Embedded anisotropic microreflectors by femtosecond-laser nanomachining

Directly written embedded structures created within fused silica by a femtosecond Ti:sapphire laser are observed to strongly reflect blue light. Reflection emerges only in a direction parallel to the polarization axis of the writing laser. This anisotropic-effect is caused by a periodic modulation of refractive index of amplitude Δn∼10−2 with a characteristic period Λ∼150 nm over a spot size ∼1.5 μm. We show that the origin of the anisotropic reflection is the primary cause of other anisotropic phenomena reported in recent experiments.