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. 2019 Sep 10;9:12988. doi: 10.1038/s41598-019-49324-5

Table 1.

Measured coupling efficiencies at a wavelength of 1550 nm.

Number of layers (N) Coupling efficiency (dB)
Apodized Unapodized
0 −4.9 −5.6
18 −2.07 −2.6
20 −1.95 −2.4