MechSE achievement named one of the year's top developments in optics

Now in its 40^th year, the professional society Optica (formerly the Optical Society of America) selects the 30 most interesting developments in optics for their end-of-year special issue of the magazine Optics and Photonics News. Professor Gaurav Bahl's work on chip-scale optical isolators, published in Nature Photonics in 2021, made the cut as a breakthrough development in “Optics in 2022”. The experimental work was conducted by students Oğulcan Örsel (a PhD candidate) and Benjamin Sohn (now working at PsiQuantum).

In the highlighted work, “Electrically driven optical isolation through phonon mediated photonic Autler-Townes splitting,” the researchers demonstrated a new chip-scale optical isolator that, for the first time, achieves ideal behavior. Optical isolators are found in every benchtop laser system and function as diode-like components that only allow light to pass through in one direction. However, there have not been any good solutions for producing these components in miniaturized photonic integrated circuits—which is widely recognized as a major technical challenge that has been holding back innovation. Bahl’s group had previously developed a technique using sound waves to produce isolators, which they took to the ultimate limit in this work, thanks to innovative design and the use of lithium niobate as a photonic material. The final device combined the transparency of a high-quality waveguide in the forward direction with near-perfect attenuation in the blocking direction, and set a new record figure of merit for on-chip isolators.

Bahl’s work has been highlighted by Optica (OSA) on several past occasions, in 2012, for the experimental observation of spontaneous Brillouin cooling, and in 2013 for the demonstration of microfluidic optomechanical sensors. His group’s work was also included in Optica’s top research in 2018, for their Nature Photonics paper, “Time-reversal symmetry breaking with acoustic pumping of nanophotonic circuits” – closely related work in which his team originally demonstrated that sound waves can be used to produce ultraminiature optical diodes that are tiny enough to fit onto a computer chip.

The Bahl Research Group performs experimental research at the interface of optical and mechanical systems. Their research focuses on systems that incorporate both optical and mechanical elements. Particularly, they are interested in mechanisms where light interacts with photonic microdevices such as radiation pressure, gradient force, electrostrictive pressure, and photothermal effects to produce new sensors and actuators.