共查询到20条相似文献,搜索用时 15 毫秒
1.
B. van Der Sijde S. Adema J. De Haas C. J. M. Denissen M. J. F. van De Sande 《等离子体物理论文集》1982,22(4):357-368
Thomson scattering with a 1.5 ms long pulse mode 20 J ruby laser has been applied to a radiative argon plasma with electron densities ne from 2.5 1019 m?3 to 1.5 1020 m?3 and an electron temperature Te of about 3 eV. Photon counting techniques have been used. The accuracy of ne and Te to be reached is about 5% after 10 shots. The signal to noise ratio S/N has been optimized by the use of optical filters and a special purpose grating. The effects of these elements on S/N have been calculated. The entrance angle, transmission and quantum efficiency have also been optimized. A comparison between 5 possible laser systems, including a normal mode and a Q-switched mode ruby laser, has been carried out. 相似文献
2.
A. V. Golenishchev-Kutuzov V. A. Golenishchev-Kutuzov R. I. Kalimullin A. A. Potapov 《Physics of the Solid State》2011,53(3):518-521
Variations in local polarization switching fields E
C
in lithium niobate crystals have been investigated under laser irradiation of the z surface. It has been established that the simultaneous application of an electric field in the direction opposite to the
spontaneous polarization field and laser beam leads to a decrease in the field E
C
. 相似文献
3.
The oscillation frequency shift ratio (OFSR) of a three-cavity coupled laser diode, which is caused by refractive index changes due to current modulation and temperature variation, has been investigated. It is found that the OFSR is significantly reduced by using a laser with an AR coated facet and a high external-mirror reflectivity, in addition to large external cavity lengths. Also, compared with an external cavity laser, the three-cavity laser has a smaller OFSR provided that the external cavities' reflectivities r0 and r3, are not identical (that is, r3 > r0). The analysis indicates that the structural parameters affect the OFSR of the three-cavity laser, which was shown to have a high longitudinal mode discrimination1. 相似文献
4.
The combined effect of relativistic and ponderomotive nonlinearities on the self‐focusing of an intense cosh‐Gaussian laser beam (CGLB) in magnetized plasma have been investigated. Higher‐order paraxial‐ray approximation has been used to set up the self‐focusing equations, where higher‐order terms in the expansion of the dielectric function and the eikonal are taken into account. The effects of various lasers and plasma parameters viz. laser intensity (a0), decentred parameter (b), and magnetic field (ωc) on the self‐focusing of CGLB have been explored. The results are compared with the Gaussian profile of laser beams and relativistic nonlinearity. Self‐focusing can be enhanced by optimizing and selecting the appropriate laser‐plasma parameters. It is observed that the focusing of CGLB is fast in a nonparaxial region in comparison with that of a Gaussian laser beam and in a paraxial region in magnetized plasma. In addition, strong self‐focusing of CGLB is observed at higher values of a0, b, and ωc. Numerical results show that CGLB can produce ultrahigh laser irradiance over distances much greater than the Rayleigh length, which can be used for various applications. 相似文献
5.
M. Jackson L.R. Zink J. Flores-Mijangos A. Robinson J.M. Brown 《Applied physics. B, Lasers and optics》2007,86(2):303-307
A laser magnetic resonance spectrometer has been used to discover and subsequently measure a far-infrared laser emission:
the 166.6-micron line of CH2F2, optically pumped by the 9P24 CO2 laser. By recording spectra for the NH radical, the frequency of this laser emission has been determined to be 1799950±13 MHz.
Spectra for the NH radical were also recorded with two other far-infrared laser emissions: the 160.4-micron line of N2H4 (9P46 CO2 pump) and the 328.6-micron line of 13CH3OH (9P12 CO2 pump). From the NH spectra, a discrepancy of 2.1 GHz with the previously measured laser frequency was identified for the
160.4-micron line. A three-laser heterodyne system was then used to remeasure the frequency to be 1868475.5±0.5 MHz. The NH
spectra were also used to determine the frequency for the 328.6-micron line to be 912366±7 MHz, in agreement with the value
previously calculated from the Rydberg–Ritz combination principle.
PACS 07.57.Hm; 32.60.+i; 42.62.Eh 相似文献
6.
The changes in emission characteristics of a neon hollow cathode discharge by resonant laser excitation of 1s
5→2p
2 and 1s
5→2p
4 transition have been studied by simultaneously monitoring the optogalvanic effect and the laser induced fluorescence. It
has been observed that resonant excitation causes substantial variation in the relative intensities of lines in the emission
spectrum of neon discharge. 相似文献
7.
A.?V.?Akimov E.?O.?Tereshchenko S.?A.?Snigirev A.?Yu.?Samokotin A.?V.?Sokolov N.?N.?Kolachevski? V.?N.?Sorokin 《Journal of Experimental and Theoretical Physics》2009,109(3):359-369
The resonant interaction of 87Rb atoms in a magneto-optical trap with femtosecond laser radiation in the spectral range 760–820 nm has been investigated
experimentally. It has been demonstrated that femtosecond laser radiation with a spectral width of 10 nm interacts with an
atomic ensemble as a set of spectrally narrow modes and as an ionizing laser field simultaneously. The dynamics of trap loading
in the presence of ionization by femtosecond radiation has been studied, and the 5D
5/2 level population produced by an additional weak laser field has been measured. 相似文献
8.
An analytical model of K
α radiation of thin laser targets has been developed. It has been shown that, for such targets, the motion of fast electrons
is significant not only in the target itself but also in vacuum. The considered dependences for the free path length of a
fast electron and for the absorption coefficient of laser radiation on the laser intensity with allowance for the electron
motion in vacuum make it possible to match the results of the proposed model with the experimental data on generation of K
α radiation in wide ranges of laser intensities (1018–1021 W/cm2) and thicknesses (1–100 μm) of targets. 相似文献
9.
Gopal C Bhar Pathik Kumbhakar D V Satyanarayana N S N Banerjee U Nundy C G Chao 《Pramana》2000,55(3):405-412
Generation of third harmonic of CO2 laser radiation has been obtained in a type-II, ϑ=57° cut 9 mm thick AgGaSe2 crystal for the first time by sum-frequency-mixing of the fundamental with its second harmonic, the latter being obtained
using another type-I, ϑ=55° cut 11 mm thick AgGaSe2 crystal. The energy conversion efficiencies obtained for second harmonic and third harmonic generations are 6.3% and 2.4%
respectively with the input fundamental pump power density of 5.9 MW/cm2 only. The wavelength of the fundamental CO2 laser radiation used for the generation of harmonics is 10.6 μm, P(20) line. A compact TEA CO2 laser source has been built in the laboratory. 相似文献
10.
M. Temporal B. Canaud 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2011,65(3):447-451
Illumination uniformity of a spherical capsule directly driven by laser beams has been
assessed numerically. Laser facilities characterized by
N
D
= 12, 20, 24, 32, 48 and 60 directions
of irradiation with associated a single laser beam or a bundle of
N
B
laser beams have been considered. The
laser beam intensity profile is assumed super-Gaussian and the calculations take into
account beam imperfections as power imbalance and pointing errors. The optimum laser
intensity profile, which minimizes the root-mean-square deviation of the capsule
illumination, depends on the values of the beam imperfections. Assuming that the
N
B
beams are statistically independents is
found that they provide a stochastic homogenization of the laser intensity associated to
the whole bundle, reducing the errors associated to the whole bundle by the
factor
\hbox{1/NB1/21/N_{B}^{1{/}2}}
1
/
N
B
1
/
2
,
which in turn improves the illumination uniformity of the capsule. Moreover, it is found
that the uniformity of the irradiation is almost the same for all facilities and only
depends on the total number of laser beams N
tot
= N
D
× N
B
. 相似文献
11.
G. Tomassetti A. Ritucci A. Reale L. Palladino L. Reale S. V. Kukhlevsky F. Flora L. Mezi J. Kaiser A. Faenov T. Pikuz 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,19(1):73-77
A capillary discharge soft X-ray laser operating at 46.9 nm on the transition 3p-3s (J = 0-1) of the Ne-like Ar has been realized by exciting the active medium with a long half-cycle duration current pulse of
140 ns. The current is produced by discharging a 10 nF water dielectric capacitor, initially charged to voltages lower than
200 kV by a six stage Marx generator, through a 15-cm long capillary channels. The laser amplification has been obtained by
properly adjusting all the other experimental parameters. Utilizing a 3-mm in diameter Al2O3 capillary channel initially filled with 0.3 torr of Ar pressure, a laser beam, which has a 4-mrad divergence and a time duration
of 1.3 ns, is characterized by a gain of 0.6±0.1 cm-1. The stability of the plasma compression followed by the laser emission is verified.
Received 13 December 2001 相似文献
12.
The strongest portion of the 3ν3 band of SF6 has been recorded at T = 160 and 295 K with Doppler-limited resolution using a tunable laser difference-frequency spectrometer. The structure in this band has been identified with the P, Q, and R branches of one F1u sublevel (with essentially l = 1 character) within the 3ν3 vibrational manifold. Preliminary effective rotational constants have been obtained for this band from which the anharmonic parameters X33, G33, and T33 can be estimated. The role of hot bands and of the other anharmonic sublevels is discussed in relation to prior interpretations of low resolution spectra and of the initial isotope selective stages of CO2 laser photo-dissociation of SF6. 相似文献
13.
This paper presents a hybrid optimization approach for the determination of the optimum laser cutting process parameters which minimize the kerf width, kerf taper, and kerf deviation together during pulsed Nd:YAG laser cutting of a thin sheet of nickel-based superalloy SUPERNI 718 (an equivalent grade to Inconel 718). A hybrid approach of Taguchi methodology and grey relational analysis has been applied to achieve better cut qualities within existing resources. The input process parameters considered are oxygen pressure, pulse width, pulse frequency, and cutting speed. A higher resolution based L27 orthogonal array has been used for conducting the experiments for both straight and curved cut profiles. The designed experimental results are used in grey relational analysis and the weights of the quality characteristics are determined by employing the entropy measurement method. The significant parameters were obtained by performing analysis of variance (ANOVA). The optimized parameters for straight and curved laser cut profiles have been compared. On the basis of optimization results it has been found that the optimal parameter level suggested for straight cut profiles are not valid for curved cut profiles. The application of the hybrid approach for straight cuts has reduced Kt and Kd by 52.37% and 17%, respectively. For curved cuts the approach has reduced Kw and Kt by 8.45% and 44.44%, respectively. The results have also been verified by running confirmation tests. 相似文献
14.
M. Jackson E.M. Telles M.D. Allen K.M. Evenson 《Applied physics. B, Lasers and optics》2001,72(7):815-818
A significantly improved far-infrared laser has been used to generate optically pumped laser emissions from 26 to 150 μm for
CD3OH. Using an X–V-pumping geometry, several new laser emissions have been found for CD3OH. In addition, an increase in power, by factors from 10 to 1000, for many of the previously known shorter-wavelength laser
lines, below 100 μm, has been observed. Frequency measurements for several lines have also been performed and have been reported
to a fractional uncertainty up to ±2×10-7, permitting the spectroscopic assignment of the laser transition. One of the frequency-measured lines, 44.256 μm observed
using the 10R34 pump, has confirmed the assignment of the previously reported FIR emission (n,K;J)=(1,7;20)?(0,8;20)A in the
ground vibrational state.
Received: 26 October 2000 / Published online: 7 February 2001 相似文献
15.
M. Ehrhardt G. Raciukaitis P. Gecys K. Zimmer 《Applied Physics A: Materials Science & Processing》2010,101(2):399-404
Laser-induced backside wet etching (LIBWE) is a promising process for microstructuring of rigid chemical resistant and inert
transparent materials. LIBWE with nanosecond laser pulses has been successfully demonstrated in a number of studies. LIBWE
in a time scale of femtosecond and picosecond pulse durations has been investigated only in a few studies and just on fused
silica. In the present study LIBWE of fluorides (CaF2, MgF2) and sapphire with a mode-locked picosecond (t
p=10 ps) laser at a UV wavelength of λ=355 nm using toluene as absorbing liquid has been demonstrated. The influence of the laser fluence and the pulse number on
the etching rate and the achieved surface morphology was investigated. The etching rate grows linearly with the laser fluence
in the low and high-fluence ranges with different slopes. The achieved etching rates for CaF2 and for sapphire were in the same range. Contrary to CaF2 and sapphire the etching rates of MgF2 were one magnitude less. For backside etching on sapphire at high fluences smooth surfaces and at low fluences ripples pattern
were found, whereas fluoride surfaces showed a trend towards crack formation. 相似文献
16.
In the present experimental work, oscillator strengths of the 4s5s 3S1 → 4snp 3Po2 (18?≤?n?≤?53) Rydberg transitions of zinc are reported. The stepwise laser excitation from the ground state 4s2 1S0 was achieved using three dye laser beams simultaneously pumped by the second (532?nm) and third (355?nm) harmonics of a Q-switched Nd: YAG (Neodymium-doped yttrium aluminum garnet) laser. The vapor containment and detection system was a single wire thermionic diode ion detector operating in space charge limited mode. A trend of the above-mentioned f-values from n?=?18 to 53 versus the principle quantum number n has been presented. Furthermore, continuity has been verified between the discrete f-values and the oscillator strength density at the threshold. 相似文献
17.
The effect of laser irradiation on the optical properties of thermally evaporated Se100?x Te x (x=8, 12, 16) chalcogenide thin films has been studied. The result shows that the irradiation causes a shift in the optical gap. The results have been analyzed on the basis of laser irradiation-induced defects in the film. The width of the tail of localized state in the band gap has been evaluated using the Urbach edge method. As the irradiation time increases, the values of the optical energy gap for all compositions decrease, while tail energy width increases. It is also observed that the optical energy gap decreases with increasing Te content in the alloy. These changes are a consequence of an increment in disorder produced by laser irradiation in the amorphous structure of thin film. 相似文献
18.
3.8 W of cw blue light generated by intracavity frequency doubling of a 946-nm Nd:YAG laser with LBO 总被引:10,自引:0,他引:10
Y. Chen H. Peng W. Hou Q. Peng A. Geng L. Guo D. Cui Z. Xu 《Applied physics. B, Lasers and optics》2006,83(2):241-243
Efficient cw intracavity frequency doubling of a diode-end-pumped Nd:YAG laser operating on 4
F
3/2→4
I
9/2 transitions at 946 nm has been demonstrated. A symmetrical cavity with two composite laser rods was designed, which divides the pump power between the two composite laser rods, allowing for greater power scalability. A 30-mm-long LiB3O5 (LBO) crystal, cut for critical type I phase matching at 57 °C, was used for the intracavity frequency doubling of the laser. A maximum output power of 3.8 W in the blue spectral range at 473 nm has been achieved at 39 W of pump power. The beam quality M2 value is 2.3 in both horizontal and vertical dimensions. PACS 42.55.Xi; 42.65.Ky 相似文献
19.
We report a diode-pumped Nd:YVO4 laser emitting at 1074 nm, based on the 4
F
3/2-4
I
11/2 transition, generally used for a 1064 nm emission. A power of 323 mW at 1074 nm has been achieved in continuouswave (CW)
operation with a fiber-coupled laser diode emitting 18.2 W at 808 nm. Intracavity second-harmonic generation in CW mode has
also been demonstrated with a power of 18 mW at 537 nm by using a LiB3O5 (LBO) nonlinear crystal. 相似文献
20.
Many radiofrequency resonances corresponding to transitions between the two components of a K-type doublet in H2CO and HDCO have been observed using infrared-radiofrequency double resonance inside a CO2 laser cavity. For strong resonances, additional transitions induced by collisions have also been observed and these provide information on collisional processes. The collision-induced transitions also provide a method for assigning the K doublet frequencies in the ground and v4 = 1 states of H2CO, and in the ground, v5 = 1, and v6 = 1 states of HDCO; the rovibrational transitions pumped by the CO2 laser can therefore be determined. The upper state rotational transitions and the infrared frequencies for the transitions in exact coincidence with the CO2 laser lines provide accurate additional data in the analysis of the conventional infrared spectrum of the ν5 and ν6 bands of HDCO. In addition, the 195-μm far-infrared laser line in HDCO, observed by Dangoisse et al. [J. Quantum Electron. QE-13, 730–731 (1977)] has been assigned as the 246,19→236,18 transition in the v6 = 1 state. 相似文献