We review our recent experiment on the Terabit-class coherent optical communication using a photonics integrated circuit-based optical amplifier. The 25.6-Tb/s 16-channel wavelength-division multiplexed (WDM) transmission (over 81-km fiber) proved the potential of such on-chip amplification for future coherent applications.
The field of topological photonics leverages concepts from geometry and topology – the branch of mathematics that deals with global properties that cannot be changed under continuous deformation – to produce electromagnetic modes that propagate with immunity to certain types of disorder and imperfections. In the last few years, several experiments have achieved the generation and propagation of quantum states of light in these so-called topological modes, demonstrating enhanced robustness of such inherently fragile quantum states. In this talk we will focus on our recent results in this area including topological protection of spatial entanglement and the demonstration of topology as an additional degree of freedom for entanglement using CMOS-compatible silicon photonics platforms.
Recent advances in the field of photonics and topological physics can be combined to offer a solution to planar 6G, above 100 GHz, communication devices. As specific examples, we demonstrate that a hybrid photonic crystal waveguide can support a single-mode transmission covering 0.367–0.411 THz (over twice as wide as that of all-silicon photonic crystal waveguides). By breaking the photonic crystal symmetry, topologically protected modes can be introduced with a single mode linear-dispersion transmission window (over 0.143–0.162 THz) and robust transmission around sharp corners without any deterioration in the bandwidth. Such topologically protected waveguides, here produced using simple 3D printing techniques, offer a unique simplification in design. The absence of coupling to back-propagating modes removes the requirement to carefully design away spurious resonances, offering a pathway to a truly versatile planar platform for integrated 6G devices with low loss and wide bandwidth.
In this talk we will discuss how to engineer the dispersion relation of photonic platforms to provide robust propagation of classical and quantum states of light. In the first part, we will unveil how to leverage the interaction of nonlinearity with higher orders of dispersion to create novel types of solitons, wave packets that propagate unperturbed for long distances. These objects have advantageous energy-width scaling laws with respect to conventional nonlinear Schrodinger solitons and show promise for applications in ultrafast lasers and integrated frequency combs. Subsequently, we will cover recent developments in topological quantum photonics. Topological photonics studies topological phases of light and leverages the appearance of robust topological edge states. We will emphasize our experimental demonstration of nonlinearly generated and topologically protected photon pairs and path-entangled biphoton states in silicon waveguide arrays. Further, we will detail our latest experiments demonstrating entanglement between topologically distinct modes, highlighting topology as an entanglement degree of freedom.
We review our recent work on the generation of novel optical solitons arising from different, high orders of dispersion and combinations thereof. By incorporating a spectral pulse-shaper in a mode-locked laser cavity, we can tailor the net-cavity dispersion, allowing us to access a wide range of new operating regimes corresponding to previously unobserved soliton pulses. We demonstrate the generation of solitons arising between self-phase modulation and any pure, negative even order of dispersion, as well as soliton molecules consisting of multiple solitons with different frequencies but that are temporally coincident.
After a successful decade of purely fundamental research, the topological photonics community is starting to explore applications more seriously. Among the most promising fields of application for topological photonics are integrated laser sources and quantum circuits. In this talk I will review the latest results on topologically protected quantum states of light, with an emphasis on our recent experimental demonstration of topological protection of photonic path entanglement. Our experimental platform is a bipartite lattice of silicon nanowires which supports to uncoupled topological edge states. By using a common weak pump evenly split between the two edge modes, and leveraging four-wave mixing in the silicon nanowires, we were able to encode a biphoton N00N state of two topological edge modes. We demonstrate that this spatial entanglement is preserved even in the presence of deliberately induced disorder in the position of the waveguides.
We report a fibre laser incorporating an intracavity pulse-shaper that induces a large anomalous net cavity quartic dispersion in which the mode-locked pulses propagate as pure-quartic solitons. We characterize the laser output pulses using a set of spectral and temporal phase resolved measurements and resonant dispersive wave analysis, and find that the results are in excellent agreement with analytic predictions.
The appeal of on-chip broadband supercontinuum generation (SCG) comes from its potential to pave the way to full integration of various ultrafast optics applications in frequency metrology, wavelength division multiplexing, and sensing. However, the generation of octave-spanning supercontinuum requires either the use of exceedingly short femtosecond pulses or large footprints. One promising method to achieve broadband supercontinuum is to exploit the high-order soliton fission. Bragg solitons leverage the large anomalous dispersion at the photonic band edge of nonlinear Bragg gratings, therefore they can facilitate high-order soliton fission in much shorter waveguide lengths and significantly lower powers. Soliton dynamics, especially fission, on CMOS-compatible platforms have been limited due to the nonlinear losses such as two-photon absorption and free carrier effects in silicon or low optical nonlinearities in traditional silicon nitride. We use compositionally engineered ultra-silicon-rich nitride (USRN) that possesses a large Kerr nonlinearity in the absence of two-photon absorption. Utilizing ideal nonlinear properties of USRN platform in conjunction with our monolithically integrated cascaded grating-waveguide design, we experimentally demonstrate × 4 spectral broadening enhancement, from 79 nm in the 7 mm long reference waveguide to 311 nm at the cascaded Bragg grating and waveguide device of the same footprint, using input pulses of 1.68 ps FWHM. This result is promising for generating wide supercontinuum, without the need to use sub-picosecond pulses or increasing the device footprint, by exploiting the high-order soliton dynamics availed through the simple photonic chip design consisting of a nonlinear Bragg grating and nonlinear waveguide.
Semiconductor optical waveguides have been the subject of intense study as both fundamental objects of study, as well as a path to photonic integration. In this talk I will focus on the nonlinear evolution of optical solitons in photonic crystal waveguides made of semiconductor materials. The ability to independently tune the dispersion and the nonlinearity in photonic crystal waveguides enables the examination of completely different nonlinear regimes in the same platform. I will describe experimental efforts utilizing time-resolved measurements to reveal a number of physical phenomena unique to solitons in a free carrier medium. The experiments are supported by analytic and numerical models providing a deeper insight into the physical scaling of these processes.
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