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1.
利用光反馈半导体激光器产生了低频起伏及关联维数为12.2的高维混沌状态. 实验研究了低频起伏到高维混沌的演变过程. 实验表明,当偏置电流Ib <1.03Ith时,随着反馈强度的降低,低频起伏的峰峰值先增大后减小,平均周期一直减小,直至进入稳定状态,但不能转化为混沌. 当偏置电流Ib >1.03Ith时,随着反馈强度的降低,低频起伏的峰峰值一直增大,平均周期一直减小
关键词:
低频起伏
混沌
半导体激光器
反馈 相似文献
2.
Ablation of organic polymers is described on the basis of photothermal bond breaking within the bulk material. Here, we assume
a first-order chemical reaction, which can be described by an Arrhenius law. Ablation starts when the density of broken bonds
at the surface reaches a certain critical value.
In order to understand the ablation behavior near the threshold fluence, φth, non-stationary regimes must be considered. The present treatment reveals several qualitative differences with respect to models that treat
ablation as a surface process: (i) Ablation starts sharply with a front velocity that has its maximum value just after the onset. (ii) The transition
to the quasi-stationary ablation regime is faster. (iii) Near threshold, the ablated depth h has a square-root dependence
on laser fluence, i.e., h∝(φ-φth)1/2. The ablation velocity is very high even near φth. (iv) With φ≈φth ablation starts well after the laser pulse. (v) The depletion of species is responsible for the Arrhenius tail observed with
fluences φ≤φth. (vi) Residual modification of material has maximum near the threshold. (vii) Stationary regimes of ablation demonstrate change of effective activation energy with laser intensity.
The model calculations are applied to Polyimide (KaptonTM H). Here, differences in single-pulse ablated depth determined from mass loss and profilometry should be about 10 nm.
Received: 16 February 1999 / Accepted: 18 February 1999 / Published online: 28 April 1999 相似文献
3.
Temperature dependence of the turn-on time delay (ton) of uncooled semiconductor laser diodes biased below and above threshold is analyzed in presence of data pattern effect.
We show that even when the laser is biased at or slightly above threshold, the increase in temperature of operation will lead
to increase in the threshold carrier (Nth) and consequently the laser diode will be biased below the threshold again and a significant value of ton will be produced. Thus, knowledge about a value of dc-bias current required to achieve zero ton within wide range of temperature degrees is important when considering uncooled laser diode in high-speed optical communication
systems. The temperature dependence of ton is calculated according to the temperature dependence of Nth and Auger recombination coefficient (C) and not by the well-know exponentional relationship of threshold current with temperature.
The temperature dependence of Nth is calculated according to the temperature dependence of laser cavity parameters. Advanced analytical model is derived in
term of carrier density, recombination coefficients and the injection current (Iinj). The validity of proposed model is confirmed by a numerical method. In addition, approximated models are included where
under specified assumptions the proposed model reduces to the well-known approximate models of ton. According to our typical values and at a specified value of modulation current, the dc-bias one (Iib) should be increased from Iib = Ith to Iib ≈ 1.25 and 1.5Ith in order to achieve approximately zero ton when the temperature increases from 25°C to 55°C and 85°C, respectively. 相似文献
4.
Chaotic dynamics and chaos synchronization in photonic crystal (PC) lasers with optical feedback are investigated numerically. The effect of various system parameters such as amplitude reflectivity of the external mirror “r”, external cavity length “Le”, and injection current “I” on system dynamics is addressed in detail. Simulation results are presented using MATLAB to address system behavior. The parameters r, Le, and I are varied over the ranges (0.05–0.25), (2.8–3.2 mm), and (1.1Ith–2Ith), respectively. The results indicate that very small parameter mismatches between the transmitter laser and receiver laser affect strongly complete chaos synchronization between them. 相似文献
5.
6.
Zhenbao Feng Haiquan Hu Shouxin Cui Wenjun Wang Canyun Lu 《Central European Journal of Physics》2009,7(4):786-790
The electronic and optical properties of InAs in core-level spectra are calculated using the full-potential linearized augmented
plane wave plus local orbitials (FP-LAPW +lo) method. The real and imaginary parts of the dielectric function ε(ω), the optical absorption coefficient I(ω), the reflectivity R(ω), the refractive index n(ω), and the extinction coefficient k(ω)are calculated. All these values are in good agreement with the experimental data. The effect of spin-orbit coupling on optical
properties is also investigated and found to be quite small.
相似文献
7.
Ramazan Koc 《Czechoslovak Journal of Physics》2005,55(9):1135-1140
An approximate method is suggested to obtain analytical expressions for the eigenvalues and eigenfunctions of the some quantum
optical models. The method is based on the Lie-type transformation of the Hamiltonians. In a particular case it is demonstrated
that E × ɛ Jahn-Teller Hamiltonian can easily be solved within the framework of the suggested approximation. The method presented
here is conceptually simple and can easily be extended to the other quantum optical models. We also show that for a purely
imaginary coupling the E × ɛ Hamiltonian becomes non-Hermitian but Pσ0-symmetric. Possible generalization of this approach is outlined.
Presented at the 3rd International Workshop “Pseudo-Hermitian Hamiltonians in Quantum Physics”, Istanbul, Turkey, June 20–22,
2005. 相似文献
8.
Jesús?álvarez-Ruiz Marien?López-Arias Rebeca?de?Nalda Margarita?Martín Andrés?Arregui Luis?Ba?ares 《Applied Physics A: Materials Science & Processing》2009,95(3):681-687
The formation of cationic clusters in the laser ablation of CdS targets has been investigated as a function of wavelength
and fluence by mass spectrometric analysis of the plume. Ablation was carried out at the laser wavelengths of 1064, 532, 355,
and 266 nm in order to scan the interaction regimes below and above the energy band gap of the material. In all cases, the
mass spectra showed stoichiometric Cd
n
S
n
+ and nonstoichiometric Cd
n
S
n−1+, Cd
n
S
n+1+, and Cd
n
S
n+2+ clusters up to 4900 amu. Cluster size distributions were well represented by a log-normal function, although larger relative
abundance for clusters with n=13, 16, 19, 34 was observed (magic numbers). The laser threshold fluence for cluster observation was strongly dependent on
wavelength, ranging from around 16 mJ/cm2 at 266 nm to more than 300 mJ/cm2 at 532 and 1064 nm. According to the behavior of the detected species as a function of fluence, two distinct families were
identified: the “light” family containing S2+ and Cd+ and the “heavy” clusterized family grouping Cd2+ and Cd
n
S
m
+. In terms of fluence, it has been determined that the best ratio for clusterization is achieved close to the threshold of
appearance of clusters at all wavelengths. At 1064, 532, and 355 nm, the production of “heavy” cations as a function of fluence
showed a maximum, indicating the participation of competitive effects, whereas saturation is observed at 266 nm. In terms
of relative production, the contribution of the “heavy” family to the total cation signal was significantly lower for 266 nm
than for the longer wavelengths. Irradiation at 355 nm in the fluence region of 200 mJ/cm2 has been identified as the optimum for the generation of large clusters in CdS. 相似文献
9.
利用光纤环长外腔光反馈半导体激光器产生了频谱平坦的宽带混沌激光,其对应的激光频谱可有效地隐藏外腔的谐振频率,增加了系统的保密性.通过单向耦合方式,将产生的混沌激光注入到另一个参数相近的半导体激光器中,实现了平坦宽带混沌同步输出,两同步激光器输出的相关系数达到084.同时实验研究了注入强度和主从激光器的频率失谐对同步质量的影响,结果表明在强光注入锁定下,在很大频率失谐范围内均可实现同步,而且注入强度越大,主从激光器输出的相关系数越大,维持混沌同步所允许的频率失谐范围越大.
关键词:
混沌同步
单向光纤环
光反馈
半导体激光器 相似文献
10.
The stationary properties of a saturation laser model with cross-correlation between the real and imaginary parts of the quantum
noise are investigated theoretically. Using the Novikov theorem and the Sargent technique, we obtain the analytic expressions
of the stationary probability density distribution, the mean, the variance and the skewness of the saturation laser model.
The cross-correlation coefficient λ and other parameters can make the stationary probability density distribution P
st
(I) generate interesting two-extrema structure, one-extremum structure, or no-extremum structure. It is clearly found that a
first- order-like-transition is induced by the coupling strength |λ| of the complex quantum noise terms in the saturation laser model. When the laser system is operated above the threshold,
the mean 〈I〉 becomes larger and the output of the laser intensity increases; however the coupling strength |λ| attenuates the output of the laser intensity. When the laser is operated near and below the threshold, the mean 〈I〉 becomes smaller, the output of the laser intensity decreases, and |λ| still attenuates the output of the laser intensity. When a periodic signal is added to a saturation laser model with cross-correlation
between quantum noise terms, the interesting stochastic resonance phenomena occur at λ=0. The noise intensity Q decreases the values of the resonance peak, however, the amplitude of the periodic signal B enhances the values of the resonance peak. 相似文献
11.
F. Cornacchia A. Di Lieto P. Maroni P. Minguzzi A. Toncelli M. Tonelli E. Sorokin I. Sorokina 《Applied physics. B, Lasers and optics》2001,73(3):191-194
We present the results obtained with a Ho,Tm:YLF crystal grown at a new crystal growth facility in Pisa. The optical quality
of the sample has been tested by studying its performance as the active medium of a laser operating at 2.06 μm. We employed
three different pump laser sources: a Ti:sapphire, a diode (both tuned at 793 nm) and, for the first time, a continuous-wave
Co:MgF2 laser, tuned at 1.682 μm. At room temperature the best slope efficiency was 30 % in the case of “red” pumping, and 59 % in
the case of “infrared” excitation. The typical lasing threshold is about 100 mW.
Received: 14 March 2001 / Revised version: 15 June 2001 / Published online: 19 September 2001 相似文献
12.
V. Yu. Osipov 《Technical Physics》1998,43(9):1075-1082
Focusing of a high-power laser beam, whose initial wave front is deformed by spherical aberration and astigmatism, in a medium
with refractive-index nonlinearity is investigated by the computer experiment method. It was found that the extended formations
which arise near the focus are no longer diffraction catastrophes, since they are structurally unstable. It is shown that
weak disturbances of the shape of the initial wave front produce extremely strong distortions of the optical field in the
focusing region. As the wave propagates in the z direction, spatial chaos in the distribution of the optical field develops in the region of focusing (from 137 to 142 mm).
Optical turbulence arises in the focusing region as a result of self-diffraction of light by self-induced nonuniformities
of the refractive index of the medium. After the region with the smallest cross section of the formation near the focus, the
three-dimensional optical field has the form of chaotically dispersing “splashes” and extended “filamentary ejecta.”
Zh. Tekh. Fiz. 68, 74–83 (September 1998) 相似文献
13.
V. E. Arkhipov V. E. Startsev V. P. Dyakina J. Klamut Ya. M. Mukovskii A. Czopnik 《JETP Letters》1998,68(1):42-46
Magnetization measurements were performed on a lanthanum manganite La0.9Sr0.1MnO3 single crystal in the temperature interval 4.2–300 K and magnetic field interval 50 Oe-55 kOe in two sample cooling regimes:
1) cooling down to 4.2 K in a high (55 kOe) magnetic field, and 2) cooling in a “zero” field. It is shown that the temperature
dependences of the magnetization M(T) are substantially different in these regimes. Pronounced anomalies of M(T) were observed at temperatures T*=103 K and T
c
=145 K. The first anomaly is attributed to a structural transition, while the second one corresponds to a ferromagnet-paramagnet
phase transition. The magnetization of a La0.9Sr0.1MnO3 single crystal in the cooling regimes studied shows typical “spin-glass” behavior.
Pis’ma Zh. éksp. Teor. Fiz. 68, No. 1, 39–43 (10 July 1998) 相似文献
14.
A. I. Akhiezer A. A. Isaev S. V. Peletminskii A. P. Rekalo A. A. Yatsenko 《Journal of Experimental and Theoretical Physics》1997,85(1):1-12
This paper discusses how an electromagnetic field consisting of a superposition of a constant magnetic field and a field of
laser type can affect nuclear beta decay. In general it is not assumed that the intensities of the two types of fields are
small compared to the characteristic field H
cr*=β
1
H
cr, where H
cr=m
2
c
3/eℏ and the quantity β
1 depends on the energy liberated in the decay and the configuration of the electromagnetic field. For nonrelativistic decays
the quantity β
1 is found to be of the same order as the maximum kinetic energy of an electron referenced to its rest energy β
1∼I≪1. It is assumed that the frequency of the wave field satisfies ℏω/mc
2⩽I. The behavior of the probability for the process is studied over a wide range of the fundamental parameters that characterize
the fields. Corresponding asymptotic expressions are derived in the “weak”-and “strong”-field regimes. Also discussed are
so-called interference corrections to the unperturbed decay probability, which cannot in principle be studied by the methods
of perturbation theory. It is shown that the times and distances that are important in generating these contributions exceed
the parameters of the unperturbed processes, just as in the case of a plane-wave field previously investigated in detail by
Nikishov and Ritus. However, in contrast to the case of a pure wave field, when a system is simultaneously subjected to a
constant magnetic field and a wave field, the degree to which these characteristic regions are enlarged can depend not only
on the intensities of the electromagnetic fields but also on their rates of change, even in the limit in which the wave field
is slowly varying.
Zh. éksp. Teor. Fiz. 111, 3–24 (January 1997) 相似文献
15.
M. Maaza B. D. Ngom S. Khamlich J. B. Kana Kana P. Sibuyi D. Hamidi S. Ekambaram 《Journal of nanoparticle research》2012,14(2):714
The possibility of synthesizing binary oxides nanoparticles in a nano-scaled form by laser liquid solid interaction using
a NdYAG “1.064 μm” as an irradiating laser source is reported. The case of MoO3−δ is emphasized. Furthermore, it is demonstrated that the Mo–O electronic valence can be controlled through the coupling effects
of oxygen enriched nature of the used coating liquid layer, namely pure H2O or H2O2 and the laser beam fluence. Dark blue hydrated molybdic pentoxide Mo2O5·xH2O and yellow molybdenum trioxide MoO3 nano-suspensions were reproducibly synthesized with hydrogen peroxide and water, respectively, at a relatively high ablation
rate. The average size of the molybdenum trioxide nanoparticles was about <ϕ>~8 nm, slightly larger than the molybdic pentoxide
ones “<ϕ>~6.2 nm”. 相似文献
16.
N. Pavel 《Laser Physics》2010,20(1):215-221
Continuous-wave (CW) simultaneous laser emission on the 0.9-μm 4
F
3/2 → 4
I
9/2 transition and the 4
F
3/2 → 4
I
11/2 transition at 1.06 μm is obtained in Nd-based laser crystals of thin-disk geometry and using a multi-pass pumping scheme.
A Nd:Y3Al5O12 (Nd:YAG) thin disk emitted simultaneous laser radiation at 946 and 1064 nm with 5.1 W output power, and Nd:YVO4 and Nd:GdVO4 thin-disk lasers with more than 3 W output power at 0.91 and 1.06 μm were realized. The ratio between the output power at
one of the wavelengths and the total output power could be varied by the laser resonator design. An intracavity frequency-doubled
Nd:YVO4 thin-disk laser with alternate green at 532 nm and “deep-blue” at 457 nm generation of high average output powers is demonstrated. 相似文献
17.
A high-power, unmodulated frequency standard laser light with low running cost is a powerful tool for industrial measurement involving laser calibration and interferometry in length and shape. To obtain such a laser light, we developed an intermittent frequency offset locked laser (IFOL laser). This laser system, composed of an iodine stabilized He-Ne laser (I2SL) and a high-powered symmetric three-mode He-Ne laser (HP-3ML, optical output=5 mW), provides two stabilization operational modes: (1) independent mode (I-mode) and (2) slave mode (S-mode). Utilizing the frequency pulling effect, HP-3ML is stabilized at the condition of symmetric three-mode oscillation, and a 3 mW single-mode light with frequency instability of 10-12 is obtained (I-mode). When the optical frequency deviates from the allowed limit during I-mode, HP-3ML is temporarily offset-locked to I2SL (S-mode) with frequency resettability of 10-10 and frequency instability of 10-12. After completion of the drift reset in S-mode, HP-3ML is stabilized in I-mode again, and then I2SL is turned off. In a typical case of allowed drift in ±1 MHz, repetitive operation of I-mode for 10 days and S-mode for 5 min was satisfactory. Such an intermittent operation reduces the working time of I2SL dramatically, resulting in low running cost that enables long-term use in industrial measurement. 相似文献
18.
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
19.
O. Utéza N. Sanner B. Chimier A. Brocas N. Varkentina M. Sentis P. Lassonde F. Légaré J. C. Kieffer 《Applied Physics A: Materials Science & Processing》2011,105(1):131-141
Surface ablation of a dielectric material (fused silica) by single femtosecond pulses is studied as a function of pulse duration
(7–450 fs) and applied fluence (F
th<F<10F
th). We show that varying the pulse duration gives access to high selectivity (with resolution ∼10 nm) for axial removal of
matter but does not influence the transverse ablation selectivity, which only depends on the normalized applied fluence F/F
th. The ablation efficiency is shown to be inversely dependent on the pulse duration and saturates with respect to the applied
fluence earlier at ultra-short pulse durations (≤30 fs). The deduced optimal fluence F
opt corresponding to the highest ablation efficiency for each pulse width defines two regimes of laser application. Below F
opt, the removed material depth can be accurately adjusted in a large range (∼40–200 nm) as a function of the applied fluence
and the morphology of the ablated pattern almost reproduces the Gaussian beam distribution. Above F
opt, the material removal depth tends to saturate and the morphology of the ablated pattern evolves to a top-hat distribution.
The coupled evolution of depth and morphology is related to the dynamics of formation of dense plasma at the surface of the
material, acting as an ultra-fast optical shutter. 相似文献
20.
Shigeo Yamaguchi Hitoshi Kurusu Yoichi Kawakami Shizuo Fujita Shigeo Fujita 《Superlattices and Microstructures》1998,23(6):1189-1195
Photo-pumped lasing properties have been investigated in a CdSe/ZnSe/ZnSSE single quantum wells (SQWs) with the well-layer thickness (LW) of 1, 2 and 3 monolayer (ML). At 20 K, the laser threshold for the SQW withLW = 1 ML was the lowest in spite of the smallest active layer thickness. The carrier (exciton) sheet density at the threshold (n)thwas estimated to be as low as 7 × 1010cm−2, which is well below Mott's screening density. Time-resolved photoluminescence has revealed that the localized biexciton band, whose peak energy agrees with the lasing peak, appeared on the low-energy side of the main PL peak at this level of carrier concentrations. Theoretical calculation has also shown that the localized biexciton recombination has to be taken into account for the lasing process. On the contrary, thenthvalues of the SQWs with 2 and 3 ML are 1 order of magnitude larger than that of the SQW with 1 ML. This may be due to the smaller oscillator strength of both localized excitons and localized biexcitons because of the larger inhomogeneous broadening, resulting in an increased carrier density for achieving optical gain sufficient to overcome the reflection losses. 相似文献