Modification of LED radiation pattern by implementation of 1D Fresnel structure in the surface

In this contribution, we present modification of far field of light emitting diode (LED) with implemented Fresnel structure in the LED surface. Fresnel structures were prepared in one-dimensional arrangement with two different foci f₁ = 12.5 μm and f₂ = 1 cm. Structures were etched directly in the LED emitting surface using electron beam lithography with the etched depth for the structure with f₁ and f₂ app. 200 nm and 400 nm, respectively. Due to application of these structures, LED far field narrowing was observed, which is documented by goniophotometer measurements. For the structure with f₁ and f₂, the intensity decrease for angles ±30° – ±50° is app. 3-4% and 5-6%, respectively, in comparison to the Lambertian profile.