Optical characterization of low-energy electron-beam-colored LiF crystals by spectral transmittance measurements

Abstract

The complex refractive index of a LiF crystal surface layer irradiated by low-energy electrons is modified by the stable formation of color centers embedded in it. A simplified dipole-electromagnetic field interaction model has been adopted in order to estimate the dispersion curves of colored LiF from a single optical transmittance measurement. The excellent agreement with the corresponding experimental curves (obtained by means of spectrophotometry and ellipsometry) demonstrates this to be a promising approach for LiF-based optical waveguide characterization.

IR‐SNOM on lithium fluoride films with regular arrays based on colour centres

“…The optical contrast observed in the infrared SNOM images on such peculiar LiF samples could be attributed to a modification of the material optical properties associated with the high concentration of active defects, which can modify the refractive index [20] of the irradiated volume. This effect can be enhanced from the spatial periodicity of the peculiar CCs based patterns.…”

Micro and sub‐micro fabrication techniques for optically confined structures based on lithium fluoride

“…4 At the same time, the electron bombardment induces an increase in the real part of the refractive index of the irradiated area in the same wavelength interval where the emissions are located. 5 Alkali halide (AH) crystals containing colour centres (CCs) have been extensively studied for the realization of optically pumped tuneable solid-state lasers. 6 Little attention, however, has so far been devoted to AH films and to their application in the development of innovative miniaturized coherent light sources, like active waveguides and microcavities.…”

Toward control of point defects in lithium fluoride thin layers

“…Among them, simultaneous modifications of refractive index [7] and gain properties [8] have been achieved within volume of size comparable with light wavelengths. The recent developments in laser technologies, electron and particles beam methods, and novel photon sources have led to a wide range of opportunities to locally change and control the LiF optical properties at sub-micron scale, with promising applications in the field of photonics [9] and soft X-ray imaging detectors [10].…”

“…Besides the efficient defects formation, the electron bombardment of LiF by a beam of energy in the range of a few keV induces a wavelength-dependent modification of the refractive index of the irradiated layer. A dipole-field interaction model [7] was been developed to describe the modification of the complex refractive index induced by CCs formation in a host dielectric medium and to quantitatively evaluate the single contributions of different kinds of electronic defects to the overall refractive index change of the colored volume. Figure 1a shows the refractive index dispersion curve, as calculated from the transmittance best-fit parameters, together with the contributions due to different types of defects, for a LiF crystal heavily irradiated by 3 keV electrons, whose penetration is estimated around 150 nm.…”