Princeton University

School of Engineering & Applied Science

Photonic topological insulators and pseudomagnetism

Mikael Rechtsman, PhD
E-Quad, B205
Monday, January 27, 2014 - 4:30pm

In this talk I will present two examples in which ‘fictitious fields’ can lead to surprising effects in photonics that would be difficult (if not impossible) to achieve with real fields.
First, I will present the first observation of topological protection in optics - specifically, a photonic Floquet topological insulator.  Topological insulators (TIs) are solid-state materials that are insulators in the bulk, but conduct electricity along their surfaces - and are intrinsically robust to disorder.  In particular, when a surface electron in a TI encounters a defect, it simply goes around it without scattering, always exhibiting – quite strikingly – perfect transmission. The structure is an array of coupled helical waveguides (the helicity generates a fictitious circularly-polarized electric field that leads to the TI behavior), and light propagating through it is ‘topologically protected’ from scattering.  I will discuss how topological protection has the capacity to endow photonic devices with the quantum Hall-like robustness.
Second, I will demonstrate artificial magnetic fields (‘pseudomagnetism’) in photonic structures.  In nearly any material, magnetic response is negligible in the optical regime.  Here I will show experimental results demonstrating how inhomogeneously straining the structure is equivalent to applying an extremely strong magnetic field. The effect of the aperiodic strain is to collapse the spatial photonic spectrum into photonic Landau levels – spectral regions of extremely high density-of-states.  High photonic density-of-states means strong light-matter interaction, which can enable large-area lasing, chemical sensing, and quantum dot emission, among other applications.
Mikael Rechtsman is an Azrieli Postdoctoral Fellow at the Technion (Israel Institute of Technology) in Prof. Mordechai Segev’s group.  He received his S.B. degree from M.I.T. in 2003 and his Ph.D. from Princeton in 2008, both in physics.  His research centers on complex structures and emergent physical phenomena in photonics, in service of novel or dramatically improved photonic devices.   Recent accomplishments include the first observation of optical topological insulators and strain-induced optical pseudomagnetism in photonic structures.  He is the recipient of the NSERC graduate award, the Fine fellowship and the Azrieli fellowship.  Dr. Rechtsman’s articles have been published in various journals, including Optics Letters, Physical Review Letters, Nature Photonics, Nature Materials, Nature and Science.