Figure 2
From: Holographic planar lightwave circuit for on-chip spectroscopy
DPH spectrometer fabrication details. (a) Light entering the DPH goes through a smooth variation of the refractive index to avoid formation of spurious harmonics; optical microscope photo of the DPH (left), and SEM top-view of a DPH section showing the digitalized grooves embedded into the Si3N4 waveguide core (right). (b) SEM 30° tilted view of one planar hologram and the projecting RWG (center); the figure shows the atomic force microscopy measurements of the planar hologram, etched 18 nm deep into the waveguide core (right), and the single mode RWG etched through the full Si3N4 film (left). DPH, digital planar hologram; RWG, ridge waveguide; SEM, scanning electron microscopy.
