In general, the higher the refractive index contrast, the wider the photonic band gaps.  The lattice constant does not have an affect on the band gap, but it has everything to do with where the band gaps occur in frequency.  The larger the lattice spacing, the lower the frequency of the band gaps.  Notice that I am using the plural version of band gap because many lattices have multiple band gaps.

For more information on this, take a look at Lecture 14 here:

http://emlab.utep.edu/ee5390em21.htm

Before watching the video or looking through the notes, you may want to work through lectures 7, 8, and 12 that cover some preliminary topics.

Hope this helps!

Dear Mrs. Thirumaran,

The PBG certainly depends on the refractive index ratio and the lattice parameter as can be seen in the dispersion relation. For a good read I recommend P. Yeh and Amnon Yariv boods especially the chapter on alternating photonic crystal.

You can also link to my demonstration at wolfram, where it is clearly seen that changes in the ref. index will change the width of the PBG

http://demonstrations.wolfram.com/ElectricFieldTransmittanceInA1DAlternatingPhotonicCrystal/

i hope this helps

The refractive index of Bragg is depend on the intensity of light and independent of lattice contact 

Thank you soo much everyone.... Will go through that... 

Is this same for all three classification of Photonic crystals? And as we compare Bragg reflector/Bragg grating to 1D crystals, do we have anything to compare for 2D Photonic crystals?

The rules for lattice constant stay about the same for 1D, 2D, and 3D.

Thank you Rumpf

Can you suggest me  examples for 2D and 3D crystals , like Bragg reflector for 1D?

Take a look at Lecture 14 here:

http://emlab.utep.edu/ee5390em21.htm

This may have what you are looking for.