![]() Besides, since LAP and DAST crystals have strong ionic bonding, processing is relatively easy compared to normal organic crystals bonded by only weak intermolecular forces. ![]() In this way, technology to precisely process fragile organic materials has not been standardized yet and didn’t result in actual application of organic NLO crystals. ![]() Contrastively, they pointed out a relation between processed surface roughness and crystal orientations. By optimizing several conditions for processing, sub-nm rms surface roughness in 1 mm square area were obtained on the b-plane. Namba et al., also processed organic DAST crystals using diamond turning 20. They found that there is no relation between processed surface roughness and processed crystal orientations. They tried single point diamond turning for organic L-arginine phosphate (LAP) crystals to generate high quality optical surfaces and achieved ten-nm level rms roughness typically. First processing for the organic crystals was reported by B. In order to develop novel organic NLO devices, it is necessary to precisely cut out properly shaped crystals with a particular crystal-facet from the as-grown bulk crystal. Consequently, as-grown organic crystals with routine crystal habit have been used for past experiments and hence, application uses of organic NLO crystals have been limited. Since organic materials are very brittle, having hygroscopic properties, low melting temperatures and particular cleavage planes owing to weak intermolecular bonding, conventional processing technologies used for inorganic materials cannot be extrapolated to obtain arbitrary shape crystals and fine optical surfaces. On the contrary, precise processing technologies for organic crystals have hardly been developed. Hence, crystal growth techniques for organic NLO crystals have been advancing steadily. The internal crystal quality for organic DAST crystals can also be remedied by employing an annealing aftertreatment 18. For example, large size DAST and BNA single crystals, i.e., exceeding 1000 mm 3 volume, have been successfully grown by optimizing the kind of solvents or concentration in the crystal-growing solution 16, 17. Recently, however, techniques for growing high-quality, large-size organic NLO single crystals have been improved. To expand the use of organic NLO crystals in various fields of photonic technology, where inorganic crystals are exclusively used, the challenges in high-quality crystal growth and precise processing for bulk organic crystals must be addressed. Organic NLO crystals, such as 4-dimethylamino-N-methyl-4-stilbazolium-tosylate (DAST) 1, 2, N-benzyl-2-methyl-4-nitroaniline (BNA) 3, 4, 4-N,N-dimethylamino-4-N-methylstilbazolium 2,4,6-trimethylbenzenesulfo-nate (DSTMS) 5, 6, 2-(3-(4-hydroxystyryl)-5,5-dimethylcyclohex-2-enylidene)malononitrile (OH1) 7, 8, and 2-(4-hydroxy-3-methoxystyryl)-1-methylquinolinium 2,4,6-trimethylbenzenesulfonate (HMQ-TMS) 9, 10 have studied for mainly THz-wave generations and detections using second-order NLO effects 11, 12, 13, 14, 15 however, their applications are still quite limited. ![]() Therefore, research and development of organic NLO materials has been becoming more and more important to establish future society. Gigantic nonlinearity, ultra-fast response due to π-electrons, low refractive index and its wavelength-dispersion in organic NLO materials can give breakthrough in these devices. Organic NLO materials can be particularly expected to support these devices in next-generation highly-advanced information society, where further improvements in speed of signal-processing, frequency-bandwidth, power consumption, compactness of devices are strongly required. Nonlinear optical (NLO) effects in materials have been widely utilized for optical signal-processing devices in information-telecommunication system. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |