Light emitting diodes are shown to be excellent sources for illumination if the problem for promoting light-emitting efficiency is solved. The optical efficiency of a conventional light-emitting diode is usually less than 5% because most of the light emitted in the active region inside the diode cannot escape out of the diode. How to promote the optical efficiency of light-emitting diodes attracted great attentions in recent years. We present a diode structure with two photonic crystal layers added to a conventional light-emitting diode. One photonic crystal layer

with a parabolic surface shape

reflects the light from the pn junction travelling sideways to the direction near the axis of the parabolic surface

so that they travel in a small solid angle along the axis and can escape out of the diode. Another photonic crystal layer

shaped like a disk

reflects light travelling in the opposite direction to the output direction

so that the diode emits light just in one direction. In the structure

the pn junction is at the focus plane of the parabolic photonic crystal layer. We find that for the diameter of the pn junction region being 2 F and the distance from the focus plane to the output surface being

H

=63.83 F

all the light from the pn junction can go out of the diode

thus a nearly 100% optical efficiency can be achieved. Here F represents the focus length of the parabolic surface. As an example

we designed a high efficiency light-emitting diode operating in the wavelength region from 1 250～1 850nm with the central wavelength being 1 550nm. The photonic crystals designed in the example are made of PbTe and Na

3

AlF

6

. The thickness of each kind of material in each period is 127.42nm. The photonic crystals are designed to be of 15 periods and of one-dimensional in structure. The structure presented in this paper can be applied to diodes operating at any other wavelength region. The light-emitting diode presented in this paper is unique in structure

efficient for operation

and more easy and practical for production than those adopting two dimensional photonic crystals investigated before.