Metallo-dielectric diamond and zinc-blende photonic crystals

Diamond and zinc-blende photonic crystals are studied both in the purely dielectric case and in the presence of small inclusions of a low absorbing metal. It is shown that small metal inclusions can have a dramatic effect on the photonic band structure. Several complete photonic band gaps (CPBG's) can open in the spectrum, between the second and third, fifth and sixth, and eighth and ninth bands. Unlike in the purely dielectric case, in the presence of small inclusions of a low absorbing metal the largest CPBG for a moderate dielectric constant (epsilonless than or equal to10) turns out to be the second to third CPBG. The second to third CPBG is the most important CPBG, because it is the most stable against disorder. For a diamond and zinc-blende structure of nonoverlapping dielectric and metallo-dielectric spheres, a CPBG begins to decrease with an increasing dielectric contrast roughly at the point where another CPBG starts to open-a kind of gap competition. A CPBG can even shrink to zero when the dielectric contrast increases further. Metal inclusions have the biggest effect for the dielectric constant epsilonis an element of[2,12], which is a typical dielectric constant at near infrared and in the visible for many materials, including semiconductors and polymers. It is shown that one can create a sizeable and robust second to third CPBG at near-infrared and visible wavelengths even for a photonic crystal which is composed of more than 97% low refractive index materials (nless than or equal to1.45, i.e., that of silica glass or a polymer). In the case of silica spheres with a silver core, the second to third CPBG opens for a metal volume fraction f(m)approximate to1.1% and has a gap width to midgap frequency ratio of 5% for f(m)approximate to2.5%. Within the second to third CPBG of 5%, absorption remains very small (less than or equal to2.6% once the CPBG is centered at a wavelength lambdagreater than or equal to750 nm), which should be tolerable in most practical applications. The metallo-dielectric structures display a scalinglike behavior, which makes it possible to scale the CPBG from microwaves down to the ultraviolet wavelengths. Aluminum, copper, and gold cores yield almost identical results, provided that sphere radius r(s)greater than or equal to250 nm. For r(s)<250 nm the results for different metals can be increasingly different with decreasing r(s), nevertheless, qualitative features remain the same. These findings open the door for any semiconductor and polymer material to be used as genuine building blocks for the creation of photonic crystals with a CPBG and significantly increase the possibilities for experimentalists to realize a sizeable and robust CPBG in the near infrared and in the visible. One possibility is a construction method using optical tweezers, which is analyzed here.