We report an invisibility carpet cloak device, which is capable of making anobject undetectable by visible light. The cloak is designed using quasiconformal mapping and is fabricated in a silicon nitride waveguide on aspecially developed nano-porous silicon oxide substrate with a very lowrefractive index. The spatial index variation is realized by etching holes ofvarious sizes in the nitride layer at deep subwavelength scale creating a localeffective medium index. The fabricated device demonstrates widebandinvisibility throughout the visible spectrum with low loss. This siliconnitride on low index substrate can also be a general scheme for implementationof transformation optical devices at visible frequency.
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