Four-wave Mixing In Silicon Waveguide Research Articles

Photonic-reconfigurable entanglement distribution network based on silicon quantum photonics

The entanglement distribution network connects remote users by sharing entanglement resources, which is essential for realizing quantum internet. We propose a photonic-reconfigurable entanglement distribution network (PR-EDN) based on a silicon quantum photonic chip. The entanglement resources are generated by a quantum light source array based on spontaneous four-wave mixing in silicon waveguides and distributed to different users through time-reversed Hong–Ou–Mandel interference by on-chip Mach–Zehnder interferometers with thermo-optic phase shifters (TOPSs). A chip sample is designed and fabricated, supporting a PR-EDN with 3 subnets and 24 users. The network topology of the PR-EDN could be reconfigured in three network states by controlling the quantum interference through the TOPSs, which is demonstrated experimentally. Furthermore, a reconfigurable entanglement-based quantum key distribution network is realized as an application of the PR-EDN. The reconfigurable network topology makes the PR-EDN suitable for future quantum networks requiring complicated network control and management. Moreover, it is also shown that silicon quantum photonic chips have great potential for large-scale PR-EDN, thanks to their capacities for generating and manipulating plenty of entanglement resources.

Recent Progress in Short and Mid-Infrared Single-Photon Generation: A Review

The generation of single photons in the mid-infrared spectral region is attracting the interest of scientific and technological research, motivated by the potential improvements that many important and emerging applications, such as quantum sensing, metrology and communication, could benefit from. This review reports the progress in short and mid-infrared single photon generation, focusing on probabilistic sources based on the two non-linear processes of spontaneous parametric downconversion (SPDC) and four wave mixing (FWM). On one hand, numerical simulations of mid-infrared SPDC are described as a powerful tool to assist and guide the experimental realization, along with the implementation and engineering of novel non-linear materials. On the other hand, the advantages offered by FWM in silicon waveguides in terms of integration, miniaturization and manufacturability are presented, providing an optimal technology for integrated quantum applications.

Mode-Entanglement in Silicon Waveguides Through Intermodal Four-Wave Mixing

Silicon photonics is rapidly emerging as a promising, scalable platform for quantum information applications. As the technology matures, sources of high-quality quantum-optical states are increasingly important. We discuss the use of intermodal four-wave mixing in silicon waveguides for creating entangled photon pairs. We describe a framework to numerically analyze the state of produced photon pairs and discuss a scheme for generating photon pairs that are purely entangled in their transverse waveguide mode. Using this scheme, we find a theoretical fidelity of 99.6 % to a true Bell state in the transverse mode with no spectral correlations.

Intermodal four-wave mixing in silicon waveguides

In this work, we report the modeling and the experimental demonstration of intermodal spontaneous as well as stimulated four-wave mixing (FWM) in silicon waveguides. In intermodal FWM, the phase-matching condition is achieved by exploiting the different dispersion profiles of the optical modes in a multimode waveguide. Since both the energy and the wave vectors have to be conserved in the FWM process, this leads to a wide tunability of the generated photon wavelength, allowing us to achieve a large spectral conversion. We measured several waveguides that differ by their widths and demonstrate large signal generation spanning from the pump wavelength (1550 nm) down to 1202 nm. A suited setup evidences that the different waves propagated indeed on different order modes, which supports the modeling. Despite observing a reduced efficiency with respect to intramodal FWM due to the decreased modal overlap, we were able to show a maximum spectral distance between the signal and idler of 979.6 nm with a 1550 nm pump. Our measurements suggest the intermodal FWM is a viable means for large wavelength conversion and heralded photon sources.

Impact of two-photon absorption and free-carrier effects on time lens based on four-wave mixing in silicon waveguides

We investigate the influences of two-photon absorption (TPA) and free-carrier effects on a time lens via four-wave mixing in silicon waveguides. It is found that the output waveform is severely modulated and the conversion efficiency is sharply reduced in temporal imaging owing to the impacts of the nonlinear absorption. A silicon–organic hybrid slot waveguide with negligible TPA is proposed for the time lens, which could realize 600× magnification of femtosecond pulses. These results can increase the signal bandwidth from gigahertz to terahertz and give rise to important potential applications for ultrafast optical signal processing in integrated optics, ultrafast optics, and optical communications.

40 Gb/s reconfigurable optical logic gates based on FWM in silicon waveguide.

Here we experimentally demonstrate reconfigurable logic gates via four-wave-mixing (FWM) in silicon waveguide with an operating speed of up to 40 Gb/s. After demodulated by a 40-GHz delay interferometer (DI), four non-return-to-zero differential phase shift keying (NRZ-DPSK) signals with carefully selected wavelengths are launched into the waveguide at the same time. Thanks to the effective FWM in silicon nano-waveguide, a full set of the two-input logic minterms can be generated simultaneously, and arbitrary combinational logic functions are able to be realized by properly combining these minterms.

Efficient terahertz-wave generation via four-wave mixing in silicon membrane waveguides

Terahertz (THz) wave generation via four-wave mixing (FWM) in silicon membrane waveguides is theoretically investigated with mid-infrared laser pulses. Compared with the conventional parametric amplification or wavelength conversion based on FWM in silicon waveguides, which needs a pump wavelength located in the anomalous group-velocity dispersion (GVD) regime to realize broad phase matching, the pump wavelength located in the normal GVD regime is required to realize collinear phase matching for the THz-wave generation via FWM. The pump wavelength and rib height of the silicon membrane waveguide can be tuned to obtain a broadband phase matching. Moreover, the conversion efficiency of the THz-wave generation is studied with different pump wavelengths and rib heights of the silicon membrane waveguides, and broadband THz-wave can be obtained with high efficiency exceeding 1%.

Influence of spectral broadening on femtosecond wavelength conversion based on four-wave mixing in silicon waveguides

Femtosecond wavelength conversion in the telecommunication bands via four-wave mixing in a 1.5 mm long silicon rib waveguide is theoretically investigated. Compared with picosecond pulses, the spectra are greatly broadened for the femtosecond pulses due to self-phase modulation and cross-phase modulation in the four-wave mixing process, and it is difficult to achieve a wavelength converter when the pump and signal pulse widths are close to or less than 100 fs in the telecommunication bands because of the spectral overlap. The influence of the spectral broadening on the conversion efficiency is also investigated. The conversion bandwidth of 220 nm and peak conversion efficiency of -8 dB are demonstrated by using 500 fs pulses with higher efficiency than the picosecond pulse-pumped efficiency when the repetition rate is 100 GHz.

Optimized wavelength conversion in silicon waveguides based on “off-Raman-resonance” operation: extending the phase mismatch formalism

We present a generic approach to determine the phase mismatch for any optical nonlinear process. When applying this approach, which is based on the evaluation of local phase changes, to Raman- and Kerr-based four-wave mixing in silicon waveguides, we obtain an expression for the phase mismatch which is more accurate as compared to the conventional definition; and which contains additional contributions due to the dispersion of the four-wave-mixing processes. Furthermore, starting from the general propagation equations for the involved pump, Stokes and anti-Stokes waves, we investigate the impact of this four-wave-mixing dispersion in silicon waveguides and examine how it is influenced by changing the frequency difference between the pump and Stokes input waves. We show by means of numerical simulations that, by detuning this frequency difference slightly away from Raman resonance, the four-wave-mixing conversion efficiency can be more than doubled, but can also lead to a decrease in efficiency of more than 10 dB. We also discuss how the pump-Stokes frequency difference that is optimal for wavelength conversion varies with the length of the silicon waveguides and with their dispersion characteristics. Finally, starting from the newly introduced phase mismatch formula we simplify the set of propagation equations such that they are less computationally intensive to solve while still giving accurate estimates of the optimal pump-Stokes frequency difference and the corresponding wavelength conversion efficiency.

Continuous Wavelength Conversion of 40-Gb/s Data Over 100 nm Using a Dispersion-Engineered Silicon Waveguide

We demonstrate broadband continuous wavelength conversion based on four-wave mixing in silicon waveguides, operating with data rates up to 40 Gb/s, validating signal integrity using bit-error-rate measurements. The dispersion-engineered silicon waveguide provides broad phase-matching bandwidth, enabling complete wavelength-conversion coverage of the <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</i> -, <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C</i> -, and <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</i> -bands of the International Telecommunication Union (ITU) grid. We experimentally show this with wavelength conversion of high-speed data exceeding 100 nm, and characterize the resulting power penalty induced by the wavelength conversion process. We then validate the bit-rate transparency of the all-optical process by scaling the data rate from 5 Gb/s up to 40 Gb/s at the 100-nm wavelength conversion configuration, showing consistent low power penalties, validating the robustness of the four-wave mixing process in the silicon platform for all-optical processing.

Mid-infrared wavelength conversion in silicon waveguides using ultracompact telecom-band-derived pump source

Using probe and pump waves derived from ultra-compact telecom optical fibre sources, scientists perform four-wave mixing in silicon waveguides in the spectral region beyond 2 µm, achieving mid-infrared wavelength generation of 2388 nm over a bandwidth of 630 nm on a silicon chip.

Ultra-broadband one-to-two wavelength conversion using low-phase-mismatching four-wave mixing in silicon waveguides

An ultra-broadband wavelength conversion is presented and experimentally demonstrated based on nondegenerate four-wave mixing in silicon waveguides. Two idlers can be generated and their wavelengths can be freely tuned by using two pumps where the first pump is set close to the signal and the second pump is wavelength tunable. Using this scheme, a small phase-mismatch and hence an ultra-broad conversion bandwidth is realized in spite of the waveguide dispersion profile. We show that the experimental demonstrations are consistent with the theoretical estimations. Total conversion bandwidth is estimated to reach >500 nm and it can provide a feasible approach to realize one-to-two wavelength conversion among different telecommunication bands between 1300 nm and 1800 nm.

Ultralong continuously tunable parametric delays via a cascading discrete stage

We report experimental demonstration of an all-optical continuously tunable delay line based on parametric mixing with a total delay range of 7.34 mus. The bit-error rate performance of the delay line was characterized for a 10-Gb/s NRZ data channel. This result is enabled by cascading a discrete delay line that consists of 16 wavelength-dependent delays and a continuously tunable delay stage. Four wavelength conversion stages based on four-wave mixing in silicon waveguides were performed in order to achieve wavelength-preserving operation. The wavelength-optimized optical phase conjugation scheme employed in the delay line is capable of minimizing the residual dispersion for the entire tuning range.

Spectral phase conjugation via temporal imaging

We experimentally demonstrate wavelength-preserving spectral phase conjugation for compensating chromatic dispersion and self-phase modulation in optical fibers. Our implementation is based on a temporal imaging scheme that uses time lenses realized by broadband four-wave mixing in silicon waveguides. By constructing a temporal analog of a 4-f imaging system, we compensate for pulse distortions arising from second- and third-order dispersion and self-phase modulation in optical fibers.