Physical unclonable functions are the physical equivalent of one-way mathematical transformations that, upon external excitation, can generate irreversible responses. Exceeding their mathematical counterparts, their inherent physical complexity renders them resilient to cloning and reverse engineering. When these features are combined with their time-invariant and deterministic operation, the necessity to store the responses (keys) in non-volatile means can be alleviated. This pivotal feature, makes them critical components for a wide range of cryptographic-authentication applications, where sensitive data storage is restricted. In this work, a physical unclonable function based on a single optical waveguide is experimentally and numerically validated. The system’s responses consist of speckle-like images that stem from mode-mixing and scattering events of multiple guided transverse modes. The proposed configuration enables the system’s response to be simultaneously governed by multiple physical scrambling mechanisms, thus offering a radical performance enhancement in terms of physical unclonability compared to conventional optical implementations. Additional features like physical re-configurability, render our scheme suitable for demanding authentication applications.

We present a systematic experimental study of the linear and nonlinear optical properties of silicon-germanium (SiGe) waveguides, conducted on samples of varying cross-sectional dimensions and Ge concentrations. The evolution of the various optical properties for waveguide widths in the range 0.3 to 2 µm and Ge concentrations varying between 10 and 30% is considered. Finally, we comment on the comparative performance of the waveguides, when they are considered for nonlinear applications at telecommunications wavelengths.

We demonstrate broadband supercontinuum generation (SCG) in a dispersion-engineered silicongermanium waveguide. The 3-cm long waveguide is pumped by femtosecond pulses at 2.4µm and the generated supercontinuum extends from 1.45µm to 2.79µm (at the -30-dB point). The broadening is mainly driven by the generation of a dispersive wave in the 1.5-1.8µm region and soliton fission. The SCG was modelled numerically and excellent agreement with the experimental results was obtained. © Silicon (Si) photonics has witnessed rapid maturity in recent years, mainly due to its potential for high-yield, low-cost CMOS-compatible fabrication of components. At the same time, the high nonlinear refractive index of silicon (n 2 = 4.5x10 −18 m 2 /W), especially when combined with small-dimension, high refractive-index-contrast waveguide geometries that lead to tight mode confinement, makes Si photonic technologies particularly attractive for nonlinear applications. Si-based devices have already been utilized to demonstrate numerous all-optical signal processing applications. Indeed, nonlinear effects such as four-wave mixing (FWM) [1], self-phase modulation (SPM) [2] and Raman amplification [3] have been demonstrated in silicon-on-insulator (SOI) waveguides and nanowires designed for operation in the near-infrared (IR).Silicon is also an excellent candidate for mid-IR applications, due to its transparency up to 8µm and to the reduced two-photon and free-carrier absorptions at wavelengths beyond 2.2µm. Leveraging on these attributes, moderate to high brightness wide-bandwidth laser sources have been demonstrated based on supercontinuum generation (SCG) in this wavelength region, using waveguides fabricated on either crystalline silicon [4,5], amorphous silicon [6] or silicon nitride [7]. Furthermore, the development of on-chip sources providing short pulses has driven research towards integrating both the pump source and nonlinear element on the same chip [8].We have recently reported the first demonstrations of alloptical signal processing using silicon germanium waveguides both in the near-[9] and mid-IR [10]. These demonstrations, along with a detailed study on the optical properties of SiGe waveguides [11], have highlighted that the addition of germanium to silicon can enhance the nonlinear response in comparison to pure silicon, as well as act as an additional valuable design parameter that can impact a host of optical properties (such as linear loss, two-photon absorption (TPA) and dispersion) of the nonlinear waveguide.In this Letter, we have extended the work presented in [12] where we reported the generation of a broadband supercontinuum (SC) in a dispersion-engineered SiGe waveguide. The waveguide was pumped using femtosecond pump pulses at 2.4µm and the 30-dB bandwidth of the SC extended more than 1330 nm spanning both the mid-IR and the entire telecommunication wavelength window, while maintaining high spectral uniformity. A numerical model was also developed to study the SCG, providing excellent agreement with the exper...

Neuro-inspired implementations have attracted strong interest as a power efficient and robust alternative to the digital model of computation with a broad range of applications. Especially, neuro-mimetic systems able to produce and process spike-encoding schemes can offer merits like high noise-resiliency and increased computational efficiency. Towards this direction, integrated photonics can be an auspicious platform due to its multi-GHz bandwidth, its high wall-plug efficiency and the strong similarity of its dynamics under excitation with biological spiking neurons. Here, we propose an integrated all-optical neuron based on an InAs/InGaAs semiconductor quantum-dot passively mode-locked laser. The multi-band emission capabilities of these lasers allows, through waveband switching, the emulation of the excitation and inhibition modes of operation. Frequency-response effects, similar to biological neural circuits, are observed just as in a typical two-section excitable laser. The demonstrated optical building block can pave the way for high-speed photonic integrated systems able to address tasks ranging from pattern recognition to cognitive spectrum management and multi-sensory data processing.

Abstract:We demonstrate four wave mixing (FWM) based wavelength conversion of 40 Gbaud differential phase shift keyed (DPSK) and quadrature phase shift keyed (QPSK) signals in a 2.5 cm long silicon germanium waveguide. For a 290 mW pump power, bit error ratio (BER) measurements show approximately a 2-dB power penalty in both cases of DPSK (measured at a BER of 10 −9 ) and QPSK (at a BER of 10 −3 ) signals that we examined.