UV Edge Coupling into AlN Waveguides — ICD, University of Twente

Source

Wavelength λ

Objective NA

Polarisation

TE (E in plane) TM (E vertical)

Waveguide

AlN thickness t

Width W

Etch depth

SiO₂ buffer

SiO₂ over-cladding instead of air

Waveguide length L

Alignment

Lateral offset Δx

Vertical offset Δy

Defocus / gap Δz

Beam tilt θ

Roughness & loss

Facet roughness σ_f

Sidewall roughness σ_sw

Correlation length L_c

Bulk/material loss

substrate leakage into Si (tunnelling through the buffer)

Presets

Operating point

From the objective to the guided mode

incident beam guided mode reflected / scattered radiated into substrate

Loss budget

Vertical slab mode (air / AlN / SiO₂ / Si)

mode field E |E|² focused beam

Effective index and cut-off versus thickness / width

Coupling efficiency versus transverse alignment

Alignment cuts and 1 dB tolerances

lateral Δx vertical Δy defocus Δz tilt θ

Free-space edge coupling into thin AlN waveguides at 360 nm

Source

Polarisation

Waveguide

Alignment

Roughness & loss

Presets

Operating point

From the objective to the guided mode

Loss budget

Vertical slab mode (air / AlN / SiO₂ / Si)

Effective index and cut-off versus thickness / width

Coupling efficiency versus transverse alignment

Alignment cuts and 1 dB tolerances

Coupling versus spot size — where the optimum sits

Wavelength dependence

Facet reflection and return loss

Fabry–Pérot fringes from the two facets

Propagation loss: leakage, scattering, material

Total insertion loss versus length, and the λ⁻³ problem