Experimentally, there are many different ways to fabricate a photonic crystal and holographic lithography is one of them. The idea of this method is to use the interference of a few coherent laser beams and record the interference pattern of these beams by photo-sensitive materials. This method can be used to produce structures that are difficult to make by other methods and from computer simulations, we can produce spiral structure (Fig. 1a and 1b) by this method too. This kind of structure is found to possess novel optical properties from the calculation of its band structure and has great potential for applications. The dimension of the structure is of the same order as the wavelength of the laser beams and hence it is easy to scale the size of the structure by changing the wavelength of the laser used.
