expression for the momentum density, which is missing from Obukhov and Hehl's Eq. 74> medium is properly taken into consideration. This yields the term 4 (Px B)in our 5. Oblique incidence with s-polarized light To the best of our knowledge, the momentum of light at oblique incidence has not been discussed previously. This is an extremely important case, since it reveals the existence of a lateral radiation pressure at the edges of the beam within a dielectric medium; consistency with the results of Section 4 simply demands the existence of such lateral pressures. We analyze the case of s-polarization here, leaving a discussion of p-polarized light at oblique incidence for the next section. The two cases turn out to be fundamentally different, although both retain the expression for momentum density derived in the case of normal incidence Figure 3 shows the case of oblique incidence with s-polarized light at the interface between the free-space and a dielectric medium. Again, we assume that the dielectric constant E is complex, allowing it to approach a real number only after calculating the total force by ntegrating through the thickness of the medium. Inside the medium, the E- and H-field distributions are Er (x, =)=(1+r3)E exp[i2T(x sine +NvE-sin e nol (5a) Hx(x,=)=ve-sin0 Err(x, syZ HI: (x, =)=-sine Ety(x,=)Zo Here rs=(cose-Ve-sin 0)/(cos0+VE-sin'e)is the Fresnel reflection coefficient for s- light. Since there are no free charges inside the medium(nor on its surface), the only relevant force here is the magnetic Lorentz force on the dipolar current density Jy(x, = -ioEE-DErv(, =). Following the same procedure as before, we find the net force components along the x-and z-axes to be r X E1=(1+rs)E。 n+ik=ve medium of(complex)dielectric constant E The Fresnel reflection coefficient is denoted by rs #5025-S1500US Received 10 August 2004; revised 13 October 2004; accepted 20 October 2004 (C)2004OSA November 2004/Vol 12. No 22/OPTICS EXPRESS 5383medium is properly taken into consideration. This yields the term ¼(P × B) in our last expression for the momentum density, which is missing from Obukhov and Hehl’s Eq. (27). 5. Oblique incidence with s-polarized light To the best of our knowledge, the momentum of light at oblique incidence has not been discussed previously. This is an extremely important case, since it reveals the existence of a lateral radiation pressure at the edges of the beam within a dielectric medium; consistency with the results of Section 4 simply demands the existence of such lateral pressures. We analyze the case of s-polarization here, leaving a discussion of p-polarized light at oblique incidence for the next section. The two cases turn out to be fundamentally different, although both retain the expression for momentum density derived in the case of normal incidence. Figure 3 shows the case of oblique incidence with s-polarized light at the interface between the free-space and a dielectric medium. Again, we assume that the dielectric constant ε is complex, allowing it to approach a real number only after calculating the total force by integrating through the thickness of the medium. Inside the medium, the E- and H-field distributions are Et y (x, z) = (1 + rs)Eo exp[i2π(x sinθ + z√ε − sin2 θ )/λo] (5a) Ht x (x, z) = √ε − sin2 θ Et y (x, z)/Zo (5b) Ht z (x, z) = −sinθ Et y (x, z)/Zo (5c) Here rs = (cosθ − √ε – sin2 θ ) / (cosθ + √ε – sin2 θ ) is the Fresnel reflection coefficient for s￾light. Since there are no free charges inside the medium (nor on its surface), the only relevant force here is the magnetic Lorentz force on the dipolar current density Jy(x, z) = −iω εo(ε − 1)Et y (x, z). Following the same procedure as before, we find the net force components along the x- and z-axes to be Fig. 3. Obliquely incident s-polarized plane wave arrives at the surface of a semi-infinite medium of (complex) dielectric constant ε. The Fresnel reflection coefficient is denoted by rs. Ho Eo θ θ′ Ht X Z rs Eo rsHo Et = (1 + rs)Eo n + iκ = √ε (C) 2004 OSA 1 November 2004 / Vol. 12, No. 22 / OPTICS EXPRESS 5383 #5025- $15.00 US Received 10 August 2004; revised 13 October 2004; accepted 20 October 2004