Allowing systems to change in time can “enhance” them with various properties – wave propagation is no longer bound to be reciprocal, effective gain and loss of power can be applied, etc. Applying both space and time modulation can create intriguing phenomena. An interesting question is whether or not a “moving” time of modulation, such as a traveling wave one, is equivalent to actual motion. Also, can space-time modulation induce in system properties that it does not have when static?
Adding time modulation to sensing systems may allow us to enhance performance and sensitivity. We study how this effect can improve direction-of-arrival detection in a deep subwavelength scenario.
Characterizing heterogeneous tissue with open-coax measurements
Open coax dielectric measurement is a common technique to characterize the dielectric properties of a sample. It is simple, cheap, noninvasive, and nondestructive. On the other hand, it's deeply quasi-static nature only provides an "averaged" look into the sample, with extremely low penetration depth due to large impedance mismatch.
By extensing existing theory, we study models and techniques that may allow us to extract more intricate information - the properties of a scatterer embedded in the media for instance, using the same technique.
In “standard” systems, waves (electromagnetic, acoustic) propagate reciprocally – if we exchange the locations of the source and the measurement probe, the measured field will not change. However, when we violate the conditions for this, for example by applying a static magnetic field bias or motion to our system, this doesn’t hold anymore, and nonreciprocal propagation is made possible. The most extreme version of it is the “one-way” or “sector way” propagation, where waves can only propagate into certain directions in space, even though they are excited by a source that does not make this directional distinction.
Wave interaction with complex particles and structures
Light interaction with complex structures, such as particle arrays that have a complex unit-cell structure or respond to both electric and magnetic fields, or chiral and anisotropic structures, allows for interesting wave propagation effects to occur such as:
Nonreciprocal and one-way wave propagation under specific requirements, that can be characterized using general group theory considerations.
Asymmetric wave propagation that can be leveraged to obtain a completely unidirectional propagation when combined with the right excitation scheme without the use of a magnetic field, time modulation, or nonlinear media.
Extreme dispersion features such as hyperbolic-like features in cylindrical structures.
And many more…