3D Tapered Waveguides in Volume Photopolymers

Sullivan, Amy C.; McLeod, Robert R.

doi:10.1364/ipnra.2007.itua7

Cited by 2 publications

(1 citation statement)

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“…Inherent absorption of the initiator tends to reduce the intensity on the back of the part; this can be compensated by appropriately compensating with variable writing power. 13 '-I-. Typical results of this process are shown in Figure 3.…”

Section: Direct Write Of 3d Waveguidesmentioning

confidence: 99%

Three-dimensional waveguide arrays via projection lithography into a moving photopolymer

2008

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We demonstrate a projection lithography method that induces optical index changes in a flexible polymer cable that is continuously translated through the image plane. We demonstrate that a static spot pattern generates a grid of waveguides along the cable length via a continuous extrusion process. Rotations or scaling of the optical spot array can fabricate image inverters or magnifying face plates in a single process step. The resulting polymer devices have applications in optical backplanes, endoscopes for medical applications and lightweight imaging systems. MOTIVATIONThe two dimensional array of vertical cavity surface emitting lasers (VCSEL) is an attractive transmitter for ultra shortreach optical communication due to the potentially high bandwidth per unit area. To capitalize on this large bandwidth density, however, requires a mating waveguide array with pitch matching the VCSEL spacing, which is measured in 10s of µm. The waveguides in the array must be precisely arranged in a two-dimensional grid, making their fabrication difficult with traditional planar lightwave circuit processes.One can extend 2D planar processes to create 3D arrays by repeating process steps to align and expose layers sequentially, 1 though the tolerances on layer thickness and in-plane alignment make this approach challenging as the number of layers grows. Another approach is to fabricate each layer separately and then stack at the wafer scale 2 followed by dicing of individual parts. Finally, nearly arbitrary 3D waveguide arrays can be formed directly in glass via femtosecond micromachining. 3 This has the advantage of producing a single monolithic part with tight tolerances but the sequential, single-point exposure of waveguides may be too slow for industrial applications. In addition, glass substrates may not meet the cost requirements for high-volume optical backplanes, motivating the use of polymer hosts.We propose and demonstrate a new form of 3D lithography that can form 3D polymer waveguide arrays in a single process step. The material is a highly sensitive volume photopolymer, enabling rapid processing with small total optical power. The lithography method can create nearly arbitrary 3D waveguide structures including rotations and fan-outs. We demonstrate the process with a 4 by 4 array on 60 µm centers deeply buried in a 4 mm by 4 mm substrate. BACKGROUND MaterialsTraditional photopolymers such as photoresists are patterned by exposure and subsequent monomer removal via solvent wash, making them inappropriate for the fabrication of 3D index structures where solvent access is impossible. In contrast, thick polymers developed for holography require no thermal or wet processing. 4 , 5 , 6 The process by which optical exposure causes development of index structures in these materials is an active area of research. 7 , 8 , 9 In the simplified model, a bleaching initiator absorbs a photon with wavelength typically between ~350 and ~600 nm and

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Section: Direct Write Of 3d Waveguidesmentioning

confidence: 99%