共查询到20条相似文献,搜索用时 156 毫秒
1.
M. Stanislawki J. Meister T. Mitra M.M. Ivanenko K. Zanger P. Hering 《Applied physics. B, Lasers and optics》2001,72(1):115-120
The Er:YAG and the CO2 laser are competitors in the field of hard tissue ablation. The use of Er:YAG lasers (2.94 μm, pulse length
L of 100 to 200 μs) show smaller areas of thermal defects then ‘‘superpulsed’’ CO2 lasers with pulse lengths of approximately 100 μs. Only the development of a Q-switched CO2 laser (9.6 μm, τL=250 ns) allowed for similar results. In this paper new results for the Er:YAG and the Q-switched CO2 laser under the influence of water spray will be presented. Several parameters are of special interest for these investigations:
the specific ablation energy, which shows a minimum for the CO2 laser at an energy density of 9 J/cm 2 and a broad shallow minimum in the range of 10 to 70 J/cm2 for the Er:YAG laser, and comparison of the cut-shape and depth. Surface effects and cutting velocity are discussed based
on SEM pictures.
Received: 19 July 2000 / Revised version: 1 November 2000 / Published online: 30 November 2000 相似文献
2.
Junhai Liu Valentin Petrov Huaijin Zhang Jiyang Wang 《Applied physics. B, Lasers and optics》2007,88(4):527-530
The power scaling capacity of a diode end-pumped Yb:KLu(WO4)2 laser, operating in the continuous-wave (cw) and passively Q-switched regimes, has been investigated. A cw output power of
11.5 W was achieved with an optical-to-optical efficiency of 41% with respect to the incident pump power, while the slope
efficiency amounts to 60%. The passively Q-switchedoperation yielded an average output power of 4.3 W at the fundamental wavelength
of 1031.7 nm, and 1.15 W of Raman radiation at 1139.3 nm. The total slope efficiency for Q-switched operation was 40%. The
highest pulse energy, duration, and peak power were 170 μJ, 2.2 ns, and 77.3 kW for the fundamental radiation, and 51 μJ,
2.3 ns, and 22.2 kW for the Raman radiation.
PACS 42.55.Rz; 42.55.Xi; 42.55.Ye 相似文献
3.
High-power picosecond LiB3O5 optical parametric oscillators tunable in the blue spectral range 总被引:2,自引:0,他引:2
The paper reports on an experimental investigation and numerical analysis of noncritically and critically phasematched LiB3O5 (LBO) optical parametric oscillators (OPOs) synchronously pumped by the third harmonic of a cw diode-pumped mode-locked Nd:YVO4 oscillator–amplifier system. The laser system generates 9.0 W of 355-nm mode-locked radiation with a pulse duration of 7.5 ps
and a repetition rate of 84 MHz. The LBO OPO, synchronously pumped by the 355-nm pulses, generates a signal wave tunable in
the blue spectral range 457–479 nm. With a power of up to 5.0 W at 462 nm and 1.7 W at 1535 nm the conversion efficiency is
74%. The OPO is characterized experimentally by measuring the output power (and its dependence on the pump power, the transmission
of the output coupler and the resonator length) and the pulse properties (such as pulse duration and spectral width). Also
the beam quality of the resonant and nonresonant waves is investigated. The measured results are compared with the predictions
of a numerical analysis for Gaussian laser and OPO beams. In addition to the blue-signal output visible-red 629-nm radiation
is generated by sum-frequency mixing of the 1.535-μm infrared idler wave with the residual 1.064-μm laser radiation. A power
of 1.25 W of 1.535-μm idler radiation and 5.7 W of 1.064-μm laser light generated a red 629-nm output power of 2.25 W.
Received: 2 February 2000 / Revised version: 28 July 2000 / Published online: 22 November 2000 相似文献
4.
S.I. Dolgaev S.V. Lavrishev A.A. Lyalin A.V. Simakin V.V. Voronov G.A. Shafeev 《Applied Physics A: Materials Science & Processing》2001,73(2):177-181
The formation and development of the large-scale periodic structures on a single crystal Si surface are studied upon its evaporation
by pulsed radiation of a copper vapor laser (wavelength of 510.6 nm, pulse duration of 20 ns). The development of structures
occurs at a high number of laser shots (∼104) at laser fluence of 1–2 J/cm2 below optical breakdown in a wide pressure range of surrounding atmosphere from 1 to 105 Pa. The structures are cones with angles of 25, which grow towards the laser beam and protrude above the initial surface
for 20–30 μm. It is suggested that the spatial period of the structures (10–20 μm) is determined by the capillary waves period
on the molten surface. The X-ray diffractometry reveals that the modified area of the Si substrate has a polycrystalline structure
and consists of Si nanoparticles with a size of 40–70 nm, depending on the pressure of surrounding gas. Similar structures
are also observed on Ge and Ti.
Received: 12 February 2000 / Accepted: 28 March 2000 / Published online: 20 June 2001 相似文献
5.
Single axial mode operation (<200 MHz optical bandwidth) of a high repetition rate periodically poled lithium niobate optical
parametric oscillator (OPO) has been obtained at signal wavelengths between 1.46 μm and 1.64 μm. OPO signal slope efficiencies
of 35% have been measured for repetition rates of 5–20 kHz. Single mode operation required spectral narrowing of both the
pump laser and the OPO. A simple technique of prelase Q-switching was implemented to reduce the optical bandwidth of the cw diode-pumped Nd:YAG pump laser to <1 GHz. A single intracavity
étalon was then sufficient to ensure single frequency oscillation of the OPO signal. The OPO output was stable with a smooth
spatial profile and an M
2 value of 1.3.
Received: 29 September 1999 / Published online: 27 January 2000 相似文献
6.
D. Mazzotti P. De Natale G. Giusfredi C. Fort J.A. Mitchell L.W. Hollberg 《Applied physics. B, Lasers and optics》2000,70(6):747-750
We report difference-frequency generation (DFG) in periodically poled lithium niobate (PPLN) around 4.25 μm using a cw Nd:YAG
and an injection-locked diode laser. This system provides a narrow linewidth source at 4.25 μm with near-shot-noise-limited
operation. A conversion efficiency close to the theoretical limit is obtained. Detection of CO2 absorption spectra is demonstrated and further improvements and applications to high sensitivity spectroscopy are discussed.
Received: 12 August 1999 / Revised version: 21 January 2000 / Published online: 24 March 2000 相似文献
7.
An efficient continuous wave (CW) and Q-switched c-cut Tm:YAP laser is reported in this letter. With the dual-end-pumped convex-concave resonator, CW output power up to 13.6
W at 1.99 μm was obtained under a total incident pump power of 50 W. The corresponding slope efficiency was 34.3% and conversion
efficiency was 27.2%. The active Q-switched operation of the laser had an average output power of 12.5 W at 10 kHz pulse repetition
frequency, with a minimum pulse width of 126 ns. With 6 kHz pulse repetition frequency, the maximum pulse energy of 1.6 mJ
was obtained. In addition, using the Tm:YAP laser as a pumping source for gain-switched Cr:ZnSe laser, as much as 4 W output
power in the wavelength range of 2.5–2.6 μm was obtained. 相似文献
8.
The free running and Q-switched operation of 2 μm Tm:YAG lasers side-pumped by pulse laser diodes were reported. In the free
running mode the maximum output energies were 102.5 mJ at 1 Hz and 94.6 mJ at 10 Hz, respectively. With an acousto-optic modulator
in the laser resonator, 21 mJ 2 μm Q-switched pulse was obtained, with a pulse width of about 330 ns. The dependences of the
output energy and the efficiency on the laser resonator parameters were investigated. 相似文献
9.
Mid-infrared trace gas detection using continuous-wave difference frequency generation in periodically poled RbTiOAsO4 总被引:1,自引:0,他引:1
A tunable mid-infrared continuous-wave (cw) spectroscopic source in the 3.4–4.5 μm region is reported, based on difference
frequency generation (DFG) in a quasi-phase-matched periodically poled RbTiOAsO4 (PPRTA) crystal, DFG power levels of 10 μW were generated at approximately 4 μm in a 20-mm long PPRTA crystal by mixing two
cw single-frequency Ti:Al2O3 lasers operating near 713 nm and 871 nm, respectively, using a laser pump power of 300 mW. A quasi-phase-matched infrared
wavelength-tuning bandwidth (FWHM) of ∼12 cm-1 and a temperature tuning rate of 1.02 cm-1/°C were achieved. Experimental details regarding the feasibility of trace gas detection based on absorption spectroscopy
of CO2 in ambient air using this DFG radiation source are also described.
Received: 23 October 2000 / Revised version: 22 January 2001 / Published online: 27 April 2001 相似文献
10.
The efficient cw mode locking (cw-ML) regime was demonstrated in Nd:YVO4 laser by means of saturable absorber mirror (SAM). The 0.3-at.% Nd3+ doped 10-mm-long YVO4 crystal end pumped by 20-W diode module with a beam shaper was applied as a gain medium located in the close vicinity to
the rear flat mirror of the first arm of Z-type resonator of 316 cm total length with two curved mirrors of 100-cm curvature
radii. The SAM of 2%-saturable absorptance and saturation fluence of 50 μJ/cm2 was mounted at the opposite end of a resonator. The developed “dynamically stable” cavity design mitigates detrimental role
of thermal aberration in gain medium, enforcing clean perfect mode locking even for the highest pump densities. The cw-ML
pulses with 47.5 MHz repetition rate and pulse durations in the range of 15–20 ps were observed for a wide range of pump powers
and output coupler losses. In the best case, for 32% of output coupler transmission, up to 6.2 W of average power with near
35% slope efficiency was achieved. The thresholds for Q-switched ML, cw-ML regimes were 2.67 W and 6.13 W of pump power, respectively.
For the maximum pump power of 20 W we obtained 133 nJ of pulse energy with 16-ps pulse duration, resulting in a peak power
higher than 8 kW. The threshold energy density at SAM giving the QML regime was estimated to be about 30 μJ/cm2, threshold of cw-ML regime was 220 μJ/cm2. 相似文献
11.
S. Chénais F. Druon F. Balembois G. Lucas-Leclin P. Georges A. Brun M. Zavelani-Rossi F. Augé J.P. Chambaret G. Aka D. Vivien 《Applied physics. B, Lasers and optics》2001,72(4):389-393
We demonstrate that Yb-doped Ca4GdO(BO3)3 (GdCOB) crystals are suitable for the development of high-power diode-pumped lasers emitting at around 1.04 μm. A 15%-doped
Yb:GdCOB crystal was longitudinally pumped with a cw fiber-coupled diode emitting 10 W at 976 nm. While 5.2 W of diode power
was absorbed, we obtained 3.2 W of 1043-μm laser light, with a beam quality factor M2 equal to 3, and 2.5 W in a diffraction-limited beam. Furthermore, the laser is continuously tunable between 1018 and 1086 nm.
Thermal effects have been investigated with a Shack–Hartmann wavefront analyser: although thermal lensing is not negligible,
it does not affect the performance of the laser with the resonator design we used.
Received: 1 August 2000 / Revised version: 18 September 2000 / Published online: 21 February 2001 相似文献
12.
Diode end-pumped Q-switched high-power intracavity frequency-doubled Nd:GdVO4/KTP green laser 总被引:2,自引:0,他引:2
J. Liu C. Wang C.Q. Wang X. Meng H. Zhang L. Zhu J. Wang Z. Shao M. Jiang 《Applied physics. B, Lasers and optics》2001,72(2):171-174
A diode-laser-array end-pumped acousto-optically Q-switched intracavity frequency-doubled Nd:GdVO4/KTP green laser, formed with a three-mirror folded resonator, has been demonstrated. With 15 W of pump power incident upon
the Nd:GdVO4 crystal, a maximum average green output power of 3.75 W was obtained at 50 kHz of pulse repetition frequency, giving an optical
conversion efficiency of 25%, whereas the effective intracavity frequency-doubling efficiency was determined to be 72%. At
the incident pump power of 12.8 W, the shortest laser pulse was achieved at a pulse repetition rate of 10 kHz, the resulting
pulse width, single pulse energy, and peak power were measured to be 35 ns, 108 μJ, and 3.1 kW, respectively.
Received: 18 May 2000 / Published online: 20 September 2000 相似文献
13.
R. Peeters G. Berden A. Apituley G. Meijer 《Applied physics. B, Lasers and optics》2000,71(2):231-236
A compact open-path optical ammonia detector is developed. A tunable external-cavity diode laser operating at 1.5 μm is used
to probe absorptions of ammonia via the cavity-enhanced absorption (CEA) technique. The detector is tested in a climate chamber.
The sensitivity and linearity of this system are studied for ammonia and water at atmospheric pressure. A cluster of closely
spaced rovibrational overtone and combination band transitions, observed as one broad absorption feature, is used for the
detection of ammonia. On these molecular transitions a detection limit of 100 ppb (1 s) is determined. The ammonia measurements
are calibrated independently with a chemiluminescence monitor. Compared to other optical open-path detection methods in the
1–2 μm region, the present result shows an improved sensitivity for contactless ammonia detection by over one order of magnitude.
Using the same set-up, a detection limit of 100 ppm (1 s) is determined for the detection of water at atmospheric pressure.
Received: 19 January 2000 / Revised version: 6 March 2000 / Published online: 7 June 2000 相似文献
14.
Laser-diode-pumped Cr4+, Nd3+:YAG self-Q-switched laser with high repetition rate and high stability 总被引:4,自引:0,他引:4
A diode end-pumped self Q-switched Cr4+, Nd3+: YAG laser was established with 30-ns pulse width (FWHM) and 0.5-μJ pulse energy output. In normal pulse pumping operation,
the lasing threshold changed greatly from 122 mJ to 2.4 mJ as the pump pulse frequency varied from 1 Hz to 500 Hz due to pumping-induced
thermal effect. A pre-pumping method was proposed and the change of the lasing threshold was reduced; programmable Q-pulse
output with maximum frequency of 16 kHz and high stability was achieved.
Received: 16 January 2001 / Revised version: 21 May 2001 / Published online: 19 September 2001 相似文献
15.
A.V. Podlipensky K.V. Yumashev N.V. Kuleshov H.M. Kretschmann G. Huber 《Applied physics. B, Lasers and optics》2003,76(3):245-247
Spectroscopic data of a V3+:YAG passive Q-switch crystal were measured. The absorption recovery time was determined to be of 37±7 ns and the ground state
absorption cross section was estimated to be 0.7×10-18 cm2 at 1.44 μm and 3.5×10-18 cm2 at 1.34 μm. Passively Q-switched operation of diode pumped 1.44 μm and 1.3 μm Nd:YAG lasers was demonstrated using this crystal
as saturable absorber. Average output powers of 1.42 W (1.44 μm) and 1.56 W (1.34 μm) and pulse energies of 24 μJ (1.44 μm)
and 25 μJ (1.34 μm) were observed, respectively.
Received: 19 August 2002 / Published online: 12 February 2003
RID="*"
ID="*"Corresponding author. Fax: +49-40/42838-6281, E-mail: kretschmann@physnet.uni-hamburg.de 相似文献
16.
J.C. Diettrich I.T. McKinnie D.M. Warrington 《Applied physics. B, Lasers and optics》1999,69(3):203-206
We have developed a gain-switched room-temperature Cr:forsterite laser operating at repetition rates of between 1 and 34 kHz,
and pumped by a continuous wave, Q-switched Nd:YAG laser. With optimised output coupling, an output pulse energy of 52 μJ
was measured at 1.5 kHz repetition rate, corresponding to 11% efficiency and 13% slope efficiency. Threshold pulse energy
was 53 μJ. Output power of 370 mW was obtained at 10 kHz repetition rate and 4.4 W pump power. Water cooling was not required
for repetition rates up to 10 kHz. In a tunable, folded resonator, the Cr:forsterite wavelength tuned between 1173 and 1338 nm.
This laser operated with maximum pulse energy of 34 μJ, efficiency of 13%, and power of 307 mW. The laser output was close
to diffraction-limited with M2 of 1.2.
Received: 6 January 1999 / Published online: 29 July 1999 相似文献
17.
M.W. Todd R.A. Provencal T.G. Owano B.A. Paldus A. Kachanov K.L. Vodopyanov M. Hunter S.L. Coy J.I. Steinfeld J.T. Arnold 《Applied physics. B, Lasers and optics》2002,75(2-3):367-376
A novel instrument, based on cavity-ringdown spectroscopy (CRDS), has been developed for trace gas detection. The new instrument
utilizes a widely tunable optical parametric oscillator (OPO), which incorporates a zinc–germanium–phosphide (ZGP) crystal
that is pumped at 2.8 μm by a 25-Hz Er,Cr:YSGG laser. The resultant mid-IR beam profile is nearly Gaussian, with energies
exceeding 200 μJ/pulse between 6 and 8 μm, corresponding to a quantum conversion efficiency of approximately 35%. Vapor-phase
mid-infrared spectra of common explosives (TNT, TATP, RDX, PETN and Tetryl) were acquired using the CRDS technique. Parts-per-billion
concentration levels were readily detected with no sample preconcentration. A collection/flash-heating sequence was implemented
in order to enhance detection limits for ambient air sampling. Detection limits as low as 75 ppt for TNT are expected, with
similar concentration levels for the other explosives.
Received: 1 April 2002 / Revised version: 13 June 2002 / Published online: 12 September 2002
RID="*"
ID="*"Corresponding author. Fax: +1-408/524-0551, E-mail: mtodd@picarro.com 相似文献
18.
4 (KTA) optical parametric oscillator (OPO) synchronously pumped by a cw diode-pumped mode-locked Nd:YVO4 oscillator–amplifier system. The laser system (pumped by 84 W of cw 808-nm diode radiation) generates 7-ps-long pulses at
1.064 μm with a repetition rate of 83.4 MHz and an average power of 29 W. The OPO, synchronously pumped by the 1.064-μm laser
pulses, consists of a 15-mm-long KTA crystal (cut for type II noncritical phase-matching) in a folded signal resonant linear
resonator. The average powers of the 1.54-μm signal radiation and the 3.47-μm idler radiation are 14.6 W and 6.4 W, respectively.
The total OPO output of 21 W corresponds to an internal efficiency of 75%. The experimental investigations include measurements
of the OPO output power (and its dependence on the pump power, the transmission of the output coupler, and the resonator length)
and of the pulse properties (such as pulse duration and spectral width). The measured results are in good agreement with the
predictions of a numerical analysis based on a split-step Fourier method.
Received: 4 May 1998 相似文献
19.
C. Theobald M. Weitz R. Knappe R. Wallenstein J.A. L’huillier 《Applied physics. B, Lasers and optics》2008,92(1):1-3
This paper reports on a passively mode-locked and Q-switched Nd:YVO4 laser generating picosecond pulses with an average output power exceeding 7 W. In a first step Q-switch mode-locking was
obtained by self Q-switching of a mode-locked oscillator with appropriate cavity design, pump power and output coupling. In
a second system the Q-switching was actively controlled and stabilized by modulating the resonator internal losses with an
acousto-optic modulator. In the Q-switch mode-locking operation the laser provided 12.8 ps long mode-locked pulses with a
repetition rate of 80 MHz. The repetition rate of the Q-switch envelope was 185 kHz. The maximum pulse energy of a single
ps pulse was 0.55 μJ which is 5.5 times the pulse energy measured for cw mode locking. The total energy of the pulses within
the Q-switch envelope was 42 μJ.
PACS 42.55.Xi; 42.60.Fc; 42.60.Gd 相似文献
20.
Frequency doubling of a passively Q-switched microchip laser using BiBO crystals is reported. Generation of green second harmonic
at 532 nm with pulse energies of 2.4–3.4 μJ and conversion efficiency of 25–35% is demonstrated. 相似文献