Photonic Topological Insulators

Shouyuan Huang, Ph.D. Student

Department of Mechanical Engineering and Birck Nanotechnology Center, Purdue University

What is topological insulator? TKNN understanding

Hasan, Kane Rev Mod Phys 2010

What is topological insulator?

• Quantum Spin Hall Effect/2-D Topological Insulator • Spin-orbit coupling • Berry Curvature

• Spin-momentum locking

• Back-scattering free

• Magnetic monopoles/Majorana Fermions

• Dissipationless electronics/fault-tolerant quantum computers

Why photonic topological insulators

• Scientific interest: Bosonic analog

• Non-reflective / one-way waveguide

• Disorder-immune boundary states

Lu et al. nphys 2016

Patton, Industry Stategy Symposium, 2013

Photonic QHE • 2-D Topological states w/ magnetic field.

Raghu, Haldane PRL 2008

Wang et. al. PRL 2008 Wang et. al. Nature 2009 (Soljacic group)

Photonic QHE • 2-D Topological states w/ magnetic field.

• Control of Chern number

Skirlo et al PRL 2014 Skirlo et al PRL 2015 (Soljacic group)

Pushing towards Optical Frequences

Khanikaev et al. nmat 2012 (Shvets group)

Pushing towards Optical Frequences • Thinking 2: Floquet theory with pseudo-time

“photonic graphene”

Gu et al. PRL 2011 Mak et al. Science 2014

Plotnik nmat 2013

Electronic:

Photonic:

Pushing towards Optical Frequences • Thinking 2: Floquet theory with pseudo-time

Rechtsman et al. Nature 2013 (Segev group)

Pushing towards Optical Frequences • Thinking 2: Floquet theory with pseudo-time

Pushing towards Optical Frequences • Thinking 2: Floquet theory with pseudo-time

“photonic graphene”

Gu et al. PRL 2011 Mak et al. Science 2014

Electronic:

Photonic:

Ma Shvets CLEO 2016 Pseudo-time design?

3-D PTI: existence of Weyl point • 3-D version of Dirac point

Double-gyroid

“photonic ARPES” Lu et al. nphys 2013; Lu et al Science 2014. (Soljacic’s group)

Self-assembly?

3-D PTI: existence of Weyl point • 3-D version of Dirac point

Lu et al. nphys 2016. (Soljacic’s group)

Symmetry protection

3-D PTI: existence of Weyl point • 3-D version of Dirac point

Noh et al. nphys 2017.

Phase differ by ½ cycle

Conclusion • Potential applications:

• Defect-immune in nanophotonic system. • One-way waveguide/photonic fibers • Large-volume/area single-mode sensing/lasing • Platform for new science

• Possible future works: • Optical wavelength one-way waveguide • Easy-realizable space groups for Weyl point