共查询到20条相似文献,搜索用时 31 毫秒
1.
Woodward J.R. Cobb S.H. Shen K. Gole J.L. 《Quantum Electronics, IEEE Journal of》1990,26(9):1574-1587
Evidence is obtained which demonstrates the potential for developing purely chemical visible lasers based on rapid near-resonant energy transfer from metastable excited triplet states of germanium and silicon monoxide (a 3Σ+,b 3Π) to select metal atoms. In this study, the Group IIIA metal atoms were chosen as the energy receptors for the energy transfer-pump sequence. Excited triplet states were generated from the Ge-O3, Ge-N2, Si-N2O, and Si-NO2 reactions; the bulk of the experimental results was obtained with a germanium-based system. The energy stored in the long-lived triplet states is transferred to pump X 2P 1/2 thallium, indium, and gallium atoms to their lowest lying 2 S 1/2 states. The authors observe a system of temporal behavior which suggests the creation of a population inversion producing a gain condition and forming the basis for full cavity oscillation on the Tl 72S 1/2-6P 3/2 transition at 535 nm 相似文献
2.
A generalized model for 3-μm (4I 11/2 →4I 13/2)Er lasers is proposed. The essential energy transfer processes present in the single-doped Er 3+ systems (up-conversion from 4I 13/2, up-conversion from 4 I 11/2, cross-relaxation from 4S 3/2), as well as those present in Cr3+ codoped Er 3+ systems, are taken into account. In the frame of this model, the main features of 3 μm Er3+ lasers, such as long pulse or CW operation, the change of emission wavelength as a function of pumping conditions, and the effects of codoping with Ho3+ or Tm3+ ions, are explained 相似文献
3.
A new organic electrooptic crystal, 2,6-dibromo-N-methyl-4-nitroaniline, is reported. The crystal structure was determined by X-ray diffraction (orthorhombic, space group Fdd2, point group mm2, Z =16, a =11.745 Å, b =29.640 Å, c =10.807 Å). The refractive indexes were measured at several wavelengths between 500 and 1100 nm (at 632.8 nm, n a=1.90, n b=1.62, and n c=1.48) and fit the data to a single oscillator Sellmeier equation. A report is presented on measurements of the linear electrooptic effect, yielding the combined coefficients n a 3r 13-n c3 r 33, as well as the first known measurements of the quadratic electrooptic effect in an organic crystal, yielding the coefficients r 42 and r 51 at 514.5, 632.8, and 810 nm. Good agreement is found between the observed dispersion in the electrooptic coefficients and that predicted by the simple two-level dispersion model 相似文献
4.
A report is presented of the thermal shifts of eleven of the twelve lines from the 4F 3/2 Stark energy levels to the 4I 11/2 energy levels in an Nd:YAG laser for a temperature change from 20-200°C. The thermal shift difference between the Stark sublevels R 1, R 2 in 4F 3/2 is found to be about -0.6±0.6 cm-1/100°C. Within experimental uncertainty, all of the lasing lines either moved to longer wavelength or remained unchanged with increasing temperature 相似文献
5.
Stimulated anti-Stokes Raman scattering at 145.7 nm in inverted Se is generated by photolysis of OCSe at 193 nm and the subsequent up-conversion of 205.1-nm pump radiation. The tuning profile is characterized with OCSe pressure, the energies and relative timing of the pump and photodissociation lasers, and CO and Ar buffer-gas pressure. The use of CO as a buffer gas is discovered to be detrimental to the anti-Stokes output. Sixteen competing stimulated emission channels are found to suppress anti-Stokes emission on exact 4p 4 1S 0-4p 3 5s 3 P 01 pump resonance 相似文献
6.
Beach R. Shinn M.D. Davis L. Solarz R.W. Krupke W.F. 《Quantum Electronics, IEEE Journal of》1990,26(8):1405-1412
A spectroscopic investigation of the biaxial crystal yttrium orthosilicate doped with Nd3+(Nd3+:Y2SiO5) has been performed. Spectrally and orientationally resolved emission cross sections necessary for the evaluation of laser performance on the Nd3+ 4F 3/2-4I 9/2 and 4F 3/2-4I 11/2 transitions have been determined. The Judd-Ofelt theory has been applied to measured values of optical absorption line strengths to obtain the orientation averaged intensity parameters: Ω2-3.34×10-20 cm2, Ω 4=4.35×10-20 cm2, and Ω6=5.60×10-20 cm2. These Judd-Ofelt intensity parameter values are significantly different from those previously reported by A.M. Tkachuk et al. Using these intensity parameters, the Nd3+ 4F 2 metastable state lifetime is predicted to be 225 μs. Measured low Nd concentration 4F 3/2 lifetimes of 214 μs indicate a high radiative quantum efficiency. Because of the Stark level splitting of the Nd3+ 4F 3/2 and 4I 9/2 manifolds, laser operation at twice one of the Cs atomic resonance filter acceptance wavelengths is possible 相似文献
7.
Connectivity properties of a packet radio network model 总被引:16,自引:0,他引:16
Philips T.K. Panwar S.S. Tantawi A.N. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》1989,35(5):1044-1047
A model of a packet radio network in which transmitters with range R are distributed according to a two-dimensional Poisson point process with density D is examined. To ensure network connectivity, it is shown that πR 2D , the expected number of nearest neighbors of a transmitter, must grow logarithmically with the area of the network. For an infinite area there exists an infinite connected component with nonzero probability if π R 2D >N 0, for some critical value N 0. It is shown that 2.195<N 0<10.526 相似文献
8.
A dispersion formula ϵ*eff(f )=ϵ* -{ϵ*-ϵ*eff(0)}/{1+( f /f 50)m}, for the effective relative permittivity ϵ*eff(f ) of an open microstrip line is derived for computer-aided design (CAD) use. The 50% dispersion point (the frequency f 50 at which ϵ*eff(f 50)={ϵ *+ϵ*eff(0)}/2}) is used a normalizing frequency in the proposed formula, and an expression for f 50 is derived. To obtain the best fit of ϵ *eff(f ) to the theoretical numerical model, the power m of the normalized frequency in the proposed formula is expressed as a function of width-to-height ratio w / h for w /h ⩾0.7 and as a function of w /h , f 50, and f for w /h ⩽0.7. The present formula has a high degree of accuracy, better than 0.6% in the range 0.1<w /h ⩽10, 1<ϵ*⩽128, and any height-to-wavelength ratio h /λ0 相似文献
9.
Hong-Yuan Shen Zeng R.R. Yu-Ping Zhou Yu G.F. Cheng-Hui Huang Zheng-Dong Zeng Zhang W.J. Ye Q.J. 《Quantum Electronics, IEEE Journal of》1991,27(10):2315-2318
The oscillation condition of a simultaneous multiple wavelength laser has been established and used to analyze the possibility of simultaneous oscillation in various neodymium host crystals, such as Nd:YAG, Nd:YLF, Nd:BEL, and Nd:YAP crystals at the transitions from 4F 3/2-4I 13/2 and 4F 3/2-4I 11/2. It is shown that this kind of laser can be realized in all the described crystals in a pulsed state. In general, continuous wave (CW) operation, however, can only be achieved for Nd:YAP. On the basis of these results, CW simultaneous double wavelength lasing has been achieved in a Nd:YAP crystal for the first time at both 1.0795 μm and 1.314 μm 相似文献
10.
Energy transfer from selectively formed metastable states of SiO is used to pump sodium-atom laser amplifiers at λ≈569 nm (4d 2D -3p 2P ), λ≈616 nm (5s 2S -3p 2 P ), and λ≈819 nm (3d 2D -3p 2P ). The a 3Σ+ and b 3Π states of SiO are generated in high yield from the Si+N2O→SiO+N2 reaction. The energy stored in the triplet states is transferred in a highly efficient collisional process to pump sodium atoms to their lowest excited 3d 2 D , 4d 2D , and 5s 2S states. Adopting a sequence in which high concentrations of silicon and sodium atoms are mixed and oxidized, a continuous amplification (gain condition) is monitored which suggests the creation of a population inversion among the receptor sodium-atom energy levels and forms the basis for full cavity oscillation on the Na4 d 2D -3p 2P transition at 569 nm 相似文献
11.
An observation is reported of a large number of new laser lines from 12CD3F gas optically pumped with a continuously tunable high-pressure pulsed CO2 laser. Making use of the coincidence of the 10 μm P and R branches of CO2 with the v 3 and v 6 vibrational-rotational absorption bands of 12CD3F, 180 laser lines were found in the wavenumber range between 8 and 55 cm-1, all of them yet unknown; these lines are studied for characteristic properties of laser action. All laser lines are assigned as pure rotational transitions in the vibrational excited or ground states 相似文献
12.
The OMDR (optical-microwave double resonance) spectrum of 87 Rb with the aim of using a frequency-stabilized GaAs semiconductor laser instead of an Rb lamp as a pumping source in a gas-cell-type Rb frequency standard. Natural isotope 87Rb was sealed in a glass cell with buffer gases (Ar/N 2=1.2, total pressure=39 torr). The double resonance signal in the 5P 1/2(F =2)←5S 1/2( F =1) transition appearing at the resonance to the F =2←1 hyperfine transition of the 5S 1/2 state was detected. The optimum operational cell temperature was 56°C. The peak-to-peak frequency width of the atomic hyperfine resonance discriminator used to stabilize the microwave frequency shifts induced by detuning of the laser frequency, changes in the laser and microwave powers, and temperature drift of the cell were investigated 相似文献
13.
Csiszar I. Narayan P. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》1991,37(1):18-26
The Gaussian arbitrarily varying channel with input constraint Γ and state constraint Λ admits input sequences x =(x 1,---,X n) of real numbers with Σx i2⩽n Γ and state sequences s =(S 1,---,s n ) of real numbers with Σs i2⩽n Λ; the output sequence x +s +V , where V =(V 1,---,V n) is a sequence of independent and identically distributed Gaussian random variables with mean 0 and variance σ2. It is proved that the capacity of this arbitrarily varying channel for deterministic codes and the average probability of error criterion equals 1/2 log (1+Γ/(Λ+σ2)) if Λ<Γ and is 0 otherwise 相似文献
14.
Ashley T. Dean A.B. Elliott C.T. McConville C.F. Whitehouse C.R. 《Electronics letters》1988,24(20):1270-1272
Molecular-beam epitaxy has been used for the first time to fabricate np junctions in InSb grown onto p -type InSb (100) substrates. Diodes formed by the epitaxial growth of a silicon-doped layer on undoped homoepitaxial material exhibited a bulk generation-recombination-limited R 0A value of 105 Ω cm2 and D λpk * of 3×1012 cm Hz1/2 W-1 at liquid nitrogen temperature 相似文献
15.
A simple expression for the noise in the photocurrent generated by the detection of light from an ideal superluminescent source is derived using a quantum amplifier model. The excess noise factor X is found to be related to the photocurrent I d, electronic charge e , spontaneous emission coupling factor K , and full width at half maximum power of the emission spectrum Δv 1/2 by the expression X =0.664 I d/eK Δv 1/2. Implications of this result for the performance of fiber-optic gyroscopes using superluminescent-diode (SLD) light sources and for the design of low-noise SLDs are discussed 相似文献
16.
Sutter K. Bosshard C. Ehrensperger M. Gunter P. Twieg R.J. 《Quantum Electronics, IEEE Journal of》1988,24(12):2362-2366
Single crystals of 2-methyl-4-nitro-N -methylaniline (MNMA) have been grown from the melt. The crystal structure was determined (orthorhombic, Pna2I (2 mm), Z =4, a =17.788(6) Å, b =11.893(4) Å, c =3.907(2) Å). The refractive indexes n a and n c were measured between 500 and 700 nm [ n a(633 nm)=2.148(10), n c(633 nm)=1.520(3)]. The nonlinear optical susceptibilities coefficients r 31=8 pm/V and r 33=7.5 pm/V were determined. Most optical properties can be explained in terms of molecular orientation and polarizability 相似文献
17.
Expressions are obtained for specifying the optimal error probability (minimum P e) thresholds λ01 and λ02 for the traditional and modified sign detectors, respectively. These thresholds are shown to depend on the parameters p , P 1, and M where: M is the number of observations z i used in the test statistic; P 1=P (H 1 ) is the prior probability for hypothesis H 1 that signal s 1 is present and 1-P 1 =P (H 0) corresponds to the hypothesis H 0 that signal s 0 is present; and p =Pr{z i⩾0|H 1} with s 0=0 for the traditional sign detector and p =Pr{z i⩾λ|H 1 }=Pr{z i<λ|H 0} with λ =(s 0+s 1)/2 for the modified sign detector. The expressions for λ01 and λ02, are given explicitly, and shown to be independent of P 1 for sufficiently large M . Optimal P e versus M performance curves, corresponding to both versions of the sign detector, are obtained for a representative range of values for p and P 1 相似文献
18.
A pulsed 4.3-μm CO2 laser was used to optically pump mixtures of CO2 and He, and create transient gain at 9 and 10 μm. A conventional continuous-wave CO2 laser operating on both regular and sequence bands measures this transient gain, and determined the ν3 (asymmetric stretching)-mode vibrational temperature T 3. The measured values of T 3 are generally much higher than those attained in discharge-excited CO2. It is shown that a Treanor distribution must be used to describe the populations in the ν3 -mode when dilute mixtures of CO2 in He are optically pumped to ν3-mode temperatures of 3000 to 4000 K. Under these conditions the sequence-band gain coefficients are almost equal to those on the regular bands. The collisional relaxation of energy from the ν3 mode shows evidence of fast V -T relaxation at high values of T 3, followed by a slower relaxation rate characteristic of the 0001 population lifetime 相似文献
19.
Barnes W.L. Laming R.I. Tarbox E.J. Morkel P.R. 《Quantum Electronics, IEEE Journal of》1991,27(4):1004-1010
A detailed set of measurements is presented on determining the emission and absorption cross sections of Er3+ doped fibers for the 4I 13/2→4I 15/2 transition. Two techniques are employed: the Fuchtbauer-Ladenberg analysis, based on spectroscopic data, and a more direct technique involving optical saturation of the transition. The cross sections, and in particular their ratio, are significantly different for the two techniques. Possible reasons for this are discussed, and it is concluded that the Fuchtbauer-Ladenberg approach is inappropriate in this situation 相似文献
20.
Hongyuan Shen Tianguan Lian Ruirong Zheng Yuping Zhou Guijang Yu Chenghui Huang Hong Liao Zhengdong Zheng 《Quantum Electronics, IEEE Journal of》1989,25(2):144-146
A method for the simultaneous measurement of the stimulated emission cross section and fluorescence lifetime by studying the relation between laser parameters and the laser relaxation oscillation frequency is discussed. The stimulated emission cross section for the 4F 3/2-4I 13/2 transition of Nd3+ ion in YAP crystal was measured to be (22±1)×10-20 cm2 相似文献