Using Nature to Pro­duce a Revolu­tion­ary Optic­al Material

An inter­na­tion­al team of research­ers has repor­ted a new way to safe­guard drones, sur­veil­lance cam­er­as and oth­er equip­ment against laser attacks, which can dis­able or des­troy the equip­ment. The cap­ab­il­ity is known as optic­al lim­it­ing. The work, pub­lished in the journ­al Nature Com­mu­nic­a­tion, also describes a super­i­or man­ner of tele­com switch­ing without the use of elec­tron­ics; instead, they use an all-optic­al meth­od that could improve the speed and capa­city of inter­net com­mu­nic­a­tions. That could remove a road­b­lock in mov­ing from 4GLTE to 5G net­works. The team repor­ted that a mater­i­al cre­ated using tel­luri­um nanor­ods – pro­duced by nat­ur­ally occur­ring bac­teria – is an effect­ive non­lin­ear optic­al mater­i­al, cap­able of pro­tect­ing elec­tron­ic devices against high-intens­ity bursts of light, includ­ing those emit­ted by inex­pens­ive house­hold lasers tar­geted at air­craft, drones or oth­er crit­ic­al sys­tems. The research­ers describe the mater­i­al and its per­form­ance as a mater­i­al of choice for next-gen­er­a­tion opto­elec­tron­ic and photon­ic devices. Seamus Cur­ran, a phys­ics pro­fess­or at the Uni­ver­sity of Hou­s­ton and one of the paper’s authors, said while most optic­al mater­i­als are chem­ic­ally syn­thes­ized, using a bio­lo­gic­ally-based nan­o­ma­ter­i­al proved less expens­ive and less tox­ic. ​“We found a cheap­er, easi­er, sim­pler way to man­u­fac­ture the mater­i­al,” he said. ​“We let Moth­er Nature do it.” The new find­ings grew out of earli­er work by Cur­ran and his team, work­ing in col­lab­or­a­tion with Wern­er J. Blau of Trin­ity Col­lege Dub­lin and Ron Orem­land with the U.S. Geo­lo­gic­al Sur­vey. Cur­ran ini­tially syn­thes­ized the nano­com­pos­ites to exam­ine their poten­tial in the photon­ics world. He holds a U.S. and inter­na­tion­al series of pat­ents for that work. The research­ers noted that using bac­teria to cre­ate the nano­crys­tals sug­gests an envir­on­ment­ally friendly route of syn­thes­is, while gen­er­at­ing impress­ive res­ults. ​“Non­lin­ear optic­al meas­ure­ments of this mater­i­al reveal the strong sat­ur­able absorp­tion and non­lin­ear optic­al extinc­tions induced by Mie scat­ter­ing over­broad tem­por­al and wavelength ranges,” they wrote. ​“In both cases, Te [tel­luri­um] particles exhib­it super­i­or optic­al non­lin­ear­ity com­pared to graphene.” Light at very high intens­ity, such as that emit­ted by a laser, can have unpre­dict­able polar­iz­ing effects on cer­tain mater­i­als, Cur­ran said, and phys­i­cists have been search­ing for suit­able non­lin­ear mater­i­als that can with­stand the effects. One goal, he said, is a mater­i­al that can effect­ively reduce the light intens­ity, allow­ing for a device to be developed that could pre­vent dam­age by that light. The research­ers used the nano­com­pos­ite, made up of bio­lo­gic­ally gen­er­ated ele­ment­al tel­luri­um nano­crys­tals and a poly­mer to build an elec­tro-optic switch – an elec­tric­al device used to mod­u­late beams of light – that is immune to dam­age from a laser, he said. Orem­land noted that the cur­rent work grew out of 30 years of basic research, stem­ming from their ini­tial dis­cov­ery of sel­en­ite-respir­ing bac­teria and the fact that the bac­teria form dis­crete pack­ets of ele­ment­al sel­en­i­um. ​“From there, it was a step down the Peri­od­ic Table to learn that the same could be done with tel­luri­um oxy­an­ions,” he said. ​“The fact that tel­luri­um had poten­tial applic­a­tion in the realm of nan­o­photon­ics came as a serendip­it­ous sur­prise.” Blau said the bio­lo­gic­ally gen­er­ated tel­luri­um nanor­ods are espe­cially suit­able for photon­ic device applic­a­tions in the mid-infrared range. ​“This wavelength region is becom­ing a hot tech­no­lo­gic­al top­ic as it is use­ful for bio­med­ic­al, envir­on­ment­al and secur­ity-related sens­ing, as well as laser pro­cessing and for open­ing up new win­dows for fiber optic­al and free-space com­mu­nic­a­tions.” Work will con­tin­ue to expand the material’s poten­tial for use in all-optic­al tele­com switches, which Cur­ran said is crit­ic­al in expand­ing broad­band capa­city. ​“We need a massive invest­ment in optic­al fiber,” he said. ​“We need great­er band­width and switch­ing speeds. We need all-optic­al switches to do that.” In addi­tion to Cur­ran, Orem­land and Blau, research­ers involved with the pro­ject include Kang-Shy­ang Liao and Surendra Maharjan, both of UH; Kang­peng Wang, Xiaoy­an Zhang, Ivan M. Kislyakov, Ningn­ing Dong, Saifeng Zhang, Gaozhong Wang, Jin­tai Fan, Long Zhang, Jun Wang, Xiao Zou, Hong­zhou Zhang, Juan Du, Yux­in Leng and Quan­zhong Zhao, all with the Shang­hai Insti­tute of Optics and Fine Mech­an­ics at the Chinese Academy of Sci­ences; Kan Wu and Jian­ping Chen, both with Shang­hai Jiao Tong Uni­ver­sity; and Shaun M. Baes­man with the U.S. Geo­lo­gic­al Sur­vey. Kang­peng Wang has an addi­tion­al affil­i­ation with the Tech­nion-Israel Insti­tute of Tech­no­logy and Gaozhong Wang is also affil­i­ated with Trin­ity Col­lege. Source: Uni­ver­sity of Houston