Coherent perfect absorbers: time-reversed lasers

Area of Science:

• Optics and Photonics
• Materials Science
• Quantum Mechanics

Background:

• Materials typically reflect or transmit light, with absorption being a loss mechanism.
• Controlling light absorption precisely is crucial for advanced optical devices.
• Lasing at threshold involves stimulated emission and constructive interference.

Purpose of the Study:

• To demonstrate a method for achieving perfect absorption in arbitrary bodies.
• To investigate the underlying physics of coherent perfect absorption.
• To explore potential applications of this phenomenon in optical technologies.

Main Methods:

• Introducing a precise amount of dissipation into a material.
• Illuminating the material with coherent monochromatic light.
• Utilizing a simple silicon (Si) slab geometry for experimental demonstration.
• Analyzing the effect through the S matrix and wave vector properties.

Main Results:

• Achieved perfect absorption at discrete frequencies in a Si slab.
• Demonstrated that the effect arises from the interplay of optical absorption and wave interference.
• Showed this phenomenon is the time-reversed analog of lasing at threshold.

Conclusions:

• Coherent perfect absorbers can be engineered by combining absorption and interference.
• These absorbers function as linear, absorptive interferometers.
• Potential applications include highly sensitive optical detectors, transducers, and switches.