Broadband Optical Active Waveguides Written by Femtosecond Laser Pulses in Lithium Fluoride

Abstract

Broadband waveguiding through light-emitting strips directly written in a blank lithium fluoride crystal with a femtosecond laser is reported. Light guiding was observed at several optical wavelengths, from blue, 458 nm, to near-infrared, at 1550 nm. Visible photoluminescence spectra of the optically active F2 and F + 3 color centers produced by the fs laser writing process were measured. The wavelength-dependent refractive index increase was estimated to be in the order of 10 −3 -10 −4 in the visible and near-infrared spectral intervals, which is consistent with the stable formation of point defects in LiF.

Advanced characterization of color centers lightemitting waveguides induced in lithium fluoride crystals by femtosecond laser

“…The observation of the near-field profiles (NFP) at several wavelengths in the visible and near-infrared spectral intervals demonstrates that these waveguides were supporting a few guided modes. Even the blue argon laser light at 457.9run can be confined in these buried CC waveguide [6,8], as it is shown in Fig.2. Fig.3 shows similar measurements obtained on another waveguide at the near-infrared wavelengths (C-band ASE fiber source at 1550 run).…”

“…Fig.3 shows similar measurements obtained on another waveguide at the near-infrared wavelengths (C-band ASE fiber source at 1550 run). A regularly shaped profile of the guided light is clearly recognizable [6,8].…”

Effects of Birefringence on the Electromagnetic Guidance of Structures Produced by Femtosecond Laser

“…Adequate modifications in the parameters of the writing technique allowed the fabrication of Bragg waveguides in LiF crystals with femtosecond laser pulses. Several works focused on the study of the Bragg waveguide dimensions and the associated refractive index variations [25], the measurement of light propagation parameters in the range from 458 nm to 1550 nm [26]- [27] and the production of LiF crystal waveguide lasers [24], [33].…”

Dimensions and refractive index estimates of deeply buried optical waveguides in Lithium Fluoride

“…Recently, the writing of fs induced waveguides in Lithium Fluoride and several of their characteristics were reported [15,16], the observed transversal cross section is also not regular, as can be seen in Fig. 1, which shows fluorescence confocal laser microscopy images of the transverse plane from (a) the side face and (b to d) from the bulk of a lithium fluoride crystal, where several optical waveguides were recorded by a femtosecond pulsed laser.…”

“…1, which shows fluorescence confocal laser microscopy images of the transverse plane from (a) the side face and (b to d) from the bulk of a lithium fluoride crystal, where several optical waveguides were recorded by a femtosecond pulsed laser. The visible fluorescence is due to the local formation of laser-active aggregate color-centers in the LiF matrix [15,16]. Figure 1(e) shows the NFP measured from one waveguide when using an ASE source, with central wavelength at 1550 nm, to launch light into the waveguide.…”