In his 1899 lectures Light Waves and Their Uses A. A. Michelson writes:

What would be the use of such extreme refinement in the science of measurement? Very briefly and in general terms the answer would be that in this direction the greater part of all future discovery must lie.

What Michelson was advocating for was higher precision in scientific measurements. The answer to his call came over half a century later in 1960 with the invention of the laser. Since then lasers have become synonymous with precision and not just in the scientific community, fiber optic communication, consumer electronics and even the Internet are all built around the laser. The Ultrafast Laser Lab’s research aims to continue the laser revolution, using laser optics to advance science on two fronts:

Fundamental Physics: Ultrafast Dynamics and Ultrasmall

Research in ultrafast is truly cross-disciplinary since ultrafast processes are relevant in a wide range of fields, from semiconductor technology to bioprotein functionality. A key focus of our research is into the ultrafast of the ultrasmall. Man-made nanostructures provide a fascinating playground into the laws of quantum mechanics. Being small provides a complete new functionality and generates new applications all through novel ultrafast dynamics.

Short optical pulses are produced by compressing a submicrosecond duration pulse into 100 femtoseconds. That corresponds to an intensity increase greater than one million. Also, since the optical source is a laser, all the energy can be focused into a spot size comparable to the wavelength of light. The result is a beam with an intensity measured in TW/cm2. Such an intense beam seriously perturbs any matter it interacts with, moving our exploration into the nonlinear regime. We now have access to excited states of the system, can read out novel information about system symmetry, and can bridge transitions that normally would be forbidden. We can control the system in novel and often counter-intuitive ways, and read out information from the system that would normally remain hidden.

Applied Physics: Laser Material Processing

Selective laser melting (SLM) is a variant of additive manufacturing (AM) that has drawn considerable attention from industry over the past decade. SLM promises to consolidate many-step, complex manufacturing processes, which are often spread out over many facilities, into one single machine, allowing for direct 3D design to final part production. It offers engineers also limitless design freedom, whether it be custom hip implants or rocket engines.

However, despite sustained industrial investment, SLM part quality continues to suffer from inconsistency across individual parts, build volumes, machines and facilities. Even after time and capital intensive optimization, which is often specific to a given part, machine and/or material, the complex interplay of the physical phenomena underlying the process can still lead to stochastic outcomes. Robust and quantitative process monitoring and feedback control are essential tools required to overcome these challenges.

We apply inline coherent imaging (ICI) to SLM when it is happening to track performance in real-time. ICI has a proven track record including successful commercialization in the fields of laser welding, cutting and micromachining. It promises to help unravel the complicated dynamics at the heart of laser 3D writing so we can build more complicated devices with a particular eye to novel materials.