lowing relationship: Substituting (6) and (7) into (4) and (5), the average of each term in the stress tensor could be represented by Here, E ( k 0 , r , s$_{i}$ ) and H ( k 0 , r , s$_{i}$ ) are the electric/magnetic field at location r in the geometry under the excitation of source s$_{i}$ . Their corresponding relationships are summarized in Table I. If the object is made of perfect conducting material, there is only induced electric current J flowing on the surface. The scattered electric field and magnetic field in the free space region could be obtained from the induced electric current by L and K operators respectively 5 E$_{α}$ ( r ) = iω ∫$_{S}$ d r $^{′}$G$_{αβ}$ ( k, r , r $^{′}$) J$_{β}$ ( r $^{′}$) (6) H$_{u}$ ( r ) = 1 µ 0 ∫$_{S}$ d r ′ [ ∂ ∂v G$_{nβ}$ ( k, r , r $^{′}$) − ∂ ∂n G$_{vβ}$ ( k, r , r $^{′}$) ] J$_{β}$ ( r $^{′}$) (7) 1 2 ϵ 0 〈 E$_{n}$ ( r ) E$_{n}$ ( r $^{′}$) 〉 = ℏ c 0 2 πµ 0 Im ∫ ∞ 0 k 2 0 iω E$_{n}$ ( k 0 , r , s 1 ) dk 0 (8) 1 2 µ 0 〈 B$_{u}$ ( r ) B$_{u}$ ( r $^{′}$) 〉 = ℏ c 0 2 π Im ∫ ∞ 0 dk 0 [ − H$_{u}$ ( k 0 , r , s 2 ) + H$_{u}$ ( k 0 , r , s 3 )] (9) 1 2 µ 0 〈 B$_{v}$ ( r ) B$_{v}$ ( r $^{′}$) 〉 = ℏ c 0 2 π Im ∫ ∞ 0 dk 0 [ − H$_{v}$ ( k 0 , r , s 4 ) + H$_{u}$ ( k 0 , r , s 5 )] (10) Field Component Source ( r$_{i}$ = r ) (1) E$_{n}$ ( r , s 1 ) ˆ nδ ( r ′ − r$_{i}$ ) (2) H$_{u}$ ( r , s 2 ) ˆ v ∂ ∂n $_{′}$δ ( r ′ − r$_{i}$ ) (3) H$_{u}$ ( r , s 3 ) ˆ n ∂ ∂v $_{′}$δ ( r ′ − r$_{i}$ ) (4) H$_{v}$ ( r , s 4 ) ˆ n ∂ ∂u $_{′}$δ ( r ′ − r$_{i}$ ) (5) H$_{v}$ ( r , s 5 ) ˆ u ∂ ∂n $_{′}$δ ( r ′ − r$_{i}$ ) TABLE I: A table of source and field operators for each term in the stress tensor.