Publisher Summary A refractive index can be increased by ion implantation by changes in density and structure, by the addition of high-polarizability impurity ions, by a reduction of the plasma effect that increases the index and that is most important in the wavelength region far from the energy gap, and by absorption changing in the index in the region of the gap, that is, via the Kramers–Kronig relation. This chapter discusses the optical properties of implanted semiconductors, electrooptic components formed by ion implantation, general principles that determine most luminescent systems, effects of implantation temperature, luminescence centers in LiF-Mg-Ti radiation dosimeters, and use of line spectra in defect studies. In the LiF system, the luminescence bands are broad, and if alternative versions of the same complex exist, they cannot be resolved from the spectra. The addition, by implantation, of ions with incomplete inner electron shells opens up new possibilities as the lattice distortions of the free-ion energy levels are strongly perturbed by the defects in the neighborhood of the ion.

Optical Effects of Ion Implantation

Integrated optics and new wave phenomena in optical waveguides

A review is given on the foundations and applications of non-Hermitian classical and quantum physics. First, key theorems and central concepts in non-Hermitian linear algebra, including Jordan normal form, biorthogonality, exceptional points, pseudo-Hermiticity and parity-time symmetry, are delineated in a pedagogical and mathematically coherent manner. Building on these, we provide an overview of how diverse classical systems, ranging from photonics, mechanics, electrical circuits, acoustics to active matter, can be used to simulate non-Hermitian wave physics. In particular, we discuss rich and unique phenomena found therein, such as unidirectional invisibility, enhanced sensitivity, topological energy transfer, coherent perfect absorption, single-mode lasing, and robust biological transport. We then explain in detail how non-Hermitian operators emerge as an effective description of open quantum systems on the basis of the Feshbach projection approach and the quantum trajectory approach. We discuss their applications to physical systems relevant to a variety of fields, including atomic, molecular and optical physics, mesoscopic physics, and nuclear physics with emphasis on prominent phenomena/subjects in quantum regimes, such as quantum resonances, superradiance, continuous quantum Zeno effect, quantum critical phenomena, Dirac spectra in quantum chromodynamics, and nonunitary conformal field theories. Finally, we introduce the notion of band topology in complex spectra of non-Hermitian systems and present their classifications by providing the proof, firstly given by this review in a complete manner, as well as a number of instructive examples. Other topics related to non-Hermitian physics, including nonreciprocal transport, speed limits, nonunitary quantum walk, are also reviewed.

Non-Hermitian Physics

A generalized analysis of wave propagation in periodic layered media is applied to the special case of optical surface waves. These waves, confined to the interface between a periodic layered medium and a homogeneous medium, are formally analogous to electronic surface states in crystals. Single‐mode surface‐wave propagation along the surface of a GaAs‐AlGaAs multilayer stack (grown by molecular‐beam epitaxy) has been observed experimentally.

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Optical surface waves in periodic layered media

This paper deals with the theory and device applications of periodic thin-film waveguides. Topics treated include mode solutions, optical filters, distributed feedback lasers (DFB), distributed Bragg reflector (DBR) lasers, grating couplers, and phase matching in nonlinear interactions.

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Periodic structures for integrated optics

We have produced optical waveguides in n‐type GaAs by implantation with 300‐keV protons. The guiding is shown to be due to the elimination of charge carriers from the implanted region. Annealing of the waveguide leads to very large reductions in the 1.15‐μ guided‐wave absorption.

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Optical waveguiding in proton-implanted GaAs

Thin film integrated optics components such as light guides, modulators, directional couplers, and polarizers demand high quality edge smoothness and high resolution pattern formation in dimensions down to submicrometer size. Fabrication techniques combining holographic and scanning electron beam lithography with ion beam micromachining have produced planar phase gratings with intervals as small as 2800 A, guiding channel couplers in GaAs, and also wire- grid polarizers for 10.6-µm radiation.

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Ion beam micromachining of integrated optics components.

Defect levels introduced by implanting GaAs with high-energy protons give rise to optical absorption at wavelengths greater than that of the normal absorption edge at 0.9 µ. Optical waveguide detectors may be fabricated by taking advantage of this absorption mechanism in the presence of a Schottky barrier depletion layer. Detector response times less than 200 ns and external quantum efficiencies of 16% have been observed.

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H. Stoll

Papers

Optical waveguiding in proton-implanted GaAs

Ion beam micromachining of integrated optics components.

Proton-implanted optical waveguide detectors in GaAs