Lasers

Researchers from Arizona State University (ASU) have presented a design concept for enhanced saturable absorption effect based on subwavelength-thick (<1/5λ0) hybrid graphene-plasmonic metasurface structures in infrared wavelengths. Yu Yao and her research team at the ASU Center for Photonics Innovation designed a faster and more energy-efficient nanoscale laser component called the graphene-plasmonic hybrid metastructure saturable absorber, known as GPSMA.

The team's theoretical and experimental results demonstrated that, by exciting nonequilibrium carriers inside nanoscale hotspots, one could not only enhance the saturable absorption in graphene, but also reduce the saturation fluence by over 3 orders of magnitude (from ∼1 mJ/cm² to ∼100 nJ/cm²). Their pump–probe measurement results suggested an ultrashort saturable absorption recovery time (<60 fs), which is ultimately determined by the relaxation dynamics of photoexcited carriers in graphene. They also observed pulse narrowing effects in the devices based on the autocorrelation measurement results. Such design concepts can be tailored via structure engineering to operate in broader wavelength ranges up to mid- and far- infrared spectral regions. These ultrafast low-saturation fluence saturable absorber designs can enable low-threshold, compact, self-starting mode-locked lasers, laser pulse shaping, and high-speed optical information processing.

Cambridge Raman Imaging (CRI) has announced it was selected to coordinate a project that received a €3.3 million grant in the European Innovation Council’s (EIC) Transition call.

The project, called CHARM, aims to develop a medical device based on high-speed, low-cost Raman digital imaging technology and artificial intelligence to transform cancer diagnosis and treatment. The technology will analyze the molecular composition of patient tissue samples to distinguish cancerous from healthy cells without the need for chemical staining.

A team of researchers, led by Professor Konstantin Arutyunov of the HSE Tikhonov Moscow Institute of Electronics and Mathematics (MIEM HSE), has developed a graphene-based mechanical resonator, in which coherent emission of sound energy quanta, or phonons, has been induced. Such devices, called phonon lasers, could have wide potential for applications in information processing, as well as classical and quantum sensing of materials.

Using an analogy with photons, quanta of the electromagnetic spectrum, there are also particles of sound energy, phonons. In fact, these are artificially introduced objects in physics—quasi-particles, which correspond to vibrations of the crystal lattice of matter.

In May 2017 we reported the the Institute of Low Temperature and Structure Research (Wroclaw, Poland) developed a new efficient white light source that uses graphene foam excitated by a continuous-wave laser. We have seen a demonstration of the technology at IDTechEx 2019 (see video below).

We have recently spoken with Prof. Krzysztof Piech who updated us on the project's process. Prof. Piech tells us that the research team received a grant of around $130,000 to develop the technology, and are expecting to soon receive a $270,000 grant that will enable the production of a series of prototypes. We hope to update once these prototypes can be demonstrated.

In May 2017 we reported on a new project at the Institute of Low Temperature and Structure Research (Wroclaw, Poland) that developed a new efficient white light source that uses graphene foam excitated by a continuous-wave laser.

The project is still in progress, and the researchers demonstrated the technology at IDTechEx Graphene & 2D Materials Europe 2019 earlier this month, as can be seen in our video above.

Researchers from the Moscow Institute of Physics and Technology (MIPT) in Russia and Tohoku University in Japan have explained the phenomenon of particle-antiparticle annihilation in graphene, recognized by specialists as Auger recombination.

Two scenarios of electron-hole recombination in graphene: radiative recombination (left) and Auger recombination (right) in which the energy is picked up by an electron passing by

Despite persistently being spotted in experiments, it was thought to be prohibited by the fundamental physical laws of energy and momentum conservation. The theoretical explanation of this process has until recently remained one of the greatest puzzles of solid-state physics.

Researchers at the Institute for Basic Science (IBS, South Korea), in collaboration with teams from the University of Birmingham and the Korea Advanced Institute of Science and Technology (KAIST), have developed unique graphene-based lenses with tunable features. These optical devices, made of graphene and a punctured gold surface, could become optical components for advanced applications like amplitude tunable lenses, lasers (i.e. vortex phase plates), and dynamic holography.

The scientists explain that metasurfaces are new 2D materials that can effectively control the electric and magnetic components of light (and other electromagnetic waves) and bend them to chosen directions. Controlling the beam's direction can bring out interesting phenomena; the most incredible being the "invisibility cloak effect", where light waves bypass an object recreating the image beyond the object.

Researchers from CNR-Istituto Nanoscienze, Italy and the University of Cambridge, UK, associated with the ​Graphene Flagship, have shown that it is possible to create a terahertz saturable absorber using graphene, produced by liquid phase exfoliation and deposited by transfer coating and ink jet printing. The paper reports a terahertz saturable absorber with an order of magnitude higher absorption modulation than other devices produced to date.

A terahertz saturable absorber decreases its absorption of light in the terahertz range (far infrared) with increasing light intensity and has great potential for the development of terahertz lasers, with applications in spectroscopy and imaging. These high-modulation, mode-locked lasers open up many prospects in applications where short time scale excitation of specific transitions are important, such as time-resolved spectroscopy of gasses and molecules, quantum information or ultra-high speed communication.

The EU-funded GOSFEL project (Graphene on Silicon Free Electron Laser), demonstrated a new type of compact laser source, which exploits graphene to create a solid-state free electron laser. Compact and low-cost lasers could benefit many indusries, like communications, security, sensors and more.

Free Electron Lasers (FELs) offer an alternative to conventional lasers being potentially the most efficient, high powered and flexible generators of tunable coherent radiation from the ultra-violet to the infrared. However, currently FELs are prohibitively large and expensive. The GOSFEL project used graphene to create a compact, relatively inexpensive, solid-state version of such a laser.

Fuji Pigment recently announced the development of a large-scale manufacturing process for carbon and graphene quantum dots (QDs). QDs are usually made of semiconductor materials that are expensive and toxic, especially Cd, Se, and Pb. Fuji Pigment stated that its toxic-metal-free QDs exhibit a high light-emitting quantum efficiency and stability comparable to the toxic metal-based quantum dots.

Quantum yield of the carbon QDs currently exceeds 45%, and the company said it is still pursuing higher quantum efficiency. Quantum yield of the graphene quantum dot is over 80%. QD’s ability to precisely convert and tune a spectrum of light makes them ideal for TV displays, smartphones, tablet displays, LEDs, medical experimental imaging, bioimaging, solar cells, security tags, quantum dot lasers, photonic crystal materials, transistors, thermoelectric materials, various type of sensors and quantum dot computers.