Search Results (5)

The article discusses the design, fabrication, and experimental evaluation of a large-area vertical grating coupler (VGC) enabling simultaneous coupling of multiple input optical beams. The presented VCG was fabricated by direct nanoimprinting of a grating pattern in a non-hardened SiO_X:TiO_Y waveguide (WG) film. The WG film was deposited on a glass substrate using a combination of the sol–gel method and the dip-coating technique. The fabrication process allowed precise control of the waveguide film thickness and refractive index, as well as the VGC geometry. The relevance of the process was proved by a demonstration of optical coupling of multiple quasi-parallel input beams via the VGC to the WG layer. To make this possible, a dedicated optical coupling system was designed, including a polymer microlens array and optical fiber array positioned in a V-groove. This opens promising perspectives on using the proposed structure for the fabrication of low-cost multichannel optical sensor chips, as highlighted in the article’s final section. Full article

The intrinsic third-order nonlinearity in silicon has proven it to be quite useful in the field of quantum optics. Silicon is suitable for producing time-correlated photon pairs that are sources of heralded single-photon states for quantum integrated circuits. A quantum signal source in the form of single photons is an inherent requirement for the principles of quantum key distribution technology for secure communications. Here, we present numerical simulations of a silicon ring with a 6 μ m radius side-coupled with a bus waveguide as the source for the generation of single photons. The photon pairs are generated by exploring the process of degenerate spontaneous four-wave mixing (SFWM). The free spectral range (FSR) of the ring is quite large, simplifying the extraction of the signal/idler pairs. The phase-matching condition is considered by studying relevant parameters like the dispersion and nonlinearity. We optimize the ring for a high quality factor by varying the gap between the bus and the ring waveguide. This is the smallest ring studied for photon pair generation with a quality factor in the order of 10 5 . The width of the waveguides is chosen such that the phase-matching condition is satisfied, allowing for the propagation of fundamental modes only. The bus waveguide is pumped at one of the ring resonances with the minimum dispersion (1543.5 nm in our case) to satisfy the principle of energy conservation. The photon pair generation rate achieved is comparable to the state of the art. The photon pair sources exploiting nonlinear frequency conversion/generation processes is a promising alternative to atom-like single-photon emitters in the field of integrated photonics. Such miniaturized structures will benefit future on-chip architectures where multiple single-photon source devices are required on the same chip. Full article

Optical Wireless Networks on-Chip are an emerging technology recently proposed to improve the interconnection between different processing units in densely integrated computing architectures. In this work, we propose a 4 × 4 optical wireless switch (OWS) based on optical phased arrays (OPAs) for broadband reconfigurable on-chip communication. The OPA and OWS design criteria are reported. Moreover, the performances of the OWS are analyzed and optimized considering the electromagnetic propagation in on-chip multilayer structures, with different thicknesses of the cladding layer. The effect on the OWS behavior of a non-ideal distribution of the power in input to the OPA is also investigated by designing a 1 × 7 beam splitter, based on a single-stage multi-mode interference (MMI) device to be used as a single element of the OWS. Then, the MMI output signals are considered in input to the transmitting OPAs and the OWS performances are evaluated. Full article

We present an integrated single-photon detection device custom designed for quantum key distribution (QKD) with time-bin encoded single photons. We implemented and demonstrated a prototype photon-to-digital converter (PDC) that integrates an 8 × 8 single-photon avalanche diode (SPAD) array with on-chip digital signal processing built in TSMC 65 nm CMOS. The prototype SPADs are used to validate the QKD functionalities with an array of time-to-digital converters (TDCs) to timestamp and process the photon detection events. The PDC uses window gating to reject noise counts and on-chip processing to sort the photon detections into respective time-bins. The PDC prototype achieved a 22.7 ps RMS timing resolution and demonstrated operation in a time-bin setup with 158 ps time-bins at an optical wavelength of 410 nm. This PDC can therefore be an important building block for a QKD receiver and enables compact and robust time-bin QKD systems with imaging detectors. Full article