  We propose a method to break the chiral symmetry of light in traveling wave
resonators by coupling the optical modes to a lossy channel. Through the
engineered dissipation, an indirect dissipative coupling between two oppositely
propagating modes can be realized. Combining with reactive coupling, it can
break the chiral symmetry of the resonator, allowing light propagating only in
one direction. The chiral symmetry breaking is numerically verified by the
simulation of an electromagnetic field in a micro-ring cavity, with proper
refractive index distributions. This work provokes us to emphasize the
dissipation engineering in photonics, and the generalized idea can also be
applied to other systems.
