Science.gov

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. PMID:23481809

  2. Dual-wavelength passively q-switched single-frequency fiber laser.

    PubMed

    Zhang, Yuanfei; Yang, Changsheng; Feng, Zhouming; Deng, Huaqiu; Peng, Mingying; Yang, Zhongmin; Xu, Shanhui

    2016-07-11

    We propose a compact dual-wavelength Q-switched single-frequency fiber laser based on a 17-mm-long home-made highly Er3+/Yb3+ co-doped phosphate fiber (EYDPF) and a semiconductor saturable absorber mirror (SESAM). The short cavity length and a polarization-maintaining fiber Bragg grating (PM-FBG) ensure that only one longitudinal mode is supported by each reflection peak. The maximum pulse energy of more than 34.5 nJ was realized with the shortest pulse duration of 110.5 ns and the Q-switched fiber laser has a repetition rate reaching over 700 kHz with a temporal synchronization of pulses at two wavelengths. Besides, the optical signal-to-noise ratio (OSNR) of larger than 64.5 dB was achieved. PMID:27410881

  3. Electro-optically Q-switched dual-wavelength Nd:YLF laser emitting at 1047 nm and 1053 nm

    NASA Astrophysics Data System (ADS)

    Men, Shaojie; Liu, Zhaojun; Cong, Zhenhua; Li, Yongfu; Zhang, Xingyu

    2015-05-01

    A flash-lamp pumped electro-optically Q-switched dual-wavelength Nd:YLF laser is demonstrated. Two Nd:YLF crystals placed in two cavities are employed to generate orthogonally polarized 1047 nm and 1053 nm radiations, respectively. The two cavities are jointed together by a polarizer and share the same electro-optical Q-switch. Two narrow-band pass filters are used to block unexpected oscillations at the hold-off state of the electro-optical Q-switch. In this case, electro-optical Q-switching is able to operate successfully. With pulse synchronization realized, the maximum output energy of 66.2 mJ and 83.9 mJ are obtained for 1047 nm and 1053 nm lasers, respectively. Correspondingly, the minimum pulse width is both 17 ns for 1047 nm and 1053 nm lasers. Sum frequency generation is realized. This demonstrates the potential of this laser in difference-frequency generations to obtain terahertz wave.

  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. PMID:27409120

  5. 808-nm diode-pumped dual-wavelength passively Q-switched Nd:LuLiF4 laser with Bi-doped GaAs

    NASA Astrophysics Data System (ADS)

    Li, S. X.; Li, T.; Li, D. C.; Zhao, S. Z.; Li, G. Q.; Hang, Y.; Zhang, P. X.; Li, X. Y.; Qiao, H.

    2015-09-01

    Diode-pumped CW and passively Q-switched Nd:LuLiF4 lasers with stable, synchronous dual-wavelength operations near 1047 and 1053 nm were demonstrated for the first time. The maximal CW output power of 821 mW was obtained at an incident pump power of 6.52 W. Employing high quality Bi-doped GaAs as saturable absorber, stable dual-wavelength Q-switched operation was realized. Under 6.52 W incident pump power, the minimal pulse duration of 1.5 ns, the largest single pulse energy of 11.32 μJ, and the highest peak power of 7.25 kW were achieved.

  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. Doubly passively Q-switched Yb:NaY(WO4)2 laser with dual-wavelength phenomenon

    NASA Astrophysics Data System (ADS)

    Lan, Ruijun

    2015-06-01

    A diode pumped doubly passively Q-switched \\text{Yb:NaY}≤ft(\\text{W}{{\\text{O}}4}\\right)2/\\text{C}{{\\text{r}}4+}\\text{:YAG}/\\text{GaAs} laser was realized for the first time to our knowledge. Compared with the singly passively Q-switched \\text{Yb:NaY}≤ft(\\text{W}{{\\text{O}}4}\\right)2/\\text{C}{{\\text{r}}4+}\\text{:YAG} laser, this laser can generate a higher repetition rate, and more symmetric and shorter pulses. The highest repetition rate and shortest pulse width was measured to be 82 kHz and 6 ns. At certain pump power, 1022 and 1026 nm dual-wavelength lasers were obtained, and the mechanism of this phenomenon was discussed.

  8. Passively Q-switched and mode-locked dual-wavelength Nd:GGG laser with Cr4+:YAG as a saturable absorber

    NASA Astrophysics Data System (ADS)

    Chu, Hongwei; Zhao, Shengzhi; Li, Yufei; Yang, Kejian; Li, Guiqiu; Li, Dechun; Zhao, Jia; Qiao, Wenchao; Li, Tao; Feng, Chuansheng; Zhang, Haijuan

    2014-03-01

    By using neodymium-doped gadolinium gallium garnet (Nd:GGG) as a laser medium, a simultaneously passively Q-switched and mode-locked (QML) dual-wavelength laser with Cr4+:YAG as a saturable absorber is presented. The laser simultaneously oscillated at 1061 nm and 1063 nm, corresponding to a frequency difference of 0.53 THz. QML pulses with nearly 100% modulation depth were observed. The mode-locked pulse duration underneath the Q-switched envelope was estimated to be about 908 ps. The experimental results indicated that the dual-wavelength QML Nd:GGG laser can be an excellent candidate for the generation of THz waves.

  9. 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).

  10. Experimental Study on Dual Wavelength and Dual Pulse Q-Switched Frequency Doubling on a Tunable Cr:LiSAF Laser

    NASA Astrophysics Data System (ADS)

    Chen, Chang-Shui; Zhang, Yi-Shi; Yu, Jin-Wang; Fang, Jian; Liu, Song-Hao

    2009-09-01

    A flashlamp-pumped Cr:LiSAF laser system with a voltage controlled Q-switch structure in the cavity is designed. A dual-wavelength and dual-pulse tunable laser output is gained. The relation of laser output behavior with input energy is studied experimentally. The output is dual-pulsed with the energy of the 32 mJ/pulse producing the total output energy of 64 mJ and the pulse width is about 27 ns at 850 nm. Then, we use one LBO crystal as the frequency doubling crystal to obtain a dual wavelength (448.1 nm and 449.15 nm) and dual pulse laser. The output for one wavelength is about 10.3 mJ and the line width is less than 0.02 nm.

  11. 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.

  12. Synchronous initiation of optical detonators by Q-switched solid laser sources

    NASA Astrophysics Data System (ADS)

    Goujon, J.; Musset, O.; Marchand, A.; Bigot, C.

    2008-10-01

    The initiation of pyrotechnic substances by a laser light has been studied for more than 30 years. But until recently the use of this technology for defence applications encountered three main technical problems: the volume and the mass of lasers, the linear loss of optical fibres and their possible damage caused by the transport of strong laser power. Recent technical progress performed in the field of electrical and optical devices are now very promising for future opto-pyrotechnic functional chains. The objective of this paper is to present a demonstrator developed in order to initiate in a synchronous way four optical detonators and to measure the dispersion of their functioning times. It includes four compact Q-switched Nd:Cr:GSGG solid laser sources, pumped by flash lamp (energy ~110mJ, FWHM ~8.5 ns), two ultra-fast electro-optical selectors (based on RTP crystals) used to steer the laser beam and six optical fibre lines to transmit the laser pulses to the optical detonators. The set-up integrates also complex control and safety systems, as well as cameras allowing an optimal alignment of optical fibres. Experiments led us to initiate in a synchronous way four detonators with a mean scattering of 50 ns. The perspectives in this domain of initiation concern mainly the miniaturization and the hardening to the environments of electrical and optical components.

  13. 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.

  14. Grating cavity dual wavelength dye laser.

    PubMed

    Zapata-Nava, Oscar Javier; Rodríguez-Montero, Ponciano; Iturbe-Castillo, M David; Treviño-Palacios, Carlos Gerardo

    2011-02-14

    We report simultaneous dual wavelength dye laser emission using Littman-Metcalf and Littrow cavity configurations with minimum cavity elements. Dual wavelength operation is obtained by laser operation in two optical paths inside the cavity, one of which uses reflection in the circulating dye cell. Styryl 14 laser dye operating in the 910 nm to 960 nm was used in a 15%:85% PC/EG solvent green pumped with a Q-switched doubled Nd3+:YAG laser. PMID:21369171

  15. Dual-wavelength synchronous operation of a mode-locked 2-μm Tm:CaYAlO4 laser.

    PubMed

    Kong, L C; Qin, Z P; Xie, G Q; Xu, X D; Xu, J; Yuan, P; Qian, L J

    2015-02-01

    We experimentally demonstrated dual-wavelength synchronous operation of a high-power passively mode-locked 2-μm Tm:CaYAlO4 (Tm:CYA) disordered crystal laser with semiconductor saturable absorber mirror (SESAM) as mode locker. The mode-locked laser emitted an average output power as high as 830 mW with pulse duration of 35.3 ps and repetition rate of 145.4 MHz. The mode-locking dual wavelengths were centered at 1958.9 nm and 1960.6 nm, respectively. Autocorrelation trace clearly shows beating pulses with pulse width of 3.5 ps and repetition rate of 0.13 THz. PMID:25680046

  16. 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.

  17. Dual-wavelength synchronous mode-locked Yb:LSO laser using a double-walled carbon nanotube saturable absorber.

    PubMed

    Feng, Chao; Hou, Wei; Yang, Jimin; Liu, Jie; Zheng, Lihe; Su, Liangbi; Xu, Jun; Wang, Yonggang

    2016-05-01

    A dual-wavelength, passively mode-locked Yb:LSO laser was demonstrated using a double-walled carbon nanotube as a saturable absorber. The maximum average output power of the laser was 1.34 W at the incident pump power of 9.94 W. The two central wavelengths were 1057 and 1058 nm. The corresponding pulse duration of the autocorrelation interference pattern was about 15 ps, while the beat pulse repetition rate was 0.17 THz and the width of one beat pulse about 2 ps. When the incident pump power was above 10.25 W, a multiwavelength mode-locked oscillation phenomenon was observed. After employing a pair of SF10 prisms, a 1058.7 nm single-wavelength mode-locked laser was obtained with a pulse width of 7 ps. PMID:27140382

  18. Optical parametric oscillator of mid-IR, visible and UV ranges with synchronous pumping by a Q-switched mode-locked Nd : YAG laser

    NASA Astrophysics Data System (ADS)

    Donin, V. I.; Yakovin, M. D.; Yakovin, D. V.

    2016-07-01

    The parametric generation in a nonlinear PPLN crystal synchronously pumped by a Q-switched mode-locked Nd : YAG laser with a pulse duration of 45 ps is studied. The output pump intensity in the nonlinear crystal reaches ~10 GW cm-2. At a pulse repetition rate of 1 kHz, the average output power at the idler wavelength (~3.6 μm) is ~12 mW, the peak power is ~25 kW, and the conversion efficiency (with respect to the absorbed power) is ~10%. The radiation linewidth at the signal wavelength (~1.5 μm) is 13 cm-1. Along with the signal and idler waves, the output emission spectrum contains lines at wavelengths of 822, 754, 624, 532, 463, 442, 392 and 355 nm. The tunable radiation with wavelengths in the vicinity of 392, 463 and 822 nm is observed for the first time. The tuning ranges for the new lines are measured (5 – 10 nm) and their origin is explained.

  19. 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.

  20. Wavelength switchable graphene Q-switched fiber laser with cascaded fiber Bragg gratings

    NASA Astrophysics Data System (ADS)

    Wu, Man; Chen, Shuqing; Chen, Yu; Li, Ying

    2016-06-01

    We have demonstrated a wavelength switchable graphene Q-switched fiber laser with two cascaded fiber Bragg gratings. Stable Q-switching operation with central wavelength 1542.9 nm (1543.7 nm), repetition rate 28.4 kHz (22.58 kHz), and pulse duration 2.16 μs (2.65 μs) can be obtained by adjusting the intra-cavity birefringence. Moreover, stable dual-wavelength operation with wavelength spacing 0.8 nm can also be observed. The cascaded fiber gratings combined with the graphene saturable absorber provide a simple and feasible way to get versatile pulsed fiber laser.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. Simultaneous Dual-Wavelength Operation of Nd-Doped Yttrium Orthovanadate Self-Raman Laser at 1175 nm and Undoped Gadolinium Orthovanadate Raman Laser at 1174 nm

    NASA Astrophysics Data System (ADS)

    Shen, Hongbin; Wang, Qingpu; Zhang, Xingyu; Zhang, Lei; Zhang, Chu; Chen, Xiaohan; Cong, Zhenhua; Bai, Fen; Liu, Zhaojun

    2013-04-01

    A diode-pumped actively Q-switched Nd-doped yttrium orthovanadate self-Raman emission at 1175 nm and undoped gadolinium orthovanadate Raman emission at 1174 nm dual-wavelength laser is demonstrated. With the pump power of 20.5 W and pulse repetition frequency of 20 kHz, the maximum dual-wavelength output power of 1.52 W was obtained, which contained a 0.71 W 1174 nm Raman laser component and a 0.81 W 1175 nm self-Raman laser component. The corresponding dual-wavelength Raman pulse width was 14.8 ns. Experimental results indicated that the dual-wavelength Raman laser with a small wavelength separation was effectively realized through simultaneous self-Raman and Raman shift.

  6. Controllable Dual-Wavelength Fiber Laser

    NASA Astrophysics Data System (ADS)

    Li, Zhen; Zhou, Jun; He, Bing; Liu, Hou-Kang; Liu, Chi; Wei, Yun-Rong; Dong, Jing-Xing; Lou, Qi-Hong

    2012-07-01

    We demonstrate a controllable dual-wavelength fiber laser which contains a master laser and a slave laser. The master laser is a kind of ring cavity laser which can be injected into by the slave laser. The output laser wavelength is controlled by injected power of the slave laser; both single- and dual-wavelength operation can be achieved. Under free running, the master laser generates 1064 nm laser output. Here the slave laser is a 1072 nm fiber laser. The 1064 nm and 1072 nm laser coexist in output spectrum for relatively low injected power. Dual-wavelength and power-ratio-tunable operation can be achieved. If the injected power of the slave laser is high enough, the 1064 nm laser is extinguished automatically and there is only 1072 nm laser output.

  7. Dual-wavelength operation of continuous-wave and mode-locked erbium-doped fiber lasers

    NASA Astrophysics Data System (ADS)

    Pottiez, O.; Martinez-Rios, A.; Monzon-Hernandez, D.; Ibarra-Escamilla, B.; Kuzin, E. A.; Hernandez-Garcia, J. C.

    2012-06-01

    We study numerically and experimentally multiple-wavelength operation of an erbium-doped figure-eight fiber laser including a multiple-bandpass optical filter formed by two concatenated fiber tapers. Both continuous-wave and pulsed operations are considered. In the continuous-wave regime, stable long-term operation at multiple closely spaced wavelengths is only obtained if fine adjustments of the cavity losses are performed. Under these conditions, simultaneous lasing at up to four wavelengths separated by 1.5 nm was observed experimentally. Tunable single-wavelength operation over more than 20 nm is also observed in the continuous-wave regime. In the passive mode locking regime, numerical simulations indicate that mechanisms involving the filter losses and the nonlinear transmission characteristic of the NOLM contribute in principle to stabilize dual-wavelength operation, allowing less demanding cavity loss adjustments. In this regime, the problem of synchronization between the pulse trains generated at each wavelength adds an additional dimension to the problem. In presence of cavity dispersion, the pulses at each wavelength tend to be asynchronous if the wavelength separation is large, however they can be synchronous in the case of closely spaced wavelengths, if cross-phase modulation is able to compensate for the dispersion-induced walkoff. Experimentally, fundamental and 2nd-order harmonic mode locking was observed, characterized by the generation of noise-like pulses. Finally, a regime of multi-wavelength passive Q-switching was also observed. We believe that this work will be helpful to guide the design of multiple-wavelength fiber laser sources, which are attractive for a wide range of applications including Wavelength Division Multiplexing transmissions, signal processing and sensing.

  8. 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.

  9. Investigation of mechanically Q-switched lasers

    NASA Astrophysics Data System (ADS)

    Cole, Brian; Goldberg, Lew; Hough, Nathaniel; Nettleton, John

    2015-02-01

    Using a resonant scanner mirror Q-switch to provide a time varying change in cavity alignment, 1535nm lasers based on Er/Yb-doped glass and 1064nm lasers based on Nd:YAG were evaluated. Using a side pumping architecture, the Er/Yb glass laser used a compact mechanical Q-switch with a mirror rotation rate of 330 Rad/s, enabling generation of <3 mJ pulses with a pulse width of 16ns. The laser output was a diffraction limited TEM00 mode. A mechanical Q-switch based on a MEMS tilting mirror was also used; its performance in a laser cavity was found to be similar to the resonant mirror. The technique of mechanical Q-switching was also extended to a side pumped Nd:YAG laser (mirror sweep rate of 1300 Rad/s), enabling generation of Q-switched pulses of <30mJ and 25ns duration. The far-field divergence showed this laser to be highly multi-moded within the pump plane, with a measured beam-product-parameter greater than 30 mm-mRad.

  10. 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.

  11. 1.31 and 1.32 μm dual-wavelength Nd:LuLiF4 laser

    NASA Astrophysics Data System (ADS)

    Li, Shixia; Li, Tao; Zhao, Shengzhi; Li, Guiqiu; Hang, Yin; Zhang, Peixiong

    2016-07-01

    We demonstrate the operation of Nd:LuLiF4 laser with efficient 1.31 and 1.32 μm dual-wavelength. Maximum continuous-wave output power of 1.63 W is obtained at an incident pump power of 9.97 W and 8% transmission of output coupler (OC), giving a slope efficiency of 17.9%. When monolayer graphene is employed as saturable absorber, stable passively Q-switched 1.31 and 1.32 μm dual-wavelength laser operation still remains. The maximum average output power of 1.33 W, the largest pulse energy of 17.3 μJ and the highest peak power of 111.6 W are achieved with the 8% OC. Meanwhile, the shortest pulse duration of 133 ns and the highest repetition rate of 91 kHz are rendered by the 3.8% OC cavity.

  12. Graphene Q-switched, tunable fiber laser

    NASA Astrophysics Data System (ADS)

    Popa, D.; Sun, Z.; Hasan, T.; Torrisi, F.; Wang, F.; Ferrari, A. C.

    2011-02-01

    We demonstrate a wideband-tunable Q-switched fiber laser exploiting a graphene saturable absorber. We get ˜2 μs pulses, tunable between 1522 and 1555 nm with up to ˜40 nJ energy. This is a simple and low-cost light source for metrology, environmental sensing, and biomedical diagnostics.

  13. A random Q-switched fiber laser.

    PubMed

    Tang, Yulong; Xu, Jianqiu

    2015-01-01

    Extensive studies have been performed on random lasers in which multiple-scattering feedback is used to generate coherent emission. Q-switching and mode-locking are well-known routes for achieving high peak power output in conventional lasers. However, in random lasers, the ubiquitous random cavities that are formed by multiple scattering inhibit energy storage, making Q-switching impossible. In this paper, widespread Rayleigh scattering arising from the intrinsic micro-scale refractive-index irregularities of fiber cores is used to form random cavities along the fiber. The Q-factor of the cavity is rapidly increased by stimulated Brillouin scattering just after the spontaneous emission is enhanced by random cavity resonances, resulting in random Q-switched pulses with high brightness and high peak power. This report is the first observation of high-brightness random Q-switched laser emission and is expected to stimulate new areas of scientific research and applications, including encryption, remote three-dimensional random imaging and the simulation of stellar lasing. PMID:25797520

  14. 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…

  15. Electro-optic Q-switch driver design specifics

    NASA Astrophysics Data System (ADS)

    Melnikov, Konstantin

    2010-07-01

    Different schematic designs of Q-Switch Drivers for Pockels Cell based optical arrangement are considered. Schematic solutions of Q-Switch driver design are analyzed. Marx Bank based Generator and High Voltage Switch Schematics are compared. Parameters of constructed Q-Switch Drivers are presented.

  16. Electro-optic Q-switch driver design specifics

    NASA Astrophysics Data System (ADS)

    Melnikov, Konstantin

    2011-03-01

    Different schematic designs of Q-Switch Drivers for Pockels Cell based optical arrangement are considered. Schematic solutions of Q-Switch driver design are analyzed. Marx Bank based Generator and High Voltage Switch Schematics are compared. Parameters of constructed Q-Switch Drivers are presented.

  17. 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.

  18. 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.

  19. Circuit Stops Prelasing In A Q-Switched Laser

    NASA Technical Reports Server (NTRS)

    Lockard, George E.

    1995-01-01

    Protective shutdown circuit stops prelasing in Q-switched laser operating at pulse-repetition rate of about 10 Hz. During normal operation, Q-switch prevents emission of light from laser cavity during application of Q-switch-trigger pulse. When circuit detects prelasing, it triggers relay turning off laser power supply. Circuit integrated into almost any Q-switched-laser system, provided one gains access to laser light, Q-switch-trigger pulse, and safety-interlock line of laser power supply.

  20. 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.

  1. Spatial filter for Q-switched lasers

    NASA Technical Reports Server (NTRS)

    Wuerker, R. F.; Heflinger, L. O. (Inventor)

    1977-01-01

    A spatial filtered Q-switched laser system is reported that prevents ionization of air in close proximity to the aperture of the spatial filter. A compound lens system having an astigmatic focus is positioned between the laser and the spatial filter for defocusing the light beam emanating from the laser in the vicinity of the aperture of the spatial filter to an intensity below that which produces ionization of air. The preferred construction of the compound lens system as viewed from the laser comprises a cylindrical lens and a pair of positive lenses.

  2. Q-switched laser prelase detection circuit

    NASA Technical Reports Server (NTRS)

    Lockard, George E.

    1991-01-01

    A compact electronic circuit was developed to detect prelasing in Q-swithed pulsed laser systems and once detected to shut down the laser before the next laser pulse occurs. The circuit is small, compact, and uses a minimum of components which makes it quite economical, thus readily lending itself to commercial applications. It can easily be incorporated into virtually any Q-switched laser system or reliability of a laser system by reducing a source of possible costly optical damage. The circuit operation and instrument requirements necessary to incorporate the circuit into a laser system are discussed.

  3. Large repetitively Q-switched oscillators

    NASA Astrophysics Data System (ADS)

    Epstein, H. M.; Dulaney, J. L.; O'Loughlin, J. F.; Altman, W. P.

    A versatile waveform laser which can operate in bursts from 5 to 160 ms long and deliver up to 30 kJ power burst has been constructed. This Nd:glass laser system consists of four oscillators in parallel. Each oscillator can be varied in length from about 3 to 10 m, and contains two pump heads 670 mm long by 64 mm in diameter phosphate glass laser rods. When trains of Q-switched pulses are required, 70 mm diameter Pockels cells and dielectric polarizers are added to the oscillator cavity. The basic burst duration of 5 ms can be stretched to 10, 20, 40, 80,and 160 ms by sequencing the firing of flashlamps, with the longest pulse length attained by sequentially firing 1/4 heads. Trains of Q-switched pulses up to 10 kHz in repetition rate and 50 to 900 ns wide can be obtained by varying the cavity configuration and Pockels cell firing rate. Spatial distributions are flat-topped within about 10 percent. Overall efficiency for the oscillator with a CW waveform can exceed 4.8 percent.

  4. 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.

  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. 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.

  7. Generation of more than 40  W of average output power from a passively Q-switched Yb-doped fiber laser.

    PubMed

    Chakravarty, Usha; Kuruvilla, Antony; Singh, Ravindra; Upadhyaya, B N; Bindra, K S; Oak, S M

    2016-01-10

    We report on the generation of 41.6 W of average output power from a passively Q-switched ytterbium-doped fiber laser using Cr4+:YAG crystal as a saturable absorber (SA). This is the highest average power from passively Q-switched fiber lasers reported so far in the literature, to our knowledge, and it has been achieved by using a specially designed T-type double-end pumping configuration. Variation in average output power, pulse energy, pulse duration, pulse frequency, and pulse-to-pulse stability has also been studied using SAs of different linear transmissions. The effect of an intracavity SA on self-pulsing dynamics was also investigated and it was observed that, at lower input pump power near threshold, the presence of an SA enhances the peak power of relaxation oscillations to trigger the generation of stimulated Raman scattering in the gain fiber. With an increase in pump power, when the passive Q-switching threshold is reached, high peak power random self-pulses regenerate into low amplitude regular Q-switched pulses. The effect of the length of the gain medium on dual-wavelength generation at very low input pump power and broadband generation at sufficiently higher pump power has also been explored. PMID:26835764

  8. 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.

  9. Dual-Wavelength Internal-Optically-Pumped Semiconductor Laser Diodes

    NASA Astrophysics Data System (ADS)

    Green, Benjamin

    Dual-wavelength laser sources have various existing and potential applications in wavelength division multiplexing, differential techniques in spectroscopy for chemical sensing, multiple-wavelength interferometry, terahertz-wave generation, microelectromechanical systems, and microfluidic lab-on-chip systems. In the drive for ever smaller and increasingly mobile electronic devices, dual-wavelength coherent light output from a single semiconductor laser diode would enable further advances and deployment of these technologies. The output of conventional laser diodes is however limited to a single wavelength band with a few subsequent lasing modes depending on the device design. This thesis investigates a novel semiconductor laser device design with a single cavity waveguide capable of dual-wavelength laser output with large spectral separation. The novel dual-wavelength semiconductor laser diode uses two shorter- and longer-wavelength active regions that have separate electron and hole quasi-Fermi energy levels and carrier distributions. The shorter-wavelength active region is based on electrical injection as in conventional laser diodes, and the longer-wavelength active region is then pumped optically by the internal optical field of the shorter-wavelength laser mode, resulting in stable dual-wavelength laser emission at two different wavelengths quite far apart. Different designs of the device are studied using a theoretical model developed in this work to describe the internal optical pumping scheme. The carrier transport and separation of the quasi-Fermi distributions are then modeled using a software package that solves Poisson's equation and the continuity equations to simulate semiconductor devices. Three different designs are grown using molecular beam epitaxy, and broad-area-contact laser diodes are processed using conventional methods. The modeling and experimental results of the first generation design indicate that the optical confinement factor of the

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

    PubMed

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

    2013-12-01

    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. PMID:24514499

  11. Rate equations for ruby and alexandrite Q-switched lasers

    NASA Astrophysics Data System (ADS)

    Sulc, Jan; Jelinkova, Helena

    2003-07-01

    To have a complex view on giant pulse generation, a more precise computer model of the build up Q-switch pulse in solid-state laser was realized. As a time starting point of the rate equation calculation, the moment of a flashlamp trigger was chosen. A system of three or four main differential rate equations describes the energy transfer from a pumping source - capacitor to an output giant pulse. Two laser active media, i.e. ruby and alexandrite, were examined with this model. A passive Q-switch ruby laser needs solving of the system of four differential equations; three differential equations gave the computer results for electro-optically Q-switched alexandrite laser.

  12. Q-switching in the electron backward-wave oscillator

    SciTech Connect

    Denisov, G. G.; Kuzikov, S. V.; Savilov, A. V.

    2011-10-15

    The use of Q-switching (periodical modulation of the feedback factor) is proposed for the electron backward-wave oscillator (BWO). This can be a way to realize regimes of a stable generation of periodical short high-power rf pulses with relatively high averaged efficiency. As compared to the conventional regime of the stable generation of a BWO with no feedback, in the Q-switched BWO the averaged electronic efficiency can be increased by an order of magnitude, whereas the peak power of output rf pulses is 40-50 times higher.

  13. 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.

  14. Dual wavelength laser damage testing for high energy lasers.

    SciTech Connect

    Atherton, Briggs W.; Rambo, Patrick K.; Schwarz, Jens; Kimmel, Mark W.

    2010-05-01

    As high energy laser systems evolve towards higher energies, fundamental material properties such as the laser-induced damage threshold (LIDT) of the optics limit the overall system performance. The Z-Backlighter Laser Facility at Sandia National Laboratories uses a pair of such kiljoule-class Nd:Phosphate Glass lasers for x-ray radiography of high energy density physics events on the Z-Accelerator. These two systems, the Z-Beamlet system operating at 527nm/ 1ns and the Z-Petawatt system operating at 1054nm/ 0.5ps, can be combined for some experimental applications. In these scenarios, dichroic beam combining optics and subsequent dual wavelength high reflectors will see a high fluence from combined simultaneous laser exposure and may even see lingering effects when used for pump-probe configurations. Only recently have researchers begun to explore such concerns, looking at individual and simultaneous exposures of optics to 1064 and third harmonic 355nm light from Nd:YAG [1]. However, to our knowledge, measurements of simultaneous and delayed dual wavelength damage thresholds on such optics have not been performed for exposure to 1054nm and its second harmonic light, especially when the pulses are of disparate pulse duration. The Z-Backlighter Facility has an instrumented damage tester setup to examine the issues of laser-induced damage thresholds in a variety of such situations [2] . Using this damage tester, we have measured the LIDT of dual wavelength high reflectors at 1054nm/0.5ps and 532nm/7ns, separately and spatially combined, both co-temporal and delayed, with single and multiple exposures. We found that the LIDT of the sample at 1054nm/0.5ps can be significantly lowered, from 1.32J/cm{sup 2} damage fluence with 1054/0.5ps only to 1.05 J/cm{sup 2} with the simultaneous presence of 532nm/7ns laser light at a fluence of 8.1 J/cm{sup 2}. This reduction of LIDT of the sample at 1054nm/0.5ps continues as the fluence of 532nm/7ns laser light simultaneously

  15. 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.

  16. High-Power Single- and Dual-Wavelength Nd:GdVO4 Lasers with Potential Application for the Treatment of Telangiectasia

    NASA Astrophysics Data System (ADS)

    Chen, Lijuan; Wang, Zhengping; Yu, Haohai; Zhuang, Shidong; Han, Shuo; Zhao, Yongguang; Xu, Xinguang

    2012-11-01

    Diode-end-pumped high-power Nd:GdVO4 lasers at 1083 nm are presented. The maximum continuous-wave output power was 10.1 W with an optical conversion efficiency of 31.3%. For acoustooptic (AO) Q-switched operation, the largest pulse energy, shortest pulse width, and highest peak power were 111 µJ, 77 ns, and 1.44 kW, respectively. By decreasing the 1063 nm transmission of the output coupler, we also achieved efficient CW dual-wavelength operation at 1083 and 1063 nm. Their total output power reached 6.7 W, and the optical conversion efficiency reached 31.6%. These lasers have special requirements in the treatment of facial telangiectasia.

  17. 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. PMID:21263612

  18. 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.

  19. Simple technique for sequential Q-switching of molecular lasers.

    NASA Technical Reports Server (NTRS)

    Lucht, R. A.; Allario, F.; Jarrett, O., Jr.

    1972-01-01

    A simple technique for sequentially Q-switching molecular lasers is discussed in which an optical scanner is used as an optical folding element in a laser cavity consisting of a stationary diffraction grating and partially reflecting mirror. Sequential Q-switching of a conventional CO2 laser is demonstrated in which over sixty-two transitions between 9.2 and 10.8 microns are observed. Rapid repetition rates (200 Hz) and narrow laser pulses (less than 5 microsec) allow conventional signal processing techniques to be used with this multiwavelength laser source which is a versatile tool for laser propagation studies, absorption spectroscopy, and gain measurements. Results of a preliminary experiment demonstrating the utility of measuring selective absorption of CO2 laser wavelengths by C2H4 are shown.

  20. 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.

  1. 100-megawatt power Q-switched Er-glass laser

    NASA Astrophysics Data System (ADS)

    Taboada, John; Taboada, John M.; Stolarski, David J.; Zohner, Justin J.; Chavey, Lucas J.; Hodnett, Harvey M.; Noojin, Gary D.; Thomas, Robert J.; Kumru, Semih S.; Cain, Clarence P.

    2006-02-01

    A very high energy Q-switched Er-glass laser is reported. We incorporated a rotating, resonant mirror/Porro-cavity reflector optical arrangement to achieve very high shutter speeds on the cavity Q of a laser designed for energetic, flashlamp-pumped, 600-μs, 1540-nm pulses. Reproducible 3.75-J, 35-ns, 1533-nm laser pulses were obtained at a repetition rate less than 1 minute. Our work shows that reliable, very high energy, Q-switched, Er-glass laser pulses at 1533 nm can be generated mechanically with no apparent damage to laser cavity components. We demonstrate the applications of this "eye safe" wavelength to energetic processes such as LIBS and materials processing. The laser could also serve as a new tool for bioeffects studies and targeting applications.

  2. Real-time dual wavelength polarimetry for glucose sensing

    NASA Astrophysics Data System (ADS)

    Malik, Bilal H.; Coté, Gerard L.

    2009-02-01

    Proper treatment of diabetes includes maintenance of near normal blood glucose levels, which can only be achieved with frequent blood glucose monitoring. Current blood finger-stick methods for glucose sensing are invasive, often resulting in low patient compliance and poor disease control. The development of a noninvasive glucose sensor has the potential to provide optimal management of diabetes. Our proposed noninvasive approach is based on an optical polarimetry system for probing the anterior chamber of the eye. The sensor would eventually be used to measure the aqueous humor glucose concentration as a means to determine the blood glucose concentration. In this report, we present the development of a near real-time (less than 1 second) dual wavelength closed-loop polarimetric system to minimize glucose prediction error in the presence of varying birefringence due to motion artifact. The new dual wavelength polarimetric system and in vitro glucose measurement results will be presented which demonstrate the sensitivity and accuracy of the system in the presence of varying birefringence.

  3. Characterizing dual wavelength polarimetry through the eye for monitoring glucose

    PubMed Central

    Malik, Bilal H.; Coté, Gerard L.

    2010-01-01

    Diabetes is an insidious disease that afflicts millions of people worldwide and typically requires the person with the disease to monitor their blood sugar level via finger or forearm sticks multiple times daily. Therefore, the ability to noninvasively measure glucose would be a significant advancement for the diabetic community. The use of optically polarized light passed through the anterior chamber of the eye is one proposed noninvasive approach for glucose monitoring. However, the birefringence of the cornea and the difficulty in coupling the light across the eye have been major drawbacks toward realizing this approach. A dual wavelength optical polarimetric approach has been proposed as a means to potentially overcome the birefringence noise but has never been fully characterized. Therefore, in this paper an optical model has been developed along with experiments performed on New Zealand White rabbit eyes for characterizing the light path and corneal birefringence at two different wavelengths as they are passed through the anterior chamber of the eye. The results show that, without index matching, it is possible to couple the light in and out of the eye but only across a very limited range otherwise the light does not come back out of the eye. It was also shown that there is potential to use a dual wavelength approach to accommodate the birefringence noise of the cornea in the presence of eye motion. These results will be used to help guide the final design of the polarimetric system for use in noninvasive monitoring of glucose in vivo. PMID:21258546

  4. 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

  5. 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.

  6. Dual-wavelength laser source for onboard atom interferometry.

    PubMed

    Ménoret, V; Geiger, R; Stern, G; Zahzam, N; Battelier, B; Bresson, A; Landragin, A; Bouyer, P

    2011-11-01

    We present a compact and stable dual-wavelength laser source for onboard atom interferometry with two different atomic species. It is based on frequency-doubled telecom lasers locked on a femtosecond optical frequency comb. We take advantage of the maturity of fiber telecom technology to reduce the number of free-space optical components, which are intrinsically less stable, and to make the setup immune to vibrations and thermal fluctuations. The source provides the frequency agility and phase stability required for atom interferometry and can easily be adapted to other cold atom experiments. We have shown its robustness by achieving the first dual-species K-Rb magneto-optical trap in microgravity during parabolic flights. PMID:22048340

  7. Dual-Wavelength Sensitized Photopolymer for Holographic Data Storage

    NASA Astrophysics Data System (ADS)

    Tao, Shiquan; Zhao, Yuxia; Wan, Yuhong; Zhai, Qianli; Liu, Pengfei; Wang, Dayong; Wu, Feipeng

    2010-08-01

    Novel photopolymers for holographic storage were investigated by combining acrylate monomers and/or vinyl monomers as recording media and liquid epoxy resins plus an amine harder as binder. In order to improve the holographic performances of the material at blue-green wavelength band two novel dyes were used as sensitizer. The methods of evaluating the holographic performances of the material, including the shrinkage and noise characteristics, are described in detail. Preliminary experiments show that samples with optimized composite have good holographic performances, and it is possible to record dual-wavelength hologram simultaneously in this photopolymer by sharing the same optical system, thus the storage density and data rate can be doubly increased.

  8. Terahertz ambipolar dual-wavelength quantum cascade laser.

    PubMed

    Lever, L; Hinchcliffe, N M; Khanna, S P; Dean, P; Ikonic, Z; Evans, C A; Davies, A G; Harrison, P; Linfield, E H; Kelsall, R W

    2009-10-26

    Terahertz frequency quantum cascade lasers (THz QCLs) are compact solid-state sources of terahertz radiation that were first demonstrated in 2002. They have a broad range of potential applications ranging from gas sensing and non-destructive testing, through to security and medical imaging, with many polycrystalline compounds having distinct fingerprint spectra in the terahertz frequency range. In this article, we demonstrate an electrically-switchable dual-wavelength THz QCL which will enable spectroscopic information to be obtained within a THz QCL-based imaging system. The device uses the same active region for both emission wavelengths: in forward bias, the laser emits at 2.3 THz; in reverse bias, it emits at 4 THz. The corresponding threshold current densities are 490 A/cm(2) and 330 A/cm(2), respectively, with maximum operating temperatures of 98K and 120 K. PMID:19997216

  9. Stable dual-wavelength erbium fiber laser for temperature measurements

    NASA Astrophysics Data System (ADS)

    Diaz, S.; Lopez-Amo, M.

    2015-09-01

    In this work, a new stable dual-wavelength erbium fiber ring laser is proposed and experimentally demonstrated. This configuration is made by creating two symmetrical laser cavities with similar optical power. This topology allows the performance of two laser emission lines in single-longitudinal mode and with a power instability lower than 0.23 dB, and an optical signal-to-noise ratio higher than 40 dB for all the emitted wavelengths. The sensing capability of the FBGs enables this source to be also used as sensor-network multiplexing scheme. The system offers a better stability and higher optical signal to noise ratios than similar configurations.

  10. Observations of Florida Convective Storms using Dual Wavelength Airborne Radar

    NASA Technical Reports Server (NTRS)

    Heymsfield, G. M.; Heymsfield, A. J.; Belcher, L.

    2004-01-01

    NASA conducted the Cirrus Regional Study of Tropical Anvils and Cirrus Layers (CRYSTAL) Florida Area Cirrus Experiment (FACE) during July 2002 for improved understanding of tropical cirrus. One of the goals was to improve the understanding of cirrus generation by convective updrafts. The reasons why some convective storms produce extensive cirrus anvils is only partially related to convective instability and the vertical transport ice mass by updrafts. Convective microphysics must also have an important role on cirrus generation, for example, there are hypotheses that homogeneous nucleation in convective updrafts is a major source of anvil ice particles. In this paper, we report on one intense CRYSTAL-FACE convective case on 16 July 2002 that produced extensive anvil. During CRYSTAL-FACE, up to 5 aircraft flying from low- to high-altitudes, were coordinated for the study of thunderstorm-generated cirrus. The NASA high-altitude (20 km) ER-2 aircraft with remote sensing objectives flew above the convection, and other aircraft such as the WB-57 performing in situ measurements flew below the ER-2. The ER-2 remote sensing instruments included two nadir viewing airborne radars. The CRS 94 GHz radar and the EDOP 9.6 GHz radar were flown together for the first time during CRYSTAL-FACE and they provided a unique opportunity to examine the structure of 16 July case from a dual-wavelength perspective. EDOP and CRS are complementary for studying convection and cirrus since CRS is more sensitive than EDOP for cirrus, and EDOP is considerably less attenuating in convective regions. In addition to the aircraft, coordinated ground-based radar measurements were taken with the NPOL S-Band (3 GHz) multiparameter radar. One of the initial goals was to determine whether dual-wavelength airborne measurements could identify supercooled water regions.

  11. 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.

  12. Monolithic passively Q-switched Cr:Nd:GSGG microlaser

    NASA Astrophysics Data System (ADS)

    Schmitt, Randal L.

    2005-09-01

    Optical firing sets need miniature, robust, reliable pulsed laser sources for a variety of triggering functions. In many cases, these lasers must withstand high transient radiation environments. In this paper we describe a monolithic passively Q-switched microlaser constructed using Cr:Nd:GSGG as the gain material and Cr4+:YAG as the saturable absorber, both of which are radiation hard crystals. This laser consists of a 1-mm-long piece of undoped YAG, a 7-mm-long piece of Cr:Nd:GSGG, and a 1.5-mm-long piece of Cr4+:YAG diffusion bonded together. The ends of the assembly are polished flat and parallel and dielectric mirrors are coated directly on the ends to form a compact, rugged, monolithic laser. When end pumped with a diode laser emitting at ~807.6 nm, this passively Q-switched laser produces ~1.5-ns-wide pulses. While the unpumped flat-flat cavity is geometrically unstable, thermal lensing and gain guiding produce a stable cavity with a TEM00 gaussian output beam over a wide range of operating parameters. The output energy of the laser is scalable and dependent on the cross sectional area of the pump beam. This laser has produced Q-switched output energies from several μJ per pulse to several 100 μJ per pulse with excellent beam quality. Its short pulse length and good beam quality result in high peak power density required for many applications such as optically triggering sprytrons. In this paper we discuss the design, construction, and characterization of this monolithic laser as well as energy scaling of the laser up to several 100 μJ per pulse.

  13. 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.

  14. Effects of axial nonuniformity in modeling Q-switched lasers

    SciTech Connect

    Stone, D.H. )

    1992-10-01

    Generic Q-switched laser pulses are calculated using a point model and a traveling wave model. Results indicate that the point model approach commonly used in rate equation modeling is inadequate for large initial inversions, large internal losses, or large fractional outcoupling. The point model typically overestimates peak power and energy and distorts the pulse shape. A simple traveling wave model is developed which easily describes these cases. The optimum outcoupling to maximize peak power varies significantly between the two models. 9 refs.

  15. 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.

  16. 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.

  17. 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).

  18. Quantum cascade lasers with dual-wavelength interdigitated cascades

    NASA Astrophysics Data System (ADS)

    Mosely, Trinesha S.; Straub, Axel; Gmachl, Claire; Colombelli, Raffaele; Troccoli, Mariano; Capasso, Federico; Sivco, Deborah L.; Cho, Alfred Y.

    2002-03-01

    A quantum cascade (QC) laser with a dual-wavelength interdigitated cascade is presented. Its active core consists of a stack of active regions and injectors designed for emission at one wavelength (8.0 μm) interleaved with a second stack emitting at a substantially different wavelength (9.5 μm), and the two injectors were designed to either bridge the 8.0 μm active region to the 9.5 μm one, or vice versa. Clear two-wavelength laser action is observed, demonstrating the viability of this approach to achieve multi-wavelength laser emission in the mid-infrared. Aside from providing two-wavelength operation, this laser design can also be used to test the role of charge transport in the injectors, which customarily bridge successive active regions together. We will present early results of this study. The work was partly supported by DARPA/US ARO under contract number DAAD19-00-C-0096. A. S. acknowledges the support of the Deutsche Studienstiftung. T. S. M. present address: Southern University and A&M College, Baton Rouge, LA.

  19. 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.

  20. Smart Q-switching for single-pulse generation in an erbium-doped fiber laser.

    PubMed

    Escalante-Zarate, Luis; Barmenkov, Yuri O; Kolpakov, Stanislav A; Cruz, José L; Andrés, Miguel V

    2012-02-13

    In this paper, we report an active Q-switching of an erbium-doped fiber laser with special modulation functions and novel laser geometry. We experimentally demonstrate that using such a smart Q-switch approach, Q-switch ripple-free pulses with Gaussian-like shape and 17.3 ns width can be easily obtained. The idea behind the smart Q-switch is to suppress one of two laser waves contra-propagating along the fiber cavity, which arises after Q-cell opening, and to eliminate the minor sub-pulses. PMID:22418199

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. Dual-wavelength microarray fluorescence detection system using volume holographic filter.

    PubMed

    Fu, Dongxiang; Ma, Junshan; Chen, Jiabi

    2007-01-01

    A dual-wavelength microarray scanner based on laser confocal principle is constructed to acquire the laser-induced two-color fluorescence from dyes Cy3 and Cy5. Unlike most commercially available micoarray scanners whose lasers are continuous wave, filters are bandpass and the channels are multiple photomultiplier tubes (PMTs), the system mainly consists of two diode lasers, four volume holographic band-stop filters, and one PMT. The central wavelengths of two kinds of volume holographic band-stop filters are equal to those of the two laser, respectively. The fluorescence beams can pass through the filters, while laser beams are blocked by them because the filters are cut off. The two fluorescences can pass through a common optical path. Thus, only one pinhole and one PMT are required. The two fluorescences are acquired by the PMT with time sharing. The two respective fluorescences can be gathered when two diode lasers work asynchronously. If lasers work synchronously, the two wavelength fluorescences could be acquired simultaneously by the same PMT. A synthesis of a two-color fluorescence image can be realized straightforwardly in this manner. An experiment is conducted and Cy3 and Cy5 fluorescences are captured. Gridding of the fluorescent images based on basic morphological erosion appropriately locates the boundary between adjacent spots. PMID:17343515

  6. Shifted excitation Raman difference spectroscopy using a dual-wavelength DBR diode laser at 785 nm

    NASA Astrophysics Data System (ADS)

    Maiwald, M.; Eppich, B.; Fricke, J.; Ginolas, A.; Bugge, F.; Klehr, A.; Sumpf, B.; Erbert, G.; Tränkle, G.

    2015-03-01

    The application of shifted excitation Raman difference spectroscopy (SERDS) using a dual wavelength distributed Bragg reflector (DBR) diode laser at 785 nm will be presented. Both excitation wavelengths necessary for SERDS provide an optical power of more than 160 mW in continuous wave operation. Raman experiments are carried out and demonstrate the suitability of the excitation light source for SERDS. Moreover, a dual-wavelength master-oscillator power amplifier diode laser system is presented. The diode laser system reaches optical powers larger 750 mW while the spectral properties of the dual-wavelength laser remain unchanged.

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

    NASA Technical Reports Server (NTRS)

    Lockard, George E. (Inventor)

    1994-01-01

    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.

  8. Q-switched fiber laser based on an acousto-optic modulator with injection seeding technique.

    PubMed

    Li, Wencai; Liu, Haowei; Zhang, Ji; Long, Hu; Feng, Sujuan; Mao, Qinghe

    2016-06-10

    The operation mechanism and the pulse property of an actively Q-switched erbium-doped fiber laser based on an acousto-optic modulator (AOM) switch with the injection seeding technique are investigated. Our results show that the Q-switched pulses can be locked to oscillate near a fixed frequency higher than that of the seed laser, though the frequency-shift effect of the AOM impedes stable cavity mode oscillations. The operation mechanism of such Q-switch fiber lasers can be explained by the mutual locking-in among the shifted frequency components originated from the injected coherence seed with the help of the gain dynamics of the Q-switch cavity. Moreover, narrow-linewidth Q-switched pulses with different repetition rates can be obtained with different cavity lengths for incredibly stable output pulses without any use of cavity-stabilized techniques. PMID:27409015

  9. 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.

  10. 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.

  11. 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.

  12. High-power terahertz optical pulse generation with a dual-wavelength harmonically mode-locked Yb:YAG laser

    NASA Astrophysics Data System (ADS)

    Zhuang, W. Z.; Chang, M. T.; Su, K. W.; Huang, K. F.; Chen, Y. F.

    2013-07-01

    We report on high-power terahertz optical pulse generation with a dual-wavelength harmonically mode-locked Yb:YAG laser. A semiconductor saturable absorber mirror is developed to achieve synchronously mode-locked operation at two spectral bands centered at 1031.67 and 1049.42 nm with a pulse duration of 1.54 ps and a pulse repetition rate of 80.3 GHz. With a diamond heat spreader to improve the heat removal efficiency, the average output power can be up to 1.1 W at an absorbed pump power of 5.18 W. The autocorrelation traces reveal that the mode-locked pulse is modulated with a beat frequency of 4.92 THz and displays a modulation depth to be greater than 80%.

  13. 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

  14. Synchronization

    NASA Astrophysics Data System (ADS)

    Pikovsky, Arkady; Rosenblum, Michael; Kurths, Jürgen

    2003-04-01

    Preface; 1. Introduction; Part I. Synchronization Without Formulae: 2. Basic notions: the self-sustained oscillator and its phase; 3. Synchronization of a periodic oscillator by external force; 4. Synchronization of two and many oscillators; 5. Synchronization of chaotic systems; 6. Detecting synchronization in experiments; Part II. Phase Locking and Frequency Entrainment: 7. Synchronization of periodic oscillators by periodic external action; 8. Mutual synchronization of two interacting periodic oscillators; 9. Synchronization in the presence of noise; 10. Phase synchronization of chaotic systems; 11. Synchronization in oscillatory media; 12. Populations of globally coupled oscillators; Part III. Synchronization of Chaotic Systems: 13. Complete synchronization I: basic concepts; 14. Complete synchronization II: generalizations and complex systems; 15. Synchronization of complex dynamics by external forces; Appendix 1. Discovery of synchronization by Christiaan Huygens; Appendix 2. Instantaneous phase and frequency of a signal; References; Index.

  15. 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.

  16. Short-pulse actively Q-switched Er:YAG lasers.

    PubMed

    Ottaway, David J; Harris, Lachlan; Veitch, Peter J

    2016-07-11

    We report the shortest duration pulses obtained to date from an actively Q-switched Er:YAG laser pumped by a low spectral and spatial brightness laser diode. The 14.5 ns, 6 mJ pulses were obtained using a 1470 nm laser diode end-pumped co-planar folded zigzag slab architecture. We also present an analytical model that accurately predicts the pulse energy-duration product achievable from virtually all Q-switched Er:YAG lasers and high repetition rate quasi-three-level Q-switched lasers in general. PMID:27410810

  17. 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.

  18. 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.

  19. 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%.

  20. 1357 nm passively Q-switched crystalline ceramic laser based on multilayer graphene

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

    1357 nm single wavelength passively Q-switched Nd:YAG ceramic lasers are demonstrated with a multilayer graphene sheets saturable absorber (SA). During an increase in the incident pump power, the laser exhibited stable Q-switched oscillation, which showed that our graphene SA provided Q-switched modulation successfully. The maximum average output power was 340 mW, and the corresponding pulse width, pulse repetition rate, single pulse energy and peak power were 380 ns, 209 kHz, 53 μJ and 139 W, respectively. Our results illustrate that graphene can be used as an SA for 1357 nm passively Q-switched Nd:YAG ceramic lasers.

  1. Treatment of large bulla formation after tattoo removal with a q-switched laser.

    PubMed

    Kirby, William; Kartono, Francisca; Desai, Alpesh; Kaur, Ravneet R; Desai, Tejas

    2010-01-01

    Widely considered the gold standard treatment option for tattoo removal, the use of Q-switched lasers may very rarely result in the formation of large bulla. While very disconcerting to patients, these lesions are easily managed and, with proper care, heal quickly with no long-term consequences. The authors present three cases of patients who had bullous reactions shortly after receiving Q-switched laser treatment of tattoo ink. Bullous formation in all three patients was treated successfully. PMID:20725537

  2. Optical performance of Ho:YLF Q-switched Tm:YAG laser system

    NASA Astrophysics Data System (ADS)

    Chang, Yi-An; Kuo, Yen-Kuang

    2002-09-01

    The absorption cross-section of the Ho:YLF crystal is close to the emission cross-section of the Tm:YAG laser. According to the passive Q-switching theory, a giant laser pulse cannot be generated from the Ho:YLF Q-switched Tm:YAG laser system unless an internal focusing lens is utilized. In a previous work we experimentally demonstrated that passive Q-switching of the 2017-nm, flashlamp pumped Tm,Cr:YAG laser with a Ho:YLF saturable absorber could be obtained with an internal focusing lens. In this paper, we theoretically investigate the optical performance of the Ho:YLF Q-switched Tm:YAG laser system by solving the coupled rate equations. The simulation results indicate that the results obtained numerically are in good agreement with that obtained experimentally. Moreover, we study the passive Q-switching performance of the Ho:YLF Q-switched Tm:YAG laser system as functions of the reflectivity of the output coupler, the initial population of the saturable absorber ground state, the laser pumping rate, and the loss inside the laser resonator. On the other hand, assuming that a polarizer is utilized inside the laser cavity, we explore the passive Q-switching performance of the Ho:YLF Q-switched Tm:YAG laser system when the polarization of the laser light is along different direction between the two saturable absorber principal axes. Effect of the relative position between the saturable absorber and the output coupler is also investigated.

  3. Research on dual-wavelength photometric method for micro liquid volume measurement

    NASA Astrophysics Data System (ADS)

    Wang, Jintao; Liu, Ziyong; Tong, Lin

    2015-02-01

    In order to overcome the shortcoming of significant influence of evaporation capacity on gravimetric method and meet the requirement of online measurement, dual-wavelength photometric method is introduced for measuring microliquid volume. Based on Lambert-Beer law, this paper introduces the dual-wavelength photometric method (DWP method) at 520 nm and 730 nm, which can measure the microliquid volume through the linear relation between the concentration of dilute solution and the absorbance. Comparing to gravimetric method, an experimental system for dual-wavelength photometric method was designed. Experimental results indicate that the test result obtained by using DWP method was better than obtained by using gravimetric method, and met the technical requirement of ISO 8655. Compared with the gravimetric method, the non-gravimetric methods can provide a better solution for microliquid volume measurement, which was less stringent for measurement environment, easy to realize the online calibration and capable of reducing the influence of liquid evaporation.

  4. Stable dual-wavelength laser combined with gain flattening ML-FMF Bragg grating filter

    NASA Astrophysics Data System (ADS)

    Liang, Xiao; Li, Yang; Bai, Yunlong; Yin, Bin; Liu, Zhibo; Jian, Shuisheng

    2016-01-01

    A stable dual-wavelength laser combined with gain flattening multi-layer few-mode fiber Bragg grating filter was proposed and experimentally demonstrated. The index profile of the multi-layer few-mode fiber was particularly designed to support LP01 and LP11 modes with approximately equal excitation coefficients. And conventional phase-mask fabrication technique was used to inscribe Bragg gratings in the multi-layer few-mode fiber core, which leads to the gain flattening filter. A switchable dual-wavelength laser combined with the gain flattening filter was successfully achieved with simple linear configuration. The lasing wavelengths spacing was 0.39 nm. The variation of the central wavelength and intensity fluctuation were as small as 0.01 nm and <0.7 dBm in both dual-wavelength and single-wavelength operation regions, respectively.

  5. Short monolithic dual-wavelength single-longitudinal-mode DBR phosphate fiber laser.

    PubMed

    Xiong, Lingyun; Hofmann, Peter; Schülzgen, Axel; Peyghambarian, N; Albert, Jacques

    2014-06-20

    We propose and demonstrate a 5-cm-long monolithic dual-wavelength single-longitudinal mode distributed Bragg reflector (DBR) all-phosphate fiber laser. Strong UV-induced fiber Bragg gratings are directly written in highly Er/Yb codoped phosphate fiber. The separation between gratings is selected as 1 cm to only excite two longitudinal modes in the DBR cavity. By exploiting the spatial hole burning effect and the polarization hole burning effect, stable narrow-linewidth dual-wavelength lasing emission with 38 pm wavelength spacing and a total emitted power of 2.8 mW is obtained from this DBR fiber laser. A microwave signal at 4.58 GHz is generated by the heterodyne detection of the dual-wavelength laser. PMID:24979414

  6. 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

  7. Dual-wavelength fluorescent detection of particles on a novel microfluidic chip.

    PubMed

    Jiang, Hai; Weng, Xuan; Li, Dongqing

    2013-03-01

    This paper reports a novel lab-on-a-chip device that performs fluorescent particle counting by coupling the electrokinetically-induced pressure-driven flow and a miniaturized dual-wavelength fluorescent detection method. A novel L-shaped PDMS microchannel bonded on a thin glass slide is used to transport the particles. The dual-wavelength fluorescent detection system can count two different fluorescent particles simultaneously. Good agreement is achieved between the results obtained by the microfluidic chip device and the results from a commercial flow cytometer. PMID:23291857

  8. Simultaneous dual-wavelength oscillation at 1116 and 1123 nm of Nd:YAG laser

    NASA Astrophysics Data System (ADS)

    Li, C. Y.; Bo, Y.; Xu, J. L.; Tian, C. Y.; Peng, Q. J.; Cui, D. F.; Xu, Z. Y.

    2011-09-01

    We report on to our knowledge the first time a diode-side-pumped simultaneous dual-wavelength Nd:YAG laser at 1116 and 1123 nm. By inserting an etalon to balance the gain and loss, a stable dual-wavelength oscillation is acquired. The numerical simulations for wavelength tuning are discussed by principles of laser threshold and Fabry-Perot etalon. Under the pump power of 250 W, a total output power of 23 W is obtained. Meanwhile, the two components have approximately equal intensities. The beam quality of M 2 factor was measured to be 7.52.

  9. Using Dual-wavelength Fiber Bragg Gratings for Temperature and Strain Sensing at Cryogenic Temperature

    NASA Technical Reports Server (NTRS)

    Wu, Meng-Chou; Prosser, William H.; Rogowski, Robert S.; DeHaven, Stanton L.

    2003-01-01

    By using dual-wavelength fiber-optic Bragg gratings, a new technique has been developed for sensing both temperature and strain simultaneously in cryogenic temperature range. Two Bragg gratings with different wavelengths were inscribed at the same location in an optical fiber to form a dual-wavelength sensor. By measuring the wavelength shifts that resulted from the fiber being subjected to different temperatures and strains, the wavelength-dependent thermo-optic coefficients and photoelastic coefficients of the fiber were determined. These coefficients were used to construct the elements of the K matrix, which enables to determine inversely the strain and temperature changes by measuring the wavelength shifts of the dual-wavelength Bragg grating. In this study, measurements were made over the temperature range from room temperature down to about 10 K, addressing much of the low temperature range of cryogenic tanks. A structure transition of the optical fiber during the temperature change was found from about 70 K to 140 K. This transition caused splitting of the waveforms characterizing the Bragg gratings, and the determination of wavelength shifts was consequently complicated. Several alternatives are proposed to resolve this problem. The effectiveness and sensitivities of these measurements in different temperature ranges are discussed. The separation of two wavelengths for the dual-wavelength Bragg grating has been widened to increase the sensitivities of measurement; however, this separation can still be covered in the scanning range from single scanning laser.

  10. 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.

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

    NASA Astrophysics Data System (ADS)

    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.

  12. Q-switched laser in an SMS cavity for inhibiting nonlinear effects.

    PubMed

    Zhou, Jiaqi; Lu, Yi; He, Bing; Gu, Xijia

    2015-07-01

    In the design of high-power Q-switched fiber lasers, nonlinear effects often become barriers that prevent the scale up of pulse energy and peak power. New designs and components that could inhibit or suppress nonlinear effects are in high demand, particularly in all-fiber configurations. In this paper, we demonstrated a Q-switched Yb-doped fiber laser in a single-mode multimode single-mode (SMS) structure to inhibit fiber nonlinear effects. The laser-generated Q-switched pulses with a peak power close to 1 kW (pulse width and energy of 100 ns and 92 μJ, respectively). The output spectrum of this laser was compared with that of a Q-switched Yb-doped fiber laser built in a conventional configuration with similar output peak power. The results showed, for the first time to our knowledge, that the SMS Q-switched laser completely inhibited the stimulated Raman scattering and significantly reduced self-phase modulation. PMID:26193155

  13. The effect of the depth of single longitudinal mode modulation in Q-switching pre-Pr3+:YLF laser

    NASA Astrophysics Data System (ADS)

    Qing-Song, Li; Ling-Xi, Zhu; Xi-He, Zhang; Yuan, Dong; Yong-Ji, Yu; Guang-Yong, Jin

    2016-08-01

    The single longitudinal mode (SLM) can be obtained under the condition of Q-switching pre-lase. In this paper, the model of Q-switching pre-lase is firstly established. Taking the Pr3+:YLF laser as an example, the process of Q-switching pre-lase is simulated and optimized, then the optimized parameters and best output characteristics under different depth of SLM modulation are obtained. Comparing with the normal Q-switching laser, the SLM pulse energy can reach to 79.29%, the pulse width exceeds 16.45% and the depth of SLM modulation get to be 20. The results show that the Q-switching pre-lase output characteristics can be effected obviously by the SLM modulation depth, and the pulse energy and pulse width can be close to the normal Q-switching laser as long as the depth of SLM modulation is optimized.

  14. LASERS: Small autonomous passively Q-switched Nd3+:YAG laser with a Cr4+:YAG Q switch emitting pulse trains

    NASA Astrophysics Data System (ADS)

    Buzinov, N. M.; Dmitriev, Valentin G.; Zabavin, V. N.; Kazakov, A. A.; Maslov, A. A.; Spitsyn, E. M.

    2007-04-01

    The energy and time characteristics of a passively Q-switched Nd3+:YAG laser with a Cr4+:YAG Q switch emitting pulse trains are studied and analysed theoretically. The description and technical parameters of a small autonomous laser with intracavity second-harmonic generation (ICSHG) in the pulse-train regime are presented. The laser provides a high total pulse-train energy for a relatively low peak power of a single pulse, stable operation in a wide temperature range, and has a small weight and size, which is convenient in operation. The enhanced reliability and stability of the laser operation are provided by its original technical design: the ICSHG scheme for type II phase matching without polarisers, the use of temperature-noncritical phase matching in KTP crystals, dust- and moisture-proof casing, and battery-operated pulsed power supply for the pump flashlamp.

  15. Gold nanoparticles as a saturable absorber for visible 635 nm Q-switched pulse generation.

    PubMed

    Wu, Duanduan; Peng, Jian; Cai, Zhiping; Weng, Jian; Luo, Zhengqian; Chen, Nan; Xu, Huiying

    2015-09-01

    Gold nanoparticle (GNP) possesses saturable absorption bands in the visible region induced by surface plasmon resonance (SPR). We firstly applied the GNP as a visible saturable absorber (SA) for the red Q-switched pulse generation. The GNPs were embedded in polyvinyl alcohol (PVA) for film-forming and inserted into a praseodymium (Pr(3+))-doped fiber laser cavity to achieve 635 nm passive Q-switching. The visible 635 nm Q-switched fiber laser has a wide range of pulse-repetition-rate from 285.7 to 546.4 kHz, and a narrow pulse width of 235 ns as well as the maximum output power of 11.1 mW. The results indicate that the GNPs-based SA is available for pulsed operation in the visible spectral range. PMID:26368498

  16. 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.

  17. 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.

  18. 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.

  19. 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. PMID:19756079

  20. 980-nm Q-switched photonic crystal fiber laser by MoS2 saturable absorber

    NASA Astrophysics Data System (ADS)

    Li, Pingxue; Liang, Boxing; Su, Meng; Zhang, Yuefei; Zhao, Yan; Zhang, Mengmeng; Ma, Chunmei; Su, Ning

    2016-05-01

    We demonstrate a 980-nm Q-switch Yb-doped photonic crystal fiber laser by a multilayer molybdenum sulfide polymer composite as the broadband saturable absorber which is prepared by the chemical vapor deposition method. We achieve passively Q-switching operations at 978 nm with the pulse width of 2.7 and 0.63 μs, corresponding to the repetition rate of 212 and 221 kHz, respectively. The maximum output power is 127 mW. It is the first time that MoS2 Q-switched Yb-doped photonic crystal fiber laser at 980 nm is demonstrated. The experimental results show that few-layer MoS2 is a promising broadband saturable absorber material.

  1. 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.

  2. 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.

  3. Active Q switching of a fiber laser with a microsphere resonator.

    PubMed

    Kieu, Khanh; Mansuripur, Masud

    2006-12-15

    We propose and demonstrate an active Q-switched fiber laser using a high-Q microsphere resonator as the Q-switching element. The laser cavity consists of an Er-doped fiber as the gain medium, a glass microsphere reflector (coupled through a fiber taper) at one end of the cavity, and a fiber Bragg grating reflector at the other end. The reflectivity of the microsphere is modulated by changing the gap between the microsphere and the fiber taper. Active Q switching is realized by oscillating the microsphere in and out of contact with the taper. Using this novel technique, we have obtained giant pulses (maximum peak power approximately 102 W, duration approximately 160 ns) at a low pump-power threshold (approximately 3 mW). PMID:17130905

  4. 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. PMID:25679830

  5. Er/Yb glass laser with compact mechanical Q-switch

    NASA Astrophysics Data System (ADS)

    Cole, Brian; Hough, Nathaniel; Hays, Alan; Nettleton, John; Goldberg, Lew

    2016-03-01

    We describe a compact, side-pumped, Er/Yb glass laser with a low cost mechanical Q-switch. The Q-switch uses a mirror or reflecting prism mounted on a cantilever resonant spring that is driven by a small electromagnetic coil. The demonstrated laser used a 5 mm long Er/Yb glass gain element, and was side-pumped by a 940 nm, 5 mm wide diode bar generating up to 100 W peak power. Target energies of 3mJ have been realized in a near-diffraction limited mode, with pulse widths of 15-25ns, and an optical-to-optical efficiency of greater than 2%. The mechanical Q-switch assembly was fully athermalized via mounting a displacing porro reflector to the cantilever spring, where a 2.5mJ laser was observed to operate with less than 5% variance over -35°C to+60°C.

  6. 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

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

    NASA Astrophysics Data System (ADS)

    Li, Lifei; Zheng, Xinliang; Jin, Chenjie; Qi, Mei; Chen, Xiaoming; Ren, Zhaoyu; 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 M2 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.

  8. 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.

  9. 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

  10. High average power of Q-switched Tm:YAG slab laser

    NASA Astrophysics Data System (ADS)

    Jin, Lin; Liu, Pian; Liu, Xuan; Huang, Haitao; Yao, Weichao; Shen, Deyuan

    2016-08-01

    A laser-diode end-pumped Tm:YAG single crystal slab laser in acousto-optic Q-switched operation was demonstrated. For Q-switched operation, the average output power of 20.7 W at 1 kHz was achieved under the absorbed pump power of 83.6 W, corresponding to the slope efficiency of 36.1%, the shortest pulse width of 84 ns and the maximum pulse energy of 20.7 mJ with peak power of 250 kW were obtained.

  11. Numerical simulation and optimization of passively q-switched erbium microchip lasers

    NASA Astrophysics Data System (ADS)

    Belghachem, Nabil; Mlynczak, Jarslow

    2015-08-01

    In this article we present a procedure of optimization of passively q-switched erbium microchip lasers. The procedure is based on the rate equation model, validated by comparing the numerical results to the experimental results of pulse generation in different types of erbium/ytterbium glass microchips q-switched by Co2+ : MgAl2O4 saturable absorber. Some Degnan’s optimization limitations in case of microchip lasers were also shown and the reabsorbtion cross section of erbium glass was also estimated.

  12. Single-frequency, 500-ns laser pulses generated by a passively Q-switched Nd laser

    NASA Astrophysics Data System (ADS)

    Jones, D. C.; Rockwell, D. A.

    1993-03-01

    Accounts are given of the construction and performance of a narrowband Q-switched oscillator that addresses requirements for heavy amplifier saturation as well as a degree of temporal pulse-shaping prior to oscillator beam injection into the amplifier chain that can avoid the severe temporal distortion imposed by amplifier saturation. This oscillator encompasses a lamp-pumped Cr:Nd:GSGG laser rod, a saturable absorber Q switch, and several etalon surfaces forming the output coupler. This device can be used in large baseline holography.

  13. Passive Q-Switching Laser Performance of Yb:YVO4 Crystal

    NASA Astrophysics Data System (ADS)

    Li, Xiao-Hong; Chen, Xiao-Wen; Han, Wen-Juan; Kong, Wei-Jin; Liu, Jun-Hai

    2014-12-01

    We report on the passive Q-switching laser performance of Yb:YVO4 crystal. Utilizing a Cr4+:YAG crystal plate as the saturable absorber, which is of an initial transmission as high as 99.3%, we demonstrate a stable passively Q-switched laser operation at 1017.2 nm, producing an average output power of 0.87 W at a pulse repetition rate of 71.4 kHz, with a slope efficiency of 30%. The resulting pulse energy, duration, and peak power are 12.2 μJ, 87 ns, and 0.14 kW, respectively.

  14. Optical chopper Q-switching for flashlamp-pumped Er,Cr:YSGG lasers

    NASA Astrophysics Data System (ADS)

    Murphy, Francis J.; Arbabzadah, Emma A.; Bak, Alexey O.; Amrania, Hemmel; Damzen, Michael J.; Phillips, Chris C.

    2015-04-01

    We present a novel way of Q-switching a flashlamp-pumped, λ = 2.8 μm Er,Cr:YSGG laser, wherein a rotating polygon is used as an optical chopper. Single pulse energies of ~3.8 mJ were achieved with pulsewidths of ~305 ns. The scheme benefits from the simplicity of design, and, compared with other Q-switching methods, a reduction in losses and laser damage problems from intracavity components. We also investigate the optimization of the laser output through purging of the laser with nitrogen, and find a 29% increase in peak output energy.

  15. Q-switched 1329  nm Nd:CNGG laser.

    PubMed

    Xiao, Kun; Lin, Bin; Zhang, Qiu-Lin; Zhang, Dong-Xiang; Feng, Bao-Hua; He, Jing-Liang; Zhang, Huai-Jin; Wang, Ji-Yang

    2015-08-10

    We demonstrate a laser-diode-pumped Q-switched 1329 nm neodymium-doped calcium-niobium-gallium-garnet (Nd:CNGG) laser using a V:YAG crystal as a saturable absorber. An average output power of 353 mW and a repetition rate of 13.43 kHz for Q-switched pulses were obtained. The pulse width was from 124 to 151.4 ns under different pump powers. Output power of 685 mW was obtained without the V:YAG crystal inserted. PMID:26368377

  16. 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

    2016-01-01

    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

  17. 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.

  18. 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.

  19. 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.

  20. 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)

  1. Dual-wavelength laser induced breakdown spectroscopic technique for emission enhancement in vacuum

    NASA Astrophysics Data System (ADS)

    Antony, Jobin K.; Vasa, Nilesh J.; SridharRaja, V. L. N.; Laxmiprasad, A. S.

    2013-07-01

    A novel approach of dual-wavelength LIBS with a single Nd3+:YAG laser is proposed and demonstrated for lunar-simulant analysis in high vacuum conditions. Laser ablation was performed at 355 nm/532 nm wavelength, and subsequently, the plasma was reexcited with the fundamental (1064 nm) wavelength. The interpulse delay was adjusted by varying the optical path length. A significant line intensity enhancement up to a factor of 3 was observed for many of the dominant emission lines of the lunar simulant sample. A theoretical model for understanding the mechanism behind the intensity improvements of dual-wavelength configurations is also discussed. Experimentally observed plasma temperature was comparable with theoretically estimated plasma temperature of silicon, which is the major constituent of lunar simulant.

  2. High-speed dual-wavelength optical polarimetry for glucose sensing

    NASA Astrophysics Data System (ADS)

    Grunden, Daniel T.; Pirnstill, Casey W.; Coté, Gerard L.

    2014-02-01

    Optical polarimetry in the anterior chamber of the eye has emerged as a potential technique to non-invasively measure glucose levels for diabetes. Time varying corneal birefringence due to eye motion artifact confounds the optical signal ultimately limiting the polarimetric technique from accurately predicting glucose concentrations. In this study, a high speed dual-wavelength optical polarimetric approach was developed and in vitro phantom studies were performed with and without motion. The glucose concentrations ranged from 0-600 mg/dL at 100 mg/dL increments. The polarimeter produced glucose measurements with less than a 10 msec stabilization time and yielding standard errors of less than 10 mg/dL without motion and standard errors less than 26 mg/dL with motion. The results indicate a high speed dual-wavelength polarimetric approach has the potential to be used for non-invasive glucose measurements.

  3. 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.

  4. Continuous-wave dual-wavelength Nd:YAG laser operation at 1319 and 1338 nm

    NASA Astrophysics Data System (ADS)

    Sun, G. C.; Lee, Y. D.; Zao, Y. D.; Xu, L. J.; Wang, J. B.; Chen, G. B.; Lu, J.

    2013-04-01

    We report an efficient continuous-wave (CW) dual-wavelength operation of an Nd:YAG (YAG: yttrium aluminum garnet) laser at 1319 and 1338 nm. An output power of 2.47 W for the dual-wavelength operation was achieved at the incident pump power of 16.7 W. Intracavity sum-frequency mixing at 1319 and 1338 nm was then realized in an LBO (lithium triborate) crystal to reach the red range. A maximum output power of 879 mW in the red spectral range at 664 nm has been achieved. The red output stability is better than 3.4%. The red beam quality M2 values are about 1.21 and 1.35 in the horizontal and vertical directions respectively.

  5. Dual-Wavelength Operation of a Flashlamp Pumped Narrow-Linewidth Ti:Sapphire Laser

    NASA Astrophysics Data System (ADS)

    Takeda, Hideki; Akabane, Yousuke; Kannari, Fumihiko

    1994-12-01

    Dual-wavelength operation of a flashlamp-pumped Ti:sapphire laser employing a modified grazing-incidence grating resonator with two tuning mirrors is described. Spatially resolved laser spectra in the output beam at the near field indicate that a large part of each wavelength laser beam oscillates in the separated gain volume. Linewidth of ˜16 pm is achieved for both laser wavelengths. Simultaneous second-harmonic generation of the dual-wavelength laser is also demonstrated in the spectral range of 390 420 nm with a β-BaB2O4 nonlinear crystal. The phase-matching angle of each wavelength is automatically satisfied in a fixed optical arrangement by using four dispersive prisms and a lens.

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

    NASA Astrophysics Data System (ADS)

    Saad, Ahmed S.

    2015-08-01

    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 (ΔP252.0-258.0nm) corresponds to BM, while ΔP266.8-255.4nm and ΔP254.2-243.5nm 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.

  7. Air cushioning in droplet impact. I. Dynamics of thin films studied by dual wavelength reflection interference microscopy

    NASA Astrophysics Data System (ADS)

    de Ruiter, Jolet; Mugele, Frieder; van den Ende, Dirk

    2015-01-01

    When a liquid droplet impacts on a solid surface, it not only deforms substantially but also an air film develops between the droplet and the surface. This thin air film—as well as other transparent films—can be characterized by reflection interference microscopy. Even for weakly reflecting interfaces, relative thickness variations of the order of tens of nanometers are easily detected, yet the absolute thickness is generally known only up to an additive constant which is a multiple of half of the wavelength. Here, we present an optical setup for measuring the absolute film thickness and its spatial and temporal behavior using a combination of a standard Hg lamp, an optical microscope, and three synchronized high-speed cameras to detect conventional side-view images as well as interferometric bottom view images at two different wavelengths. The combination of a dual wavelength approach with the finite coherence length set by the broad bandwidth of the optical filters allows for measuring the absolute thickness of transient air films with a spatial resolution better than 30 nm at 50 μs time resolution with a maximum detectable film thickness of approximately 8 μm. This technique will be exploited in Part II to characterize the air film evolution during low velocity droplet impacts.

  8. Modulation frequency characteristics of the Q-switched envelope in a doubly Q-switched and mode-locked laser with acousto-optic modulator and Cr4+:YAG saturable absorber

    NASA Astrophysics Data System (ADS)

    Qiao, Junpeng; Zhao, Jia; Li, Yufei; Zhao, Shengzhi; Li, Guiqiu; Li, Dechun; Qiao, Wenchao; Chu, Hongwei

    2015-11-01

    The modulation frequency characteristics of the Q-switched envelope in a doubly Q-switched and mode-locked Nd:GGG laser with an acousto-optic modulator (AOM) and Cr4+:YAG saturable absorber are given. At a fixed incident pump power, the repetition rates of the Q-switched envelope and the related laser characteristics versus the modulation frequency of AOM for different small signal transmissions of Cr4+:YAG saturable absorbers have been measured. The experimental results show that the repetition rates of the Q-switched envelope, the average output power, the average peak power, and the pulse widths of the Q-switched envelopes are subharmonics of the modulation frequency at a fixed incident pump power. Furthermore, the mechanism for these behaviors is discussed.

  9. Five simultaneously Q-switch mode-locked passive laser modulators

    NASA Astrophysics Data System (ADS)

    Chen, Junewen

    2007-02-01

    Five types of passive Q-switched as well as simultaneously Q-switch mode-locked modulators: plastic dye sheets ( Kodak 9850 cellulose acetate dye sheets), lithium fluoride crystals containing F II - color centers ( LiF: F II -), chromium doped yttrium aluminum garnet crystals ( Cr 4+:YAG), ionic color filter glass ( Schott RG1000 color filter glass) and the single crystal semiconductor wafers ( GaAs, Fe doped InP, Zn doped InP, S doped InP, etc.) used for the modulation of the Nd:hosted(Nd:YAG, Nd:YVO 4, and Nd:LSB) lasers have been investigated in detail in our researches. We have also investigated into the applications of the Q-switch mode-locked pulses train for the development of higher resolution solid state laser range finder. We will also present the high accuracy laser ranging results, the micro-motor that driven mechanical parts from the stepping digital ranging readout, to precisely control the best focus of a miniature zoom lens modular. The core simultaneously Q-switch mode-locked modulators microchip laser is the key part of our automatic optical inspection system.

  10. Cr 4+: GSGG saturable absorber Q-switch for the ruby laser

    NASA Astrophysics Data System (ADS)

    Chen, W.; Spariosu, K.; Stultz, R.; Kuo, Y. K.; Birnbaum, M.; Shestakov, A. V.

    1993-12-01

    Cr 4+: GSGG has been utilized for the first time to provide a saturable absorber Q-switch for the ruby laser. Single output pulse operation (100 mJ and 27 ns duration) with efficiencies relative to the free-running ruby laser operation of 25-30% was routinely obtained.

  11. 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.

  12. Q-switching of mid-infrared Er:YAG laser and its radiation delivery system

    NASA Astrophysics Data System (ADS)

    Jelinkova, Helena; Koranda, Petr; Nemec, Michal; Sulc, Jan; Cech, Miroslav; Miyagi, Mitsunobu; Shi, Yi-Wei; Matsuura, Yuji

    2004-09-01

    Q-switching of mid-infrared Er:YAG laser was obtained with an electro-optical shutter. For that the LiNbO3 Pockels cell was used in transversal quarter-wave arrangement with the Brewster angle cut faces used as a polarizer. Parameters and dependences of this Q-switched system were investigated, i.e. a pulse length and generated pulse energy, delay between switching of flashlamp and Q-switch circuit, high voltage applied on Pockels cell were measured and optimized. The resulted giant pulse length and energy was 60 ns and 55 mJ, respectively. This generated pulse was obtained for the applied voltage around 1.4 kV and for the optimum delay value 450 us. Problem of mid-infrared giant pulse delivery, which is needed for various technological applications, was solved by a specially designed cyclic olefin polymer coated silver hollow glass (COP/Ag) waveguide. Parameters of this waveguide were: diameter 700/850 um and length 1 m. The measured transmission was 74 % which corresponded to delivered intensity 86 MW/cm2. Q-switched Er:YAG laser radiation in connection with this special delivery system gives a possibility of the surgical treatment in many medicine branches, for example ophthalmology, urology or dentistry.

  13. 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.

  14. SOLITONS AND OPTICAL FIBERS: Self-Q-switched ytterbium-doped cladding-pumped fibre laser

    NASA Astrophysics Data System (ADS)

    Grukh, Dmitrii A.; Kurkov, Andrei S.; Razdobreev, I. M.; Fotiadi, A. A.

    2002-11-01

    A self-Q-switched ytterbium-doped double-clad fibre laser is described. A samarium-doped fibre is used as a filter for protecting a pump source. A fibre coupler is employed to obtain a nonlinear feedback. The mechanism of pulse formation in the laser is considered, and the dependence of its output pulse on the coupler parameters is studied.

  15. 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.

  16. Dual-wavelength method and optoelectronic sensor for online monitoring of the efficiency of dialysis treatment

    NASA Astrophysics Data System (ADS)

    Vasilevsky, A. M.; Konoplev, G. A.; Stepanova, O. S.; Zemchenkov, A. Yu; Gerasimchuk, R. P.; Frorip, A.

    2015-11-01

    The absorption spectra of effluent dialysate in the ultraviolet region were investigated. A novel dual-wavelength spectrophotometric method for uric acid determination in effluent dialysate and an optoelectronic sensor based on UV LED were developed. Clinical trials of the proposed sensor were carried out in the dialysis unit of St. Petersburg Mariinsky Hospital. The relative error of measurement for the concentration of uric acid does not exceed 10%.

  17. 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

  18. Development of a real-time closed-loop dual wavelength optical polarimeter for glucose monitoring

    NASA Astrophysics Data System (ADS)

    Malik, Bilal H.; Coté, Gerard L.

    2010-02-01

    Over the last decade, noninvasive glucose sensors based on optical polarimetry have been proposed to probe the anterior chamber of the eye. Such sensors would ultimately be used to measure the aqueous humor glucose concentration which is correlated with blood glucose concentration. Although the effect of other chiral components in the eye has been minimized, the time-variant corneal birefringence due to motion artifact is still a limiting factor which needs to be resolved for realization of such a device. Here we present the development of a real-time dual wavelength optical polarimetric system employing a classical three-term feedback controller. Our dual wavelength system utilizes real-time closed-loop feedback based on proportional-integral-derivative (PID) control, which effectively reduced the time taken by the system to stabilize to less than 300 ms while minimizing the effect of motion artifact, which appears as common noise source for both wavelengths. Measurements in the presence of time-variant test cell birefringence demonstrate the sensitivity of the current system to measure glucose within the range of 0-600 mg/dl with a standard error of less than 13 mg/dl using the dual wavelength information.

  19. 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. PMID:26832513

  20. 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.

  1. Dual-wavelength erbium-doped fiber laser with tunable wavelength spacing using a twin core fiber-based filter

    NASA Astrophysics Data System (ADS)

    Yin, Guolu; Lou, Shuqin; Wang, Xin; Han, Bolin

    2014-05-01

    A dual-wavelength erbium-doped fiber laser with tunable wavelength spacing was proposed and experimentally demonstrated by using a twin core fiber (TCF)-based filter. Benefiting from the polarization dependence of the TCF-based filter, the laser operated in dual-wavelength oscillation with two orthogonal polarization states. By adjusting the polarization controller, the wavelength spacing was tuned from 0.1 nm to 1.2 nm without shifting the centre position of the two wavelengths. By stretching the TCF, the two wavelengths were simultaneously tuned with fixed wavelength spacing. Such a dual-wavelength fiber laser could find applications in optical fiber sensors and microwave photonics generation.

  2. Cavity length dependence of mode beating in passively Q-switched Nd-solid state lasers

    NASA Astrophysics Data System (ADS)

    Zameroski, Nathan D.; Wanke, Michael; Bossert, David

    2013-03-01

    The temporal intensity profile of pulse(s) from passively Q-switched and passively Q-switched mode locked (QSML) solid-state lasers is known to be dependent on cavity length. In this work, the pulse width, modulation depth, and beat frequencies of a Nd:Cr:GSGG laser using a Cr+4:YAG passive Q-switch are investigated as function cavity length. Measured temporal widths are linearly correlated with cavity length but generally 3-5 ns larger than theoretical predictions. Some cavity lengths exhibit pulse profiles with no modulation while other lengths exhibit complete amplitude modulation. The observed beat frequencies at certain cavity lengths cannot be accounted for with passively QSML models in which the pulse train repetition rate is τRT-1, τRT= round-trip time. They can be explained, however, by including coupled cavity mode-locking effects. A theoretical model developed for a two section coupled cavity semiconductor laser is adapted to a solid-state laser to interpret measured beat frequencies. We also numerically evaluate the temporal criterion required to achieve temporally smooth Q-switched pulses, versus cavity length and pump rate. We show that in flash lamp pumped systems, the difference in buildup time between longitudinal modes is largely dependent on the pump rate. In applications where short pulse delay is important, the pumping rate may limit the ability to achieve temporally smooth pulses in passively Q-switched lasers. Simulations support trends in experimental data. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  3. The radio-on-fiber-wavelength-division-multiplexed-passive-optical network (WDM-RoF-PON) for wireless and wire layout with linearly-polarized dual-wavelength fiber laser and carrier reusing

    NASA Astrophysics Data System (ADS)

    Ji, Wei; Chang, Jun

    2013-07-01

    In this paper, we design a WDM-RoF-PON based on linearly-polarized dual-wavelength fiber laser and CSRZ-DPSK, which can achieve wire-line and wireless access synchronously. With the CSRZ-DPSK modulation, the wireless access in ONU can save RF source and the frequency of radio carrier can be controlled by OLT. The dual-wavelength fiber laser is the union light source of WDM-PON with polarization multiplexing. By the RSOA and downstream light source reusing, the ONU can save omit laser source and makes the WDM-PON to be colorless. The networking has the credible transmission property, including wireless access and fiber transmission. The networking also has excellent covering range.

  4. 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.

  5. 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.

  6. Low-threshold and multi-wavelength Q-switched random erbium-doped fiber laser

    NASA Astrophysics Data System (ADS)

    Wang, Simin; Lin, Wei; Chen, Weicheng; Li, Can; Yang, Changsheng; Qiao, Tian; Yang, Zhongmin

    2016-03-01

    We demonstrate a low-threshold and multi-wavelength Q-switched random fiber laser with erbium-doped fiber as the gain medium and Rayleigh scattering as the randomly distributed feedback. Q-switched pulses are generated with threshold as low as 27 mW by combining random cavity resonances and the Q-value modulation effect induced by stimulated Brillouin scattering. The repetition rate is typically on the kilohertz scale with rms timing jitter of <5.5% and rms amplitude fluctuation of <30%. Raman Stokes emissions up to the third order are observed with an overall energy of nearly 42% of the pulse output, which may open an avenue for applications requiring multiple wavelengths.

  7. Multiple folded resonator for LD pulse end pumped Q-switched Yb:YAG slab laser.

    PubMed

    Jun, Liu; Jianguo, Xin; Ye, Lang; Jiabin, Chen

    2014-09-01

    In this paper, a multiple folded resonator is presented which consists of a multiple optical folding setup, a flat total reflector, a flat output coupler, a Q-switch crystal and a polarizer. By this technique, the output energy of 32.6mJ and pulse width of 13.4ns with a repetition rate of 5Hz was obtained, which is three times higher than that reported in the past publications by the use of the currently existing technique of the Q-switched slab gain lasers with the unstable resonator. The output beam with a quality of M² = 1.55 in the slow axis and M² = 1.40 in the fast axis was also obtained. PMID:25321590

  8. Passively Q-switched microchip lasers based on Yb:YAG/Cr4+:YAG composite crystal

    NASA Astrophysics Data System (ADS)

    Ren, Yingying; Dong, Jun

    2014-02-01

    Efficient passively Q-switched microchip laser based on Yb:YAG/Cr4+:YAG composite crystal has been demonstrated under high brightness single-emitter laser-diode pumping. Maximum average output power of 1.5 W was obtained when the absorbed pump power was 3.65 W, the corresponding optical-to-optical efficiency was over 41%. The slope efficiency was 52.3%. The effect of the cavity length on the performance of Yb:YAG/Cr4+:YAG composite crystal passively Q-switched microchip lasers was investigated. Laser pulses at 1030 nm with pulse width of 466 ps and peak power of 91 kW were achieved with cavity length of 1.7 mm, while laser pulses with pulse width of 665 ps and peak power of 79 kW were obtained with cavity length of 3.7 mm.

  9. Continuous-wave and passively Q-switched cladding-pumped planar waveguide lasers.

    PubMed

    Beach, R J; Mitchell, S C; Meissner, H E; Meissner, O R; Krupke, W F; McMahon, J M; Bennett, W J; Shepherd, D P

    2001-06-15

    Greater than 12 W of average output power has been generated from a diode-pumped Yb:YAG cladding-pumped planar waveguide laser. The laser radiation developed is linearly polarized and diffraction limited in the guiding dimension. A slope efficiency of 0.5 W/W with a peak optical-optical conversion efficiency of 0.31 W/W is achieved. In a related structure, greater than 8 W of Q -switched average output power has been generated from a Nd:YAG cladding-pumped planar waveguide laser by incorporation of a Cr(4+): YAG passive Q switch monolithically into the waveguide structure. Pulse widths of 3 ns and pulse-repetition frequencies as high as 80 kHz have been demonstrated. A slope efficiency of 0.28 W/W with a peak optical-optical conversion efficiency of 0.21 W/W is achieved. PMID:18040479

  10. Q-switched Erbium-doped fiber laser using MoSe2 as saturable absorber

    NASA Astrophysics Data System (ADS)

    Ahmad, H.; Suthaskumar, M.; Tiu, Z. C.; Zarei, A.; Harun, S. W.

    2016-05-01

    A Q-switched Erbium-doped fiber laser by using MoSe2 thin film as saturable absorber is experimentally demonstrated. The bulk MoSe2 is processed into few layer MoSe2 based on liquid phase exfoliation technique, and further fabricated into thin film by using polyvinyl alcohol polymer. Q-switching operation is obtained from pump power range of 22.4-102.0 mW. The pulse repetition rate shows an increasing trend from 16.9 kHz to 32.8 kHz, whereas the pulse width exhibits a decreasing trend from 59.1 μs to 30.4 μs. The highest pulse energy of 57.9 nJ is obtained at pump power of 102.0 mW.

  11. An 885-nm Direct Pumped Nd:CNGG 1061 nm Q-Switched Laser

    NASA Astrophysics Data System (ADS)

    Li, Qi-Nan; Zhang, Tao; Feng, Bao-Hua; Zhang, Zhi-Guo; Zhang, Huai-Jin; Wang, Ji-Yang

    2014-07-01

    The 885 nm direct pumping method, directly into the 4F3/2 emitting level of Nd3+ ion, is used to a Nd:CNGG crystal to product passive Q-switched 1061 nm laser pulses, for the first time to the best of our knowledge. A maximum average output power of 1.16 W for 1061 nm Q-switched pulses and a repetition rate of 12.54 kHz are obtained. The pulse width is measured to be 24 ns and the peak power is 3.843 kW. A high-quality fundamental transverse mode can be observed owing to the reduction of the thermal effect for Nd:CNGG crystal by 885 nm direct pumping.

  12. All-solid-state passively Q -switched mode-locked Nd-doped fiber laser

    SciTech Connect

    Zenteno, L.A.; Po, H.; Cho, N.M. )

    1990-01-15

    We report the generation of {ital Q}-switched mode-locked pulses from a Nd-doped fiber laser that uses a solid-state solution of BDN-I dye as the saturable absorber and is pumped by a GaAlAs laser diode. For an absorbed pump power of 110 m W, pulses of 8-nsec duration at a repetition rate of 14 MHz can be generated under an 800-nsec-wide {ital Q}-switched envelope at a repetition rate of 100 kHz, yielding an average output power of 8 m W near 1.06 {mu}m. This corresponds to approximately 9 W of peak power in the main mode-locked pulse.

  13. 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.

  14. 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

  15. Analysis of related factor of pigment alteration after Q-switched laser treatment

    NASA Astrophysics Data System (ADS)

    Zhang, Wei; Xu, Cai Xia; Ding, Yang Feng; Tan, Yi Wen

    2005-07-01

    To explore the related factors of pigment alteration after the Q-switched laser treatment. After the Q-switched laser treatment, the side effects in patients were observed, recorded and analyzed. The results showed that the incidence of pigment alteration is directly related to age (OR1=2.519, confidence interval 0.996-6.366; OR2=2.519, confidence interval 0.978-6.488; OR3=8.311, confidence interval 3.312-29.695). Besides, the pigment alteration is also correlated to the skin types, but not to gender, kind of diseases, parts of body, intensity of ultraviolet radiation, character of work, wavelength of laser and the energy of laser. Older patient is easier to have pigment alteration than younger patient. Pigment alteration may be obvious in a pigmented individual than a lightly pigmented individual.

  16. Tunable Q-switched fiber laser using zinc oxide nanoparticles as a saturable absorber.

    PubMed

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

    2016-06-01

    Nanomaterials have ignited new interest due to their distinctive electronic, mechanical, and optical properties. Zinc oxide nanostructures are fabricated into thin film and then inserted between two fiber ferrules to act as a saturable absorber (SA). The modulation depth and insertion loss of the SA are 5% and 3.5 dB, respectively. When the ZnO-SA is incorporated into the laser cavity, a stable Q-switched pulse tunable from 1536 to 1586 nm (50 nm range) with pulse energy up to 46 nJ was observed. Our result suggests that ZnO is a promising broadband SA to generate passively Q-switched fiber lasers. PMID:27411175

  17. 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.

  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. 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.

  20. Dual-wavelength operation of monolithically integrated arrayed waveguide grating lasers for optical heterodyning

    NASA Astrophysics Data System (ADS)

    Guzmán M., Robinson C.; Jimenez, Álvaro; Lawniczuk, Katarzyna; Corradi, Antonio; Leijtens, Xaveer J. M.; Bente, Erwin A. J. M.; Carpintero, Guillermo

    2013-05-01

    A cost-effective solution to provide higher data rates in wireless communication system is to push carrier wave frequencies into millimeter wave (MMW) range, where the frequency bands within the E-band and F-band have been allocated. Photonics is a key technology to generate low phase noise signals, offering methods of generating continuous MMW with varying performance in terms of frequency bandwidth, tunability, and stability. Recently, we demonstrated for the first time of our knowledge the generation of a 95-GHz signal by optical heterodyning of two modes from different channels of a monolithically integrated arrayed waveguide grating multi-wavelength laser (AWGL). The device uses an arrayed waveguide grating (AWG) as an intra-cavity filter. With up to 16-channel sources with independent amplifiers and a booster amplifier on the common waveguide, the laser cavity is formed between cleaved facets of the chip. The two wavelengths required for optical heterodyning are generated activating simultaneously two channel SOAs and the Boost amplifier. In this work, we analyze the effect on the dual-wavelength operation of the Boost SOA, which is shared by two wavelengths. Mapping the optical spectrum, sweeping the two channel and Boost bias currents, we show the interaction among the different SOAs two find the regions of dual wavelength operation. The size of dual wavelength operation region depends greatly on the Boost SOA bias level. Initial results of a numerical model of the AWGL will be also presented, in which a digital filter is used to implement the AWG frequency behavior.

  1. Pulse synchronisation in passively Q-switched lasers emitting at 1.053 and 1.064 {mu}m

    SciTech Connect

    Bagdasarov, V Kh; Denisov, N N; Malyutin, A A; Chigaev, I A

    2009-10-31

    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). (control of laser radiation parameters)

  2. 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. PMID:26974625

  3. Generation of single longitudinal mode in a pulsed passively Q -switched Nd:YAG laser

    SciTech Connect

    Hariri, A.; Soltanmoradi, F.; Nayeri, M. )

    1990-08-01

    It is shown that a single longitudinal mode in a passively {ital Q}-switch Nd:YAG laser can be obtained by adjusting an intracavity saturable absorber gelatin film (BDN) to work as a mirror in a three-mirror Fabry--Perot resonator. With a 0.13-mm-thick gelatin film of 40% unsaturated transmission, a temporally smooth single-laser pulse of {similar to}10 ns duration has been obtained.

  4. Frequency tuning characteristics of a Q-switched Co:MgF2 laser

    NASA Technical Reports Server (NTRS)

    Lovold, S.; Moulton, P. F.; Killinger, D. K.; Menyuk, N.

    1985-01-01

    A tunable Q-switched Co:MgF2 laser has been developed for atmospheric remote sensing applications. Frequency tuning is provided by a quartz etalon and a specially designed three-element birefringent filter covering the whole gain bandwidth of the Co:MgF2 laser. The laser has good temporal and spectral characteristics, with an emission linewidth of approximately 3 GHz (0.1 per cm).

  5. Clinical effects of iridectomy performed by laser YAG Nd+3 Q switch

    NASA Astrophysics Data System (ADS)

    Kecik, Tadeusz; Zydecki, Miroslaw

    1995-03-01

    Clinical effects of iridectomy performed by the use of laser Yag Nd+3-Q-switch on 38 patients treated for intra-ocular pressure increase were analyzed. In 32 cases primary glaucoma was diagnosed. In 11 cases secondary glaucoma was caused by pupil blocking. Pressure normalization was obtained in 27 cases (71%). In the remaining 11 patients pressure decreasing was acquired but at the same time administration of antiglaucoma medicines was indispensable. Time of observation took from 4 weeks to 3 years.

  6. 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.

  7. Q-switched Tm-doped fiber lasers using dynamic microbends in oval-coating fibers

    NASA Astrophysics Data System (ADS)

    Araki, S.; Kimpara, K.; Tomiki, M.; Sakata, H.

    2013-06-01

    We present Q-switched pulse generation in a thulium-doped fiber laser by inducing a piezoelectric-driven microbend into an oval-coating fiber. The oval-coating fiber is made of a single-mode fiber in which an acrylic coating is flattened by thermal pressing. A pulse peak power of 1.45 W is obtained with a pump power of 139 mW.

  8. Modified grating-based external cavity diode laser for simultaneous dual-wavelengths operation

    NASA Astrophysics Data System (ADS)

    Khorsandi, Alireza; Sabouri, Saeed Ghavami; Fathi, Somaieh; Asadnia-Jahromi, Marzieh

    2011-07-01

    We have reported a modified V-shaped external cavity, which is constructed around a commercial diode laser operating at a center wavelength of λ=785 nm by adding a new coated glass plate with about 50% reflectivity to the cavity. This allows simultaneous dual-wavelengths operation in the vicinity of Δ νmin=0.18 THz to Δ νmax=0.22 THz, which can be used as laser source for terahertz generation either for semiconductor devices or nonlinear schemes.

  9. 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. PMID:27140105

  10. Dual-wavelength laser operation at 1061 and 942 nm in Nd:GSAG

    NASA Astrophysics Data System (ADS)

    Fu, X. H.; Che, Y.; Li, Y. L.

    2011-06-01

    A dual-wavelength continuous-wave (CW) diode end-pumped gadolinium scandium aluminum garnet (Nd:GSAG) laser that generates simultaneous laser action at the wavelengths 1061 and 942 nm is demonstrated. A total output power of 589 mW (476 mW at 1061 nm and 113 mW at 942 nm) for the dual-wave-length was achieved at the incident pump power of 18.2 W. The M 2 values for 942 and 1061 nm lights were found to be around 1.18 and 1.37, respectively.

  11. Handheld dual-wavelength Raman instrument for the detection of chemical agents and explosives

    NASA Astrophysics Data System (ADS)

    Christesen, Steven D.; Guicheteau, Jason A.; Curtiss, Justin M.; Fountain, Augustus W.

    2016-07-01

    Handheld Raman systems have become powerful analytical tools for the detection and identification of hazardous chemical materials that are now commonly used by both the civilian and military communities. Due to the availability of compact lasers and sensitive detectors, systems typically operate at 785 nm. However, the Raman return at this wavelength can still be obscured by fluorescent impurities in the targeted materials or their matrices. To potentially mitigate this shortcoming, a prototype dual-wavelength Raman incorporating both 785- and 1064-nm excitations was developed and assessed at the Edgewood Chemical Biological Center. The results of that evaluation are discussed here.

  12. Y-branch integrated dual wavelength laser diode for microwave generation by sideband injection locking.

    PubMed

    Huang, Jin; Sun, Changzheng; Xiong, Bing; Luo, Yi

    2009-11-01

    A Y-branch integrated dual wavelength laser diode is fabricated for optical microwave generation based on the principle of sideband injection locking. The device integrates a master laser and a slave laser with associated Y-branch coupler. By directly modulating the master laser near its relaxation resonance frequency, multiple sidebands are generated due to enhanced modulation nonlinearity. Beat signal with high spectral purity is obtained by injection locking the slave laser to one of the modulation sidebands. A millimeter-wave carrier of 42-GHz with a phase noise of -94.6 dBc/Hz at 10 kHz offset is demonstrated. PMID:19997304

  13. 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.

  14. Passively Q-switched diode-pumped Yb:YAG laser using Cr4+-doped garnets

    NASA Astrophysics Data System (ADS)

    Kalisky, Yehoshua Y.; Labbe, Christophe; Waichman, Karol; Kravchik, Leonid; Rachum, U.; Deng, Peizhen; Xu, Jun; Dong, Jun; Chen, Wei

    2002-03-01

    We investigated the operation of a diode-pumped Yb:YAG laser passively Q-switched, by Cr4+:YAG, Cr4+:LuAG, and Cr4+: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. (sigma) emequals3.3x10-20 cm2 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 approximately equals 10.4-kW, and energy of approximately equals 0.5 mJ/pulse were extracted with 30% extraction efficiency.

  15. 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

  16. 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. PMID:27409862

  17. Passive Q-switching of microchip lasers based on Ho:YAG ceramics.

    PubMed

    Lan, R; Loiko, P; Mateos, X; Wang, Y; Li, J; Pan, Y; Choi, S Y; Kim, M H; Rotermund, F; Yasukevich, A; Yumashev, K; Griebner, U; Petrov, V

    2016-06-20

    A Ho:YAG ceramic microchip laser pumped by a Tm fiber laser at 1910 nm is passively Q-switched by single- and multi-layer graphene, single-walled carbon nanotubes (SWCNTs), and Cr2+:ZnSe saturable absorbers (SAs). Employing SWCNTs, this laser generated an average power of 810 mW at 2090 nm with a slope efficiency of 68% and continuous wave to Q-switching conversion efficiency of 70%. The shortest pulse duration was 85 ns at a repetition rate of 165 kHz, and the pulse energy reached 4.9 μJ. The laser performance and pulse stability were superior compared to graphene SAs even for a different number of graphene layers (n=1 to 4). A model for the description of the Ho:YAG laser Q-switched by carbon nanostructures is presented. This modeling allowed us to estimate the saturation intensity for multi-layered graphene and SWCNT SAs to be 1.2±0.2 and 7±1  MW/cm2, respectively. When using Cr2+:ZnSe, the Ho:YAG microchip laser generated 11 ns/25 μJ pulses at a repetition rate of 14.8 kHz. PMID:27409113

  18. 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.

  19. Visual acuity changes in rhesus following low-level Q-switched exposures

    NASA Astrophysics Data System (ADS)

    Robbins, David O.; Zwick, Harry; Bearden, Bradley D.; Evans, Brenda S.; Stuck, Bruce E.

    1997-05-01

    Previously we have shown that visual deficits can be produced by long duration pulses at or slightly below traditional threshold levels for retinal injury. Initially the deficits produced were only transient shifts in baseline acuity that lasted less than 30 min, but successive exposures over a period of days at these same power levels were shown to be cumulative and their impact on visual acuity lengthened and became permanent. The present investigation extended these exposures to Q-switched, 532 nm Nd/YAG pulses presented to awake, task-oriented nonhuman primates performing Landolt ring discriminations. At and above the ED50, single pulses of minimal spot diameter produced only minor, transient shifts in visual acuity while repeated exposures produced significant shifts in acuity that became permanent over time. At lower energies, minimal spot, single-pulsed exposures again produced little observable consequence until either retinal spot sizes or number of pulses were increased. At these lower energy levels, however, no permanent functional loss was observed. Hence, the functional impact of single Q-switched pulses was more difficult to assess than longer time domain exposures. Multiple, low level Q-switched pulses, and/or larger spot sizes produced visual deficits similar to those observed for msec time domain exposures, suggesting both temporal and spatial summation at energy levels where no permanent effects have been noted.

  20. The design of passively Q-switched solid-state lasers

    NASA Astrophysics Data System (ADS)

    Xiao, Guohua

    The passively Q-switched laser has been of intense interest because it is generally simple, convenient, and requires a minimum of intracavity elements and no external high voltage or RF drivers. Z-scan technique was used to obtain more realistic values of the ground and excited state absorption cross sections of Cr:YAG, one of the most important solid state saturable absorbers. Other spectroscopic research revealed that Cr:YAG performs stably over the wide temperature range from -70 to +80°C. A generalized model of a passively Q-switched laser was developed. It enables performance optimization including general cases in which the saturable absorber exhibits both ground and excited state absorption at the laser wavelength. Based on the theory, we built and tested a Nd:glass laser passively Q-switched by a Cr4+:YAG crystal and found excellent agreement with our model. The model was then extended to the case where an optical parametric oscillator (OPO) is contained inside the passively Q-switched laser cavity. In such a laser there is no output at the fundamental or pump wavelength. When the OPO signal field begins to build up, it acts as a loss for the pump and cavity dumps the pump resonator. The extended model describes the complicated interactions between the fundamental laser gain medium, saturable absorber, fundamental laser cavity, and OPO cavity. The model developed enables one to select OPO parameters which optimize the system's performance. Application of the model to a very compact, lightweight, eye-safe laser range finder operating at 1.54 μm will also be presented. Many applications demand lasers to be operated over a wide temperature range (-55-75°C). Efforts were dedicated to obtaining information on the temperature dependence of the emission cross section of Nd,Cr:GSGG and the optical properties of certain laser resonator optics. The data serve as input parameters to the models to design passively Q-switched laser systems with predictable

  1. 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. PMID:27557200

  2. 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

    2016-01-01

    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 (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. PMID:26950126

  3. 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.

  4. 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

  5. Study of a symmetrically structured SPR sensor and its dual-wavelength differential method

    NASA Astrophysics Data System (ADS)

    Yang, Hai-ma; Ma, Cai-wen; Wang, Jian-yu; Liu, Jin; Chen, Bao-xue

    2016-01-01

    This study investigates a novel structure for surface plasmon resonance sensing and its dual-wavelength differential method. The surface plasmon wave is excited by a planar waveguide, which is prepared through the ion-exchange method. The distribution of refractive indices is fitted by the Fermi function. The sensing structure is based on a symmetric structure with a metal layer, a measured medium, and another metal layer. The condition for refractive index matching changes with the thicknesses of test samples, thus the test range can be adjusted using this structure. Given two appropriate wavelengths ? and ? for detection by the intensity method and an increase in the refractive index, the intensity variety at ? can be positive, whereas that at ? can be negative. When the refractive indices are determined based on differential values, sensitivity is improved. Solutions with refractive index values ranging from 1.33 to 1.428 are detected in the experiments using the single-wavelength method and the dual-wavelength differential method. Results show that the differential detection method enhances the adjustability and sensitivity of the SPR sensor in combination with a symmetric structure.

  6. 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.

  7. 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.

  8. 520 mJ langasite electro-optically Q-switched Cr, Tm, Ho:YAG laser.

    PubMed

    Wang, Li; Cai, Xuwu; Yang, Jingwei; Wu, Xianyou; Jiang, Haihe; Wang, Jiyang

    2012-06-01

    A flash lamp pumped 2.09 μm Cr, Tm, Ho:YAG laser utilizing a self-grown La(3)Ga(5)SiO(14) crystal as the electro-optic Q-switch generator is proposed and demonstrated for the first time. Operating at 3 Hz repetition rate, 520 mJ pulse energy with 35 ns pulse width is achieved by optimizing the Q-switch delay time and compensating for the thermal depolarization with a quarter-wave plate. The corresponding peak power is 14.86 MW, and the Q-switched-to-normal-mode energy extraction efficiency is 66.3%. To our knowledge, this Q-switched giant pulse is the best result reported to date in 2.09 μm laser resonator. PMID:22660096

  9. Q-switched Ho:Lu2O3 laser at 2.12 μm.

    PubMed

    Lamrini, Samir; Koopmann, Philipp; Scholle, Karsten; Fuhrberg, Peter

    2013-06-01

    We report on a Q-switched Ho:Lu2O3 laser resonantly pumped by a GaSb-based laser diode stack at 1.9 μm. The maximum output energy extracted from the compact plano-plano acousto-optically Q-switched resonator was 8 mJ at a 100 Hz pulse repetition rate, while the peak power was 40 kW. The laser wavelength was 2.124 μm. PMID:23722799

  10. 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.

  11. 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)

  12. Single-shot dual-wavelength phase reconstruction in off-axis digital holography with polarization-multiplexing transmission.

    PubMed

    Wang, Zhe; Jiang, Zhuqing; Chen, Yifei

    2016-08-01

    A new system for single-shot dual-wavelength digital holographic microscopy with polarization-multiplexing path-shared transmission is presented. The key feature of the optical configuration is that the interference waves of two wavelengths having orthogonal polarization can transmit in the same interferometer paths at the same time, and two polarizers orthogonal to each other are placed in front of the CCD to realize single-shot recording of two holograms. The correlative filtering algorithm of the spatial-frequency spectrum for dual-wavelength digital holograms is reliable and efficient in the dual-wavelength path-shared configuration. The phase reconstruction in dual-wavelength digital holographic imaging is achieved by using this filtering algorithm. The experiment results of phase reconstruction of a groove grating demonstrate the reliability and validity of this optical configuration and the correlative filtering algorithm. This polarization-multiplexing configuration for dual-wavelength digital holography is compact and has more flexibility for the replacement of different-wavelength lasers. PMID:27505390

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

    PubMed

    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

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

    NASA Astrophysics Data System (ADS)

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

    2016-07-01

    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.

  15. 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

  16. 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

  17. 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.

  18. Erbium-doped fiber triple-ring laser configuration with single-longitudinal-mode dual-wavelength output

    NASA Astrophysics Data System (ADS)

    Yeh, Chien-Hung; Chen, Hone-Zhang; Chen, Jhih-Yu; Tsai, Ning; Zhuang, Yuan-Hong; Chen, Jing-Heng; Lin, Fey

    2016-02-01

    In this investigation, we propose and demonstrate a stabilized single-longitudinal-mode (SLM) dual-wavelength erbium-doped fiber (EDF) laser triple-ring cavity. Here, two fiber Bragg gratings (FBGs) are used inside the fiber cavity to generate dual-wavelength output. In order to complete the SLM output, the triple-ring configuration is utilized for suppressing the densely multi-longitudinal mode (MLM). The output powers and wavelengths of  -8.4 and  -8.5 dBm and 1535.76 and 1543.28 nm are obtained in the proposed dual-wavelength EDF laser, respectively. Moreover, the stability performances of output power and wavelength in the proposed EDF laser are also discussed.

  19. A tunable and switchable single-longitudinal-mode dual-wavelength fiber laser with a simple linear cavity.

    PubMed

    He, Xiaoying; Fang, Xia; Liao, Changrui; Wang, D N; Sun, Junqiang

    2009-11-23

    A simple linear cavity erbium-doped fiber laser based on a Fabry-Perot filter which consists of a pair of fiber Bragg gratings is proposed for tunable and switchable single-longitudinal-mode dual-wavelength operation. The single-longitudinal-mode is obtained by the saturable absorption of an unpumed erbium-doped fiber together with a narrow-band fiber Bragg grating. Under the high pump power (>166 mW) condition, the stable dual-wavelength oscillation with uniform amplitude can be realized by carefully adjusting the polarization controller in the cavity. Wavelength selection and switching are achieved by tuning the narrow-band fiber Bragg grating in the system. The spacing of the dual-wavelength can be selected at 0.20 nm (approximately 25.62 GHz), 0.22 nm (approximately 28.19 GHz) and 0.54 nm (approximately 69.19 GHz). PMID:19997420

  20. 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.

  1. 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.

  2. Detonation of insensitive high explosives by a Q-switched ruby laser.

    NASA Technical Reports Server (NTRS)

    Yang, L. C.; Menichelli, V. J.

    1971-01-01

    Immediate longitudinal detonations have been observed in confined small-diameter columns of PETN, RDX, and tetryl by using a focused Q-switched ruby laser. The energy ranged from 0.8 to 4.0 J in a pulse width of 25 nsec. A 1000-A-thick aluminum film deposited on a glass window was used to generate a shock wave at the window-explosive interface when irradiated by the laser. In some cases, steady-state detonations were reached in less than .5 microsec with less than 10% variation in the detonation velocity.

  3. VCSEL end-pumped passively Q-switched Nd:YAG laser with adjustable pulse energy.

    PubMed

    Goldberg, Lew; McIntosh, Chris; Cole, Brian

    2011-02-28

    A compact, passively Q-switched Nd:YAG laser utilizing a Cr4+:YAG saturable absorber, is end-pumped by the focused emission from an 804 nm vertical-cavity surface-emitting laser (VCSEL) array. By changing the VCSEL operating current, we demonstrated 2x adjustability in the laser output pulse energy, from 9 mJ to 18 mJ. This energy variation was attributed to changes in the angular distribution of VCSEL emission with drive current, resulting in a change in the pump intensity distribution generated by a pump-light-focusing lens. PMID:21369256

  4. The passive Q-switching regime in a solid state laser with a multiloop cavity

    NASA Astrophysics Data System (ADS)

    Pogoda, A. P.; Burkovskii, G. V.; Makarchuk, P. S.; Khakhalin, I. S.; Boreisho, A. S.; Fedin, A. V.

    2016-03-01

    A compact, pulsed-periodic YAG: Nd3+ laser with self-pumped phase-conjugate multiloop cavity and passive Q-switching by YAG: Cr 4+ and GSGG: Cr 4+ crystals has been studied. It is established that the energy and temporal parameters of radiation in separate pulses of a periodic train can be controlled almost without changing the pulse train energy. A regime of generating modulated radiation pulses with a peak power of up to 30 MW and a spatial brightness of 1.7 × 1015 W/(cm2 sr) at a radiation beam quality parameter of M 2 < 1.2 has been realized in experiment.

  5. Azimuthally polarized, passively Q-switched Yb-doped fiber laser

    NASA Astrophysics Data System (ADS)

    Zou, Lin; Yao, Yao; Han, Xiahui; Liu, Jinyu; Xu, Yun; Li, Jianlang

    2015-11-01

    An azimuthally polarized and passively Q-switched ytterbium-doped fiber laser was demonstrated. With the involvement of a single lens inside the laser resonator, a birefringent crystal was used as the polarization discriminator, and a Cr4+:YAG crystal acted as the saturable absorber and also the output coupler. For the simplicity and low optical loss of the resonator cavity, this fiber laser emitted azimuthally polarized pulse with a high slope efficiency of 72.6% and high average power of 4.11 W. The laser pulse had 132-ns duration and 112-kHz repetition rate at the absorbed pump power of 6.40 W.

  6. Correct calibration procedure for the Q-switched ruby laser and checking the treatment irradiation pattern

    PubMed Central

    Ohshiro, Takafumi; Sasaki, Katsumi; Takenouchi, Kiyofumi; Kozuma, Mituaki; Ohshiro, Naoyuki; Kageyama, Yuichi

    2013-01-01

    Background and aims: There are many Q-switched lasers. The Q-switched ruby laser is the one most popularly used in dermatology, aesthetic surgery and plastic surgery, to remove pigmented lesions or tattoos. Correct and regular calibration of such a system is essential. However, some clinics fail to perform this with the excuse of having no measuring instrument (MI) in their offices or treatment rooms in some of their hospitals or clinics, or even the case of well-known medical universities in Japan. The present article explains the precise calibration procedure and beam pattern checking for the Q-switched ruby systems in the first author's clinic. Rationale: In the case of treatment with a medical laser, the calibration and the irradiated pattern (IP) check of the laser being used for treatment are the most important factors for treatment efficacy and safety. If these factors change, the treatment result could be different from that expected. Such kind of data are not acceptable as scientific information for a presentation or published paper. With such unreliable results and incorrect beam pattern, replicating such a study would be impossible Regular calibration check: In our clinic, we have 2 Q-switched ruby laser systems. On a daily basis, the beam patterns, both the optical axis of the beam and its treatment footprint, are checked on dedicated printed sheets and footprint paper, respectively, at the beginning of the day and after the last procedure. Every two weeks we calibrate our systems in-house using a precise MI. Every six months we calibrate the systems in-house with the MI, and then we send the systems back to the manufacturers for calibration. Once every year, we have our MI calibrated by an accredited facility in Japan. In this way, we are not only ensuring accurate and safe treatment for our patients, but we are also producing accurate system and treatment data which can be replicated by others, the basis of evidence-based medicine. PMID:24204090

  7. A highly efficient graphene oxide absorber for Q-switched Nd:GdVO4 lasers

    NASA Astrophysics Data System (ADS)

    Wang, Yong Gang; Chen, Hou Ren; Wen, Xiao Ming; Hsieh, Wen Feng; Tang, Jau

    2011-11-01

    We demonstrated that graphene oxide material could be used as a highly efficient saturable absorber for the Q-switched Nd:GdVO4 laser. A novel and low-cost graphene oxide (GO) absorber was fabricated by a vertical evaporation technique and high viscosity of polyvinyl alcohol (PVA) aqueous solution. A piece of GO/PVA absorber, a piece of round quartz, and an output coupler mirror were combined to be a sandwich structure passive component. Using such a structure, 104 ns pulses and 1.22 W average output power were obtained with the maximum pulse energy at 2 µJ and a slope efficiency of 17%.

  8. Dual-wavelength diode laser with electrically adjustable wavelength distance at 785  nm.

    PubMed

    Sumpf, Bernd; Kabitzke, Julia; Fricke, Jörg; Ressel, Peter; Müller, André; Maiwald, Martin; Tränkle, Günther

    2016-08-15

    A spectrally adjustable monolithic dual-wavelength diode laser at 785 nm as an excitation light source for shifted excitation Raman difference spectroscopy (SERDS) is presented. The spectral distance between the two excitation wavelengths can be electrically adjusted between 0 and 2.0 nm using implemented heater elements above the distributed Bragg reflector (DBR) gratings. Output powers up to 180 mW at a temperature of 25°C were measured. The spectral width is smaller than 13 pm, limited by the spectrum analyzer. The device is well-suited for Raman spectroscopy, and the flexible spectral distance allows a target-specific adjustment of the excitation light source for shifted excitation Raman difference spectroscopy (SERDS). PMID:27519065

  9. Simultaneous Temperature and Strain Sensing for Cryogenic Applications Using Dual-Wavelength Fiber Bragg Gratings

    NASA Technical Reports Server (NTRS)

    Wu, Meng-Chou; Prosser, William H.

    2003-01-01

    A new technique has been developed for sensing both temperature and strain simultaneously by using dual-wavelength fiber-optic Bragg gratings. Two Bragg gratings with different wavelengths were inscribed at the same location in an optical fiber to form a sensor. By measuring the wavelength shifts that resulted from the fiber being subjected to different temperatures and strains, the wavelength-dependent thermo-optic coefficients and photoelastic coefficients of the fiber were determined. This enables the simultaneous measurement of temperature and strain. In this study, measurements were made over the temperature range from room temperature down to about 10 K, addressing much of the low temperature range of cryogenic tanks. A structure transition of the optical fiber during the temperature change was found. This transition caused splitting of the waveforms characterizing the Bragg gratings, and the determination of wavelength shifts was consequently complicated. The effectiveness and sensitivities of these measurements in different temperature ranges are also discussed.

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

    SciTech Connect

    Khmaladze, A.; Restrepo-Martinez, A.; Kim, M.; Castaneda, R.; Blandon, A.

    2008-06-15

    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.

  11. Determination of dry sludge in heavy oil by dual wavelength spectrophotometry

    SciTech Connect

    Fukui, Y.; Nakai, S.; Yamazoe, S. )

    1989-04-01

    Contents of dry sludge in heavy oils have been usually determined by the gravimetric methods. These methods involve complicated operations and require much time. Therefore, a simplified and rapid method for the determination of dry sludge has been awaited both for process control and quality control in a petroleum refinery. Recently, some spectrophotometric methods have been reported by Ono, Mirsayapova, et al., Kaibara, et al, and Fukui for the determination of asphaltene in residual oils. However, no spectrometric method for the determination of dry sludge has ever been reported. A novel method for the rapid determination of dry sludge has been achieved by dual wavelength spectrophotometry. Dry sludge can be determined directly without any solvent, using a thin-walled cell. The method is available for high viscosity oils up to 20,000 cSt {at}50{degree}C, and the time required for the determination is much reduced, compared with the conventional gravimetric methods.

  12. Tunable photonic microwave generation by directly modulating a dual-wavelength amplified feedback laser

    NASA Astrophysics Data System (ADS)

    Yu, Liqiang; Lu, Dan; Sun, Yu; Zhao, Lingjuan

    2015-06-01

    A compact and simple approach to realizing tunable high-frequency photonic microwave using a directly-modulated dual-wavelength amplified feedback laser (AFL) diode is demonstrated. By directly modulating the AFL at the 1/2 sub-harmonic frequency of its fundamental mode spacing, frequency-doubled microwave is generated. At a low RF driven power of 2.8 dBm, tunable microwave outputs ranging from 15 GHz to 33 GHz are obtained with 2-GHz locking range. The phase noise and frequency stability of the generated microwave signal are also investigated. The proposed scheme requires much lower RF driven power and can be a viable choice for situations where high power and high frequency RF signal is not available.

  13. Three-dimensional imaging of skin melanoma in vivo by dual-wavelength photoacoustic microscopy.

    PubMed

    Oh, Jung-Taek; Li, Meng-Lin; Zhang, Hao F; Maslov, Konstantin; Stoica, George; Wang, Lihong V

    2006-01-01

    Dual-wavelength reflection-mode photoacoustic microscopy is used to noninvasively obtain three-dimensional (3-D) images of subcutaneous melanomas and their surrounding vasculature in nude mice in vivo. The absorption coefficients of blood and melanin-pigmented melanomas vary greatly relative to each other at these two optical wavelengths (764 and 584 nm). Using high-resolution and high-contrast photoacoustic imaging in vivo with a near-infrared (764-nm) light source, the 3-D melanin distribution inside the skin is imaged, and the maximum thickness of the melanoma (approximately 0.5 mm) is measured. The vascular system surrounding the melanoma is also imaged with visible light (584 nm) and the tumor-feeding vessels found. This technique can potentially be used for melanoma diagnosis, prognosis, and treatment planning. PMID:16822081

  14. Determination of refractive properties of fluids for dual-wavelength interferometry

    NASA Technical Reports Server (NTRS)

    Vikram, Chandra S.; Witherow, William K.; Trolinger, James D.

    1992-01-01

    Methods to calculate the refractive properties of solutions at different wavelengths are described by using experimental data at just two wavelengths. The properties are the refractive index and its gradients with temperature and concentration. Cauchy's equation is used to determine the refractive indices. The gradients versus temperature and concentration are then determined by using the Murphy-Alpert and the Lorentz-Lorenz equation, respectively. Finally, the particular case of a triglycine sulfate aqueous solution is considered as an example. The approach should provide the desired information for fringe analysis when dual-wavelength holographic or other interferometry is used for solving heat and mass transfer problems in fluids during crystal-growth experiments.

  15. 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

  16. Phase modulation system for dual wavelength difference spectroscopy of hemoglobin deoxygenation in tissues

    NASA Astrophysics Data System (ADS)

    Chance, Britton; Maris, Michael B.; Sorge, J.; Zhang, M. Z.

    1990-05-01

    Time resolved spectroscopy of tissue makes it possible to quantify tissue hemoglobin concentrations because of the direct measurement of the optical path length for photon migration. However, the laser system is bulky and unwieldy and impractical for clinical studies. Thus, the application of the more compact and efficient phase modulation technology well known for fluorescence lifetime studies to time resolved spectroscopy of tissue offers opportunities to simplify the methodology and in addition to afford continuous readout of tissue photon propagation. This paper describes single and dual wavelength systems operating at two wavelengths in the deep red region based upon a time-sharing system. These devices have noise levels in a 2 Hz bandwidth of less than 2 ps and drifts of < 1ps/min. Applications of the noninvasive devices include measurement of hemoglobin deoxygenation in brain and hemoglobin and myoglobin deoxygenation in human skeletal muscle and animal models. Numerous applications to medical and biological problems now become available.

  17. Dual-wavelength digital holography with a single low-coherence light source.

    PubMed

    Jeon, Sungbin; Cho, Janghyun; Jin, Ji-Nan; Park, No-Cheol; Park, Young-Pil

    2016-08-01

    We propose a measurement system using dual-wavelength digital holography and low-coherence interferometry to measure micro- and nanostructure surface heights. To achieve an extended axial step-measurement range and better image quality, a single light-emitting diode generates two distinct light sources by filtering different center wavelengths and narrower bandwidths. The system can measure surface profile with higher step heights and lower speckle noise in a large field-of-view. Using single-source lighting and a simple configuration, the method supports compactly configured and lower-cost surface-topography measurement systems applicable in various fields. Experimental results for a standard step sample verify the system's performance. PMID:27505804

  18. 1319 nm and 1356 nm dual-wavelength operation of diode-side-pumped Nd:YAG laser

    NASA Astrophysics Data System (ADS)

    Chen, Ming; Wang, Zhi-chao; Zhang, Shen-jin; Yang, Feng; Zhang, Feng-feng; Yuan, Lei; He, Miao; Li, Jia-jia; Zhang, Xiao-wen; Zong, Nan; Wang, Zhi-min; Bo, Yong; Peng, Qin-jun; Cui, Da-fu; Xu, Zu-yan

    2016-05-01

    We report the first demonstration on a diode-side-pumped quasi continuous wave (QCW) dual-wavelength Nd:YAG laser operating at 1319 nm and 1356 nm. The resonator adopts symmetrical L-shaped flat-flat structure working in a thermally near unstable cavity. By precise coating on the cavity mirrors, the simultaneous oscillation at 1319 nm and 1356 nm is delivered. A maximum dual-wavelength output power of 9.4 W is obtained. The beam quality factor M2 is measured to be 1.9.

  19. A cryogenically cooled Nd:YAG monolithic laser for efficient dual-wavelength operation at 1061 and 1064 nm

    NASA Astrophysics Data System (ADS)

    Cho, C. Y.; Tuan, P. H.; Yu, Y. T.; Huang, K. F.; Chen, Y. F.

    2013-04-01

    We experimentally explore the fluorescence spectra of the Nd:YAG (YAG: yttrium aluminum garnet) crystal at cryogenic temperatures to confirm the feasibility of dual-wavelength operation at 1061 and 1064 nm. Furthermore, a cryogenically cooled Nd:YAG crystal with coating to form a monolithic cavity is employed to investigate the performance of the dual-wavelength operation. At an incident pump power of 20 W, the output powers for each wavelength can simultaneously reach 6.0 W at the optimally balanced temperature of 152 K. The optimal temperature for balancing the output powers of the two wavelengths is experimentally determined as a function of the incident pump power intensity.

  20. 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.

  1. 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.)

  2. 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.

  3. Observation of dual-wavelength solitons and bound states in a nanotube/microfiber mode-locking fiber laser

    NASA Astrophysics Data System (ADS)

    Zeng, C.; Cui, Y. D.; Guo, J.

    2015-07-01

    We report on the experimental observation of dual-wavelength soliton and the phase-locked bound state in an all-fiber laser mode-locked by a carbon nanotubes/microfiber saturable absorber. The operation wavelengths are strongly dependent on the intracavity loss. By adjusting an attenuator to increase the intracavity loss, mode-locking wavelength shifts from 1557 to 1531 nm. With the appropriate pump power and intracavity loss, dual-wavelength solitons are achieved simultaneously. In addition, the phase-locked bound-state solitons are also observed at the two wavelengths. The pulse separation and phase difference are related to the first-order Kelly sidebands.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. Comparison of high repetition rate Q-switched 355nm ultraviolet lasers with EOM and AOM

    NASA Astrophysics Data System (ADS)

    Lu, Tingting; Li, Xiaolei; Zang, Huaguo; Zhu, Xiaolei

    2013-05-01

    Two kinds of Q-switched ultraviolet lasers using an acousto-optic modulator and an electro-optic modulator in the same cavity structure are demonstrated, with type I phase-matched LBO as second harmonic generation crystal and type II phase-matched LBO as third harmonic generation crystal. For acousto-optic Q-switched UV laser-a maximum average power of 6.3W with the shortest pulse width of 12 ns was obtained at the repetition rate of 22 kHz when the pump power reached 52.4 W. The optical conversion efficiency was up to 12%. Then we used a La3Ga5SiO14 crystal electro-optic modulator to replace the acousto-optic modulator. The 1.29W output power at 355nm wavelength was obtained at the repetition rate of 10 kHz when the pump power was increased to 20.4W, and the UV laser pulse width was as short as 9.6ns.The optical conversion efficiency was up to 6.3%.

  12. 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.

  13. 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.

  14. Dual-wavelength speckle-based SI-POF sensor for frequency detection and localization of remote vibrations

    NASA Astrophysics Data System (ADS)

    Pinzón, P. J.; Montero, D. S.; Tapetado, A.; Torres, J. C.; Vázquez, C.

    2016-05-01

    A novel speckle-based method for sensing frequency vibration is demonstrated in a reflective configuration. By employing a visible dual-wavelength approach it is also possible to determine the relative spatial location of the vibrations along a plastic optical fiber lead of 8 m in a distributed scheme.

  15. Influence of UV illumination on the cold temperature operation of a LiNbO(3) Q-switched Nd:YAG laser.

    PubMed

    Cole, Brian; Goldberg, Lew; King, Vernon; Leach, Jeff

    2010-04-26

    UV illumination of a lithium niobate Q-switch was demonstrated as an effective means to eliminate a loss in hold-off and associated prelasing that occurs under cold temperature operation of Q-switched lasers. This degradation occurs due to the pyroelectric effect, where an accumulation of charge on crystal faces results in a reduction in the Q-switch hold-off and a spatially variable loss of the Q-switch in its high-transmission state, both resulting in lowering of the maximum Q-switched pulse energy. With UV illumination, the resulting creation of photo-generated carriers was shown to be effective in eliminating both of these effects. A Q-switched Nd:YAG laser utilizing UV-illuminated LiNbO(3) was shown to operate under cold temperatures without prelasing or spatially variable loss. PMID:20588809

  16. Highly efficient passively Q-switched Tm,Ho:GdVO4 laser with kilowatt peak power

    NASA Astrophysics Data System (ADS)

    Du, Yanqiu; Yao, Baoquan; Liu, Wei; Cui, Zheng; Duan, Xiaoming; Ju, Youlun; Yu, Hong

    2016-04-01

    We present the experimental results on the laser characteristics of diode-pumped passively Q-switched Tm,Ho:GdVO4 and Tm,Ho:YVO4 lasers with a Cr2+:ZnS saturable absorber emitting in the 2-μm range. The Tm,Ho:GdVO4 laser exhibits better performance than the Tm,Ho:YVO4 laser. The minimum pulse duration of 32.7 ns is obtained with the pulse energy of 0.30 mJ, corresponding to the peak power of 9.1 kW. The slope efficiencies of continuous wave and passively Q-switched Tm,Ho:GdVO4 lasers are 49.9% and 36.5%, corresponding to the Q-switching efficiency of 70.2%.

  17. Variable energy, high peak power, passive Q-switching diode end-pumped Yb:LuAG laser

    NASA Astrophysics Data System (ADS)

    Kaskow, M.; Sulc, J.; Jabczynski, J. K.; Jelinkova, H.

    2014-12-01

    A new method to control the pulse energy in a passively Q-switched laser was proposed and experimentally verified for a diode-end-pumped Yb:LuAG laser. By changing the pumping area parameters it was possible to demonstrate generation of a wide range of output energies with a single laser configuration consisting of a gain medium, passive Q-switch and out-coupling mirror. The range of available energies 0.15-0.51 mJ with maximum peak power of 113 kW in simple Q-switching regime by means of a Cr:YAG saturable absorber and a Yb:LuAG gain medium pumped by a 20 W laser diode emitting at 968 nm was demonstrated.

  18. Passive Q-switching of an all-fiber laser induced by the Kerr effect of multimode interference.

    PubMed

    Fu, Shijie; Sheng, Quan; Zhu, Xiushan; Shi, Wei; Yao, Jianquan; Shi, Guannan; Norwood, R A; Peyghambarian, N

    2015-06-29

    A novel passively Q-switched all-fiber laser using a single mode-multimode-single mode fiber device as the saturable absorber based on the Kerr effect of multimode interference is reported. Stable Q-switched operation of an Er(3+)/Yb(3+) co-doped fiber laser at 1559.5 nm was obtained at a pump power range of 190-510 mW with the repetition rate varying from 14.1 kHz to 35.2 kHz and the pulse duration ranging from 5.69 μs to 3.86 μs. A maximum pulse energy of 0.8 μJ at an average output power of 27.6 mW was achieved. This demonstrates a new modulation mechanism for realizing Q-switched all-fiber laser sources. PMID:26191734

  19. On the Q-switched operation of Titanium:Sapphire lasers using a graphene-based saturable absorber mirror

    NASA Astrophysics Data System (ADS)

    Weigand, R.; Pinto, T.; Crespo, H. M.; Guerra, J. M.

    2015-09-01

    We numerically demonstrate Q-switched operation of Titanium:Sapphire lasers using mono and multilayer graphene, deposited on a totally reflecting end mirror as a saturable absorber. Output energies, pulse duration and repetition frequencies of the Q-switched pulse trains are given as a function of the pump intensity for different number of graphene layers and cavity lengths. For the geometries studied, pulses from 17 to 491 ns can be achieved, with energies ranging from 11 to 74 μJ and repetition rates from 0.06 to 2.5 MHz. These results can be useful for designing and building laser cavities for Q-switched and mode-locked operation in laser media with short lifetimes as Titanium:Sapphire.

  20. Environmental testing of a Q-switched Nd:YLF laser and a Nd:YAG ring laser

    NASA Technical Reports Server (NTRS)

    Robinson, D. L.

    1991-01-01

    A Q-switched Nd:YLF laser (model 110-02) and a Nd:YAG ring laser (model 120-04) from Lightwave Electronics were subjected to thermal and vibration tests similar to what can be expected during launch and flight on a spacecraft. Even though these lasers were not designed for space flight, environmental tests were performed to identify major design weaknesses. Laser performance (output power, energy, pulsewidth, lasing threshold etc.) were measured prior to and after thermal vibration tests. Average output power of the Q-switched laser degraded 15-20 percent after thermal tests and an additional 20-25 percent after vibration tests. Post diagnostic tests revealed that degradation of the Q-switched laser was due to misalignment of pump focusing optics and the laser cavity.

  1. An Nd:YLF laser Q-switched by a monolayer-graphene saturable-absorber mirror

    NASA Astrophysics Data System (ADS)

    Matía-Hernando, Paloma; Guerra, José Manuel; Weigand, Rosa

    2013-02-01

    We demonstrate Q-switched operation of a transversely diode-pumped Nd:YLF (yttrium lithium fluoride) laser using chemical vapour deposition-grown large-area monolayer graphene transferred to a dielectric saturable-absorber mirror (G-SAM). The resulting compact design operates at 1047 nm with 2.5 μs pulses in a 100% modulation Q-switch regime with an average and very stable output power of 0.5 W. Different cavity lengths have been employed and the results are compared against a theoretical model based on rate equations, evidencing the role of transverse pumping in the system. The model also reveals that monolayer graphene effectively leads to shorter and more powerful pulses compared to those with multilayer graphene. These results establish the potential of single-layer graphene for providing a reliable and efficient Q-switch mechanism in solid-state lasers.

  2. 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

  3. Single-frequency Q-switched erbium-doped fiber ring laser by combination of a distributed Bragg reflector laser and a Mach-Zender interferometer.

    PubMed

    Wang, Anting; Ming, Hai; Xie, Jianping; Chen, Xiyao; Lv, Liang; Huang, Wencai; Xu, Lixin

    2003-06-20

    A single-frequency Q-switched erbium-doped fiber ring laser is implemented for producing a single frequency with 25-Mhz laser linewidth, Q-switched pulses with a high peak power at 1557.5 mm. The single longitudinal mode is selected by a distributed Bragg reflector fiber laser, and a fiberoptic Mach-Zehnder interferometer acts as a Q-switch. The peak power and the average power of the Q-switched pulses vary with the repetition rate. PMID:12833955

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

    PubMed

    Klenner, Alexander; Keller, Ursula

    2015-04-01

    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. PMID:25968691

  5. Highly stable and tunable narrow-spacing dual-wavelength ytterbium-doped fiber using a microfiber Mach-Zehnder interferometer

    NASA Astrophysics Data System (ADS)

    Ahmad, Harith; Salim, Muhammad A. M.; Azzuhri, Saaidal R.; Harun, Sulaiman W.

    2016-02-01

    We describe a successful demonstration of highly stable and narrowly spaced dual-wavelength output via an ytterbium-doped fiber laser. A microfiber-based Mach-Zehnder interferometer and a tunable bandpass filter were both placed into the laser ring cavity for the purpose of ensuring a stable and narrowly spaced dual-wavelength output. Experimental results comprised three sets of dual-wavelength lasing output with wavelength spacing of 0.06, 0.09, and 0.22 nm, respectively, and side-mode suppression ratio of ˜50 dBm. A subsequent stability test provided evidence that maximum power and wavelength fluctuation were less than 0.8 dB and 0.01 nm, respectively, and thus, the obtained output was considered to be highly stable in dual-wavelength operation. The proposed system offers advantages of flexibility in dual-wavelength laser generation in addition to excellent reliability.

  6. Large energy laser pulses with high repetition rate by graphene Q-switched solid-state laser.

    PubMed

    Li, Xian-lei; Xu, Jin-long; Wu, Yong-zhong; He, Jing-liang; Hao, Xiao-peng

    2011-05-01

    We demonstrated that the graphene could be used as an effective saturable absorber for Q-switched solid-state lasers. A graphene saturable absorber mirror was fabricated with large and high-quality graphene sheets deprived from the liquid phase exfoliation. Using this mirror, 105-ns pulses and 2.3-W average output power are obtained from a passively Q-switched Nd:GdVO(4) laser. The maximum pulse energy is 3.2 μJ. The slope efficiency is as high as 37% approximating to 40% of the continue-wave laser, indicating a low intrinsic loss of the graphene. PMID:21643251

  7. 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)

  8. Q-switching and mode-locking in a diode-pumped frequency-doubled Nd : YAG laser

    SciTech Connect

    Donin, Valerii I; Yakovin, Dmitrii V; Gribanov, A V

    2012-02-28

    A new method for obtaining Q-switching simultaneously with mode-locking using one travelling-wave acousto-optic modulator in a frequency-doubled Nd : YAG laser cavity is described. Further shortening of output laser pulses (from 40 to 3.25 ps) is achieved by forming a Kerr lens in the frequency-doubling crystal. At an average power of {approx} 2 W and a Q-switching rate of 2 kHz, the peak power of the stably operating reached {approx} 50 MW.

  9. 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.

  10. Processing of Ni-based aero engine components with repetitively Q-switched Nd:YAG lasers

    NASA Astrophysics Data System (ADS)

    Bostanjoglo, Georg; Sarady, Istvan; Beck, Thomas; Weber, Horst

    1996-09-01

    Aircraft engine industry uses free running high power Nd:YAG lasers for drilling cooling holes into nickel base alloy turbine components. A cw-pumped, Q-switched, high beam quality laser system with 400W laser power is presented. The laser is used to trepan drilling of 1.6mm. Hastelloy X sheets and ceramic coated combustion chamber tubes of the same metal. Cylindrical shape, uniformity, and reproducibility are achieved with a trepan-like drilling setup. The heat load of the workpiece as well as the process time is considerably decreased by employing high-repetition Q-switched lasers.

  11. 1.4-MHz repetition rate electro-optic Q-switched Nd:YVO4 laser.

    PubMed

    Horiuchi, Ryusuke; Adachi, Koji; Watanabe, Goro; Tei, Kazuyoku; Yamaguchi, Shigeru

    2008-10-13

    An electro-optic (EO) deflector was used for Q-switching of a laser cavity with a Nd-doped yttrium vanadate (Nd:YVO(4)), enabling a short pulse width and a high peak power to be achieved at a high repetition rate of over 1 MHz. The EO deflector has a low optical loss during Q-switching without polarizers and can be used to form a short laser cavity. A repetition rate of 1.4 MHz with a pulse width of 39 ns was achieved. An output power of 2.7 W was obtained at a pump power of 6.5 W. PMID:18852782

  12. 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.

  13. Radially polarized and pulsed output from passively Q-switched Nd:YAG ceramic microchip laser.

    PubMed

    Li, Jian-lang; Ueda, Ken-ichi; Musha, Mitsuru; Zhong, Lan-xiang; Shirakawa, Akira

    2008-11-15

    For the first time, to the best of our knowledge, a radially polarized laser pulse was produced from a passively Q-switched Nd:YAG ceramic microchip laser with a piece of Cr4+:YAG crystal as the saturable absorber and multilayer concentric subwavelength grating as the polarization-selective output coupler. The averaged laser power reached 450 mW with a slope efficiency of 30.2%. The laser pulse had a maximum peak power of 759 W, a minimum pulse duration of 86 ns, and a 6.7 kHz repetition rate at 3.7 W absorbed pump power. The polarization degree of the radially polarized pulse was measured to be as high as 97.4%. Such a radially polarized laser pulse with a high peak power and a short width is important to numerous applications such as metal cutting. PMID:19015709

  14. 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. PMID:19015677

  15. 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.

  16. 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.

  17. Treatment of traumatic tattoo with the Q-switched Nd:YAG laser.

    PubMed

    Gorouhi, Farzam; Davari, Parastoo; Kashani, Mansour Nassiri; Firooz, Alireza

    2007-12-01

    Traumatic tattoos are undesirable tattoos caused by different foreign bodies such as fireworks' particles, sand, metals, glass, gunpowder, asphalt, dust, or petroleum products embedded forcefully in the dermis. We report the case of a 54-year-old man who presented with sand and asphalt tattooing on his face following a bomb explosion 15 years ago. Q-switched Nd:YAG laser at a wavelength of 1064 nm with a spot size of 4 mm and a fluence of 7.96 J/cm(2) were applied to treat the patient. The patient tolerated the treatment very well. Most of the blue dots became whitened immediately after the procedure and remained almost clear after a 6-month follow-up. PMID:18236246

  18. Passively Q-switched Nd:YAG ceramic microchip laser with azimuthally polarized output

    NASA Astrophysics Data System (ADS)

    Li, J.-L.; Lin, D.; Zhong, L.-X.; Ueda, K.; Shirakawa, A.; Musha, M.; Chen, W.-B.

    2009-10-01

    A passively-Q-switched neodymium-doped yttrium aluminum garnet (Nd:YAG) ceramic microchip laser was demonstrated to emit azimuthally polarized beam bus using a chromium-doped YAG (Cr4+:YAG) crystal as saturable absorber and a multilayer concentric subwavelength grating as polarization-selective output coupler. The laser's output power reached 512 mW with an initial slope efficiency of nearly 60%, and the pulse had 1.15-kW peak power with 40-ns duration and 11-kHz repetition rate at 3.9-W absorbed pump power. The laser beam's polarization degree was 97.6%. The thermal lensing effect in Nd:YAG microchip remained as a problem to be solved.

  19. Diode-side-pumped, passively Q-switched Yb:LuAG laser

    NASA Astrophysics Data System (ADS)

    Kaskow, Mateusz; Galecki, Lukasz; Jabczynski, Jan K.; Skorczakowski, Marek; Zendzian, Waldemar; Sulc, Jan; Nemec, Michal; Jelinkova, Helena

    2015-10-01

    A high-gain, diode-side-pumped Yb:LuAG slab laser was designed and investigated for use at room temperature. Pumping occurred from a fast-axis collimated 2D laser diode stack emitting at a wavelength of 970 nm, with 0.8 J over a duration of 0.8 ms. The pump scheme, which enabled efficient mode matching and high gain, was analysed and experimentally verified for different dopant levels. An energy of 100 mJ with 23% slope efficiency in a near fundamental mode was achieved in the free-running regime. A peak power of 2.5 MW and a pulse energy of 10.1 mJ were demonstrated in passive Q-switching by means of a Cr:YAG saturable absorber with 39% initial transmission. The study defined the indications for optimizing such a system.

  20. Segment side-pumped Q-switched Nd:YAG laser.

    PubMed

    Wang, Wei; Fu, Chen; Hu, Zhenyue; Zhao, Qin; Gong, Mali

    2012-04-10

    In the design of conduction-cooled lasers, a side-pumped configuration is an attempt to solve the space conflict between pump and heat removal. The pump radiation always competes with the heat removal and mechanical support device for the lateral surface of a laser rod. This space conflict can be addressed by a segment side-pumped configuration in which circular laser diode arrays and heat-conducting rod holders alternate periodically along the length of the laser rod. This scheme permitted 11 Hz operation of a 190 mJ Q-switched laser at the wavelength of 1064 nm without the use of liquid cooling for both the laser rod and laser diode arrays and the corresponding optical-optical conversion efficiency of 23.1%. Thus, it has great potential to be used in compact and miniature laser systems. PMID:22505168

  1. 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.

  2. 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. PMID:15813276

  3. 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%.

  4. 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.

  5. Novel gas sensor combined active fiber loop ring-down and dual wavelengths differential absorption method.

    PubMed

    Zhao, Yanjie; Chang, Jun; Ni, Jiasheng; Wang, Qingpu; Liu, Tongyu; Wang, Chang; Wang, Pengpeng; Lv, Guangping; Peng, Gangding

    2014-05-01

    A novel active fiber loop ring-down gas sensor combined with dual wavelengths differential absorption method is proposed. Two Distributed Feedback Laser Diodes (DFB LDs) with different wavelengths are employed. One LD whose wavelength covered with the absorption line of target gas is used for sensing. Another LD whose wavelength is centered outside the absorption line is used for reference. The gas absorption loss can be obtained by differencing the reference signal and sensing signal. Compared with traditional method of one wavelength employed, it can eliminate the influence of the cavity loss variety and photoelectric device drift in the system efficiently. An Erbium Doped Fiber Amplifier (EDFA) with Automatic Gain Control (AGC) is used to compensate the loss of the light in the ring-down cavity, which will increase the cavity round trips and improve the precision of gas detection. And two fiber Bragg gratings (FBGs) are employed to get rid of amplified spontaneous emission (ASE) spectrum noise as filters. The calibrating ethyne samples of different concentrations are measured with a 65 mm long gas cell in order to evaluate the effect of reference. The results show the relative deviation is found to be less than ± 0.4% of 0.1% ethyne when a certain additional loss from 0 to 1.2dB is introduced to the cavity and the relative deviation of measured concentration is less than ± 0.5% over 24 hours. PMID:24921822

  6. An interference signal processing method for displacement measurement by dual wavelength and single grating

    NASA Astrophysics Data System (ADS)

    Wang, Guochao; Yan, Shuhua; Yang, Dongxing; Zhou, Weihong; Xie, Xuedong

    2011-12-01

    Displacement measurement by dual wavelength and single grating integrates the single grating diffraction theory and the heterodyne interference theory. By taking advantage of the two theories, it solves the contradiction between large range and high precision in grating displacement measurement quite well. In order to obtain nanometer resolution and nanometer precision, high-power subdivision of interference fringe must be realized accurately. According to phase demodulation theory for heterodyne interference signal, a digital phase measuring method is proposed by combining frequency-mixing technique and pulse-filling method. The whole signal processing part, which is based on FPGA and PLL, has been designed to realize the integer period measurement and high-powered subdivision of the decimal phase. Through experiments, it is validated that the phase range is [-180°, 180°], and the phase measurement resolution and the phase precision are above 0.03° and 0.1°, respectively. Moreover, the displacement measurement resolution and the displacement precision, corresponding to the phase indexes, are 0.167nm and 0.556nm, respectively.

  7. 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.

  8. 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.

  9. Continuous-wave single-frequency laser with dual wavelength at 1064 and 532 nm.

    PubMed

    Zhang, Chenwei; Lu, Huadong; Yin, Qiwei; Su, Jing

    2014-10-01

    A continuous-wave high-power single-frequency laser with dual-wavelength output at 1064 and 532 nm is presented. The dependencies of the output power on the transmission of the output coupler and the phase-matching temperature of the LiB(3)O(5) (LBO) crystal are studied. An output coupler with transmission of 19% is used, and the temperature of LBO is controlled to the optimal phase-matching temperature of 422 K; measured maximal output powers of 33.7 W at 1064 nm and of 1.13 W at 532 nm are obtained with optical-optical conversion efficiency of 45.6%. The laser can be single-frequency operated stably and mode-hop-free, and the measured frequency drift is less than 15 MHz in 1 min. The measured Mx2 and My2 for the 1064 nm laser are 1.06 and 1.09, respectively. The measured Mx2 and My2 for the 532 nm laser are 1.12 and 1.11, respectively. PMID:25322220

  10. 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.

  11. Cloud image retrieval and characterization using ground-based dual-wavelength radar at millimeter wavelengths

    NASA Astrophysics Data System (ADS)

    Colon-Diaz, Nivia; Cruz-Pol, Sandra L.; Sekelsky, Stephen M.

    2003-04-01

    Characterization of the microphysical properties of non-precipitating stratus clouds including their suspended-water droplet size distribution and the cloud's liquid water content are estimated in this work. The dual wavelength ratio, DWR, and the differential extinction, DE, were computed at two millimeter frequencies, 33 GHz and 95 GHz, using UMass Cloud Profiling Radar System (CPRS) to estimate the drop size distribution. Data from radiosonde observations (Raob) is used as input in a recently calibrated model for estimation of the gaseous attenuation at Ka.-band and Liebe's model at W-band. Integrated specific humidity from a radiometer is used to constrain the radiosonde specific humidity. The radar reflectivity is corrected to take into account the effect of the wind speed, the difference of beamwidth at both frequencies and the difference in sampled range cells. Radar reflectivity and ancillary data are combined to obtain the differential extinction and the estimated cloud's liquid water density. Profiles of the processed data, such as DE, the DWR and the cloud's liquid water density are presented. Cloud's water density and radar reflectivity were used for the size distribution estimation of the suspended water droplets and the median drop diameter.

  12. Dual-wavelength digital holography: single-shot shape evaluation using speckle displacements and regularization.

    PubMed

    Bergström, Per; Khodadad, Davood; Hällstig, Emil; Sjödahl, Mikael

    2014-01-01

    This paper discusses the possibility of evaluating the shape of a free-form object in comparison with its shape prescribed by a CAD model. Measurements are made based on a single-shot recording using dual-wavelength holography with a synthetic wavelength of 1.4 mm. Each hologram is numerically propagated to different focus planes and correlated. The result is a vector field of speckle displacements that is linearly dependent on the local distance between the measured surface and the focus plane. From these speckle displacements, a gradient field of the measured surface is extracted through a proportional relationship. The gradient field obtained from the measurement is then aligned to the shape of the CAD model using the iterative closest point (ICP) algorithm and regularization. Deviations between the measured shape and the CAD model are found from the phase difference field, giving a high precision shape evaluation. The phase differences and the CAD model are also used to find a representation of the measured shape. The standard deviation of the measured shape relative the CAD model varies between 7 and 19 μm, depending on the slope. PMID:24513998

  13. Remote picometer fiber Bragg grating demodulation using a dual-wavelength source.

    PubMed

    Clement, Juan; Torregrosa, Germán; Maestre, Haroldo; Fernández-Pousa, Carlos R

    2016-08-10

    We report on the self-referenced, intensity-based, remote and passive interrogation of a fiber Bragg grating (FBG) for point sensing, by use of a reconfigurable dual-wavelength source composed of a tunable wavelength and subsequent suppressed-carrier, electro-optic amplitude modulation. The demodulation procedure is based on the measurement of the reflected power at two different wavelengths within the FBG spectral response. The grating was interrogated by use of conventional spectral analysis, and also after 32.9 km of single-mode fiber using a dispersive incoherent optical Fourier-domain reflectometry technique. Both procedures provide picometer resolution in the determination of Bragg wavelength shifts at a comparatively similar scan time (∼1  s) and received power (-16  dBm). The main limitations in each interrogation scheme have been identified. These results show the feasibility of interrogation systems incorporating relatively simple frequency combs at a calibrated, and eventually reconfigurable, wavelength grid with an, at least, similar performance to that of commercial FBG interrogators. PMID:27534505

  14. 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.

  15. Reduction of implantation shadowing effect by dual-wavelength exposure photo process

    NASA Astrophysics Data System (ADS)

    Gu, Yiming; Chou, Dyiann; Lee, Sang Yun; Roche, William R.; Sturtevant, John L.

    2003-06-01

    As transistor engineering continues to well below 100 nm length devices, ion implantation process tolerances are making these formerly "non-critical" lithography levels more and more difficult. In order to minimize the channeling effect and to obtain a controllable profile of dopant, an angled implantation is often required. However, a shadow area of resist pattern is always accompanied with an angled implantation. This shadowing effect consumes silicon real estate, and reduces the line edge placement (LEP) tolerances. Therefore, methodologies to reduce the shadowing effect in angled implantation become a critical consideration not only for device engineering but also for photolithography. Based on the model analysis, simulation and experiments, this paper presents an effective novel process utilizing dual-wavelength exposure (DWE) to reduce the shadowing effect. The DWE process is realized by two consecutive exposures for an I-line resist with a DUV stepper/scanner and an I-line stepper. The process leverages the high absorption coefficient of novalak-DNQ resist at 248 nm, and results in a tunable post-develop resist thickness to minimize the shadowing effect. It is effective in satisfying the junction requirements and also is helpful in minimizing the number of photoresists in a manufacturing fab. A repeatable resist profile and an excellent CD uniformity across wafer also indicated that the DWE is a potentially manufacturable process.

  16. 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.

  17. Self-Q-switched Cr:LiCAF laser near 800 nm

    NASA Astrophysics Data System (ADS)

    Beyatli, Ersen; Sennaroglu, Alphan; Demirbas, Umit

    2013-03-01

    Self-Q-switching (SQS) of lasers enable the generation of Q-switched pulses from simple laser cavities without using any additional saturable absorbers or active modulators. Earlier studies have reported SQS in ruby, Nd:YAG, and Cr:LiSAF lasers. However, these systems were mostly flashlamp pumped and required cooling of the crystal and/or misalignment of the laser cavity for the observation of SQS. In this presentation, for the first time to our knowledge, we report SQS operation of a Cr:LiCAF laser. SQS was achieved in an astigmatically compensated x-cavity containing only a Cr:LiCAF crystal that was end-pumped with a 140-mW continuous-wave (cw) diode at 660 nm. During regular cw operation, the laser produced a diffraction-limited beam with 50 mW of output power and had a spectral width of 0.5 nm near 795 nm. SQS operation of the Cr:LiCAF laser could be initiated by fine adjustment of the separation between the curved mirrors of the cavity and was observed at several mirror separations within the stability range of the resonator. During SQS operation, the laser generated saw-tooth-shaped pulses with 20-30 microsecond duration in the 780-800 nm wavelength range, at repetition rates between 10 and 30 kHz. SQS operation was further accompanied with a decrease in the output power to the 30-45 mW range. In this regime, the output beam became multimode and spectral broadening up to 12.5 nm (FWHM) was observed.

  18. 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.

  19. 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.

  20. 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. PMID:26406500

  1. Q-switched erbium-doped fiber ring laser with piezoelectric transducer-based PS-CFBG

    NASA Astrophysics Data System (ADS)

    Wu, Liangying; Pei, Li; Wang, Jianshuai; Li, Jing; Ning, Tigang; Liu, Shuo

    2016-09-01

    In this letter, a Q-switched erbium-doped fiber ring laser (EDFRL) with piezoelectric transducer (PZT)-based phase shift chirped fiber Bragg grating (PS-CFBG) has been proposed and demonstrated first. As known, the phase shift can be induced and wiped periodically by applying a modulation signal on the PZT. This makes it possible for the PZT-based PS-CFBG to be used in Q-switched EDFRL. To verify the performance of this Q-switched EDFRL system, some theoretical analyses and experiments have been performed. It is found that, when the PZT is modulated by a signal with frequencies of 1 and 2 kHz, pulse widths of the Q-switched pulse train are 19.8 μs and 15.6 μs, respectively. Besides, the corresponding pulse energies are 1.16 μJ (1 kHz) and 1.91 μJ (2 kHz) with a pump power of 90 mW.

  2. Continuously-tunable, narrow-linewidth, Q-switched Cr:LiSAF laser for lidar applications

    SciTech Connect

    Early, J.W.; Lester, C.S.; Quick, C.R.; Tiee, J.J.; Shimada, T.; Cockroft, N.J.

    1995-02-01

    A continuously-tunable, narrow-linewidth, flashlamp-pumped, Q-switched Cr:LiSAF laser has been developed (energy: 30 mJ, pulsewidth: 40 ns, linewidth:<2 GHz) and was used successfully for the DIAL(differential absorption lidar) measurements of atmospheric water vapor and LIF lidar for the remote detection of metal oxide fluorescence.

  3. 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. PMID:25549817

  4. 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.

  5. 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.

  6. Continuously-tunable, narrow-linewidth, Q-switched Cr:LiSAF laser for lidar applications

    SciTech Connect

    Shimada, Tsutomu; Early, J.W.; Lester, C.S.; Quick, C.R.; Tiee, J.J.; Cockroft, N.J.

    1994-10-01

    A continuously-tunable, narrow-linewidth, flashlamp-pumped, Q-switched Cr:LiSAF laser has been developed (energy: 30 mJ, pulsewidth: 40 ns, linewidth: <2 GHz) and was used successfully for the DIAL (differential absorption lidar) measurements of atmospheric water vapor.

  7. Spectroscopic, thermal and cw dual-wavelength laser characteristics of Nd:LaF3 single crystal

    NASA Astrophysics Data System (ADS)

    Hong, Jiaqi; Zhang, Lianhan; Li, Jing; Wang, Zhaowei; He, Jingliang; Zhang, Peixiong; Wang, Yaqi; Hang, Yin

    2016-03-01

    A Nd-doped LaF3 crystal was grown by Czochralski method, and the rocking curves of (0 0 2) and (1 1 0) diffraction planes show good crystallinity quality of the as-grown crystal. Room-temperature fluorescence spectrum and transmittance spectrum of Nd:LaF3 crystal were investigated, both indicating probable dual-wavelength emissions at ∼1.04 μm and ∼1.06 μm. The thermal diffusivity and thermal conductivity of Nd:LaF3 crystal were detailed studied. Cw dual-wavelength laser operation of Nd:LaF3 single crystal at 1040 nm and around 1065 nm with LD pumping was demonstrated. A maximum output power of 302 mW was obtained with a slope efficiency of about 18.5% with respect to the pump power. The results of our study indicate the Nd:LaF3 crystal a promising laser crystal.

  8. 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.

  9. 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%. PMID:26393759

  10. Focusing dual-wavelength surface plasmons to the same focal plane by a far-field plasmonic lens.

    PubMed

    Venugopalan, Priyamvada; Zhang, Qiming; Li, Xiangping; Kuipers, L; Gu, Min

    2014-10-01

    In this Letter, we demonstrate the nanoscale focusing of surface plasmons (SPs) at two different wavelengths to the same focal plane by a far-field plasmonic lens both numerically and experimentally. The far-field plasmonic lens, which consists of an annular slit and a concentric groove and is capable of focusing dual-wavelength SPs to the same focal plane, is characterized by a scanning near-field optical microscope under both linearly and radially polarized illuminations. The demonstrated far-field plasmonic lens can provide immense opportunities for on-chip photonic applications, including dual-wavelength-based super-resolution imaging and ultra-high-density optical data storage. PMID:25360974

  11. Dual-wavelength Y-branch distributed Bragg reflector diode laser at 785 nanometers for shifted excitation Raman difference spectroscopy.

    PubMed

    Maiwald, Martin; Eppich, Bernd; Fricke, Jörg; Ginolas, Arnim; Bugge, Frank; Sumpf, Bernd; Erbert, Götz; Tränkle, Günther

    2014-01-01

    A dual-wavelength Y-branch distributed Bragg reflector (DBR) diode laser at 785 nm is presented as an excitation light source for shifted excitation Raman difference spectroscopy (SERDS). The monolithic device was realized with deeply etched surface DBR gratings using one-step epitaxy. An optical output power of 140 mW was obtained in continuous-wave (CW) operation for each laser cavity, with emission wavelengths of the device at 784.50 and 785.12 nm. A spectral width of the laser emission of 30 pm (0.5 cm(-1)), including 95% of optical power, was measured. The mean spectral distance of both excitation lines is 0.63 nm (10.2 cm(-1)) over the whole operating range. Raman experiments using polystyrene as the test sample and ambient light as the interference source were carried out and demonstrate the suitability of the dual-wavelength diode laser for SERDS. PMID:25061785

  12. High-power dual-wavelength external-cavity diode laser based on tapered amplifier with tunable terahertz frequency difference.

    PubMed

    Chi, Mingjun; Jensen, Ole Bjarlin; Petersen, Paul Michael

    2011-07-15

    Tunable dual-wavelength operation of a diode laser system based on a tapered diode amplifier with double-Littrow external-cavity feedback is demonstrated around 800 nm. The two wavelengths can be tuned individually, and the frequency difference of the two wavelengths is tunable from 0.5 to 5.0 THz. An output power of 1.54 W is achieved with a frequency difference of 0.86 THz, the output power is higher than 1.3 W in the 5.0 THz range of frequency difference, and the amplified spontaneous emission intensity is more than 20 dB suppressed in the range of frequency difference. To our knowledge, this is the highest output power from a dual-wavelength diode laser system operating with tunable terahertz frequency difference. PMID:21765489

  13. Effect of pump wave reflections on the excitation of a dual-wavelength vertical-cavity surface-emitting laser

    SciTech Connect

    Morozov, M. Yu.; Morozov, Yu. A. Popov, V. V.

    2009-03-15

    The effect of pump wave reflections on the carrier generation rate and uniformity of carrier population in quantum wells (QWs) of a dual-wavelength vertical-cavity surface-emitting laser has been numerically analyzed. The laser's active region has been described within a mathematical model allowing any number of QWs and arbitrary distribution of carrier generation rate. It is shown that the optimal arrangement of blocking layers in the active region of a dual-wavelength vertical-cavity surface-emitting laser allows one to obtain a very uniform QW population. It is established that pump wave reflections significantly affect the local carrier generation rate and, therefore, the distribution of excited carriers in the laser structure.

  14. Dual wavelength laser-induced damage threshold measurements of alumina/silica and hafnia/silica ultraviolet antireflective coatings.

    PubMed

    Mrohs, Marius; Jensen, Lars; Günster, Stefan; Alig, Thimotheus; Ristau, Detlev

    2016-01-01

    An approach for the measurement of the laser-induced damage threshold with two wavelengths combined was made while testing antireflective coatings for the wavelengths 266 and 532 nm. Samples were made of Al2O3/SiO2 and HfO2/SiO2 ion beam sputtered films. The results show that adding radiation of a second wavelength might lead to a significant reduction of the threshold. The damage morphology of single and dual wavelength tests is very similar and does not suggest an altered damage mechanism. Further investigations indicated that the dual wavelength threshold is a function of the temporal delay of the two pulses. PMID:26835628

  15. Improved Large Signal Analysis of the Dual-Wavelength Linearization Technique of Optically Phase-Modulated Analog Microwave Signals

    NASA Astrophysics Data System (ADS)

    Taher Abuelma'Atti, Muhammad

    2009-10-01

    This paper presents simple closed-form expressions, in terms of the ordinary Bessel functions, for the amplitudes of the third- and fifth-order intermodulation products of the dual-wavelength linearized phase modulated link for any scenario of the microwave driving voltage. The results obtained for a microwave driving voltage comprising equal-amplitude two- and three-tones show that the third-order intermodulation can be minimized for values of phase modulation depth less than 0.2 over a relatively wide range of the ratio between the powers in the TM and TE waves of the link. Using these results it is possible to adjust the phase modulation depth and/or the ratio between the powers of the TM and TE waves to achieve a dual-wavelength linearized phase modulated link with a predetermined intermodulation performance.

  16. Tunable and switchable dual-wavelength erbium-doped fiber laser based on in-line tapered fiber filters

    NASA Astrophysics Data System (ADS)

    Tong, Zheng-rong; Yang, He; Cao, Ye

    2016-07-01

    A tunable and switchable dual-wavelength erbium-doped fiber laser (EDFL) based on all-fiber single-mode tapered fiber structure has been demonstrated. By adjusting the variable optical attenuator (VOA), the laser can be switched between the single-wavelength mode and the dual-wavelength mode. When the temperature applied on the tapered fiber structure varies, the pass-band varies and the wavelength of the output laser shifts correspondingly. When the temperature changes from 30 °C to 180 °C, the central wavelength of the EDFL generated by branch A shifts from 1 550.7 nm to 1 560.3 nm, while that of branch B shifts from 1 530.8 nm to 1 540.4 nm, indicating the wavelength interval is tunable. These advantages enable this laser to be a potential candidate for high-capacity wavelength division multiplexing systems and mechanical sensors.

  17. 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.

  18. 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.

  19. 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

  20. Minimally Invasive Treatment of Infrabony Periodontal Defects Using Dual-Wavelength Laser Therapy.

    PubMed

    Al-Falaki, Rana; 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

  1. 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

  2. Real-time measurement of dual-wavelength laser-induced fluorescence spectra of individual aerosol particles.

    PubMed

    Huang, Hermes C; Pan, Yong-Le; Hill, Steven C; Pinnick, Ronald G; Chang, Richard K

    2008-10-13

    We report the development of an in-situ aerosol detection system capable of rapidly measuring dual-wavelength laser-induced fluorescence spectra of single particles on the fly using a single spectrometer and a single 32-anode photomultiplier array. We demonstrate the capability of this system with both reference samples and outdoor air. We present spectra from separate excitation wavelengths from the same particle that demonstrate improved discrimination capability compared with only using one excitation wavelength. PMID:18852760

  3. High-speed dual-wavelength demultiplexing and detection in a monolithic superlattice p-i-n waveguide detector array

    NASA Technical Reports Server (NTRS)

    Larsson, A.; Andrekson, P. A.; Andersson, P.; Eng, S. T.; Salzman, J.

    1986-01-01

    High-speed (1 Gbit/x) dual-wavelength demultiplexing and detection in a monolithic linear array of superlattice p-i-n photodetectors in a waveguide configuration is demonstrated. A crosstalk attenuation of 28 dB was achieved between two digital transmission channels with an interchannel wavelength spacing of 30 nm. The device performance is a result of an enhanced electroabsorption due to the quantum-confined Stark effect in the superlattice p-i-n diodes.

  4. 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.

  5. Single-/dual-wavelength switchable and tunable compound-cavity erbium-doped fiber laser with super-narrow linewidth

    NASA Astrophysics Data System (ADS)

    Feng, Ting; Yan, Feng-ping; Liu, Shuo

    2016-03-01

    A single-/dual-wavelength switchable and tunable erbium-doped fiber laser (EDFL) with super-narrow linewidth has been proposed and experimentally demonstrated at room temperature. The fiber laser is based on a compound cavity simply composed of a ring main cavity and a two-ring subring cavity (TR-SC). Regardless of single- or dual-wavelength operation, the EDFL could always work well in single-longitudinal-mode (SLM) state at every oscillating wavelength. In dual-wavelength operation, the spacing could be tuned from 0 nm to 4.83 nm. In single-wavelength operation, the EDFL could lase at a fixed wavelength of 1 543.65 nm or another wavelength with a tunable range of 4.83 nm. The super-narrow linewidths of 550 Hz and 600 Hz for two wavelengths are obtained. The proposed EDFL has potential applications in microwave/terahertz-wave generation and high-precision distributed fiber optical sensing.

  6. A calibrated dual-wavelength infrared thermometry approach with non-greybody compensation for machining temperature measurements

    NASA Astrophysics Data System (ADS)

    Hijazi, A.; Sachidanandan, S.; Singh, R.; Madhavan, V.

    2011-02-01

    We report the development of a new approach for determining temperatures using the dual-wavelength infrared thermometry technique, which does not presume greybody behaviour and compensates for the spectral dependence of emissivity. This approach is based on Planck's radiation equation and explicitly accounts for the wavelength-dependent response of the IR detector and the losses occurring due to each of the elements of the IR imaging system that affect the total radiant energy sensed in different spectral bands. A thorough calibration procedure is utilized to determine a compensation factor for the spectral dependence of emissivity, which is referred to as the non-greybody compensation factor (NGCF). Calibration and validation experiments are carried out on Aluminum 6061-T6 targets with two different surface roughnesses. Results show that this alloy does not exhibit greybody behaviour, even though the two spectral bands used were relatively close to each other, and that the spectral dependence of emissivity is influenced by the surface finish. It is found that non-greybody behaviour of low emissivity surfaces can lead to significant systematic error in dual-wavelength IR thermometry. The inclusion of the NGCF eliminates the systematic error caused by the invalidity of greybody assumption and thus improves the accuracy of the measurements. Non-greybody-compensated dual-wavelength thermography is used to measure the chip temperature along the tool-chip interface during orthogonal cutting of Al 6061-T6 and sample results at three different cutting speeds are presented.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. Spectral and temporal control of Q-switched solid-state lasers using intracavity MEMS

    NASA Astrophysics Data System (ADS)

    Paterson, A.; Bauer, R.; Li, R.; Clark, C.; Lubeigt, W.; Uttamchandani, D.

    2016-03-01

    Active control of the spectral and temporal output characteristics of solid-state lasers through use of MEMS scanning micromirrors is presented. A side-pumped Nd:YAG laser with two intracavity scanning micromirrors, enabling Q-switching operation with controllable pulse duration and pulse-on-demand capabilities, is investigated. Changing the actuation signal of one micromirror allows a variation of the pulse duration between 370 ns and 1.06 μs at a pulse repetition frequency of 21.37 kHz and average output power of 50 mW. Pulse-on-demand lasing is enabled through actuation of the second micromirror. To our knowledge this is the first demonstration of the use of multiple intracavity MEMS devices as active tuning elements in a single solid-state laser cavity. Furthermore, we present the first demonstration of control over the output wavelength of a solid-state laser using a micromirror and a prism in an intracavity Littman configuration. A static tilt actuation of the micromirror resulted in tuning the output wavelength of an Yb:KGW laser from 1024 nm to 1031.5 nm, with FWHM bandwidths between 0.2 nm and 0.4 nm. These proof-of-principle demonstrations provide the first steps towards a miniaturized, flexible solid-state laser system with potential defense and industrial applications.

  12. 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. PMID:27409193

  13. High-power widely tunable Q-switched thulium fiber lasers

    NASA Astrophysics Data System (ADS)

    Li, Feng; Zhu, Haibin; Zhang, Yong

    2015-09-01

    Based on acousto-optic modulation and grating diffraction, a high-power-pulsed ~2 μm laser with a wide tunable wavelength is realized in double-clad Tm fibers. A maximum average output power of 35.6 W is obtained with the 6 m fiber, which also provides a maximum pulse energy and peak power of 1.58 mJ and 5.6 kW, respectively. For the 6 m fiber length, a  >20 W average power can be achieved over a 100 nm wavelength tuning range. Shortening the fiber length to 2 m and 1 m can extend the wavelength tuning range further to shorter spectral regimes (1892 nm and 1881 nm). Short fiber length also narrows the Q-switched pulse duration to 90 ns. This kind of high-power, high-pulse-energy, widely tunable, and narrow-bandwidth ~2 μm fiber lasers can find wide applications in various regions.

  14. 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. PMID:27464082

  15. Development of monolith Nd:YAG /Cr+4:YAG passively Q-switched microchip laser

    NASA Astrophysics Data System (ADS)

    Izhnin, Ihor; Vakiv, Mykola; Izhnin, Aleksandr; Syvorotka, Igor; Ubizskii, Sergii; Syvorotka, Ihor, Jr.

    2005-09-01

    The main features of passively Q-switched microchip lasers development are considered. The active medium of laser is an epitaxial structure combining an epitaxial layer of saturable absorber Cr4+:Y3Al5O12 (Cr:YAG) grown on substrate of generating crystal Nd:YAG by liquid phase epitaxy. The modulator layer has an initial optical absorption of 36 cm-1 at wavelength of lasing (1064 nm). The epitaxial layer grown on unworking side was mechanically removed and this substrate side was optically polished. The other one was processed precisely to needed thickness. The cavity's mirrors were deposited by electron beam technique directly on each side of the structure to form a rugged, monolithic resonator. Diode laser Model ATC-C4000 with lasing wavelength 808 nm provided the CW end pumping. The output pulses parameters were investigated by means of test bench consisting of photoelectric transducer FEK-15 and Digital Phosphor Oscilloscope TDS 5052B. The obtained laser parameter are as follows: pulse width (FWHM) about 1.3 ns, repetition rate 5.5 kHz, average output power about 10 mW, pulse energy 1.0 μJ, pick power 1.2 kW. The possible solutions for laser parameter improving and optimization are discussed.

  16. 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.

  17. 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. PMID:22565344

  18. 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.

  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. Analysis of mode wavefront characteristics for passively Q-switched slab Nd:YAG laser

    NASA Astrophysics Data System (ADS)

    Zhang, Xiang; Wang, Jie; Hu, Zhiqiu; Su, Likun

    2016-01-01

    The eigenmode of resonators with symmetric circular mirrors used in solid-state lasers is investigated. Further experiments on output beam quality on a passive Q-switched zigzag slab Nd:YAG laser have been performed by adopting Hartmann-Shack and Zernike-mode reconstruction methods. By the means of peak-valley and root mean square errors of the wavefront distribution, each order of Zernike aberrations are achieved accurately. Moreover, the distribution of circle energy in the far-field and corresponding beam evaluation factors can also be obtained by further calculation. Experimental results indicate that the wavefront aberration is mainly concentrated in the first 10 Zernike aberrations, which mainly includes the defocus Z3, the low-order astigmatism Z5, the coma aberration Z6, and the spherical aberration Z10, because of the crystal thermal effect and the intracavity phase perturbation. The method can be used to further analyze the compensation of intracavity aberration and optimal design for such lasers.

  1. Water content contribution in calculus phantom ablation during Q-switched Tm:YAG laser lithotripsy

    NASA Astrophysics Data System (ADS)

    Zhang, Jian J.; Rajabhandharaks, Danop; Xuan, Jason Rongwei; Wang, Hui; Chia, Ray W. J.; Hasenberg, Tom; Kang, Hyun Wook

    2015-12-01

    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.

  2. 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.

  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. 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

    2015-12-01

    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. PMID:26662067

  5. High resolution laser micro sintering / melting using q-switched and high brilliant laser radiation

    NASA Astrophysics Data System (ADS)

    Exner, H.; Streek, A.

    2015-03-01

    Since the discovery of selective laser sintering/melting, numerous modifications have been made to upgrade or customize this technology for industrial purposes. Laser micro sintering (LMS) is one of those modifications: Powders with particles in the range of a few micrometers are used to obtain products with highly resolved structures. Pulses of a q-switched laser had been considered necessary in order to generate sinter layers from the micrometer scaled metal powders. LMS has been applied with powders from metals as well as from ceramic and cermet feedstock's to generate micro parts. Recent technological progress and the application of high brilliant continuous laser radiation have now allowed an efficient laser sintering/melting of micrometer scaled metal powders. Thereby it is remarkable that thin sinter layers are generated using high continuous laser power. The principles of the process, the state of the art in LMS concerning its advantages and limitations and furthermore the latest results of the recent development of this technology will be presented. Laser Micro Sintering / Laser Micro Melting (LMM) offer a vision for a new dimension of additive fabrication of miniature and precise parts also with application potential in all engineering fields.

  6. 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.

  7. Microphysical Retrievals Over Stratiform Rain Using Measurements from an Airborne Dual-Wavelength Radar-Radiometer

    NASA Technical Reports Server (NTRS)

    Meneghini, Robert; Kumagai, Hiroshi; Wang, James R.; Iguchi, Toshio; Kozu, Toshiaki

    1997-01-01

    The need to understand the complementarity of the radar and radiometer is important not only to the Tropical Rain Measuring Mission (TRMM) program but to a growing number of multi-instrumented airborne experiment that combine single or dual-frequency radars with multichannel radiometers. The method of analysis used in this study begins with the derivation of dual-wavelength radar equations for the estimation of a two-parameter drop size distribution (DSD). Defining a "storm model" as the set of parameters that characterize snow density, cloud water, water vapor, and features of the melting layer, then to each storm model there will usually correspond a set of range-profiled drop size distributions that are approximate solutions of the radar equations. To test these solutions, a radiative transfer model is used to compute the brightness temperatures for the radiometric frequencies of interest. A storm model or class of storm models is considered optimum if it provides the best reproduction of the radar and radiometer measurements. Tests of the method are made for stratiform rain using simulated storm models as well as measured airborne data. Preliminary results show that the best correspondence between the measured and estimated radar profiles usually can be obtained by using a moderate snow density (0.1-0.2 g/cu cm), the Maxwell-Garnett mixing formula for partially melted hydrometeors (water matrix with snow inclusions), and low to moderate values of the integrated cloud liquid water (less than 1 kg/sq m). The storm-model parameters that yield the best reproductions of the measured radar reflectivity factors also provide brightness temperatures at 10 GHz that agree well with the measurements. On the other hand, the correspondence between the measured and modeled values usually worsens in going to the higher frequency channels at 19 and 34 GHz. In searching for possible reasons for the discrepancies, It is found that changes in the DSD parameter Mu, the radar

  8. 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.

  9. The Effect of Anterior Stromal Puncture Using Q-Switched Nd:YAG Laser on Corneal Wound Healing

    PubMed Central

    Hamdy Abdelaziz, Mohamed; Fouad Ghoneim, Dina; Abdelkawi Ahmed, Salwa; Taher, Ibraheim Mohyeldin; Abdel- Salam, Ahmed Medhat

    2014-01-01

    Introduction: Recurrent corneal erosion occurs when the wounded corneal epithelium failed to adhere to the underlying stroma. Therefore, this work aimed to assess the effect of treatment of corneal injury using Q- switched Nd:YAG laser. Method: Twenty one New Zealand male rabbits weighing 2-2.5 kg and 3 months old were classified into three main groups. The control group: did not received any treatment (n=3 rabbits). The rest of the animals (n= 18 rabbits), corneal epithelium was injured by syringe needle and blade 15 and divided into:(A) Normal healing group: which was divided into three subgroups (n=3 rabbits each), and the animals were left for normal healing for1 day, 1 week, and 4 weeks respectively, (B) Laser treated group: divided into three subgroups (n=3 rabbit seach) and subjected to anterior stromal puncture using Q-switched Nd: YAG laser on corneal sub-epithelium or superficial stroma, and the animals were left for 1 day, 1 week, and 4 weeksrespectively. After the demonstrated periods, the corneas were isolated for estimation of total protein content, sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), total antioxidative capacity (TAC), total oxidative capacity (TOC) and oxidative stress index (OSI). Results: The present results of corneal total protein showed increment in the percentage change in normal healed groups after 1 day, 1 week and 4 weeks by values of 93%, 68% and 39%. In Q-switched Nd: YAG laser treated group the results showed better improvement in corneal protein than normal healed group with percentage changes of 58%, 29%, and 7.5% respectively. In SDS- PAGE, a protein band at 110 KD appeared in the migrating epithelium for both normal healed group and Q-switched Nd:YAG laser treated group with changes in the peaks intensities at middle and low molecular weight regions. Moreover, after 4 weeks the peak at 110 KD disappeared in the wounded epithelium treated with Q-switched Nd:YAG. After four weeks, the OSI in laser

  10. 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)

  11. 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.

  12. Generation of Q-switched pulse by Bi2Se3 topological insulator in Yb:KGW laser

    NASA Astrophysics Data System (ADS)

    Hu, Mengting; Liu, Jinghui; Tian, Jinrong; Dou, Zhiyuan; Song, Yanrong

    2014-11-01

    A Q-switched Yb:KGW solid-state laser using topological insulator Bi2Se3 as a saturable absorber was demonstrated experimentally for the first time. The Bi2Se3 saturable absorber was fabricated in a film on a highly reflective mirror. By inserting this into a Yb:KGW laser, the Q-switched operation was obtained. The highest average output power was 439.4 mW and the corresponding repetition rate, pulse width and pulse energy were 166.7 kHz, 1.6 μs and 2.64 μJ, respectively. To our knowledge, this is the highest output power among topological insulator-modulated lasers with topological insulator absorbers.

  13. 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. PMID:22941006

  14. Integrated electro-optic Q switching in a domain-inverted Nd:LiTaO3 laser

    NASA Astrophysics Data System (ADS)

    Abedin, Kazi Sarwar; Tsuritani, Takehiro; Sato, Manabu; Ito, Hiromasa; Shimamura, Kiyoshi; Fukuda, Tsuguo

    1995-10-01

    We report a novel integrated Q -switched laser constructed from a bulk domain-inverted single Nd:LiTaO3 crystal that combines the laser gain and the electro-optic effect. The Q of the cavity is controlled electro-optically by exploitation of the deflection that occurs at the boundary of two oppositely directed domains under the application of an electric field. The integrated Q -switching element, with dimensions of 4.1mm \\times 4.6 mm \\times 1 mm , generates 22-ns pulses at 1.08 mu m with a peak power of 64 W and an operating voltage of \\similar 600 V . The output is seen to be completely free from prelasing or afterpulsing.

  15. Q-switched Tm3+-doped fiber laser with a micro-fiber based black phosphorus saturable absorber

    NASA Astrophysics Data System (ADS)

    Wang, Yazhou; Li, Jianfeng; Han, Lian; Lu, Rongguo; Hu, Yunxiao; Li, Zhuo; Liu, Yong

    2016-06-01

    We report a passively Q-switched Tm3+-doped fiber laser using a black phosphorus deposited micro-fiber (BPDMF) as a saturable absorption (SA) device for the first time. The BPDMF prepared by depositing black phosphorus (BP) on the micro-fiber waist with heat convention effect and optical tweezer effect has a measured modulation depth of 40.2% and a nonsaturable loss of 55.9%. By employing this device in an all-fiber ring cavity, a stable Q-switched pulse train at 1948 nm was achieved with a repetition rate from 12.5 to 28.1 kHz and a pulse width from 15.1 to 5.6 μs, respectively.

  16. 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

  17. A stable 2 μm passively Q-switched fiber laser based on nonlinear polarization evolution

    NASA Astrophysics Data System (ADS)

    He, X.; Luo, A.; Lin, W.; Yang, Q.; Yang, T.; Yuan, X.; Xu, S.; Xu, W.; Luo, Z.; Yang, Z.

    2014-08-01

    A passively Q-switched thulium-doped fiber (TDF) laser based on the nonlinear polarization evolution technique was demonstrated with the central wavelength of 1898.4 nm. With the increasing pump power, the pulse repetition frequency of the Q-switched TDF laser from 87.6 to 110.1 kHz was achieved, while the corresponding pulse duration was changed from 1171 to 785.7 ns. The power instability of the TDF laser was measured to be about ±1.5% during 8 h. In addition, the mode-locked phenomenon was also observed in our all-fiber TDF laser by carefully adjusting the polarization controllers.

  18. 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

  19. Watt-level passively Q-switched heavily Er3+-doped ZBLAN fiber laser with a semiconductor saturable absorber mirror

    NASA Astrophysics Data System (ADS)

    Shen, Yanlong; Wang, Yishan; Luan, Kunpeng; Huang, Ke; Tao, Mengmeng; Chen, Hongwei; Yi, Aiping; Feng, Guobin; Si, Jinhai

    2016-05-01

    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.

  20. CONTROL OF LASER RADIATION PARAMETERS: Passive Q switching of a neodymium laser by a Cr4+ : YAG crystal switch

    NASA Astrophysics Data System (ADS)

    Il'ichev, Nikolai N.; Gulyamova, E. S.; Pashinin, Pavel P.

    1997-11-01

    Theoretical and experimental investigations were made of passive Q switching of a neodymium laser by a Cr4+ : YAG switch. Analytic expressions were derived for estimating the output energy of the TEM00 mode of a passively Q-switched laser from the known parameters of the Cr4+ : YAG switch, of the active element, and of the cavity. The adopted description makes it possible to cover the range from generation of the first spike of a free-running transient to generation of a giant pulse. An experimental study was made of the dependence of the output energy on the cavity parameters, on the material of the active element (in this investigation it was Nd :YAG and Cr, Nd : GSGG), and on the angle of rotation of the Cr4+ : YAG switch. The experimental results obtained agreed to within 30% with calculations.

  1. Cr{sup 4+}:YAG as passive Q-switch and Brewster plate in a pulsed Nd:YAG laser

    SciTech Connect

    Shimony, Y.; Burshtein, Z.; Kalisky, Y.

    1995-10-01

    The authors demonstrate the performance of a Nd:YAG laser, passively Q-switched with a Cr{sup 4+}:YAG plate, which plays the double role of a passive Q-switch ad a Brewster plate. The Brewster plate configuration contributes an intracavity loss of approximately 3.2 {times} 10{sup {minus}3} cm{sup {minus}1} along the cavity length. Losses contributed by the active Cr{sup 4+} ions in the plate relate to their excited state absorption. A freshly measured transmission saturation curve of Cr{sup 4+}:YAG suggests a ground state absorption cross section {sigma}{sub gs} = (8.7 {+-} 0.8) {times} 10{sup {minus}19} cm{sup 2}, and an excited state absorption cross section {sigma}{sub es} = (2.2 {+-} 0.2) {times} 10{sup {minus}19} cm{sup 2} of the Cr{sup 4+} ions at {lambda} = 1,064 nm.

  2. Q-switched operation of a femtosecond-laser-inscribed Yb:YAG channel waveguide laser using carbon nanotubes.

    PubMed

    Choi, Sun Young; Calmano, Thomas; Kim, Mi Hye; Yeom, Dong-Il; Kränkel, Christian; Huber, Günter; Rotermund, Fabian

    2015-03-23

    We demonstrate a diode-pumped femtosecond-laser-inscribed Yb:YAG channel waveguide laser, Q-switched by using single-walled carbon nanotubes (SWCNTs) near 1029 nm. We used saturable absorber mirrors (SAMs) fabricated by depositing SWCNTs on three different output couplers. Best performance of the 9.3-mm-long ultra-compact Q-switched waveguide laser is obtained with an output coupling transmission of 20%. In this case, a maximum average output power of 60 mW with a corresponding pulse energy of 37.7 nJ and a pulse duration of 88 ns at 1.59-MHz repetition rate were achieved. The highest pulse energy of 39.2 nJ and the shortest pulse duration of 78 ns were obtained with 30% and 10% output couplers, respectively. PMID:25837137

  3. Highly efficient passively Q-switched Yb:YAG microchip lasers under high intensity laser-diode pumping

    NASA Astrophysics Data System (ADS)

    Dong, J.; Wang, G. Y.; Cheng, Y.

    2013-03-01

    A highly efficient Cr4+:YAG passively Q-switched Yb:YAG microchip laser has been demonstrated at room temperature by high-brightness single-emitter laser-diode pumping. The maximum average output power of 1.53 W was obtained at the absorbed pump power of 3.5 W. The optical-to-optical efficiency was 44% with respect to the absorbed pump power. Laser pulses with a pulse width of 2.9 ns, pulse energy of 11.3 μJ, and peak power of 3.9 kW were obtained. The high pump power intensity from a high-brightness single-emitter laser-diode plays an important role in the alleviation of thermal effects and the efficient performance of Cr4+:YAG passively Q-switched Yb:YAG microchip lasers.

  4. High-energy resonantly diode-pumped Q-switched Er:YAG laser at 1617 nm

    NASA Astrophysics Data System (ADS)

    Yu, Zhenzhen; Wang, Mingjian; Hou, Xia; Chen, Weibiao

    2016-04-01

    We report high-energy linearly polarized operation of an Er:YAG laser at 1617 nm, resonantly pumped by quasi-continuous-wave 1470-nm laser diodes. A U-shape resonator incorporating two 0.25 at.% Er:YAG rods and an acousto-optic Q-switch was employed. Polarized output with pulse energy of 20.5 mJ and pulse width of 52 ns at a 50 Hz repetition rate was obtained. At the maximum output energy, the output beam quality M 2 was approximately 1.02 and 1.03 in horizontal and vertical directions, respectively. To the best of our knowledge, this polarized pulse energy is the highest ever reported for a directly diode-pumped Q-switched Er:YAG laser operating at 1617 nm.

  5. Q-switched mode-locked and azimuthally polarized Nd:GdVO4 laser with semiconductor saturable absorber mirror

    NASA Astrophysics Data System (ADS)

    Hong, Kun-Guei; Hung, Bi-Jin; Lin, Shih-Ting; Wei, Ming-Dar

    2016-06-01

    A Q-switched mode-locked Nd:GdVO4 laser with azimuthal polarization was generated using a semiconductor saturable absorber mirror. On the basis of the birefringence of the laser crystal inducing different equivalent lengths for ordinary and extraordinary rays, beams were azimuthally polarized around the edge of a stable cavity region. At a pump power of 9 W, the repetition rate and width for the Q-switched envelope were 318 kHz and 0.91 µs, and the mode-locked pulse repetition rate and pulse width were 455 MHz and 65 ps, respectively. The degree of polarization was controllable up to 95.4 ± 1.4%.

  6. Watt-level passively Q-switched heavily Er(3+)-doped ZBLAN fiber laser with a semiconductor saturable absorber mirror.

    PubMed

    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 Er(3+)-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

  7. Passively Q-switched erbium-doped fiber laser at C-band region based on WS₂ saturable absorber.

    PubMed

    Ahmad, H; Ruslan, N E; Ismail, M A; Reduan, S A; Lee, C S J; Sathiyan, S; Sivabalan, S; Harun, S W

    2016-02-10

    We demonstrate a Q-switched erbium-doped fiber laser using tungsten disulfide (WS₂) as a saturable absorber. The WS₂ is deposited onto fiber ferrules using a drop-casting method. Passive Q-switched pulses operating in the C-band region with a central wavelength of 1560.7 nm are successfully generated by a tunable pulse repetition rate ranging from 27.2 to 84.8 kHz when pump power is increased from 40 to 220 mW. At the same time, the pulse width decreases from a maximum value of 3.84 μs to a minimum value of 1.44 μs. The signal-to-noise ratio gives a stable value of 43.7 dB. The modulation depth and saturation intensity are measured to be 0.99% and 36.2  MW/cm², respectively. PMID:26906366

  8. S-band Q-switched fiber laser using molybdenum disulfide (MoS2) saturable absorber

    NASA Astrophysics Data System (ADS)

    Ahmad, Harith; Afiq Ismail, Mohd; Suthaskumar, Muneswaran; Cheak Tiu, Zian; Wadi Harun, Sulaiman; Zamani Zulkifli, Mohd; Samikannu, Sathiyan; Sivaraj, Sivabalan

    2016-03-01

    In this letter, a molybdenum disulfide (MoS2) saturable absorber (SA) is fabricated using a simple drop cast method to generate Q-switched fiber laser operating in the S-band region (1460 nm-1530 nm). The MoS2 solution was prepared using the liquid phase exfoliation (LPE) method where MoS2 crystals were added into dimethylformamide (DMF) solvent and subsequently sonicated and centrifuged. They were then repeatedly dripped onto fiber ferrules and dried in an oven. The resultant Q-switched fiber laser starts with some physical disturbance when the pump power was set at 40 mW and continues to operate until the pump power reaches 120 mW. The resultant repetition rate varies with pump power between 27.17 to 101.17 kHz while the changes in pulse widths are from 3.0 to 1.4 μs.

  9. Lithium niobate Q-switch to prevent pre-lasing of high gain lasers operating over a wide temperature range

    NASA Astrophysics Data System (ADS)

    Jundt, Dieter H.; MacKay, Peter E.

    2015-02-01

    Because of its ease of growth and large electro-optic effect, lithium niobate is the preferred choice for Q-switching mobile lasers. Temperature-induced pyro-electric charges however may lead to premature lasing. We manufactured and characterized temperature-stable LN Q-switch. A thermo-chemical anneal was performed creating a conductive material layer 0.5mm thick with increased conductivity. While this increases optical insertion loss by a few percent, this is tolerable in high gain lasers. We present details of treatment, the surface charge creation and dissipation mechanism and the setup used to assess the cold-performance used to demonstrate improved charge dissipation when compared to untreated crystals.

  10. Nanosecond pulses in a THz gyrotron oscillator operating in a mode-locked self-consistent Q-switch regime.

    PubMed

    Alberti, S; Braunmueller, F; Tran, T M; Genoud, J; Hogge, J-Ph; Tran, M Q; Ansermet, J-Ph

    2013-11-15

    An experimental study of a nanosecond pulsed regime in a THz gyrotron oscillator operating in a self-consistent Q-switch regime has been carried out. The gyrotron is operated in the TE(7,2) transverse mode radiating at a frequency of 260.5 GHz. The 5 W nanosecond pulses are obtained in a self-consistent Q-switch regime in which the cavity diffraction quality factor dynamically varies by nearly 2 orders of magnitude on a subnanosecond time scale via the nonlinear interaction of different mode-locked frequency-equidistant sidebands. The experimental results are in good agreement with numerical simulations performed with the TWANG code based on a slow time scale formulation of the self-consistent time-dependent nonlinear wave particle interaction equations. PMID:24289692

  11. 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.

  12. 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. PMID:23913058

  13. Passively Q-switched erbium-doped fiber laser using Fe3O4-nanoparticle saturable absorber

    NASA Astrophysics Data System (ADS)

    Bai, Xuekun; Mou, Chengbo; Xu, Luxi; Wang, Shaofei; Pu, Shengli; Zeng, Xianglong

    2016-04-01

    We experimentally demonstrate passively Q-switched erbium-doped fiber laser (EDFL) operation using a saturable absorber (SA) based on Fe3O4 nanoparticles (FONPs). As a type of transition metal oxide, the FONPs have a large nonlinear optical response and fast response time. The FONP-based SA possesses a modulation depth of 8.2% and nonsaturable absorption of 56.6%. Stable passively Q-switched EDFL pulses with an output pulse energy of 23.76 nJ, a repetition rate of 33.3 kHz, and a pulse width of 3.2 µs were achieved when the input pump power was 110 mW. The laser features a low threshold pump power of ∼15 mW.

  14. A continuous-wave and passively Q-switched Nd:LaGGG laser at 937 nm

    NASA Astrophysics Data System (ADS)

    Li, Z.-Y.; Ying, H.-Y.; Yang, H.; He, J.-L.

    2013-10-01

    A diode-end-pumped continuous-wave (CW) and passively Q-switched Nd:LaGGG (GGG: gadolinium gallium garnet) laser at about 937 nm was demonstrated for the first time. The maximum CW output power of 540 mW was obtained with the optical-optical conversion efficiency of 3.2% and the slope efficiency of 4.4%. A V3+:YAG (yttrium aluminum garnet) saturable absorber with the initial transmission of 97% was used for the passive Q-switching regime. The shortest pulse width was achieved as 500 ns with the pulse repetition rate of 96 kHz. The corresponding single-pulse energy and pulse peak power were determined as 1.56 μJ and 3.12 W, respectively.

  15. 183 WTEM00 mode acoustic-optic Q-switched MOPA laser at 850 kHz.

    PubMed

    Liu, Qiang; Yan, Xingpeng; Fu, Xing; Gong, Mali; Wang, Dongsheng

    2009-03-30

    We report a high-power, high-repetition-rate TEM00 mode MOPA laser using acoustic-optic Q-switching. Seed laser from the dual-end- pumped Nd:YVO4 oscillator was scaled up to 183.5 W average power at 850 kHz after behind amplified by the four-stage power amplifiers. The stable Q-switching operation worked at different pulse repetition rate from 60 kHz to 850 kHz while the pulse duration increased from 12.8 ns to 72 ns. The beam quality was near diffraction-limit with M2 factors measured as M2x = 1.28 and M2y = 1.21. In CW operation, 195 W TEM00 mode output was achieved corresponding to the total optical-optical efficiency of 44.7% and the absorbed pump power to output power efficiency of 53.3% respectively. PMID:19333332

  16. 145-watt high beam quality bidirectional voltage-supplied Q-switched Nd∶YAG master oscillator power amplifier laser

    NASA Astrophysics Data System (ADS)

    Bai, Zhenxu; Long, Mingliang; Chen, Liyuan; Chen, Meng; Li, Gang

    2013-02-01

    We present a high compact structure laser diode (LD) side-pumped all-solid-state Q-switched master oscillator power amplifier (MOPA) laser system with high beam quality. Bidirectional voltage-supplied Q-switched and MOPA technologies were introduced in the design. An in-center wavelength of 1064 nm with pulse width adjustability from 5 to 18 ns was obtained at the repetition rate of 500 Hz. Through multistage Nd∶YAG amplifiers at the pulse width of 6 ns, the oscillator was scaled up to 145 W and the corresponding peak power reached 48.3 MW with single pulse energy fluctuation less than 0.45% in 1 h operation.

  17. 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. PMID:18795004

  18. 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.

  19. 47 W, 6 ns constant pulse duration, high-repetition-rate cavity-dumped Q-switched TEM(00) Nd:YVO(4) oscillator.

    PubMed

    McDonagh, Louis; Wallenstein, Richard; Knappe, Ralf

    2006-11-15

    We report on a cavity-dumped Q-switched TEM(00) Nd:YVO(4) oscillator offering a unique combination of high power, constant short pulse duration, and high repetition rate, suppressing the gain dependence of pulse duration in classical Q-switched oscillators. Its performance is compared with that of the same oscillator operated in a classical Q-switched regime, demonstrating the much higher peak powers achievable with this technique, especially at high repetition rates. Up to 31 W of 532 nm green light was generated by frequency doubling in a noncritical phase matched LBO crystal, corresponding to 70% conversion efficiency. PMID:17072404

  20. Numerical Study of Passive Q Switching of a Tm:YAG Laser with a Ho:YLF Solid-State Saturable Absorber

    NASA Astrophysics Data System (ADS)

    Kuo, Yen-Kuang; Chang, Yi-An

    2003-03-01

    In a previous work [Appl. Phys. Lett. 65 , 3060 (1994) we experimentally demonstrated that passive ]Q switching of a 2017-nm, flashlamp-pumped Tm,Cr:YAG laser with a Ho:YLF saturable absorber could be obtained with an internal focusing lens. We numerically investigate the optical performance of the Ho:YLF Q -switched Tm:YAG laser system by solving the coupled rate equations. The simulation results indicate that the results obtained numerically are in good agreement with those obtained experimentally. With typical laser configuration, a Q -switched laser pulse of 35 mJ in 30 ns is obtained.

  1. Actively Q-switched 2.9 μm Ho(3+)Pr(3+)-doped fluoride fiber laser.

    PubMed

    Hu, Tomonori; Hudson, Darren D; Jackson, Stuart D

    2012-06-01

    We report an efficient Q-switched Ho(3+)Pr(3+)-doped fluoride fiber laser, producing a peak power of 77 W, with pulse width of 78 ns. A slope efficiency of 20% with respect to the launched pump power was achieved. A TeO(2) acousto-optic modulator allowed continuous tunability of the pulse repetition frequency from 40 to 300 kHz. PMID:22660149

  2. 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.

  3. Diode pumped Nd:YAG laser with active Q-switching and mode locking for hole drilling

    NASA Astrophysics Data System (ADS)

    Solokhin, S. A.; Sirotkin, A. A.; Garnov, S. V.

    2011-06-01

    A diode-pumped Nd:YAG laser operating with active-passive Q-switch mode locking, has been developed. The acousto-optic repetition train was one kilohertz with generated pulse train widths 65 ns, single pulse widths 200 ps and an average power of 6.5 W. Improvement of efficiency of small diameter deep holes laser drilling in different materials was studied.

  4. Melanin Index in Assessing the Treatment Efficacy of 1064 nm Q Switched Nd-Yag Laser in Nevus of Ota

    PubMed Central

    Sethuraman, Gomathy; Sharma, Vinod K; Sreenivas, Vishnubhatla

    2013-01-01

    Background: Q-switched neodymium-yttrium aluminium-garnet (Q switched Nd-Yag) laser has been used in the treatment of nevus of Ota in all skin types with variable success rate. Data with an objective assessment parameter to this laser treatment is lacking. Objective: To evaluate the utility of melanin index in assessing the treatment response and also determine the efficacy and safety of the Q-switched Nd-Yag laser (1064-nm) in the treatment of nevus of Ota in Fitzpatrick skin types IV and V. Materials and Methods: A total of 35 patients treated with Nd-Yag laser were studied. The objective improvement (pigment clearance) was determined by melanin index from two fixed points: A1, 2 cm below the pupil at the mid pupillary line (when the gaze is fixed); A2, the most prominent part of zygoma. The melanin index in these two areas was recorded as M1 and M2, respectively. The subjective clinical improvement was determined by the physician and the patient global assessment score. Results: The mean baseline melanin indices M1 and M2 were 59.54 ± 9.72 and 59.02 ± 9.16, respectively. At the last visit the mean M1 and M2 decreased to 53.8 ± 8.55 (P < 0.001) and 54.13 ± 6.01 (P < 0.001), respectively. Patient and the physician global assessment score showed that 26 (74.3%) and 20 (57.14%) patients, respectively, had >50% pigment clearance. Conclusion: The melanin index, a simple non-invasive parameter is useful in assessing the treatment response more objectively. The 1064-nm Q-switched Nd-Yag laser offers good improvement in patients with nevus of Ota in darker skin types IV/V. PMID:24470713

  5. Removal of tattoos by q-switched laser: variables influencing outcome and sequelae in a large cohort of treated patients.

    PubMed

    Bencini, Pier Luca; Cazzaniga, Simone; Tourlaki, Athanasia; Galimberti, Michela Gianna; Naldi, Luigi

    2012-12-01

    OBJECTIVE To analyze variables affecting the treatment course and prognosis of Q-switched laser tattoo removal. DESIGN Observational prospective cohort study. SETTING The study was carried out in a referral center for surgery and laser surgery in Milan. PARTICIPANTS Of 397 consecutive patients initially enrolled from January 1, 1995, to December 31, 2010, 352 patients (201 men and 151 women; median age, 30 years) were included in the analysis. INTERVENTION All patients were treated by the same investigator with Q-switched 1064/532-nm Nd:YAG laser and Q-switched 755-nm alexandrite laser according to tattoo colors. Laser sessions were scheduled at 6-week or longer intervals. MAIN OUTCOME MEASURES Successful therapy was defined as removal of the tattoo, with no adverse effects other than transient hypochromia or darkening. RESULTS The cumulative rates of patients with successful tattoo removal were 47.2% (95% CI, 41.8%-52.5%) after 10 sessions and 74.8% (95% CI, 68.9%-80.7%) after 15 sessions. Smoking, the presence of colors other than black and red, a tattoo larger than 30 cm2, a tattoo located on the feet or legs or older than 36 months, high color density, treatment intervals of 8 weeks or less, and development of a darkening phenomenon were associated with a reduced clinical response to treatment. CONCLUSIONS To our knowledge, this study is the first to formally assess prognostic factors for effective tattoo removal by Q-switched laser. Several variables influence response rates and should be considered when planning tattoo removal treatments. PMID:22986584

  6. Passively Q-switched a-cut Nd:GdVO4 self-Raman laser with Cr:YAG

    NASA Astrophysics Data System (ADS)

    Peng, J. Y.; Zheng, Y.; Shi, Y. X.; Shen, J. P.

    2012-10-01

    A passively Q-switched a-cut Nd:GdVO4 self-Raman solid-state laser with Cr:YAG saturable absorber was firstly demonstrated. The first Stokes at 1173 nm was successfully obtained. At the maximum incident pump power, the pulse width was about 1.8 ns and the repetition rate was 27.5 kHz. 586.5 nm yellow laser output was also realized by use of an LBO frequency doubling crystal.

  7. 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.

  8. 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)

  9. Diode-pumped high-efficiency high-brightness Q-switched ND:YAG slab laser.

    PubMed

    Armandillo, E; Norrie, C; Cosentino, A; Laporta, P; Wazen, P; Maine, P

    1997-08-01

    A high-efficiency diode-pumped Q-switched Nd:YAG oscillator designed for future spaceborne applications has been demonstrated and characterized. The laser is based on a side-pumped slab geometry and uses an unstable resonator with a radially variable-reflectivity output coupler. The laser provides an output pulse energy of 100 mJ at a 100-Hz repetition rate, with a near-diffraction-limited beam and an overall electrical optical efficiency exceeding 6%. PMID:18185784

  10. Comprehensive study of electro-optic and passive Q-switching in solid state lasers for altimeter applications

    NASA Astrophysics Data System (ADS)

    Bhardwaj, Atul; Agrawal, Lalita; Pal, Suranjan; Kumar, Anil

    2006-12-01

    Laser Science and Technology Center (LASTEC), Delhi, is developing a space qualified diode pumped Nd: YAG laser transmitter capable of generating 10 ns pulses of 30 mJ energy @ 10 pps. This paper presents the results of experiments for comparative studies between electro-optic and passively Q-switched Nd: YAG laser in a crossed porro prism based laser resonator. Experimental studies have been performed by developing an economical bench model of flash lamp pumped Nd: YAG laser (rod dimension, \

  11. Passively Q-switched high-energy all-solid-state holographic Nd:YAG laser with a multiloop cavity

    NASA Astrophysics Data System (ADS)

    Lebedev, V. F.; Pogoda, A. P.; Boreysho, A. S.; Smetanin, S. N.; Fedin, A. V.

    2015-02-01

    A high-energy, high-beam-quality laser based on a single Nd:YAG rod with laser diode side-pumping and multiloop self-adaptive reciprocal cavity is presented. The optimized laser cavity geometry allowed to change the laser oscillation from single 200-ns self-Q-switched pulse followed by low-intensity free-running lasing to repetitive high-intensive pulses by periodically writing and erasing holographic gain gratings in the active Nd:YAG medium. The intensified self-Q-switching pulse train oscillation was realized by the interaction with a diffusely reflecting target placed in the focal plane of a lens at the laser output. Effects of shortening of the repetitive laser pulses down to 70-ns duration, stabilization of the pulse repetition period (~ 5 μs), and mode-locking temporal modulation of the pulses were observed. The use of a passive F2-:LiF Q-switch resulted in stable giant pulse train oscillation with total output energy of up to 0.43 J, individual pulse energy of 50 mJ, and its peak power of 4 MW at the individual pulse duration of 12 ns.

  12. 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.

  13. Maximum value of the pulse energy of a passively Q-switched laser as a function of the pump power.

    PubMed

    Li, Jianlang; Ueda, Ken-ichi; Dong, Jun; Musha, Mitsuru; Shirakawa, Akira

    2006-07-20

    The finite recovery time Ts of the bleached absorber is presented as one of the possible mechanisms accounting for the increase-maximum-decrease in pulse energy E with the pumping rate Wp in cw-pumped passively Q-switched solid-state lasers, by analytically evaluating the sign of the derivative partial differentialE/ partial differentialWP. The results show that, in the low pump regime (T>Ts, T is the interpulse period), the initial population density ni remains constant, the final population density nf decreases with Wp, and this results in a monotonic increase of E with Wp. In the high pump regime (TQ switched by a Cr4+:YAG absorber is demonstrated to confirm this model. The theoretical model is also applied to the analysis of three previously reported passive Q switching solid-state [Nd:GdVO4, Nd+:LaSc3(BO3)4 (Nd+:LSB), and Nd:YAG] lasers experiments. PMID:16826274

  14. Intracavity KTP OPO pumped by a doubly Q-switched laser with AOM and a monolayer graphene saturable abosorber

    NASA Astrophysics Data System (ADS)

    Qiao, Junpeng; Zhao, Jia; Yang, Kejian; Zhao, Shengzhi; Li, Guiqiu; Li, Dechun; Li, Tao; Qiao, Wenchao; Chu, Hongwei

    2015-12-01

    An intracavity KTiOPO4 (KTP) optical parametric oscillator (IOPO) pumped by a doubly Q-switched YVO4/Nd:YVO4 laser with an acousto-optic modulator (AOM) and a monolayer graphene saturable absorber has been realized for the first time. The average output power, the pulse duration, single pulse energy and the peak power of signal light versus incident pump power have been measured. At an incident pump power of 11.7 W and an AOM repetition rate of 10 kHz, the shortest pulse duration of 1.24 ns was obtained, corresponding to a single pulse energy of 9.5 μJ and a peak power of 7.9 kW. In comparison, the doubly IOPO (DIOPO) pumped by doubly Q-switched laser with AOM and graphene saturable absorber can generate pulses with narrower pulse width and higher peak power than the singly IOPO (SIOPO) pumped only by AOM Q-switched laser.

  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. 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.

  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. PMID:25832207

  18. A low jitter single frequency Q-switched laser from solid state to optical fiber configuration

    NASA Astrophysics Data System (ADS)

    Wu, Frank F.

    2013-03-01

    This paper will get to the bottom of the mechanism of a superior inject seeding technology, and take it even further, from the solid state laser into the fiber laser configuration. This low jitter, single frequency Q-switched solid state laser with precisely controllable firing time was realized, developed and reported previously, in which the oscillator can output energy of near 100 mJ and the master oscillator power amplifier (MOPA) reaches the output energy of 300 mJ, operating at a wavelength of 1064 nm, with a pulse width of 10 ns and in near single transversal mode. Comparing two existing commercial techniques, ramp-and-fire and pulse-to-pulse buildup time reduction, this report presents a full understanding of using a CW transformed injection seeding method in which this technique is immune to mechanical vibration or thermal expansion, and it is able to precisely control the high peak energy launching time within a nanosecond jitter and achieve single frequency operation at the same time. It is carefully observed that the CW seeding mechanism is similar but not equivalent to a pulsed seeding with pulse width shorter or equal to the ring cavity length. The advantage of the realized regime is that in stable laser operation there is no need to adjust the slave cavity length to match the seeded light longitudinal mode. Therefore, the extremely strict mechanical requirement can be relaxed. It is found that the slave laser frequency follows exactly to the injected seeded laser's frequency which can also provide frequency tuning, control and locking.

  19. Nonlinear dynamics of Ytterbium-doped fiber laser Q-switched using acousto-optical modulator

    NASA Astrophysics Data System (ADS)

    Barmenkov, Y. O.; Kir'yanov, A. V.; Andres, M. V.

    2014-12-01

    A comprehensive experimental analysis of the dynamics of an ytterbium-doped fiber laser actively Q-switched (QS) using an intracavity acousto-optical modulator (AOM) is presented. It is shown that type of QS pulsing strongly depends on AOM repetition rate and pump power. In particular, at low repetition rates, including zero-rate, and at relatively high pump powers peculiar QS pulsing, switched by stimulated Brillouin scattering (SBS), is established in the laser. The cause of such kind of pulsing is the SBS-process boosted by spurious narrow-line CW lasing that arises in auxiliary low-Q cavity formed by an output coupler (in our experiments - fiber Bragg gratings) and weak reflections from blocked AOM. The parameters' area where this regime occurs is limited by certain values of pump power and AOM repetition rate. At increasing AOM repetition rate or decreasing pump power spurious CW lasing is not attained in the system; consequently, the SBS type of QS fades, while "conventional" QS (CQS) lasing is established in the system and remains. However CQS pulsing strongly suffers the nonlinear-dynamics effects: depending on AOM repetition rate and pump power the laser switches to common P1, P2, or P3 attractors, when QS pulses arise at sub-harmonics of AOM repetition rate, or to the specific transient regimes between them, or to chaotic operation. These and other sides (e.g. pulse jittering) of operation of the QS ytterbium-doped fiber laser with AOM are under scope of the present review as they have big interest for practical applications.

  20. Minocycline-induced hyperpigmentation: comparison of 3 Q-switched lasers to reverse its effects.

    PubMed

    Nisar, Mahrukh S; Iyer, Karthik; Brodell, Robert T; Lloyd, Jenifer R; Shin, Thuzar M; Ahmad, Asad

    2013-01-01

    Minocycline is a tetracycline derivative antibiotic commonly prescribed for acne, rosacea, and other inflammatory skin disorders. Minocycline turns black when oxidized, leading to discoloration of the skin, nails, bulbar conjunctiva, oral mucosa, teeth, bones, and thyroid gland. Hyperpigmentation has been reported after long-term minocycline therapy with at least 100 mg/day. Three types of minocycline-induced cutaneous hyperpigmentation can result. Type I is the most common, and is associated with blue-black discoloration in areas of previous inflammation and scarring. Type II most commonly affects the legs and is characterized by blue-gray pigmentation of previously normal skin. Type III is the least common and is characterized by diffuse muddy-brown discoloration predominantly on sun exposed skin. Minocycline-induced hyperpigmentation may be cosmetically disfiguring and prompt identification is essential. Without treatment, symptoms may take several months, to years to resolve, after discontinuation of the drug. However, the pigmentation may never completely disappear. In fact, there have been few reports of complete resolution associated with any therapeutic intervention. We report a case of a patient on long-term minocycline therapy utilized as an anti-inflammatory agent to control symptoms of rheumatoid arthritis, which led to minocycline-induced hyperpigmentation of the face. To remove the blue-gray cutaneous deposits, 3 Q-switched lasers (Neodymium: yttrium aluminum garnet (Nd:YAG) 1064 nm, Alexandrite 755 nm, and Ruby 694 nm) were used in test areas. The Alexandrite 755 nm laser proved to provide effective clearing of the minocycline hyperpigmentation requiring just 2 treatments, with minimal treatment discomfort and down time. PMID:23754872

  1. 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

  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. Tunable photonic microwave notch filter using SOA-based single-longitudinal mode, dual-wavelength laser.

    PubMed

    Lee, Kwanil; Lee, Ju Han; Lee, Sang Bae

    2009-07-20

    A novel photonic microwave notch filter with capability of frequency tuning is proposed and experimentally demonstrated. The scheme is based on a fiber Bragg grating (FBG)-based, single longitudinal mode, wavelength-spacing tunable dual-wavelength fiber laser and a dispersive fiber delay line. By using a symmetrical S-bending technique along the FBGs, the wavelength spacing of the laser can be tuned, which enables the microwave notch frequency tuning. Experimental results show that the notch rejection of more than 30 dB and the flexible tunability of notch frequency can be readily achieved in the range of 1.2 approximately 6.7 GHz. PMID:19654727

  4. The use of a dual-wavelength erbium-doped fiber laser for intra-cavity sensing

    NASA Astrophysics Data System (ADS)

    Wu, Baoqun; Lu, Ying; Jing, Lei; Huang, Xiaohui; Yao, Jianquan

    2013-11-01

    A novel intra-cavity sensor based on a dual-wavelength Er-doped fiber laser is proposed. The output power characteristics of the laser are investigated experimentally, and the sensitivity of power to relative cavity loss with different pump currents is studied by defining a sensitivity enhancement factor (SEF). A measurement of the relative sensitivity enhancement of 158.5 is obtained. Moreover, we used such a sensor to measure the absorption peak of NH3 with a 2 m long hollow core photonic crystal fiber as a gas cell.

  5. Numerical analysis of dual-wavelength nonreciprocal phase shifter for magneto-optical isolators on silicon-on-insulator system

    NASA Astrophysics Data System (ADS)

    Huang, Tianze; Sun, Yiling; Ouyang, Zhengbiao

    2014-11-01

    The wavelength dependence of the nonreciprocal phase shift (NPS) in a magneto-optical (MO) waveguide is investigated from the aspect of the geometrical structure. In an MO nonreciprocal waveguide, the effect of the waveguide dispersion on the NPS is being demonstrated to compensate the dispersion of the Faraday rotation coefficients. By accurately controlling the structure parameter of the MO waveguide, the wavelength-insensitive NPS can be obtained. According to this principle, we proposed the dual-wavelength nonreciprocal phase shifter at the wavelengths of 1.31 and 1.55 μm.

  6. Observation of spectral broadening in a commercial modelocked and Q-switched Nd:YLF oscillator - Wegner`s Demon

    SciTech Connect

    Wegner, P.; Feit, M.

    1994-09-14

    We have observed spectral broadening in the pulsed output of a Quantronix model 4217 modelocked and Q-switched Nd:YLF oscillator. When Q-switched, the 76-1MHz oscillator produces a nearly gaussian train of pulses with a total energy of 3 mJ and a duration of {approximately}300 ns. Between Q-switch cycles the CW-pumped oscillator lases at a low level to enable a circulating modelocked pulse to reach steady-state transform-limited conditions. With a 1-mm intracavity etalon the steady-state modelocked pulsewidth is 150 ps and the oscillating bandwidth is 3 GHz. Measurements show that at the peak of the Q-switched train the modelocked pulse bandwidth is broadened to 11 GHz, We attribute the altered spectrum to self-phase modulation (SPM) of the circulating pulse in the 3.8-cm long acousto-optic quartz modulators. SPM has been recognized as a potential problem in this type of oscillator however we did not expect to find it in a commercial product and its occurrence in the modulators rather than the rod was a surprise. Analysis of the cavity mode has determined that the spot size is small at the ends of the cavity where the modulators are located. A large mode volume in the rod coupled with a relatively small nonlinear coefficient makes intensity-dependent: phase shifts there negligible by comparison. Since the effects of SPM in this type of oscillator are not well-documented we developed a numerical model and used it to examine the spectral evolution of the circulating modelocked pulse after Q-switching. The model incorporates a rod with gain, two passive quartz blocks with nonlinear refractive index for simulating nonlinear propagation in the modulators, a time-dependent shutter to simulate the active modelocker, an etalon, and distributed Fresnel losses. The spectra that we calculate are in good agreement with that observed, confirming the source of the broadening. The oscillator has been redesigned to increase the mode size in the modulators and eliminate the SPM.

  7. 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.

  8. A wavelength-switchable single-longitudinal-mode dual-wavelength erbium-doped fiber laser for switchable microwave generation.

    PubMed

    Pan, Shilong; Yao, Jianping

    2009-03-30

    A novel wavelength-switchable single-longitudinal-mode (SLM) dual-wavelength erbium-doped fiber laser (EDFL) implemented based on a sigma architecture that is composed of a ring loop and a linear standing wave arm is experimentally demonstrated. Gain competition that prevents stable dual-wavelength oscillation is effectively suppressed by placing the gain medium in the standing-wave arm and by introducing polarization hole burning (PHB) via polarization multiplexing of the two lasing wavelengths in the ring loop. The SLM operation is guaranteed by an ultranarrow Fabry- Perot filter (FPF) introduced by absorption saturation in an unpumped erbium-doped fiber (EDF) and the gain saturation in the gain medium. In addition, the ring cavity forms a Lyot filter for each wavelength. Thus, wavelength switching is achieved by simply adjusting the polarization state of either wavelength. By beating the two SLM wavelengths at a photodetector (PD), a microwave signal with a frequency tunable from approximately 10 to approximately 50 GHz is experimentally generated. PMID:19333306

  9. [A Method for Determination of Migratable Fluorescent Whitening Agents in Paper Products by Dual-Wavelength UV Spectroscopy].

    PubMed

    Zhang, Shu-xin; Chai, Xin-sheng; Tian, Ying-xin; Chen, Run-quan

    2015-07-01

    The current national standard method GB/T 27741-2011, i.e., "quantitative determination of migratable fluorescent whitening agents-UV spectroscopy", overestimates the migratable fluorescent whitening agents (FWA) in the paper based products because of the spectral interference of the leached lignin from the cellulose fibers. To minimize such interference, a spectroscopic method based on dual-wavelength (305 and 348 nm) measurement was proposed. It was observed that the dual-wavelength spectroscopy can effectively subtract the spectral absorption contributed by the leached lignin in the extraction medium, thus more accurately determination of migratable FWA can be performed. The results showed that the present method has a relative standard deviation of 2.17%, the quantitative detection limit of 16.9 mg x kg(-1), and recovery of 98%-103%. Compared with the current alternative standard-HPLC method, the present method possesses advantages of low operation and maintenance costs, simple, and practical in application. Therefore, it is more suitable for the rapid determination of migratable FWA in the product quality control in the production process and sample examination in the commercial market. PMID:26717753

  10. 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.

  11. 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.

  12. Single- and dual-wavelength laser pulses induced modification in 10×(Al/Ti)/Si multilayer system

    NASA Astrophysics Data System (ADS)

    Salatić, B.; Petrović, S.; Peruško, D.; Čekada, M.; Panjan, P.; Pantelić, D.; Jelenković, B.

    2016-01-01

    The surface morphology of the ablation craters created in the multilayer 10×(Al/Ti)/Si system by nanosecond laser pulses at single- and dual wavelength has been studied experimentally and numerically. A complex multilayer thin film including ten (Al/Ti) bilayers deposited by ion sputtering on Si(1 0 0) substrate to a total thickness of 260 nm were illuminated at different laser irradiance in the range 0.25-3.5 × 109 W cm-2. Single pulse laser irradiation was done at normal incidence in air, with the single wavelength, either at 532 nm or 1064 nm or with both laser light simultaneously in the ratio of 1:10 for energy per pulse between second harmonic and 1064 nm. Most of the absorbed laser energy was rapidly transformed into heat, producing intensive modifications of composition and morphology on the sample surface. The results show an increase in surface roughness, formation of specific nanostructures, appearance of hydrodynamic features and ablation of surface material with crater formation. Applying a small fraction (10%) of the second harmonic in dual-wavelength pulses, a modification of the 10×(Al/Ti)/Si system by a single laser pulse was reflected in the formation of wider and/or deeper craters. Numerical calculations show that the main physical mechanism in ablation process is normal evaporation without phase explosion. The calculated and experimental results agree relatively well for the whole irradiance range, what makes the model applicable to complex Al/Ti multilayer systems.

  13. Cr4 + :Gd3Sc2Ga3O12 passive Q-switch for the Cr3 + :LiCaAlF6 laser

    NASA Astrophysics Data System (ADS)

    Kuo, Yen-Kuang; Yang, Yang; Birnbaum, Milton

    1994-05-01

    A Cr4+:Gd3Sc2Ga3O12 (Cr4+:GSGG) broad-band saturable absorber has been demonstrated to be an excellent passive Q-switch for the flashlamp-pumped tunable Cr3+:LiCaAlF6 (Cr:LiCAF) laser at room temperature. A single Q-switched laser output pulse of 11 mJ in energy and 37 ns in duration at 778 nm was obtained in a nonoptimized laser.

  14. 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. PMID:26861980

  15. 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.

  16. 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.

  17. 1.94 μm switchable dual-wavelength Tm3+ fiber laser employing high-birefringence fiber Bragg grating.

    PubMed

    Peng, W J; Yan, F P; Li, Q; Liu, S; Feng, T; Tan, S Y; Feng, S C

    2013-07-01

    A 1.94 μm switchable dual-wavelength Tm(3+) fiber laser employing two high-birefringence fiber Bragg gratings (HB-FBGs) is demonstrated. The polarization hole burning effect enhanced by the HB-FBG is first observed and adopted to guarantee stable dual-wavelength operation in the spectral region near 2 μm at room temperature. The wavelength spacing between the dual lasing wavelengths is 0.81 nm. The polarization states of the dual-output lasers are orthogonal. By adjusting a polarization controller, a single-wavelength mode operating at one of the dual wavelengths can be selected. The side-mode-suppression ratio of each laser can be greater than 60 dB. The power fluctuation measurement at both operating wavelengths shows that this Tm(3+) fiber laser has good stability. PMID:23842257

  18. 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. PMID:25927746

  19. 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.

  20. A semi-analytical approach for evaluating effects of amplified spontaneous emission on characteristics of Q-switched lasers

    SciTech Connect

    Razzaghi, D; Hajiesmaeilbaigi, F; Ruzbehani, M

    2012-08-31

    Possible effects of amplified spontaneous emission on output pulse characteristics of a Q-switched laser are discussed within the framework of a semi-analytical approach. It is shown that output energy decreases almost exponentially with average path length of the spontaneously emitted photons which in turn depends on geometrical specification and active medium properties as well as on optical finishing of the surfaces (for solid-state lasers). Optimal coupling dependence on the average path length is also investigated and shown to increase with average path length increment. (control of laser radiation parameters)

  1. Repetitive Q-switching of a CW Nd:YAG laser using Cr{sup 4+}:YAG saturable absorbers

    SciTech Connect

    Shimony, Y.; Burshtein, Z.; Ben-Amar Baranga, A.; Kalisky, Y.; Strauss, M.

    1996-02-01

    Repetitive Q-switching of a CW pumped Nd:YAG laser using a Cr{sup 4+}:YAG saturable absorber was achieved for the first time, providing pulses 80--300 ns wide (FWHM) with repetition rates ranging between 2 and 29 kHz. Different ranges of repetition rates and pulse widths are obtained by using absorbers of different optical densities. Satisfactory quantitative description of the experimental results is obtained by a full numerical solution of the system rate equations according to the theory of Powell and Wolga. These equations involve the dynamics of the laser population inversion, the absorber state population, and the photon density in the laser cavity.

  2. 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. PMID:27410624

  3. 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. PMID:26072779

  4. Continuous-wave and passively Q-switched 1.06 μm ceramic Nd:YAG laser

    NASA Astrophysics Data System (ADS)

    He, Ying; Ma, Yufei; Li, Jiang; Li, Xudong; Yan, Renpeng; Gao, Jing; Yu, Xin; Sun, Rui; Pan, Yubai

    2016-07-01

    In this paper, a diode-pumped continuous-wave and passively Q-switched 1.06 μm laser with gain medium of ceramic was demonstrated. Laser output characteristics using Nd:YAG ceramics with different doping concentrations of 1.0%, 2.0%, and 4.0% were studied. A maximum output power of 7.74 W with optical efficiency of 51.6% was obtained through the optimization of the coupler's transmission. By using Cr4+:YAG crystals with initial transmissions of 80% and 90% as saturable absorbers, the pulsed ceramic Nd:YAG laser performance was investigated.

  5. 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. PMID:23384078

  6. High-efficient diode-pumped actively Q-switched Nd:YAG/KTP Raman laser at 1096 nm wavelength

    NASA Astrophysics Data System (ADS)

    Su, Fufang; Zhang, Xingyu; Wang, Weitao; Cong, Zhenhua; Shi, Men; Yang, Xiuqin; Kong, Weijin; Ma, Lili; Wu, Wendi

    2013-09-01

    With Nd:YAG as the gain medium and KTP crystal as the Raman medium, the characteristics of an LD pumped intracavity actively Q-switched Nd:YAG/KTP Raman laser at 1096 nm wavelength were studied. The output characteristics of 1096 nm were investigated. At a pulse repetition rate of 30 kHz an average power up to 1.97 W was obtained with the incident pump power of 11.75 W, corresponding to a diode-to-Stokes conversion efficiency of 16.8%.

  7. Generation of 1.6 ns Q-switched pulses based on Yb:YAG/Cr:YAG microchip laser

    NASA Astrophysics Data System (ADS)

    Šulc, Jan; Jelínková, Helena; Nejezchleb, Karel; Škoda, Václav

    2015-05-01

    The highly-stable Q-switched longitudinally diode-pumped microchip laser, emitting radiation at wavelength 1031 nm, was designed and realized. This laser was based on monolith crystal which combines in one piece an active laser part (YAG crystal doped with Yb3+ ions, 10 at.% Yb/Y, 3mm long) and saturable absorber (YAG crystal doped with Cr3+ ions, 1.36mm long). The diameter of the diffusion bonded monolith was 3 mm. The initial transmission of the Cr:YAG part was 90% @ 1031 nm. The microchip resonator consisted of dielectric mirrors directly deposited on the monolith surfaces. The pump mirror (HT for pump radiation, HR for generated radiation) was placed on the Yb:YAG part. The output coupler with reflection 55% for the generated wavelength was placed on the Cr3+-doped part. Q-switched microchip laser was tested under CW diode pumping. For longitudinal pumping of Yb:YAG part, a fibre coupled (core diameter 100 μm, NA= 0.22) laser diode, operating at wavelength 968 nm, was used. The laser threshold was 3.3W. The laser slope efficiency calculated for output mean power in respect to incident CW pumping was 17%. The wavelength of linearly polarized laser emission was fixed to 1031 nm. The generated transversal intensity beam profile was close to the fundamental Gaussian mode. The generated pulse length was equal to 1.6 ns (FWHM). This value was mostly stable and independent on investigated pumping powers in the range from the threshold up to 9.3W. The single pulse energy was linearly increasing with the pumping power. Close to the laser threshold the generated pulse energy was 45 μJ. For maximum investigated CW pumping 9.3W the pulse energy was stabilized to 74 μJ which corresponds to the Q-switched pulse peak power 46 kW. The corresponding Q-switched pulses repetition rate was 13.6 kHz. The maximum Yb:YAG/Cr:YAG microchip laser mean output power of 1W was reached without observable thermal roll-over.

  8. 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

  9. 0.7 MW output power from a two-arm coherently combined Q-switched photonic crystal fiber laser.

    PubMed

    Rosenstein, Boris; Shirakov, Avry; Belker, Daniel; Ishaaya, Amiel A

    2014-03-24

    We demonstrate a high peak power, Q-switched pulsed, intracavity coherently combined fiber laser system. The system is based on two Yb-doped, rod-type, photonic crystal fibers which are passively phase-locked and combined into the single output beam in a power oscillator configuration. Experimental evidence indicate that this oscillator system provides record high peak power of ∼ 0.7 MW with pulse duration of ∼ 10 ns at 1 kHz repetition rate. The measured beam quality shows near-diffraction-limited operation of the coherently combined system. PMID:24663989

  10. Coaxial Dual-wavelength Interferometric Method for a Thermal Infrared Focal-plane-array with Integrated Gratings.

    PubMed

    Shang, Yuanfang; Ye, Xiongying; Cao, Liangcai; Song, Pengfei; Feng, Jinyang

    2016-01-01

    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. PMID:27193803

  11. 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.

  12. Experimental Determination of Dual-Wavelength Mie Lidar Geometric form Factor Combining Side-Scatter and Back-Scatter Signals

    NASA Astrophysics Data System (ADS)

    Wang, Zhenzhu; Tao, Zongming; Liu, Dong; Xie, Chenbo; Wang, Yingjian

    2016-06-01

    In theory, lidar overlap factor can be derived from the difference between the particle backscatter coefficient retrieved from lidar elastic signal without overlap correction and the actual particle backscatter coefficient, which can be obtained by other measured techniques. The side-scatter signal using a CCD camera is testified to be a powerful tool to detect the particle backscatter coefficient in near ground layer during night time. In experiment, by combining side-scatter and backscatter signals the geometric form factor for vertically-pointing Mie lidar in 532 nm channel is determined successfully, which is corrected by an iteration algorithm combining the retrieved particle backscatter coefficient using CCD sidescatter method and Fernald method. In this study, the method will be expanded to 1064 nm channel in dual-wavelength Mie lidar during routine campaigns. The experimental results in different atmosphere conditions demonstrated that the method present in this study is available in practice.

  13. 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.

  14. Coaxial Dual-wavelength Interferometric Method for a Thermal Infrared Focal-plane-array with Integrated Gratings

    PubMed Central

    Shang, Yuanfang; Ye, Xiongying; Cao, Liangcai; Song, Pengfei; Feng, Jinyang

    2016-01-01

    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. PMID:27193803

  15. 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.

  16. 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.

  17. Stabilized dual-wavelength erbium-doped fiber laser with a single-longitudinal mode by utilizing fiber Bragg grating and a compound-ring filter

    NASA Astrophysics Data System (ADS)

    Yeh, Chien-Hung; Chen, Hone-Zhang; Chen, Jhih-Yu; Chow, Chi-Wai

    2016-02-01

    In this investigation, a stable single-longitudinal-mode (SLM) dual-wavelength erbium-doped fiber (EDF) multiring laser by utilizing fiber Bragg grating is proposed and investigated. Here, to accomplish a SLM output, the multiring cavity of the proposed EDF laser is employed for suppressing the densely multilongitudinal mode. Hence, the output powers and wavelengths of the proposed dual-wavelength EDF laser are 7.0 and 6.7 dBm and 1531.72 and 1537.32 nm, respectively. In addition, the maximum output stabilities of the power and wavelength in the proposed laser are also executed and discussed.

  18. Development of an ultra-widely tunable DFG-THz source with switching between organic nonlinear crystals pumped with a dual-wavelength BBO optical parametric oscillator.

    PubMed

    Notake, Takashi; Nawata, Kouji; Kawamata, Hiroshi; Matsukawa, Takeshi; Qi, Feng; Minamide, Hiroaki

    2012-11-01

    We developed a difference frequency generation (DFG) source with an organic nonlinear optical crystal of DAST or BNA selectively excited by a dual-wavelength β-BaB(2)O(4) optical parametric oscillator (BBO-OPO). The dual-wavelength BBO-OPO can independently oscillate two lights with different wavelengths from 800 to 1800 nm in a cavity. THz-wave generation by using each organic crystal covers ultrawide range from 1 to 30 THz with inherent intensity dips by crystal absorption modes. The reduced outputs can be improved by switching over the crystals with adequately tuned pump wavelengths of the BBO-OPO. PMID:23187402

  19. A Stable Dual-wavelength Thulium-doped Fiber Laser at 1.9 μm Using Photonic Crystal Fiber

    NASA Astrophysics Data System (ADS)

    Soltanian, M. R. K.; Ahmad, H.; Khodaie, A.; Amiri, I. S.; Ismail, M. F.; Harun, S. W.

    2015-10-01

    A stable dual-wavelength thulium-doped fiber laser operating at 1.9 μm using a short length of photonic crystal fiber (PCF) has been proposed and demonstrated. The photonics crystal fiber was 10 cm in length and effectively acted as a Mach-Zehnder interferometry element with a free spectral range of 0.2 nm. This dual-wavelength thulium-doped fiber laser operated steadily at room temperature with a 45 dB optical signal-to-noise-ratio.

  20. A Stable Dual-wavelength Thulium-doped Fiber Laser at 1.9 μm Using Photonic Crystal Fiber.

    PubMed

    Soltanian, M R K; Ahmad, H; Khodaie, A; Amiri, I S; Ismail, M F; Harun, S W

    2015-01-01

    A stable dual-wavelength thulium-doped fiber laser operating at 1.9 μm using a short length of photonic crystal fiber (PCF) has been proposed and demonstrated. The photonics crystal fiber was 10 cm in length and effectively acted as a Mach-Zehnder interferometry element with a free spectral range of 0.2 nm. This dual-wavelength thulium-doped fiber laser operated steadily at room temperature with a 45 dB optical signal-to-noise-ratio. PMID:26455713

  1. A Stable Dual-wavelength Thulium-doped Fiber Laser at 1.9 μm Using Photonic Crystal Fiber

    PubMed Central

    Soltanian, M. R. K.; Ahmad, H.; Khodaie, A.; Amiri, I. S.; Ismail, M. F.; Harun, S. W.

    2015-01-01

    A stable dual-wavelength thulium-doped fiber laser operating at 1.9 μm using a short length of photonic crystal fiber (PCF) has been proposed and demonstrated. The photonics crystal fiber was 10 cm in length and effectively acted as a Mach-Zehnder interferometry element with a free spectral range of 0.2 nm. This dual-wavelength thulium-doped fiber laser operated steadily at room temperature with a 45 dB optical signal-to-noise-ratio. PMID:26455713

  2. A quasi-three-level dual-wavelength thin-disk laser at 1024 and 1030 nm based on a diode-pumped Yb:YAG crystal

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

    A diode-end-pumped Yb:YAG dual-wavelength continuous-wave (cw) laser that generates simultaneous laser action at wavelengths of 1024 and 1030 nm is demonstrated for the first time. A total output power of 897 mW for the dual-wavelength was achieved at an incident pump power of 17.8 W. Furthermore, intracavity sum-frequency mixing at 1024 and 1030 nm was then realized in an LBO crystal to reach the green range. We obtained a total cw output power of 85 mW at 513.5 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. Yb:YAG thin disk laser passively Q-switched by a hydro-thermal grown molybdenum disulfide saturable absorber

    NASA Astrophysics Data System (ADS)

    Zhan, Yi; Wang, Li; Wang, Jie Yu; Li, Hong Wei; Yu, Zhen Huang

    2015-02-01

    We demonstrate a passively Q-switched Yb:YAG thin disk solid-state laser based on nanoflake MoS2 as a saturable absorber. MoS2 is synthesized by a hydro-thermal process. The prepared MoS2 is transferred onto the BK7 glass for ease-of-use in the solid-state laser as a saturable absorber. The average output power could reach up to 250 mW, center wavelength 1030 nm corresponding to a pulse width, a pulse repetition rate, and a per pulse energy of 12 μs, 17 kHz, and 15 μJ, respectively. Our results show that nanoflake MoS2 could be a promising saturable absorber for Q-switching solid-state lasers. The over saturation of the MoS2 saturable absorber at a high pump strength limit in a solid-state laser could be also effective for high power operation.

  6. Repetitive Q-switched operation of x-axis Nd:La2Be2O5

    NASA Technical Reports Server (NTRS)

    Tucker, A. W.; Birnbaum, M.; Fincher, C. L.

    1981-01-01

    The repetitive Q-switched performances of an x-axis neodymium-doped lanthanum beryllate (Nd:BeL) laser and the current state-of-the-art Nd:YAG laser are compared. Output beam pulse energy, peak power, pulse width, beam divergence and mode pattern were measured for a gold-plated single elliptical cavity using a xenon flashlamp for excitation. The output of the Nd:BeL laser is found to exceed that of the Nd:YAG laser by a factor of two at Q-switched repetition rates on the order of 1 Hz, due to the smaller stimulated emission cross section of the x-axis Nd:BeL. When the repetition rate is increased to 10 Hz, the Nd:BeL output falls to a level three fifths lower than its low-rate value, while Nd:YAG output remained essentially constant. Analysis reveals that the decrease in output may be attributed to a depolarization loss due to thermally induced stress birefringence.

  7. Yb:YAG enhanced Cr,Yb:YAG self-Q-switched microchip laser under QCW laser-diode pumping

    NASA Astrophysics Data System (ADS)

    Wang, Guangyu; Chen, Dimeng; Cheng, Ying; Dong, Jun

    2015-05-01

    Enhanced Cr,Yb:YAG self-Q-switched microchip lasers by bonding Yb:YAG crystal have been studied under quasi-continuous-wave (QCW) laser-diode pumping for the first time to our best knowledge. The effects of the pump pulse duration and pump power of the QCW laser-diode on the performance of Yb:YAG/Cr,Yb:YAG microchip lasers have been investigated. The optical efficiency, pulse energy and peak power of the Yb:YAG/Cr,Yb:YAG self-Q-switched laser increase with the pump pulse duration and pump power, and tend to be constant when the pump pulse duration is longer than 1 ms, which is comparable to the fluorescence lifetime of Yb:YAG crystal. Output energy of over 11.7 mJ was obtained at input pump energy of 48.2 mJ; corresponding optical-to-optical efficiency of 24.3% was obtained. Laser pulses with pulse energy of 31 μJ and peak power of 13.3 kW were obtained. The multi-longitudinal modes oscillation around 1030 nm was dominant within the available input pump energy.

  8. 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

    2015-05-01

    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. PMID:25969240

  9. Third-order nonlinearity and passive Q-switching of Cr⁴⁺:YGG garnet crystal.

    PubMed

    Wang, Shuxian; Zhang, Yuxia; Wu, Kui; Zhang, Rui; Yu, Haohai; Zhang, Huaijin; Zhang, Guanghui; Xiong, Qihua

    2015-05-15

    We demonstrate the third-order nonlinear optical properties of Cr(4+):Y(3)Ga(5)O(12) (Cr(4+):YGG) and Q-switched lasers with Cr(4+):YGG as the saturable absorber for the first time to our knowledge. The third-order nonlinear properties, including the optical Kerr nonlinearity and saturable absorption, were systematically measured and analyzed in detail by using a Z-scan technique. The measured data show that Cr(4+):YGG has a large nonlinear refractive index, ground-state absorption cross section, and excited-state absorption cross section in contrast to Cr(4+):Y(3)Al(5)O(12) (Cr(4+):YAG). With a Nd:YGG crystal as the gain medium and a Cr(4+):YGG crystal as the saturable absorber, the passively Q-switched laser was performed. The shortest pulse width and largest pulse energy were achieved at the absorbed pump power of 8 W with the values of 9.1 ns and 26.1 μJ, respectively, corresponding to the average output power of 0.87 W and peak power of 2.9 kW. The results indicate that Cr(4+):YGG is an available and promising optical switcher for pulsed lasers. PMID:26393755

  10. A high-energy cladding-pumped 80 nanosecond Q-switched fiber laser using a tapered fiber saturable absorber

    NASA Astrophysics Data System (ADS)

    Moore, Sean W.; Soh, Daniel B. S.; Bisson, Scott E.; Patterson, Brian D.; Hsu, Wen L.

    2013-02-01

    We report a passively Q-switched all-fiber laser using a large mode area (LMA) Yb3+-doped fiber cladding-pumped at 915 nm and an unpumped single-mode Yb3+-doped fiber as the saturable absorber (SA). The saturable absorber and gain fibers were first coupled with a free-space telescope to better study the composite system, and then fusion spliced with fiber tapers to match the mode field diameters. ASE generated in the LMA gain fiber preferentially bleaches the SA fiber before depleting the gain, thereby causing the SA fiber to act as a passive saturable absorber. Using this scheme we first demonstrate a Q-switched oscillator with 40 μJ 79 ns pulses at 1026 nm using a free-space taper, and show that pulses can be generated from 1020 nm to 1040 nm. We scale the pulse energy to 0.40 mJ using an Yb3+-doped cladding pumped fiber amplifier. Experimental studies in which the saturable absorber length, pump times, and wavelengths are independently varied reveal the impact of these parameters on laser performance. Finally, we demonstrate 60 μJ 81 ns pulses at 1030 nm in an all fiber architecture using tapered mode field adaptors to match the mode filed diameters of the gain and SA fibers.

  11. A Q-switched multi-wavelength Brillouin erbium fiber laser with a single-walled carbon nanotube saturable absorber

    NASA Astrophysics Data System (ADS)

    Tan, S. J.; Harun, S. W.; Ahmad, F.; Nor, R. M.; Zulkepely, N. R.; Ahmad, H.

    2013-05-01

    A Q-switched multi-wavelength Brillouin erbium fiber laser (MWBEFL) is demonstrated using a single-walled carbon nanotube-polyethylene oxide (SWCNT-PEO) saturable absorber (SA). The SA is fabricated by cutting off a small part of the developed SWCNT-PEO film and sandwiching it in between two FC/PC (fiber connector/physical contact) fiber connectors. Multi-wavelength combs with ten lasing lines and spacing of 0.158 nm are obtained by the use of 2 km long dispersion compensating fiber as the Brillouin gain medium and a four-port circulator to isolate and circulate the odd-order Stokes signals. Q-switched pulse trains with a repetition rate of 105.2 kHz and a pulse width of 0.996 μs are obtained in the proposed MWBEFL at a 1480 nm pump power of 120 mW and a Brillouin pump power of 5.4 dBm.

  12. 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.

  13. Theory and Engineering Design Aspects of a Mini Diode-Pumped Q-Switch Er: Glass Laser for Space Applications

    NASA Astrophysics Data System (ADS)

    Sankar, N. Siva; Ramalingam, A.; Raja, V. L. N. Sridhar; Laxmiprasad, A. S.

    2011-10-01

    The invention of the laser, with its precise wavelength and beam divergence characteristics, coupled with the techniques like q-switching, mode locking to produce ultra-short pulses has been influencing the era of space technology. Space agencies worldwide are equipping satellites with laser transmitters in the hope of achieving crucial and vital tasks. Though, both laser technology and space operations have matured substantially in the recent decades, offering synergistic possibilities of using lasers from space-based platforms, development of a reliable laser sources meeting the space mission types and constraints is still the current quest. This paper especially focuses on the conceptualization and engineering design aspects of developing a miniaturized diode pumped, passive q-switch Er: Glass laser capable of delivering pulses of energy 3 mJ, pulse width of 7 ns at a repetition rate of 1 Hz and operating wavelength of 1535 nm. This paper sheds the light also on the selected resonator configurations, pump geometries and theoretical estimations that were performed in selection of the resonator elements keeping the miniaturization as the prime concern. Simulations of the non-linear effects like pump energy distribution, thermal lensing of the configured laser resonator design are done by employing various laser cavity and design analysis software.

  14. LD-end-pumped passively Q-switched Nd:YAG ceramic laser with single wall carbon nanotube saturable absorber

    NASA Astrophysics Data System (ADS)

    Li, C. Y.; Bo, Y.; Zong, N.; Wang, Y. G.; Jiang, B. X.; Pan, Y. B.; Niu, G.; Fan, Z. W.; Peng, Q. J.; Cui, D. F.; Xu, Z. Y.

    2012-10-01

    We report on a LD-end-pumped passively Q-switched Nd:YAG ceramic laser by using a novel single wall carbon nanotube saturable absorber (SWCNT-SA). The SWCNT wafer was fabricated by electric Arc discharge method on quartz substrate with absorption wavelength of 1064 nm. We firstly investigated the continuous wave (CW) laser performance and scattering properties of Nd:YAG ceramic sample. For the case of passively Q-switched operation, a maximum output power of 376 mW was obtained at an incident pump power of 8.68 W at 808 nm, corresponding to an optical-optical conversion efficiency of 4.3%. The repetition rate as the increase of pump power varied from 14 to 95 kHz. The minimum pulse duration of 1.2 μs and maximum pulse energy of 4.5 μJ was generated at a repetition rate of 31.8 kHz.

  15. 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.

  16. 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. PMID:26368084

  17. Tunable and switchable dual-wavelength mode-locked Tm3+-doped fiber laser based on a fiber taper.

    PubMed

    Wang, Yazhou; Li, Jianfeng; Zhai, Bo; Hu, Yunxiao; Mo, Kundong; Lu, Rongguo; Liu, Yong

    2016-07-11

    We demonstrate a self-starting dual-wavelength mode-locked fiber laser at a 2 μm spectral region by using a fiber taper in a Tm3+-doped ring fiber cavity. The fiber taper fabricated with a flame brushing technique was used as a periodic filter with a modulation depth of ~3.61 dB and a modulation period of ~7.3 nm, respectively. Diverse dual-wavelength regimes including continuous wave (CW)/multi-soliton, soliton/multi-soliton, and soliton/soliton regimes were obtained by adjusting pump power. Wavelength tuning for the dual-wavelength was also precisely controllable through stretching the fiber taper carefully. The tuning range was ~7 nm which was limited by the modulation period of the taper. By inserting a 10.0 m dispersion compensation fiber (DCF) into the fiber cavity, a stable dual-wavelength dissipative-soliton operation was obtained at 2 μm spectral region for the first time. PMID:27410806

  18. 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. PMID:24977828

  19. Nanosecond pulse generation in a passively Q-switched Nd:GGG laser at 1331 nm by CVD graphene saturable absorber

    NASA Astrophysics Data System (ADS)

    Xu, Bin; Wang, Yi; Cheng, Yongjie; Yang, Han; Xu, Huiying; Cai, Zhiping

    2015-10-01

    We report on a nanosecond pulse generation in a diode end-pumped passively Q-switched Nd:GGG laser at the low-gain transition line of 1331 nm. A three-layer CVD graphene thin film was transferred from Cu foil to a BK7 glass substrate for the use of saturable absorber. A stable Q-switching laser operation was obtained with maximum average output power of 0.69 W and slope efficiency of about 11.0% with respect to the absorbed pump power. The shortest pulse duration and the maximum repetition rate of the pulse trains were registered to be 556 ns and 166.7 kHz with corresponding maximum pulse energy 4.14 μJ and pulse peak power 7.45 W. This is the first demonstration of CVD-graphene-based Q-switched laser operation at 1.3 μm, to the best of our knowledge.

  20. Broadband tuning in a passively Q-switched erbium doped fiber laser (EDFL) via multiwall carbon nanotubes/polyvinyl alcohol (MWCNT/PVA) saturable absorber

    NASA Astrophysics Data System (ADS)

    Ahmad, H.; Hassan, S. N. M.; Ahmad, F.; Zulkifli, M. Z.; Harun, S. W.

    2016-04-01

    An MWCNT/PVA-based Q-switched erbium-doped fiber laser (EDFL) that uses a tunable bandpass filter (TBPF) as the wavelength tuning and filtering mechanism to achieve a broadband tuning range is proposed and demonstrated. The tuning range of the generated Q-switched pulses covered a wide wavelength range of 50 nm, which spanned from 1519 nm to 1569 nm and corresponded to the S- and C-band regions. In addition, the lasing and Q-switching operations had low thresholds of 8.9 mW and 22.4 mW respectively. The highest pulse energy of 52.13 nJ was obtained at an output wavelength of 1569 nm, with a corresponding repetition rate of 26.53 kHz and pulse width of 6.10 μs, at the maximum power of 114.8 mW.

  1. Diverse output states from an all-normal dispersion ytterbium-doped fiber laser: Q-switch, dissipative soliton resonance, and noise-like pulse

    NASA Astrophysics Data System (ADS)

    Xu, Z. W.; Zhang, Z. X.

    2013-06-01

    An all-normal-dispersion ytterbium-doped fiber ring laser has been demonstrated, with different operation regimes: Q-switch, CW mode-locking and noise-like pulses, depending on the pump power and suitable orientation of the polarization controllers. As a transition between Q-switch and CW mode-locking, Q-switched mode-locking has also been observed. Moreover, our experiment shows that the CW mode-locking operation is the result of dissipative soliton resonance in the all-normal-dispersion fiber laser without external filter, which is a new way to generate high-energy pulses. This fiber laser with diverse outputs has many potential applications, and is helpful to investigate laser dynamics.

  2. High-pulse-energy passively Q-switched quasi-monolithic microchip lasers operating in the sub-100-ps pulse regime.

    PubMed

    Nodop, D; Limpert, J; Hohmuth, R; Richter, W; Guina, M; Tünnermann, A

    2007-08-01

    We present passively Q-switched microchip lasers with items bonded by spin-on-glass glue. Passive Q-switching is obtained by a semiconductor saturable absorber mirror. The laser medium is a Nd:YVO(4) crystal. These lasers generate pulse peak powers up to 20 kW at a pulse duration as short as 50 ps and pulse repetition rates of 166 kHz. At 1064 nm, a linear polarized transversal and longitudinal single-mode beam is emitted. To the best of our knowledge, these are the shortest pulses in the 1 microJ energy range ever obtained with passively Q-switched microchip lasers. The quasi-monolithic setup ensures stable and reliable performance. PMID:17671554

  3. Acousto-optic Q-switching laser performance of Yb:GdCa(4)O(BO(3))(3)crystal.

    PubMed

    Chen, Xiaowen; Xu, Honghao; Guo, Yunfeng; Han, Wenjuan; Yu, Haohai; Zhang, Huaijin; Liu, Junhai

    2015-08-20

    We report on the active Q-switching laser performance of Yb:GdCa4O(BO3)3 crystal, demonstrated by employing an acousto-optic Q-switch in a compact plano-concave resonator. Stable repetitively Q-switched operation is achieved with pulse repetition rates varying from 30 to 0.2 kHz, producing an average output power of 10.2 W at 1027.5 nm at 30 kHz of repetition rate, with an optical-to-optical efficiency of 30%. The maximum pulse energy generated at the lowest repetition rate of 0.2 kHz is 4.75 mJ, with a pulse width being 11 ns, gives rise to a peak power that amounts to 432 kW. PMID:26368745

  4. 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.

  5. 2.79 μm high peak power LGS electro-optically Q-switched Cr,Er:YSGG laser.

    PubMed

    Wang, Li; Wang, Jintao; Yang, Jingwei; Wu, Xianyou; Sun, Dunlu; Yin, Shaotang; Jiang, Haihe; Wang, Jiyang; Xu, Changqing

    2013-06-15

    A flash lamp pumped Cr,Er:YSGG laser utilizing a langasite (LGS) crystal as an electro-optic Q-switch is proposed and demonstrated. It is proved that a LGS crystal with relatively high damage threshold can be used as the electro-optic Q-switch at 2.79 μm, and 216 mJ pulse energy with 14.36 ns pulse width is achieved. Its corresponding peak power of pulse can reach 15 MW, to our knowledge the best result at a 2.79 μm wavelength. PMID:23939006

  6. Passive q-switching of CO/sub 2/ TEA laser using sulfur hexafluoride (SF/sub 6/). Report for April-August 1986

    SciTech Connect

    Pastel, R.

    1986-10-01

    Passive Q-switching of a CO/sub 2/ TEA laser using sulfur hexafluoride (SF/sub 6/) was demonstrated at 10.2 micron. There is minimum loss of peak power, narrowing of the pulse, and elimination of the tail. Q-switching at 9.6 micron was not observed. Also discussed is the use of SF/sub 6/ to frequency the laser to the strong gain lines of the 10.2-m and 9.6-m branch of the CO/sub 2/ emission. Both theory and experimental results are given.

  7. Tunable Q-switched fiber laser based on saturable edge-state absorption in few-layer molybdenum disulfide (MoS₂).

    PubMed

    Woodward, R I; Kelleher, E J R; Howe, R C T; Hu, G; Torrisi, F; Hasan, T; Popov, S V; Taylor, J R

    2014-12-15

    We fabricate a few-layer molybdenum disulfide (MoS₂) polymer composite saturable absorber by liquid-phase exfoliation, and use this to passively Q-switch an ytterbium-doped fiber laser, tunable from 1030 to 1070 nm. Self-starting Q-switching generates 2.88 μs pulses at 74 kHz repetition rate, with over 100 nJ pulse energy. We propose a mechanism, based on edge states within the bandgap, responsible for the wideband nonlinear optical absorption exhibited by our few-layer MoS₂ sample, despite operating at photon energies lower than the material bandgap. PMID:25607060

  8. Diode-pumped CW and passively Q-switched lasers of Nd:GdLuAG mixed garnet at 1123 nm

    NASA Astrophysics Data System (ADS)

    Liu, Yang; Liu, Zhaojun; Zhang, Sasa; Xia, Jinbao; Zhang, Yanmin; Guan, Chen

    2016-03-01

    Diode-pumped CW and passively Q-switched lasers of Nd:GdLuAG mixed garnet at 1123 nm were demonstrated. The maximum average output power of CW operation was 4.13 W. For Q-switched operation, the average output power was 800 mW, the corresponding single pulse energy was 133.8 μJ. The Nd:GdLuAG laser emitting at 1123 nm was obtained for the first time to the best of our knowledge, which proves that the Nd:GdLuAG mixed garnet has a better ability of energy storage than Nd:YAG in 1123 nm oscillation.

  9. Gold nanobipyramids as saturable absorbers for passively Q-switched laser generation in the 1.1  μm region.

    PubMed

    Zhang, Huanian; Liu, Jie

    2016-03-15

    We demonstrated that gold nanobipyramids (Au-NBPs) can be used as saturable absorbers for ultrafast pulsed-laser application, for the first time. Au-NBPs are prepared through a seed-mediated growth method, and performance is investigated in a passively Q-switched Nd:YVO4 laser. In the Q-switched operation the maximum average output power that can be achieved is 151 mW. The minimum pulse width is 396 ns at a pulse repetition rate of 90.6 kHz. PMID:26977656

  10. MoS2 nanoflowers as high performance saturable absorbers for an all-fiber passively Q-switched erbium-doped fiber laser

    NASA Astrophysics Data System (ADS)

    Wei, Rongfei; Zhang, Hang; Tian, Xiangling; Qiao, Tian; Hu, Zhongliang; Chen, Zhi; He, Xin; Yu, Yongze; Qiu, Jianrong

    2016-03-01

    Strong saturable absorption was observed in MoS2 nanoflowers, which were synthesized by a facile solvothermal method. A MoS2 nanoflower-based saturable absorber with a high modulation depth of 51.8% and a large saturable intensity of 275.5 GW cm-2 was introduced to the application of passively Q-switched fiber laser generation. Stable passively Q-switched fiber laser pulses at 1.56 μm with a low threshold power of 16.10 mW, high signal-to-noise ratio of 52.5 dB and short pulse duration of 1.9 μs were obtained. More importantly, a high output power of 3.10 mW related to a large pulse energy of about 51.84 nJ can be attained at a very low pump power. The efficiency of the laser reaches 4.71%, which is larger than that of the prepared layered MoS2 and recently reported MoS2-based passively Q-switching operations. Such results imply that the MoS2 nanoflowers are an excellent candidate for a saturable absorber in passively Q-switched fiber lasers at a low pump intensity.Strong saturable absorption was observed in MoS2 nanoflowers, which were synthesized by a facile solvothermal method. A MoS2 nanoflower-based saturable absorber with a high modulation depth of 51.8% and a large saturable intensity of 275.5 GW cm-2 was introduced to the application of passively Q-switched fiber laser generation. Stable passively Q-switched fiber laser pulses at 1.56 μm with a low threshold power of 16.10 mW, high signal-to-noise ratio of 52.5 dB and short pulse duration of 1.9 μs were obtained. More importantly, a high output power of 3.10 mW related to a large pulse energy of about 51.84 nJ can be attained at a very low pump power. The efficiency of the laser reaches 4.71%, which is larger than that of the prepared layered MoS2 and recently reported MoS2-based passively Q-switching operations. Such results imply that the MoS2 nanoflowers are an excellent candidate for a saturable absorber in passively Q-switched fiber lasers at a low pump intensity. Electronic supplementary

  11. 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.

  12. Passively Q-switched 2 μm Tm:YAP laser based on graphene saturable absorber mirror.

    PubMed

    Hou, Jia; Zhang, Baitao; He, Jingliang; Wang, Zhaowei; Lou, Fei; Ning, Jian; Zhao, Ruwei; Su, Xiancui

    2014-08-01

    Using high-quality single-layer graphene as a saturable absorber, Tm:YAlO₃ (Tm:YAP) crystal as the gain medium, we demonstrated a laser-diode-pumped, compact, passively Q-switched (PQS) solid-state laser in the 2 μm region. The maximum average output power was 362 mW, with the corresponding largest pulse repetition rate and pulse energy of 42.4 kHz and 8.5 μJ, respectively. Under the same pump power, the pulse width of 735 ns was obtained, which is, to our best knowledge, the shortest pulse width among Tm-doped solid-state PQS lasers using graphene saturable absorber mirrors. PMID:25090328

  13. Experimental investigation on laser milling of aluminium oxide using a 30 W Q-switched Yb:YAG fiber laser

    NASA Astrophysics Data System (ADS)

    Leone, C.; Genna, S.; Tagliaferri, F.; Palumbo, B.; Dix, M.

    2016-01-01

    In the present study, laser milling tests were carried out on aluminium oxide (Al2O3) plate, 3 mm in thickness, using a Q-Switched 30 W Yb:YAG fiber laser. A systematic approach based on Design of Experiment (DoE) has been successfully adopted with the aim to detect which and how the process parameters affect the laser beam-material interaction, and to explain the effect of the process parameters on the material removal rate and surface quality. The examined process parameters were the laser beam scan speed, the pulse frequency, the total energy released for surface unit, the distance between two consecutive scan lines and the scanning strategy. A full factorial design and ANalysis Of VAriance (ANOVA) were applied for the results analysis. Finally, the various effects of the process parameters on the material removal rate and surface roughness have been analysed and discussed.

  14. Passively Q-switched 1617-nm polycrystalline ceramic Er:YAG laser using a Cr:ZnSe saturable absorber

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaoqi; Shen, Deyuan; Huang, Haitao; Liu, Jun; Zhang, Jian; Tang, Dingyuan; Fan, Dianyuan

    2015-08-01

    We report on a passively Q-switched polycrystalline ceramic Er:YAG laser by using a Cr:ZnSe crystal as a saturable absorber. When pumped by a 1532-nm Er-, Yb-doped fiber laser with the maximum power of 12.4 W, the laser yielded pulses of 28.8 ns duration at 1617 nm by using a saturable absorber with an initial transmission of 80 %. The corresponding peak power was up to 11.3 kW at a repetition rate of 2.17 kHz. The dependence of the pulse duration and repetition rate on the pump power was experimentally studied. The numerical and experimental results both show that the pulse duration was mainly determined by the initial transmission of the saturable absorber and slightly affected by the transmission of the output coupler. At last, we give some prospects for further narrowing down the pulse duration.

  15. Analytical solution of the transient temperature profile in gain medium of passively Q-switched microchip laser.

    PubMed

    Han, Xiahui; Li, Jianlang

    2014-11-01

    The transient temperature evolution in the gain medium of a continuous wave (CW) end-pumped passively Q-switched microchip (PQSM) laser is analyzed. By approximating the time-dependent population inversion density as a sawtooth function of time and treating the time-dependent pump absorption of a CW end-pumped PQSM laser as the superposition of an infinite series of short pumping pulses, the analytical expressions of transient temperature evolution and distribution in the gain medium for four- and three-level laser systems, respectively, are given. These analytical solutions are applied to evaluate the transient temperature evolution and distribution in the gain medium of CW end-pumped PQSM Nd:YAG and Yb:YAG lasers. PMID:25402922

  16. 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}.

  17. Application systems for the intracorporal laser-induced shockwave lithotripsy using the Nd:YAG Q-switched laser

    NASA Astrophysics Data System (ADS)

    Frank, Klaus H.; Eichenlaub, M.; Hessel, Stefan F. F.; Wondrazek, Fritz

    1990-06-01

    For the laser-induced shockwave lithotripsy the electromagnetic energy of a laser light pulse is converted intracorporally into the acoustic energy of a shock wave. The lithotriptor is based on a specially developed, Q-switched Nd:YAG laser whose high power light pulses (70 mJ, 25 ns) are coupled into a flexible quartz fiber of 600 pim core diameter. Using focussing elements energy densities higher than 6 1O J m2 can be achieved resulting in an optical breakdown in water followed by a shock wave. As a result of different absorption mechanisms the breakdown threshold can be decreased by placing a metallic target into the laser beam. The different shockwave formations of such optomechanical transducers have been measured. First clinical applications have been performed.

  18. The formation of iron aluminides on aluminum surface by using a Q-switched Nd:YAG laser

    NASA Astrophysics Data System (ADS)

    Bidin, Noriah; Al-Wafi, Yusef A.

    2014-03-01

    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-2.

  19. 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

  20. Narrow-band 1 W source at 257 nm using frequency quadrupled passively Q-switched Yb:YAG laser.

    PubMed

    Goldberg, Lew; Cole, Brian; McIntosh, Chris; King, Vernon; Hays, A D; Chinn, Stephen R

    2016-07-25

    We describe generation of 1.1 W of 257 nm emission by frequency quadrupling the 1030 nm emission from a compact passively Q-switched Yb:YAG laser. The laser utilized a volume Bragg grating to achieve a 0.1 nm linewidth required for UV-Raman spectroscopic applications, generated 100 kW peak power, 250 μJ pulses and 3.6 W of average power at 1030 nm. Fourth harmonic generation (FHG) was carried out using a 10 mm lithium triborate (LBO) crystal to generate 515 nm second harmonic with 70% conversion efficiency, followed by a 7 mm beta-barium borate (BBO) crystal to generate 257 nm fourth harmonic with 45% efficiency, resulting in an overall nonlinear conversion efficiency of 31%. Far-field and near-field of the FHG emission were characterized. PMID:27464186

  1. 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.

  2. 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.

  3. 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. PMID:25143716

  4. Q-switched waveguide laser based on two-dimensional semiconducting materials: tungsten disulfide and black phosphorous.

    PubMed

    Tan, Yang; Guo, Zhinan; Ma, Linan; Zhang, Han; Akhmadaliev, Shavkat; Zhou, Shengqiang; Chen, Feng

    2016-02-01

    Owing to their unique properties, graphene-like two dimensional semiconducting materials, including Tungsten Disulfide (WS2) and Black Phosphorous (BP), have attracted increasing interest from basic research to practical applications. Herein, we demonstrated the ultrafast nonlinear saturable absorption response of WS2 and BP films in the waveguide structure. Through fabricating WS2 and BP films by evaporating the solutions on glass wafers. Saturable absorber films were attached onto the end-facet of the waveguide, which therefore constitutes a resonant cavity for the waveguide laser. Under a pump laser at 810 nm, we could obtain a stable Q-switched operation in the waveguide structure. This work indicated the significant potential of WS2 and BP for the ultrafast waveguide laser. PMID:26906854

  5. WS2 as a saturable absorber for Q-switched 2  micron lasers.

    PubMed

    Luan, Chao; Yang, Kejian; Zhao, Jia; Zhao, Shengzhi; Song, Lei; Li, Tao; Chu, Hongwei; Qiao, Junpeng; Wang, Chao; Li, Zhen; Jiang, Shouzhen; Man, Baoyuan; Zheng, Lihe

    2016-08-15

    We prepared WS2 nanosheets by using the thermal decomposition method and demonstrated for the first time its nonlinear saturable absorption property at around 2 μm. With the as-prepared WS2 nanosheets as saturable absorber (SA), a passively Q-switched Tm:LuAG laser was realized successfully, and 660 ns laser pulses with an average output power of 1.08 W and pulse peak power of 26 W at a repetition rate of 63 kHz were obtained for an incident pump power of 7 W. Our experimental results definitely demonstrate that WS2 could be a kind of promising SA for solid-state 2 μm lasers. PMID:27519088

  6. Phase retrieval based on temporal and spatial hybrid matching in simultaneous phase-shifting dual-wavelength interferometry.

    PubMed

    Qiu, Xiang; Zhong, Liyun; Xiong, Jiaxiang; Zhou, Yunfei; Tian, Jindong; Li, Dong; Lu, Xiaoxu

    2016-06-13

    In simultaneous phase-shifting dual-wavelength interferometry, by matching both the phase-shifting period number and the fringe number in interferogram of two wavelengths to the integers, the phase with high accuracy can be retrieved through combining the principle component analysis (PCA) and least-squares iterative algorithm (LSIA). First, by using the approximate ratio of two wavelengths, we can match both the temporal phase-shifting period number and the spatial fringe number in interferogram of two wavelengths to the integers. Second, using above temporal and spatial hybrid matching condition, we can achieve accurate phase shifts of single-wavelength of phase-shifting interferograms through using PCA algorithm. Third, using above phase shifts to perform the iterative calculation with the LSIA method, the wrapped phases of single-wavelength can be determined. Both simulation calculation and experimental research demonstrate that by using the temporal and spatial hybrid matching condition, the PCA + LSIA based phase retrieval method possesses significant advantages in accuracy, stability and processing time. PMID:27410297

  7. Photoacoustic imaging of a near-infrared fluorescent marker based on dual wavelength pump-probe excitation

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

    Photoacoustic imaging has been used to determine the spatial distribution of fluorophores, such as exogenous dyes and genetically expressed proteins, from images acquired in phantoms and in vivo. Most methods involve the acquisition of multiwavelength images and rely on differences in the absorption spectra of the tissue chromophores to estimate the spatial distribution and abundance of the latter using spectral decomposition techniques, such as model based inversion schemes. However, the inversion of 3-D images can be computationally expensive. Experimental approaches to localising contrast agents may therefore be useful, especially if quantification is not essential. This work aims to develop a method for determining the spatial distribution of a near-infrared fluorescent cell marker from images acquired using dual wavelength excitation. The excitation wavelengths coincided with the absorption and emission spectrum of the fluorophore. The contrast mechanism relies on reducing the excited state lifetime of the fluorophore by inducing stimulated emission. This changes the amount of energy thermalized by the fluorophore, and hence the photoacoustic signal amplitude. Since this is not observed in endogenous chromophores, the background may be removed by subtracting two images acquired with and without pulse delay between the pump and probe pulses. To characterise the fluorophore, the signal amplitude is measured in a cuvette as a function of pulse delay, concentration, and fluence. The spatial distribution of the fluorophore is determined from images acquired in realistic tissue phantoms. This method may be suitable for in vivo applications, such as imaging of exogenous or genetically expressed fluorescent cell markers.

  8. 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.

  9. Dual-wavelength vertical external-cavity surface-emitting laser: strict growth control and scalable design

    NASA Astrophysics Data System (ADS)

    Jasik, Agata; Sokół, Adam Kamil; Broda, Artur; Sankowska, Iwona; Wójcik-Jedlińska, Anna; Wasiak, Michał; Kubacka-Traczyk, Justyna; Muszalski, Jan

    2016-02-01

    This paper reports on the design and fabrication of a dual-wavelength vertical external-cavity surface-emitting laser. Grown by molecular beam epitaxy, the laser structures have a relatively simple active region divided into two sections, between which there is no optical filter. Comparable threshold power was achieved for both wavelengths. The growth rate was controlled precisely by growing AlAs/GaAs superlattices with different period thicknesses and testing them with high-resolution X-ray diffractometry. The simultaneous emission of two wavelengths was detected in setup without a heat spreader, one of 991 nm and the other of 1038 nm. After diamond heat spreader was bonded, both wavelengths lased in continuous-wave mode with the combined output power of 1.79 W. The design scalability allowed us to obtain two further structures with layers thinned by about 3 % in the first and by about 6 % in the second, operating at 958/1011 and 928/977 nm, respectively.

  10. Compact Handheld Probe for Shifted Excitation Raman Difference Spectroscopy with Implemented Dual-Wavelength Diode Laser at 785 Nanometers.

    PubMed

    Maiwald, Martin; Eppich, Bernd; Ginolas, Arnim; Sumpf, Bernd; Erbert, Götz; Tränkle, Günther

    2015-10-01

    A compact handheld probe for shifted-excitation Raman difference spectroscopy (SERDS) with an implemented dual-wavelength diode laser with an emission at 785 nm is presented. The probe is milled from aluminum and has dimensions 100 × 28 × 12 mm. The diode laser provides two excitation lines with a spectral distance of 10 cm(-1) (0.62 nm), has a spectral width smaller than 11 pm, and reaches an optical power of 120 mW ex probe. Raman experiments were carried out using polystyrene (PS) as the test sample. During a measurement time of over 1 h, a stable spectral center position of the Raman line at 999 cm(-1) of PS was achieved within a spectral window of 0.1 cm(-1). Here, the Raman intensity of this line was observed with a peak-to-peak variation smaller than ±2%, dominated by shot noise interference. A deviation of the center position of a Raman line with <±1 cm(-1) was observed over the whole excitation power range. Raman investigations of the quartz glass window of the SERDS probe showed minor interference. The results demonstrate the suitability of the developed handheld probe for Raman investigations and the application of in situ SERDS experiments to fields such as food safety control, medical diagnostics, and process control. PMID:26449807

  11. 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.

  12. 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

  13. 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.

  14. Dual Wavelength RP-HPLC Method for Simultaneous Determination of Two Antispasmodic Drugs: An Application in Pharmaceutical and Human Serum.

    PubMed

    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 μ Bondapak 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. 785-nm dual wavelength DBR diode lasers and MOPA systems with output powers up to 750 mW

    NASA Astrophysics Data System (ADS)

    Sumpf, Bernd; Maiwald, Martin; Klehr, Andreas; Müller, André; Bugge, Frank; Fricke, Jörg; Ressel, Peter; Erbert, Götz; Tränkle, Günther

    2015-03-01

    Raman lines are often superimposed by daylight, artificial light sources or fluorescence signals from the samples under study. Shifted excitation Raman difference spectroscopy (SERDS), i.e. exciting the sample alternatingly with two slightly shifted wavelengths, allows to distinguish between the Raman lines and sources of interference. In this work, monolithic dual wavelength Y-branch DBR ridge waveguide diode lasers and their application in master oscillator power amplifier (MOPA) systems at 785 nm suitable for Raman spectroscopy and SERDS will be presented. The definition of the wavelengths is made by implementing deeply-etched 10th order 500 μm long surface gratings with different periods using i-line wafer stepper lithography. Y-branch DBR lasers with a total length of 3 mm and a stripe width of 2.2 μm were manufactured and characterized. The monolithic devices reach output powers up to 215 mW with emission widths of about 20 pm. At 200 mW the conversion efficiency is 20%, i.e. the electrical power consumption is only 1 W. The spectral distance between the two laser cavities is about 0.6 nm, i.e. 10 cm-1 as targeted. The side mode suppression ratio is better than 50 dB. Amplifying these devices using a ridge waveguide amplifier an output power of about 750 mW could be achieved maintaining the spectral properties of the master oscillator.

  16. 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.

  17. Efficient passive Q-switching operation of a diode-pumped Nd:GdVO4 laser with a Cr4+:YAG saturable absorber

    NASA Astrophysics Data System (ADS)

    Liu, Junhai; Ozygus, Bernd; Yang, Suhui; Erhard, Jürgen; Seelig, Ute; Ding, Adalbert; Weber, Horst; Meng, Xianlin; Zhu, Li; Qin, Lianjie; Du, Chenlin; Xu, Xinguang; Shao, Zongshu

    2003-04-01

    A diode-pumped highly efficient Cr4+:YAG passively Q-switched Nd:GdVO4 laser formed by a plano-concave resonator has been demonstrated. At the highest attainable absorbed pump power of 11.4 W, 4.05 W of average output power, which was two thirds of the maximum corresponding cw output, was achieved with an optical conversion efficiency of 35.5%, and the slope efficiency was determined to be 46.8%, reaching 85% of the magnitude of its cw counterpart. The resulting shortest pulse duration, single-pulse energy, and peak power were found to be 13 ns, 90 μJ, and 7 kW, respectively, with a pulse repetition frequency (PRF) of 45 kHz. Two particularly modified resonator configurations were employed; the largest pulse energy and the highest peak power reached were, respectively, 154 μJ and 11.2 kW at 8.5 W of absorbed pump power. An analytical relation between the PRF and the absorbed pump power is given for a passively Q-switched laser, showing good consistency with experiment with a Nd:GdVO4 laser. The dependence of the operational parameters on the pump power and on the output coupling was also investigated experimentally. Issues involving the criterion for passive Q switching are discussed in some detail for Cr4+:YAG passively Q-switched neodymium-doped vanadate lasers.

  18. 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. PMID:27176977

  19. MoS2 nanoflowers as high performance saturable absorbers for an all-fiber passively Q-switched erbium-doped fiber laser.

    PubMed

    Wei, Rongfei; Zhang, Hang; Tian, Xiangling; Qiao, Tian; Hu, Zhongliang; Chen, Zhi; He, Xin; Yu, Yongze; Qiu, Jianrong

    2016-04-14

    Strong saturable absorption was observed in MoS2 nanoflowers, which were synthesized by a facile solvothermal method. A MoS2 nanoflower-based saturable absorber with a high modulation depth of 51.8% and a large saturable intensity of 275.5 GW cm(-2) was introduced to the application of passively Q-switched fiber laser generation. Stable passively Q-switched fiber laser pulses at 1.56 μm with a low threshold power of 16.10 mW, high signal-to-noise ratio of 52.5 dB and short pulse duration of 1.9 μs were obtained. More importantly, a high output power of 3.10 mW related to a large pulse energy of about 51.84 nJ can be attained at a very low pump power. The efficiency of the laser reaches 4.71%, which is larger than that of the prepared layered MoS2 and recently reported MoS2-based passively Q-switching operations. Such results imply that the MoS2 nanoflowers are an excellent candidate for a saturable absorber in passively Q-switched fiber lasers at a low pump intensity. PMID:26997036

  20. 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.