ULTRA-THICKOPTICALCOMPONENTS USINGLF55GNPHOTOSENSITIVE FLEXOPOLYMER

We present thephotosensitive flexopolymer LF55GNasanewmaterial forthe realisation ofthick three-dimensional optical microstructures. Microstructures withathickness upto4 millimetres andwithanaspect ratio of10canberealised using onlyasingle UV exposure step andina timeframeofminutes. Nobaking process isrequired forthepatterning oftheLF55GNflexopolymer. Theelastomeric nature ofthematerial allows fabricating thick structures onflexible substrates andforces induced bythedeformation oftheflexible substrate areeasily supported. Combining thecasting method andUV lithography, thick optical components suchasright-angle prisms withnearly vertical sidewalls andgoodsurface quality aresuccessfully fabricated. C~~~~~~~~~~~ andtime-consuming. Polymers areconsidered as promising materials forreplacing glass dueto their lowcost, lowweight andeaseoffabrication. Several polymers withgoodoptical transparency andcontrollable refractive indexhavebeenused foroptical applications. Polymers such asPMMA, Polycarbonate, andSU-8aretypical materials that havebeenusedforfabricating optical components including waveguides, lenses, prisms andmirrors. Differenttechniques includingmolding, replication, etching andlithography processhave beendeveloped forprocessing polymers. UV- lithography isone ofthesimplest andbest established methods permitting thefabrication of features withhighresolution andwell-defined shape. SU-8isanegative polymer thatcanbe patterned byaUV lithography process torealize ultra-thick microstructures upto2mm withahigh aspect ratio. Duetoitschemical inertness, good mechanical andoptical properties, SU-8hasbeen usedinavariety ofapplications. However, SU-8 hasa numberofdisadvantages suchasthe development ofstress atthesubstrate interface, leading toadhesion problems, anditposes difficulties instripping byconventional methods. Inaddition, patterning a thick SU-8structure requires many spinning/exposure steps, as, depending ontheviscosity, layers ofmaximum 0.2mm canbeprocessed inasingle step. Here, weintroduce theflexopolymer LF55GNasanew negative photoresist that hasalladvantages ofSU- 8butnoneofthedisadvantages. Moreover, the LF55GN flexopolymer presents goodoptical properties andcanbeusedforthefabrication of optical components.