Effect of exit and injection rates on phase-dependent transient evolution of gain without inversion

It is shown that in an open Λ-type system with spontaneously generated coherence, the transient evolution rule of the gain of lasing without inversion (LWI) is very sensitive to variation of the relative phase φ between the probe and driving fields; the variety of the atomic exit rateγ_0 and the ratio C of the atomic injection rates also have a considerable effect on the phase-dependent transient evolution rule of LWI gain. We find that whenφ=0, the transient and stationary LWI gain increases with C increasing but decreases with γ_0 increasing; whenφ≠0 , the effect of C andγ_0 on LWI gain is just opposite to that when φ=0 ; in order to get the largest transient and stationary LWI gain, we need selecting suitable values of φ,γ_0 and C.     

开放的V型三能级系统中SGC对传播效应的影响

利用密度矩阵运动方程和光场传播方程的数值计算结果,研究在Doppler展宽的开放的V型三能级无反转激光（LWI）系统中自发辐射诱导相干（SGC）对传播效应的影响及原子退出速率（r0）和注入速率比（s）对SGC相关的传播效应的调制作用,以寻找获得更大LWI增益和探测场强度的途径。研究结果表明,随着传播距离的增加,IWI增...     

Doppler展宽的四能级系统无反转激光的传播效应

在考虑Doppler效应下,通过理论分析和数值模拟研究了传播效应对开放四能级系统中的无反转激光特性的影响.研究发现:探测场和驱动场同向传输对系统获得无反转激光更为有利,要想提高探测激光的增益不仅要选取合适的入口处驱动场Rabi频率值,而且选取适当的驱动场和探测场初始失谐值对于提高激光增益也极为关键;随传播距离的增大,探测场上下能级粒子数一直满足无反转,而探测场上能级和驱动场上能级间的粒子数随传播距离的增大发生了Raman反转.     

Impact of the sample thickness and γ-irradiation dose on the occurrence of radiation-induced optical effects in chalcogenide vitreous semiconductors of the Ge-Sb-S system

The impact of the sample thickness and γ-irradiation dose on the magnitude of total and static radiation-induced optical effects in chalcogenide vitreous semiconductors is studied using the example of Ge-Sb-S alloys of the Ge_23.5Sb_11.8S_64.7 chemical composition. It is established that, at comparable ratios between the doses of γ-irradiation (Φ = 3.0 and 7.72 MGy) and thicknesses of the samples (d = 1.0 and 1.7 mm), the dose change more essentially affects the occurrence of radiation-induced optical effects in the semiconductors examined.     

开放的梯型无反转激光系统Doppler展宽对增益的影响

研究表明：当探测场和驱动场都失谐时，Doppler展宽的变化仅对无反转地．增益的检大值有明显的影响，而且极大值随Doppler展宽的增加而迅速减小；当探测场失谐驱动场共振且Doppler展宽取适当值时，系统可以获得增益极大值中的最大值；这个最大值随原子注入速率比的增加而增加，频率上转换的程度越高，为达到这个极大值所要求的Doppler展宽越小；在开放的梯型无反转激光（LWI）系统中Doppler展宽对增益的影响与从其他LWI系统中得到的有明显的差别。     

Quaternary (FeIn2S4)x(MnIn2S4)1 ? x alloys and photosensitive structures on their basis

Using directional crystallization of the melt of the (FeIn₂S₄) _x (MnIn₂S₄)_{1 − x} alloy, homogeneous crystals of a similar atomic composition are grown over the entire range of compositions 1 ≥ x ≥ 0. It is established that the crystals of the continuous series of quaternary alloys in the range x = 0–1 crystallize in the spinel structure and lattice parameter a linearly depends on x. It is established that it is possible to obtain In(Al)/(FeIn₂S₄) _x (MnIn₂S₄)_1–x photosensitive structures. Room-temperature spectra of relative quantum efficiency of photoconversion of the In(Al)/(FeIn₂S₄) _x (MnIn₂S₄)_{1 − x} structures fabricated for the first time are obtained. From the analysis of these spectra, activation energies of direct and indirect band-to-band transitions for the crystals of the (FeIn₂S₄) _x (MnIn₂S₄)_1–x alloys are determined and the dependence of these parameters on the composition of the position-disordered phases of mentioned alloys is discussed. It is concluded that the crystals of the (FeIn₂S₄) _x (MnIn₂S₄)_{1 − x} alloys can be used in broadband photoconverters of optical radiation.     

Parasitic aware impedance matching techniques for RF amplifiers

This paper analyzes the impact of non-idealities of the lumped passive elements (inductor and capacitor) in the matching networks of RF amplifiers. This work infers that the representation of performance matrices of a matching network like sensitivity and harmonic rejection; in terms of input reflection coefficient (S ₁₁) is more convenient than the transfer functions. Expression of S ₁₁ of widely used L-, π- and T-networks have been derived as a function of inductor quality factor (Q _L ), capacitor quality factor (Q _C ) and transformation ratio. This formulation shows that the matching performance degrades severely due to component non-idealities. To circumvent this degradation, a modified set of design equations have been proposed for the L-network and the same has been extended for π- and T-network. Simulation results show that network synthesized on the basis of proposed set of equations nullify the effect of non-idealities by 70–80% in L-network and 10–20% in π-network but minor improvement in T-network.     

Discovery of the (In2S3)x(MnIn2S4)1 ? x solid solutions and fabrication of photosensitive structures based on them

A technology of growing single crystals of (In₂S₃) _x (MnIn₂S₄)_{1 − x} solid solutions that provides control over their atomic composition in the entire concentration range 0 ≤ x ≤ 1 is developed. It is shown that, in the range x = 0–1, the single crystals have the cubic spinel structure and the unit cell parameter a follows the linear dependence on x. The exponential character of the temperature dependence of resistivity of solid solutions, on which the first photosensitive Cu/(In₂S₃)x(MnIn₂S₄)_{1 − x} structures are obtained, is revealed. The first photosensitivity spectra of these structures are obtained, and, based on these spectra, dependences of energy of the direct and indirect band-to-band transitions on the composition x are determined. The possibility of applying these structures in broad-band photoconverters of optical radiation is concluded.     

Flicker phase noise in transistorized amplifier

In this article, the relation between the frequency stability due to the flicker phase noise (phase-power spectrum densityS _Δϕ1'(f) in frequency domain and Allen variance γ _y ² {τ} in time domain) and the parameters of the transistors has been derived and experimentally verified.     

Electrodeposited Gd2Zr2O7 and Gd2O3 Buffer Layers for YBa2Cu3O7-δ Superconductors

Non-vacuum electrodeposition (ED) was used to prepare a biaxially textured Gd₂Zr₂O₇ (GZO) and GZO/Gd₂O₃ (GO) buffer layer on a Ni-W substrate. The YBa₂Cu₃O_7−δ (YBCO) superconductor was deposited by pulsed-laser deposition (PLD) on a simplified ED-GZO and ED-GZO/ED-GO buffer layer. The buffer layers and YBCO superconductor were characterized by X-ray diffraction (including θ/2θ, pole figure, omega scans, and phi scans) and atomic force microscopy. Full-width at half maximum values of the omega (ω) and phi (Φ) scans of the electrodeposited GZO and GZO/GO layer were better than those of the Ni-W base substrate. At 77 K and a self-magnetic field, the critical current density of PLD YBCO on the electrodeposited-based buffer layer was 3.3 × 10⁶ A/cm², using the field criterion of 1 μV/cm.     

Influence of fast-neutron irradiation on the intensity of the copper-related luminescence band at hν m =1.01 eV in n-type GaAs

The influence of neutron irradiation (the energy E=2 MeV and the dose Φ=10¹³–10¹⁵cm⁻²) and subsequent anneals (the annealing temperature T _a =400–700 °C and the annealing time is 30 min) of n-type GaAs(Te,Cu) crystals with an initial carrier concentration n ₀=2×10¹⁸ cm⁻³ on the intensity of the copper-related luminescence band with an emission maximum at hν _m =1.01 eV is studied. A significant irradiation-induced increase in the intensity of the band is observed. It is attributed to a radiation-stimulated increase in the concentration of emitting centers (Cu_Ga V _As pairs) as a result of the effective interaction of interstitial copper atoms with irradiation-induced gallium (V _Ga) and arsenic (V _As) vacancies, as well as V _Ga V _As divacancies. Fiz. Tekh. Poluprovodn. 31, 1171–1173 (October 1997)     

开放系统的无粒子数反转激光的时间演化分析

对开放的V型三能级系统,通过微分方程的数值运算,分析了该系统的无粒子数反转激光(laser without inversion, LWI)产生的机制,讨论了探测场和驱动场的失谐、驱动场的Rabi频率、粒子初始状态对系统LWI时间演化的影响.结果显示:驱动场耦合的两个能级上的粒子数分布以相同的频率振荡,位相差π;在探测场和驱动场皆共振(⊿=⊿<,o>=0)时,原子对探测场色散的响应为零,双光子相干项ρca是实量;驱动场的Rabi频率Ω增大时,增益、相干项和粒子数差的振荡周期减小;粒子数的初始状态主要影响增益、相干项和粒子数差的振荡幅度,并不影响最后的稳定状态.     

Growth of the (In2S3)x(FeIn2S4)1 ? x single crystals and properties of photoelectric structures on their basis

Complete mutual solubility in the (In₂S₃) _x (FeIn₂S₄)_{1 − x} system is established. The technology is developed, and single crystals of the continuous series of the (In₂S₃) _x (FeIn₂S₄)_{1 − x} solid solutions are grown for the first time. The linear dependence of the unit cell parameter of single crystals with a cubic spinel lattice on the solid solution composition is found. First, photosensitive Schottky barriers are fabricated, and then, based on studies of their photosensitivity, the character of band-to-band transition is discussed and the values of the band gap depending on the atomic composition are estimated. The possibility of using the obtained solid solutions as broadband photoconverters of optical radiation is revealed.     

Photovoltaic effect in the impurity absorption region of Si-structures with blocked impurity conductivity

A study is made of the field dependence of the photoconductivity in two-layer Si:Sb-and Si:Bstructures with blocked impurity-band conductivity and different thicknesses of the undoped (blocking) layer. The impurity concentration in the doped (active) layer was ≈10¹⁸ cm⁻³. Measurements were made at temperatures T=4–15 K for high (Φ∼10¹⁶ photons/cm² · s) and low (Φ<10¹⁴ photons/cm² · s) incident photon fluxes. A photovoltaic effect is observed in the Si:B structures with a thin (3 μm) blocking layer. It is found that a photovoltage develops for photons with energies exceeding the ionization energy of boron and its magnitude is independent of the photoexcitation intensity (for Φ>10¹³ photons/cm² · s) and, in the limit of low temperatures, it is close to the activation energy ɛ ₃ for jump conductivity in the active layer. The photovoltaic effect is explained by ballistic transit of the blocking layer by holes emitted from the contact which are then cooled in the active layer, as well as by the presence of a potential barrier ≈ɛ ₃ between the active and blocking layers. These factors are taken into account in a model for describing the major features of the dependence of the photovoltage on temperature and on the photon intensity and energy. Fiz. Tekh. Poluprovodn. 33, 456–463 (April 1999)     

Staebler-Wronski effect as a function of the Fermi level position and structure of nondoped, amorphous, hydrated silicon

The photoconductivity degradation rates γ (σ _ph∼t ^−γ ) of nondoped, amorphous, hydrated silicon films deposited at T _s =300–400 °C and subjected to illumination for 5 h at 300 K (light source 100 mW/cm², λ<0.9 μm) were investigated. It was shown that the degradation rate γ depends on the preillumination position of the Fermi level ɛ _c −ɛ _F and often is not directly related to the hydrogen content in the film. It was found that there are correlations between the value of γ and the bonds in the silicon-hydrogen subsystem [isolated SiH and SiH₂ complexes, clusters (SiH)_n, and chains (SiH₂)_n]. Fiz. Tekh. Poluprovodn. 32, 484–489 (April 1998)     

Increase in the Thermoelectric Efficiency of the Disordered Phase of Layered Antiferromagnetic CuCrS<Subscript>2</Subscript>

The thermoelectric figure of merit (ZT) of the layered antiferromagnetic compound CuCrS₂ is further improved with increase in the Cr-vacancy disorder on sintering above 900°C. X-ray photoelectron spectroscopy and x-ray diffraction refinement results for different samples show that the chromium atoms are transferred from the filled layers to the vacant sites between the layers. This atomic disorder increases the electrical conductivity (σ) due to self-doping of the charge carriers and reduces thermal conductivity (κ) due to increase in phonon scattering. The Seebeck coefficient (S) is p-type and remains nearly temperature independent with values between 150 μV/K and 450 μV/K due to electronic doping in different samples.     

The magnetic parameter connected with design of high quality ferrite microstrip phase shifter

It is shown that the state of magnetization of the substrate is one of the main factors affecting the properties of nonreciprocal latching ferrite microstrip phase shifter. Raising the residual magnetization of the substrate, increasing the ratioR(=4πM/4πM _s ) (4πM—the magnetization of the “latching state” of the device, 4πM _s —the saturation magnetization) are effective in reducing the insertion loss of the device, raising the effectiveness of phase shift, extending the band width, and reducing the drive power, etc. Different methods of magnetization are analysed and compared. Photographs indicating the structure and the external form of the device are given and the main performances of single-digit and multi-digit devices are also presented.     

Photoluminescence of nitro-substituted europium (III) phthalocyanines

Europium monophthalocyanine Eu(acac)Pc, europium monotetranitrophthalocyanine Eu(acac)Pc(NO₂)₄, and heteroleptic europium tetranitrobisphthalocyanine Eu(Pc)(Pc(NO₂)₄) are synthesized. The spectral characteristics of the phthalocyanine complexes in the visible and near-infrared regions are studied. The photoluminescence spectra are recorded. The luminescence bands are detected in the regions 450–500 nm (S₂ → S₀) and 670–730 nm (S₁ → S₀). The peaks are attributed to electronic transitions in the organic ligands.     

Structure and High-Temperature Thermoelectric Properties of the n-Type Layered Oxide Ca2?xBix?δMnO4?γ

We have investigated the effects of Bi doping on the crystal structure and high-temperature thermoelectric properties of the n-type layered oxide Ca₂MnO_4−γ . The electrical conductivity σ and the absolute value of the Seebeck coefficient S were, respectively, found to increase and decrease with Bi doping. The thermal conductivity κ of doped Ca₂MnO_4−γ is relatively low, 0.5 W/m K to 1.8 W/m K (27°C to 827°C). Consequently, the ZT value, ZT = σS ² T/κ, increases with Bi doping. The maximum ZT is 0.023 for Ca_1.6Bi_0.18MnO_4−γ at 877°C, which is ten times higher than that of the end member, Ca₂MnO_4−γ . The increase of ZT mainly results from the considerable increase of σ, which can be explained in terms of structural change. The␣Mn-O(1) and the Mn-O(2) distances in the c-direction and ab-plane, respectively, increase with increasing Bi concentration, indicating that the valence state of Mn ions decreases with the increase of electron carriers in the CaMnO₃ layers. In addition, the Mn-O(2)-Mn bond angle increases linearly with Bi doping, leading to an improvement of the electron carrier mobility.     

Anomalous Peak in the Forward-Bias <Emphasis Type="Italic">C</Emphasis>–<Emphasis Type="Italic">V</Emphasis> Plot and Temperature-Dependent Behavior of Au/PVA (Ni,Zn-doped)/<Emphasis Type="Italic">n</Emphasis>-Si(111) Structures

In this study, the temperature-dependent mean density of interface states (N_SS)(N_{\rm SS}) and series resistance (R_S)(R_{\rm S}) profiles of Au/PVA (Ni,Zn-doped)/n-Si(111) structures are determined using current–voltage (I−V) and admittance spectroscopy [capacitance–voltage (C–V) and conductance–voltage G/ω–V] methods. The other main electronic parameters such as zero-bias barrier height (F_B0)(\Phi_{{\rm B}0}), ideality factor (n), and doping concentration (N _D) are also obtained as a function of temperature. Experimental results show that the values of F_B0\Phi_{\rm{B}0}, n, R _S, and N _SS are strongly temperature dependent. The values of F_B0\Phi_{\rm{B}0} and R _S increase with increasing temperature, while those of n and N _SS decrease. The C–V plots of Au/PVA (Ni,Zn-doped)/n-Si(111) structures exhibit anomalous peaks in forward bias (depletion region) at each temperature, and peak positions shift towards negative bias with increasing temperature. The peak value of C has been found to be strongly dependent on N _SS, R _S, and temperature. The experimental data confirm that the values of N _SS, R _S, temperature, and the thickness and composition of the interfacial polymer layer are important factors that influence the main electrical parameters of the device.