Studies on two-photon lithography in negative SU-8 photoresist demonstrate the possibility of obtaining mechanically stable, stress-free, extended nanorods having lateral sizes of about 30 nm (corresponding to λ/25 resolution). The high resolution achievable with the given combination of materials and fabrication techniques demonstrates its potential for the fabrication of large-scale nanostructures, such as photonic crystals with photonic stop gaps at visible wavelengths.

ring under atmospheric conditions. TEA (2.2 mL, 99+ %) was slowly added drop by drop to the solution under agitation. After 30±45 min stirring the white product was filtered off, washed with DMF, and was finally dried at 373 K for 3±5 h in an oven. After drying the yield was 71 % in weight with respect to zinc nitrate. The same synthesis was repeated adding three drops of H 2 O 2 (35 %) to the DMF solution containing dissolved BDC and zinc nitrate and then the TEA was added directly to the solution.For the second synthesis, which did not produce pure MOF-5, 0.3 g of Zn(NO 3 ) 2 . xH 2 O and 0.227 g of BDC were dissolved in 10 mL of DMF and 2.4 mL of chlorobenzene (99.7 %, also purchased from Alfa Aesar), and three droops of H 2 O 2 were added. The vessel containing the reagent solution was put into a larger closed vessel containing 2 mL of TEA. After one week, the white crystalline product at the interface between the air and solution was filtered off and washed with DMF and then dried for 3±5 h at 373 K.Characterization: Powder X-ray diffraction data were recorded for the as-synthesized and dried sample with a Siemens D5000 powder diffractometer using Cu Ka radiation and a secondary monochromator.Images of MOF-5 crystals were taken with a SEM and with a fieldemission SEM.The specific surface area (SSA) and pore size of the samples were investigated with a quantachrome Autosorb automated gas sorption apparatus using N 2 gas. To measure the SSA, the solvent incorporated in the crystalline structure during the synthesis was completely removed by heating at 473 K under a vacuum of 10 ±6 mbar. Hydrogen-Storage Measurements: For hydrogen-storage measurements we used a volumetric setup that had been previously tested both for room-temperature measurements, using well-known metal hydrides, and at 77 K, using activated carbon.For adsorption measurements at room temperature, the experimental set-up was immersed in a temperature-controlled water bath at 298 K. High purity (99.999 %) hydrogen gas was introduced into a reservoir of known volume and, after thermal equilibrium had been achieved, the gas was permitted to expand into the sample holder.For measurements at 77 K, the sample holder was immersed in liquid nitrogen and the pressure drop due to cooling and to enhanced hydrogen storage was recorded. To calculate the storage capacity of the sample, the experiment was repeated accurately under the same conditions for a blind sample (sea sand) of the same volume, which does not adsorb any hydrogen. The difference in hydrogen pressure drop is attributed exclusively to hydrogen storage.After every adsorption step, the sample was heated under vacuum and the measurement was repeated for a new hydrogen pressure. This procedure ensured that every adsorption value was measured independently from the previous one. The experiment was been performed a second time using a different sample mass. The congruency in the measured storage values for the two experiments was additional evidence of the high accuracy of our measuring system. T...

The universal scaling of a width of photopolymerized line on the exposure dose was observed in polymerization by direct laser writing using tightly focused femtosecond pulses in SU-8 resist. This scaling can be explained as the photopolymerization by a blackbody-type emission. A spectrally broad thermal emission of electrons heated up to temperatures approximately Te∼103K coincides with an IR-absorption band of SU-8 centered at the 2.9μm and had caused polymerization by a cumulative direct absorption. Three-dimensional photonic crystal templates with approximately twice reduced feature size were fabricated with stop band at the fiber communication wavelength of 1.3μm.

High-quality templates of three-dimensional woodpile photonic crystals are fabricated in photoresist SU-8 by use of femtosecond laser lithography. The samples have smooth surfaces, are mechanically stable, and are resistant to degradation under environmental and chemical influences. Fundamental and higher-order photonic stopgaps are identified in the wavelength range 2.0-8.0 microm. These templates can be used for subsequent infiltration by optically active or high-refractive-index materials.

Three-dimensional photonic crystals with a circular spiral architecture were fabricated by direct laser writing ͑DLW͒ in a photoresist. DLW was performed with a laser beam having the direction of propagation and elongation of the ellipsoidal focal region perpendicular to the spirals' orientation. This allowed the reduction of the turning period of the spirals while avoiding the overlap between their adjacent turns. Consequently, optical transmission and reflection spectra of the fabricated samples revealed multiple photonic stop gaps whose shortest wavelength was 0.88 m, the lowest observed so far in spiral structures. These results were qualitatively reproduced by finite-difference time-domain simulations. This fabrication scheme can be useful for DLW of structures where photonic stop gaps along particular directions, rather than complete photonic band gaps, are required.