excitation levels required for the efficient operation of this laser, bleach-wave pumping using an alexandrite laser at 745 nm has been employed. With KNbO{sub 3}, noncritical phase matching is possible at 140{degree} C using {ital d}{sub 32} and is demonstrated.

  15. Treatment of persistent Mongolian spots with Q-switched alexandrite laser.

    PubMed

    Kagami, Shinji; Asahina, Akihiko; Uwajima, Yuta; Miyamoto, Akie; Yamada, Daisuke; Shibata, Sayaka; Yamamoto, Mizuho; Masui, Yuri; Sato, Shinichi

    2012-11-01

    Mongolian spots are congenital and confluent hyperpigmented areas that are usually grayish blue in color. They are found most frequently in the sacral region in infants and typically disappear during childhood. Occasionally, they persist to adulthood. We retrospectively examined outcomes of laser treatment of persistent Mongolian spots. We used Q-switched alexandrite laser to treat persistent Mongolian spots of 16 Japanese patients at 14 years old or older. A good therapeutic outcome was achieved overall; however, postinflammatory hyperpigmentation and hypopigmentation were observed in two patients, respectively. While laser treatment was effective for all seven patients with extrasacral Mongolian spots, four out of ten patients with sacral Mongolian spots were refractory to treatment. Of these patients, two received laser irradiation only twice and abandoned treatment, simply because of unsatisfactory results without any adverse events. The other two patients received treatments at intervals of 3 months, which resulted in postinflammatory hyperpigmentation. Contrary to children, who generally show good response after two or three sessions of irradiation, we should consider more frequent irradiation, longer intervals between treatment sessions, and use of bleaching creams in the treatment of persistent sacral Mongolian spots in adults.

  16. Light and electron microscopic analysis of tattoos treated by Q-switched ruby laser

    SciTech Connect

    Taylor, C.R.; Anderson, R.R.; Gange, R.W.; Michaud, N.A.; Flotte, T.J. )

    1991-07-01

    Short-pulse laser exposures can be used to alter pigmented structures in tissue by selective photothermolysis. Potential mechanisms of human tattoo pigment lightening with Q-switched ruby laser were explored by light and electron microscopy. Significant variation existed between and within tattoos. Electron microscopy of untreated tattoos revealed membrane-bound pigment granules, predominantly within fibroblasts and macrophages, and occasionally in mast cells. These granules contained pigment particles ranging from 2-in diameter. Immediately after exposure, dose-related injury was observed in cells containing pigment. Some pigment particles were smaller and lamellated. At fluences greater than or equal to 3 J/cm2, dermal vacuoles and homogenization of collagen bundles immediately adjacent to extracellular pigment were occasionally observed. A brisk neutrophilic infiltrate was apparent by 24 h. Eleven days later, the pigment was again intracellular. Half of the biopsies at 150 d revealed a mild persistent lymphocytic infiltrate. There was no fibrosis except for one case of clinical scarring. These findings confirm that short-pulse radiation can be used to selectively disrupt cells containing tattoo pigments. The physial alteration of pigment granules, redistribution, and elimination appear to account for clinical lightening of the tattoos.

  17. Visible supercontinuum generation in photonic crystal fiber using various harmonics of subnanosecond Q-switched laser

    NASA Astrophysics Data System (ADS)

    Vengelis, Julius; Jarutis, Vygandas; Sirutkaitis, Valdas

    2016-09-01

    We report results of supercontinuum generation in highly nonlinear polarization maintaining photonic crystal fiber (PCF) using the first or second harmonics of a subnanosecond passively Q-switched Nd:YAG microlaser. The Nd:YAG microlaser generated 50 μJ energy 300 ps duration pulses at 1064 nm with a kilohertz repetition rate. We demonstrated that we can expand the supercontinuum spectrum to cover the whole visible range and beyond using either first or second harmonics of our pump laser in the case of such pump pulse durations. In the case of a first-harmonic pump (λp=1064 nm), the supercontinuum extended from 400 to 1300 nm and in the case of a second-harmonic pump (λp=532 nm), it extended from 400 to 900 nm. In addition, we compared the supercontinuum evolution and dependence on pump pulse energy in both cases. We also performed numerical simulations of supercontinuum generation in PCF using an improved approach. The generalized nonlinear Schrödinger equation was modified so that numerical simulations would yield greater accuracy in the case of longer (300 ps) pulses. The simulated supercontinuum spectra display the same qualitative features as that measured in the experiment.

  18. Performance model for optical extraction from a Q-switched chemical oxygen-iodine laser

    NASA Astrophysics Data System (ADS)

    Copeland, D. A.; Bauer, A. H.; Jones, K. D.

    1993-03-01

    A comprehensive time-dependent model for optical extraction from a Q-switched supersonic oxygen-iodine laser is described. Gas flow is treated by using an unsteady, premixed, quasi-1D model that accounts for gas motion and expansion as well as heat release in the cavity. The model uses a simplified, temperature-dependent, chemical kinetics package that consists of several reactions among the 3Sigma, 1Delta, and 1Sigma states of oxygen, atomic and molecular iodine, water, and helium. Hyperfine relaxation effects on the gain and optical extraction from the 3-4 transition line are treated by using a simple four-level laser model. An efficient algorithm for solving the coupled medium and optical extraction equations, in conjunction with a geometric model of an unstable confocal resonator, is used to examine optical extraction from the medium as a function of pulse repetition rate, duty cycle, and optical mode width. It is shown that the output power may exhibit flow-induced relaxation oscillations.

  19. Morphologic evaluations of Q-switched Nd:YAG laser injury of human retina

    NASA Astrophysics Data System (ADS)

    Scales, David K.; Schuschereba, Steven T.; Lund, David J.; Stuck, Bruce E.

    1997-05-01

    Depiction of the cellular and immune responses in the human model is critical to design rational therapies preventing/limiting cellular destruction and ultimately functional visual loss following acute laser injuries. We report the light and electron microscopy histologic findings in a controlled ocular human laser exposure. Following informed consent, the normal eye of a patient scheduled to undergo exenteration for invasive carcinoma of the orbit was exposed to both continuous wave and Q-switched lasers. Four hours prior to exenteration, argon G lesions were placed in the superior/temporal quadrant and Nd:YAG lesions were placed in the inferior/temporal quadrant. After enucleation, the retina was prepared for routine light and transmission electron microscopy. Histology of the argon G lesions showed primarily photoreceptor and RPE photocoagulation damage. Neutrophil adhesion was limited within the choroid and no neutrophils were observed in the subretinal space. In contrast, the 4 hr Nd:YAG lesions showed extensive retinal disruption, hemorrhage within subretinal and intraretinal spaces, neutrophil accumulation in the retina, and an extensive neutrophil chemotaxic and emigration response in the choroid. Severe laser injuries elicit a significant neutrophil response by 4 hr, suggesting that neutrophils should be an early stage therapeutic target.

  20. Design and construction of Q-switched Nd:YAG laser system for LIBS measurements

    NASA Astrophysics Data System (ADS)

    Elsayed, Khaled.; Imam, Hisham; Harfoosh, Amro; Hassebo, Yasser; Elbaz, Yasser; Aziz, Mouayed; Mansour, Mohy

    2012-02-01

    A passive, Q-switched pulsed, Nd:YAG laser system was designed and built, which can provide a potential compact robust laser source for portable laser induced breakdown spectroscopy systems. The developed laser system operates at 1064 nm. Each laser shot contains a train of pulses having maximum total output energy of 170 mJ. The number of pulses varies from 1-6 pulses in each laser shot depending on the pump energy. The pulse width of each pulse ranges from 20 to 30 ns. The total duration of the output pulse train is within 300 μs. The multi-pulse nature of the laser shots was employed to enhance the LIBS signal. To validate the system, LIBS measurements and analysis were performed on ancient ceramic samples collected from Al-Fustat excavation in Old Cairo. The samples belong to different Islamic periods in Egypt history. The results obtained are highly indicative that useful information can be provided to archeologists for use in restoring and repairing of precious archeological objects.

  1. Dual-wavelength technology used in anti-interference for long-range and short-distance detection

    NASA Astrophysics Data System (ADS)

    Zhang, Haojun; Zhao, Jianlin; Ren, Ju; Sun, Limin

    2009-10-01

    Technology of interference becomes more advancing. Adopting fog and aerosols is the best way to interfere optical detection. Due to the fog and aerosols, target recognition becomes difficult under this environment. In the present paper a method is given to solve this problem in a simple way. A dual-wavelength technology used in anti-interfere for long range and short distance detection is introduced in this paper, which can discriminate the backscattering reflection of fog and aerosols. In the present work the scattering character of the special fog and aerosols environment is calculated using the Rayleigh scattering method and Mie scattering method. The scattering characters in different environment are analyses using two wavelengths, i.e. one wavelength lies in ultraviolet wave band, the other in near infrared wave band. The results indicated that the ratio of proportion-discrimination is usually greater than 2, and deeper the strength of the fog and aerosols, the greater the ratio. This method also validated by experiment. In the present study, three kinds of wavelength such as 405nm, 670nm and 808nm are adopted. The intensity data collected shows that the ratio is greater than 3. The performance and working principle of the system and its components are analyzed in details. Based on the full system, the dual-wavelength technology can be well applied. The result of the experiments also proves that the technology is efficient, especially in the heavy fog and aerosols environment. The dual wavelength method can be used for long range and short distance detection.

  2. A Dual Wavelength Echidna® Lidar (DWEL) for Forest Structure Retrieval

    NASA Astrophysics Data System (ADS)

    Strahler, A. H.; Douglas, E. S.; Martel, J.; Cook, T.; Mendillo, C.; Marshall, R. A.; Chakrabarti, S.; Schaaf, C.; Woodcock, C. E.; Li, Z.; Yang, X.; Culvenor, D.; Jupp, D.; Newnham, G.; Lovell, J.

    2012-12-01

    A newly-constructed, ground-based lidar scanner designed for automated retrieval of forest structure, the Dual Wavelength Echidna Lidar (DWEL), separates laser "hits" of leaves from hits of trunks and branches using simultaneous laser pulses at 1548 nm, where leaf water content produces strong absorption, and at 1064 nm, where leaves and branches have similar reflectances. The DWEL uses a rotating mirror scan mechanism on a revolving mount, coupled with full digitization of return waveforms, to identify, locate, and parameterize scattering events in the three-dimensional space around the scanner. In the DWEL instrument, the two measurement lasers are triggered simultaneously. Laser pulses are sharply peaked; full-width half-max pulse length of the lasers is 5.1 ns, corresponding to 1.53 m in distance. The laser pulses are expanded and collimated to a 6-mm beam diameter (1/e2), then shaped into a top-hat cross section using a diffraction apparatus. Interchangeable optics provide a beam divergence of 1.25-, 2.5-, or 5-mrad. A mirror and two dichroic filters combine the beams and join them with a visible green continuous-wave marker laser. The combined beam is guided along an optical path to the 10-cm rotating scan mirror. Scan encoders in zenith and azimuth directions resolve the pointing of the instrument to 215 units per 2π radians. Scan resolution has three settings: 1-, 2-, and 4-mrad. Scan time varies with resolution: 11 min at 4 mrad; 41 min at 2 mrad; and 2.7 hr at 1 mrad. The return beam enters the 10-cm diameter Newtonian-Nasmyth telescope and is directed to the receiver assembly, which splits the return beam using a dichroic filter and narrowband pass filters. Two 0.5 mm InGaAs photodiodes measure the return signal, which is sampled by two digitizers at 2 gigasamples per second with 10-bit precision. This provides a 7.5-cm sampling of the 1.53 m pulse, allowing very good reconstruction of the return waveform. The designed signal-to-noise ratio is 10:1 (8

  3. Dual-wavelength phase-shifting digital holography selectively extracting wavelength information from wavelength-multiplexed holograms.

    PubMed

    Tahara, Tatsuki; Mori, Ryota; Kikunaga, Shuhei; Arai, Yasuhiko; Takaki, Yasuhiro

    2015-06-15

    Dual-wavelength phase-shifting digital holography that selectively extracts wavelength information from five wavelength-multiplexed holograms is presented. Specific phase shifts for respective wavelengths are introduced to remove the crosstalk components and extract only the object wave at the desired wavelength from the holograms. Object waves in multiple wavelengths are selectively extracted by utilizing 2π ambiguity and the subtraction procedures based on phase-shifting interferometry. Numerical results show the validity of the proposed technique. The proposed technique is also experimentally demonstrated.

  4. Design and fabrication of a diffractive beam splitter for dual-wavelength and concurrent irradiation of process points.

    PubMed

    Amako, Jun; Shinozaki, Yu

    2016-07-11

    We report on a dual-wavelength diffractive beam splitter designed for use in parallel laser processing. This novel optical element generates two beam arrays of different wavelengths and allows their overlap at the process points on a workpiece. To design the deep surface-relief profile of a splitter using a simulated annealing algorithm, we introduce a heuristic but practical scheme to determine the maximum depth and the number of quantization levels. The designed corrugations were fabricated in a photoresist by maskless grayscale exposure using a high-resolution spatial light modulator. We characterized the photoresist splitter, thereby validating the proposed beam-splitting concept.

  5. Fabrication of dual-wavelength diffractive beam splitters using maskless optical lithography with a digital micromirror device

    NASA Astrophysics Data System (ADS)

    Amako, Jun; Yu, Shinozaki

    2016-03-01

    In this paper, we demonstrate a dual-wavelength diffractive beam splitter to be used in parallel laser processing. The novel optical element, which is formed in a transparent material, generates two beam arrays at different wavelengths and allows their overlap at the process points on a workpiece. Since the splitter has a stochastically designed, complex, and deep surface profile, there is limited freedom in selecting a fabrication method. We designed the splitter using a simulated annealing algorithm and fabricated it in a photoresist through maskless exposure by using a digital micromirror device. We characterized the designed splitter, thereby corroborating the proposed beam-splitting concept.

  6. Q-switched and mode-locked Er{sup 3+}-doped fibre laser using a single-multi-single fibre filter and piezoelectric

    SciTech Connect

    Ji Wang; Yunjun Zhang; Aotuo Dong; Xiaoxin Xu; Youlun Ju; Baoquan Yao

    2014-04-28

    The active Q-switched and passive mode-locked Er{sup 3+}-doped all-fibre laser is presented. The fibre laser centre wavelength is located at 1563 nm and determined by the homemade singlemulti- single (SMS) in-line fibre filter. The laser spectrum width is nearly 0.1 nm. The active Q-switched mechanism relies on the polarisation state control using a piezoelectric to press a segment of passive fibre on the circular cavity. The nonlinear polarisation rotation technology is used to realise the passive self-started modelocked operation. In the passive mode-locked regimes, the output average power is 2.1 mW, repetition frequency is 11.96 MHz, and single pulse energy is 0.18 nJ. With the 100-Hz Q-switched regimes running, the output average power is 1.5 mW. The total Q-switched pulse width is 15 μs, and every Q-switched pulse is made up by several tens of mode-locked peak pulses. The calculated output pulse energy of the Q-switched fibre laser is about 15 μJ, and the energy of every mode-locked pulse is about 64–68 nJ during a Q-switched pulse taking into account the power fraction propagating between pulses. (lasers)

  7. Q-switched and mode-locked Er3+-doped fibre laser using a single-multi-single fibre filter and piezoelectric

    NASA Astrophysics Data System (ADS)

    Wang, Ji; Zhang, Yunjun; Dong, Aotuo; Xu, Xiaoxin; Ju, Youlun; Yao, Baoquan

    2014-04-01

    The active Q-switched and passive mode-locked Er3+-doped all-fibre laser is presented. The fibre laser centre wavelength is located at 1563 nm and determined by the homemade singlemulti- single (SMS) in-line fibre filter. The laser spectrum width is nearly 0.1 nm. The active Q-switched mechanism relies on the polarisation state control using a piezoelectric to press a segment of passive fibre on the circular cavity. The nonlinear polarisation rotation technology is used to realise the passive self-started modelocked operation. In the passive mode-locked regimes, the output average power is 2.1 mW, repetition frequency is 11.96 MHz, and single pulse energy is 0.18 nJ. With the 100-Hz Q-switched regimes running, the output average power is 1.5 mW. The total Q-switched pulse width is 15 μs, and every Q-switched pulse is made up by several tens of mode-locked peak pulses. The calculated output pulse energy of the Q-switched fibre laser is about 15 μJ, and the energy of every mode-locked pulse is about 64-68 nJ during a Q-switched pulse taking into account the power fraction propagating between pulses.

  8. Yb- and Er-doped fiber laser Q-switched with an optically uniform, broadband WS2 saturable absorber

    PubMed Central

    Zhang, M.; Hu, Guohua; Hu, Guoqing; Howe, R. C. T.; Chen, L.; Zheng, Z.; Hasan, T.

    2015-01-01

    We demonstrate a ytterbium (Yb) and an erbium (Er)-doped fiber laser Q-switched by a solution processed, optically uniform, few-layer tungsten disulfide saturable absorber (WS2-SA). Nonlinear optical absorption of the WS2-SA in the sub-bandgap region, attributed to the edge-induced states, is characterized by 3.1% and 4.9% modulation depths with 1.38 and 3.83 MW/cm2 saturation intensities at 1030 and 1558 nm, respectively. By integrating the optically uniform WS2-SA in the Yb- and Er-doped laser cavities, we obtain self-starting Q-switched pulses with microsecond duration and kilohertz repetition rates at 1030 and 1558 nm. Our work demonstrates broadband sub-bandgap saturable absorption of a single, solution processed WS2-SA, providing new potential efficacy for WS2 in ultrafast photonic applications. PMID:26657601

  9. Passively Q-switched erbium doped fiber laser based on double walled carbon nanotubes-polyvinyl alcohol saturable absorber

    NASA Astrophysics Data System (ADS)

    Mohammed, D. Z.; Al-Janabi, A. H.

    2016-11-01

    A passively Q-switched Er-doped fiber laser with a ring cavity operating at 1568.6 nm is demonstrated using a saturable absorber based on a double walled carbon nanotubes film, which is prepared using polyvinyl alcohol as a host polymer. The Q-switching operation is achieved at a low pump threshold of 40 mW. The proposed fiber laser produces stable pulses train of repetition rate ranging from 14.7 KHz to 47 KHz as the pump power increases from threshold to 203 mW. The minimum recorded pulse width was 4.6 µs at 203 mW, while the highest energy obtained was 102.1 nJ.

  10. Lidar-radar velocimetry using a pulse-to-pulse coherent rf-modulated Q-switched laser.

    PubMed

    Vallet, M; Barreaux, J; Romanelli, M; Pillet, G; Thévenin, J; Wang, L; Brunel, M

    2013-08-01

    An rf-modulated pulse train from a passively Q-switched Nd:YAG laser has been generated using an extra-cavity acousto-optic modulator. The rf modulation reproduces the spectral quality of the local oscillator. It leads to a high pulse-to-pulse phase coherence, i.e., phase memory, over thousands of pulses. The potentialities of this transmitter for lidar-radar are demonstrated by performing Doppler velocimetry on indoor moving targets. The experimental results are in good agreement with a model based on elementary signal processing theory. In particular, we show experimentally and theoretically that lidar-radar is a promising technique that allows discrimination between translation and rotation movements. Being independent of the laser internal dynamics, this scheme can be applied to any Q-switched laser.

  11. CONTROL OF LASER RADIATION PARAMETERS: Computational and experimental study of a Q-switched cw chemical HF/DF laser

    NASA Astrophysics Data System (ADS)

    Aleksandrov, Boris S.; Kuprenyuk, V. I.; Maksimov, Yurii P.; Mashendzhinov, Viktor I.; Rodionov, A. Yu; Rotinyan, Mikhail A.; Sudarikov, V. V.; Tret'yakov, Nikolai E.; Fedorov, Igor'A.; Etsina, Alla L.

    2007-06-01

    The energy and temporal parameters of radiation from a cw chemical medium-size HF/DF laser mechanically Q-switched by a mirror rotating at a frequency of up to 1 kHz are calculated and studied experimentally. The peak power of laser pulses in the repetitively pulsed regime exceeds the cw output power of the HF laser at least by a factor of four. The average power in the repetitively pulses regime is lower than that in the cw regime, but it increases (approximately doubles) with increasing modulation frequency. The time of the complete recovery of the gain profile in the active medium is measured to be 6-7 μs. Two numerical models are developed which describe the dynamics of Q-switched HF and DF lasers. Some specific features of the operation of these lasers are analysed with the help of these models.

  12. Sub-20-ps pulses from a passively Q-switched microchip laser at 1  MHz repetition rate.

    PubMed

    Mehner, Eva; Bernard, Benjamin; Giessen, Harald; Kopf, Daniel; Braun, Bernd

    2014-05-15

    We present a 50 μm Nd3+:YVO4 microchip laser that is passively Q-switched by a semiconductor saturable absorber mirror. To reduce handling problems caused by the small crystal dimensions, the 50 μm Nd3+:YVO4 crystal is optically bonded to an undoped YVO4 crystal of a length of about 500 μm. By using a saturable absorber mirror with an effective modulation depth of >10% the system is able to deliver 16 ps pulses at a repetition rate of up to 1.0 MHz. The average laser power is 16 mW at 1064 nm. To our knowledge these are the shortest Q-switched pulses ever reported from a solid-state laser. The limits in terms of pulse width, repetition rate, output power, and system stability are discussed. Additionally, continuous-wave behavior is analyzed. Experimental data is compared with the simulation results of the coupled rate equations.

  13. Yb- and Er-doped fiber laser Q-switched with an optically uniform, broadband WS2 saturable absorber

    NASA Astrophysics Data System (ADS)

    Zhang, M.; Hu, Guohua; Hu, Guoqing; Howe, R. C. T.; Chen, L.; Zheng, Z.; Hasan, T.

    2015-12-01

    We demonstrate a ytterbium (Yb) and an erbium (Er)-doped fiber laser Q-switched by a solution processed, optically uniform, few-layer tungsten disulfide saturable absorber (WS2-SA). Nonlinear optical absorption of the WS2-SA in the sub-bandgap region, attributed to the edge-induced states, is characterized by 3.1% and 4.9% modulation depths with 1.38 and 3.83 MW/cm2 saturation intensities at 1030 and 1558 nm, respectively. By integrating the optically uniform WS2-SA in the Yb- and Er-doped laser cavities, we obtain self-starting Q-switched pulses with microsecond duration and kilohertz repetition rates at 1030 and 1558 nm. Our work demonstrates broadband sub-bandgap saturable absorption of a single, solution processed WS2-SA, providing new potential efficacy for WS2 in ultrafast photonic applications.

  14. Mid-infrared self-Q-switched Er, Pr:CaF2 diode-pumped laser.

    PubMed

    Liu, Jingjing; Fan, Xiuwei; Liu, Jie; Ma, Weiwei; Wang, Jingya; Su, Liangbi

    2016-10-15

    A diode-end-pumped self-Q-switched mid-infrared laser was demonstrated with Er3+, Pr3+ co-doped CaF2 crystal for, to the best of our knowledge, the first time. Maximum average output power of 262 mW was achieved and the corresponding slope efficiency was 14.9%. Stable self-Q-switched laser pulses as short as 718 ns were obtained with a repetition rate of 52.63 kHz at the center wavelength of 2803.7 nm. This highly compact nanosecond laser using a 3 at. % Er3+ and 0.03 at. % Pr3+ co-doped CaF2 crystal is free from any active or passive modulators in cavity, potentially promising for a micro and integrated diode-pumped mid-infrared laser system.

  15. Watt-level passively Q-switched heavily Er3+-doped ZBLAN fiber laser with a semiconductor saturable absorber mirror

    PubMed Central

    Shen, Yanlong; Wang, Yishan; Luan, Kunpeng; Huang, Ke; Tao, Mengmeng; Chen, Hongwei; Yi, Aiping; Feng, Guobin; Si, Jinhai

    2016-01-01

    A diode-cladding pumped mid-infrared passively Q-switched Er3+-doped ZBLAN fiber laser with an average output power of watt-level based on a semiconductor saturable absorber mirror (SESAM) is demonstrated. Stable pulse train was produced at a slope efficiency of 17.8% with respect to launched pump power. The maximum average power of 1.01 W at a repetition rate of 146.3 kHz was achieved with a corresponding pulse energy of 6.9 μJ, from which the maximum peak power was calculated to be 21.9 W. To the best of our knowledge, the average power and the peak power are the highest in 3 μm region passively Q-switched fiber lasers. The influence of gain fiber length on the operation regime of the fiber laser has been investigated in detail. PMID:27225029

  16. Scaling output energy in a diode-end-pumped passively Q-switched laser with a flat-flat resonator

    NASA Astrophysics Data System (ADS)

    Tang, C. Y.; Huang, Y. J.; Liang, H. C.; Chen, Y. F.; Su, K. W.

    2017-01-01

    The spatial and temporal behaviors in a diode-end-pumped passively Q-switched laser with a flat-flat resonator are systematically explored as a function of the cavity length. A Nd:YAG/Cr4+:YAG miniature laser is experimentally used to show that the scale-up of the pulse energy without the higher-order transverse modes can be practically realized by optimizing the cavity length as a function of the pump size. A theoretical analysis is performed to confirm the experimental results. The extracavity second harmonic generation is experimentally conducted to demonstrate the usefulness of the laser design. PACS number(s): 42.60.Gd Q-switching; 42.55.Xi Diode-pumped lasers; 42.55.-f Lasers; 42.65.Sf Dynamics of nonlinear optical systems; optical instabilities, optical chaos and complexity, and optical spatiotemporal dynamics.

  17. Laboratory model for the study and treatment of traumatic tattoos with the Q-switched ruby laser

    NASA Astrophysics Data System (ADS)

    Silverman, Richard T.; Lach, Elliot

    1994-09-01

    The outcome of laser tattoo removal is dependent on the type of laser and characteristics of the tattoo. A rabbit model was developed to study the Q-switched ruby laser in the treatment of traumatic tattooing. On the backs of white New Zealand rabbits, three 3 cm patches were dermabraded and dressed with carbon black and antibiotic ointment. After a healing period of eight weeks, pre-treatment biopsies were obtained, and the rabbits were treated with the Q- switched ruby laser at various fluence settings with a pulse width of 34 nsec. At set intervals, further biopsies were obtained and studied with light and electron microscopic analysis, and photodocumentation was performed. Grossly, clearance of the tattooed areas was noted in the laser treated specimens. More effective clearance was observed with higher fluence treatment. No infections occurred, and hair regrowth was noted in all cases, though the rate seemed to be altered by laser treatment.

  18. Theoretical and experimental study on passively Q-switched intracavity frequency-doubled solid-state yellow Raman lasers.

    PubMed

    Ding, Shuanghong; Zhang, Wenhui; Wang, Shiwu; Wang, Xichang; Zhang, Jun; Wang, Meiqin

    2013-05-20

    Normalized space-dependent rate equations of passively Q-switched intracavity frequency-doubled Raman lasers are deduced for the first time. The normalized rate equations are solved numerically to investigate the influences of the normalized variables on the yellow laser performance. The LD end-pumped passively Q-switched Nd:YAG/SrWO(4)/KTP/Cr:YAG yellow Raman laser is realized, and the maximum yellow laser output power is 350 mW with the incident pump power of 5.9 W with Cr:YAG of 85% initial transmission. The theoretical analysis and optimization are taken out for the experiment, and the theoretical results are in accordance with the experimental ones.

  19. Continuous-wave and Q-switched operation of a resonantly pumped Ho:YAlO3 laser.

    PubMed

    Yao, Bao-Quan; Duan, Xiao-Ming; Zheng, Liang-Liang; Ju, You-Lun; Wang, Yue-Zhu; Zhao, Guang-Jun; Dong, Qin

    2008-09-15

    We demonstrated continuous-wave (CW) and Q-switched operation of a room-temperature Ho:YAlO(3) laser that is resonantly end-pumped by a diode-pumped Tm:YLF laser at 1.91 microm. The CW Ho:YAlO(3) laser generated 5.5 W of linearly polarized (EII c ) output at 2118 nm with beam quality factor of M(2) approximately 1.1 for an incident pump power of 13.8 W, corresponding to optical-to-optical conversion efficiency of 40%. Up to 1- mJ energy per pulse at pulse repetition frequency (PRF) of 5 kHz, and the maximum average power of 5.3-W with FWHM pulse duration of 30.5 ns at 20 kHz were achieved in Q-switched mode.

  20. Low-threshold diode-pumped Yb3+,Na+:CaF2 self-Q-switched laser.

    PubMed

    Su, Liangbi; Xu, Jun; Xue, Yinghong; Wang, Chingyue; Chai, Lu; Xu, Xiaodong; Zhao, Guangjun

    2005-07-25

    For the first time to our knowledge, the laser performance of Yb3+, Na+-codoped CaF2 single crystals was demonstrated. Self-Q-switched laser operation at 1050nm was observed for 976 nm diode pumping at room temperature. On 5 W of incident power, the repetition rate and width of the self-Q-switched pulses reached 28 kHz and 1.5 micros, respectively. A maximal slope efficiency of 20.3% and minimal threshold absorbed pump power of 30 mW were respectively achieved with different output couplers, showing the promising application of Yb3+, Na+-codoped CaF2 crystals as compact and efficient solid-state lasers.

  1. High-energy directly diode-pumped Q-switched 1617 nm Er:YAG laser at room temperature.

    PubMed

    Wang, Mingjian; Zhu, Liang; Chen, Weibiao; Fan, Dianyuan

    2012-09-01

    We describe high-energy Erbium-doped yttrium aluminum garnet (Er:YAG) lasers operating at 1617 nm, resonantly pumped using 1532 nm fiber-coupled laser diodes. A maximum continuous wave output power of 4.3 W at 1617 nm was achieved with an output coupler of 20% transmission under incident pump power of 29.7 W, resulting in an optical conversion of 14% with respect to the incident pump power. In Q-switched operation, the pulse energy of 11.8 mJ at 100 Hz pulse repetition frequency and 81 ns pulse duration was obtained. This energy is the highest pulse energy reported for a directly diode-pumped Q-switched Er:YAG laser operating at 1617 nm.

  2. Thermal, spectral properties and Q-switched laser operation of Nd:SrLaAlO4 crystal

    NASA Astrophysics Data System (ADS)

    Liu, Shande; Dong, Lulu; Zhang, Xiao; Yao, Yongping; Xu, Yan; Ren, Tingqi; Zheng, Lihe; Su, Liangbi; Berkowski, Marek

    2017-02-01

    The thermal and spectral properties of a Nd:SrLaAlO4 (Nd:SLA) crystal were systematically studied, including thermal diffusivity, thermal expansion, specific heat, thermal conductivity, polarized absorption and emission spectra. Both continuous-wave (CW) and passively Q-switched Nd:SLA laser operations were investigated. The maximum CW output power of 3.54 W was obtained at 1.077 μm, corresponding to an optical-to-optical efficiency of 46.4%. In the passively Q-switched regime, the maximum average power, pulse repetition rate, and shortest pulse width were 1.8 W, 113 kHz, and 12.6 ns, respectively. All the results indicate that the Nd:SLA crystal is a highly efficient gain medium for laser applications.

  3. Microstructure and mechanical changes induced by Q-Switched pulse laser on human enamel with aim of caries prevention

    NASA Astrophysics Data System (ADS)

    Apsari, R.; Pratomo, D. A.; Hikmawati, D.; Bidin, N.

    2016-03-01

    This study was conducted to determine the effect of Q-Switched Nd: YAG laser energy dose to human enamel caries. The specifications of Q-Switched Nd: YAG laser as followed: wavelength of 1064 nm and 6 ns pulse width. Caries enamel samples taken from human teeth molars of 17-35 ages and the type of media caries. Energy doses used in this study were 723.65 mJ/cm2, 767.72 mJ/cm2, and 1065.515 mJ/cm2; 5 Hz repetition rate, and 20 second exposure time. Samples characterized the surface morphology and the percentage of constituent elements, especially calcium/phosphorus (Ca/P) with FESEM-EDAX. The fraction volume and crystallinity percentage of hydroxyapatite (HA) with XRD and hardness value using Vickers Microhardness Test. The results indicated that exposure of Q-Switched Nd:YAG laser on enamel caries resulting cracks, holes, and melt due to plasma production effects in the surface. Plasma production effect also resulted in micro properties such as percentage of Ca/P was close to normal, the fraction volume and crystallinity percentage of HA went up but did not change the crystal structure (in terms of the lattice structure). The hardness value also rose as linear as exposure energy dose caused by phototermal effect. Based on the results, Q-Switched Nd:YAG laser can be used as contactless drill dental caries replacement candidate with the additional therapy effect such as localized caries in order to avoid the spread, the ratio of Ca/P approaching healthy teeth, the fraction volume and crystallinity percentage of HA rose and established stronger teeth with peak energy dose 1065.515 mJ/cm2.

  4. On the possibility of increasing the pulse energy of a passively Q-switched erbium glass minilaser

    SciTech Connect

    Izyneev, A A; Sadovskii, Pavel I; Sadovskii, S P

    2010-08-03

    A simple method to increase the output energy of a passively Q-switched erbium glass laser is proposed. Using the amplitude modulation of losses at the active element face, the fundamental mode was reliably suppressed and the laser operated in a selected higher-order mode. The output energy was experimentally increased by a factor of 2.1, and the range of allowable pump energy instability was extended threefold. (lasers)

  5. CONTROL OF LASER RADIATION PARAMETERS: Passive laser Q switches made of glass doped with oxidised nanoparticles of copper selenide

    NASA Astrophysics Data System (ADS)

    Yumashev, K. V.

    2000-01-01

    Passive Q switching of Nd3+:YAG (λ = 1060 nm) and YAlO3:Nd3+ (1340 nm) lasers, as well as of an Er3+ (1540 nm) glass laser was realised by using glass doped with oxidised nanoparticles of copper selenide. Nonlinear optical properties of the nanoparticles (radius of 25 nm) in a glass matrix were studied by the picosecond absorption spectroscopy technique.

  6. CW and Q-switched performance of a diode end-pumped Yb:YAG laser. Revision 1

    SciTech Connect

    Bibeau, C.; Beach, R.; Ebbers, C.; Emanuel, M.; Skidmore, J.

    1997-02-19

    Using an end-pumped technology developed at LLNL we have demonstrated a Yb:YAG laser capable of delivering up to 434 W of CW power and 226 W of Q-switched power. In addition, we have frequency doubled the output to 515 nm using a dual crystal scheme to produce 76 W at 10 kHz in a 30 ns pulse length.

  7. Gold nanorods saturable absorber for Q-switched Nd:GAGG lasers at 1 μm

    NASA Astrophysics Data System (ADS)

    Feng, Chao; Liu, Mingyi; Li, Yanbin; Gao, Xuejian; Kang, Zhe; Qin, Guanshi; Jia, Zhitai; Tao, Xutang; Song, Teng; Dun, Yangyang; Bai, Fen; Li, Ping; Wang, Qingpu; Fang, Jiaxiong

    2017-03-01

    A gold nanorod saturable absorber has been synthesized by the seed-mediated growth method characterized in detail. The absorption peak wavelength was 1080 nm, and the modulation depth was measured to be 9%. The performance of its Q-switched Nd:GAGG lasers at 1061 and 1106 nm has been systematically investigated, respectively. The corresponding shortest pulsewidths were 250 and 480 ns. Our experiment results proved that the GNR-SA is a promising saturable absorber for nanosecond bulk lasers.

  8. Diode-pumped passively Q-switched Nd:GGG laser with a Bi-doped GaAs semiconductor saturable absorber

    NASA Astrophysics Data System (ADS)

    Cong, Wen; Li, Dechun; Zhao, Shengzhi; Yang, Kejian; Li, Xiangyang; Qiao, Hui; Liu, Ji

    2014-12-01

    Passive Q-switching of a diode-pumped Nd:GGG laser is demonstrated using Bi-doped GaAs as saturable absorber. The Bi-doped GaAs wafer is fabricated by ion implantation and subsequent annealing. Compared with the Q-switched laser by undoped GaAs semiconductor saturable absorber, the laser with Bi-doped GaAs as saturable absorber can produce higher output power, shorter pulses, higher single pulse energies and higher peak powers. These results suggest that Bi-doped GaAs can be a promising new candidate of semiconductor saturable absorber in Q-switched laser.

  9. CONTROL OF LASER RADIATION PARAMETERS: Pulse synchronisation in passively Q-switched lasers emitting at 1.053 and 1.064 μm

    NASA Astrophysics Data System (ADS)

    Bagdasarov, V. Kh; Denisov, N. N.; Malyutin, A. A.; Chigaev, I. A.

    2009-10-01

    Pulse synchronisation with an accuracy of no worse than ±5 ns is demonstrated in passively Q-switched neodymium phosphate glass and Nd:YAG lasers. Two operating regimes are realised: the 'sub-threshold' regime (when the slave Nd:YAG laser does not generate a giant pulse if its passive Q switch is not irradiated by the master Nd:glass laser) and the 'above-threshold' regime (when the pulse irradiating the passive Q switch of the slave laser advances its generation).

  10. Active Q-switching of a fiber laser using a modulated fiber Fabry-Perot filter and a fiber Bragg grating

    NASA Astrophysics Data System (ADS)

    Martínez Manuel, Rodolfo; Kaboko, J. J. M.; Shlyagin, M. G.

    2016-02-01

    We propose and demonstrate a simple and robust actively Q-switched erbium-doped fiber ring cavity laser. The Q-switching is based on dynamic spectral overlapping of two filters, namely a fiber Bragg grating-based filter and a fiber Fabry-Perot tunable filter. Using 3.5 m of erbium-doped fiber and a pump power of only 60 mW, Q-switched pulses with a peak power of 9.7 W and a pulse duration of 500 ns were obtained. A pulse repetition rate can be continuously varied from a single shot to a few KHz.

  11. High-power Q-switched erbium-ytterbium codoped fiber laser using multiwalled carbon nanotubes saturable absorber

    NASA Astrophysics Data System (ADS)

    Ab Razak, Mohd Zulhakimi; Saleh, Zatul Saliza; Ahmad, Fauzan; Anyi, Carol Livan; Harun, Sulaiman W.; Arof, Hamzah

    2016-10-01

    Due to an enormous potential of pulsed lasers in applications such as manufacturing, metrology, environmental sensing, and biomedical diagnostics, a high-power and stable Q-switched erbium-ytterbium codoped double-clad fiber laser (EYDFL) incorporating of multiwall carbon nanotubes (MWCNTs) saturable absorber (SA) made based on polyvinyl alcohol (PVA) with a 3∶2 ratio is demonstrated. The SA was fabricated by mixing a dilute PVA solution with an MWCNTs homogeneous solution. Subsequently, the mixture was sonicated and centrifuged to produce a homogeneous suspension that was left to dry at room temperature to form the MWCNTs-PVA film. The SA was formed by inserting the film between a pair of FC/PC fiber connectors. Then, it was integrated into the EYDFL's ring cavity, which uses a 5-m-long erbium-ytterbium codoped fiber (EYDF). The lasing threshold for the Q-switched EYDFL was at 330 mW. At the maximum available pump power of 900 mW, the proposed EYDFL produced Q-switched pulses with a repetition rate of 74.85 kHz, pulsewidth of ˜3.6 μs, and an average output power of about 5 mW. The maximum energy per pulse of ˜85 nJ was obtained at pump power of ˜700 mW with peak power of 21 mW.

  12. Numerical solution and experiment of a self-Q-switched 946 nm Cr,Nd:YAG laser

    NASA Astrophysics Data System (ADS)

    Li, Q.; Feng, B.; Zhang, D.; Du, S.; Shi, Y.; Zhang, Z.; Zhang, S.

    2008-11-01

    A LD-pumped self-Q-switched 946 nm laser by using a co-doped Cr,Nd:YAG crystal as a gain medium as well as a saturable absorber is studied. The 946 nm self-Q-switched rate equations of co-doped crystal are solved numerically by Runge-Kutta method directly. The important parameters of lasers, such as average output power, threshold pump power, pulse width, pulses repetition rate, and optimal transmission of output coupler are obtained numerically. Experimentally, the maximum average output power up to 2.61 W, corresponding to a slope efficiency of 23.43%, was obtained in a simple and compact linear cavity. The optical-to-optical efficiency is 17.3% and the peak power is 7.57 kW with repetition rate of 23.78 kHz and pulse width of 14.5 ns. In the experiments, a high-quality fundamental transverse mode can be preserved in a large range of incident pump power. The numerical results of the 946 nm self-Q-switched Cr,Nd:YAG laser are in good agreement with the experimental results.

  13. Passively Q-switched ytterbium-doped ScBO3 laser with black phosphorus saturable absorber

    NASA Astrophysics Data System (ADS)

    Lu, Dazhi; Pan, Zhongben; Zhang, Rui; Xu, Tianxiang; Yang, Ruilong; Yang, Bingchao; Liu, Zhongyuan; Yu, Haohai; Zhang, Huaijin; Wang, Jiyang

    2016-08-01

    We demonstrate a passively Q-switched Yb3+-doped ScBO3 bulk laser using a black phosphorous (BP) saturable absorber, a two-dimensional semiconductor. The response spectra of BP show that it is suitable as a universal switcher in the spectral range from the visible to midinfrared band. Considering the saturable absorption properties of BP and emission properties of Yb3+-doped crystals, the passively Q-switched bulk laser pulses were realized with the Yb3+:ScBO3 crystal as a gain material and a fabricated BP sample as a Q-switcher. Because of the large energy storage capacity of Yb3+:ScBO3, the maximum output energy is obtained to be 1.4 μJ, which is comparable with the previous reported maximum energy of graphene Q-switched lasers. The obtained results identify the potential capability of BP as a pulse modulator in bulk lasers, and BP plays an increasingly important role in a wide range of its applications, including photonics and optoelectronics.

  14. Semiconductor saturable absorber mirror passively Q-switched 2.97 μm fluoride fiber laser

    NASA Astrophysics Data System (ADS)

    Li, Jianfeng; Luo, Hongyu; He, Yulian; Liu, Yong; Luo, Binbin; Sun, Zhongyuan; Zhang, Lin; Turitsyn, Sergei K.

    2014-05-01

    A diode-cladding-pumped mid-infrared passively Q-switched Ho3+-doped fluoride fiber laser using a reverse designed broad band semiconductor saturable mirror (SESAM) was demonstrated. Nonlinear reflectivity of the SESAM was measured using an in-house Yb3+-doped mode-locked fiber laser at 1062 nm. Stable pulse train was produced at a slope efficient of 12.1% with respect to the launched pump power. Maximum pulse energy of 6.65 μJ with a pulse width of 1.68 μs and signal to noise ratio (SNR) of ~50 dB was achieved at a repetition rate of 47.6 kHz and center wavelength of 2.971 μm. To the best of our knowledge, this is the first 3 μm region SESAM based Q-switched fiber laser with the highest average power and pulse energy, as well as the longest wavelength from mid-infrared passively Q-switched fluoride fiber lasers.

  15. Semiconductor saturable absorber mirror passively Q-switched 2.97 μm fluoride fiber laser

    NASA Astrophysics Data System (ADS)

    Li, J. F.; Luo, H. Y.; He, Y. L.; Liu, Y.; Zhang, L.; Zhou, K. M.; Rozhin, A. G.; Turistyn, S. K.

    2014-06-01

    A diode-cladding-pumped mid-infrared passively Q-switched Ho3+-doped fluoride fiber laser using a reverse designed broad band semiconductor saturable mirror (SESAM) was demonstrated. Nonlinear reflectivity of the SESAM was measured using an in-house Yb3+-doped mode-locked fiber laser at 1062 nm. Stable pulse train was produced at a slope efficient of 12.1% with respect to the launched pump power. Maximum pulse energy of 6.65 µJ with a pulse width of 1.68 µs and signal-to-noise ratio (SNR) of ~50 dB was achieved at a repetition rate of 47.6 kHz and center wavelength of 2.971 µm. To the best of our knowledge, this is the first 3 µm region SESAM-based Q-switched fiber laser with the highest average power and pulse energy, as well as the longest wavelength from mid-infrared passively Q-switched fluoride fiber lasers.

  16. Switchable Q-switched and modelocked operation in ytterbium doped fiber laser under all-normal-dispersion configuration

    SciTech Connect

    Mukhopadhyay, Pranb K. Gupta, Pradeep K.; Singh, Chandra Pal; Singh, Amarjeet; Sharma, Sunil K.; Bindra, Kushvinder S.; Oak, Shrikant M.

    2015-03-15

    We have constructed an Yb-doped fiber laser in all-normal-dispersion configuration which can be independently operated in Q-switched or modelocked configuration with the help of a simple fiber optic ring resonator (FORR). In the presence of FORR, the laser operates in Q-switched mode producing stable pulses in the range of 1 μs-200 ns with repetition rate in the range of 45 kHz-82 kHz. On the other hand, the laser can be easily switched to mode-locked operation by disjoining the FORR loop producing train of ultrashort pulses of ∼5 ps duration (compressible to ∼150 fs) at ∼38 MHz repetition rate. The transmission characteristics of FORR in combination with the nonlinear polarization rotation for passive Q-switching operation is numerically investigated and experimentally verified. The laser can serve as a versatile seed source for power amplifier which can be easily configured for application in the fields that require different pulsed fiber lasers.

  17. Switchable Q-switched and modelocked operation in ytterbium doped fiber laser under all-normal-dispersion configuration.

    PubMed

    Mukhopadhyay, Pranb K; Gupta, Pradeep K; Singh, Chandra Pal; Singh, Amarjeet; Sharma, Sunil K; Bindra, Kushvinder S; Oak, Shrikant M

    2015-03-01

    We have constructed an Yb-doped fiber laser in all-normal-dispersion configuration which can be independently operated in Q-switched or modelocked configuration with the help of a simple fiber optic ring resonator (FORR). In the presence of FORR, the laser operates in Q-switched mode producing stable pulses in the range of 1 μs-200 ns with repetition rate in the range of 45 kHz-82 kHz. On the other hand, the laser can be easily switched to mode-locked operation by disjoining the FORR loop producing train of ultrashort pulses of ∼5 ps duration (compressible to ∼150 fs) at ∼38 MHz repetition rate. The transmission characteristics of FORR in combination with the nonlinear polarization rotation for passive Q-switching operation is numerically investigated and experimentally verified. The laser can serve as a versatile seed source for power amplifier which can be easily configured for application in the fields that require different pulsed fiber lasers.

  18. In vitro assessment of fiber sweeping speed during Q-switched 532-nm laser tissue ablation

    NASA Astrophysics Data System (ADS)

    Rajabhandharaks, Danop; Kang, Hyun Wook; Ko, Woo Jin; Stinson, Douglas; Choi, Benjamin

    2011-03-01

    Photoselective vaporization of the prostate (PVP) is considered a minimally invasive procedure to treat benign prostatic hyperplasia (BPH). During the PVP, the prostate gland is irradiated by the 532-nm laser and the fiber is swept and dragged along the urethra. In this study the speed of sweeping fiber during the PVP is being investigated. In vitro porcine kidney model was used (N=100) throughout the experiment. A Q-switched 532-nm laser, equipped with sidefiring 750-Um fiber, was employed and set to power levels of 120 and 180 W. The speed of fiber sweeping was the only variable in this study and varied at 0 (i.e. no sweeping), 0.5, 1.0, 1.5, and 2.0 sweep/s. Ablation rate, depth, and coagulation thickness were quantified. Based on the current settings, ablation rate decreased as sweeping speed increased and was maximized between 0 to 1.0 sweep/s for 120-W power level and between 0 to 0.5 sweep/s for 180-W power level. Ablation rate at 180 W was higher than that at 120 W, regardless of sweeping speed. Ablation depth at both 120 and 180 W was maximized at 0 sweep/s and decreased 35% at 0.5 sweep/s. The overall coagulation thickness was less than 1.5 mm and comparable from 0 to 1.5 sweep/s (0.8~0.9 mm) and increased at 2.0 sweep/s (~1.1 mm). This study demonstrated that tissue ablation performance was contingent upon sweeping speed and maximized at slow sweeping speed due to longer laser-tissue interaction time and larger area coverage by the 532-nm light.

  19. Temperature-stable lithium niobate electro-optic Q-switch for improved cold performance

    NASA Astrophysics Data System (ADS)

    Jundt, Dieter H.

    2014-10-01

    Lithium niobate (LN) is commonly used as an electro optic (EO) Q-switch material in infrared targeting lasers because of its relatively low voltage requirements and low cost compared to other crystals. A common challenge is maintaining good performance at the sub-freezing temperatures often experienced during flight. Dropping to low temperature causes a pyro-electric charge buildup on the optical faces that leads to birefringence non-uniformity and depolarization resulting in poor hold-off and premature lasing. The most common solution has been to use radioactive americium to ionize the air around the crystal and bleed off the charge, but the radioactive material requires handling and disposal procedures that can be problematic. We have developed a superior solution that is now being implemented by multiple defense system suppliers. By applying a low level thermo-chemical reduction to the LN crystal optical faces we induce a small conductivity that allows pyro-charges to dissipate. As the material gets more heavily treated, the capacity to dissipate charges improves, but the corresponding optical absorption also increases, causing insertion loss. Even though typical high gain targeting laser systems can tolerate a few percent of added loss, the thermo-chemical processing needs to be carefully optimized. We describe the results of our process optimization to minimize the insertion loss while still giving effective charge dissipation. Treatment is performed at temperatures below 500°C and a conductivity layer less than 0.5mm in depth is created that is uniform across the optical aperture. Because the conductivity is thermally activated, the charge dissipation is less effective at low temperature, and characterization needs to be performed at cold temperatures. The trade-off between optical insertion loss and potential depolarization due to low temperature operation is discussed and experimental results on the temperature dependence of the dissipation time and the

  20. Generation of stable and narrow spacing dual-wavelength ytterbium-doped fiber laser using a photonic crystal fiber

    NASA Astrophysics Data System (ADS)

    Ahmad, Harith; Aizi Mat Salim, Muhammad; Soltanian, Mohammad Reza K.; Razalli Azzuhri, Saaidal; Wadi Harun, Sulaiman; Yasin, Moh.

    2016-05-01

    We demonstrate the design and operation of novel narrow spacing and stable dual-wavelength fiber laser (DWFL). A 70-cm ytterbium-doped fiber has been chosen as the gain medium in a ring cavity arrangement. Our design includes a short length photonic crystal fiber, acting as a dual-wavelength stabilizer based on its birefringence coefficient and nonlinear behavior and tunable band pass filter (TBPF) to achieve narrow spacing spectrum lasing. Our laser output is considered to be highly stable, with power fluctuation less than 0.8 dB over a period of 15 min. The flexibility and tunability of TBPF, together with polarization controller enable the spacing tuning of the DWFL from 0.03 nm up to 0.07 nm for 1040 nm region, and 0.10 nm up to 0.40 nm for 1060 nm region. The tunable wavelength spacing shows the flexibility of the DWFL in addition to stable and reliable properties of fiber laser in 1-μm region.

  1. High power, widely tunable dual-wavelength 2 μm laser based on intracavity KTP optical parametric oscillator

    NASA Astrophysics Data System (ADS)

    Yan, Dexian; Wang, Yuye; Xu, Degang; Shi, Wei; Zhong, Kai; Liu, Pengxiang; Yan, Chao; Mei, Jialin; Shi, Jia; Yao, Jianquan

    2017-01-01

    We presented a high power, widely tunable narrowband 2 μm dual-wavelength source employing intracavity optical parametric oscillator with potassium titanium oxide phosphate (KTP) crystal. Two identical KTP crystals were oriented oppositely in the OPO cavity to compensate the walk-off effect. The output average power of dual-wavelength 2 μm laser was up to 18.18 W at 10 kHz with the peak power of 165 kW. The two wavelengths can be tuned in the range of 2070.7 nm to 2191.1 nm for ordinary light while in the range of 2190.7 nm to 2065.9 nm for extraordinary light with the full width at half maximum (FWHM) about 0.8 nm. The pulse width of the tunable laser was as narrow as 11 ns. The beam quality factor M 2 was less than 4 during wavelength tuning.

  2. Single-polarization, switchable dual-wavelength erbium-doped fiber laser with two polarization-maintaining fiber Bragg gratings.

    PubMed

    Feng, Suchun; Xu, Ou; Lu, Shaohua; Mao, Xiangqiao; Ning, Tigang; Jian, Shuisheng

    2008-08-04

    An improved erbium-doped fiber laser configuration for achieving single-polarization, switchable dual-wavelength of orthogonal polarizations oscillations at room temperature is proposed. For the first time, two fiber Bragg gratings (FBGs) directly written in a polarization-maintaining (PM) and photosensitive erbium-doped fiber (PMPEDF) as the wavelength-selective component are used in a linear laser cavity. Due to the polarization hole burning (PHB) enhanced by the polarization-maintaining FBG (PMFBG), the laser can be designed to operate in stable dual-wavelength or wavelength-switching modes with a wavelength spacing of 0.336 nm at room temperature by adjusting a polarization controller (PC). Each lasing line shows a single polarization with a polarization extinction ratio of >25 dB under different pump levels. The optical signal-to-noise ratio (OSNR) is greater than 50 dB. The amplitude variation with 16 times scans in nearly one and half an hour is less than 0.5 dB at both operating wavelength.

  3. Difference frequency generation of Mid-IR radiation in PPLN crystals using a dual-wavelength all-fiber amplifier

    NASA Astrophysics Data System (ADS)

    Krzempek, Karol; Soboń, Grzegorz; Dudzik, Grzegorz; Sotor, Jaroslaw; Abramski, Krzysztof M.

    2014-02-01

    We present a method of generating mid-IR radiation by means of nonlinear difference frequency generation (DFG) effects occurring in periodically polled lithium niobate (PPLN) crystals using an all-fiber dual-wavelength amplifier. The presented mid-IR laser source incorporates an unique double-clad (DC) Erbium and Ytterbium (Er-Yb) doped amplifier stage capable of simultaneous amplification of both wavelengths required in the DFG process - 1064 nm and 1550 nm. The amplifier delivered more than 23.7 dB and 14.4 dB of amplification for 1550 nm and 1064 nm wavelength, low power, off-the-shelf, fiber pigtailed, distributed feedback (DFB) laser diodes, respectively. The dual-wavelength amplifier parameters crucial for the DFG process were investigated, including long-term power and polarization instabilities and optical spectrum characteristics of both amplified wavelengths. The DFG setup used a single collimator radiation delivery scheme and an 40 mm long MgO doped PPLN crystal. In effect the DFG source was capable of generating 1.14 mW of radiation centered around 3.4 μm. The overall performance of the mid-IR source was elaborated by performing sensitive Tunable Diode Laser Absorption Spectroscopy (TDLAS) detection of methane (CH4) in ambient air on an free-space optical path-length of 8 m. The measured detection limit of the sensor was 26 ppbv with a 1σ SNR of 69.

  4. Broadly tunable dual-wavelength light source for coherent anti-Stokes Raman scattering microscopy.

    PubMed

    Ganikhanov, Feruz; Carrasco, Silvia; Sunney Xie, X; Katz, Mordechai; Seitz, Wolfgang; Kopf, Daniel

    2006-05-01

    The signal and idler beams from a picosecond, synchronously pumped optical parametric oscillator (OPO) provide the two colors necessary for coherent anti-Stokes Raman scattering (CARS) microscopy. The OPO provides a continuously tunable frequency difference between the two beams over a broad range of Raman shifts (100-3700 cm(-1)) by varying the temperature of a single nonlinear crystal. The near-infrared output (900-1300 nm) allows for deep penetration into thick samples and reduced nonlinear photodamage. Applications of this light source to in vivo cell and ex vivo tissue imaging are demonstrated.

  5. Transversely diode-pumped Q-switched Nd : YAG laser with injection of radiation from a single-frequency semiconductor laser

    NASA Astrophysics Data System (ADS)

    Bogdanovich, M. V.; Duraev, V. P.; Kalinov, V. S.; Kostik, O. E.; Lantsov, K. I.; Lepchenkov, K. V.; Mashko, V. V.; Ryabtsev, A. G.; Ryabtsev, G. I.; Teplyashin, L. L.

    2016-10-01

    A Q-switched Nd : YAG laser with a high-power transverse diode pumping and injection of seed radiation generated by a single-frequency semiconductor laser is described. The threshold seed radiation power at which the Q-switched Nd : YAG switches to the single-frequency mode is 0.44 {\\text{mW}} (radiation intensity 5.6 × 10-2 {\\text{W}} {\\text{cm}}-2). With increasing injection power, the spectral and power characteristics of the Q-switched laser almost do not change at a constant excitation of its active medium. The spectral linewidth of the Q-switched Nd : YAG laser with injection from a TLD-1060-14BF single-frequency semiconductor laser module does not exceed 90 {\\text{MHz}} (wavelength 1064 {\\text{nm}}).

  6. A Cr4+:YAG passively Q-switched Nd:YVO4 microchip laser for controllable high-order Hermite-Gaussian modes

    NASA Astrophysics Data System (ADS)

    Dong, Jun; He, Yu; Bai, Sheng-Chuang; Ueda, Ken-ichi; Kaminskii, Alexander A.

    2016-09-01

    A nanosecond, high peak power, passively Q-switched laser for controllable Hermite-Gaussian (HG) modes has been achieved by manipulating the saturated inversion population inside the gain medium. The stable HG modes are generated in a Cr4+:YAG passively Q-switched Nd:YVO4 microchip laser by applying a tilted pump beam. The asymmetrical saturated inversion population distribution inside the Nd:YVO4 crystal for desirable HG modes is manipulated by choosing the proper pump beam diameter and varying pump power. A HG9,8 mode passively Q-switched Nd:YVO4 microchip laser with average output power of 265 mW has been obtained. Laser pulses with a pulse width of 7.3 ns and peak power of over 1.7 kW working at 21 kHz have been generated in the passively Q-switched Nd:YVO4 microchip laser.

  7. Output characteristics of diode-end-pumped electro-optically Q-switched Nd:LuVO4 laser at 1064 nm

    NASA Astrophysics Data System (ADS)

    Zhao, Weifang; Zhang, Ling; Yu, Haijuan; Qi, Yaoyao; He, Chaojian; Zhang, Jingyuan; Lin, Xuechun

    2016-06-01

    We demonstrated a Q-switched Nd:LuVO4 laser with fundamental mode at 1064 nm using BaB2O4 electro-optic Q-switching. High-efficiency operation of Q-switched laser with dynamic to static ratio of 91.4% was realized. When the absorbed pump power was 6.59 W, the maximum average output power of 2.88 W was achieved with a repetition rate of 50 kHz. The optical conversion efficiency and slope efficiency were 43.7% and 55.5%, respectively. The minimum pulse width of 17.8 ns was achieved. Meanwhile, the pulse energy and peak power were 57.6 μJ and 3.2 kW, respectively. To the best of our knowledge, this study is the first to demonstrate about the electro-optically Q-switched laser in Nd:LuVO4 crystal.

  8. Q-switched fiber laser based on transition metal dichalcogenides MoS(2), MoSe(2), WS(2), and WSe(2).

    PubMed

    Chen, Bohua; Zhang, Xiaoyan; Wu, Kan; Wang, Hao; Wang, Jun; Chen, Jianping

    2015-10-05

    In this paper, we report 4 different saturable absorbers based on 4 transition metal dichalcogenides (MoS(2), MoSe(2), WS(2), WSe(2)) and utilize them to Q-switch a ring-cavity fiber laser with identical cavity configuration. It is found that MoSe(2) exhibits highest modulation depth with similar preparation process among four saturable absorbers. Q-switching operation performance is compared from the aspects of RF spectrum, optical spectrum, repetition rate and pulse duration. WS(2) Q-switched fiber laser generates the most stable pulse trains compared to other 3 fiber lasers. These results demonstrate the feasibility of TMDs to Q-switch fiber laser effectively and provide a meaningful reference for further research in nonlinear fiber optics with these TMDs materials.

  9. Passively Q-switched Er3+-doped fiber lasers using colloidal PbS quantum dot saturable absorber.

    PubMed

    Lee, Yin-Wen; Chen, Chien-Ming; Huang, Chia-Wei; Chen, Shih-Ken; Jiang, Jhang-Rong

    2016-05-16

    We report on the demonstration of a passively Q-switched 1.55 µm fiber laser utilizing a colloidal PbS quantum dot (QD) thin film as a saturable absorber. Colloidal PbS QD films have several features that are advantageous in passively Q-switched fiber laser operation, including a large operation wavelength range, cost-effectiveness, and a low saturable absorption intensity. We conducted thorough material and optical studies to verify the advantages of PbS QDs in Q-switched laser operation and successfully generated 801 nJ pulses with a 24.2 kHz repetition rate. To the best of our knowledge, the developed Q-switched fiber laser is the first based on colloidal PbS QDs.

  10. Passively Q-switched Er,Yb:GdAl3(BO3)4 laser with single-walled carbon nanotube based saturable absorber

    NASA Astrophysics Data System (ADS)

    Gorbachenya, K. N.; Kisel, V. E.; Yasukevich, A. S.; Prudnikova, M. B.; Maltsev, V. V.; Leonyuk, N. I.; Choi, S. Y.; Rotermund, F.; Kuleshov, N. V.

    2017-03-01

    We demonstrate a passively Q-switched Er,Yb:GdAl3(BO3)4 diode-pumped laser emitting near 1.5 µm. By using a single-walled carbon nanotube (SWCNT) as a saturable absorber, Q-switched laser pulses with energy of 0.8 µJ and duration of 130 ns at a maximum repetition rate of 500 kHz were obtained at 1550 nm.

  11. A novel miniaturized passively Q-switched pulse-burst laser for engine ignition.

    PubMed

    Ma, Yufei; Li, Xudong; Yu, Xin; Fan, Rongwei; Yan, Renpeng; Peng, Jiangbo; Xu, Xinrui; Sun, Rui; Chen, Deying

    2014-10-06

    A novel miniaturized Cr⁴⁺:YAG passively Q-switched Nd:YAG pulse-burst laser under 808 nm diode-laser pulse-pumping was demonstrated for the purpose of laser-induced plasma ignition, in which pulse-burst mode can realize both high repetition rate and high pulse energy simultaneously in a short period. Side-pumping configuration and two different types of laser cavities were employed. The pumping pulse width was constant at 250 μs. For the plane-plane cavity, the output beam profile was flat-top Gaussian and the measured M² value was 4.1 at the maximum incident pump energy of 600 mJ. The pulse-burst laser contained a maximum of 8 pulses, 7 pulses and 6 pulses for pulse-burst repetition rate of 10 Hz, 50 Hz and 100 Hz, respectively. The energy obtained was 15.5 mJ, 14.9 mJ and 13.9 mJ per pulse for pulse-burst repetition rate of 10 Hz, 50 Hz and 100 Hz, respectively. The maximum repetition rate of laser pulses in pulse-burst was 34.6 kHz for 8 pulses at the incident pump energy of 600 mJ and the single pulse width was 13.3 ns. The thermal lensing effect of Nd:YAG rod was investigated, and an plane-convex cavity was adopted to compensate the thermal lensing effect of Nd:YAG rod and improve the mode matching. For the plane-convex cavity, the output beam profile was quasi-Gaussian and the measured M2 value was 2.2 at the incident pump energy of 600 mJ. The output energy was 10.6 mJ per pulse for pulse-burst repetition rate of 100 Hz. The maximum repetition rate of laser pulses in pulse-burst was 27.4 kHz for 6 pulses at the incident pump energy of 600 mJ and the single pulse width was 14.2 ns. The experimental results showed that this pulse-burst laser can produce high repetition rate (>20 kHz) and high pulse energy (>10 mJ) simultaneously in a short period for both two different cavities.

  12. Selectable dual-wavelength erbium-doped fiber laser with stable single-longitudinal-mode utilizing eye-type compound-ring configuration

    NASA Astrophysics Data System (ADS)

    Yeh, Chien-Hung; Chen, Jhih-Yu; Chen, Hone-Zhang; Chow, Chi-Wai

    2016-08-01

    In this paper, a tunable dual-wavelength erbium-doped fiber (EDF) ring laser with stable single-longitudinal-mode (SLM) under a tuning range of 1530.0-1560.0 nm is proposed and demonstrated. Here, the mode spacing of lasing dual-wavelength from 1.0 to 30.0 nm can be selected arbitrarily in any wavelength position. To accomplish the SLM output, the eye-type compound-ring scheme is proposed inside ring cavity for suppressing the multi-longitudinal-mode (MLM) highly. The entire measured output power and optical signal to noise ratio (OSNR) of each dual-wavelength are larger than -13.3 dBm and 60 dB respectively. In addition, the output stability measurement of proposed EDF laser is also performed and analyzed.

  13. Switchable and spacing-tunable dual-wavelength thulium-doped silica fiber laser based on a nonlinear amplifier loop mirror.

    PubMed

    Liu, Shuo; Yan, Fengping; Feng, Ting; Wu, Beilei; Dong, Ze; Chang, Gee-Kung

    2014-08-20

    A kind of switchable and spacing-tunable dual-wavelength thulium-doped silica fiber laser based on a nonlinear amplifier loop mirror is presented and experimentally demonstrated. By adjusting the polarization controllers (PCs), stable dual-wavelength operation is obtained at the 2 μm band. The optical signal-to-noise ratio (OSNR) is better than 56 dB. The wavelength tuning is performed by applying static strain into the fiber Bragg grating. A tuning range from 0 to 5.14 nm is achieved for the dual-wavelength spacing. By adjusting the PCs properly, the fiber laser can also operate in single-wavelength state with the OSNR for each wavelength more than 50 dB.

  14. Every Good Virtue You Ever Wanted in a Q-switched Solid-state Laser and More: Monolithic, Diode-pumped, Self-q-switched, Highly Reproducible, Diffraction-limited Nd:yag Laser

    NASA Technical Reports Server (NTRS)

    Chen, Y. C.; Lee, K. K.

    1993-01-01

    The applications of Q-switched lasers are well known, for example, laser radar, laser remote sensing, satellite orbit determination, Moon orbit and 'moon quake' determination, satellite laser communication, and many nonlinear optics applications. Most of the applications require additional properties of the Q-switched lasers, such as single-axial and/or single-transverse mode, high repetition rate, stable pulse shape and pulse width, or ultra compact and rugged oscillators. Furthermore, space based and airborne lasers for lidar and laser communication applications require efficient, compact, lightweight, long-lived, and stable-pulsed laser sources. Diode-pumped solid-state lasers (DPSSL) have recently shown the potential for satisfying all of these requirements. We will report on the operating characteristics of a diode-pumped, monolithic, self-Q-switched Cr,Nd:YAG laser where the chromium ions act as a saturable absorber for the laser emission at 1064 nm. The pulse duration is 3.5 ns and the output is highly polarized with an extinction ratio of 700:1. It is further shown that the output is single-longitudinal-mode with transform-limited spectral line width without pulse-to-pulse mode competition. Consequently, the pulse-to-pulse intensity fluctuation is less than the instrument resolution of 0.25 percent. This self-stabilization mechanism is because the lasing mode bleaches the distributed absorber and establishes a gain-loss grating similar to that used in the distributed feedback semiconductor lasers. A repetition rate above 5 KHz has also been demonstrated. For higher power, this laser can be used for injection seeding an amplifier (or amplifier chain) or injection locking of a power oscillator pumped by diode lasers. We will discuss some research directions on the master oscillator for higher output energy per pulse as well as how to scale the output power of the diode-pumped amplifier(s) to multi-kilowatt average power.

  15. Comparison of clinical efficacy and complications between Q-switched alexandrite laser and Q-switched Nd:YAG laser on nevus of Ota: a systematic review and meta-analysis.

    PubMed

    Yu, Panxi; Yu, Nanze; Diao, Wenqi; Yang, Xiaonan; Feng, Yongqiang; Qi, Zuoliang

    2016-04-01

    Although the application of Q-switched lasers on nevus of Ota (OTA) is well demonstrated, debates about clinical option between Q-switched alexandrite laser (QSA) and Q-switched Nd:YAG laser (QSNY) still remain. This systematic review and meta-analysis estimated the overall successful rate of OTA pigment clearance and complication rate of QSA and QSNY and evaluated which laser could produce a better result. English articles evaluating pigment clearance and complications of QSA and/or QSNY on OTA were screened through predetermined inclusion and exclusion criteria and analyzed. The successful rate of pigment clearance and complication rate of QSA and QSNY were respectively calculated using a random-effects or fixed-effects model, depending on the heterogeneity of the included studies. The successful rate and complication rate of QSA and QSNY were compared statistically. Of the 140 articles searched, 13 met inclusion criteria. Totally, 2153 OTA patients treated by QSA and 316 patients treated by QSNY were analyzed. In QSA and QSNY groups, respectively, the successful rate of OTA pigment clearance was 48.3% (95% confidence interval (CI) 19.9-76.8%) and 41% (95% CI 9.7-72.2%), while the complication rate was 8.0% (95% CI 3.9-12.2%) and 13.4% (95% CI 7.7-19.0%). When compared with QSNY, QSA had a significantly higher successful rate (P = 0.017), and a lower complication rate (P = 0.000). According to this review, QSA may surpass QSNY in treatment for OTA as it had a superior successful rate of pigment clearance and a lower complication rate than QSNY did.

  16. Characterization of Topography and Vegetation Structure using Dual-wavelength LIDAR and High-Resolution Stereo Imagery

    NASA Astrophysics Data System (ADS)

    Leigh, H. W.; Magruder, L. A.; Neuenschwander, A. L.

    2015-12-01

    This study examines the utility of co-collected, dual-wavelength, full-waveform LIDAR and high resolution stereo imagery to improve characterizations of topography and vegetation over two survey sites near Monterey, CA. Extraction of waveform features, such as total waveform energy, canopy energy distribution, and foliage penetration metrics are computed along the laser line-of-sight and along the vertical axis of synthesized "pseudowaveforms." The pseudowaveform technique is a novel method that allows for direct comparisons between green (532nm) and near IR (1064nm) waveforms, despite variations in sampling. Comparisons between wavelengths allows for detailed characterization of vegetation structure and distribution not possible with single-wavelength LIDAR. Additionally, point clouds derived from stereo imagery are fused with LIDAR point clouds to increase resolution and improve accuracy of bare earth digital elevation models, further augmenting characterization of tree height and structure.

  17. Coaxial Dual-wavelength Interferometric Method for a Thermal Infrared Focal-plane-array with Integrated Gratings

    NASA Astrophysics Data System (ADS)

    Shang, Yuanfang; Ye, Xiongying; Cao, Liangcai; Song, Pengfei; Feng, Jinyang

    2016-05-01

    Uncooled infrared (IR) focal-plane-array (FPA) with both large sensing range and high sensitivity is a great challenge due to the limited dynamic range of the detected signals. A coaxial dual-wavelength interferometric system was proposed here to detect thermal-induced displacements of an ultrasensitive FPA based on polyvinyl-chloride(PVC)/gold bimorph cantilevers and carbon nanotube (CNT)-based IR absorbing films. By alternately selecting the two displacement measurements performed by λ1 (=640 nm) and λ2 (=660 nm), the temperature measuring range with greater than 50% maximum sensitivity can be extended by eight-fold in comparison with the traditional single-wavelength mode. Meanwhile, the relative measurement error over the full measuring range is below 0.4%. In addition, it offers a feasible approach for on-line and on-wafer FPA characterization with great convenience and high efficiency.

  18. Four-step phase-shifting digital holography simultaneously sensing dual-wavelength information using a monochromatic image sensor

    NASA Astrophysics Data System (ADS)

    Tahara, Tatsuki; Mori, Ryota; Arai, Yasuhiko; Takaki, Yasuhiro

    2015-12-01

    Four-step phase-shifting digital holography simultaneously sensing dual-wavelength information from wavelength-multiplexed holograms is presented. Specific phase shifts for respective wavelengths are introduced to remove the crosstalk components and extract only the object wave at the desired wavelength from the holograms. Object waves at multiple wavelengths are selectively extracted by utilizing 2π ambiguity and the subtraction procedures based on phase-shifting interferometry. Two-step phase-shifting interferometry is merged into the procedures to decrease the number of the recorded holograms. The proposed technique is numerically investigated and experimentally demonstrated. The applicability to the case where the number of wavelengths is more than two and possible noise when using two-step phase-shifting interferometry are discussed.

  19. Detection of acid moisture in photovoltaic modules using a dual wavelength pH-sensitive fluorescent dye

    NASA Astrophysics Data System (ADS)

    Asaka, Takashi; Iwami, Kentaro; Taguchi, Atsushi; Umeda, Norihiro; Masuda, Atsushi

    2014-01-01

    The formation of acetic acid via the penetration of moisture into ethylene vinyl acetate (EVA) in photovoltaic (PV) modules is cited as the main reason for PV modules’ degradation. Currently, there is no effective method for detecting acetic moisture in PV modules. We proposed a simple method for detecting acid moisture in PV modules using a dual-wavelength pH-sensitive dye that measures pH by the ratio of the intensities of two peaks in the fluorescence spectra of the dye. We detected the pH change caused by acetic acid with the change in the intensity ratio of the fluorescence spectra of the dried dye. Furthermore, we observed that the dry fluorescent dye is heat resistant to withstand the lamination process for the manufacturing of PV modules, and has good long-term durability.

  20. A tunable dual-wavelength pump source based on simulated polariton scattering for terahertz-wave generation

    NASA Astrophysics Data System (ADS)

    Sun, Bo; Liu, Jinsong; Yao, Jianquan; Li, Enbang

    2013-11-01

    We propose a dual-wavelength pump source by utilizing stimulated polariton scattering in a LiNbO3 crystal. The residual pump and the generated tunable Stokes waves can be combined to generate THz-wave generation via difference frequency generation (DFG). With a pump energy of 49 mJ, Stokes waves with a tuning range from 1067.8 to 1074 nm have been generated, and an output energy of up to 14.9 mJ at 1070 nm has been achieved with a conversion efficiency of 21.7%. A sum frequency generation experiment was carried out to demonstrate the feasibility of the proposed scheme for THz-wave DFG.

  1. pH Measurement Using Dual-Wavelength Fluorescent Ratio by Two-Photon Excitation for Mitochondrial Activity

    NASA Astrophysics Data System (ADS)

    Kanazashi, Yasuaki; Li, Yongbo; Onojima, Takumi; Iwami, Kentaro; Ohta, Yoshihiro; Umeda, Norihiro

    2012-11-01

    A mitochondrion has a pH gradient between the two sides of its inner membrane in order to produce adenosine triphosphate (ATP). Because ATP depletion causes numerous diseases, the measurement of the pH value around the mitochondrion is expected to clarify the mechanism of these diseases. In this study, a dual-wavelength pH-sensitive dye was excited by two-photon absorption initiated using a femtosecond pulse laser. In addition, fluorescence from the dye was directly collected from the fluorescent point using the collection-mode probe of a scanning near-field optical microscope. By this proposed method, a pH calibration curve was obtained from the fluorescent intensity ratio of the dye solution, and temporal pH variations with 0.1 s time resolution following the addition of acid were observed. Moreover, mitochondrial activity on the basis of the pH changes was successfully observed in three different mitochondrial densities.

  2. Dual-wavelength nano-engineered Thulium-doped fiber laser via bending of singlemode-multimode-singlemode fiber structure

    NASA Astrophysics Data System (ADS)

    Zulkifli, A. Z.; Latiff, A. A.; Paul, M. C.; Yasin, M.; Ahmad, H.; Harun, S. W.

    2016-12-01

    In this paper, a dual-wavelength fiber laser (DWFL) using nano-engineered Thulium-doped fiber as a gain medium with a bent singlemode-multimode-singlemode fiber structure (SMS) is demonstrated. The SMS structure is packaged systematically using Cr-39 polymer plates to provide linear bending via applied load. Experimental results have proved that the bent SMS is capable to provide highly effective wavelength filter and wavelengths stabilizer by balancing the net cavity gain between the two wavelengths. The DWFL provides very narrow spacing of 0.9 nm, narrow 3 dB spectral linewidth of ∼0.07 nm and SNR of ∼42 dB. Based on stability test, very small mode hopping is observed at the two wavelengths having deviations of ±0 nm and ±0.04 nm respectively. In conjunction, the DWFL provides very stable relative wavelength spacing with a deviation of ±0.04 nm.

  3. Switchable dual-wavelength erbium-doped fiber laser based on the photonic crystal fiber loop mirror and chirped fiber Bragg grating

    NASA Astrophysics Data System (ADS)

    Chen, Wei-Guo; Lou, Shu-Qin; Wang, Li-Wen; Li, Hong-Lei; Guo, Tieying; Jian, Shui-Sheng

    2010-03-01

    The switchable dual-wavelength erbium-doped fiber laser (EDFL) with a two-mode photonic crystal fiber (PCF) loop mirror and a chirped fiber Bragg grating (CFBG) at room temperature is proposed and experimentally demonstrated. The two-mode PCF loop mirror is formed by inserting a piece of two-mode PCF into a Sagnac loop mirror, with the air-holes of the PCF intentionally collapsing at the splices. By adjusting the state of the polarization controller (PC) appropriately, the laser can be switched between the stable single- and dual-wavelength operations by means of the polarization hole burning (PHB) and spectral hole burning (SHB) effects.

  4. Dual-wavelength erbium-doped fiber ring laser based on one polarization maintaining fiber Bragg grating in a Sagnac loop interferometer

    NASA Astrophysics Data System (ADS)

    Feng, Suchun; Li, Honglei; Xu, Ou; Lu, Shaohua; Mao, Xiangqiao; Ning, Tigang; Jian, Shuisheng

    2008-11-01

    Dual-wavelength with orthogonal polarizations erbium-doped fiber ring laser at room temperature is proposed. One polarization-maintaining fiber Bragg grating (PMFBG) in a Sagnac loop interferometer is used as the wavelength-selective filter. Due to the polarization hole burning (PHB) enhanced by the PMFBG, the laser can operate in stable dual-wavelength operation with wavelength spacing of 0.336 nm at room temperature by adjusting a polarization controller (PC). The optical signal-to-noise ratio (OSNR) is over 52 dB. The amplitude variation in nearly one and half an hour is less than 0.6 dB for both wavelengths.

  5. Sensitivity of S- and Ka-band matched dual-wavelength radar system for detecting nonprecipitating cloud

    NASA Astrophysics Data System (ADS)

    Vivekanandan, J.; Politovich, Marcia; Rilling, Robert; Ellis, Scott; Pratte, Frank

    2004-12-01

    Remote detection of cloud phase in either liquid, ice or mixed form a key microphysical observation. Evolution of a cloud system and associated radiative properties depend on microphysical characteristics. Polarization radars rely on the shape of the particle to delineate the regions of liquid and ice. For specified transmitter and receiver characteristics, it is easier to detect a high concentrations of larger atmospheric particles than a low concentration of small particles. However, the radar cross-section of a given hydrometeor increases as the transmit frequency of the radar increases. Thus, in spite of a low transmit power, the sensitivity of a millimeter-wave radar might be better than high powered centimeter-wave radars. Also, ground clutter echoes and receiver system noise powers are sensitive functions of radar transmit frequency. For example, ground clutter in centimeter-wave radar sample volumes might mask non-precipitating or lightly precipitating clouds. An optimal clutter filter or signal processing technique can be used to suppress clutter masking its effects and/or enhanced weak cloud echoes that have significantly different Doppler characteristics than stationary ground targets. In practice, it is imperative to investigate the actual performance of S and Ka-band radar systems to detect small-scale, weak cloud reflectivity. This paper describes radar characteristics and the sensitivity of the new system in non-precipitating conditions. Recently, a dual-wavelength S and Ka-band radar system with matched resolution volume and sensitivity was built to remotely detect supercooled liquid droplets. The detection of liquid water content was based on the fact that the shorter of the two wavelengths is more strongly attenuated by liquid water. The radar system was deployed during the Winter Icing Storms Project 2004 (WISP04) near Boulder, Colorado to detect and estimate liquid water content. Observations by dual-wavelength radar were collected in both non

  6. Active Q switching in a GaAs/AlGaAs multiquantum well laser with an intracavity monolithic loss modulator

    NASA Technical Reports Server (NTRS)

    Arakawa, Y.; Larsson, A.; Paslaski, J.; Yariv, A.

    1986-01-01

    Active Q switching in a GaAs/AlGaAs multiquantum well laser with an intracavity electroabsorption monolithic loss modulator is demonstrated. In this device, an efficient loss modulation is achieved through the quantum confined Stark effect in a modulator section and the enhanced carrier induced band shrinkage effect in an optical amplifier section. It is found that a picosecond pulse as narrow as 18.6 ps full width at half-maximum is generated and a high repetition rate of more than 3 GHz is obtained.

  7. Compact, Passively Q-Switched Nd:YAG Laser for the MESSENGER Mission to the Planet Mercury

    NASA Technical Reports Server (NTRS)

    Krebs, Danny J.; Novo-Gradac, Anne-Marie; Li, Steven X.; Lindauer, Steven J.; Afzal, Robert S.; Yu, Antony

    2004-01-01

    A compact, passively Q-switched Nd:YAG laser has been developed for the Mercury Laser Altimeter (MLA) instrument which is an instrument on the MESSENGER mission to the planet Mercury. The laser achieves 5.4 percent efficiency with a near diffraction limited beam. It has passed all space flight environmental tests at system, instrument, and satellite integration. The laser design draws on a heritage of previous laser altimetry missions, specifically ISESAT and Mars Global Surveyor; but incorporates thermal management features unique to the requirements of an orbit of the planet Mercury.

  8. Q-switched-like soliton bunches and noise-like pulses generation in a partially mode-locked fiber laser.

    PubMed

    Wang, Zhenhong; Wang, Zhi; Liu, Yan-Ge; Zhao, Wenjing; Zhang, Hao; Wang, Shangcheng; Yang, Guang; He, Ruijing

    2016-06-27

    We report an intermediate regime between c.w. emission and noise-like pulses (NLPs) regime in an Er-doped partially mode-locked fiber laser with nonlinear polarization rotation. In this regime, the soliton bunches stochastically turn up from a quasi-cw background in the Q-switched-like envelope. The soliton bunches normally last for tens or hundreds of intracavity round-trips. When the soliton bunches vanish, typical NLPs chains are generated sporadically at location where the soliton bunches collapses. These results would be helpful to understand the generation and property of the NLPs regime.

  9. Development of flashlamp-pumped Q-switched Ho:Tm:Cr:YAG lasers for mid-infrared LIDAR application

    NASA Technical Reports Server (NTRS)

    Choi, Young S.; Kim, Kyong H.; Whitney, Donald A.; Hess, Robert V.; Barnes, Norman P.; Bair, Clayton H.; Brockman, Philip

    1989-01-01

    A flashlamp-pumped 2.1 micron Ho:Tm:Cr:YAG laser was studied for both normal mode and Q-switched operations under a wide variety of experimental conditions in order to optimize performance. Laser output energy, slope efficiency, threshold and pulselength were determined as a function of operating temperature, output mirror reflectivity, input electrical energy and Q-switch opening time. The measured normal-mode laser thresholds of a Ho(3+) (0.45 atomic percent):Tm(3+) (2.5 atomic percent):Cr(3+) (0.8 atomic percent):YAG crystal ranged form 26 to 50 J between 120 and 200 K with slope efficiencies up to 0.36 percent with a 60 percent reflective output mirror. Under Q-switched operation the slope efficiency was 90 percent of the normal-mode result. Development of solid state lasers with Ho(3+), Tm(3+) and/or Er(3+) doped crystals has been pursued by NASA for eye-dafe mid-infrared LIDAR (light detection and ranging) application. As a part of the project, the authors have been working on evaluating Ho(3+):Tm(3+):Cr(3+):YAG crystals for normal-mode and Q-switched 2.1 micron laser operations in order to determine an optimum Tm(3+) concentration under flashlamp pumping conditions. Lasing properties of the Ho(3+) in the mid-infrared region have been studied by many research groups since the early 1960's. However, the technology of those lasers is still premature for lidar application. In order to overcome the inefficiency related to narrow absorption bands of the Ho(3+), Tm(3+) and Er(3+), the erbium has been replaced by chromium. The improvement in flashlamp-pumped Ho(3+) laser efficiency has been demonstrated recently by several research groups by utilizing the broad absorption spectrum of Cr(3+) which covers the flashlamp's emission spectrum. Efficient energy transfer to the Tm(3+) and then the Ho(3+) occurs subsequently. It is known that high Tm(3+) concentration and low Ho(3+) concentration are preferred to achieve a quantum efficiency approaching two and to avoid

  10. Passively Q-switched single-frequency 2μm laser used graphene as saturable absorber

    NASA Astrophysics Data System (ADS)

    Wang, Lei

    2016-04-01

    A graphene passively Q-switched single frequency Ho:YAG laser was demonstrated. Ho:YAG crystal was resonantly pumped by a 1908 nm diode laser. Twisted-mode single frequency technique was applied to realize single frequency oscillation. The maximum single frequency laser output was 358 mW. Single frequency pulse laser output was achieved by inserting a graphene into the single frequency Ho:YAG laser. The maximum average power of 149 mW was obtained with the pulse repetition rate of 40.45 kHz under 8.32 W of incident pump power.

  11. 456-mW graphene Q-switched Yb:yttria waveguide laser by evanescent-field interaction.

    PubMed

    Choudhary, Amol; Beecher, Stephen J; Dhingra, Shonali; D'Urso, Brian; Parsonage, Tina L; Grant-Jacob, James A; Hua, Ping; Mackenzie, Jacob I; Eason, Robert W; Shepherd, David P

    2015-05-01

    In this Letter, we present a passively Q-switched Yb:Y2O3 waveguide laser using evanescent-field interaction with an atmospheric-pressure-chemical-vapor-deposited graphene saturable absorber. The waveguide, pumped by a broad area diode laser, produced an average output power of 456 mW at an absorbed power of 4.1 W. The corresponding pulse energy and peak power were 330 nJ and 2 W, respectively. No graphene damage was observed, demonstrating the suitability of top-deposited graphene for high-power operation.

  12. Tm:KLu(WO(4))(2) microchip laser Q-switched by a graphene-based saturable absorber.

    PubMed

    Serres, Josep Maria; Loiko, Pavel; Mateos, Xavier; Yumashev, Konstantin; Griebner, Uwe; Petrov, Valentin; Aguiló, Magdalena; Díaz, Francesc

    2015-06-01

    We report on the first Tm-doped double tungstate microchip laser Q-switched with graphene using a Tm:KLu(WO4)2 crystal cut along the Ng dielectric axis. This laser generates a maximum average output power of 310 mW with a slope efficiency of 13%. At a repetition rate of 190 kHz the shortest pulses with 285 ns duration and 1.6 µJ energy are achieved.

  13. Partial unilateral lentiginosis treated with alexandrite Q-switched laser: case report and review of the literature.

    PubMed

    Pretel, Maider; Irarrazaval, Isabel; Aguado, Leyre; Lera, José Miguel; Navedo, María; Giménez de Azcárate, Ana

    2013-08-01

    Partial unilateral lentiginosis (PUL) is a rare pigmentary disorder characterized by multiple lentigines grouped within an area of normal skin, often in a segmental pattern and appearing at birth or in childhood. There is no established standard treatment for this condition. We present two cases of PUL succesfully treated with alexandrite Q-switched laser. In our cases, this laser proved to be a safe and effective treatment for cosmetically disfiguring lentigines. Special precautions are needed when treating dark-skinned patients because side effects are more likely. We propose that this modality be considered in the treatment of this rare disorder.

  14. Delivering dispersion-managed soliton and Q-switched pulse in fiber laser based on graphene and nonlinear optical loop mirror

    NASA Astrophysics Data System (ADS)

    Wang, W. B.; Wang, F.; Yu, Q.; Zhang, X.; Lu, Y. X.; Gu, J.

    2016-11-01

    We propose and experimentally demonstrate a bidirectional erbium-doped fiber laser delivering dispersion-managed soliton (DMS) and Q-switched pulse based on a graphene-polyvinyl alcohol (PVA) and nonlinear optical loop mirror (NOLM) saturable absorbers (SAs). In proposed structure, the DMS is achieved in clockwise (CW) direction and Q-switched pulse is obtained in counter-clockwise (CCW) direction. By properly adjusting the intracavity attenuators (ATT) and polarizer controllers (PCs), DMS in the CW direction and Q-switched pulse in the CCW direction can be obtained, respectively or simultaneously. The DMS with full width at half maximum (FWHM) of ~480 fs, signal to noise ratio (SNR) of ~60 dB and repetition frequency about 3.907 MHz is obtained. The Q-switched pulse is established at a pump power of 180 mW with a repetition rate of ~43.5 kHz and FWHM of ~8.18 μs. When the pump power is increased to 700 mW, Q-switched pulse with a repetition rate of ~107.1 kHz and FWHM of ~2.15 μs is generated. When the two type pulses are formed simultaneously, the maximum repetition rate of Q-switched pulse is 55.8 kHz and minimum FWHM is 2.81 μs, the DMS can be formed by properly adjusting PC and ATT in this case. To the best of our knowledge, it is the first time that Q-switched pulse and DMS have been acquired respectively or simultaneously in a fiber laser.

  15. Generation of dual-wavelength square pulse in a figure-eight erbium-doped fiber laser with ultra-large net-anomalous dispersion.

    PubMed

    Shao, Zhihua; Qiao, Xueguang; Rong, Qiangzhou; Su, Dan

    2015-08-01

    A type of wave-breaking-free mode-locked dual-wavelength square pulse was experimentally observed in a figure-eight erbium-doped fiber laser with ultra-large net-anomalous dispersion. A 2.7 km long single-mode fiber (SMF) was incorporated as a nonlinear optical loop mirror (NOLM) and provided largely nonlinear phase accumulation and anomalous dispersion, which enhanced the four-wave-mixing effect to improve the stability of the dual-wavelength operation. In the NOLM, the long SMF with small birefringence supported the Sagnac interference as a filter to manage the dual-wavelength lasing. The dual-wavelength operation was made switchable by adjusting the intra-cavity polarization loss and phase delay corresponding to two square pulses. When the pump power was increased, the duration of the square pulse increased continuously while the peak pulse power gradually decreased. This square-type pulse can potentially be utilized for signal transmission and sensing.

  16. Lidar Observations of Tropical High-altitude Cirrus Clouds: Results form Dual Wavelength Raman Lidar Measurements During the ALBATROSS Campaign 1996

    NASA Technical Reports Server (NTRS)

    Neuber, R.; Wegener, Alfred; Schrems, O.; McDermid, I. S.

    1997-01-01

    Results from dual wavelength Raman Lidar Observations of tropical high-altitude cirrus clouds are reported. Based on 107 hours of night-time measurements cirrus cloud were present in more than 50% of the observations at latitudes between 23.5 degress S and 23.5 degrees N and altitudes between 11 and 16km.

  17. WS₂ as a saturable absorber for ultrafast photonic applications of mode-locked and Q-switched lasers.

    PubMed

    Wu, Kan; Zhang, Xiaoyan; Wang, Jun; Li, Xing; Chen, Jianping

    2015-05-04

    Two-dimensional (2D) nanomaterials, especially the transition metal sulfide semiconductors, have drawn great interests due to their potential applications in viable photonic and optoelectronic devices. In this work, 2D tungsten disulfide (WS2) based saturable absorber (SA) for ultrafast photonic applications was demonstrated. WS2 nanosheets were prepared using liquid-phase exfoliation method and embedded in polyvinyl alcohol (PVA) thin film for the practical usage. Saturable absorption was discovered in the WS2-PVA SA at the telecommunication wavelength near 1550 nm. By incorporating WS2-PVA SA into a fiber laser cavity, both stable mode locking operation and Q-switching operation were achieved. In the mode locking operation, the laser obtained femtosecond output pulse width and high spectral purity in the radio frequency spectrum. In the Q-switching operation, the laser had tunable repetition rate and output pulse energy of a few tens of nano joule. Our findings suggest that few-layer WS2 nanosheets embedded in PVA thin film are promising nonlinear optical materials for ultrafast photonic applications as a mode locker or Q-switcher.

  18. Plate-shaped Yb:LuPO4 crystal for efficient CW and passively Q-switched microchip lasers

    NASA Astrophysics Data System (ADS)

    Liu, Junhai; Wang, Lisha; Han, Wenjuan; Xu, Honghao; Zhong, Degao; Teng, Bing

    2016-10-01

    It is demonstrated that plate-shaped crystals of Yb:LuPO4, which are grown from spontaneous nucleation by high-temperature solution method, can be utilized to make microchip lasers operating in continuous-wave (CW) or passively Q-switched mode. Efficient operation of such a microchip laser, which is built with a 0.3 mm thick crystal plate in a 2 mm long plane-parallel cavity, is realized at room temperature. With 2.37 W of pump power absorbed, 1.45 W of CW output power is generated with a slope efficiency of 73%. When passively Q-switched with a Cr4+:YAG crystal plate as saturable absorber, the laser produces a maximum pulsed output power of 0.53 W at 1013.3 nm, at a pulse repetition rate of 23.8 kHz, the resulting pulse energy, duration, and peak power are 22.3 μJ, 4.0 ns, and 5.6 kW, respectively.

  19. Passively Q-switched Ytterbium doped fiber laser with mechanically exfoliated MoS2 saturable absorber

    NASA Astrophysics Data System (ADS)

    Al-Masoodi, A. H. H.; Ahmed, M. H. M.; Latiff, A. A.; Arof, H.; Harun, S. W.

    2017-01-01

    A passively Q-switched Ytterbium-doped fiber laser (YDFL) based on MoS2 saturable absorber (SA) is demonstrated. A few layers of MoS2 are mechanically exfoliated from a natural MoS2 crystal using a scotch tape and the resulting SA is sandwiched between two fiber ferrules to form a fiber compatible Q-switcher. The saturation intensity, non-saturable intensity, and modulation depth of the MoS2 SA are 23.5 MW/cm2, 23.0, and 11.3%, respectively. By introducing the MoS2 SA into the YDFL cavity, a stable pulse laser is generated at 1070.2 nm wavelength with a threshold pump power of 49.57 mW. The repetition rate of the Q-switched pulses ranges from 3.817 to 25.25 kHz, as the 980 nm pump power increases from 49.57 to 87.2 mW. The highest pulse energy is 295.45 nJ at a pump power of 87.2 mW.

  20. CW and Q-switched GGG/Er:Pr:GGG/GGG composite crystal laser at 2.7 µm

    NASA Astrophysics Data System (ADS)

    You, Z. Y.; Wang, Y.; Sun, Y. J.; Xu, J. L.; Zhu, Z. J.; Li, J. F.; Wang, H. Y.; Tu, C. Y.

    2017-04-01

    We report the continuous-wave (CW) and passively Q-switched laser operations of a GGG/Er:Pr:GGG/GGG composite crystal at about 2.7 µm. Owing to the alleviation of the thermal lensing effect, the CW laser with a maximum output power of 463 mW was obtained with a slope efficiency of 15.5%. Based on the broadband saturable absorption property, a graphene saturable absorber (SA) mirror was fabricated and employed for realizing the Q-switched mid-infrared laser. Under an absorbed pump power of 2.47 W, an average output power of 186 mW was generated with a slope efficiency of 12.3%. The pulse width and the repetition rate of the laser were 360 ns and 120.5 kHz, respectively. These results indicate that the Er:Pr:GGG crystal, with the relatively lower upper-level lifetime, shows great promise for generating a short pulsed 2.7 µm mid-infrared laser using the graphene SA.

  1. Watt-level passively Q-switched double-cladding fiber laser based on graphene oxide saturable absorber.

    PubMed

    Yu, Zhenhua; Song, Yanrong; Dong, Xinzheng; Li, Yanlin; Tian, Jinrong; Wang, Yonggang

    2013-10-10

    A watt-level passively Q-switched ytterbium-doped double-cladding fiber laser with a graphene oxide (GO) absorber was demonstrated. The structure of the GO saturable absorber mirror (GO-SAM) was of the sandwich type. A maximum output power of 1.8 W was obtained around a wavelength of 1044 nm. To the best of our knowledge, this is the highest output power in Q-switched fiber lasers based on a GO saturable absorber. The pure GO was protected from the oxygen in the air so that the damage threshold of the GO-SAM was effectively raised. The gain fiber was a D-shaped ytterbium-doped double-cladding fiber. The pulse repetition rates were tuned from 120 to 215 kHz with pump powers from 3.89 to 7.8 W. The maximum pulse energy was 8.37 μJ at a pulse width of 1.7 μs.

  2. Megawatt-level peak-power from a passively Q-switched hybrid fiber-bulk amplifier and its applications

    NASA Astrophysics Data System (ADS)

    Reiser, Axel; Bdzoch, Juraj; Höfer, Sven; Scholz-Riecke, Sina; Seitz, Daniel; Kugler, Nicolas; Genter, Peter

    2016-03-01

    A novel laser system with optical parameters that fill the gap between Q-switched and modelocked lasers has been developed. It consists of a high gain hybrid fiber-bulk amplifier seeded by a low power SESAM Q-switched oscillator. The mW level output power of the seed oscillator is preamplified by a single mode fiber which is limited by SRS effects. The final amplification stage is realized by a longitudinal pumped Nd:YVO4 crystal in a double pass setup. This MOPA configuration delivers sub-300ps pulses at repetition rates up to 1 MHz with an output power exceeding 60W. Nonlinear frequency conversion to 532nm and 355nm is achieved with efficiencies of >75% and >45%, respectively. Due to the high peak power, high repetition rate and high beam quality of this system, applications formerly only addressable at lower pulse repetition frequencies or with complex modelocked laser systems are now possible with high speed and lower cost of ownership. Application results that take benefit from these new laser parameters will be shown. Furthermore, the reduction of the pulse duration to sub-100ps and power scaling to output powers <100W by the use of the Innoslab concept are being presented.

  3. Transversally diode-pumped Q-switched Nd:YAG laser with improved power and spatial characteristics

    NASA Astrophysics Data System (ADS)

    Bezyazychnaya, T. V.; Bogdanovich, M. V.; Grigor'ev, A. V.; Kabanov, V. V.; Kostik, O. E.; Lebiadok, Y. V.; Lepchenkov, K. V.; Mashko, V. V.; Ryabtsev, A. G.; Ryabtsev, G. I.; Shchemelev, M. A.; Teplyashin, L. L.

    2013-11-01

    The power and output beam spatial properties of the transversally diode-pumped Q-switched Nd:YAG laser with the active element surrounded by the low-absorption light-scattering layer have been investigated. The layer consisted of the bonding agent in which the solid particles, like aluminum oxide or magnesium oxide, effectively scattering the light was uniformly distributed. The particle diameter was mainly in the range of 2-5 μm. It has been shown that application of such layer to the diode-pumped Q-switched Nd:YAG laser head allows suppressing the amplified spontaneous emission and/or internally circulating parasitic lasing modes. At the optimized concentration of the light-scattering solid particles the output lasing pulses with the energy of 188-210 mJ (the wavelength of 1064 nm, the pulse repetition rate of 30 Hz) and improved spatial characteristics were obtained using the pump unit based on three laser diode matrixes.

  4. Multi-output Q-switched solid-state laser using an intra-cavity MEMS micromirror array

    NASA Astrophysics Data System (ADS)

    Bauer, Ralf; Lubeigt, Walter; Clark, Caspar; McBrearty, Euan; Uttamchandani, Deepak

    2013-03-01

    Multiple individually-controllable Q-switched laser outputs from a single diode-pumped Nd:YAG module are presented by using an electrostatic MEMS scanning micromirror array as cavity end-mirror. The gold coated, 700 μm diameter and 25 μm thick, single-crystal silicon micromirrors possess resonant tilt frequencies of ~8 kHz with optical scan angles of up to 78°. Dual laser output resulting from the actuation of two neighboring mirrors was observed resulting in a combined average output power of 125 mW and pulse durations of 30 ns with resulting pulse energies of 7.9 μJ and 7.1 μJ. The output power was limited by thermal effects on the gold-coated mirror surface. Dielectric coatings with increased reflectivity and therefore lower thermal stresses are required to power-scale this technique. An initial SiO2/Nb2O5 test coating was applied to a multi-mirror array with individual optical scan angles of 14° at a resonant tilt frequency of 10.4 kHz. The use of this dielectric coated array inside a 3-mirror Nd:YAG laser cavity led to a single mirror output with average Q-switched output power of 750 mW and pulse durations of 295 ns resulting in pulse energies of 36 μJ.

  5. Q-switched Erbium-doped fiber laser at 1600 nm for photoacoustic imaging application

    PubMed Central

    Zeng, Lvming; Chen, Zhongping; Kim, Chang-Seok

    2016-01-01

    We present a nanosecond Q-switched Erbium-doped fiber (EDF) laser system operating at 1600 nm with a tunable repetition rate from 100 kHz to 1 MHz. A compact fiber coupled, acousto-optic modulator-based EDF ring cavity was used to generate a nanosecond seed laser at 1600 nm, and a double-cladding EDF based power amplifier was applied to achieve the maximum average power of 250 mW. In addition, 12 ns laser pulses with the maximum pulse energy of 2.4 μJ were obtained at 100 kHz. Furthermore, the Stokes shift by Raman scattering over a 25 km long fiber was measured, indicating that the laser can be potentially used to generate the high repetition rate pulses at the 1.7 μm region. Finally, we detected the photoacoustic signal from a human hair at 200 kHz repetition rate with a pulse energy of 1.2 μJ, which demonstrates that a Q-switched Er-doped fiber laser can be a promising light source for the high speed functional photoacoustic imaging. PMID:27110032

  6. Hollow fiber optics with improved durability for high-peak-power pulses of Q-switched Nd:YAG lasers.

    PubMed

    Matsuura, Yuji; Tsuchiuchi, Akio; Noguchi, Hiroshi; Miyagi, Mitsunobu

    2007-03-10

    To improve the damage threshold of hollow optical waveguides for transmitting Q-switched Nd:YAG laser pulses, we optimize the metallization processes for the inner coating of fibers. For silver-coated hollow fiber as the base, second, and third Nd:YAG lasers, drying silver films at a moderate temperature and with inert gas flow is found to be effective. By using this drying process, the resistance to high-peak-power optical pulse radiation is drastically improved for fibers fabricated with and without the sensitizing process. The maximum peak power transmitted in the fiber is greater than 20 MW. To improve the energy threshold of aluminum-coated hollow fibers for the fourth and fifth harmonics of Nd:YAG lasers, a thin silver film is added between the aluminum film and the glass substrate to increase adhesion of the aluminum coating. By using this primer layer, the power threshold improves to 3 MW for the fourth harmonics of a Q-switched Nd:YAG laser light.

  7. Optimization of doubly Q-switched lasers with both an acousto-optic modulator and a GaAs saturable absorber.

    PubMed

    Li, Dechun; Zhao, Shengzhi; Li, Guiqiu; Yang, Kejian

    2007-08-20

    A doubly Q-switched laser with both an acousto-optic (AO) modulator and a GaAs saturable absorber can obtain a more symmetric and shorter pulse with high pulse peak power, which has been experimentally proved. The key parameters of an optimally coupled doubly Q-switched laser with both an AO modulator and a GaAs saturable absorber are determined, and a group of general curves are generated for what we believe is the first time, when the single-photon absorption (SPA) and two-photon absorption (TPA) processes of GaAs are combined, and the Gaussian spatial distributions of the intracavity photon density and the initial population-inversion density as well as the influence of the AO Q-switch are considered. These key parameters include the optimal normalized coupling parameter, the optimal normalized GaAs saturable absorber parameters, and the normalized parameters of the AO Q-switch, which can maximize the output energy. Meanwhile, the corresponding normalized energy, the normalized peak power, and the normalized pulse width are given. The curves clearly show the dependence of the optimal key parameters on the parameters of the gain medium, the GaAs saturable absorber, the AO Q-switch, and the resonator. Sample calculations for a diode-pumped Nd3+:YVO4 laser with both an AO modulator and a GaAs saturable absorber are presented to demonstrate the use of the curves and the relevant formulas.

  8. Study of Dual-Wavelength PIA Estimates: Ratio of Ka- and Ku-band Attenuations Obtained from Measured DSD Data

    NASA Astrophysics Data System (ADS)

    Liao, L.; Meneghini, R.; Tokay, A.

    2014-12-01

    Accurate attenuation corrections to the measurements of the Ku- and Ka-band dual-wavelength precipitation radar (DPR) aboard the Global Precipitation Measurement (GPM) satellite is crucial for estimates of precipitation rate and microphysical properties of hydrometeors. Surface reference technique (SRT) provides a means to infer path-integrated attenuation (PIA) by comparing differences of normalized surface cross sections (σ0) between rain and rain-free areas. Although single-wavelength SRT has been widely used in attenuation correction for airborne/spaceborne radar applications, its accuracy relies on the variance of σ0 in rain-free region. Dual-wavelength surface reference technique (DSRT) has shown promising ways to improve accuracy in PIA estimates over single-wavelength as a result of that the variance of the difference of PIA between two wavelengths (δPIA) is much smaller than the variance of σ0 at single wavelength arising from high correlation of σ0 between Ku- and Ka-bands. However, derivation of PIA at either wavelength from DSRT requires an assumption of the ratio of Ka- and Ku-band PIAs (p). Inappropriate assumption of this ratio will lead to the bias of PIA estimates. In this study the ratio p will be investigated through measured DSD data. The attenuation coefficients at Ku and Ka bands are first computed directly from measured DSD spectra, and then regression analysis is performed to the data points (Ku- and Ka-band attenuation coefficients) in obtaining p values for rain. Taking an advantage of large collection of the DSD measurements from various GPM Ground Validation (GPM GV) programs, the results of the ratio p will be examined from different climatological regimes. Because PIA is affected by all types of hydrometeors contained in the columns of radar measurements, the synthetic profiles composed of different types of hydrometeors are constructed using measured DSD to look into impacts of different phase hydrometeors on the p values. To

  9. High peak power Q-switched Er:YAG laser with two polarizers and its ablation performance for hard dental tissues.

    PubMed

    Yang, Jingwei; Wang, Li; Wu, Xianyou; Cheng, Tingqing; Jiang, Haihe

    2014-06-30

    An electro-optically Q-switched high-energy Er:YAG laser with two polarizers is proposed. By using two Al(2)O(3) polarizing plates and a LiNbO(3) crystal with Brewster angle, the polarization efficiency is significantly improved. As a result, 226 mJ pulse energy with 62 ns pulse width is achieved at the repetition rate of 3 Hz, the corresponding peak power is 3.6 MW. To our knowledge, such a high peak power has not been reported in literature. With our designed laser, in-vitro teeth were irradiated under Q-switched and free-running modes. Results of a laser ablation experiment on hard dental tissue with the high-peak-power laser demonstrates that the Q-switched Er:YAG laser has higher ablation precision and less thermal damage than the free-running Er:YAG laser.

  10. Q-switched mode-locked erbium-doped fiber laser based on topological insulator Bi(2)Se(3) deposited fiber taper.

    PubMed

    Gao, Lei; Huang, Wei; Zhang, Jing Dong; Zhu, Tao; Zhang, Han; Zhao, Chu Jun; Zhang, Wei; Zhang, Hua

    2014-08-10

    We have demonstrated the passive Q-switching mode-locking operation in an erbium-doped fiber (EDF) laser by using topological insulator Bi(2)Se(3) deposited on fiber taper, whose damage threshold can be further increased by the large evanescent field interacting length. Due to the low saturation intensity, stable Q-switched mode-locked fiber lasers centered at 1562 nm can be generated at a pump power of 10 mW. The temporal and spectral characteristics for different pump strengths have also been investigated. To the best of our knowledge, it is the first time a Q-switched mode-locked EDF laser based on the fiber taper deposited by Bi(2)Se(3) was generated.

  11. Fabrication of narrow pulse passively Q-switched self-stimulated Raman laser with c-cut Nd:GdVO4

    NASA Astrophysics Data System (ADS)

    Shen, Gao; Li, Zuo-han; Han, Ming

    2016-11-01

    Combining the self-stimulated Raman scattering technology and saturable absorber of Cr4+:YAG, a 1.17 μm c-cut Nd:GdVO4 picosecond Q-switched laser is demonstrated in this paper. With an incident pump power of 10 W, the Q-switched laser with average power of 430 mW for 1.17 μm, pulse width of 270 ps, repetition rate of 13 kHz and the first order Stokes conversion efficiency of 4.3% is obtained. The Q-switched pulse width can be the narrowest in our research. In addition, the yellow laser at 0.58 μm is also achieved by using the LiB3O5 frequency doubling crystal.

  12. Quantitative measurement of absolute cell volume and intracellular integral refractive index (RI) with dual-wavelength digital holographic microscopy (DHM)

    NASA Astrophysics Data System (ADS)

    Boss, Daniel; Kühn, Jonas; Depeursinge, Christian; Magistretti, Pierre J.; Marquet, Pierre

    2012-06-01

    Quantitative Phase Imaging techniques including DHM have been applied recently in the field of cell imaging to monitor and quantify non-invasively dynamic cellular processes modifying cell morphology and/or content . Concretely, the DHM phase signal is highly sensitive to cell thickness and intracellular integral RI variations associated with transmembrane water movements. As net water flow across the cell membrane leads at the same time to changes in cell thickness and intracellular RI, the interpretation of phase signal variations remains difficult. To overcome this drawback, we have developed a Dual-wavelength Digital Holographic Microscopy (DHM) setup allowing to separately measure, with a single CCD camera acquisition, thickness and integral RI of living cells. The method is based on the use of an absorbing dye that enhances the refractive index dispersion of the extracellular medium. Practically, two significantly different phase signals can be obtained when measuring at two appropriate wavelengths. From the two phase measurements, both cell RI and thickness can be univocally determined.

  13. Flexibly combined optical microangiography and dual-wavelength laser speckle system for comprehensive imaging of hemodynamic and metabolic responses

    NASA Astrophysics Data System (ADS)

    Shi, Lei; Qin, Jia; An, Lin; Wang, Ruikang K.

    2014-03-01

    We have proposed and developed a multi-modal non-invasive biomedical optical imager. It was combined from the subsystems of optical microangiography and dual-wavelength laser speckle contrast imaging. The system was designed to maintain the performances of both subsystems. It was capable of simultaneously imaging the hemodynamic and metabolic responses in tissue environment in vivo. To achieve such requirements, we utilized unique optical setup, such as paired dichroic mirrors to compensate dispersion, additional relay lens to increase working distance and translational sample probe to freely select imaging area and focal plane. The multi-functionality of the system was demonstrated in an investigation of hemodynamic and metabolic responses on an acute wound healing model in mouse pinna in vivo. The microvasculature, blood flow and hemoglobin concentration from millimeter down to capillary level were comprehensively visualized. The captured instantaneous responses to wound onset differed greatly between localized areas; after that blood flow had a rebalance tendency, and hemoglobin concentration dynamically recovered to baseline situation.

  14. Dual Wavelength RP-HPLC Method for Simultaneous Determination of Two Antispasmodic Drugs: An Application in Pharmaceutical and Human Serum

    PubMed Central

    Hasan, Najmul; Chaiharn, Mathurot; Khan, Sauleha; Khalid, Hira; Sher, Nawab; Siddiqui, Farhan Ahmed; Siddiqui, Muhammad Zain

    2013-01-01

    A reverse phase stability indicating HPLC method for simultaneous determination of two antispasmodic drugs in pharmaceutical parenteral dosage forms (injectable) and in serum has been developed and validated. Mobile phase ingredients consist of Acetonitrile : buffer : sulfuric acid 0.1 M (50 : 50 : 0.3 v/v/v), at flow rate 1.0 mL/min using a Hibar μBondapak ODS C18 column monitored at dual wavelength of 266 nm and 205 nm for phloroglucinol and trimethylphloroglucinol, respectively. The drugs were subjected to stress conditions of hydrolysis (oxidation, base, acid, and thermal degradation). Oxidation degraded the molecule drastically while there was not so much significant effect of other stress conditions. The calibration curve was linear with a correlation coefficient of 0.9999 and 0.9992 for PG and TMP, respectively. The drug recoveries fall in the range of 98.56% and 101.24% with 10 pg/mL and 33 pg/mL limit of detection and limit of quantification for both phloroglucinol and trimethylphloroglucinol. The method was validated in accordance with ICH guidelines and was applied successfully to quantify the amount of trimethylphloroglucinol and phloroglucinol in bulk, injectable form and physiological fluid. Forced degradation studies proved the stability indicating abilities of the method. PMID:24286017

  15. Retrieval of Raindrop Size Distribution, Vertical Air Velocity and Water Vapor Attenuation Using Dual-Wavelength Doppler Radar Observations

    NASA Technical Reports Server (NTRS)

    Heymsfield, Gerald M.; Tian, Lin; Li, Lihua; Srivastava, C.

    2005-01-01

    Two techniques for retrieving the slope and intercept parameters of an assumed exponential raindrop size distribution (RSD), vertical air velocity, and attenuation by precipitation and water vapor in light stratiform rain using observations by airborne, nadir looking dual-wavelength (X-band, 3.2 cm and W-band, 3.2 mm) radars are presented. In both techniques, the slope parameter of the RSD and the vertical air velocity are retrieved using only the mean Doppler velocities at the two wavelengths. In the first method, the intercept of the RSD is estimated from the observed reflectivity at the longer wavelength assuming no attenuation at that wavelength. The attenuation of the shorter wavelength radiation by precipitation and water vapor are retrieved using the observed reflectivity at the shorter wavelength. In the second technique, it is assumed that the longer wavelength suffers attenuation only in the melting band. Then, assuming a distribution of water vapor, the melting band attenuation at both wavelengths and the rain attenuation at the shorter wavelength are retrieved. Results of the retrievals are discussed and several physically meaningful results are presented.

  16. Functional evaluation of hemodynamic response during neural activation using optical microangiography integrated with dual-wavelength laser speckle imaging

    PubMed Central

    Qin, Jia; Shi, Lei; Wang, Hequn; Reif, Roberto; Wang, Ruikang K.

    2014-01-01

    Abstract. Evaluation of spatiotemporal hemodynamic and metabolic responses during neural activation is crucial in studying brain function. We explore the use of a noninvasive multifunctional optical imaging system to measure these responses in a mouse brain upon electrically stimulated neural activation, with the cranium left intact. The system is developed by integrating an optical microangiography (OMAG) imaging system with a dual-wavelength laser speckle imaging (DW-LSI) system. The DW-LSI, running at an image acquisition speed of ∼100  Hz, is used to extract the large-scale two-dimensional map, revealing the localized response of blood flow, hemoglobin concentration, and metabolic rate of oxygen change. Guided by DW-LSI, the OMAG is, however, used to image the response of individual blood vessels with its unique depth-resolved capability. We show that the integrated system is capable of investigating neural activation, thus is potentially valuable in the preclinical study of the mechanism of neurovascular coupling. PMID:24549439

  17. Dual-wavelength excited photoluminescence spectroscopy of deep-level hole traps in Ga(In)NP

    SciTech Connect

    Dagnelund, D.; Huang, Y. Q.; Buyanova, I. A.; Chen, W. M.; Tu, C. W.; Yonezu, H.

    2015-01-07

    By employing photoluminescence (PL) spectroscopy under dual-wavelength optical excitation, we uncover the presence of deep-level hole traps in Ga(In)NP alloys grown by molecular beam epitaxy (MBE). The energy level positions of the traps are determined to be at 0.56 eV and 0.78 eV above the top of the valance band. We show that photo-excitation of the holes from the traps, by a secondary light source with a photon energy below the bandgap energy, can lead to a strong enhancement (up to 25%) of the PL emissions from the alloys under a primary optical excitation above the bandgap energy. We further demonstrate that the same hole traps can be found in various MBE-grown Ga(In)NP alloys, regardless of their growth temperatures, chemical compositions, and strain. The extent of the PL enhancement induced by the hole de-trapping is shown to vary between different alloys, however, likely reflecting their different trap concentrations. The absence of theses traps in the GaNP alloy grown by vapor phase epitaxy suggests that their incorporation could be associated with a contaminant accompanied by the N plasma source employed in the MBE growth, possibly a Cu impurity.

  18. [Simultaneous determination of cobalt and nickel in catalyst by microwave digestion-dual wavelength equal absorption spectrophotometry].

    PubMed

    Li, L; Zhang, J; Gao, C

    2001-08-01

    Catalyst samples are digested in a microwave digestion system. The optimum parameters for microwave digestion are selected. Cobalt and nickel in the mixture of Co2+ and Ni2+ with 4-(2-pyridylazo) resorcinol (PAR) can be determined simultaneously by dual-wavelength equal absorption spectrophotometry. By means of the combination of two methods, Co2+ and Ni2+ in catalyst can be determined rapidly, accurately, and contamination problems avoided. The linear ranges are 0-30 micrograms.25 mL-1 for Co2+ and 0-25 micrograms.25 mL-1 for Ni2+. The recoveries of Co2+ and Ni2+ in synthetic samples are between 98.2%-103.6% and between 97.9%-103.7%, respectively. The relative standard deviations of analytical results in catalyst samples are less than 2.2% for Co2+ and less than 1.8% for Ni2+, and relative errors are less than +/- 2.5% for Co2+ and Ni2+.

  19. Linearly polarized, dual wavelength frequency-modulated continuous-wave fiber laser for simultaneous coherent distance and speed measurements

    NASA Astrophysics Data System (ADS)

    Chen, Tao; Wu, Jun; Xu, Weiming; He, Zhiping; Qian, Liqun; Shu, Rong

    2016-07-01

    We have experimentally demonstrated a high power linearly polarized, dual wavelength frequency-modulated continuous-wave (FMCW) fiber laser with master-oscillator power-amplifier (MOPA) configuration, which is specially designed for simultaneous coherent distance and speed measurements. Two single longitudinal mode laser diodes working at 1550.12 and 1554.13 nm are employed as the seeds of the fiber MOPA. The wavelengths of the seeds are externally modulated by two acousto-optic frequency shifters (AOFSes) with a symmetrical sawtooth wave from 330-460 MHz in the frequency domain. The modulation periodicities for the two seeds are 26 and 26.3 μs, respectively, by which the distance ambiguity can be eliminated and therefore the detection range can be extended to a great extent. The seeds are then amplified independently to reduce their power differences during frequency modulation. After being coupled and boosted with three successive fiber amplifiers, an output power of 12.1 W is recorded from the FMCW laser with a power instability   <0.14% over 1.5 h. The measured PER and full divergence angle of the laser are  >18 dB and  <25 μrad, respectively, indicating its excellent performance for field measurements.

  20. Q-switched all-solid-state lasers and application in processing of thin-film solar cell

    NASA Astrophysics Data System (ADS)

    Liu, Liangqing; Wang, Feng

    2009-08-01

    Societal pressure to renewable clean energy is increasing which is expected to be used as part of an overall strategy to address global warming and oil crisis. Photovoltaic energy conversion devices are on a rapidly accelerating growth path driven by government, of which the costs and prices lower continuously. The next generation thin-film devices are considered to be more efficiency and greatly reduced silicon consumption, resulting in dramatically lower per unit fabrication costs. A key aspect of these devices is patterning large panels to create a monolithic array of series-interconnected cells to form a low current, high voltage module. This patterning is accomplished in three critical scribing processes called P1, P2, and P3. All-solid-state Q-switched lasers are the technology of choice for these processes, due to their advantages of compact configuration, high peak-value power, high repeat rate, excellent beam quality and stability, delivering the desired combination of high throughput and narrow, clean scribes. The end pumped all-solid-state lasers could achieve 1064nm IR resources with pulse width of nanoseconds adopting acoustic-optics Q-switch, shorter than 20ns. The repeat rate is up to 100kHz and the beam quality is close to diffraction limit. Based on this, 532nm green lasers, 355nm UV lasers and 266nm DUV lasers could be carried out through nonlinear frequency conversion. Different wave length lasers are chose to process selective materials. For example, 8-15 W IR lasers are used to scribe the TCO film (P1); 1-5 W green lasers are suitable for scribing the active semiconductor layers (P2) and the back contact layers (P3). Our company, Wuhan Lingyun Photo-electronic System Co. Ltd, has developed 20W IR and 5W green end-pumped Q-switched all-solid-state lasers for thin-film solar industry. Operating in high repeat rates, the speed of processing is up to 2.0 m/s.

  1. Diode-pumped simultaneously Q-switched and mode-locked YVO4/Nd:YVO4/YVO4 crystal self-Raman first-Stokes laser.

    PubMed

    Huang, Guoxi; Yu, Yongqin; Xie, Xiaohua; Zhang, Yufeng; Du, Chenlin

    2013-08-26

    A diode-end-pumped simultaneously Q-switched and modelocked self-Raman YVO(4)/Nd:YVO(4)/YVO(4) laser at first-Stokes wavelength of 1175.9 nm was demonstrated. The shortest mode-locked pulse width of the laser was obtained to be ~23.57 ps, with the corresponding timebandwidth product of ~0.51. The maximum average output power, the highest pulse energy and the highest peak power were obtained to be 1.83 W, 6.1 μJ and 220 kW, respectively. The nonlinear Raman process improved the Q-switched mode-locking performance of the Stokes pulses.

  2. Continuous-wave and actively Q-switched resonantly dual-end-pumped Er : YAG ceramic laser emitting at 1.6 μm

    SciTech Connect

    Dai, T Y; Deng, Yu; Ju, Y-L; Yao, B Q; Duan, X M; Wang, Y Z

    2015-12-31

    We demonstrate a continuous-wave (cw) and actively Q-switched Er : YAG ceramic laser resonantly dual-end-pumped by a 1532 nm fibre-coupled laser diode. A maximum cw output power of 1.48 W at 1645.3 nm is obtained at an absorbed pump power of 12.72 W, corresponding to a slope efficiency of 19.2%. In the Q-switched regime the maximum pulse energy of 0.84 mJ is reached at a pulse repetition rate of 100 Hz, pulse duration of 48.03 ns and absorbed pump power of 10.51 W. (lasers)

  3. LD-pumped passively Q-switched Nd:GGG laser at 1062 nm with a GaAs saturable absorber

    NASA Astrophysics Data System (ADS)

    Zhang, H. N.; Li, P.; Wang, Q. P.; Chen, X. H.

    2011-11-01

    we have experimentally studied the passively Q-switched performance of a diode-pumped Nd:GGG laser at 1062 nm with a GaAs saturable absorber, in the experiment when the pumped power was 9.8 W, the maximum CW output power of 5.1 W was obtained. The optical conversion efficiency and the slop efficiency were 52 and 53%, respectively. The threshold was 0.9 W. In the passively Q-switched regime, we get the average output power of 0.93 W. The shortest pulse width and pulse repetition rate were 7 ns and 188 kHz, respectively.

  4. Passive Q-switching of Pr:LiYF4 orange laser at 604 nm using topological insulators Bi2Se3 as saturable absorber

    NASA Astrophysics Data System (ADS)

    Cheng, Yongjie; Peng, Jian; Bin, Xu; Xu, Huiying; Cai, Zhiping; Weng, Jian

    2017-02-01

    Q-switched laser operation of a laser diode pumped Pr:LiYF4 laser is reported at 604 nm using a topological insulator (TI) Bi2Se3 nanosheet material as saturable absorbers (SAs), for the first time to our knowledge. Stable Q-switched laser operation is obtained with shortest pulse width of about 802 ns, a maximum pulse repetition rate of 130 kHz, pulse energy of about 0.2 μJ and a maximum average output power of 26 mW. This work further extends the working wavelength of Bi2Se3 as saturable absorbers to visible domain.

  5. 36 W Q-switched Ho:YAG laser at 2097 nm pumped by a Tm fiber laser: evaluation of different Ho3+ doping concentrations

    NASA Astrophysics Data System (ADS)

    Antipov, O. L.; Eranov, I. D.; Kositsyn, R. I.

    2017-01-01

    A laser oscillator based on Ho:YAG crystal pumped by a Tm fiber laser with an acousto-optical Q-switch was optimized for maximum output power and pulse-to-pulse stability. Stable operation at 2097 nm in Q-switched mode is demonstrated, with pulse repetition rates from 10 to 30 kHz, and output power of 36 W (at 55 W of pump power at 1908 nm) in the good quality beam. The influence of Ho ion up-conversion and thermal lensing on the oscillation efficiency is discussed.

  6. Free-running and Q:Switched LIBS measurements during the laser ablation of Prickle Pears spines

    NASA Astrophysics Data System (ADS)

    Flores, T.; Ponce, L.; Arronte, M.; de Posada, E.

    2009-05-01

    The pulse laser ablation (PLA) as a new method for spines elimination of Prickle Pear fruit is presented. The new technique works thanks to the use of the pulsed light that is absorbed in a selective way, specifically in the spines. An optical characterization of both spine and cactus cortex allows to find the most convenient pulse energy for selective absorption. By using laser-induced breakdown spectroscopy (LIBS) in Q:Switch and free-running regimes, it is possible to control the process in real time and to check the cleaning results online. The feasibility of performing the laser ablation of spines without visible damages to the substrate was proved by the optical microscopy observation.

  7. In vivo analysis of solar lentigines by reflectance confocal microscopy before and after Q-switched ruby laser treatment.

    PubMed

    Richtig, Erika; Hofmann-Wellenhof, Rainer; Kopera, Daisy; El-Shabrawi-Caelen, Laila; Ahlgrimm-Siess, Verena

    2011-03-01

    Solar lentigines are benign lesions usually found on sun-damaged skin. We investigated twelve cases of solar lentigines through dermoscopy and reflectance confocal microscopy, performed before, and 30 min and 10 days after, a single treatment with a Q-switched ruby laser. At baseline, all lesions showed characteristic features of solar lentigines in reflectance confocal microscopy analysis: regular honeycomb patterns, edged dermal papillae and cord-like rete ridges at the dermoepidermal junction. Thirty minutes post-laser treatment, blurred epidermal intercellular connections, dark structureless areas of different sizes and shapes in the lower epidermal layers, and hyporeflective dermal papillae, reflecting epidermal and dermal oedema, were observed. Ten days post-treatment highly reflective round-to polygonal areas and aggregated granules, representing extracellular melanin, were detected in all epidermal layers featuring regular honeycomb patterns. Reflectance confocal microscopy can be used to visualise dynamic skin processes, allowing non-invasive in vivo follow-up of skin lesions after treatment.

  8. Fiber-optic delivery of high-peak-power Q-switched laser pulses for in-cylinder flow measurement.

    PubMed

    Stephens, Timothy J; Haste, Martin J; Towers, David P; Thomson, Martin J; Taghizadeh, Mohammed R; Jones, Julian D C; Hand, Duncan P

    2003-07-20

    A bundle of optical fibers was constructed to deliver Q-switched frequency-doubled Nd:YAG laser pulses for the purpose of particle image velocimetry. Data loss that is due to fiber speckle was reduced by ensuring that each fiber was different in length by more than the coherence length of the laser being delivered. Hence, their speckle patterns will overlap but not interfere, producing more even illumination that is shown to reduce data loss. A custom-made diffractive optical element and careful endface preparation help to reduce damage to the fibers by the required high peak powers. With this method, pulse energies in excess of 25 mJ were delivered for a series of experimental trials within the cylinder head of an optically accessed internal combustion engine. Results from these trials are presented along with a comparison of measurements generated by conventionally delivered beams.

  9. Fiber-optic delivery of high-peak-power Q-switched laser pulses for in-cylinder flow measurement

    NASA Astrophysics Data System (ADS)

    Stephens, Timothy J.; Haste, Martin J.; Towers, David P.; Thomson, Martin J.; Taghizadeh, Mohammed R.; Jones, Julian D. C.; Hand, Duncan P.

    2003-07-01

    A bundle of optical fibers was constructed to deliver Q-switched frequency-doubled Nd:YAG laser pulses for the purpose of particle image velocimetry. Data loss that is due to fiber speckle was reduced by ensuring that each fiber was different in length by more than the coherence length of the laser being delivered. Hence, their speckle patterns will overlap but not interfere, producing more even illumination that is shown to reduce data loss. A custom-made diffractive optical element and careful endface preparation help to reduce damage to the fibers by the required high peak powers. With this method, pulse energies in excess of 25 mJ were delivered for a series of experimental trials within the cylinder head of an optically accessed internal combustion engine. Results from these trials are presented along with a comparison of measurements generated by conventionally delivered beams.

  10. Severe unexpected adverse effects after permanent eye makeup and their management by Q-switched Nd:YAG laser.

    PubMed

    Goldman, Alberto; Wollina, Uwe

    2014-01-01

    Permanent makeup is a cosmetic tattoo that is used to enhance one's appearance, and which has become more popular among middle-aged and elderly women. A couple of benefits seem to be associated with permanent tattoos in the elderly: saving time (wake up with makeup); poor eyesight (difficult to apply makeup); and saving money. On the other hand, cosmetic tattoos bear the same risks as other tattoo procedures. We report on fading and unintended hyperpigmentation after tattooing on eyebrows and eyelids, and discuss the scientific and anatomical background behind the possible cause. Dermatochalasis may be a possible risk factor for excessive unwanted discolorations. Q-switched neodymium-doped yttrium aluminum garnet laser is an appropriate and safe therapeutic tool that can manage such adverse effects. Consumer protection warrants better information and education of the risks of cosmetic tattoos - in particular, for elderly women.

  11. The formation of iron aluminides on aluminum surface by using a Q-switched Nd:YAG laser

    SciTech Connect

    Bidin, Noriah; Al-Wafi, Yusef A.

    2014-03-05

    The formation and growth of Fe based aluminum diffusion layers at the Fe-Al interface have been investigated to improve the surface hardness. The diffusion of Fe into Al has been accomplished by focusing a Q-switched Nd:YAG laser on the modified surface. The variety of the layer depth is achieved based on the type of heating and quenching media. Microstructural characterization and mechanical properties of the modified surface were carried out via gas discharge spectrometer GDS, X-Ray diffraction (XRD), Scanning electron microscope (SEM), and Vickers Hardness tester. The results indicate that hardness at the interface of Fe-Al layer is increased. The optimum hardness achieved as 93 HV at corresponding critical energy density of 438 Jcm{sup −2}.

  12. Passively Q-switched erbium all-fiber lasers by use of thulium-doped saturable-absorber fibers.

    PubMed

    Tsai, Tzong-Yow; Fang, Yen-Cheng; Hung, Shih-Hao

    2010-05-10

    We demonstrate all-fiber passively Q-switched erbium lasers at 1570 nm using Tm(3+)-doped saturable-absorber fibers. The absorption cross section of a Tm(3+)-doped fiber at 1570 nm was measured in a bleaching experiment to be about 1.44 x 10(-20) cm(2). With a thulium-doped fiber, sequential pulses with a pulse energy of 9 microJ and a pulse duration of about 420 ns were stably produced at repetition rates in the range 0.1 to 2 kHz. The maximum pulse repetition rate was 6 kHz, limited by the maximum pump power of a 980-nm laser diode, about 230 mW.

  13. A 41-W ZnGeP₂ optical parametric oscillator pumped by a Q-switched Ho:YAG laser.

    PubMed

    Yao, Bao-Quan; Shen, Ying-Jie; Duan, Xiao-Ming; Dai, Tong-Yu; Ju, You-Lun; Wang, Yue-Zhu

    2014-12-01

    We reported a high-power ZnGeP₂ (ZGP) optical parametric oscillator (OPO) pumped by a Q-switched Ho:YAG laser. The maximum output power of the ZGP OPO was 41.2 W at 107.0 W incident Ho pump power, corresponding to a slope efficiency of 44.6%. The ZGP OPO produced 16-ns mid-IR pulse laser in the 3.74-3.98 μm and 4.38-4.76 μm spectral regions simultaneously. The beam quality was measured to be M²<4.37. The continuous wave maximum average output power of the Ho:YAG laser was 128 W, corresponding to a slope efficiency of 65.8%.

  14. Severe unexpected adverse effects after permanent eye makeup and their management by Q-switched Nd:YAG laser

    PubMed Central

    Goldman, Alberto; Wollina, Uwe

    2014-01-01

    Permanent makeup is a cosmetic tattoo that is used to enhance one’s appearance, and which has become more popular among middle-aged and elderly women. A couple of benefits seem to be associated with permanent tattoos in the elderly: saving time (wake up with makeup); poor eyesight (difficult to apply makeup); and saving money. On the other hand, cosmetic tattoos bear the same risks as other tattoo procedures. We report on fading and unintended hyperpigmentation after tattooing on eyebrows and eyelids, and discuss the scientific and anatomical background behind the possible cause. Dermatochalasis may be a possible risk factor for excessive unwanted discolorations. Q-switched neodymium-doped yttrium aluminum garnet laser is an appropriate and safe therapeutic tool that can manage such adverse effects. Consumer protection warrants better information and education of the risks of cosmetic tattoos – in particular, for elderly women. PMID:25143716

  15. Mode-locking and Q-switching in multi-wavelength fiber ring laser using low frequency phase modulation.

    PubMed

    Jun, Chang Su; Kim, Byoung Yoon

    2011-03-28

    We describe experimental investigation of pulsed output from a multi-wavelength fiber ring laser incorporating low frequency phase modulation with large modulation amplitude. The Erbium-doped fiber (EDF) ring laser generated more than 8 wavelength channels with the help of a phase modulator operating at 26.2 kHz and a periodic intra-cavity filter. For most cases, the laser output is pulsed in the form of mode-locking at 5.62 MHz and/or Q-switching at harmonic and sub-harmonic of the phase modulation frequency. Chaotic pulse output is also observed. The behavior of the output pulses are described as functions of pump power and phase modulation amplitude. The relative intensity noise (RIN) value of a single wavelength channel is measured to be under -100 dB/Hz (-140 dB/Hz beyond 1.5 GHz).

  16. All-fiber Q-switched operation of thulium-doped silica fiber laser by piezoelectric microbending.

    PubMed

    Sakata, Hajime; Araki, Shungo; Toyama, Ryo; Tomiki, Masahiro

    2012-03-10

    We demonstrate an all-fiber Q-switched laser operation in the 2 µm region on the basis of a dynamic periodic microbend and pulsed-pump configuration. A single-mode thulium-doped silica fiber is pumped by 1.6 µm-band laser diodes, and the dynamic loss is introduced in the fiber ring resonator by the periodic microbend that is electrically controlled with a piezoelectric actuator. When the voltage-off period of the piezoelectric actuator is set at 20 µs for the pump power of 120 mW, the output pulse power is measured by 420 mW with a pulse width of 1.3 µs.

  17. Nonlinear optical properties and Q-switch performance of silica glasses doped with CuxSe nanoparticles

    NASA Astrophysics Data System (ADS)

    Zolotovskaya, Svetlana A.; Savitski, Vasily G.; Prokoshin, Pavel V.; Yumashev, Konstantin V.; Gurin, Valerij S.; Alexeenko, Alexander A.

    2006-07-01

    Glasses containing copper selenide nanoparticles (CuxSe) reveal an intense absorption band peaking at 1 μm (1.24 eV). The transient bleaching and intensity-dependent transmission of silica glasses with CuxSe nanoparticles of different stoichiometry are studied with 1.08 μm (1.15 eV) picosecond pulses. The bleaching relaxation time decreases with a shift in the absorption band maximum to the lower photon energies. The dependence of absorption on the input energy of the pulses is saturationlike at the beginning of the plateau at ~40 mJ/cm2. Passive Q-switching of the Nd3+:KGd(WO4)2 laser at 1.067 μm is realized with the CuxSe-doped glasses for different x.

  18. Tunable diode laser-pumped Tm,Ho:YLF laser operated in continuous-wave and Q-switched modes

    NASA Technical Reports Server (NTRS)

    Mcguckin, B. T.; Hemmati, H.; Menzies, R. T.

    1992-01-01

    Tunable continuous-wave and pulsed laser output was obtained from a Tm-sensitized Ho:YLiF4 crystal at subambient temperatures when longitudinally pumped with a diode laser array. A conversion efficiency of 42 percent and slope efficiency of approximately 60 percent relative to the absorbed pumped power have been achieved at a crystal temperature of 275 K. The emission spectrum was etalon tunable over a range of 16/cm centered at 2067 nm with fine tuning capability of the transition frequency with crystal temperature at measured rate of -0.03/cm/K. Output energies of 0.22 mJ per pulse and 22 ns pulse duration were recorded at Q-switch frequencies that correspond to an effective upper laser level lifetime of 6 ms, and a pulse energy extraction efficiency of 64 percent.

  19. Switchable dual-wavelength erbium-doped fiber-ring laser based on one polarization maintaining fiber Bragg grating in a Sagnac loop interferometer

    NASA Astrophysics Data System (ADS)

    Feng, Suchun; Xu, Ou; Lu, Shaohua; Mao, Xiangqiao; Ning, Tigang; Jian, Shuisheng

    2009-04-01

    A switchable erbium-doped fiber-ring laser providing dual-wavelength outputs with orthogonal polarizations when operating at room temperature is proposed. One polarization-maintaining fiber Bragg grating (PMFBG) in a Sagnac loop interferometer is used as the wavelength-selective filter. Due to the enhancement of the polarization hole burning (PHB) by the PMFBG, the laser can be designed to operate in stable dual-wavelength or wavelength-switching modes with a wavelength spacing of 0.336 nm at room temperature by adjusting a polarization controller (PC). The optical signal-to-noise ratio (OSNR) is over 42 dB. The amplitude variation over 90 min is less than 0.6 dB for both wavelengths.

  20. Switchable single-longitudinal-mode dual-wavelength erbium-doped fiber laser based on one polarization-maintaining fiber Bragg grating incorporating saturable absorber

    NASA Astrophysics Data System (ADS)

    Feng, Suchun; Xu, Ou; Lu, Shaohua; Chen, Ming; Jian, Shuisheng

    2009-08-01

    Switchable single-longitudinal-mode (SLM) dual-wavelength erbium-doped fiber laser at room temperature is demonstrated. One fiber Bragg grating (FBG) directly written in a polarization-maintaining and photosensitive erbiumdoped fiber (PMPEDF) as the wavelength-selective component is used in a linear laser cavity. Due to the polarization hole burning (PHB) enhanced by the polarization-maintaining fiber Bragg grating (PMFBG), the laser can be designed to operate in stable dual-wavelength or wavelength-switching modes with a wavelength spacing of 0.202 nm by adjusting a polarization controller (PC). The stable SLM operation is guaranteed by a saturable absorber (SA). The optical signal-tonoise ratio (OSNR) of the laser is over 40 dB. The amplitude variation in nearly one and half an hour is less than 0.5 dB for both wavelengths.

  1. A geomorphologist's dream come true: synoptic high resolution river bathymetry with the latest generation of airborne dual wavelength lidar

    NASA Astrophysics Data System (ADS)

    Lague, Dimitri; Launeau, Patrick; Michon, Cyril; Gouraud, Emmanuel; Juge, Cyril; Gentile, William; Hubert-Moy, Laurence; Crave, Alain

    2016-04-01

    Airborne, terrestrial lidar and Structure From Motion have dramatically changed our approach of geomorphology, from low density/precision data, to a wealth of data with a precision adequate to actually measure topographic change across multiple scales, and its relation to vegetation. Yet, an important limitation in the context of fluvial geomorphology has been the inability of these techniques to penetrate water due to the use of NIR laser wavelengths or to the complexity of accounting for water refraction in SFM. Coastal bathymetric systems using a green lidar can penetrate clear water up to 50 m but have a resolution too coarse and deployment costs that are prohibitive for fluvial research and management. After early prototypes of narrow aperture green lidar (e.g., EEARL NASA), major lidar manufacturer are now releasing dual wavelength laser system that offer water penetration consistent with shallow fluvial bathymetry at very high resolution (> 10 pts/m²) and deployment costs that makes the technology, finally accessible. This offers unique opportunities to obtain synoptic high resolution, high precision data for academic research as well as for fluvial environment management (flood risk mapping, navigability,…). In this presentation, we report on the deployment of the latest generation Teledyne-Optech Titan dual-wavelength lidar (1064 nm + 532 nm) owned by the University of Nantes and Rennes. The instrument has been deployed over several fluvial and lacustrine environments in France. We present results and recommendation on how to optimize the bathymetric cover as a function of aerial and aquatic vegetation cover and the hydrology regime of the river. In the surveyed rivers, the penetration depth varies from 0.5 to 4 m with discrete echoes (i.e., onboard detection), heavily impacted by water clarity and bottom reflectance. Simple post-processing of the full waveform record allows to recover an additional 20 % depth. As for other lidar techniques, the main

  2. Concordance of macular pigment measurements obtained using customized heterochromatic flicker photometry, dual-wavelength autofluorescence, and single-wavelength reflectance.

    PubMed

    Dennison, Jessica L; Stack, Jim; Beatty, Stephen; Nolan, John M

    2013-11-01

    This study compares in vivo measurements of macular pigment (MP) obtained using customized heterochromatic flicker photometry (cHFP; Macular Metrics Densitometer(™)), dual-wavelength fundus autofluorescence (Heidelberg Spectralis(®) HRA + OCT MultiColor) and single-wavelength fundus reflectance (Zeiss Visucam(®) 200). MP was measured in one eye of 62 subjects on each device. Data from 49 subjects (79%) was suitable for analysis. Agreement between the Densitometer and Spectralis was investigated at various eccentricities using a variety of quantitative and graphical methods, including: Pearson correlation coefficient to measure degree of scatter (precision), accuracy coefficient, concordance correlation coefficient (ccc), paired t-test, scatter and Bland-Altman plots. The relationship between max MP from the Visucam and central MP from the Spectralis and Densitometer was investigated using regression methods. Agreement was strong between the Densitometer and Spectralis at all central eccentricities (e.g. at 0.25° eccentricity: accuracy = 0.97, precision = 0.90, ccc = 0.87). Regression analysis showed a very weak relationship between the Visucam and Densitometer (e.g. Visucam max on Densitometer central MP: R(2) = 0.008, p = 0.843). Regression analysis also demonstrated a weak relationship between MP measured by the Spectralis and Visucam (e.g. Visucam max on Spectralis central MP: R(2) = 0.047, p = 0.348). MP values obtained using the Heidelberg Spectralis are comparable to MP values obtained using the Densitometer. In contrast, MP values obtained using the Zeiss Visucam are not comparable with either the Densitometer or the Spectralis MP measuring devices. Taking cHFP as the current standard to which other MP measuring devices should be compared, the Spectralis is suitable for use in a clinical and research setting, whereas the Visucam is not.

  3. A novel mobile dual-wavelength laser altimetry system for improved site-specific Nitrogen fertilizer applications

    NASA Astrophysics Data System (ADS)

    Eitel, J.; Magney, T. S.; Vierling, L. A.; Brown, T. T.; Huggins, D. R.

    2012-12-01

    Reducing fertilizer inputs while maintaining yield would increase farmer's profits and similarly lessen the adverse environmental effects of production agriculture. The development of technologies that allow precise, site-specific application of Nitrogen (N) fertilizer has thus been an important research goal over the past decades. Remote sensing of foliar crop properties and function with tractor-mountable optical sensors has thought to be useful to optimize N fertilizer applications. However, on-the-go sensing of foliar crop properties and function has proven difficult, particularly during early crop growth stages when fertilizer decisions are often made. This difficulty arises from the fact that the spectral signal measured by on-the-go sensors is dominated by soil reflectance during early crop growth stages. Here, we present the basic principles behind a novel, dual-wavelength, tractor mountable laser altimetry system that measures the laser return intensity of the reflected green and red laser light. The green (532 nm) and the red (660 nm) wavelength combination allows calculation of a modified Photochemical Reflectance Index (mPRI) that have shown to be sensitive to both crop function and foliar chemistry. The small field of view of the laser points (diameter: 4 mm) combined with its high sampling rate (1000 points sec-1) allows vegetation returns to be isolated from ground returns by using simple thresholds. First tests relating foliar N of winter wheat (Triticum aestivum L.) with laser derived mPRI are promising (r2 = 0.72). Further research is needed to test the relationship between laser derived spectral indices and crop function.

  4. Dual-wavelength polarimetric glucose sensing in the presence of birefringence and motion artifact using anterior chamber of the eye phantoms

    PubMed Central

    Pirnstill, Casey W.; Coté, Gerard L.

    2013-01-01

    Abstract. Noninvasive glucose monitoring is being investigated as a tool for effectively managing diabetes mellitus. Optical polarimetry has emerged as one such method, which can potentially be used to ascertain blood glucose levels by measuring the aqueous humor glucose levels in the anterior chamber of the eye. The key limitation for realizing this technique is the presence of sample noise due to corneal birefringence, which in the presence of motion artifact can confound the glucose signature in the aqueous humor of the eye. We present the development and characterization of a real-time, closed-loop, dual-wavelength polarimetric system for glucose monitoring using both a custom-built plastic eye phantom (in vitro) and isolated rabbit corneas (ex vivo) mounted in an artificial anterior chamber. The results show that the system can account for these noise sources and can monitor physiologic glucose levels accurately for a limited range of motion-induced birefringence. Using the dual-wavelength system in vitro and ex vivo, standard errors were 14.5  mg/dL and 22.4  mg/dL, respectively, in the presence of birefringence with motion. The results indicate that although dual-wavelength polarimetry has a limited range of compensation for motion-induced birefringence, when aligned correctly, it can minimize the effect of time-varying corneal birefringence for a range of motion larger than what has been reported in vivo. PMID:23299516

  5. 2-μm Switchable dual-wavelength single-longitudinal-mode fiber laser based on a core-offset structure and carbon nanotube

    NASA Astrophysics Data System (ADS)

    Chen, Enci; Lu, Ping; Yang, Wei; Liu, Deming; Zhang, Jiangshan

    2016-11-01

    In this paper, we demonstrate a switchable single-longitudinal-mode (SLM) dual-wavelength fiber laser in 2-μm region based on a core-offset structure and carbon nanotube (CNT). The switchability of the fiber laser is based on a core-offset structure which acts as a tunable filter, so that the laser can work in stable dual-wavelength operation or switch between two wavelengths by adjusting the curvature of the core-offset structure. 3.68 nm (1919.44-1923.12 nm) and 6.32 nm (1890.64-1896.96 nm) tuning range can be obtained by tuning FBGs, respectively. The wavelength shift is less than 0.08 nm, and the power variation is smaller than 0.5 and 1 dB at 1923 and 1897 nm, respectively. The SLM oscillation is guaranteed by the CNT, which works as the loss factor to realize SLM oscillation. Absorption of the CNT increases the lasing threshold of the laser, therefore only the stronger mode can get lasing and SLM emission can be obtained. The proposed fiber laser offers a convenient and low-cost design for switchable dual-wavelength fiber laser in 2-μm region which has potential application in fields of gas sensing, lidar, and so on.

  6. A fiber laser pumped dual-wavelength mid-infrared laser based on optical parametric oscillation and intracavity difference frequency generation

    NASA Astrophysics Data System (ADS)

    Wang, Peng; Shang, Yaping; Li, Xiao; Shen, Meili; Xu, Xiaojun

    2017-02-01

    We report a dual-wavelength mid-infrared laser based on intracavity difference frequency generation (DFG) in an MgO-doped periodically poled LiNbO3, which was pumped by a dual-wavelength fiber MOPA consisting of two parts: a dual-wavelength seed and a power amplifier. The maximum pump power was 74.1 W and the wavelengths were 1060 nm and 1090 nm. The wavelengths of the mid-infrared output were 3.1 µm and 3.4 µm under maximum pump power with a total idler power of 6.57 W. The corresponding pump-to-idler slope efficiency reached 12%. The contrast for the peak intensity of the emissions for the two idlers was 0.6. A power preamplifier was added in a further experiment to enhance the contrast. The idler output reached 4.45 W under the maximum pump power of 70 W, which was lower than before. However, the contrast for the idler emission peak intensity was increased to 1.18. The signal wave generated in the experiment only had a single wavelength around 1.6 µm, indicating that two kinds of nonlinear processes occurred in the experiment, namely optical parametric oscillation and intracavity DFG.

  7. Experimental investigation of a diode-pumped powerful continuous-wave dual-wavelength Nd:YAG laser at 946 and 938.6 nm

    NASA Astrophysics Data System (ADS)

    Chen, F.; Yu, X.; Yan, R. P.; Li, X. D.; Li, D. J.; Yang, G. L.; Xie, J. J.; Guo, J.

    2013-05-01

    In this paper, a diode-pumped high-power continuous-wave (cw) dual-wavelength Nd:YAG laser at 946 and 938.6 nm is reported. By using an end-pumped structure, comparative experiments indicate that a 5 mm-length Nd:YAG crystal with a Nd3+-doping concentration of 0.3 at.% is favorable for high-power laser operation, and the optimal transmissivity of the output coupler is 9%. As a result, a maximum output power of 17.2 W for a dual-wavelength laser at 946 and 938.6 nm is obtained at an incident pump power of 75.9 W, corresponding to a slope efficiency of 26.5%. To the best of our knowledge, this is the highest output power of a quasi-three-level dual-wavelength laser using a conventional Nd:YAG crystal achieved to date. By using a traveling knife-edge method, the beam quality factor and far-field divergence angle at 17 W power level are estimated to be 4.0 and 6.13 mrad, respectively.

  8. Switchable 10 nm-spaced dual-wavelength SLM fiber laser with sub-kHz linewidth and high OSNR using a novel multiple-ring configuration

    NASA Astrophysics Data System (ADS)

    Feng, Ting; Ding, Dongliang; Zhao, Ziwei; Su, Hongxin; Yan, Fengping; Yao, X. Steve

    2016-10-01

    A switchable dual-wavelength (10 nm spacing) single-longitudinal-mode (SLM) erbium-doped fiber laser (EDFL) that uses a multiple-ring configuration was demonstrated experimentally. A novel theoretically lossless triple-ring passive secondary cavity composed of three optical couplers was utilized to select the SLM from the dense main cavity longitudinal modes for the first time. Using two superimposed fiber Bragg gratings as one compact mode-restricting element and introducing the nonlinear polarization rotation effect to alleviate the strong mode competition for the fiber laser, a highly stable dual-wavelength mode-hop-free SLM operation with sub-kHz linewidths and optical signal to noise ratios (OSNRs) of  >69 dB was achieved for both lasing wavelengths. By adjusting the polarization controllers, the dual-wavelength operation could be easily switched to single-wavelength lasing with a linewidth of  <1 kHz and an OSNR of  >72 dB. The proposed EDFL may find many important applications, such as the generation of very pure terahertz waves.

  9. Dual-wavelength polarimetric glucose sensing in the presence of birefringence and motion artifact using anterior chamber of the eye phantoms

    NASA Astrophysics Data System (ADS)

    Malik, Bilal H.; Pirnstill, Casey W.; Coté, Gerard L.

    2013-01-01

    Noninvasive glucose monitoring is being investigated as a tool for effectively managing diabetes mellitus. Optical polarimetry has emerged as one such method, which can potentially be used to ascertain blood glucose levels by measuring the aqueous humor glucose levels in the anterior chamber of the eye. The key limitation for realizing this technique is the presence of sample noise due to corneal birefringence, which in the presence of motion artifact can confound the glucose signature in the aqueous humor of the eye. We present the development and characterization of a real-time, closed-loop, dual-wavelength polarimetric system for glucose monitoring using both a custom-built plastic eye phantom (in vitro) and isolated rabbit corneas (ex vivo) mounted in an artificial anterior chamber. The results show that the system can account for these noise sources and can monitor physiologic glucose levels accurately for a limited range of motion-induced birefringence. Using the dual-wavelength system in vitro and ex vivo, standard errors were 14.5 mg/dL and 22.4 mg/dL, respectively, in the presence of birefringence with motion. The results indicate that although dual-wavelength polarimetry has a limited range of compensation for motion-induced birefringence, when aligned correctly, it can minimize the effect of time-varying corneal birefringence for a range of motion larger than what has been reported in vivo.

  10. Highly sensitive liquid-level sensor based on dual-wavelength double-ring fiber laser assisted by beat frequency interrogation.

    PubMed

    Dai, Yi; Sun, Qizhen; Tan, Sisi; Wo, Jianghai; Zhang, Jiejun; Liu, Deming

    2012-12-03

    A highly sensitive liquid-level sensor based on dual-wavelength single-longitudinal-mode fiber laser is proposed and demonstrated. The laser is formed by exploiting two parallel arranged phase-shift fiber Bragg gratings (ps-FBGs), acting as ultra-narrow bandwidth filters, into a double-ring resonators. By beating the dual-wavelength lasing output, a stable microwave signal with frequency stability better than 5 MHz is obtained. The generated beat frequency varies with the change of dual-wavelength spacing. Based on this characteristic, with one ps-FBG serving as the sensing element and the other one acting as the reference element, a highly sensitive liquid level sensor is realized by monitoring the beat frequency shift of the laser. The sensor head is directly bonded to a float which can transfer buoyancy into axial strain on the fiber without introducing other elastic elements. The experimental results show that an ultra-high liquid-level sensitivity of 2.12 × 10(7) MHz/m within the measurement range of 1.5 mm is achieved. The sensor presents multiple merits including ultra-high sensitivity, thermal insensitive, good reliability and stability.

  11. High peak power, 28 ns Q-switched Tm:LuAG laser at a 2 μm wavelength by dual-loss-modulation

    NASA Astrophysics Data System (ADS)

    Luan, Chao; Yang, Kejian; Zhao, Jia; Zhao, Shengzhi; Qiao, Wenchao; Li, Tao; Liu, Cheng; Chu, Hongwei; Qiao, Junpeng; Zheng, Lihe; Xu, Xiaodong; Xu, Jun

    2016-02-01

    By employing output couplers (OCs) with different transmissions T and GaAs saturable absorbers (SAs) with different modulation depth ΔR in a passively Q-switched Tm:LuAG laser at 2 μm, the optimal parameters of OCs and SAs for obtaining short pulse width and high peak power were investigated. By inserting an electro-optical modulator (EOM) into the optimized passively Q-switched Tm:LuAG laser (T  =  2%/ΔR  =  19%), a dual-loss-modulated Q-switched Tm:LuAG laser with an EOM and GaAs was realized. The experimental results show that the dual-loss-modulated Q-switched laser can generate a shorter pulse width and higher peak power than the single-loss-modulated case. At an incident pump power of 8.4 W, the shortest pulse width achieved was 28 ns and the highest peak power reached 74 kW.

  12. Optical parametric generation by a simultaneously Q-switched mode-locked single-oscillator thulium-doped fiber laser in orientation-patterned gallium arsenide.

    PubMed

    Donelan, Brenda; Kneis, Christian; Scurria, Giuseppe; Cadier, Benoît; Robin, Thierry; Lallier, Eric; Grisard, Arnaud; Gérard, Bruno; Eichhorn, Marc; Kieleck, Christelle

    2016-11-01

    Optical parametric generation is demonstrated in orientation-patterned gallium arsenide, pumped by a novel single-oscillator simultaneously Q-switched and mode-locked thulium-doped fiber laser, downconverting the pump radiation into the mid-infrared wavelength regime. The maximum output energy reached is greater than 2.0 μJ per pump pulse.

  13. Compact self-Q-switched green upconversion Er:ZBLAN all-fiber laser operating at 543.4  nm.

    PubMed

    Luo, Zhengqian; Ruan, Qiujun; Zhong, Min; Cheng, Yongjie; Yang, Runhua; Xu, Bin; Xu, Huiying; Cai, Zhiping

    2016-05-15

    We report the demonstration of a compact self-Q-switched green upconversion Er3+:ZrF4-BaF2-LaF3-AlF3-NaF (ZBLAN) fiber laser operating at 543.4 nm. The all-fiber green laser simply consists of a 45 cm high-concentration Er3+:ZBLAN fiber, a 976 nm pump source, and a pair of fiber end-facet mirrors. Under the strong excitation of the 976 nm pump laser, green upconversion lasing at 543.4 nm is achieved from the compact Er3+:ZBLAN fiber laser. Interestingly, the green laser exhibits stable self-Q-switching operation. As the 976 nm pump power is increased, the pulse repetition rate linearly increases from 25.9 to 50.8 kHz and the pulse width narrows from 7.2 to 1.95 μs. The Q-switched green laser has a pump threshold of 118 mW and a maximum output power of 6.9 mW with a slope efficiency of 30%. This is, to the best of our knowledge, the shortest-wavelength operation of a self-started or passively Q-switched fiber laser.

  14. Dynamical modeling and experiment for an intra-cavity optical parametric oscillator pumped by a Q-switched self-mode-locking laser

    NASA Astrophysics Data System (ADS)

    Wang, Jing; Liu, Nianqiao; Song, Peng; Zhang, Haikun

    2016-11-01

    The rate-equation-based model for the Q-switched mode-locking (QML) intra-cavity OPO (IOPO) is developed, which includes the behavior of the fundamental laser. The intensity fluctuation mechanism of the fundamental laser is first introduced into the dynamics of a mode-locking OPO. In the derived model, the OPO nonlinear conversion is considered as a loss for the fundamental laser and thus the QML signal profile originates from the QML fundamental laser. The rate equations are solved by a digital computer for the case of an IOPO pumped by an electro-optic (EO) Q-switched self-mode-locking fundamental laser. The simulated results for the temporal shape with 20 kHz EO repetition and 11.25 W pump power, the signal average power, the Q-switched pulsewidth and the Q-switched pulse energy are obtained from the rate equations. The signal trace and output power from an EO QML Nd3+: GdVO4/KTA IOPO are experimentally measured. The theoretical values from the rate equations agree with the experimental results well. The developed model explains the behavior, which is helpful to system optimization.

  15. Q-switched 2 μm thulium bismuth co-doped fiber laser with multi-walled carbon nanotubes saturable absorber

    NASA Astrophysics Data System (ADS)

    Saidin, N.; Zen, D. I. M.; Ahmad, F.; Haris, H.; Ahmad, H.; Dimyati, K.; Harun, S. W.; Halder, A.; Paul, M. C.; Pal, M.; Bhadra, S. K.

    2016-09-01

    We report a passively Q-switched fiber laser operating at 1900 nm region using the newly developed thulium bismuth co-doped lithium-alumino-germano-silicate fiber (TBF) as a gain medium in conjunction with a multiwall carbon nanotubes (MWCNTs) based saturable absorber (SA). The TBF and MWCNTs are fabricated and prepared in-house. By increasing the 802 nm pump power from 106.6 to 160 mW, stable generation of Q-switched TBFL has been obtained at 1857.8 nm wavelength. The pulse repetition rate varies from 12.84 to 29.48 kHz while pulse width is increased from 9.6 to 6.1 μs. The performance of the laser is also compared with the Q-switched TDFL, which was obtained using a similar MWCNTs SA and pump wavelength. The Q-switched TDFL generates an optical pulse train with a repetition rate increasing from 3.8 to 4.6 kHz and pulse width reducing from 22.1 to 18.3 μs when the pump power is tuned from 187.3 to 194.2 mW. This shows that the TBFL performs better than the TDFL in terms of threshold pump power, repetition rate and pulse width.

  16. Tunable passively Q-switched thulium-doped fiber laser operating at 1.9 μm using arrayed waveguide grating (AWG)

    NASA Astrophysics Data System (ADS)

    Samion, M. Z.; Ismail, M. F.; Muhamad, A.; Sharbirin, A. S.; Harun, S. W.; Ahmad, H.

    2016-12-01

    Thulium-doped fiber lasers (TDFLs), operating in the 1.8-2.0 μm wavelength region, have been viewed as an important research topic, due to their potential in various fields of applications. However, the growing need to advance the development of applications in various fields for instance medicine and environment sensor, has led to a deeper and specific study of Q-switched TDFLs with wavelength tunability. In this paper, a stable, tunable Q-switched TDFL operating in a wavelength range near to 1.9 μm by exploiting the use of a multiwall carbon nanotube (MWCNT)-based thin film as a saturable absorber (SA), and the use of an arrayed waveguide grating (AWG) for wavelength tunability, is presented. The tuning range of the Q-switched pulses generated covered a wavelength range that spanned from 1871.6 nm to 1888.8 nm. The repetition rate of the generated Q-switched pulses covers a range of frequency starting from 41.19 kHz to 68.3 kHz with a change in pump power from 242.2 mW until 360.9 mW.

  17. Switchable dual-wavelength single-longitudinal-mode erbium-doped fiber laser using an inverse-Gaussian apodized fiber Bragg grating filter and a low-gain semiconductor optical amplifier.

    PubMed

    Lin, Bo; Tjin, Swee Chuan; Zhang, Han; Tang, Dingyuan; Hao, Jianzhong; Dong, Bo; Liang, Sheng

    2010-12-20

    We present a stable and switchable dual-wavelength erbium-doped fiber laser. In the ring cavity, an inverse-Gaussian apodized fiber Bragg grating serves as an ultranarrow dual-wavelength passband filter, a semiconductor optical amplifier biased in the low-gain regime reduces the gain competition of the two wavelengths, and a feedback fiber loop acts as a mode filter to guarantee a stable single-longitudinal-mode operation. Two lasing lines with a wavelength separation of approximately 0.1 nm are obtained experimentally. A microwave signal at 12.51 GHz is demonstrated by beating the dual wavelengths at a photodetector.

  18. Hybrid Q-switched laser with MoS2 saturable absorber and AOM driven sub-nanosecond KTP-OPO.

    PubMed

    Qiao, Junpeng; Zhao, Shengzhi; Yang, Kejian; Zhao, Jia; Li, Guiqiu; Li, Dechun; Li, Tao; Qiao, Wenchao

    2017-02-20

    Two-dimensional (2D) materials, especially transition-metal dichalcogenides, such as molybdenum disulfide (MoS2) and tungsten disulfide (WS2), have attracted great interests due to their exceptional optical properties as saturable absorbers in laser systems. In this work, at first, we presented a diode-pumped passively Q-switched laser with MoS2 saturable absorber (MoS2-SA). At an incident pump power of 6.54 W, a maximum output power of 1.15 W with a minimum pulse duration of 70.6 ns was obtained, which is the shortest pulse duration of diode pumped passively Q-switched laser with MoS2-SA to the best of our knowledge. Then, by using a hybrid Q-switched laser with a MoS2-SA and an acousto-optic modulator (AOM) as pumping fundamental laser, a sub-nanosecond KTiOPO4 (KTP) based intracavity optical parametric oscillation (IOPO) was realized. With an incident pump power of 10.2 W and AOM repetition rate of 10 kHz, the maximum output power of 183 mW with minimum pulse duration of 850 ps was obtained. The experimental results indicate that the IOPO pumped by the hybrid Q-switched laser with AOM and MoS2-SA can generate signal wave with shorter pulse duration than those IOPOs pumped by hybrid Q-switched laser with AOM and Cr4+:YAG or single-walled carbon nanotube saturable absober (SWCNT-SA) or monolayer graphene SA.

  19. Treatment of enlarged pores with the quasi long-pulsed versus Q-switched 1064 nm Nd:YAG lasers: A split-face, comparative, controlled study

    PubMed Central

    Roh, MR; Goo, BC; Jung, JY; Chung, HJ; Chung, KY

    2011-01-01

    Background and Aims: A variety of treatment modalities have been used to reduce the size of en-larged pores. The 1064 nm Nd:YAG laser, in addition to its role in removal of tattoos and age-related dyschromia, depilation and skin rejuvenation, may also play a role in reducing the size of enlarged pores. The present split-face controlled study assessed and compared the efficacy between the quasi long-pulsed (micropulsed) and the Q-switched modes of the Nd:YAG laser in the treatment of enlarged pores. Subjects and Methods: Twenty subjects with enlarged pores were recruited for the micropulsed vs Q-switched study, all treated with the same 1064 nm Nd:YAG laser system. Ten subjects were treated with the 300 µs micropulsed mode and the other ten subjects were treated with the 5 ns Q-switched mode. All subjects were treated on the right half of the face, the left half serving as an untreated control. Five laser sessions were performed. The pore sizes were measured using an image analysis program and the sebum level was measured with a Sebumeter® before and after the treatments. Results: The pore size and sebum level significantly decreased with treatment on the treated side (right cheek and right half of nose) in both the micropulsed and Q-switched modes compared to the control side (p<0.05), but without any statistically significant difference between the modes. Conclusions: The micropulsed and Q-switched Nd:YAG laser treatments reduced pore size and sebum levels with more or less equal efficacy and with no adverse side effects. PMID:24155526

  20. A randomized, split-face clinical trial of Q-switched alexandrite laser versus Q-switched Nd:YAG laser in the treatment of bilateral nevus of Ota.

    PubMed

    Wen, Xiang; Li, Yong; Jiang, Xian

    2016-01-01

    Different types of Q-switched (QS) lasers have been used successfully to treat nevus of Ota. The purpose of this study was to compare the clinical efficacy and complication of QS alexandrite (QS Alex) laser versus QS neodymium:yttrium aluminum garnet (Nd:YAG) (QS Nd:YAG) laser for bilateral nevus of Ota. Seventeen patients with bilateral nevus of Ota were treated randomly with QS Alex in one half of face and QS Nd:YAG in the other half with an interval of at least 3 months between each. Subjective assessment was made by both patients and dermatologists. Patients were also examined for evidence of complications. All patients experienced improvement (p < 0.05). There was no statistically significant difference between the two sides (p > 0.05). The pain after a short period of laser therapy was more severe for QS Alex than for QS Nd:YAG laser. Vesicles developed in 1 patient after QS Alex therapy. Both QS Alex laser and QS Nd:YAG laser were equally effective at improving bilateral nevus of Ota. Patients tolerate QS Nd:YAG laser better than QS Alex laser.

  1. Characterization of long-range transported Saharan dust across the Atlantic Ocean; dual-wavelength lidar measurements during SALTRACE

    NASA Astrophysics Data System (ADS)

    Gross, Silke; Freudenthaler, Volker; Schäfler, Andreas; Schepanski, Kerstin; Heinold, Bernd; Toledano, Carlos; Wiegner, Matthias; Weinzierl, Bernadett

    2015-04-01

    Mineral dust is a major component of the atmospheric aerosol load which main source region is the Saharan desert. Dust layers can be transported over thousands of kilometers and thus they cannot be considered as regional phenomenon. During long-range transport the particles are influenced by aging and mixing processes altering the microphysical and thus the optical properties of Saharan dust. But the influence of long-range transport on the particle properties and their effect on the Earth's radiation budget is still not well understood. To study aging processes of transported Saharan dust as well as the microphysical, optical and radiative properties of long-range transported dust the Saharan Aerosol Long-range Transport and Aerosol-Cloud-Interaction Experiment (SALTRACE) took place at Barbados in June and July 2013. SALTRACE was designed as closure study combining ground-based and airborne lidar and in-situ measurements with Satellite observations, long-term measurements at Barbados, and model calculations. During SALTRACE four main dust events occurred with column integrated AOD of up to 0.6. The vertical aerosol distribution was characterized by a three layer structure consisting of a marine dominated boundary layer, a highly variable mixing layer often affected by clouds, and a Saharan dust layer in heights between 2 km and 3.5 km in some cases even up to 5 km. We will present first results of the ground-based measurements with the dual-wavelength lidar system POLIS of the Meteorological Institute of the Ludwig-Maximilians Universität, München. In particular we will investigate measurements of the particle linear depolarization ratio and the lidar ratio of the different aerosol layers. We compare our findings with results of the Saharan Mineral Dust Experiment (SAMUM) studying Saharan dust close to the source region in Morocco and at the beginning of the long-range transport on the Cape Verde Islands. In addition, we assess the influence of long

  2. Intense Pulsed Light and Low-Fluence Q-Switched Nd:YAG Laser Treatment in Melasma Patients

    PubMed Central

    Na, Se Young; Cho, Soyun

    2012-01-01

    Background Recently, low fluence collimated Q-switched (QS) Nd:YAG laser has drawn attention for the treatment of melasma. However, it needs a lot of treatment sessions for the substantial results and repetitive laser exposures may end up with unwanted depigmentation. Objective We evaluated the clinical effects and safety of the combinational treatment, using intense pulsed light (IPL) and low fluence QS Nd:YAG laser. Methods Retrospective case series of 20 female patients, with mixed type melasma, were analyzed using medical records. They were treated with IPL one time, and 4 times of weekly successive low fluence Nd:YAG laser treatments. At each visit, digital photographs were taken under the same condition. Melanin index (MI) and erythema index (EI) were measured on the highest point on the cheekbones. Modified melasma area and severity index (MASI) scores were calculated by two investigators using digital photographs. Results The mean values of MI and EI decreased significantly after treatments. The modified MASI score has decreased by 59.35%, on average. Sixty percents of the participants did not require any more treatments, and no clinical aggravations were observed during the follow-up period (mean 5.9 months). Conclusion IPL and low fluence laser may elicit a clinical resolution in the mixed type melasma with long term benefits. PMID:22879709

  3. Dynamic photopatterning of cells in situ by Q-switched neodymium-doped yttrium ortho-vanadate laser.

    PubMed

    Deka, Gitanjal; Okano, Kazunori; Kao, Fu-Jen

    2014-01-01

    Cellular micropattering has been increasingly adopted in quantitative biological experiments. A Q-switched pulsed neodymium-doped yttrium ortho-vanadate (Nd∶YVO4) laser directed in-situ microfabrication technique for cell patterning is presented. A platform is designed uniquely to achieve laser ablation. The platform is comprised of thin gold coating over a glass surface that functions as a thermal transducer and is over-layered by a cell repellant polymer layer. Micropatterns are engraved on the platform, subsequently exposing specific cell adhesive micro-domains by ablating the gold-polymer coating photothermally. Experimental results indicate that the proposed approach is applicable under culture conditions, viable toward cells, and has a higher engraving speed. Possible uses in arraying isolated single cells on the platform are also shown. Additionally, based on those micro-patterns, dynamic cellular morphological changes and migrational speed in response to geometrical barriers are studied to demonstrate the potential applications of the proposed approach. Our results further demonstrate that cells in narrower geometry had elongated shapes and higher migrational speed than those in wider geometry. Importantly, the proposed approach will provide a valuable reference for efforts to study single cell dynamics and cellular migration related processes for areas such as cell division, wound healing, and cancer invasion.

  4. Passive Q-switching of a Tm:YLF laser with a Co2+ doped silver halide saturable absorber

    NASA Astrophysics Data System (ADS)

    Hecht, Harel; Burshtein, Zeev; Katzir, Abraham; Noach, Salman; Sokol, Maxim; Frumker, Eugene; Galun, Ehud; Ishaaya, Amiel A.

    2017-02-01

    We report a successful passive Q-switching of a Tm:YLF laser operating at λ = 1.9 μm, using a Co2+:AgCl0.5Br0.5 saturable absorber. Approximately 200-ns long, 150 μJ pulses were obtained. Increase in pump energy resulted in repetitive pulsing, with a repetition rate approximately proportional to the pump pulse energy. Room-temperature optical transmission saturation curves measured in ∼1-mm thick Co2+:AgCl0.5Br0.5 plates yielded a ground state absorption cross section σgs =(7.8 ± 0.5) ×10-18 cm2 , and an excited state absorption cross section σes =(3.3 ± 0.3) ×10-18 cm2 , at λ = 1.9 μm. The lifetime of the A2(4F) second excited-state of the octahedral O symmetry was τ∗ =(0.6 ± 0.06) ns .

  5. Experimental retinectomy with a 6.1 μm Q-switched Raman-shifted alexandrite laser

    NASA Astrophysics Data System (ADS)

    Joos, Karen M.; Prasad, Ratna; Kozub, John; Ivanov, Borislav; Agarwal, Anita; Shen, Jin H.

    2010-02-01

    Purpose: It is hypothesized that 6.1 μm produced by a portable laser would be useful for incising tissue layers such as performing a retinectomy in detached retina with extensive anterior proliferative vitreoretinopathy. Methods: An alexandrite laser system, which provides a high-intensity Q-switched pulse (780 nm, 50-100 ns duration, 10 Hz), is wavelength-shifted by a two-stage stimulated Raman conversion process into the 6-7 μm range (Light Age, Inc.). Fresh cadaver porcine retinas were lased with 6.1 μm using a 200 μm diameter spot at 0.6 mJ after removal of the vitreous. Specimens were examined grossly and prepared for histological examination. Results: The Raman-shifted alexandrite laser produced a smooth Gaussian profile. A narrow spectrum was produced at 6.1 μm. A full-thickness retinal incision with minimal thermal damage was obtained at a low energy level of 0.6 mJ in the retinas. However, the depth of the incision did vary from an incomplete incision to a full-thickness incision involving the underlying choroidal layer in attached retinas. Conclusions: The 6.1 μm mid-infrared energy produced by a portable laser is capable of incising detached retinas with minimal thermal damage.

  6. Supercontinuum generation in polarization maintaining photonic crystal fiber by using various harmonics of sub-nanosecond Q-switched laser

    NASA Astrophysics Data System (ADS)

    Vengelis, Julius; Jarutis, Vygandas; Sirutkaitis, Valdas

    2016-04-01

    We present results of supercontinuum generation in highly nonlinear polarization maintaining photonic crystal fiber using various harmonics of sub-nanosecond passively Q-switched Nd:YAG microlaser. The pump source was a Nd:YAG microlaser generating 50 μJ energy 300 ps duration pulses at 1064 nm with kilohertz repetition rate. We demonstrated that we can expand the supercontinuum spectrum to cover the whole visible range and beyond using either first or second harmonic of our pump laser in simple experimental setups: supercontinuum extended from 400 nm to 1300 nm in case of λp = 1064 nm and from 400 nm to 900 nm in case of λp = 532 nm. We compared supercontinuum evolution and dependence on pump pulse energy in both cases. We also performed numerical simulations of supercontinuum generation in PCF by applying the traditional approach of solving generalized nonlinear Schrödinger equation (GNLSE) and also presented a new numerical simulation approach -deriving and solving equation for evolution of spectral components of pulse propagating in the PCF. In case of GNLSE approach, the simulated supercontinuum spectra display the same qualitative features as the ones measured in the experiment.

  7. Low-pulse energy Q-switched Nd:YAG laser treatment for hair-dye-induced Riehl's melanosis.

    PubMed

    On, Hye Rang; Hong, Won Jin; Roh, Mi Ryung

    2015-06-01

    Riehl's melanosis, a form of dermatitis characterized by reticulate pigmentation, typically presents as a gray-brown to black hyperpigmentation on the face and neck. Among the various etiologic factors suggested, photoallergic reaction and pigmented contact dermatitis resulting from exposure to drugs, coal tar dyes, optical whitener, or other ingredients found in cosmetics are believed to be the major contributing factors in this disease. The histopathological features of Riehl's melanosis mainly consist of pigmentary incontinence along with infiltration of numerous dermal melanophages and lymphohistiocytes.1,2 Additionally, notable clinical improvements in the treatment of this condition have been reported for intense pulsed light (IPL) therapy, in comparison to long-term topical application of bleaching agents.2 Here, we report the cases of two Asian patients treated with a low-pulse energy 1,064-nm Q-switched (QS) Nd:YAG laser for hair dye-induced Riehl's melanosis on the face and neck. In conclusion, we observed that Riehl's melanosis on the face and neck was effectively and safely treated with a low-pulse energy 1,064-nm QS Nd:YAG laser. We suggest that this method can be used in Asian patients with Riehl's melanosis at risk of postinflammatory hyperpigmentation from excessive light or laser energy delivery.

  8. Dual-wavelength excitation to reduce background fluorescence for fluorescence spectroscopic quantitation of erythrocyte zinc protoporphyrin-IX and protoporphyrin-IX from whole blood and oral mucosa

    NASA Astrophysics Data System (ADS)

    Hennig, Georg; Vogeser, Michael; Holdt, Lesca M.; Homann, Christian; Großmann, Michael; Stepp, Herbert; Gruber, Christian; Erdogan, Ilknur; Hasmüller, Stephan; Hasbargen, Uwe; Brittenham, Gary M.

    2014-02-01

    Erythrocyte zinc protoporphyrin-IX (ZnPP) and protoporphyrin-IX (PPIX) accumulate in a variety of disorders that restrict or disrupt the biosynthesis of heme, including iron deficiency and various porphyrias. We describe a reagent-free spectroscopic method based on dual-wavelength excitation that can measure simultaneously both ZnPP and PPIX fluorescence from unwashed whole blood while virtually eliminating background fluorescence. We further aim to quantify ZnPP and PPIX non-invasively from the intact oral mucosa using dual-wavelength excitation to reduce the strong tissue background fluorescence while retaining the faint porphyrin fluorescence signal originating from erythrocytes. Fluorescence spectroscopic measurements were made on 35 diluted EDTA blood samples using a custom front-face fluorometer. The difference spectrum between fluorescence at 425 nm and 407 nm excitation effectively eliminated background autofluorescence while retaining the characteristic porphyrin peaks. These peaks were evaluated quantitatively and the results compared to a reference HPLC-kit method. A modified instrument using a single 1000 μm fiber for light delivery and detection was used to record fluorescence spectra from oral mucosa. For blood measurements, the ZnPP and PPIX fluorescence intensities from the difference spectra correlated well with the reference method (ZnPP: Spearman's rho rs = 0.943, p < 0.0001; PPIX: rs = 0.959, p < 0.0001). In difference spectra from oral mucosa, background fluorescence was reduced significantly, while porphyrin signals remained observable. The dual-wavelength excitation method evaluates quantitatively the ZnPP/heme and PPIX/heme ratios from unwashed whole blood, simplifying clinical laboratory measurements. The difference technique reduces the background fluorescence from measurements on oral mucosa, allowing for future non-invasive quantitation of erythrocyte ZnPP and PPIX.

  9. Modulating dual-wavelength multiple quantum wells in white light emitting diodes to suppress efficiency droop and improve color rendering index

    SciTech Connect

    Zhao, Yukun; Wang, Shuai; Zheng, Min; Ding, Wen; Yun, Feng; Su, Xilin; Yang, Xiangrong; Liu, Shuo; Guo, Maofeng; Zhang, Ye

    2015-10-14

    In this paper, gallium nitride (GaN) based white light-emitting diodes (WLEDs) with modulated quantities of blue (In{sub 0.15}Ga{sub 0.85}N) quantum wells (QWs) and cyan QWs (In{sub 0.18}Ga{sub 0.82}N) in multiple QW (MQW) structures have been investigated numerically and experimentally. It is demonstrated that the optical performance of LEDs is sensitive to the quantities of cyan QWs in dual-wavelength MQW structures. Compared to the LEDs with respective 0, 4, and 8 cyan QWs (12 QWs in total), the optical performance of the sample with 6 cyan QWs is the best. The deterioration of the optical performance in the sample with less (4 pairs) cyan QWs or more (8 pairs) cyan QWs than 6 cyan QWs may be ascribed to weakened reservoir effect or more defects induced. Compared to conventional blue LEDs (12 blue QWs), the sample with 6 cyan QWs could effectively suppress the efficiency droop (the experimental droop ratio decreases from 50.3% to 39.5% at 80 A/cm{sup 2}) and significantly improve the color rendering index (CRI, increases from 66.4 to 77.0) simultaneously. We attribute the droop suppression to the strengthened reservoir effect and carrier confinement of deeper QWs (higher indium composition) incorporated in the dual-wavelength MQW structures, which lead to the better hole spreading and enhanced radiative recombination. Meanwhile, the remarkable experimental CRI improvement may result from the wider full-width at half-maximum of electroluminescence spectra and higher cyan intensity in WLED chips with dual-wavelength MQW structures.

  10. A compact dual-wavelength Nd:LuVO4 laser with adjustable power-ratio between 1064 nm and 1342 nm lines by controlling polarization dependent loss

    NASA Astrophysics Data System (ADS)

    Qi, Yaoyao; Yu, Haijuan; Zhang, Jingyuan; Zhang, Ling; He, Chaojian; Lin, Xuechun

    2017-01-01

    We demonstrate a compact dual-wavelength operation of Nd:LuVO4 laser with a power-ratio adjustable between 1064 nm and 1342 nm lines in a compound cavity configuration. The output power at two wavelengths of the laser indicates that it depends not only on pumping-power and but also on the controllable polarization loss in the cavity. Also, the power-ratio, defined as ratio between the output power at 1064 nm and that at 1342 nm, can be adjusted from 0 to 8 or higher accurately by rotating a quarter-wave plate (QWP) in the cavity.

  11. Efficient dual-wavelength excitation of Tb3+ emission in rare-earth doped KYF4 cubic nanocrystals dispersed in silica sol-gel matrix

    NASA Astrophysics Data System (ADS)

    del-Castillo, J.; Yanes, A. C.; Santana-Alonso, A.; Méndez-Ramos, J.

    2014-11-01

    Energy transfer from Ce3+ to Tb3+ ions under UV excitation, giving rise to visible emissions, is investigated in sol-gel derived transparent nano-glass-ceramics containing cubic KYF4 nanocrystals, for different doping concentrations of rare-earth ions. Moreover, visible emissions of Tb3+ are also obtained under near-infrared excitation through energy transfer from Yb3+ ions by means of cooperative up-conversion processes. Thus, Ce3+-Tb3+-Yb3+ doped nano-glass-ceramics can be activated in a dual-wavelength mode yielding efficient blue-green emissions of particular interest in photovoltaic silicon solar cells and white-light emitting diodes.

  12. Dual-wavelength in-line phase-shifting interferometry based on two dc-term-suppressed intensities with a special phase shift for quantitative phase extraction.

    PubMed

    Xu, Xiaoqing; Wang, Yawei; Xu, Yuanyuan; Jin, Weifeng

    2016-06-01

    To efficiently promote the phase retrieval in quantitative phase imaging, a new approach of quantitative phase extraction is proposed based on two intensities with dual wavelength after filtering the corresponding dc terms for each wavelength, in which a special phase shift is used. In this approach, only the combination of the phase-shifting technique and subtraction procedures is needed, and no additional algorithms are required. The thickness of the phase object can be achieved from the phase image, which is related to the synthetic beat wavelength. The feasibility of this method is verified by the simulated experiments of the optically transparent objects.

  13. Mid-infrared difference-frequency generation source pumped by 1.1-1.5 micrometer dual-wavelength fiber amplifier for trace-gas detection

    NASA Technical Reports Server (NTRS)

    Goldberg, L.; Koplow, J.; Lancaster, D. G.; Curl, R. F.; Tittel, F. K.

    1998-01-01

    Continuous-wave mid-infrared radiation near 3.5 micrometers is generated by difference-frequency mixing of the output of a compact 1.1-1.5 micrometer dual-wavelength fiber amplifier in periodically poled LiNbO3. The diode side-pumped amplifier is constructed with double-cladding Yb-doped fiber followed by single-mode Er/Yb codoped fiber. Output powers of as much as 11 microW at 3.4 micrometers are obtained, and spectroscopic detection of CH4 and H2CO is demonstrated. c 1998 Optical Society of America.

  14. Investigations of Q-switching and mode locking in diode-pumped Nd:YVO4 laser with passive saturable absorbers

    NASA Astrophysics Data System (ADS)

    Kwiatkowski, Jacek; Jabczynski, Jan K.; Zendzian, Waldemar

    2005-03-01

    The saturable absorbers (Cr4+:YAG, GaAs and LiF crystals for 1064-nm wavelength, V3+:YAG crystals for 1340-nm respectively) were examined as passive Mode Lockers and Q-switches in diode pumped Nd:YVO4 lasers in the Z-type resonators. In each case, partially modulated long trains of QML pulses were observed. As a rule, envelopes with about 1 μs duration and more than 50% depth of modulation were observed. For stabilization of the mode locking trains nonlinear crystals (KTP or LBO) as negative feedback elements were inserted. The fully modulated QML trains for intracavity II harmonic conversion at 670-nm wavelength in V3+:YAG Q-switched Nd:YVO4 laser with LBO crystal were demonstrated.

  15. Generation of Q-switched mode locking controlled rectangular noise-like soliton bunching in a Tm-doped fiber laser.

    PubMed

    Qiao, Tian; Chen, Weicheng; Lin, Wei; Yang, Zhongmin

    2016-08-08

    We report on an interesting phenomenon of the combination of Q-switched mode locked pulses (QSMLP) and rectangular noise-like pulses (RNLP) as a unit in a Tm-doped ring fiber laser which contains a Fabry-Perot (F-P) subcavity based on the nonlinear polarization evolution (NPE) technique. The RNLP and QSMLP are independently generated in the ring cavity and F-P subcavity, respectively. A notable characteristic is that the physical parameters of RNLP, e.g. repetition rate and pulse duration, are controlled by QSMLP. Thus, they form as a composite bunching, which is termed as "Q-switched mode locking controlled rectangular noise-like soliton bunching (QRNSB)". Further investigation shows that the existence of QRNSB only occurs in high pumping conditions, while both fundamental mode-locking pulses and the coexistence of QSMLP and solitons are achieved in low pumping ones. Our work can enrich the understanding of the nonlinear dynamics in fiber lasers.

  16. Stable Q-switched and mode-locked Nd:GdVO4/KTP green laser with dual-loss-modulation.

    PubMed

    Zhang, Gang; Zhao, Shengzhi; Li, Guiqiu; Li, Dechun; Yang, Kejian; Cheng, Kang; Zhang, Yan

    2010-08-20

    A diode-pumped dual-loss-modulated Q-switched and mode-locked (QML) Nd:GdVO(4)/KTP green laser with an acousto-optic modulator (AOM) and GaAs saturable absorber is presented. The experimental results show that the stability and the peak power of the dual-loss-modulated QML Nd:GdVO(4)/KTP green laser are significantly improved. The pulse width of the Q-switched pulse envelope in the dual-loss-modulation QML green laser has a compression of 50% compared with that in the singly passively QML green laser with GaAs. By using a hyperbolic secant square function and considering the Gaussian distribution of the intracavity photon density, the coupled equations for diode-pumped dual-loss-modulated QML Nd:GdVO(4) green laser are given, and the numerical solutions of the equations are in good agreement with the experimental results.

  17. Passively Q-switched, intracavity frequency-doubled YVO{sub 4}/Nd : YVO{sub 4}/KTP green laser with a GaAs saturable absorber

    SciTech Connect

    Shang Gao

    2015-11-30

    A diode-pumped, passively Q-switched, intracavity frequency-doubled YVO{sub 4}/Nd : YVO{sub 4}/KTP green laser is realised using a GaAs saturable absorber. Two pieces of GaAs wafers are employed in the experiment. In using a 400-μm-thick GaAs wafer and an incident pump power of 10.5 W, the maximum output power of the passively Q-switched green laser is 362 mW at a pulse repetition rate of 84 kHz and a pulse duration of 2.5 ns. When use is made of a 700-mm-thick GaAs wafer, the minimum pulse duration is 1.5 ns at a repetition rate of 67 kHz, pulse energy of 4.18 μJ and peak power of 2.8 kW. (control of laser radiation parameters)

  18. Enhancement of passively Q-switched performance at 1.34 μm with a class of Nd:GdxY(1-)xVO(4) crystals.

    PubMed

    Li, Xin; Li, Guiqiu; Zhao, Shengzhi; Xu, Chao; Li, Yufei; Liu, Hong; Zhang, Huaijin

    2010-10-11

    Passively Q-switched operation at 1.34 μm in which V:YAG was employed as saturable absorber has been demonstrated with a series of mixed Nd:GdxY(1-)xVO(4) crystals. The Q-switched laser pulse performance with these Nd-doped mixed vanadate crystals, especially Nd:Gd(0.63)Y(0.37)VO(4), was enhanced in respect to Nd:GdVO(4) under the identical conditions. The average output power of 171.3 mW with the shortest pulse width of 44.4 ns, largest single pulse energy of 21.7 μJ, and highest peak power of 489 W at the incident pump power of 5.04 W were obtained with Nd:Gd(0.63)Y(0.37)VO(4) crystal.

  19. All-fiber passively Q-switched 604  nm praseodymium laser with a Bi2Se3 saturable absorber.

    PubMed

    Lin, Hui-Yu; Li, Wen-Song; Lan, Jing-Long; Guan, Xiao-Feng; Xu, Hui-Ying; Cai, Zhi-Ping

    2017-02-01

    We experimentally demonstrated a simple passively Q-switched praseodymium (Pr3+)-doped all-fiber laser at 604 nm with a Bi2Se3 saturable absorber (SA). A Bi2Se3/polyvinyl alcohol composite film is sandwiched between two ferrules to construct a fiber-compatible Q-switcher. Two fiber end facet mirrors build a compact-linear resonator. The repetition rate of the achieved 604 nm Q-switching pulse can be widely tuned from 86.2 to 187.4 kHz, and the pulse duration can be as narrow as 494 ns. To the best of our knowledge, this is the shortest operation wavelength of a Bi2Se3-based pulsed all-fiber laser at 604 nm.

  20. 88 ns multi-millijoule LiNbO3 electro-optically Q-switched Tm:LuAG laser

    NASA Astrophysics Data System (ADS)

    Liu, C.; Yang, K.; Zhao, S.; Li, Y.; Li, G.; Li, D.; Li, T.; Qiao, W.; Feng, T.; Chen, X.

    2015-11-01

    An electro-optical modulator (EOM) made of a z-cut LiNbO3 (LN) crystal with size of 9×9×25 mm3 was designed to work in transverse-field regime. The extinction ratio of the EOM was measured to be 324:1. With the EOM operating in off Q-switching regime, a diode pumped all-solid-state actively Q-switched Tm:LuAG laser at 2 μm was realized. At repetition rate of 200 Hz, 2.5 mJ pulses with duration of 88.2 ns were generated. A maximum pulse energy of 2.51 mJ was achieved at repetition rate of 50 Hz, corresponding to a minimum pulse duration of 88 ns.