New discovery opens for breakthrough in laser technology


IMAGE: Assistant Professor Nicolas Volet
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Credit: Melissa Yildirim, AU Foto

The Department of Engineering, Aarhus University, has received a grant from the Independent Research Fund Denmark to investigate nonlinear effects in semiconductor lasers – a stepping-stone to enable next generation higher-order modulation in fibre optic networks.

One of the properties of lasers is the reduced spectral distribution of their optical emission as compared to other light sources.

However, this laser ‘linewidth’ can be greatly influenced by the environmental conditions, which deteriorate their performance when used outside the research lab.

Now, Assistant Professor Nicolas Volet, who leads the Integrated Photonics group at Aarhus University (AU) has received a DKK 2.9 million grant from the Independent Research Fund Denmark for a new ambitious project, that aims at solving the linewidth issue of diode lasers.

This issue is known to be one of the limitations in the deployment of coherent higher-order modulation transceivers for emerging applications; for instance, 5G wireless.

This project is based on a recent breakthrough discovery made by Assistant Professor Nicolas Volet and Dr. Holger Klein, Director of Chip Design at the US-based company OE Solutions America, Inc (OESA):

“We have discovered a method to effectively narrow the linewidth of a laser by a factor of up to 500, which is required to enable higher-order modulation formats in coherent communication, where information is encoded in the phase, amplitude and polarization of the lightwave signal. This unique approach can reduce the cost, size and power consumption compared to today’s laser technology,” says Dr. Holger Klein.

Nicolas Volet continues:

“Indeed, this discovery is extremely encouraging as it is expected to turn a notorious limitation of semiconductor lasers into an opportunity to increase optical network transport capacity and simplify their packaging for real-world applications. Our group will work closely with OESA’s

Boeing and General Atomics join forces on new laser weapon

WASHINGTON — General Atomics and Boeing are teaming up to build a new high-energy laser for air and missile defense, the companies announced Oct. 13.

Under the agreement, the companies will create a 100 kilowatt laser that will be scalable to 250 kilowatts, the companies stated in a news release. The weapon will be able to be employed as a standalone system or integrated onboard ground vehicles, ships and aircraft.

General Atomics Electromagnetic Systems will be responsible for the laser, batteries and thermal management system, while Boeing will create the beam director and software necessary for precision tracking and pointing the laser.

Although the companies did not specify whether the system is being built with a particular acquisition program in mind, the power levels that General Atomics and Boeing hope to achieve with their laser coincides with what the Army is aiming for in its High Energy Laser Tactical Vehicle Demonstrator program.

The service has already tapped Dynetics and Lockheed Martin to build the initial HEL TVD demonstrator — a 100-kilowatt-class laser that will be integrated with a Family of Medium Tactical Vehicles platform — but the service ultimately hopes to develop 250- to 300-kilowatt-class directed-energy weapons for future requirements.

The HEL TVD demonstrator is a pathway to fielding a directed energy weapon as part of the Indirect Fires Protection Capability (IFPC) Increment 2. The Army is in the process of putting laser fiber modules that buildup the components that get a laser up to 300 kilowatts, Lt. Gen. L. Neil Thurgood, the Army’s Rapid Capabilities and Critical Technologies Office (RCCTO) director told Defense News in a recent interview ahead of of the Association of the U.S. Army’s annual conference.

The Army will demonstrate the capability in fiscal 2022 on a truck.

Part of a broader Pentagon program, the HEL-TVD

Ultrafast fiber laser produces record high power

Credit: Pixabay/CC0 Public Domain

Researchers have developed an ultrafast fiber laser that delivers an average power more than ten times what is available from today’s high-power lasers. The technology is poised to improve industrial-scale materials processing and paves the way for visionary applications.

Michael Müller, a Ph.D. student of Prof. Jens Limpert from the Friedrich Schiller University’s Institute of Applied Physics and the Fraunhofer Institute of Institute for Applied Optics and Precision Engineering in Jena, Germany, will present the new laser at the all-virtual 2020 OSA Laser Congress to be held 12-16 October. The presentation is scheduled for Tuesday, 13 October at 14:30 EDT.

High power without the heat

In lasers, waste heat is generated in the process of light emission. Laser geometries with a large surface-to-volume ratio, such as fibers, can dissipate this heat very well. Thus, an average power of about 1 kilowatt is obtained from today’s high-power lasers. Beyond this power, the heat load degrades the beam quality and poses a limit.

To circumvent this limitation, the research team around Müller and Limpert created a new laser that externally combines the output of 12 laser amplifiers. They showed that the laser can produce 10.4 kW average power without degradation of the beam quality. Thermographic imaging of the final beam combiner revealed a marginal heating. Thus, power scaling to the 100-kW level could be accomplished by adding even more amplifier channels.

“In the future, high-power combined lasers not only will accelerate industrial processing, but also enable formerly visionary applications such as laser-driven particle acceleration and space debris removal,” said Müller.

The investigation of novel applications at that power level as well as the transfer of the laser technology to commercial systems is ongoing within the frame of the Fraunhofer Cluster of Excellence Advanced Photon Sources (CAPS), which foremost

Finding the right color to control magnets with laser pulses

Finding the right colour to control magnets with laser pulses
The spin can be seen as an elementary “needle of a compass”, typically depicted as an arrow showing the direction from North to South poles. Credit: Lancaster University

Scientists have discovered a new way to manipulate magnets with laser light pulses shorter than a trillionth of a second.

The international team of researchers, led by Lancaster and Radboud Universities, also identified the light wavelength or color which enables the most efficient manipulation. The finding is published in Physical Review Letters.

Magnets have fascinated people since ancient times, but until a hundred years ago the theoretical understanding of magnetism remained very elusive. The breakthrough in understanding occurred with the development of quantum mechanics and the discovery of the fact that each electron has an intrinsic magnetic moment or spin.

The spin can be seen as an elementary “needle of a compass,” typically depicted as an arrow showing the direction from North to South poles. In magnets all spins are aligned along the same direction by the force called exchange interaction. The exchange interaction is one of the strongest quantum effects which is responsible for the very existence of magnetic materials.

The strength of the exchange interaction can be appreciated from the fact that it generates magnetic fields 10,000 times stronger than the Earth’s magnetic field. Another manifestation of its strength is the fact that it can drive spins to rotate with a period of one trillionth of a second and even faster.

Manipulating the exchange interaction would be the most efficient and ultimately fastest way to control magnetism. To achieve this result, the researchers used the fastest and the strongest stimulus available: ultrashort laser pulse excitation.

However, in order to detect/observe the effect of light on magnetism one would need an ultrafast magnetometer—a device which would be able to trace

Revealing the reason behind jet formation at the tip of laser optical fiber — ScienceDaily

When an optical fiber is immersed in liquid, a high temperature, high speed jet is discharged. Researchers expect this to be applied to medical treatment in the future. Now, a research team from Russia and Japan has explored this phenomenon further and revealed the reasons behind the jet formation.

Lasers using a thin optical fiber and combined with an endoscope and catheter can be easily transported into deep areas of the body or inside blood vessels. Traditionally, affected areas or lesions are removed by generating heat inside the tissue through laser absorption — a process known as the photothermal effect.

Yet, hydrodynamical phenomena, such as microbubble formation or high-speed jet generation from the optical fiber, show immense medical promise.

The process of jet formation happens when the laser is irradiated to the water, causing the water to boil and a vapor bubble to form at the tip of the optical fiber. The vapor bubble grows until the laser energy absorbed in the liquid is consumed. Because of the surrounding cold liquid, condensation suddenly shrinks the vapor bubble.

Using a numerical simulation, Dr. Junosuke Okajima from Tohoku University’s Institute of Fluid Science, along with his colleagues in Russia, set out to clarify the jet formation mechanism. Their simulation investigated the relationship between the bubble deformation and the induced flow field.

When the bubble shrinks, the flow toward the tip of the optical fiber is formed. The flow deforms the bubble into the cylindrical shape. This deformation induces the collision of flow in a radial direction. This collision generates the jet forward. As a result of collision and jet formation, the vortex is formed at the tip of the deformed bubble and it grows larger.

“We found the jet velocity depends on the relationship between the size of the vapor bubble just