Yann G. Boucher

Low threshold coherent emission at 1.5 µm is achieved using Er³⁺-doped dielectric 1D microcavities fabricated with a Radio Frequency-sputtering technique. The microcavities are composed of a half-wavelength Er³⁺-doped SiO₂ active layer inserted between two Bragg reflectors consisting of ten, five, and seven pairs of SiO₂/TiO₂ layers, also doped with Er³⁺ ions. The morphology of the structure is inspected using scanning electron microscopy. Transmission measurements show the third and first order cavity resonance at 530 nm and 1.5 µm, respectively. The photoluminescence measurements are obtained using the optical excitation at the third order cavity resonance using a 514.5 nm Ar⁺ laser or Xe excitation lamp at 514.5 nm, with an excitation angle of 30°. The full width at half maximum of the emission peak at 1535 nm decreased with the pump power until the spectral resolution of the detection system was 2.7 nm. Moreover, the emission intensity presents a non-linear behavior with the pump power and a threshold at about 4 µW.

We consider a system of two coupled magnetooptical single-mode slab waveguides separated by an isotropic dielectric spacer. In the transverse magneto-optical configuration, the TE/TM states of polarization can be handled separately. The even/odd supermodes are derived in much the same way as in similar non-magnetic coupled systems; perfect phase-matching ensures a total transfer of energy from one waveguide to the other. The coupling constant can be related to the difference between the propagation constants of the even (fast) and odd (slow) supermodes. Besides, while reversing the magnetization in one of the two waveguides does not affect the phase-matching, it does change the coupling mechanism in a subtle way, thus allowing a magnetic control of the supermodes and of the polarization-dependent coupling efficiency.

This work focuses on the fabrication processes and photonic assessment of SiO₂-SnO₂:Er³⁺ monoliths. To obtain the crack-free and densified system, the sol-gel derived synthesis protocols and heat-treatment processes were optimized. The absorption measurements were employed to assess the effect of the heat-treatment on the samples and specially to estimate the –OH content. The XRD patterns were used to investigate the crystallization as well as the structure of the monoliths. The emission spectra, performed at different excitation wavelengths, evidence the presence of Er³⁺ in the SnO₂ nanocrystals and the energy transfer from SnO₂ to the rare earth ions. In addition, the efficient role of SnO₂ nanocrystals as Er³⁺ sensitizers are also experimentally confirmed in this system.

All Er³⁺ doped dielectric 1-D microcavity are fabricated by RF sputtering technique. The microcavity is composed of half wave Er³⁺ doped SiO₂ active layer inserted, between two Bragg reflectors consisting of seven pairs of SiO₂/TiO₂ layers also doped with Er³⁺ ions. The morphology of the structure is inspected with scanning electron microscopy. Transmission measurements show the third and first order cavity resonance at 530 nm and 1535 nm, respectively. The photoluminescence measurements were obtained by optically exciting at the third order cavity resonance using 514.5 nm Ar⁺ laser with an excitation angle of 30°. The Full Width at Half Maximum of the emission peak at 1535 nm decrease with the pump power until the spectral resolution of the detection system of 2.3 nm. Moreover, the emission intensity presents a non-linear behavior with the pump power and a threshold at about 4 μW.

We investigate theoretically, in the frame of coupled-mode theory, a parity-time symmetric directional coupler inserted into a symmetric resonant cavity, all ports being terminated by four identical lossless reflectors. The scattering parameters are expressed under analytic closed forms in several equivalent bases, underlining the fact that PT Symmetry can be thought of as mode coupling between the old Eigenmodes of the passive structure. We also derive the oscillation threshold of such a complex cavity, and comment upon this apparent paradox: as a matter of fact, a laser effect is not necessarily expected from a device with more losses than gain.

EPJ Web of Conferences, open-access proceedings in physics and astronomy

EPJ Web of Conferences, open-access proceedings in physics and astronomy