• Present invention describes a method & apparatus for modifying dimensions of a waveguide.
• The method comprising a few steps illustrated hereinbelow:

STEP 1

• Positioning a shadow mask with an aperture above the waveguide fabricated on a substrate.

STEP 2

• Spatially filtering a substance, by the apparatus through the aperture of the shadow mask on a portion of the waveguide, wherein the substance is a vaporizing material deposited with the portion of the waveguide to modify a cladding of the waveguide; and

STEP 3 

• Obtaining an adiabatic spot size converter at end of the waveguide, by adjusting a distance between the shadow mask and the portion of the waveguide, to modify the dimensions of the waveguide. (Refer Fig.1)

• Further the apparatus for modifying dimensions of a waveguide is illustrated herein. (Refer Fig. 2A-2F)
• The apparatus comprises one of a reactive ion etching system & a deposition system.
• Further, said apparatus includes a shadow mask which is with an aperture positioned above the waveguide, configured to spatially filter a substance through the aperture in the shadow mask on a portion of the waveguide.
• Furthermore, an adiabatic spot size converter is obtained at end of the waveguide.