Laser Writer

The laser writer creates precisely defined arrays of micrometer-scale metallic near-field optical apertures (Figure 1 shows an array of 30 micron apertures with 100 micron spacing between centers).

Figure 1 4 X 4 Array of aluminum apertures (30 micron diameters)

  While the apertures are usually an aluminum metalization, other metals may also be used to form an aperture.  The apertures are formed by first spin coating a glass substrate with photoresist sensitive to shorter wavelengths of light.  An Argon-Ion laser operating at 458 nm is collimated and then focused through an Olympus microscope to provide the energy to expose the photoresist.  The photoresist-coated substrate is mounted on a Prior microscope stage that can be positioned in x and y at one-micron increments under computer control.  When the stage has moved to the location of an aperture, an electromechanical shutter opens, exposing the photoresist.  Development of the exposed positive photoresist exposes the defined patterns in the photoresist.

Next, the substrate with the photoresist is coated with aluminum or other materials by sputtering in a vacuum chamber.  Immersion in acetone dissolves the photoresist, lifting off the aluminum overlaying the photoresist that was sputtered onto the substrate.  Where the photoresist was removed by development, the aluminum adheres to the substrate and survives the immersion in acetone leaving the desired pattern on the substrate.

Patterns can be written as rectangular arrays with a different number of elements and different step sizes in the x and y directions with a resolution of one micron.  It is also possible to arbitrarily move to any position within the movement limits of the stage and expose the photoresist.  This permits the generation of virtually any shape with micron-scale resolution.