Al4532 a

For full Numerical Aperture (NA) light injection, a continuous wave (CW) diode-pumped solid state (DPSS) laser source (λ = 473 nm, Laser Quantum Ciel 473, Laser Quantum, Stockport, UK) was collimated with a 10× beam expander and focused into the fiber with an objective lens (Olympus UIS-2 Plan N 40× NA = 0.65, Olympus Corp., Tokyo, Japan). For angle-selective light injection, light was coupled into the TFs by using the optical path depicted in Fig. 1(b). The CW beam was coupled to a patch fiber through a scanning system composed by lenses L₁ (focal length f₁ = 100 mm, Thorlabs LA1050-A, Thorlabs Inc., Newton, New Jersey, US) and L₂ (f₂ = 100 mm, AL50100-A), a galvanometric mirror GM (Sutter RESSCAN-MOM), and by lens L₃ (f₃ = 32 mm, AL4532-A). Lens L₁ focuses light on the rotation axis of the GM, while lenses L₂ and L₃ relay the beam deflected by the GM to the input facet of the fiber. Given a deflection θ_s imposed to the beam by the GM, the input angle θ into the optical fiber is given by θ = tan⁻¹(f₂ . f₃⁻¹ . tan θ_s). TFs were connected to the patch fibers of matching NA through a ferrule-to-ferrule butt coupling.