A complex-valued refractive index includes two parts: real and imaginary parts. The real part stands for refractive, while the imaginary one handles the attenuation.
Transparent window of the Silicon (1.2-6.5um)
n(Si) = 3.5; n (SiO2) = 1.45.
Low detection capability
Si pros:
- Transparent in 1.3-1.6 um wavelength region
- CMOS compatibility
- Low cost
- High index -> small device footprint
Cons:
- No electro-optical effect: inefficient modulation
- Low absorption in 1.3-1.6 um region: no detection
- High index: bad for efficient coupling
- Indirect bandgap: inefficient light emission