Abstract
Optical couplers play an integral role in coupling of the guided mode from an optical fiber into a Photonic Integrated Circuit (PIC). Apart from the edge couplers, grating couplers are the most extensively used optical I/O's. Grating couplers have limited application owing to their polarization selectivity and a small coupling 3-dB bandwidth of approx. 70 nm. By engineering the average effective index of the grating coupler using sub-wavelength gratings, we increased the coupling bandwidth while introducing polarization insensitivity. With the a uniform sub-wavelength grating coupler designed in this thesis, we attained 3-dB bandwidth of 105nm and 121 nm for the TE and TM polarizations, respectively. The proposed device attains a simulated coupling efficiency of -4.88dB for both TE and TM polarization at 1550 nm, resulting in zero polarization dependent loss. To the best of our knowledge, the proposed SWGC offers the best reported performance in bandwidth and polarization sensitivity.
Highlights
1.1 Silicon PhotonicsSilicon Photonics has attracted tremendous research interest throughout the past decade
The polarization dependent loss (PDL) at 1.55 μm are reduced to 0.87 dB at 1.55 μm, with maximum coupling efficiencies of −2.95 dB and −3.82 dB for Transverse Electric (TE) and Transverse Magnetic (TM), respectively
A 1-dB coupling bandwidth of 45 nm and 37.5 nm were obtained for TE and TM, respectively
Summary
1.1 Silicon PhotonicsSilicon Photonics has attracted tremendous research interest throughout the past decade. One of the key challenges is efficient coupling of light from a fiber into and out of photonic integrated circuits (PICs). The DWDM fiber may support up to as high as 128 channels, increasing the minimum bandwidth limit to almost 100 nm [2] and resulting in an overall higher data rate. It is highly desirable to employ an optical coupler that is efficient as well as broadband. For broadband application we require at least 100 nm bandwidth at a central operating wavelength of 1550 nm, thereby invading parts of the S-band (1460–1530 nm) and the L-band (1565–1625 nm). An optical coupler that is both polarization flexible and broadband in operation is highly desirable for high-data rate telecom applications. A brief overview of the most popular fiberwaveguide coupling techniques and their characteristic properties is given
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