The field of photonic band gap structures, also called photonic crystals, is a relatively recent field of research but is fast developing. It all started in 1987 with two papers by Eli Yablonovitch of UCLA and by Sajeev John (Principal Investigator, Photonics Research Ontario) published simultaneous but independently, and it has been growing exponentially ever since. The number of publications on the subject doubles every two years and keeping up to date has become a real challenge. A paper which strives to review the field every few years is of great help to researchers considering the many aspects the subject presents. So, one of the most important considerations for the success of such papers is opportunity. There had been very good reviews in the recent past but it seemed that recent advancements called for a new revision of the field. A very important consideration is comprehensiveness. While the underlying idea is innovative and original, many concepts can be borrowed from solid state physics which greatly simplify things. There remain, however, many aspects which are to be considered anew. Among them, materials aspects are of the greatest importance. Design of photonic band gap systems is but the initial step to the realization of countless applications, but a huge effort is required to obtain performing structures. The intrinsic nature of photonic band gap materials make them heterogeneous and varied and the number of approaches is only limited by imagination. This puts a challenge in trying to cover all the dimensionalities, frequency ranges, and fabrication techniques. A balance between the seminal work and the most recent advancements is important as well.

The paper is a review and is intended to facilitate the work of researchers and especially of those just entering the field, be it as newcomers or as students just starting. One of the most enriching factors in research is the mixture of disciplines and approaches coming from very distinct areas which add new perspectives to a common goal. This is especially true for materials aspects and even more so in an area such as that of photonic crystals where many different avenues have been and are being explored. So, trying to present a bird’s eye view of the field ahead is capital. The paper attempts to make photonic crystals something not private to the physics realm alone and gives a semblance where chemistry and engineering contributions and expectations can be readily appreciated.

This article, after giving a comprehensive review of basic concepts, involving phenomena along with potential and current applications, makes an up-to-date summary of materials issues in photonic band gap crystals. It is not only very comprehensive in the scope of the techniques covered, but also tries to make the physics of photonic band gaps accessible to scientists with very different profiles—physicists, chemists, engineers—and provides them with leads for further reading and research. In trying to be fair, for every subject, it includes a summary of the first ground-breaking works along with the most recent and innovative advancement.

Our group began some 10 years back in an interdisciplinary institute where physicists and chemists naturally collaborated. Merging together the techniques and know-how from both sides produced encouraging results and contributed to a fast developing method. The approach taken in our group proved to be a successful one and it is nowadays one of the most widely used methods for the production and study of photonic band gap materials owing to its simplicity and the low cost of the techniques involved. The background in semiconductor physics prevailing in the group made the transition easy in as much as many concepts in photonic band gaps are similar to those found in solid state physics.