Dynamic optics for photonic fabrication

Short pulsed laser beams are widely used in three-dimensional fabrication of devices such as artificial bandgap materials, microfluidics, metal nanostructures and embedded waveguides. Structures are created by focusing the laser into a substrate where multiphoton absorption and/or avalanche effects cause permanent material changes. The fidelity of fabrication depends strongly on the quality of the focal spot, which in many cases is impaired by aberrations. This is particularly so when there is a mismatch between the refractive indices of the processed material and the objective immersion medium. We use adaptive optics to compensate aberrations and maintain fabrication performance at depth.

Laser fabrication is typically carried out in a point by point fashion and since feature sizes are sub-micron the processing time for extended structures can become impractically long. A useful progression of the technique that can reduce fabrication times is to generate multiple fabrication spots from the same laser beam. We demonstrate parallel fabrication using dynamic holographic elements to create three-dimensional structures. We also introduce a novel hybrid microlens array/holographic method that permits individual control of hundreds of laser foci in parallel.

We have applied these techniques to fabrication in a range of materials including fused silica, glass, lithium niobate and diamond.  Applications of these methods can be found in optical communications, quantum optics, astrophotonics and spectroscopy.