A method for irradiating scattering medium, including modifying a particle's response to electromagnetic radiation irradiating the particle in a scattering medium, wherein the electromagnetic radiation is scattered by the scattering medium, and modulated by the modifying, into scattered electromagnetic radiation comprising a scattered field; forming a phase conjugate field, wherein the phase conjugate field is a phase conjugate of the scattered field; and irradiating the scattering medium with the phase conjugate field, wherein the phase conjugate field forms a focus at a target defined by the particle.