Projected demands in information bandwidth have resulted in a paradigm shift from electrical to optical interconnects. Switches, modulators and wavelength converters have all been demonstrated on complementary metal-oxide semiconductor compatible platforms, and are important for all optical signal and information processing. Similarly, pulse compression is crucial for creating short pulses necessary for key applications in high-capacity communications, imaging and spectroscopy. In this study, we report the first demonstration of a chip-scale, nanophotonic pulse compressor on silicon, operating by nonlinear spectral broadening from self-phase modulation in a nanowire waveguide, followed by temporal compression with an integrated dispersive element. Using a low input peak power of 10 W, we achieve compression factors as high as 7 for 7 ps pulses. This compact and efficient device will enable ultrashort pulse sources to be integrated with systems level photonic circuits necessary for future optoelectronic networks.
Fundamental to pulse compression is the acquisition of nonlinear phase through self-phase modulation20. The third order susceptibility of the host material results in an intensity-dependent phase shift, which leads to the creation of new optical frequencies. When appropriately combined with optical dispersion, pulse compression results. This dispersion may be distributed over the length of the nonlinear medium, leading to solitonic compression, or may be localized at the output of the nonlinear medium using a highly dispersive element. We recently reported the theory and operation of such a dispersive element in silicon21,22, thus opening up vast prospects for all-optical on-chip functionalities for which dispersion is a key requirement. Such an element has been absent in the on-chip nanophotonics toolkit, and to date, most integrated optics applications requiring dispersive elements required heterogeneous integration with fibre-based components, resulting in less compact systems.
In this study, we demonstrate for the first time, a chip scale, compact, monolithically integrated nonlinear pulse compressor operating via self-phase modulation in a silicon nanowire waveguide, followed by re-phasing with an integrated dispersive element. We report optimal compression factors as high as 7 at a low input peak power of 10 W. The requisite large acquired nonlinear phase for high compression factors is obtained at low input peak powers, owing to the large third order Kerr nonlinearity in silicon, high modal confinement in the carefully designed nanowire waveguide and, consequently, large nonlinear parameter, γ20,23,24,25,26.
Integrated photonic circuits are one of the most promising platforms for large-scale photonic quantum information systems due to their small physical size and stable interferometers with near-perfect lateral-mode overlaps. Since many quantum information protocols are based on qubits defined by the polarization of photons, we must develop integrated building blocks to generate, manipulate and measure the polarization-encoded quantum state on a chip. The generation unit is particularly important. Here we show the first integrated polarization-entangled photon pair source on a chip. We have implemented the source as a simple and stable silicon-on-insulator photonic circuit that generates an entangled state with 91 ± 2% fidelity. The source is equipped with versatile interfaces for silica-on-silicon or other types of waveguide platforms that accommodate the polarization manipulation and projection devices as well as pump light sources. Therefore, we are ready for the full-scale implementation of photonic quantum information systems on a chip.
Integrated quantum photonics, which exploits miniature physical size and stable interferometers with near-perfect lateral-mode overlaps of integrated lightwave circuits, constitutes the future for realizing a scalable photonic QIP system on a chip10,11. Recent experiments on integrated quantum photonics have utilized path-encoded quantum states of photons3,10,11,12,13. However, polarization encoding allows us to implement the systems without the need for path duplication and thus provides the simplest and most compact circuitry. It will also allow us to implement a wealth of the QIP protocols. To accomplish such polarization-encoded QIP systems, it is essential to develop integrated subsystems to generate, manipulate and measure polarization-encoded quantum states on a single chip. Although the integration of optical circuits makes the handling of polarization states slightly more challenging, Bonneau et al.14 and Sansoni et al.15,16 recently demonstrated the manipulation and projection of quantum states on a chip by using a lithium niobate (LN) waveguide modulator and low-birefringent silica waveguides, respectively. An integrated single-photon detector on a silicon chip has already been demonstrated17. Therefore the only remaining task is to implement a polarization-entangled photon pair source18,19. The source is an essential component of such polarization-encoded QIP systems as quantum gates7, on-demand single photon sources20 and scalable one-way quantum computation8. Furthermore, path-polarization hybrid integration is also useful as a simulation tool for physical quantum systems4.
In this work, we experimentally demonstrate the first polarization entanglement source that is fully integrated as a silicon photonic circuit. We compensate for the polarization-dependent walk-off simply by designing the device to be symmetric as regards the polarization degree with respect to the device midpoint, with the help of a polarization manipulation technology for telecommunication devices. The symmetric structure is also useful for the stable generation of maximally entangled states, in the presence of waveguide loss. Our source is not based on a post-selection scheme22, so creates no spurious photons that limit the application of the source21. Furthermore, the device is equipped with a spot-size converter (SSC), which is an interface with silica or other types of quantum waveguide circuits for a fully integrated QIP system on a chip.
As regards the degree of entanglement, we estimate the fully entangled fraction , where the maximum is taken over all maximally entangled states , i.e., over , where Us and Ui are unitary transformations on the signal and idler modes37,38. Therefore, we can create any maximally entangled state (including Bell states) from a state ρ with F(ρ) = 1 by employing linear optics such as wave plates. In accordance with the procedure described in ref , we obtained F(ρref) as 0.51 ± 0.02, which is on the bound of the classical states of F(ρ) = 0.5. Thus, the single straight silicon wire waveguide created no entanglement. At the same time, for the polarization-entanglement source we obtained F(ρent) = 0.91 ± 0.02. The F(ρent) value is much greater than , implying that the generated state can violate the Clauser-Horne-Shimony-Holt inequality39. In addition, the concurrence (an alternate measure of entanglement) was obtained as 0.88 ± 0.02. Hence, we successfully generated photon pairs with a high degree of polarization entanglement from the chip.
Hi Mugsby,I'm sorry but I haven't uploaded it!I have downloaded it :) , I got this link from other source......You can see the pictures if you left click on the boxes which r there for the pictures.......I did this and got the schematics........free! whenever I tried to see the projects at silicon chip,I was asked to pay for it.....some other members also say that they can get it free but I don't know why I can't.......Repair shop guys storys????????????
Methods The ASR microchip is a 2-mm-diameter silicon-based device that containsapproximately 5000 microelectrode-tipped microphotodiodes and is powered byincident light. The right eyes of 6 patients with retinitis pigmentosa wereimplanted with the ASR microchip while the left eyes served as controls. Safetyand visual function information was collected. 2b1af7f3a8