ICFO – The Institute of Photonic Sciences

About: ICFO – The Institute of Photonic Sciences is a facility organization based out in Barcelona, Spain. It is known for research contribution in the topics: Quantum & Quantum entanglement. The organization has 872 authors who have published 1965 publications receiving 56273 citations.

Current status and technological prospect of photodetectors based on two-dimensional materials.

Abstract: Photodetectors are an essential component in a vast number of devices and applications nowadays for they are the cornerstone component of image sensors, ambient sensors in consumer electronics, in spectrometry, biomedical imaging, food and manufacturing process monitoring, just to name a few. The biggest portion of the photodetector market is currently served by silicon (CMOS-based) photodetectors in view of their high performance, low cost, maturity and high level of integration with electronics. Applications that require photodetection in the infrared, i.e., beyond silicon’s bandgap, are currently relying on exotic semiconductors such as III-V InGaAs or HgCdTe systems that can cover a spectral beyond 10 μm. Such technologies, albeit offering high performance detectors, suffer from severe manufacturing costs and integration issues, and therefore are limited only to niche low-volume, high-value markets. This has a major impact on several applications (night vision, infrared spectrometry, infrared imaging) that would provide indispensable information to consumers and automotive industry in terms of health, safety and security. This grand challenge is one that two-dimensional (2D) materials are called for to address, and offer an opportunity to bring about a significant market value growth as well as profound socioeconomic impact. Among the various optoelectronic applications considered for 2D materials, one that has therefore attracted significant attention is that of photodetectors1. Graphene, an atomically thin semimetallic material with extraordinarily large carrier mobility, flat broadband absorption, and electrostatically tunable carrier concentration, offers unique properties that can be leveraged for photodetection. 2D semiconductor analogs also provide very high carrier mobilities—especially taking into account their nearly atomic thin profiles—and a spectral coverage both in the visible and in the infrared wavelength range, depending upon the material selection. A common additional feature of those materials is their ‘form factor’ and the resulting possibility to enable high performance optoelectronic devices that are ultra-low-weight, flexible, and therefore suited for seamless integration in a variety of substrates, either rigid or flexible, single crystalline or amorphous etc.

Graphene-based, mid-infrared, room-temperature pyroelectric bolometers with ultrahigh temperature coefficient of resistance

Abstract: There is a growing number of applications demanding highly sensitive photodetectors in the mid-infrared. Thermal photodetectors, such as bolometers, have emerged as the technology of choice, because they do not need cooling. The performance of a bolometer is linked to its temperature coefficient of resistance (TCR, ∼2–4% K−1 for state-of-the-art materials). Graphene is ideally suited for optoelectronic applications, with a variety of reported photodetectors ranging from visible to THz frequencies. For the mid-infrared, graphene-based detectors with TCRs ∼4–11% K−1 have been demonstrated. Here we present an uncooled, mid-infrared photodetector, where the pyroelectric response of a LiNbO3 crystal is transduced with high gain (up to 200) into resistivity modulation for graphene. This is achieved by fabricating a floating metallic structure that concentrates the pyroelectric charge on the top-gate capacitor of the graphene channel, leading to TCRs up to 900% K−1, and the ability to resolve temperature variations down to 15 μK. There is emerging interest in photodetectors in the mid-infrared driven by increasing need to monitor the environment for security and healthcare purposes. Sassiet al. show a thermal photodetector, based on the coupling between graphene and a pyroelectric crystal, which shows high temperature sensitivity.

Out-of-plane heat transfer in van der Waals stacks through electron-hyperbolic phonon coupling.

Abstract: Van der Waals heterostructures have emerged as promising building blocks that offer access to new physics, novel device functionalities and superior electrical and optoelectronic properties 1–7 . Applications such as thermal management, photodetection, light emission, data communication, high-speed electronics and light harvesting 8–16 require a thorough understanding of (nanoscale) heat flow. Here, using time-resolved photocurrent measurements, we identify an efficient out-of-plane energy transfer channel, where charge carriers in graphene couple to hyperbolic phonon polaritons 17–19 in the encapsulating layered material. This hyperbolic cooling is particularly efficient, giving picosecond cooling times for hexagonal BN, where the high-momentum hyperbolic phonon polaritons enable efficient near-field energy transfer. We study this heat transfer mechanism using distinct control knobs to vary carrier density and lattice temperature, and find excellent agreement with theory without any adjustable parameters. These insights may lead to the ability to control heat flow in van der Waals heterostructures. Observation of an efficient out-of-plane energy transfer channel in van der Waals heterostructures, where charge carriers in graphene couple to hyperbolic phonon–polaritons on a picosecond timescale.

Attosecond coherent control of free-electron wave functions using semi-infinite light fields.

Abstract: Light-electron interaction is the seminal ingredient in free-electron lasers and dynamical investigation of matter. Pushing the coherent control of electrons by light to the attosecond timescale and below would enable unprecedented applications in quantum circuits and exploration of electronic motions and nuclear phenomena. Here we demonstrate attosecond coherent manipulation of a free-electron wave function, and show that it can be pushed down to the zeptosecond regime. We make a relativistic single-electron wavepacket interact in free-space with a semi-infinite light field generated by two light pulses reflected from a mirror and delayed by fractions of the optical cycle. The amplitude and phase of the resulting electron-state coherent oscillations are mapped in energy-momentum space via momentum-resolved ultrafast electron spectroscopy. The experimental results are in full agreement with our analytical theory, which predicts access to the zeptosecond timescale by adopting semi-infinite X-ray pulses.