pbg 3d
Yes, I do agree with you about the high cost of high dielectric constant material, and I also want to say the processing (manufacture) cost is another issue. Using now available process is cheaper than developing new process.
Simulation of Photonic Crystal structure is not a big deal, we can keep playing games with pitch/radius, refractive index ratio. But after simulation, even you can get spectacular results, Can you fabricate the device or NOT? Si is well understood material in semiconductor industry, but the process of PBG in Silicon is still under developing. The fabrication tolerance, your design robustness are the main barrier.
As far as I know, I only got 1 paper demonstrating the PBG device, and that is the only one sucessfully showing the fabricated PBG device. If you want, I can share some interesting simulation to you.
I can not comment anything about those kind of material, if your purpose is pure research, then the price of material is not a big deal, at least you do not need large quantity, if you design purpose is for wide range appliation, for large scale production, then I dont think who can afford such kind of extremly expensive material.
Best Regards,