共查询到20条相似文献,搜索用时 31 毫秒
1.
Properties of atom-like emitters in cavities are successfully described by cavity quantum electrodynamics(cavity-QED).In this work,we focus on the issue of the steady-state and spectral properties of the light emitted by a driven microcavity containing a quantum well (QW) with the excitonic interactions using simulation of fully quantum-mechanical treatment.The system is coherently pumped with laser,and it is found that depending on the relative values of pumping rate of stimulated emission,either one or two peaks close to the excitation energy of the QW or to the natural frequency of the cavity are shown in the emission spectrum.Furthermore,the nonclassical proprieties of the emitted photon have been investigated.This excitonic system presents several dynamical and statistical similarities to the atomic system,in particular for the bad-cavity and good-cavity limits.The results show that the photon emission can be significantly amplified due to the coupling strength between a single emitter and radiation field in the microcavity,and it is concluded that the present semiconductor microcavity system may serve as a QW laser with low threshold. 相似文献
2.
Zhixian X. Jiu Duluo L. Zuo Liang Miao Zuhai H. Cheng Chunchao C. Qi 《Journal of Infrared, Millimeter and Terahertz Waves》2010,31(8):885-891
A simple terahertz (THz) cavity and a TEA CO2 laser for the optically pumped THz emission is studied experimentally. To obtain high peak power of pump laser, pressure
ratios of gas mixture in the cavity of the TEA CO2 laser are discussed. When CH3OH are pumped by the 9P(16) and 9P(36) CO2 laser lines, the generation of terahertz radiation with energy as high as 353 μJ and 307 μJ are obtained, respectively. The
corresponding photon conversion efficiencies are 0.705% and 0.29%. Meanwhile, higher peak power of pump laser effectively
improves the photon conversion efficiency. And the optimum THz laser pressure increases with narrower pulse width of pump
laser. 相似文献
3.
Upconversion lasing in Er:YAlO3 is reported. Laser emission was produced using both sequential two-step pumping and cross-relaxation energy transfer. In addition, photon avalanche upconversion pumping was demonstrated. Selection among these pumping mechanisms is determined by the pump wavelength, and laser operation was obtained with excitation between 785 nm and 840 nm. The highest laser output power was achieved at 34°K, where 918 mW of pump power at 807 nm produced 121 mW of TEM00 emission. The optical conversion efficiency was 13%. Repetitively Q-switched operation is reported, and the temporal- and temperature-dependence of the laser output is discussed 相似文献
4.
Pingyuan Liang Meng Meng Jiangchu Liang Xizhang Luo 《Journal of Infrared, Millimeter and Terahertz Waves》2012,33(10):1018-1028
Based on the theory of semi-classical density matrix and a model of double three-energy-level (DTEL) system for laser line competition in optically pumped D2O super-radiant terahertz laser (THz Laser), the mathematical expressions of gain coefficients for pumping signal and THz laser signal are deduced, and the competition between 66?μm and 116?μm laser lines is calculated numerically by means of iteration method. The effects of the operation conditions (including pump power, working gas pressure and the length of cavity) on the competition are analyzed. It is found that 66?μm emission dominated the competition; with the increase of working gas pressure (or the cavity length), the spectrum of 66?μm emission experiences changes from discrete double-peak structure to overlapped double-peak structure and finally to a wide-band structure, and the optimum gas pressure varied conversely with the optimum length of the THZ laser cavity. 相似文献
5.
Taiichi Otsuji Stephane Boubanga-Tombet Akira Satou Maki Suemitsu Victor Ryzhii 《Journal of Infrared, Millimeter and Terahertz Waves》2012,33(8):825-838
This paper reviews recent advances in spectroscopic study on ultrafast carrier dynamics and terahertz (THz) stimulated emission in optically pumped graphene. The gapless and linear energy spectra of electrons and holes in graphene can lead to nontrivial features such as negative dynamic conductivity in the THz spectral range, which may lead to the development of new types of THz lasers. First, the non-equilibrium carrier relaxation/recombination dynamics is formulated to show how photoexcited carriers equilibrate their energy and temperature via carrier-carrier and carrier-phonon scatterings and in what photon energies and in what time duration the dynamic conductivity can take negative values as functions of temperature, pumping photon energy/intensity, and carrier relaxation rates. Second, we conduct time-domain spectroscopic studies using an optical pump and a terahertz probe with an optical probe technique at room temperature and show that graphene sheets amplify an incoming terahertz field. Two different types of samples are prepared for the measurement; one is an exfoliated monolayer graphene on SiO2/Si substrate and the other is a heteroepitaxially grown non-Bernal stacked multilayer graphene on a 3C-SiC/Si epi-wafer. 相似文献
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7.
This paper describes a model and provides the mathematical formulation for describing the spike pulsing phenomenon observed in optically pumped three-level lasers. The model is based on the pumping of electrons from a ground state to an excited pump band from which they relax very rapidly to the excited laser level. With population inversion then achieved, laser action starts and repetitive pulses with decreasing amplitude are generated; the pulses then damp out and the laser output reaches a steady state as long as sufficient pump radiation energy is available. The equations describing the system in terms of the population inversion and photon density are nonlinear. However, approximations are made which permit the required relations between the transition rates to be established for such action to progress. The time variation of the population inversion and the photon density at the laser frequency are obtained for both the pumping time interval and the stimulated emission laser region. 相似文献
8.
AM and FM quantum noise properties of semiconductor lasers have been studied theoretically. Theoretical formulations for the AM noise spectrum, photon number probability density, FM noise spectrum, instantaneous frequency probability density, and power spectrum are presented here as functions of semiconductor laser material, structural, and pumping parameters. Two theoretical approaches are employed: one is based on the quantum mechanical Langevin equation, and the other on the density matrix equation. Starting from the quantum mechanical Langevin equation, three different formulations, that is, the rate equation, Fokker-Planck equation, and van der Pol equation, are derived. The parameters which represent stimulated emission, spontaneous emission, and refractive-index dispersion are obtained by using the Kane function interpolated to Halperin-Lax bandtail and the Stern's improved matrix element. The above four different theoretical formulations are related to each other, and the applicability for each method is discussed. 相似文献
9.
The generation of broadly tunable FIR laser emission by pumping Raman transitions in NH3 with 300 mJ, 50 ns duration pulses from a continuously tunable CO2 laser is reported. FIR laser outputs up to 4 mJ and a photon conversion efficiency as high as 16 percent have been obtained. 相似文献
10.
研究了周期量级的圆偏振激光在空气中成丝产生太赫兹辐射的偏振特性。将中心波长1.8 m、脉宽8.6 fs 的圆偏振红外激光脉冲聚焦到空气中,形成等离子体细丝,产生太赫兹辐射。通过测量太赫兹辐射的偏振状态,和偏振方向与驱动激光载波-包络相位的关系,发展太赫兹波偏振控制的方法。实验结果表明,太赫兹辐射为椭圆偏振,而且偏振平面随着驱动激光载波-包络相位的变化而转动。这对太赫兹波的偏振控制有重要意义,并为周期量级激光载波-包络相位的测量提供了新方法。 相似文献
11.
Ingrid Wilke Yujie J. Ding Tatiana V. Shubina 《Journal of Infrared, Millimeter and Terahertz Waves》2012,33(6):559-592
Indium nitride is a novel narrow band gap semiconductor. The material is a potential strong source of terahertz frequency
electromagnetic radiation with applications in time-domain terahertz spectroscopy and imaging systems. This article reviews
recent experimental research on terahertz emission from the binary compound semiconductor indium nitride excited by near-infrared
laser beams or microseconds electrical pulses. Advantages of indium nitride as terahertz radiation source material are discussed.
It is demonstrated that different mechanisms contribute to the emission of terahertz radiation from indium nitride. The emission
of up to 2.4 μW of THz radiation power is observed when InN is excited with near-infrared femtosecond laser pulses at an average
power of 1 W. 相似文献
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13.
V. L. Malevich 《Semiconductors》2006,40(2):155-160
The Monte Carlo simulation is used to calculate the Dember photovoltage and study the generation of terahertz electromagnetic pulses excited in indium arsenide by femtosecond laser radiation. The dynamics of the electric field and the charge-carrier transport are treated self-consistently. It is shown that the excitation of a semiconductor by laser pulses with the photon energy of ?ω?1.5 eV, the photovoltage attains its maximum within 50–100 fs after excitation and then falls off, oscillating with the plasma frequency. The photovoltage peak can be as much as tens times higher than the typical Dember photovoltages induced by steady-state illumination. On excitation of the semiconductor by radiation with shorter wavelengths (?ω?1.6 eV), the photoelectrons are scattered to the L and X valleys side; as a result, the photovoltage and the efficiency of the generation of the terahertz emission decrease. 相似文献
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15.
石墨烯特殊的零带隙能带结构和载流子弛豫特性,在研究太赫兹辐射源相干放大领域引起广泛关注。考虑带内和带间跃迁对电导率的贡献,研究了光抽运单层和多层石墨烯中非平衡二维电子-空穴系统的动态电导率特性。结果表明,在足够强的光抽运下,石墨烯中的粒子数反转能够使得动态电导率的实部在太赫兹频段内出现负值,这使基于石墨烯的太赫兹放大或受激辐射源成为可能。同时,通过研究动量弛豫时间、温度、层数、光强对石墨烯的负动态电导率的影响表明,石墨烯多层结构的动态电导率最小值的绝对值更大,作为太赫兹激光器的激活介质更具优势。 相似文献
16.
You-Jian Song Ming-Lie Hu Chang-Lei Wang Zhen Tian Qi-Rong Xing Lu Chai Ching-Yue Wang 《Photonics Technology Letters, IEEE》2008,20(13):1088-1090
A high pulse energy passively mode-locking fiber laser operating in the soliton-like regime is demonstrated. The laser is based on a linear cavity design. A segment of Yb-doped single-polarization large-mode-area photonic crystal fiber serves as the gain medium, and the self-starting mode-locking is achieved by a high contrast semiconductor saturable absorber mirror. The laser directly generates 600-fs pulses with 900 mW of average power at a repetition rate of 47.3 MHz, corresponding to a single pulse energy of 19 nJ. Furthermore, this fiber laser is directly used for pumping ZnTe to generate broadband terahertz radiation, resulting in a compact terahertz source. 相似文献
17.
The results of an investigation of photon avalanche upconversion pumping in Er3+:TiAlO3 are reported. Five pump wavelengths corresponding to transitions from the metastable 4I13/2 state to the 2H11/2 state generated upconversion laser emission at 549.8 nm. The dependence of the laser output power on pump power near laser threshold is discussed in terms of a four-level kinetics model and is shown to reflect the threshold power requirement for photon avalanche. The maximum output power at 7 K was 33 mW, giving an optical conversion efficiency of 3.5% and a conversion efficiency of 28% based on absorbed power. Pumping Er:YALO by cross relaxation energy transfer produced 166 mW of laser output with an optical conversion efficiency of 17% 相似文献
18.
增益随机散射介质中的非相干辐射 总被引:1,自引:2,他引:1
用蒙特卡罗方法仿真了增益随机散射体中的非相干辐射,观察了非相干随机激光的特性。当抽运能量超过一定阈值时,散射体的整体辐射谱突然变窄;随着抽运能量继续增大,在光滑谱背景上会出现分离尖峰;散射体内空间某位置处频率组成不是单一的;辐射谱中某单个频率的空间方向分布和位置分布比较广。增益随机散射体中产生的非相干随机激光本质上既不同于无反馈的普通放大自发辐射,又不同于相干反馈形成的常规激光。解释了非相干随机激光辐射谱上出现分离尖峰的原因,出现这种现象是由于少数光子在增益散射体中经历较多次数散射后得到了相对充分的放大。 相似文献
19.
Incoherent radiation of amplifying random media was investigated using Monte Carlo simulation and the characteristics of random laser were observed The entire emission spectra of the random media would become narrow abruptly when pumping energies exceeded certain threshold values, and as the pumping energies further increased, distinct sharp peaks would emerge on the spectrum background. The intensity of a certain spatial point within the scattering media was contributed from emissions of many frequencies. The intensity of a single frequency of the entire spectrum was contributed with emissions from wide spatial location and angle ranges. It has been pointed out that the incoherent radiation of amplifying random media is essentially different from amplified spontaneous emission without any feedback as well as conventional resonant-feedback laser. The explanation on distinct sharp peaks is that rare photons have experienced rather more scattering events and walked longer paths in amplifying random media, which accumulates more gain for these photons. 相似文献
20.
本文采用朗之万量子理论和激光场的准线性表示计算相干泵浦双光子激光的光子数起伏。结果表明,具有双光子损耗机制且在近阈运行时,双光子激光不存在光子数压缩态。 相似文献