Generating and distributing encryption keys via chaos synchronization of optical systems is a promising method for achieving secure and fast real-time encryption of large data volumes. However, current state-of-the-art systems based on lasers subjected to time-delayed feedback have exhibited serious limitations in regard to stability and speed due to their inherent phase sensitivity and their fundamental bandwidth limitation by the laser relaxation oscillation frequency. Here, we propose, simulate, and build a fundamentally different concept based on optoelectronic oscillators (OEOs) to generate and distribute encryption keys. We demonstrate both theoretically and experimentally that by injecting chaotic OEOs with a common external chaotic signal, chaos synchronization can be achieved. The key distribution signal shared between sender and receiver is in the optical domain and can thus be transmitted over a standard fiber-optic network. As the optoelectronic feedback is phase insensitive, stable synchronization becomes possible without any need for active stabilization, resulting in a compact and inexpensive setup. From the chaotic time traces, identical random bit sequences can be generated on the sender’s and receiver’s sides at rates of up to 6 GBit/s, which is comparable to current state-of-the-art systems of the same bandwidth. Since OEOs are not bandwidth limited by relaxation oscillations, the key generation can be further increased compared to laser-based systems by increasing the OEO bandwidth, thus presenting a promising platform for achieving fast and secure real-time encryption.

Fluorescence imaging has been widely used in fields like (pre)clinical imaging and other domains. With advancements in imaging technology and new fluorescent labels, fluorescence lifetime imaging is gradually gaining recognition. Our research department is developing the tauCAM^TM, based on the Current-Assisted Photonic Sampler, to achieve real-time fluorescence lifetime imaging in the NIR (700–900 nm) region. Incorporating fluorescence lifetime into endoscopy could further improve the differentiation of malignant and benign cells based on their distinct lifetimes. In this work, the capabilities of an endoscopic lifetime imaging system are demonstrated using a rigid endoscope involving various phantoms and an IRF-free deep learning-based method with only 6-time points. The results show that this application’s fluorescence lifetime image has better lifetime uniformity and precision with 6-time points than the conventional methods.

A 64 × 64-pixel current-assisted photonic sampler (CAPS) image sensor is designed for real-time fluorescence lifetime (FLT) imaging. Current-assistance is used for swift detection and time-gating of the photogenerated carriers within the whole substrate. An additional bias node is used to decrease the dynamic power consumption and a photogate is applied to the sensor to reduce the carrier transfer time. The sensor is fabricated in a commercial 350nm CMOS process on a 15μm epi-layer, with 30μm pixels and a 61% fill factor. The pixel features gating widths below 1 ns subject to a 17 ps standard deviation on the gate width uniformity, and a 31 ps standard deviation on its temporal position. The pixel has a quantum efficiency (QE) above 40% for near-infrared (NIR) wavelengths, whereas the peak QE is 61% at 675 nm. The gate’s intrinsic decay is observed to be 320 ps, which allows for the FLT imaging of sub-nanosecond lifetime dyes. The real-time FLT imaging capabilities are demonstrated on commercial fluorescence phantoms and in a preclinical experiment.

Fluorescence-guided surgery is a significant advancement in medical imaging, particularly for distinguishing malignant from healthy tissue during cancer surgery. Recent advancements in endoscopy technology and fluorescence-lifetime (FLT) imaging can provide better insight into identifying abnormal tissues during surgery than white light endoscopy imaging. Current imaging systems used in fluorescence-guided surgery are primarily designed to provide surgeons with a combined view of natural color (RGB) images and fluorescence overlays. These systems typically rely on an RGB camera, incapable of FLT imaging. Our novel approach sequentially illuminates the scene with red, green, and blue light pulses and Near Infrared (NIR) pulses, captured selectively with a single fast time-gated camera. The camera is synchronized to the pulsed illumination and positions its gate windows to capture only one of the illumination pulses; afterwards, it overlays the NIR fluorescence lifetime image on the natural color image. The VUB-ETRO team developed the tauCAMTM camera based on Current-Assisted Photonic Sampler (CAPS) image sensor technology, which intends to offer real-time FLT imaging, particularly in the NIR area. This paper presents an LED-based time-multiplexing RGB + FLT endoscopy imaging with tauCAMTM, designed to enhance visualization in real-time surgical settings. By combining RGB and FLT imaging, surgeons could receive comprehensive insights into tissue characteristics, supporting precise interventions.

In vivo fluorescence lifetime (FLT) imaging is an emerging and promising modality with the potential to provide additional biological information compared to fluorescence intensity (FI) imaging. Until now, nearly all studies evaluating the benefits of FLT imaging in vivo have been conducted using cyanine dyes. While these fluorophores are highly successful for conventional in vivo fluorescence imaging due to their unmatched brightness in the NIR-I region (700-900 nm), they might be suboptimal for FLT imaging. Indeed, NIR-I cyanines are characterized by short singlet excited-state lifetime (generally below 1 ns) making it challenging to differentiate them from tissue autofluorescence. Therefore, there is a pressing need for biocompatible fluorophores with longer FLTs. Herein, we report a novel bioconjugatable water-soluble NIR-emissive aza-BODIPY dye with extended FLT values in physiological conditions, compared to cyanine dyes (increase of 100% compared to IRDye® 800CW). The suitability of aza-BODIPY for FLT imaging when conjugated to an antibody was assessed to enhance this technology. Beyond rational design and synthesis of a long-wavelength fluorophore with attractive features for in vivo FLT imaging, this study also highlights for the first time the impact of the conjugation method on the FLT characteristics of the resulting fluorescent antibody conjugates.