The research objective of this collaborative award is to develop flexible and cross-platform methods to fabricate three-dimensional (3D) lightwave circuits and photonic crystal structures in transparent media. A laser direct writing technique using high-repetition-rate femtosecond laser will be explored to produce compact 3D lightwave circuits. The approach takes advantages of multi-photon process induced by ultrashort laser pulses to initialize a universal photosensitivity response to change refractive indices in a wide array of optical materials. Bulk heating effects from high-repetition laser pulses will be utilized to mitigate laser-induced material damages to minimize optical loss and to achieve desired device performance of lightwave circuits. To fabricate 3D periodic photonic structures, multi-layer near-field diffractive optical elements will be developed to produce 3D interference patterns. Periodic photonic structures such as diamond-like photonic crystals will be fabricated using this one-optical-element and one-laser-exposure holographic fabrication process.
If successful, the results of this research will yield a cross-platform laser manufacturing technique to fabricate high-quality lightwave circuits in a wide array of optical substrates. The fabrication technique will enable new 3D photonic circuit architectures that allows lightwave circuits to be routed vertically and continuously in- and out- of a plane. This will drastically increase the density, functionality, and complexity of the optical circuitry. The success of this research will also enable the fabrication of mid-IR fiber lasers and sensor devices for applications in chemical sensing and structural health monitoring in harsh environments. The holographic laser fabrication developed from this award can be conveniently built into the existing multiple mask fabrication flow for integrated optoelectronic circuit manufacturing. This enables the monolithic integration of photonic crystal structures with other on-chip optical components for widespread applications. This award will also support an interdisciplinary training program for undergraduate students on the integrated laser manufacturing and product innovation. Through undergraduate extracurricular activities on robotics and minority outreach activities, the proposed education programs will attract female and under-represented minority students to study engineering and science at both undergraduate and graduate levels.
This research project explored laser fabrication of three-dimensional micro-optic and nano-optic devices for telecommunication and sensing applications. By studying laser matter interactions, this research project sheds light on how femtosecond short laser pulses and their spatial energy distribution can be used to engineer material modification at nanometer scales. Based on these scientific knowledges, 3D optic devices with exceptional high optical and mechanic qualities were fabricated in a wide array of optical substrates for a wide ranges of photonics applications. The three-dimensional architecture enabled by the laser fabrication technique has drastically increased the density, functionality, and complexity of optical circuitry. The holographic laser lithography technique developed by this project provides a unique opportunity to integrate 3D photonic crystal structures with other optoelectronic devices on-chip. The hologrpahic laser lithography technique developed by this project can be conveniently built into the existing multiple mask fabrication flow for integrated optoelectronic circuit manufacturing. This enables the monolithic integration of photonic crystal structures with other on-chip optical components. Teaming up with local industry, this research project enabled the University of Pittsburgh to provide an interdisciplinary training program for our undergraduate students on the integrated laser manufacturing and product innovation. It has produced a number of highly trained science and engineering leaders in micro-electronics and photonics area.
