Phys.org November 14, 2024 An international team of researchers (Canada, USA – Brookhaven National Laboratory, University of Wisconsin-Madison, University of Rochester) demonstrated a laser beam acting like an object — the beam casts a shadow upon a surface when the beam is illuminated by another light source. They observed a regular shadow that could be seen by the naked eye, it followed the contours of the surface it fell on, and it followed the position and shape of the object (the laser beam). They used a nonlinear optical process involving four atomic levels of ruby. They were able to control […]
Tag Archives: Laser
Generating spin currents directly using ultrashort laser pulses
Phys.org September 13, 2024 An international team of researchers (USA – UC Berkeley, Lawrence Berkeley National Laboratory, France, Canada, Germany, Austria) measured the light-driven response of a magnetic multilayer structure made of thin alternating layers of cobalt and platinum at the few-femtosecond timescale. They observed how light rearranges the magnetic moment during and after excitation. The results revealed a sub-5 fs spike of magnetization in the platinum layer, which followed the shape of the driving pulse. They interpreted the observations as light-driven spin injection across the metallic layers of the structure. The light-triggered spin current was strikingly short, largely outpacing […]
A chip-scale titanium-sapphire laser
Nanowerk June 26, 2024 Ti:sapphire lasers are unmatched in bandwidth and tuning range, yet their use is restricted because of their large size, cost and need for high optical pump powers. An international team of researchers (USA – Stanford University, Belgium) demonstrated a monocrystalline titanium:sapphire-on-insulator (Ti:SaOI) photonics platform that enabled dramatic miniaturization, cost reduction and scalability of Ti:sapphire technology. Through the fabrication of low-loss whispering-gallery-mode resonators, they realized a Ti:sapphire laser operating with an ultralow, sub-milliwatt lasing threshold; through orders-of-magnitude improvement in mode confinement in Ti:SaOI waveguides, they realized an integrated solid-state optical amplifier operating below 1 μm. They amplified distortion-free […]
Accelerated discovery research unveils 21 novel materials for advanced organic solid-state laser technology
Phys.org May 16, 2024 To overcome the synthesis bottleneck in molecular discovery, an international team of researchers (Canada, USA – University of Illinois at Urbana-Champaign, industry, UK, Japan, Poland) developed a generalizable two-step one-pot protocol for assembling pentameric organic solid-state laser (OSL) gain materials from modular precursors, spanning over 150,000 target materials. The preparation of building blocks was distributed over the available experimental resources at four geographic locations. They found a total of 21 small-molecule emitters with improved emission gain cross sections compared with state-of-the-art OSL gain materials. The resulting data was fed into the central, machine learning–based experiment planning […]
Single-pulse real-time billion-frames-per-second planar imaging of ultrafast nanoparticle-laser dynamics
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 […]
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 […]