ultrashort pulse

Tuning a string to the right note: the laser pulse is adjusted so that harmonics play in unison at kiloelectronvolt frequencies. Visible light oscillates at hundreds of trillions of times per second.

A blacksmith pumps the bellows, and a slow stream of air turns into a sharp jet that can ignite a flame. Physicists treat light much the same way: they take a long laser pulse and squeeze it into a short, powerful flash.

It's like a sprint record: to break it, you need a perfect run-up. But for sub-millisecond pulsars, the run-up is too short. The fastest known pulsar, PSR J1748-2446ad, spins 716 times per second — faster than a kitchen blender. If it were the size of Earth, a point on its equator would move at about 0.24 times the speed of light. But why doesn't any pulsar spin even faster?

Picture a lighthouse on the shore at night. Its lamp is off almost all the time, but once every few days, for a split second, it blazes so brightly that the light is visible beyond the horizon.

For three days straight, a laser blasted a jet of gas, and every second it produced a beam of electrons with the energy of a tiny lightning bolt. Previously, such beams could only be produced in huge halls where the accelerator takes up an entire building. Now the whole setup fits in a room and ran without a glitch for 72 hours.

When a laser beam hits a gas, it tears electrons from atoms and accelerates them to nearly the speed of light. As these electrons fly through the plasma, they emit X-rays, like a glowing trail from a fast particle. In the new work, physicists made a single laser pulse create not one but two such trails in succession.

Two electrons that leave a metal needle tip almost simultaneously start to repel each other, like two people trying to squeeze through a narrow door at the same time. The closer they are, the more they get in each other's way.

A superconducting qubit is like a finicky musical instrument: until you tune it, you won't get a clean note. But even after tuning, the pitch drifts. The culprits are tiny defects in the material that physicists call two-level systems. They're like invisible cracks that appear and disappear, throwing off the processor's rhythm.

The galaxy is not a smooth lake but a pond with ripples. These ripples are created by ultralight dark matter (particles billions of billions of times lighter than an electron).

In the silent ocean of the Galaxy, mature civilizations have likely long chosen an unexpected strategy: instead of loud beacons, they scatter quiet fireflies — autonomous interstellar laser beacons, drifting in the void and dropping microsecond flashes. These 'seeds of contact' are not tied to their home stars and do not drown in their glow.

A typical laser is a cavity where light bounces between mirrors and gets amplified. But you can ditch the mirrors and make light circulate inside a tiny particle smaller than the light wave itself. That's how the new lasers work: nanoparticles of indium phosphide sitting on perfectly smooth gold.

A factory laser that cuts and welds metal on production lines has been made to work as a particle accelerator for the first time. Physicists took a standard ytterbium laser, its heart is a crystal the size of a palm, and turned its flashes into a tool for accelerating electrons to nearly the speed of light.

In the constellation Scorpius, 3,000 light-years from Earth, a dead star steals matter from a living one. A white dwarf in the system IGR J17014-4306 — a superdense carbon-oxygen ball with the mass of the Sun but the size of Earth — siphons hydrogen from a normal companion star.

Dark matter is an invisible substance that reveals itself only through gravitational effects: it bends the light of distant galaxies, much like an unseen window that alters the path of light rays.

In a benzene molecule, electrons buzz around the nuclei like a swarm of bees around a hive. But this swarm doesn't just hum: it pulses: every 856 attoseconds, the electron cloud completes a full oscillation cycle. The hive itself, the carbon nuclei, rocks more slowly, with a period of 36 femtoseconds.

The universe is permeated by an invisible substance, dark matter, whose gravitational influence is obvious, but whose composition remains a mystery. One hypothesis suggests it consists of ultralight particles so light that they exhibit wave-like behavior, forming a kind of cosmic ripple.

A pendulum swings with such precision that, had it been counting seconds since the Big Bang, it would have drifted by only half a second by today. That is the stability of the new portable ultraviolet laser — the heart of aluminum atomic clocks.

Usually, isotopes are separated by exploiting the difference in nuclear weight. That difference is tiny, like sorting grains of sand that differ by one hundredth of a millimeter. The new method ignores weight and instead looks at the nucleus's rotation: its spin. The laser hits the molecules twice with a short pause in between.

An ordinary laser emits narrow lines, like a string that sounds only one note. For spectroscopy, this is inconvenient: if a substance absorbs light between the lines, you might miss it.

A laser hits a target of thin wires, and within tens of femtoseconds (billionths of a billionth of a second) knocks out a stream of protons. These protons fly into a converter made of lithium and deuterium, where neutrons are born.

An ordinary camera flash lasts thousandths of a second. An attosecond pulse is a trillion times shorter — in the time it takes, light travels a distance smaller than the size of an atom. Such flashes act as an ultra-high-speed shutter: they freeze the motion of electrons, letting us see them jump between orbitals or take part in a chemical reaction.

An ordinary camera flash lingers for hundredths of a second, but for atoms, that's an eternity. Inside molecules, electrons jump in attoseconds: billionths of a billionth of a second. To capture that, you need a light pulse shorter than the event itself. Physicists take an electron beam in a linear accelerator and compress it so that individual bunches become thinner than a hair — in time.

An ordinary sheet of black phosphorus looks like a layered cake of atoms. If you shine a regular lamp on it, nothing special happens: the electrons sit still, like spectators in a dark theater. But a short laser flash lasting millionths of a billionth of a second shakes up that theater.

Light can carry information faster than any electronics. But usually, between a computer and a laser sits a digital-to-analog converter — a device that turns zeros and ones into electrical signals. It's the bottleneck. The new transmitter does away with this middleman.

A laser flash lasting 50 femtoseconds is like a shot that lasts one billionth of a second. In that time, light travels only 15 micrometers — less than the thickness of a human hair. But if you send such a flash through an amplifier, it starts to stretch like a rubber band and loses its sharpness.

A laser flash lasts a few femtoseconds — imagine a single instant stretched into a million parts. Such a flash mixes many colors, from red to violet. Instruments that measure the pulse shape often err: they see some colors well and others poorly, blurring the picture. The authors propose a simple fix.

The laser based on diamond converts almost half of the pump energy into bright yellow light — an efficiency of 47.7%, a record for such devices. But the main advantage is not the power, but the exceptional purity of the color: the beam is so monochromatic that it can be compared to a musical instrument playing just one note without the slightest wavering.

A shock wave in the Sun's corona is like the sonic boom from an airplane, except instead of air there is scorching plasma, and instead of sound there is a jump in density and magnetic field. On March 10, 2024, such a wave swept across the western part of the solar disk.

A laser beam strikes a gold-and-silver film for just a few nanoseconds — in that time, light travels less than a meter. At the point of impact, the metal boils, splatters, and freezes into a random pattern of tiny particles. Each pattern is as unique as cracks in ice or tree branches.

A spinning top that whirls so fast it completes 220 rotations in a single second: that's exactly what China's FAST radio telescope has caught. This is the pulsar PSR J1810-0623, a neutron star the size of a city but with more mass than the Sun.

The EDA2 radio telescope in the Australian outback is like a giant ear pressed against the sky. It listens to the cosmos at very low frequencies, from 50 to 250 megahertz, where ordinary telescopes can barely make out anything.

Rhythmic flashes of a lighthouse in thick fog: that's what searching for pulsars looks like. The lighthouse spins, and its beam periodically sweeps across the telescope. But the fog smears the light, making the period seem slightly different. If the same lighthouse was observed twice, you can compare: the periods should nearly match, and the smearing should be similar.

At the centers of many galaxies lurk supermassive black holes. From time to time they 'scream' — unleashing powerful X-ray flares. Scientists have long puzzled over the nature of these 'quasi-periodic eruptions'.

A camera that captures not light but a stream of electrons reflected off a crystal is a hybrid pixel detector. It can count every electron that hits it, generating almost no noise of its own. In normal mode, when the electron beam flows continuously, the detector works perfectly.

A laser pulse racing through plasma is like a runner carving a path through a crowd. It shoves electrons aside, leaving behind a rarefied channel, just as the crowd parts for a sprinter. In this channel, the crest of the light wave moves slightly faster than light in a vacuum, and it is this speed that determines how efficiently the pulse transfers energy to particles.

A laser beam usually quivers slightly, like a plucked string. In optical clocks, that quiver turns into timing errors. Engineers swapped the shaky light for steady light, and rubidium vapor clocks started ticking five times more evenly.

A ring the size of a dinner plate made an electron beam run in circles. Its diameter is 22 centimeters, and a full turn takes just 4.7 nanoseconds. To put that in perspective: in one second, such an electron would complete more than two hundred million laps.

At India's Gauribidanur Radio Observatory, 32 antennas that look like giant TV dishes are listening to the sky. They catch radio waves from pulsars — dead stars that spin at breakneck speed and blink like lighthouses. Previously, signals from these antennas were processed slowly and awkwardly.

A short laser pulse strikes the air, and a tiny lightning bolt flashes at the point of impact. It lives longer than you'd think: the bright glow is visible for half a millisecond, and a faint one for nearly twenty milliseconds.

A pulsar is a dead star spinning at breakneck speed, sending out radio pulses like a lighthouse. Usually these pulses arrive right on schedule, but occasionally there are true monsters among them — giant pulses that are thousands of times brighter than normal.