A high efficiency broadband grating coupler for Silicon-OnInsulator waveguides was designed. The grating coupler is defined by locally adding a poly-Silicon layer on top of the existing waveguide layer structure prior to grating etching. Adding this poly-Silicon layer reshapes the grating structure which changes its diffraction properties. Coupling efficiencies as high as 78% at a wavelength of 1.55μm are calculated and the optical 3dB bandwidth of the device is about 85nm. The device layout is compatible with standard CMOS technology processing.
Expanding far beyond traditional applications in optical interconnects at telecommunications wavelengths, the silicon nanophotonic integrated circuit platform has recently proven its merits for working with mid-infrared (mid-IR) optical signals in the 2-8 μm range. Silicon's broadband transparency 1, 2 , strong optical confinement, and potential for co-integration with CMOS electronics 3 are but a few of the many characteristics making the silicon platform ideal for development of high-performance, densely-integrated mid-IR optical systems. These systems are capable of addressing applications including industrial process and environmental monitoring 4 , threat detection 5 , medical diagnostics 6 , and free-space communication 7 . Rapid progress has led to the demonstration of various silicon components designed for the on-chip processing of mid-IR Mid-IR to telecom band spectral translation in silicon wires can be accomplished using efficient FWM with discrete band phase-matching 24, 25 . In this process, the pump is placed away from the zero dispersion wavelength, and higher-order waveguide dispersion is used to phase-2 match a discrete pair of bands at spectrally distant frequencies, located symmetrically on either side of the pump. Discrete band phase-matching can be achieved in a waveguide with anomalous additional discrete MI bands with much larger detuning from the pump appear at 1620 nm and 2440 nm, and serve as direct evidence of higher-order phase-matching. The absolute power of the MI band at 2440 nm appears lower than that of the MI band at 1620 nm, due to a 1.8 dB asymmetry expected from the Manley-Rowe power division relations, as well as from ~3-4 dB larger losses in the output fibre optical collection path at longer wavelengths.The visibility of the MI bands, associated with the parametric amplification of background noise, suggests that the pumped silicon nanophotonic wire should exhibit significant parametric gain as well as a large conversion efficiency when probed by input signals at these wavelengths. Figure 1d illustrates the output spectrum in one such case, when the long-wavelength discrete MI band is probed (Signal ON) by a low-power (P sig < 35 μW) continuous-wave mid-IR signal at 2440 nm. When the signal is tuned into resonance with this spectral band, it experiences strong parametric amplification through degenerate FWM (evidenced by the appearance of the large spectral pedestal), and is simultaneously up-converted to a prominent telecom band idler at 1620nm. This large spectral translation over more than 62 THz illustrates that the higher-order dispersion design methodology applied here may be used to efficiently convert optical information on a mid-IR carrier into the telecom band, where it can be detected and processed using un-cooled, high-speed, high-sensitivity III-V and group-IV semiconductor detector technologies. 4By recording transmission spectra for a range of signal wavelengths near 2440 nm and 1620 nm, the wavelength dependence of spectral translation efficiency and par...
Abstract:Laser emission from an InP/InGaAsP thin film epitaxial layer bonded to a Silicon-on-Insulator waveguide circuit was observed. Adhesive bonding using divinyl-tetramethyldisiloxane-benzocyclobutene (DVS-BCB) was used to integrate the InP/InGaAsP epitaxial layers onto the waveguide circuit. Light is coupled from the laser diode into an underlying waveguide using an adiabatic inverted taper approach. 0.9mW optical power was coupled into the SOI waveguide using a 500μm long laser. Besides for use as a laser diode, the same type of devices can be used as a photodetector. 50μm long devices obtained a responsivity of 0.23A/W. 2654 -2656 (1996). 8. Z. Mi, J. Yang, P. Bhattacharya, and D. L. Huffaker, "Self-organised quantum dots as dislocation filters: the case of GaAs-based lasers on silicon," Electron. Lett. 42, 121-122 (2006).
A surface-illuminated photoconductive detector based on Ge 0.9 Sn 0.1 quantum wells with Ge barriers grown on a silicon substrate is demonstrated. Photodetection up to 2.2µm is achieved with a responsivity of 0.1 A/W for 5V bias. The spectral absorption characteristics are analyzed as a function of the GeSn/Ge heterostructure parameters. This work demonstrates that GeSn/Ge heterostructures can be used to developed SOI waveguide integrated photodetectors for short-wave infrared applications. 2012 Optical Society of America References and links1. J. Menendez and J. Kouvetakis "Type-I Ge/Ge1−x−ySixSny strained-layer hetero-structures with a direct Ge Bandgap", Applied Physics Letters, 85(7), 1175-1177 (2004). 2. G. Sun, R. A. Soref, H. H. Cheng, "Design of a Si-based lattice-matched room temperature GeSn/GeSiSn multiquantum-well mid-infrared laser diode", Optics Express 18(19), 19957-19965 (2010). 39(3), 1871-1883, (1989). 14. M. Krijn, "Heterojunction band offsets and effective masses in III-V quaternary alloys" Semiconductor Science and Technology, 6(1), 27-31 (1991
High efficiency diffractive grating structures to interface a single mode optical fiber and a nanophotonic integrated circuit fabricated on silicon-on-insulator are presented. The diffractive grating structures are designed to be inherently very directional by adding a silicon overlay before grating definition. 55% coupling efficiency at a wavelength of 1.53 m is experimentally demonstrated on devices fabricated using standard complementary metal-oxide semiconductor technology. By optimizing the grating parameters, we theoretically show that 80% grating coupling efficiency can be obtained for a uniform grating structure.High refractive index contrast optical waveguide structures hold promise for large scale integration of optical functions on a single substrate. This is due to the fact that the high refractive index contrast allows realizing wavelengthscale optical components ͑e.g., photonic crystal cavities, 1 ring resonators, 2 modulators, 3 etc.͒ which can be interconnected by nanophotonic integrated waveguides. Silicon-oninsulator ͑SOI͒ is emerging as the dominant platform for this integration because the refractive index contrast between the silicon waveguide layer ͑n Si = 3.45 at a wavelength of 1.55 m͒ and the underlying buried oxide layer ͑n SiO 2 = 1.45͒ is very high. Moreover, these nanophotonic structures can be defined using state-of-the-art complementary metaloxide semiconductor ͑CMOS͒ technology. 4 While the high omnidirectional refractive index contrast allows realizing wavelength-scale optical functions, the interfacing between a nanophotonic waveguide and a standard single mode fiber is far from trivial due to the large mismatch in dimensions between the 9 m diameter core of a single mode fiber and the cross section of an integrated high index contrast waveguide, which is typically 0.1 m 2 for a single mode waveguide at telecommunication wavelengths. In this paper, we present the use of a diffractive grating structure defined in the waveguide layer to efficiently interface with a single mode optical fiber. The operation principle of the device is based on the Bragg diffraction from the grating. The optical fiber is slightly tilted off vertically in order to avoid second order Bragg reflection into the waveguide. 4 While the optical coupling properties of one-dimensional grating structures are very polarization dependent, it was shown that a twodimensional grating coupling approach allows tackling the issue of the polarization dependent loss of high index contrast photonic integrated circuits by applying a polarization diversity configuration, 5 without the need of integrating a polarization splitter and rotator on the photonic integrated circuit. 6The fiber-to-waveguide coupling efficiency is determined by the directionality of the grating, being the ratio of the power that is diffracted upward ͑P up ͒ to the total diffracted power ͑P up + P do ͒, as shown in Fig.
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