Stack of Si3N4-LiNbO3 forming the integrated laser and integrated into test setup (d). (Credit: Snigirev et al., 2023)

Fast Adjustable Lasers Using Lithium Niobate Integrated Photonics

August 4, 2023 by Maya Posch 14 Comments

Making lasers smaller and more capable of rapidly alternating between frequencies, while remaining within a narrow band, is an essential part of bringing down the cost of technologies such as LiDAR and optical communication. Much of the challenge here lies understandably in finding the right materials that enable a laser which incorporates all of these properties.

A heterogeneous Si3N4–LiNbO3 chip as used in the study. (Credit: Snigirev et al., 2023)

Here a recent study by [Viacheslav Snigirev] and colleagues (press release) demonstrates how combining the properties of lithium niobate (LiNbO₃) with those of silicon nitride (Si₃N₄) into a hybrid (Si₃N₄)–LiNbO₃ wafer stack allows for an InP-based laser source to be modulated in the etched photonic circuitry to achieve the desired output properties.

Much of the modulation stability is achieved through laser self-injection locking via the microresonator structures on the hybrid chip. These provide optical back reflection that forces the laser diode to resonate at a specific frequency, providing the frequency lock. What enables the fast frequency tuning is that this is determined by the applied voltage on the microresonator structure via the formed electrodes.

With a LiDAR demonstration in the paper that uses one of these hybrid circuits it is demonstrated that the direct wafer bonding approach works well, and a number of optimization suggestions are provided. As with all of these studies, they build upon years of previous research as problems are found and solutions suggested and tested. It would seem that thin-film LiNbO₃ structures are now finding some very useful applications in photonics.

(Heading image: Stack of Si₃N₄-LiNbO₃ forming the integrated laser and integrated into test setup (d). (Credit: Snigirev et al., 2023) )

Accelerating Electrons To TeV Levels Using Curved Laser Beams

August 1, 2023 by Maya Posch 12 Comments

There are many applications for particle accelerators, even outside research facilities, but for the longest time they have been large, cumbersome machines, not to mention very expensive to operate. Here laser wakefield accelerators (LWFAs) are a promising alternative, which uses lasers to create accelerated particles along the wake in a plasma field. One of the major struggles has been with reinjecting the thus accelerated particles into another stage of a multi-stage accelerator, which would be required to obtain energies closer to one TeV. In this area researchers have now demonstrated a way around this, by using curved channels for the laser beams (paywalled paper) which inject the laser beam into the continuous cavity. Continue reading “Accelerating Electrons To TeV Levels Using Curved Laser Beams” →

“Room Temperature Superconductor” LK-99, Just Maybe It Could Be Real

August 1, 2023 by Jenny List 66 Comments

To have been alive over the last five decades is to have seen superconductors progress from only possible at near-absolute-zero temperatures, to around the temperature of liquid nitrogen in the 1980s and ’90s, and inching slowly higher as ever more exotic substances are made and subjected to demanding conditions. Now there’s a new kid on the block with an astounding claim of room-temperature and pressure superconductivity, something that has been a Holy Grail for physicists over many years.

LK-99 is a lead-copper-phosphate compound developed by a team from Korea University in Seoul. Its announcement was met with skepticism from the scientific community and the first attempts to replicate it proved unsuccessful, but now a team at Huazhong University of Science and Technology in China claim to have also made LK-99 samples that levitate under a magnetic field at room temperature and pressure. This is corroborated by simulation studies that back up the Korean assertions about the crystal structure of LK-99, so maybe, just maybe, room temperature and pressure superconductors might at last be with us.

Floating on a magnetic field is cool as anything, but what are the benefits of such a material? By removing electrical resistance and noise from the equation they hold the promise of lossless power generation and conversion along with higher-performance electronics both analogue and digital, which would revolutionize what we have come to expect from electronics. Of course we’re excited about them and we think you should be too, but perhaps we’ll wait for more labs to verify LK-99 before we celebrate too much. After all, if it proves over-optimistic, it wouldn’t be the first time.

Location of the Duvanny Yar outcrop on the Kolyma River, northeastern Siberia. (Credit: Anastasia Shatilovich et al., 2023)

Nematodes From The Siberian Permafrost Woke Up After A 46,000 Year Long Nap

July 31, 2023 by Maya Posch 25 Comments

The general consensus among us mammals is that if we get very cold, we die. Within the world of nematodes, however, they’d like to differ on that viewpoint. This is demonstrated succinctly after researchers coaxed a batch of these worms back into action after they had been frozen in Siberian permafrost for an estimated 46,000 years. The mechanism underlying this phenomenon is called cryptobiosis, which is essentially a metabolic state that certain lifeforms can enter when environmental conditions become unsuitable.

In the case of nematodes, they hold a number of records, with a group of them having survived the STS-107 Space Shuttle Columbia in 2003 when it broke up during reentry, making it the first known lifeform to have achieved such a feat. During arctic experiments it was found that these roundworms can withstand intracellular freezing even while active depending on its diet. Continue reading “Nematodes From The Siberian Permafrost Woke Up After A 46,000 Year Long Nap” →

Timeline of the universe. A representation of the evolution of the universe over 13.77 billion years. The far left depicts the earliest moment we can now probe, when a period of "inflation" produced a burst of exponential growth in the universe. (Size is depicted by the vertical extent of the grid in this graphic.) For the next several billion years, the expansion of the universe gradually slowed down as the matter in the universe pulled on itself via gravity. More recently, the expansion has begun to speed up again as the repulsive effects of dark energy have come to dominate the expansion of the universe. The afterglow light seen by WMAP was emitted about 375,000 years after inflation and has traversed the universe largely unimpeded since then. The conditions of earlier times are imprinted on this light; it also forms a backlight for later developments of the universe. (Credit: NASA)

ESA’s Euclid Space Telescope And The Quest For Dark Energy

July 31, 2023 by Maya Posch 30 Comments

Most of what humankind and other mammalian species on Earth experience of the Universe is primarily restricted to the part of the electromagnetic spectrum which our optical organs can register. Despite these limitations, we have found ways over the centuries which enable us to perceive the rest of the EM spectrum, to see both what is incredibly far away, and what is incredibly small, to constantly get a little bit closer to understanding what makes the Universe into what we can observe today, and what it may look like in the future.

An essential element of this effort are space telescopes, which gaze into the depths of the Universe with no limitations imposed by the Earth’s atmosphere, or human activity. Among the many uses of space telescopes, the investigation of the expansion of the Universe is perhaps the most fascinating, as this brings us ever closer to the answers to the most fundamental questions about not only its shape, but also to its future, which may include hitherto unknown types of matter and energy.

With the recently launched Euclid space telescope, another chapter is being opened in the saga on dark energy and matter, and their nature and effects on the Universe, as well as whether they exist at all. Yet how exactly do you use a space telescope to ferret out the potential effects of dark energy?

Continue reading “ESA’s Euclid Space Telescope And The Quest For Dark Energy” →

Fiber-Infused Ink Allows 3D-Printed Heart Muscle To Beat

July 29, 2023 by Maya Posch 7 Comments

Illustration from Anatomy & Physiology, Connexions Web site. http://cnx.org/content/col11496/1.6/, Jun 19, 2013.

What makes a body’s organs into what they are is more than just a grouping of specialized cells. They also need to be oriented and attached to each other and scaffolding in order to create structures which can effectively perform the desired function. A good example here is the heart, which requires a large number of muscle cells to contract in unison in order for the heart component (like a ventricle) to effectively pump blood. This complication is what has so far complicated efforts to 3D print complex tissues and entire organs, but recently researchers have demonstrated a way to 3D print heart muscle which can contract when stimulated similarly to a human heart’s ventricle.

At the center of this technique lies a hydrogel that is infused with gelatin fibers. Using a previously developed Rotary Jet-Spinning technology that was reported on in 2016, a sheet of spun fibers was produced that were then cut up into micrometer-sized fibers which were dispersed into the hydrogel. After printing the desired structure – taking into account the fiber alignment – it was found that the cardiomyocytes (the cells responsible for carrying the contractile signal in the heart muscle) align along the thus laid out pattern, ultimately creating a cardiac muscle capable of organized contraction.

These findings come after many years of research into the topic, with e.g. Zihan Wang and colleagues in a 2021 paper reporting on the challenges remaining with 3D printing cardiac tissue, yet also the massive opportunities that this could provide. Although entire heart replacements (via therapeutic cloning with the patient’s own cells) might become possible too, more immediate applications would involve replacements for damaged cardiac muscle and other large structures of the heart.

Would We Recognize Extraterrestrial Technology If We Saw It?

July 28, 2023 by Maya Posch 92 Comments

There’s a common critique in science fiction series like Star Trek about the extraterrestrial species not looking ‘alien’ enough, as well as about their technology being strangely similar to our own, not to mention compatible to the point where their widgets can be integrated into terrestrial systems by any plucky engineer. Is this critique justified, or perhaps more succinctly put: if we came across real extraterrestrial life with real extraterrestrial technology, would we even notice? Would an alien widget borrowed of an alien spacecraft even work with our own terrestrial spacecraft’s system?

Within the domain of exobiology there are still plenty of discussions on the possible formation and evolutionary paths conceivable within the Universe, but the overarching consensus seems to be that it’s hard to escape the herding effect of fundamental physics. For lifeforms, carbon-based chemistry is the only reasonable option, and when it comes to technology, it’s hard to not end up at technology using the same physical principles which we presume to exist across the Universe, which would practically guarantee some level of interoperability.

What’s notable here is that over the past years, a number of people have claimed to have observed potential alien technology in our Solar System, in particular the ʻOumuamua asteroid in 2017 and a more recent claim by astrophysicist Abraham Loeb regarding an interstellar meteor that impacted Earth in 2019, which he says could be proof of ‘alien technology’. This raises the question of whether we are literally being pummeled by extraterrestrial spacecraft these days.

Continue reading “Would We Recognize Extraterrestrial Technology If We Saw It?” →