(b) Write out the equations for the time dependence of ρ11, ρ22, ρ12 and ρ21 assuming that a light field interaction V = -μ12Ee iωt + c.c. couples only levels |1> and |2>, and that the excited levels exhibit spontaneous decay. (8 marks) (c) Under steady-state conditions, find the ratio of populations in states |2> and |3>. (3 marks) (d) Find the slowly varying amplitude ̃ ρ 12 of the polarization ρ12 = ̃ ρ 12e iωt . (6 marks) (e) In the limiting case that no decay is possible from intermediate level |3>, what is the ground state population ρ11(∞)? (2 marks) 2. (15 marks total) In a 2-level atom system subjected to a strong field, dressed states are created in the form |D1(n)> = sin θ |1,n> + cos θ |2,n-1> |D2(n)> = cos θ |1,n> sin θ |2,n-1>

The Quantum Theory of Light

Plasma–liquid interactions represent a growing interdisciplinary area of research involving plasma science, fluid dynamics, heat and mass transfer, photolysis, multiphase chemistry and aerosol science. This review provides an assessment of the state-of-the-art of this multidisciplinary area and identifies the key research challenges. The developments in diagnostics, modeling and further extensions of cross section and reaction rate databases that are necessary to address these challenges are discussed. The review focusses on non-equilibrium plasmas.

/pdf/plasma-liquid-interactions-a-review-and-roadmap-4kfoerpjnh.pdf

Plasma-liquid interactions: A review and roadmap

Cyclostationarity: half a century of research

Journal of Applied physics,Vol.33 : 1962年に発表されたレオロジー関連の論文

There can be little doubt that the Monte Carlo method for semiconductor device simulation has enormous power as a research tool. It represents a detailed physical model of the semiconductor material(s), and provides a high degree of insight into the microscopic transport processes. However, if the authority ascribed to Monte Carlo models of devices at 1/spl mu/m feature size is to be maintained for devices below O.1/spl mu/m, modelling of the fundamental physics must be further improved. And if the Monte Carlo method is to be successful as a semiconductor device design tool, the device model must be made more realistic. Success in the industrial sector depends on this, but also on achieving fast run-times optimisation - where the scope and need for ingenuity is now greatest.

The Monte Carlo method for semiconductor device simulation

We report on systematic measurements of resonant plasma waves oscillations in several gate-length InGaAs high electron mobility transistors (HEMTs) and compare them with numerical results from a specially developed model. A great concern of experiments has been to ensure that HEMTs were not subject to any spurious electronic oscillation that may interfere with the desired plasma-wave spectroscopy excited via a terahertz optical beating. The influence of geometrical HEMTs parameters as well as biasing conditions is then explored extensively owing to many different devices. Plasma resonances up to the terahertz are observed. A numerical approach, based on hydrodynamic equations coupled to a pseudo-two-dimensional Poisson solver, has been developed and is shown to render accurately from experiments. Using a combination of experimental results and numerical simulations all at once, a comprehensive spectroscopy of plasma waves in HEMTs is provided with a deep insight into the physical processes that are involved.

Terahertz spectroscopy of plasma waves in high electron mobility transistors

We present a survey on the theoretical modelling of the small-signal response and noise associated with velocity fluctuations in semiconductor high-field transport. Because of the high values of the applied electric field, current - voltage characteristics and electrical noise are found to deviate strongly from Ohm's law and Nyquist's relation respectively. Accordingly, in the case of homogeneous (bulk) structures the field and frequency dependence of the differential mobility, diffusivity and electronic noise temperature are investigated within a rigorous microscopic approach which solves exactly the appropriate kinetic equations through analytical and Monte Carlo techniques. Spectral functions in the frequency domain are obtained from their correspondent response and correlation functions in the time domain. The subject is also analysed within a balance-equation approach which enables us to obtain simple analytical expressions which can provide a direct microscopic interpretation and can be applied to device modelling. For validation purposes calculations are applied to the relevant case of holes in Si and electrons in GaAs. In the latter material the presence of negative differential conductivity (Gunn effect) leads to interesting behaviour of the small-signal response and noise spectra which are also investigated for the simplest prototype of non-homogeneous structures, that is the diode. The comparison between the different approaches so developed and between calculations and experiments is found to be quite good, thus providing a quantitative microscopic interpretation of the main features associated with small-signal response and fluctuations in semiconductors under high-field conditions.

https://iopscience.iop.org/article/10.1088/0268-1242/12/2/001/pdf

Modelling of small-signal response and electronic noise in semiconductor high-field transport

Transfer-field methods for electronic noise in submicron semiconductor structures

A closed hydrodynamic model and the associated numerical procedures are developed for simulating hot‐carrier transport in submicron semiconductor devices. To check the validity of the model, the steady‐state characteristics of near‐micron n+nn+ InP diodes are compared with a standard Monte Carlo approach. The excellent agreement found fully validates the physical reliability of our model which has been further developed to investigate linear and nonlinear time‐dependent characteristics. The contribution of each part of the device, when operating as microwave power‐generation, is analyzed through the spatial profiles of the impedance‐field spectrum. The usual subdivision of the n‐region into a passive (dead‐zone) and active zone is carried out. The dead zone is found to manifest itself as a purely real resistance which is practically independent of the frequency. One or more spatial zones which are responsible for the generation are shown to be formed in the active region of the diode. By reducing the leng...

Linear and nonlinear analysis of microwave power generation in submicrometer n+nn+ InP diodes

We present a hydrodynamic model to simulate the excitation by optical beating of plasma waves in nanometric field effect transistors. The biasing conditions are whatever possible from Ohmic to saturation conditions. The model provides a direct calculation of the time-dependent voltage response of the transistors, which can be separated into an average and a harmonic component. These quantities are interpreted by generalizing the concepts of plasma transit time and wave increment to the case of nonuniform channels. The possibilities to tune and to optimize the plasma resonance at room temperature by varying the drain voltage are demonstrated.

Pavel Shiktorov

Papers

Terahertz spectroscopy of plasma waves in high electron mobility transistors

Modelling of small-signal response and electronic noise in semiconductor high-field transport

Transfer-field methods for electronic noise in submicron semiconductor structures

Linear and nonlinear analysis of microwave power generation in submicrometer n+nn+ InP diodes

Hydrodynamic modeling of optically excited terahertz plasma oscillations in nanometric field effect transistors