A Photonic Front End for High Resolution Blue Spectral Sensor in 45 nm SOI SiPh Process

Md Nabil Shehtab Dhrubo, Jason Case, Agung Julius, Robert F. Karlicek, Mona Mostafa Hella

Abstract: A photonic front end for a blue spectral sensor in a standard silicon photonic process is presented. The detector is capable of identifying multiple spectral peaks within the blue wavelength range (410 nm ~ 500 nm), The front end consists of grating structures with different grating pitches, followed by tapered waveguides. From the waveguide, the optical power is evanescently coupled to a silicon photodetector. To further improve the overall optical collection for the photo detector, an optical power combining network is also designed and optimized. The designs are fabricated using GlobalFoundries' 45SPCLO technology. The measurement results demonstrate the effect of varying the grating pitch in detecting different spectral peaks within the blue region, with peaks demonstrating responsivities ranging between 32~135 mAIW, depending on the grating pitch and the reverse bias.