Embossable Grating Couplers for Planar Waveguide Optical Sensors

Abstract

Planar optical waveguides are an attractive tool for use in analytical chemistry and spectroscopy. Although similar to fiber optics, planar waveguides have been slow to be commercially accepted due to the difficulty of coupling light into the guide. Generally, prism coupling is the method of choice in the laboratory, as efficiencies approaching 80% can be reached. However, prisms are impractical for routine use for several reasons: expensive positioning equipment is required, coupled power is sensitive to environmental fluctuations, and prism coupling prohibits the fabrication of a truly planar device. The use of thin gratings on the surface of the waveguide allows for a two-dimensional structure to be maintained, while providing enough efficiency to be useful as a sensor. Our research efforts focus on developing a technique to make inexpensive, reproducible gratings that are easy to fabricate. By chemically modifying the surface of a commercial grating with a suitable release agent, it is possible to emboss replica gratings onto a variety of waveguide types. The fabrication of embossed gratings will be described, and their performance on glass, ion-diffused, polymer, and semiconductor waveguides will be presented.

Ordered Nanowell Arrays

“…Figure 5 shows a polymeric film with a hexagonally packed array of 600-nm-tall polymeric cones obtained by peeling and inverting the polymer film off of the chemically etched imaging fiber. Since fused fiber-optic bundles and their individual optical fiber cores can be heated, tapered, and shaped into a variety of architectures and dimensions, the facile creation of a variety of polymeric patterns and struc- 20,21 or biosensor arrays. [22][23][24] The ultimate utility of this microfabrication methodology may arise by exploiting the fact that each well is connected to its own optical channel 25 allowing it to be addressed individually or as part of the entire imaging fiber array.…”

“…Since fused fiber-optic bundles and their individual optical fiber cores can be heated, tapered, and shaped into a variety of architectures and dimensions, the facile creation of a variety of polymeric patterns and structures can be envisioned. In addition, reusable nanowell arrays and the polymeric pattern-transfer methodology could be used to fabricate microlens arrays, , embossable gratings, , or biosensor arrays. − The ultimate utility of this microfabrication methodology may arise by exploiting the fact that each well is connected to its own optical channel allowing it to be addressed individually or as part of the entire imaging fiber array. Thus, after well fabrication, light could be employed to initiate additional processes such as deposition, polymerization, or ultraviolet curing to facilitate multistep operations that address complex microfabrication challenges.…”

Microfluidics: Recent Advances Toward Lab‐on‐Chip Applications in Bioanalysis

“…The various limitations of this method include longer duration, inability to produce shell features, and high pressures cannot be achieved in thicker substrates. The various applications include compact discs (CDs), diffraction grating waveguides, [ 52 ] as well as high‐resolution track, features down to 25 nm [ 53 ] for etching, and sacrificial masks. Various stamps for imprint lithography have been fabricated with a variety of materials including quartz [ 54 ] and poly‐methyl methacrylate (PMMA).…”

Micro/Nano Patterning on Polymers Using Soft Lithography Technique

“…The minimum feature size of less than 100 nm can be accurately replicated using this technique. It has been successfully used for mass production of devices such as compact disks (CDs) [15,16], diffraction gratings [17], holograms [18], and microtools [19]. The prime or master mold is generally fabricated on a rigid material (silicon, nickel, glass, or SU8 photoresist) using a standard photolithography and micromachining techniques.…”