Experimental Realization of Optimal Energy Storage in Resonators Embedded in Scattering Media

Abstract

The ability to enhance light–matter interactions by increasing the energy stored in optical resonators is inherently dependent on the resonators' coupling to the incident wavefront. In practice, weak coupling may result from resonators' irregular shapes and/or the scrambling of waves in the surrounding scattering environment. Here, a blind and non‐invasive wavefront shaping technique providing optimal coupling to resonators is presented. The coherent control of the incident wavefront relies on the lengthening of delay times of waves efficiently exciting the resonator. Using a modal approach, the optimality of the proposed technique is proven and its limitations are quantified. The proposed concept is demonstrated in microwave experiments by injecting in situ optimal wavefronts that maximize the energy stored in high‐permittivity dielectric scatterers and extended leaky cavities embedded in a complex environment. The introduced framework is expected to find important applications in the enhancement of light–matter interactions in photonic materials as well as to enhance energy harvesting.

Shaping the propagation of light in complex media

“…The corresponding eigenvectors of Q ω , which determine the spatial input wavefront of these time-delay eigenstates, provide an orthogonal basis in which states are sorted according to the time delay they accumulate during the scattering process. Of particular interest in complex media are those states with the shortest and the longest possible time delays: whereas short time delays typically correspond to fast and ballistic scattering processes with a certain robustness [105][106][107] , the direct connection between the dwell time and the field intensity 104,108 makes long-lived scattering states very attractive for enhanced energy storage in a sample [108][109][110] (see Fig. 5e for an example).…”

Time Reversal Communications With Channel State Information Estimated From Impedance Modulation at the Receiver

“…The time-delay eigenstates found from a diagonalization of Q(ω) are insensitive to frequency shifts and are associated with well-defined time delays between incoming and outgoing modes given by the corresponding eigenvalues. In the context of wavefront shaping, these eigenstates make it possible to excite particle-like states in cavities [25], principal modes arriving temporally unscattered in optical fibers [26] or maximally resonant states that maximize energy storage in resonators [27], [28]. This operator may also be useful to shed light on the group delay analysis of microwave devices and the frequency sensitivity of multiport antennas, as illustrated in recent papers [29], [30].…”

On‐Demand Coherent Perfect Absorption in Complex Scattering Systems: Time Delay Divergence and Enhanced Sensitivity to Perturbations

“… hence provides maximal excitation of the selected mode. [ 22,23 ] The interpretation of as the time‐reversed output of a lasing mode (if loss mechanisms were replaced by gain mechanisms of equal strength) led to the term “anti‐laser”, [ 3,7,12 ] an analogy that should be used with caution since it neglects essential nonlinear processes in laser operation.…”