Femtosecond, and Ion Direct Writing

An analogy to direct laser writing, ion irradiation, has also been used to fabricate tellurite waveguides [91,92]. A 24 pm gap created by two 75 pm-thick silicon covers was used to gate ions to define a channel. The ions had an energy of 1.5 MeV and penetrated 1.5 pm into the tungsten sodium tellurite [WNT] glass. Despite the fact 

Despite their flexibility in terms of the geometry of the formed waveguide and 3D structure capability, direct-writing techniques are restricted to low index contrast. The modes are generally large, and compact devices are not easily obtained due to bending loss. 

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