Phys.org March 6. 2023 Unburnt hydrocarbon flames produce soot which is the second biggest contributor to global warming. The state-of-the-art high-speed imaging techniques do not provide a complete picture of flame-laser interactions, important for understanding soot formation. An international team of researchers (USA – Caltech, Washington University, Sweden, Germany) has developed single-shot laser-sheet compressed ultrafast photography (LS-CUP) for billion-frames-per-second planar imaging of flame-laser dynamics. They observed laser-induced incandescence, elastic light scattering, and fluorescence of soot precursors – polycyclic aromatic hydrocarbons (PAHs) in real-time using a single nanosecond laser pulse. The spatiotemporal maps of the PAHs emission, soot temperature, primary nanoparticle […]
Tag Archives: Laser
Physicists build an atom laser that can stay on forever
Phys.org June 14, 2022 Bose–Einstein condensates (BECs) are important to quantum simulation and sensing. A long-standing constraint for quantum gas devices has been the need to execute cooling stages time-sequentially, restricting these devices to pulsed operation. Researchers in the Netherlands demonstrated continuous Bose–Einstein condensation by creating a continuous-wave (CW) condensate of strontium atoms that lasts indefinitely. The coherent matter wave is sustained by amplification through Bose-stimulated gain of atoms from a thermal bath. By steadily replenishing this bath while achieving 1,000 times higher phase-space densities than previous works they maintained the conditions for condensation. Their experiment is the matter wave […]
A leap forward for terahertz lasers
Science Daily January 26, 2022 Despite decades of research, no frequency tunable sources span the terahertz gap between 0.3 and 3 THz. By introducing methyl fluoride (CH3F) as a new gain medium for a quantum cascade laser-pumped molecular laser (QPML), a team of researchers in the US (Harvard University, industry, DEVCOM ARL, Duke University) has demonstrated continuous-wave lasing from more than 120 discrete transitions, spanning the range from 0.25 to 1.3 THz. Due to its large permanent dipole moment and large rotational constants, methyl fluoride (CH3F) as a QPML gain medium combines a lower threshold, a larger power efficiency, and […]
New type of metasurface allows unprecedented laser control
Phys.org June 29, 2021 An international team of researchers (USA – Harvard University, Italy) has developed a tunable laser that has two components—a laser diode and a reflective metasurface. The metasurface surface uses supercells, groups of pillars which work together to control different aspects of light. It is designed so that only the selected wavelength has the correct direction to enter back in the diode enabling the laser to operate only at that specific wavelength. The wavelength can be changed by moving the metasurface with respect to the laser diode. The shape of the laser beam can be fully controlled […]
Quantum laser turns energy loss into gain
Phys.org July 7, 2021 Parity-time reversal symmetry in non-Hermitian systems realizes spontaneous symmetry breaking. A team of researchers in South Korea have demonstrated that such direct coupling can remodel conventional photonic platforms of non-Hermitian systems into polaritonic platforms with a single component; thus, improving the degrees of freedom of both integration and design for the coupled system. In this system, they found that as energy loss increased, the amount of energy needed to induce lasing decreased. By controlling the degree of loss between the microcavity and the semiconductor substrate the threshold energy becomes smaller as energy loss increases. According to […]
Scientists develop first electrically-driven ‘topological’ laser
Phys.org February 13, 2020 Previous demonstrations of topological lasers have required an external laser source for optical pumping and have operated in the conventional optical frequency regime. An international team of researchers (Singapore, UK) demonstrated an electrically pumped terahertz quantum cascade laser based on topologically protected valley edge states. Unlike topological lasers that rely on large-scale features to impart topological protection, the compact design makes use of the valley degree of freedom in photonic crystals, analogous to two-dimensional gapped valleytronic materials. With regularly spaced emission peaks lasing occurs in a sharp-cornered triangular cavity, even if perturbations are introduced into the […]
Cutting through fog with laser focus
Phys.org January 7, 2020 Most of the previous studies demonstrated spatial focusing to the speckle grain size, and manipulation of the temporal properties of the achieved focus. Researchers in Australia demonstrate an approach to control the total temporal impulse response, not only at a single speckle grain but overall spatial degrees of freedom (spatial and polarization modes) at any arbitrary delay time through a multimode fiber. Global enhancement or suppression of the total light intensity exiting a multimode fibre is shown for arbitrary delays and polarization states. This work could benefit to applications that require pulse delivery in disordered media, […]
Quantum dot lasers move a step closer with electric-pumping development
Phys.org November 29, 2019 Colloidal quantum dots (CQDs) are highly promising materials for light amplification. But band-edge state degeneracy demands multiple excitons to achieve population inversion increasing the lasing threshold and limits the gain lifetime. Researchers in Singapore have demonstrated that the amplified spontaneous emission (ASE) threshold is controllable in a device where CQD film is exposed to an external electric field. Specifically, singly charged CQDs lower the threshold due to the preexisting electron in the conduction band, while strongly enhanced Auger recombination in doubly charged CQDs stymies the ASE. According to the researchers the next big challenge in laser […]
Laser combo opens up futuristic terahertz technology
Physics World November 25, 2019 The terahertz region of the electromagnetic spectrum has been the least utilized owing to inadequacies of available sources. A team of researchers in the US (Harvard University, MIT, Duke University) has created a compact, widely frequency-tunable, extremely bright source of terahertz radiation: a gas-phase molecular laser based on rotational population inversions optically pumped by a quantum cascade laser. By identifying the essential parameters that determine the suitability of a molecule for a terahertz laser, almost any rotational transition of almost any molecular gas can be made to lase. Nitrous oxide is used to illustrate the […]
US Navy and Missile Defense Agency Megawatt Lasers by 2023-2024
Next Big Future August 8, 2019 In 2018, the US Navy and Missile Defense Agency had targeted demonstrating megawatt lasers by 2023-2024. The US Army recently had an announcement of a contract for 250-300 kilowatt lasers on a large truck by 2024. This means that four container-sized laser power systems could be combined on a Navy ship or at a Missile Defense base for a megawatt laser. A large US Army truck is the same size as a shipping container. A mobile 250-kilowatt laser has all the power, fuel and electronics for module that could be used for a megawatt […]