Bound states in the continuum:
the (un)known state with innovative applications

Prof. Pedro Pereira
(IF-UERJ)

Resumo:

Usually, in introductory quantum mechanics courses, we use the finite quantum well to study the possible quantum states, namely, bound states within the quantum well, and extended and resonant states in the continuum. In addition to these states, the bound state in the continuum is one less explored in introductory courses, even though it was proposed at the beginning of quantum mechanics. In 1929, von Neumann and Wigner noted that certain infinite periodic potentials gave rise to states with localized wavefunction embedded in the continuum. These periodic potentials are not found in nature, making the bound state in the continuum just a “toy model” of the Schrödinger equation at that time.

The advancement of epitaxial growth techniques of semiconductor heterostructures allowed such periodic potentials to be fabricated in the laboratory. The bound state in the continuum was observed in 1992 in semiconductor superlattices, and was fundamental for the progress of the quantum cascade laser. Although the bound state in the continuum has been proposed in quantum systems, it is a universal feature of wave systems (acoustic, aquatic, optical, and photonic). In particular, they are of great interest for creating optical cavities with infinite quality factor.

The laboratory of semiconductors and optoelectronic devices (LSDopto) has been exploring these states for the development of infrared photodetectors with characteristics not obtained with traditional quantum well-infrared photodetectors. In this talk, I will present the fundamental concepts of bound states in the continuum in semiconductor superlattices, and, in particular, how they are being used in the development of innovative photodetectors by our group.

Departamento de Física dos Sólidos
Instituto de Física UFRJ