We report on optically pumped lasing from dye-doped, graded-spacing layer structures of dichromate gelatin emulsions fabricated using two-beam holographic interference. The graded layers exhibited deep and wide photonic band gaps. Multimode lasing with both a low threshold and a high quality factor was observed at the band edge of the photonic band gap. We modeled the emissions from the dye-doped graded layer system using a finite difference time domain technique and achieved good agreement with experimental results. © 2008 American Institute of Physics. ͓DOI: 10.1063/1.2907488͔ Photonic crystals exhibiting band gaps in which electromagnetic wave propagation is not possible have attracted much interest due to the potential that they can manipulate photons in optical microdevices.1 Among the many unique properties of photonic crystals, the control of the photonic density of states has a direct effect on the spontaneous emission of photons, which is an important capability in optoelectronics devices such as lasers, 2 light emitting diodes, 3 microwaveguides, 4 and many other promising photonic devices.5 It has been proposed that the enhancement of the spontaneous emissions in one-dimensional ͑1D͒ photonic crystals doped with gain materials is possible because of the localization at the band gaps and the high density of states at the band edges. 6 The realization of this enhancement was first demonstrated in GaAs light-emitting diodes sandwiched between stacks of 1D Bragg reflectors.7 Since then, lasing from dye-doped polymeric multilayers using distributed feedback and defect modes has been observed. 8,9 Recently, studies on band-edge and defect-mode lasing in dye-doped liquid crystals have attracted interest. 10 In these previous studies, equally spaced layers were employed in the systems. Lasing from 1D layers with gradually changing spacings ͑graded layers͒ is expected to be possible as well.One-dimensional stacks have been fabricated using a time-consuming layer-by-layer spin-coating method.7-9 Holographic lithography that employs the interference of multiple coherent beams is more efficient and has been used to fabricate two-dimensional as well as three-dimensional microstructures in photoresists.11 Furthermore, high-resolution holographic gelatin emulsions can be used to record the interference patterns.12,13 One advantage to using holographic gelatin emulsions is that the structure resulting from the interference is self-supporting inside the gelatin. It was further demonstrated that, with a volume hologram made from dichromate gelatin ͑DCG͒, highly efficient and wide-bandgap 1D layer structures could be achieved.14 The wide-bandgap results from the graded spacing of the 1D layers obtained by the differential swelling of the gelatin during the development process.14 Here, we show that lasing from dyedoped 1D graded layers in DCG holographic emulsions fabricated using two-beam interference is possible. Multimode lasing with both a low threshold and a high quality factor was observed at the band edge of the p...

We have fabricated spherical layer structures that exhibit complete photonic bandgaps in the visible range in dichromate gelatin emulsions by holographic interference. The complete bandgap was not a result of the high dielectric contrast but was due to the fact that the spherical layer structure was isotropic with equal spacing in all accessible directions. Angular dependence spectral measurements of the spherical layer structures were in good agreement with the expected results from an ideal structure of dielectric concentric spherical shells with equal spacing. Our fabrication technique and results could pave the way for new applications using complete bandgap photonic crystals.

Lasing requires an active gain medium and a feedback mechanism. In conventional lasers the feedback is provided externally, e.g. by mirrors. An alternate approach is through Bloch waves in photonic crystals composed of periodic dielectric materials in which propagation of light in certain frequency ranges, known as photonic bandgaps, is forbidden. Compared to periodic crystals, quasicrystals have higher symmetry and are more favorable for the formation of photonic bandgaps. Hence quasicrystals are more efficient in providing the feedback mechanism for lasing. Here we report observation of lasing at visible wavelengths from dye-doped three-dimensional icosahedral quasicrystals fabricated in dichromate gelatin emulsions using a novel seven-beam optical interference holographic method. Multi-directional lasing exhibiting the icosahedral symmetry was observed. The lasing modes and pattern were explained by using the lasing condition expressed in the reciprocal lattice space of the icosahedral quasicrystal.