Thermal stimulated radiation of a dissipative Fabry-Perot etalon

The contribution of stimulated coherent radiation to the total thermal radiation of a dissipative Fabry-Perot etalon is calculated and it is shown that for sufficiently high temperatures and a sufficiently highQ of the resonator the radiation of the Fabry-Perot etalon can be predominantly a stimulated one. On the basis of thermodynamic investigation, it has been found that for the conversion efficiency of thermal energy into the energy of stimulated radiation of a two-level system , whereT _eff is a parameter characterizing the total emissivity of the system at a given frequency and¯f is the mean value of the distribution function of the photons in a given spectrum interval.The author wishes to express his gratitude to Dr. M. Trlifaj and Dr. K. Pátek for stimulating discussions.     

Nonstationary source of resonance radiation at the surface of a stimulated dispersed medium

Upon the sudden connection of a radiation source a reflected wave has two fronts corresponding to scattering by excited and nonexcited atoms of the medium. The former turns out to be leading. It is shaped by collapse of a fur coat of virtual photons, because of the vacuum effect, surrounding the excited atoms.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 33–38, October, 1988.     

Phase of radiation from stimulated emission

With the help of the quantum theory of radiation, it is shown that the stimulated radiation from an atom has the same direction and phase dependence as the incident stimulating radiation.     

Two-quantum stimulated emission of gamma radiation

Various schemes exploiting two-quantum nuclear transitions for the generation of coherent gamma radiation (stimulated anti-Stokes and stimulated two-quantum de-excitation of isomeric nuclei in an active medium with the hidden population inversion of nuclear states and the ignition of an avalanche-like stimulated gamma-emission by counterpropagating X-rays) are discussed.     

Current density in radiation stimulated superconductors

Eliashberg's theory of stimulated superconductivity is reviewed and discussed within the BCS-Mattis formalism for impure superconductors. Stimulation by microwaves as well as by acoustical fields is considered. Eliashberg's results are completed by obtaining the nonequilibrium current response to an applied transverse vector potential. The resulting expression may be used to obtain the critical current of small specimens.     

Observation of infra-red radiation from stimulated polaritons

Polaritons associated with the 1072 cm^–1 optical mode of quartz have been stimulated by a two-beam method and we have directly observed the far-infrared radiation corresponding to the electromagnetic part of the excitation with a HgTe-CdTe detector.     

Decay of isomers stimulated by laser radiation

A theory is presented for the induced decay of isomer levels for nuclei exposed to a laser field, which couples the initial isomer level to intermediate higher lying levels with short lifetimes. We took into account the electric dipole transitions between these levels in a one-photon approximation. The time-dependent Schrödinger equation with a periodic Hamiltonian is solved by the method of the composite Hilbert space. A simple expression for the broadening of the isomer level ΔΓ, caused by the laser radiation, is derived. As an example, we considered the decay of the isomer level 970.17 keV with the spin I ^π = 23/2^? of ¹⁷⁷Lu, coupled by the laser wave to the virtual level 1352.33 keV with I ^π = 21/2⁺. The ratio of the broadening ΔΓ to the natural width of the isomer level Γ is found to be about 40% for a 10¹⁷ W/cm² laser. Any influence of the electronic environment is not taken into account.     

Vacuum ultraviolet radiation source

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 54, No. 3, pp. 509–512, March, 1991.     

Water-vapor-based source of UV radiation

The results of studying a capacitive discharge in water vapor are reported. This discharge is an effective and environmentally friendly source of UV radiation due to hydroxyl OH (A ²Σ⁺ → X ²Π transition) in the wavelength range 280–330 nm. It is shown that, at E/N < 210 Td, the discharge is greatly influenced by dissociative attachment of electrons, while at E/N > 210 Td, ionization dominates over dissociation. The formation rate of excited OH* radicals (A ²Σ⁺) in the water-vapor discharge is much higher than the formation rate of emitting states in hydrogen and oxygen atoms. As E/N grows, the ratio between the intensities of OH lines and atomic hydrogen Balmer series decreases. According to estimates, E/N values optimal for the OH radical line excitation fall into the range 250–400 Td.     

Thermal distortion in glass producing stimulated emission

A Mach-Zender interferometer has been used with neodymium glass in various stages of pumping by a flash tube; the pumping produces the effect of a positive lens for air cooling but of a negative one for water cooling.     

受激辐射压力的光子再分配模型

本文报道了在两束不同频率、不同传播方向的光束作用于二能级原子的受激辐射压力的数值结果。给出了一个新的模型——光子再分配模型——来解释受激辐射压力。     

Thermal emission stimulated by excitation of metastable states

Waves interference inside thin films creates fine structures in the thermal emission spectrum of film when the magnitude of film thickness is of the same order than the coherence length of light. Here, we present an alternative to the theory of partially coherent light to explain these ripples pattern and easily predict the radiative properties of films in intermediate regime. The starting point of this theory is based on the observation that unlike vacuum, matter supports the presence of unstable electromagnetic waves with a finite lifetime. For thin absorbing films, we demonstrate that many of these metastable states are quantified and can be excited by an external radiation field. A direct connection is then established between the peaks of emission and these modes. These results open new prospects for the theoretical study and modelling of radiative exchanges inside and between microscale media.     

Thermal radiation from nanoparticles

A simple and universal criterion of the efficiency of energy loss by thermal radiation is obtained for the class of small conducting particles, including, in addition to metals and graphite, the majority of carbides of metals important for practical applications, such as tungsten and titanium carbides.     

On the interaction of stimulated spin-flip raman scattering and stimulated recombination radiation in InSb

We have studied the interaction of stimulated spin-flip Raman scattering and stimulated recombination radiation in n-InSb using a CW CO pump laser. A change in linewidth and output power of second Stokes spin-flip radiation is observed when the tuning curve of the first Stokes stimulated spin-flip radiation and the stimulated recombination radiation cross. The observations are explained using a simple rate equation model.     

All-fiber femtosecond Cherenkov radiation source

An all-fiber femtosecond source of spectrally isolated Cherenkov radiation is reported, to the best of our knowledge, for the first time. Using a monolithic, self-starting femtosecond Yb-doped fiber laser as the pump source and the combination of photonic crystal fibers as the wave-conversion medium, we demonstrate milliwatt-level, stable, and tunable Cherenkov radiation at visible wavelengths 580-630 nm, with pulse duration of sub-160-fs, and the 3 dB spectral bandwidth not exceeding 36 nm. Such an all-fiber Cherenkov radiation source is promising for practical applications in biophotonics such as bioimaging and microscopy.     

A hydrodynamic X-ray radiation source

The results of experimental investigation of a flow of a weakly conductive liquid in a coaxial channel with insulating walls are presented. The possibility of forming all the necessary conditions to generate X-ray radiation when liquid moves in the channel is shown. The questions of the electrization, the charge accumulation, and its discharge are considered. It is shown that the charge intensely accumulates during liquid cavitation in small holes on the channel wall. The appearance of stable luminous cavitation threads moving in the flow is revealed in the initial segment of the channel, and their role in the discharge of the cavitation regions is determined.     

新型准光学可调辐射源研究

 本文介绍一种新型毫米波准光学可调辐射源,它采用由面对称三反射镜准光学谐振腔和绕射光栅组成高频互作用系统,利用中等能量级的相对论带状电子注激励,产生频率可调的宽带毫米波、远红外波段的辐射。这种新方案的机理性实验在电子科技大学首次获得成功,其主要实验参数：电子注的能量为400~500kV,电压脉冲宽度70ns,同步脉冲磁场强度1.2T; 磁场脉冲宽度10ms,带状电子注尺寸10nm×1mm;通过热测实验,我们成功地检测到3mm波段的高频信号,其峰值功率达到数十千瓦量级。