Biomedical Engineering Reference
In-Depth Information
Fig. 7.19.
Fabrication flow starting from a silicon on insulator (SOI) wafer and
ending with the 2D PhC microcavity inserted in a silicon wire waveguide
Fig. 7.20.
Experimental setup for measuring the transmission of a 2D PhC micro-
cavity. A microscope objective is used to observe the alignment of all the components
The fabrication procedure is depicted in Fig. 7.19. After the SOI wafer
was cleaned and an oxide mask grown, negative (PMMA) and positive (FOX)
resists were used for pattern transformation. After electron-beam lithography
and resist development, reactive ion etching was performed to transfer the
pattern onto the Si slab. The ridge waveguide facets were then polished to
improve the coupling e
ciency.
Figure 7.20 illustrates the measurement setup. An HP8168F laser, tunable
from 1,440 to 1,590 nm, was used as the light source. The TE polarized laser
beam was focused onto the input tapered ridge waveguide (from 2
mto
µ
0.6
m at focus), and the
transmitted signal was measured by a photodetector. To optimize the intensity
of the TE polarized-light, a polarization controller was inserted between the
laser and the input fiber.
m) using a tapered lensed fiber (with a spot size of 2
µ
µ
7.4.2 Sensing Principle
The sensing principle is very similar to the one used in the 1D PhC biosen-
sors. In contrast to chemical sensors [37], in biological sensors, the biomolecule
