Abstract: An improved waveguide is disclosed. The waveguide comprises four or five layers, an inner core polymer, one or two layers of outer cladding polymer either on one side of the core of sandwiching the inner core polymer, and two layers of a dielectric reflector sandwiching the outer cladding polymer. The refractive index of the inner core polymer is greater than that of the outer cladding polymer. Further, the refractive index of the outer cladding polymer is greater than that of the dielectric reflector. Further, the waveguide can be used to create a physically unclonable function. A light source and an image sensor may be disposed on a printed circuit board. The waveguide may be disposed on the printed circuit board so that light emitted from the light source traverses the waveguide before reaching the image sensor.