Phys.org April 21, 2021 An abrupt change in the Fermi surface topology, also called Lifshitz transition, can lead to the emergence of fascinating phenomena like colossal magnetoresistance and superconductivity. Controlling the electrons’ arrangement has been a key topic for decades. An international team of researchers (Germany, Sweden, US – research organization) has massively cut down the switching time to only 100 femtoseconds by shooting ultrashort optical laser pulses at a semi-metallic crystal composed of tungsten and tellurium atoms. Shining light on the crystal encourages it to reorganize its internal electronic structure, which also changes the conductivity of the crystal. They […]
Tag Archives: Lasers
Scientists propose novel self-modulation scheme in seeded free-electron lasers
Phys.org March 11, 2021 Seeded free-electron lasers (FELs), which use the frequency up-conversion of an external seed laser to improve temporal coherence, are ideal for providing fully coherent soft x-ray pulses. However, it is difficult to operate seeded FELs at a high repetition rate due to the limitations of present state-of-the-art laser systems. Researchers in China have developed self-modulation method for enhancing laser-induced energy modulation, thereby significantly reducing the requirement of an external laser system. They have experimentally realized high harmonic generation in a seeded FEL using an unprecedentedly small external laser-induced energy modulation. The results pave a way for […]
Colloidal quantum dot lasers poised to come of age
Nanowerk February 18, 2021 A team of researchers in the US (Los Alamos National Laboratory, Argonne National Laboratory) sums up the recent progress in colloidal-quantum-dot research and highlights the remaining challenges and opportunities in the rapidly developing field, which is poised to enable a wide array of new laser-based and LED-based technology applications. According to the researchers these tiny specs of semiconductor matter can generate spectrally tunable lasing light, opening tremendous opportunities in areas of photonic circuits, optical communications, lab-on-a-chip sensing, and medical diagnostics. They conclude that the accumulated knowledge, along with the approaches developed for manipulating the optical-gain properties […]
First bufferless lasers grown directly on silicon wafers in Si-photonics
Nanowerk March 4, 2020 In conventional approaches of integrating III-V lasers on Si thick III-V buffers up to a few micrometers are used to reduce the defect densities, which posses huge challenges for efficient light interfacing between the epitaxial III-V lasers and the Si-based waveguides. Based on numerical simulations an international team of researchers (China, Hong Kong) designed and fabricated a novel growth scheme to eliminate the requirement of thick III-V buffers and thus promoted efficient light coupling into the Si-waveguides. They demonstrated the 1.5 µm III-V lasers directly grown on the industry-standard 220 nm SOI wafers using metal organic […]
A laser for penetrating waves
Phys.org August 19, 2019 An international team of researchers (France, Poland, Germany, Russia, Czech Republic) used a heavy metal alloy of mercury, cadmium and tellurium (HgCdTe) that is used for highly sensitive thermal imaging cameras. Mercury, cadmium and tellurium contents can be very precisely chosen, which makes it possible to fine-tune the band gap. The material showed properties similar to graphene, but without the issue of strong Auger scattering. When electric current is applied it gets rid of its energy in the form of terahertz radiation. By varying an additional magnetic field of only about 200 millitesla, the experts were able […]
Researchers discover anti-laser masquerading as perfect absorber
Phys.org February 15, 2019 Researchers at Duke University constructed zirconia ceramic surface dimpled with cylinders like the face of a Lego brick. After computationally modeling the device’s properties by altering the cylinders’ size and spacing, the researchers realized that they had actually created a more fundamental kind of coherent perfect absorber (CPA) which can absorb both aligned and misaligned waves. Unlike typical CPAs the new material has three variables the cylinders’ radius, height and periodicity. This gives a lot of flexibility for tailoring the CPA model and put them in the frequency spectrum where needed…read more. TECHNICAL ARTICLE
Laser capable of emitting light quiet enough to move demanding scientific applications
Science Daily February 1, 2019 Under a DARPA sponsored initiative an international team of researcher (USA – UC Santa Barbara, industry partners, Northern Arizona University, Yale University, Portugal) has developed a chip-scale laser capable of emitting light with a fundamental linewidth of less than 1 Hz. They leveraged stimulated Brillouin scattering to build the lasers. The circuits were built with waveguides that are extremely low loss. They formed into a Brillouin laser ring cavity on the chip. They can store an extremely large number of photons on the chip, handle extremely high levels of optical power inside the optical cavity […]
Scientists demonstrate fractal light from lasers
Science Daily January 30, 2019 A team of researchers (South Africa, UK) has observed a variety of fractal shapes in transverse intensity cross sections through the lowest-loss eigenmodes of unstable canonical laser resonators, thereby demonstrating the controlled generation of fractal light inside a laser cavity. They advance the existing theory of fractal laser modes, first by predicting three-dimensional self-similar fractal structure around the center of the magnified self-conjugate plane and second by showing, quantitatively, that intensity cross sections are most self-similar in the magnified self-conjugate plane. The work offers a significant advance in the understanding of a fundamental symmetry of […]
New laser technology can identify unknown white powders from safe distance
Phys.org October 8, 2018 An international team of researchers (UK, USA – industry) was able to identify 11 white powder samples using their infrared laser system. No samples or disturbance of the powders were required, and they could be identified from up to one metre away. They illuminated each sample with broadband coherent light in the 8–9-µm band. Similarities between different spectra were quantified using Pearson’s correlation coefficient, confirming that spectral features in the 8–9-µm wavelength region were sufficient to discriminate between all eleven powders evaluated in the study. The researchers believe that the identification system will prove most useful […]
Building miniature lasers using nanowire
Nanowerk August 29, 2018 An international team of researchers (Norway, Australia, Sweden) has developed single-mode and room-temperature lasing from 890 to 990 nm, utilizing a novel design of single nanowires with GaAsSb-based multiple axial superlattices as a gain medium under optical pumping. The control of lasing wavelength via compositional tuning with excellent room-temperature lasing performance is shown to result from the unique nanowire structure with efficient gain material, which delivers a low lasing threshold, a lasing quality factor as high as 1250, and a high characteristic temperature of ∼129 K. These results present a major advancement for the design and […]