Tag Archives: Laser

Femtosecond Electronics With Plasmonic Hot Electron Nano-emitters

A team led by the Technical University of Munich (TUM) physicists Alexander Holleitner and Reinhard Kienberger has found success for the first time in generating ultrashort electric pulses on a chip. They made this possible by using asymmetric metal antennas only a few nanometers in dimension, then running the signals a few millimeters above the surface and receiving them in a controlled way.

Traditional electronics allow frequencies up to around 100 GHz. Optoelectronics can produce electric pulses at 10 THz range by applying electromagnetic phenomenon. The range in between them is referred as the terahertz gap, since components for signal generation, conversion, and detection have been remarkably difficult to achieve.

The TUM physicists succeeded in generating electric pulses in the frequency range up to 10 THz using tiny, so-called plasmonic antennas and run them over a chip. Researchers call the antennas plasmonic because of their shape, they amplify the light intensity at the metal surfaces. The shape of these plasmonic antennas is very important. They are asymmetrical in shape. One side of the nanometer-sized metal structures is more pointed than the other. When a lens-focused laser pulse excites the antennas, they emit more electrons on their pointed side than on the opposite flat ones. An electric current flows between the contacts — but only as long as the antennas are excited with the laser light.

Femtosecond near-field coupling of NIR pulses to THz stripline modes
Femtosecond near-field coupling of NIR pulses to THz stripline modes

In photoemission, the light pulse causes electrons to be emitted from the metal into the vacuum,

explains Christoph Karnetzky, lead author of the Nature paper.

All the lighting effects are stronger on the sharp side, including the photoemission that we use to generate a small amount of current. The light pulses were present in only a few femtoseconds.

Correspondingly short were the electrical pulses in the antennas.  In this way, a femtosecond laser pulse with a frequency of 200 THz could generate an ultra-short THz signal with a frequency of up to 10 THz in the circuits on the chip, according to Karnetzky.

The researchers chose sapphire as the chip material, because it cannot be excited optically and, thus, causes no interference. With an eye on future applications, they used 1.5-micron wavelength lasers deployed in traditional internet fiber-optic cables. Holleitner and his colleagues also made yet another amazing observation that both the electrical and the THz pulses were non-linearly dependent on the excitation power of the laser used. This means that the photoemission in the antennas is triggered by the absorption of multiple photons per light pulse.

Alexander Holleitner said,

Such fast, nonlinear on-chip pulses did not exist hitherto

Utilizing this effect he hopes to discover even faster tunnel emission effects in the antennas and to use them for chip applications.

Laser Beam Wireless Smartphone Chargers: The Next Big Thing

Cellphone chargers have been in existence for years and have grown from one stage to another. It started with the mobile phone traditional charger which had a USB interface, a DC converter, and a charging plug and now has expanded to a close-range inductive wireless charging. The commonly used inductive wireless charging is nice but limited, it still requires close contact with the charging pad making it offer little or no advantage to cable-based chargers. We have seen some potential long-range wireless chargers especially those from the PowerSpot, which in theory could charge up to 80 feet away. Among those technologies, charging with a laser beam is a possibility the research team from the University of Washington is evaluating.

Researchers from the UW’s (University of Washington), Paul G. Allen School of Computer Science & Engineering, have designed a laser system that can remotely charge your smartphones as quickly as a standard USB cable. They have embedded essential safety features which include a metal, flat-plate heat sink on the smartphone to dissipate excess heat from the laser, as well as a reflector based system to turn off the laser if a person tries to get in the way of the charging beam.

Shyam Gollakota, an associate professor at the UW’s Paul G. Allen School of Computer Science & Engineering said “We have designed, constructed and tested this laser-based charging system with a rapid-response safety mechanism, which ensures that the laser emitter will terminate the charging beam before a person comes into the path of the laser”. (more…)

Researchers Developed a Very Powerful Mini Synchrotron That Can Fit On A Tabletop

A synchrotron is a particular type of cyclic particle accelerator which is used to accelerate quantum level charged particles at a very high velocity, traveling around a fixed closed-loop path.

It is one of the first accelerator concepts to enable the construction of large-scale facilities because they are very efficient in beam focusing, bending, and splitting the beam into different components. The most powerful modern particle accelerators such as Large Hadron Collider (LHC) in Switzerland uses bigger versions of the synchrotron design.

Scientists design mini synchrotron that is only 4m long

A synchrotron is mainly used for the production of X-ray in many medical, engineering or industrial fields. Researchers at Eindhoven University of Technology and Delft University of Technology will build and develop a new scaled down version of a synchrotron which will even fit on a tabletop. The intensity of the X-ray radiation of this device will be just as powerful as the larger ones. Smart*Light” is the name of this new synchrotron which they officially took under research on 23rd January.

With Smart*Light, the consortium wants to build a ‘scaled down synchrotron‘. A compact and tunable X-ray source which is less than 4 meters long, which can be used in any lab. The potential of application for such a device is huge in medical diagnostics, high-tech industries, aircraft, car, and ship manufacturing.

Using Smart*Light there is the opportunity to analyze the chemical composition of old or new artworks layer by layer. This does not only have importance for conservation but, also for research into authenticity too.

The operation of this revolutionary X-ray source is based on the physical concept where X-rays are produced from collisions between LASER light and accelerated electrons. The theory is known as Inverse Compton Scattering, and has already been recognized for decades, but only recently has the necessary technology been modern enough to be developed.

Physicists Of University of Rochester Have Created Polariton – A Particle With Negative Mass

A group of researchers led by Nick Vamivakas from the University of Rochester has successfully produced particles which have negative mass in an atomically thin semiconductor material. According to the researchers, they have created a device that can generate LASER light using a significantly small amount of energy. All made possible with the help of this so-called negative mass particles. Quantum physicist Nick Vamivakas from Rochester’s Institute of Optics says,

It also turns out the device we’ve created presents a way to generate laser light with an incrementally small amount of power. Interesting and exciting from a physics perspective,

Polariton – A new particle that has negative mass

Mass is often observed as a resistance or response to a force. It’s harder to push and to stop a bowling ball than a marble because of the inertia associated with the mass of the object. All objects that are made of matter must have the property of ‘mass’. Even elementary particles without rest mass have something called relativistic mass. They react to an externally applied force in the way you expect them to. Particles with ‘negative mass’ however exhibit the opposite reaction to an applied force. They tend to move toward the applied force direction than to move away from it.

“That’s kind of a mind-bending thing to think about because if you try to push or pull it, it will go in the opposite direction from what your intuition would tell you,” says Vamivakas.

The device they created to make negative mass consists of two mirrors. It is used to make an optical microcavity to capture light at different colors of the spectrum depending on the mirror spacing. An atomically thin Molybdenum diselenide semiconductor is then implanted into the microcavity. This interacts with the captured light. The small particles called excitons from the semiconductor combine with photons of the trapped light to form polaritons. This process of an exciton giving up its identity to a photon to produce a polariton results in an object with negative mass associated with it. Simply means when you try to push or pull it, it goes off in the opposite direction to the way you would assume.

The most probable practical applications according to the researchers would be:

  •  The physics of negative mass: It will enrich the understanding of the reaction behavior of polaritons on electric fields and external forces.
  •  As a laser fabrication substrate: Due to polaritons, lasers would function more efficiently than the conventional ones. They will require much lower power input.

Further information is available in the journal Nature Physics, with the title Anomalous dispersion of microcavity trion-polaritons.

290Hz Narrowband Laser On Chip For Numeros Photonic Applications

Researchers from the MESA+ research institute at University of Twente have collaborated together with the provider company of the customized microsystem solutions “LioniX International” to achieve the lowest bandwidth tunable diode laser on a chip.

The newly-developed laser operates in the IR region at 1550 nm with an 81 nm tuning range, which means that users can choose the color of the laser themselves, within a broad range. The laser is an integrated InP-Si3N4 hybrid laser consists of two different photonic chips, optically connected to each other.

Photonics is a key technology that makes numerous other innovations possible. So that, scientists and researchers are making big efforts at this field including deployment of photons for transporting and processing data.

To make photonic chips function as efficient as possible, we need to be able to control the light signals. Which means that all transmitted light particles should have the same frequency and wavelength as possible. The university researchers have succeeded developing a tiny laser on a chip with a maximum bandwidth of just 290 Hertz.

Our signal is more than ten times more coherent – or clean – than any other laser on a chip.
~ Professor Klaus Boller, the research leader

This record laser will have countless applications especially in fiber optic communications that require high data rate. This applications includes 5G mobile networks, accurate GPS systems and sensors for monitoring the structural integrity of buildings and bridges.

You can find out more details here.

On-Chip Microwave Laser

Lasers are everywhere these days: at the checkout in the supermarket, in the CD player in the lounge – and quantum researchers need them to test qubits in the (future) quantum computers. For most applications, today’s large, inefficient lasers are a perfectly adequate solution, but quantum systems operate on a very small scale and at extremely low temperatures. Researchers, for the past 40 years, have been trying to develop accurate and efficient microwave lasers that will not disturb the ultra-cold and fragile quantum experiments. A team of researchers from the Dutch Technical University Delft have now developed an on-chip laser, which is based on the Josephson-effect. The resulting microwave laser opens the door to applications where microwave radiation with a low loss is essential. An important example is the control of qubits in a scalable quantum computer.

Lasers emit coherent light: the line width (the color spectrum) can be very narrow. A typical laser comprises a large number of emitters (atoms, molecules or charge carriers in semiconductors) in a oscillator cavity. These conventional lasers are generally inefficient and generate much heat. This makes them a challenge to use in low-temperature applications, such as quantum technologies.

The researchers constructed a single Josephson junction in an extremely small superconducting oscillator cavity. Here, the Josephson junction behaves like a single atom, while the micro cavity behaves like a pair of mirrors for microwave light: the result is a microwave laser on a chip. By cooling the chip down to ultra-low temperatures (less than 1 kelvin) a coherent beam of microwave light is generated at the output of the oscillator cavity. The on-chip laser is extremely efficient: it requires less than one picowatt to produce laser radiation.

The research paper can be read here.

Source: Elektor

Make Your Own Laser Scanning Microscope

A laser scanning microscope (LSM) is an optical imaging technique for increasing optical resolution and contrast of micrographs. It permits a wide range of qualitative and quantitative measurements on difficult samples, including topography mapping, extended depth of focus, and 3D visualization.

A laser microscope works by shining a beam of light on a subject in an X-Y plane. The intensity of the reflected light is then detected by a photoresistor (LDR) and recorded. When the various points of light are combined, you get an image.

Venkes had built his own DIY laser scanning microscope with a DVD pick-up, an Arduino Uno, a laser, and a LDR. He had also published an A-Z tutorial about making a similar device.

The result image consists of 256×256 pixels with resolution of 200 nm, about 1300 time enlargement, and it will not cost you a lot because you may have most of the parts. However, the scanning process is a bit slow, it may need half an hour for one image, and it is not crispy sharp.

The parts needed for this DIT LSM are:

  • 2 lens/coil parts of a laser pick-up (DVD and/or CD)
  • a bit of PCB
  • a piece if UTP cable (approx 15cm)
  • An Arduino UNO
  • An LDR
  • 2 x 10uF capacitors
  • 1 x 220 Ohm resistor
  • 1 x 10k resistor
  • 1 x 10k pot
  • 1 x 200 Ohm trim potentiometer
  • 1 breadboard
  • 1 switch
  • 1 3,5 mm jack plug
  • 1 audio amplifier
  • 1 laser with a good collimating lens
  • 1 piece of glass, a quarter of a microscope object glass or so to act as a semipermeable mirror
  • The under part of a ballpoint casing to put the LDR in

For the software side, an Arduino sketch is used to steer the lens, to read the LDR values, and to send information to a Processing sketch which will receive the data and translate it into an image.

You can find more details of this project with the source files at the project’s Instructables page. This video shows the device in action:

LASER TRIGGER FOR CHRONOGRAPH

I finished this laser wall trigger for my HIGH RESOLUTION AND ACCURACY CHRONOGRAPH. The purpose of this device is to generate the trigger start and stop impulses for my chronograph as soon as an object disrupts any of the laser beams.

LASER TRIGGER FOR CHRONOGRAPH – [Link]

Constant Current Laser Diode Driver Circuit Using OPA2350 OpAmp

The voltage-controlled current source circuit can be used to drive a constant current into a signal or pump laser diode. This simple linear driver provides a cleaner drive current into a laser diode than switching PWM drivers. The basic circuit is that of a Howland current pump with a current booster (Q1) on the output of a R-R CMOS OPA2350 op amp (U1). Laser diode current is sensed by differentially measuring the voltage drop across a shunt resistor (RSHUNT) in series with the laser diode. The output current is controlled by the input voltage (VIN) that comes from Trim pot PR1.

Features

  • Supply 3,3V DC
  • Load Up to 300mA
  • PR1 Trimpot Current Adjust

Constant Current Laser Diode Driver Circuit Using OPA2350 OpAmp – [Link]

RELATED POSTS

A Laser Treatment To Improve Paper Electronics

NanoEngineers” research group at Iowa University have been devoting efforts to use graphene and its amazing properties in their sensors and other technologies. Graphene has many extraordinary properties. It is about 100 times stronger than the strongest steel. It conducts heat and electricity efficiently and is nearly transparent.

Inspired by some recent projects about using inkjet printers to print multi-layer graphene circuits and electrodes, “NanoEngineers” have been working to move this research further by using the technology for a larger scale flexible, wearable and low-cost electronics. But there was some hurdles in improving the graphene conductivity after being printed and this process may damage the printing surface, such as papers, because of the high temperature or the use of chemicals.

Eventually, these engineers have led development of a laser-treatment process that allows them to use and improve printed graphene for electronic circuits and electrodes, even on paper and other fragile surfaces. The technology is said to show tremendous promise for a wide variety of fields including wearable sensors and thin film transistors with the ability of large-scale manufacturing.

It’s a three step process:

  • Graphene ink formulation: single layer graphene (SLG) powders were mixed with solvents and binders, bath sonicated, probe sonicated, and syringe filtered in order to produce a jettable graphene ink.
  • Inkjet Printing: The resultant graphene ink was syringed into the printer cartridge of a Dimatix Materials Printer and ejected via a piezoelectric nozzle in the subsequent printing process.
  • Laser Annealing:  A pulsed-laser processing of the electrodes using a Nd:Yag laser.
 Formulation, Printing, and Treatment, Source: <a href="http://pubs.rsc.org/en/Content/ArticleLanding/2016/NR/C6NR04310K#!divAbstract">Original Paper</a>
Formulation, Printing, and Treatment, Source: Original Paper

The engineers were able to remove ink binders and reduce graphene oxide by developing a computer-controlled laser technology that selectively irradiates inkjet-printed graphene oxide, Transforming the inkjet-printed graphene into a conductive material capable of being used in new applications is a huge breakthrough in nanotechnology.

More details are available at this paper on NanoScale journal.

Via:  ScienceDaily