We present a novel laser nano-lithography method inside the bulk of silicon. We exploit nanosecond laser pulses of 1.55-μm wavelength which are modulated with a spatial light modulator. The created Bessel beams enable direct and highly-controlled subsurface fabrication capability in Si. Using this technique, we demonstrate for the first time, the fabrication of sub-wavelength nano-modifications deep inside Si. We further illustrate nanopatterns of 200-nm width and of sub-micron separation. Such 3D control on sub-wavelength structures inside Si offer exciting possibilities for Si-photonics devices, meta-material and meta-surface in-chip technologies. © 2023, META Conference. All rights reserved.