Three-dimensional periodic microstructures of aluminum oxide, which are important for creating photonic band-gap structures (PBGs), were fabricated by laser rapid prototyping by means of laser-induced direct-write deposition from the gas phase. The structures consisted of layers of parallel rods forming a face-centered tetragonal lattice with lattice constants of 66 and 133 micrometers. These structures showed transmission minima centered around 4 terahertz (75 micrometers) and 2 terahertz (150 micrometers), respectively. PBGs will allow precise control of the optical properties of materials, including lasers without threshold.

The retina of rabbits was coagulated with different wave-lengths (570-630 nm) using a tunable dye laser with Rhodamin 6G. To achieve comparable ophthalmoscopic appearance the intensity of the laser beam was varied with neutral filters of varying absorption. Histologic examination of fresh coagulation effects and 3-week-old coagulation scars showed no difference in relation to the wave-length used. Theoretically, 577 nm seems to be a particularly useful wavelength for the treatment of a wide variety of retinal lesions because it is not absorbed in xanthophyll and penetrates opacities of the optic media better than argon blue green. Furthermore, it is absorbed maximally in hemoglobin, making it particularly suitable for the coagulation of blood vessels.

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