The invention provides a non-invasive skin treatment device (200) comprising: a light source (10) constructed for emitting treatment light (15), an optical system (20) constructed for focusing the treatment light along an optical axis (OA) to a focus position (320) inside the skin tissue (300), and an indenter (30) comprising a skin contact surface (34) having an aperture (A1) at a distance from the optical system for allowing the treatment light to be focused through the aperture into the skin tissue. The indenter is configured and constructed for generating, in a cross-section of the aperture taken along the optical axis and along a cross-section direction wherein the aperture has a width dimension, a maximally curved protrusion of skin tissue freely protruding through the aperture towards the optical system by pressing the indenter against the skin surface of a specific skin type with a pressure exceeding a predefined pressure, a skin surface of said maximally curved protrusion having a radius of curvature (RC) at an intersection with the optical axis. The optical system is configured and constructed for generating a focused beam of the treatment light having, in said cross-section of the aperture at said intersection, a wave front with a radius of curvature ranging between 75% and 125% of said radius of curvature (RC) of the skin surface of said maximally curved protrusion.
