Discussions Of Electromagnetic Energy And Their Possible Applications

The law of conversion,transmission and conservation of energy in electromagnetic wave is a fundamental issue in electromagnetic field theory.In this paper,the following five aspects of his work are carried out around the conversion and transmission of electromagnetic energy in lossy media.First,there exist several unequivalent expressions of stored and dissipated energy densities.It is still lack of correctness judgement for these expressions.Here,he proposes that the time-averaged form of Poynting's theorem,which implies that the net power flowing into a closed surface equals the power dissipated in the enclosed volume,can be taken as a correctness criterion for expression of dissipated energy density.On this basis,he reviews the common expressions of stored and dissipated energy densities and provides possibility to derive equivalent expressions by using different ways.Then,he discusses a possible experiment to examine the correctness of expression of electromagnetic dissipated energy density: When a plane wave normally incident to a slab,the energy absorbed by the slab can be uniquely determined by the reflection coefficient and the transmission coefficient.On the other hand,the energy absorbed by the slab can also be calculated by using the dissipated energy density expressions of forward and backward waves in the slab.By comparing the absorbed energy of this two ways,he can judge the correctness of expression of electromagnetic dissipated energy density.Furthermore,he demonstrates that usual expression of time-averaged stored energy density(TASED)for disperisve medium is invalid,which is mainly attributed to the fact that there exist mathematical errors in derivation of this expression.Noting connection between TASED and time-averaged Poynting vector(TAPV)and the case that TAPV of a pulse is the sum of TAPVs of its components,similarly,it is verified that TASED of a pulse in disperisve medium can be taken as the sum of TASEDs of all its components.Based on the above research and related theories,he demonstrates that TASED of a circularly polarized wave is equal to zero,in addition,TASEDs of both circularly and linearly polarized waves do not directly relate to their TAPV,respectively,which indicate that the usual definition of energy flow velocity needs to be reconsidered.Noting that energy of electromagnetic wave(photon)obtained from relativistic energy-momentum relation corresponds to transport of electromagnetic energy,combining expressions of both TAPV and time-averaged electromagnetic wave momentum density,a new definition of energy flow velocity is proposed by applying energyinstead of TASED.Also,he shows from the new definition that a rational energy flow velocity of electromagnetic wave traveling in a material medium is obtained by adopting Minkowski electromagnetic wave momentum density,which provides a new way to further discuss the long-standing Abraham-Minkowski controversy.Last,he demonstrates theoretically that steady bound electromagnetic eigenstate can arise in an infinite homogeneous isotropic linear metamaterial with zero-real-part-of-impedance and nonzero-imaginary-part-of-wave-vector,which is partly attributed to that,here,nonzero-imaginary-part-of-wave-vector is not involved with energy losses or gain.Altering value of real-part-of-impedance of the metamaterial,the bound electromagnetic eigenstate may become to be a progressive wave.His work can be useful to further understand energy conversion and conservation properties of electromagnetic wave in the dispersive and absorptive medium and provides a feasible route to stop,store and release electromagnetic wave(light)conveniently by using metamaterial with near-zero-real-part-of-impedance.