Tag Archives: Lasers

Meet MASER, Laser’s High Powered Older Cousin

Lasers have been around for a long time now. They are so ubiquitous, you can find them in computers, hunting rifle scopes, medical devices, and even a child’s play thing. Believe it or not, about 50 years ago, most of the devices that use lasers had not even been conceived of. What you also may not know is that the laser has an older cousin that has been sitting quietly on the shelf for nearly 50 years. It’s name is MASER.

Where LASER is an acronym for Light Amplification by Stimulated Emission of Radiation, MASER is Microwave Amplification by Stimulated Emission of Radiation. So basically, instead of visible light, the MASER produces a concentrated beam of microwaves. Though MASERs were actually developed first, the conditions it took to create them were very difficult to achieve. For instance, they required nearly absolute zero temperatures to operate. New research done by Britain’s National Physics Laboratory (NPL) and Imperial College, London has resulted in a solid-state room temperature MASER. The research has been published in the journal Nature and was led by Dr. Mark Oxborrow.

MASER
The MASER core via NPL Youtube Video

Up until now, MASERS were only a thing of physics labs and research facilities. The only real practical use for them was in atomic clocks. Now that the NPL scientists have been able to remove the extreme environmental conditions from the MASER, more practical applications are likely to be introduced. According to an NPL press release, “MASERs could be used to make more sensitive medical instruments for scanning patients, improved chemical sensors for remotely detecting explosives; lower-noise read-out mechanisms for quantum computers and better radio telescopes for potentially detecting life on other planets.” In the embedded video below, Dr. Oxborrow gives a brief description of the MASER and shows the core they invented to make all of this possible.

[Video Link]

Conventional MASERs work by directing microwaves at crystals such as ruby. Unfortunately, this material requires extremely low temperatures, as well as a lot of costly magnets to work. The NPL scientists discovered a new type of crystal called p-terphenyl crystal. This crystal is “doped” pentacene which allows it to be used to amplify microwaves at room temperature. There are still challenges facing the MASER. One, is to get it to work continuously instead of in pulses. The other, is to get it to operate in a broader range of microwave frequencies to make it more useful. To keep up with the MASER research, visit http://www.npl.co.uk/news/maser.

Introducing: The World’s Most Powerful Laser Which Is To Be Used For Accelerating Particles

In the world of high-powered lasers, a new kid is on the block. And it’s damn powerful! The Berkeley Lab Laser Accelerator (BELLA) has developed a laser which can deliver a huge 1 petawatt of power in a single pulse which lasts for 40 femtoseconds. It can do this once every second, making it a one-pulse-per-second laser.

Blinding

Strange units

Now, what do those terms with the funny units mean?

A petawatt is a million billion watts – a quadrillion watts, in everyday language. And a femtosecond is a quadrillionth of a second – one part of 1015 parts in a second! No other laser in the world has this high a peak power and still function at that high a pulse rate (1 pulse per second). This is now officially a world record – this is the world’s most powerful laser.

Building an accelerator

Enter the Laser and Optical Accelerator Systems Integrated Studies (LOASIS) program and there is where BELLA really scores. The really powerful laser is a prototype for the ultimate laser that will be built to accelerate particles for an accelerator. This accelerator will use the laser’s energy to speed up electrons and protons.

Conventional particle accelerators, the LHC included, uses electric fields to accelerate the charged particles, while magnetic fields bend them. The laser uses its intense heat to generate plasma. This plasma has a lot of free electrons swimming around and they can absorb energy and be accelerated to very high speeds. The trick is to make all of these electrons accelerate in phase.

Says Wim Leemans of Berkeley Labs Accelerator and Fusion Research Division (AFRD), the dept. responsible for the construction and maintenance of the LOASIS:

BELLA will be an exceptional tool for advancing the physics of laser and matter interactions. The laser’s peak power will give us access to new regimes, such as developing compact particle accelerators for high-energy physics, and tabletop free electron lasers for investigating materials and biological systems.

BELLA laser will be used to build the world’s first plasma accelerator, which will be able to accelerate electrons to 10 GeV. This is about a thousandths of what the LHC produced, but it’s still very high energy achieved on a device a millionth of the size of the LHC. This successful preliminary test of the BELLA laser was part of the LOASIS test which is due to start this autumn.

Observed: Atomic Movements Inside Molecule For The First Time Ever!!

Ultra-fast movements of atoms within a molecule have been observed for the first time ever, courtesy scientists led by Prof. Louis Di Mauro, a professor of physics at Ohio State University. The principle is simple: Shining light onto a molecule will excite the electrons of the atoms in the molecule. These electrons can then be the probe for the atomic movements within the molecule. The team used oxygen and nitrogen molecules, the simplest diatomic molecules you can get.

Procedure:

The team shone light on the molecules, which knocked out a single electron from one of the two atoms. This electron can then be reabsorbed into the molecule, but when that happens, it will interact with both the atoms. This interaction can be used to track back the potential between the atoms. Thus, we can probe the potential landscape within the molecule, using the interaction information of the electrons.

To probe the movement of the electrons, the team used an ultrafast laser, with a pulse width of 50 femtoseconds. That a millionths of a billions of a second!! Light travels just 300 nanometers in that time! 

The technology required to image complicated molecules like protein is still far away.

Atomic interactions inside molecules may augur in great fortunes in the soon-to-come future. 

Creating Real 3D Images In Air By Making Plasma With Lasers! [With a Video]

This is just too cool. Forget about the 3D optical illusion that is used to show 3D movies, this 3D technology is for real! The True 3D display technology creates plasma at specific points in air (or under water) and hence forms a true 3D picture. The plasma is formed by a high frequency laser, powerful enough to create pockets of plasma that give off light.

Making a plasma show!

The technology is developed by Burton and improves upon a previously known version of 3D technology. The researchers point out that this is the first time you can show pictures without any screen!

This system can create about 50,000 dots per second, and its frame rate is currently about 10-15 fps. But we’re working to improve the frame rate to 24-30 fps.

Presently, they are testing the system with a green laser in water, as it takes much less energy to make plasma in water than in air. The results are definitely positive. They plan to use a higher power laser to make such images in air! The next step would be to generate multiple colors using red, blue and green lasers. The final step would be to use this system to screen a short film!

This following video (Courtesy: diginfo.com) should be self-explanatory. Warning: When I first saw it, my mind was completely blown! Enjoy.

Has the time for a redefinition of a 3D film imminent in a few years?

Source and More Info here:  http://www.diginfo.tv/2011/11/14/11-0231-r-en.php

Anti-Matter Trapped: CERN Scientists at ALPHA Trap Anti-Matter For Record 1000 Seconds

Some people might liken it to the situation described in Dan Brown’s novel Angels and Demons. CERN scientists trapped  dangerously slippery anti-matter for a record 1000 seconds (or 17 minutes), a huge achievement in terms of anti-matter confinement.

This remarkable feat was achieved by scientists working on the Anti-hydrogen Laser Physics Apparatus (ALPHA). 1000 seconds is a huge improvement (almost 4 orders of magnitude greater) than the previous best, of 172 millisecond (i.e. 0.172 s). This new trapping ability will allow physicists to design new experiments that take a closer look at the properties of anti-matter. Theoretically, anti-hydrogen should occupy the same quantum energy levels as normal hydrogen, but this has never been theoretically confirmed. Also this will settle many long standing problems like Baryon Asymmetry and give insights into CP violation, or even CPT violation. There is also hope of cooling these anti-atoms to temperatures low enough so that gravitational effects become significant.

ALPHA Facility
An Overview of the ALPHA facility

Confining neutral (or even charged) particles cannot be done using electric fields. Magnetic fields are used. A Penning trap is used to produce and hold the anti-hydrogen produced. These are then held in a magnetic field with a three-dimensional minimum. (See figure)

Simulation as to how a magnetic trap potential looks. (Made by author using Wolfram Mathematica)
This shows the basic layout. Notice the streams of positrons and anti-protons fired from the two sides, which form anti-hydrogen. A magnetic field of 1T (which is HUGE) is applied by means of an external solenoidal coil (not shown here). Silicon detector line the wall of the trap. (Courtesy: Arxiv paper)
This shows the cross-section of the field profile. (A): A longitudinal cross-section is taken. The bright lines represent field of a certain strength. (B): The transverse cross-section is taken. (Courtesy: Arxiv paper)

It is clear that deeper the well (see the second figure from the top), lesser is the probability of the atoms escaping. The ALPHA collaboration has gone up to 309 atoms from a measly 38 that it started off with. Most anti-hydrogen atoms were in their ground state as expected.

An exciting question is whether anti-matter is attracted or repelled by gravity i.e. whether it should fall up or down. (By all means, physicists expect it to fall down! Nature is not that asymmetric. However, enough anti-matter has not been observed to fall down or up.)

We’ll just have to wait and watch.

Super Fast: Teams Develop Optical Fiber Cables That Carry Data Faster Than 100 Terabits A Second

Now that’s fast. Two independent groups have developed fiber optic cables capable to transferring data at an incredible rate of 100 Terabits per second. This unbelievable speed is far greater than anything available today.

Just to give an idea of what 100 Terabits (or about 12 Terabytes) per second means, take this example. An HD movie with a running time of about 2 hours has a size of about (or less than) 4 Gigabytes (GB). 1 Terabyte (or TB) equals roughly 1000 GB. Thus, you could download 250 HD movies, each running for 2 hours, in one second!! That’s a running time of 500 hours, there being 720 hours in one month! Even if you watched 5 of these movies a day (an unrealistic rate, by any estimate), you could go on like that for 50 days after just 1 second of download.

Even the busiest optical line in the world, that between Washington D.C. and New York, experiences a maximum speed of a few Terabits per second.

Optical cable
Super-fast!

 

How they did it

The first team, from Japan’s NIICT, led by Jun Sakaguchi, adopted a simple strategy. They developed an optical fiber having seven optical cores, completely insulated from one another. Each of these could carry 15.6 TBits/s. The information would then be read and processed at the end of the communication line. The total speed thus achieved was 109.2 TBits/s.

The second team, from NEC Global’s R&D, led by Dayou Quan, took a more complicated route. They fed in packets of information from 370 lasers (as light pulses) into a single optical fiber core. The lasers each had different positions in the Infrared Spectrum, as well as different polarizations, amplitudes and, importantly, phases. This ensures that the signals don’t interfere with each other. Using this technique, the team transferred data across 165 kilometers (!) at a speed of 101.7 Tbits/s.

New World?

The path is being paved for a world which craves for more data and information. Even then, 100 Tbits/s is more than anyone asked for or needs. Is this the beginning of a world where all forms of entertainment come in 3-D?

Big Lasers: Czech Republic To Build The World’s Most Powerful Laser by 2015

Lasers are the hottest things in physics. Now, the Czech Republic intends to make it even hotter, by building the world’s most powerful laser an exawatt beast – by 2015. This is a part of the European Union’s commitment to remain at the forefront of research in modern physics. The project will be undertaken by a facility under the name of European Light Infrastructure ELI a collaboration spanning 13 EU countries. According to their website, ELI initially intends to set up three sites in Prague.

laser

What is exawatt?

The power (i.e. amount of energy per unit area per second) delivered by a laser is measured in watt’. Since lasers generally have very high power ratings (over a small surface they dump in a lot of energy), higher units like kilowatt (thousand watt) or megawatt (million watt) are used. Exawatt is a million million megawatts, an unbelievably high amount of energy!

The catch with time

The catch with lasers is that they can emit a lot of energy in a single short pulse, or they can continuously emit energy with low intensity. Thus, powerful lasers are always pulse lasers, having short pulse times. The exawatt laser, which is slated to become operational by 2015, will have a pulse time of just 1.5 x 10-14 s. While that might look really small (and it is!), but experimentalists do conduct high-energy physics experiments at these time-scales.

Where it will stand

The powerful lasers available today have wattage in the range of terawatt (which is a million megawatts). The most powerful lasers push that to 100 terawatts, nearing a petawatt (a thousand terawatt). This laser by ELI will raise the bar by thousand times that amount!

ELI
The ELI facility at Czech Republic

What are its uses?

Its uses in scientific research purpose primarily probing reactions occurring at super fast rates. The laser may also be used for future cancer treatment and nuclear waste management.

This is the first real big research project to be funded by EU in an Eastern European country and this will also be one of the most expensive ones, costing about 700 million Euro.

More Efficient Engines: Lasers Replacing Spark Plugs In Cars?

A team of Japanese researchers has come up with ceramic lasers that can be triggered every nanosecond, giving powerful blasts  that hold their intensity over very short ranges. They are just 9 mm in diameters. They might find use in the unlikeliest of places the engine of a car, sounding the death knell for spark plugs and twitchy car engines.

Spark Plug RIP

A moment’s thought might help one describe this idea as innovative’, rather than outlandish’, though, in fact, it is both. Let’s see why.

Lasers are extremely accurate and can deliver ignition pulses, precise in both time and space. They will deliver it at the right spot and also time them as needed. The very low response time will make engines more sensitive to what the driver instructs them to so. This will make a huge difference in the stopping time of a vehicle, when, often, a second or two matters a lot.

Laser

Since lasers can be made to point accurately at any place, they can be designed to produce the ignition right in the middle of the chamber, which can then spread out evenly. Spark plugs deliver asymmetric ignition and, thus, some energy is wasted, since the force in the radial direction is not quite balanced. Lasers will eliminate such imbalances and give more push for the same ignition, concentrating all the force to act in the direction that matters.

Extremely important is the ability of lasers to produce very high temperatures within small spaces. This will be able to ignite a fuel-air mixture containing much less fuel. Spark plugs, producing much lesser temperatures, need higher proportion of fuel to ignite. Fuel guzzlers may become a thing of the past.

Lasers will also come with a lower maintenance cost, so in the long run, they’ll save a lot of money for the owner of the car. They are also expected to make significant cuts in carbon emissions of engines.

Leaner, cleaner and fitter, lasers promise to replace spark plugs in engines of not too distant future.

Quantum Breakthrough: Matter Guided through Optical Guides, Just Like Light Through Optical Fibers

It’s atoms now, and not only light. Researchers at ARC Center of Excellence for Quantum Atom Optics, Research School of Physics, ANU, have successfully guided supercooled Helium atoms through an optical guide made of a laser beam. This is the first ever successful at guiding matter waves.

Speckles, Modes and the Rest of the Basics:

When light is guided in an optical fiber, there can be many modes of transmission. These modes interfere and produce a speckle pattern’ on the screen after emerging from the fiber. The light can be adjusted so as to eliminate the speckle, which indicates that the light is in a single mode, or technically, coherent’. Scientists say that the light has the same phase factor’ throughout, which doesn’t vary with time.

Laser Speckle
Laser Speckle, the indication of multiple modes

There are many other coherent substances that can be made. One of them is known as the Bose-Einstein Condensate (BEC). During the 1920’s, Satyendranath Bose and Albert Einstein worked out the statistics of bosons and showed that, if cooled enough, they can be made to fall into a single giant ground state. In this state, any addition to the number density of the particles makes more particles fall into the ground state. This is, thus, called a Condensate’, appropriately named, Bose-Einstein Condensate’.

Bose Einstein Condensate
Bose-Einstein Condensate (The peaks indicate the number density of atoms in the ground state. Note how it rises with fall in temperature) (nK=nanoKelvin) (Courtesy: Colorado University)

BEC is a remarkable state of matter. Thousands of bosons (for example, Helium atoms) can condense and behave like a single super-atom. BEC physics is one of the richest and the present interest is primarily because BEC physics mimics that of superconductors.

The guiding of matter waves

What the team of researchers has achieved is this: They took a bunch of atoms and trapped them. Then,  they irradiated this with laser light pointing downwards towards gravity. This produced a speckled pattern.

As Ken Baldwin, one of the team members, reports

We have shown that when atoms in a vacuum chamber are guided inside a laser light beam, they too can create a speckle pattern – an image of which we have captured for the first time.

The BEC guide
The schematic for the BEC guide used by the researchers. (Courtesy: Nature)

The atoms were cooled to lower and lower temperatures, until the atoms formed the BEC. Since the BEC is a coherent state, with the lowering of the intensity of the laser light, the speckled pattern suddenly disappeared.

Team leader, Dr. Andrew Truscott, reported that:

The atoms … behaved more like waves than particles, forming a Bose-Einstein condensate (BEC).   When the BEC was loaded into the guide, the speckle pattern disappeared, showing that just one mode was being transmitted the single quantum wave.

Looking at the images and by measuring the arrival times of the atoms on the Multi-Channel Plate (MCP), the researchers could differentiate between a speckled, multi-mode transmission and a smooth, single-mode transmission.

Achievement:

Earlier it was only light that could be guided in a wave guide (here, the optical fiber). No longer is that true. This breakthrough demonstrates that it is possible to guide atoms in a BEC state in an optical guide (not glass). This will allow higher precision atom-interferometers.

Laser Cooling

One of the coolest things in physics is used as a common tool to make things really cold. Lasers are used to cool a bunch of atoms to extremely low temperatures, temperatures in the micro-Kelvin range. Extremely successful, laser cooling is surely one of the hottest topics in Physics.

Firstly, let’s note few important points:

  1. The ‘temperature’ of a substance is the average kinetic energy of the constituent atoms/ molecules. This is the definition. And, yes, this is exactly what we measure with a thermometer. Thus, in short, the faster the atoms in a substance move, the higher its temperature.
  2. There is a well known effect called the Doppler Effect. If you move towards a light source (or equivalently, if the source moves closer to you) the frequency of light you see goes up (“blueshift”). This is, obviously, a velocity dependent phenomenon. The faster you move, the more the shift in observed frequency. Similarly, if you move away from the source, the frequency goes down (“redshift”). So if a stationary observer observes green light, an observer moving towards it might see a blue light, while the observer moving away may see a red light.
  3. A substance absorbs energy only at discrete and specific frequencies of radiation. For example, if a substance absorbs at a frequency of red light, radiating it with a light of slightly lower wavelength will not cause it to undergo any transition. This light will not be absorbed. This is due to the quantum nature of the energy levels of the atoms.
  4. Light is made up of tiny packets of energy called photons. Each of these photons carries only one value of energy, dependent on the frequency of the radiation. The higher the frequency, the higher the energy. Also, photons carry momentum. Momentum for a photon is equal to its energy.
Doppler Effect
Frequency tends to increase as one moves towards source: Doppler effect
Doppler Shift in Spectra
Doppler Effect: Notice the bands and how they are shifted either to blue or to red

Armed with these points, we can finish off the explanation for laser cooling in a few lines. Take an atom and irradiate it with light with a frequency slightly lower than the one it would absorb. The light would just bounce off without any absorption (point 3). Now say that the atom is moving towards the laser. The frequency it will see is greater than the static laser frequency (Point 2). This higher frequency is now good enough for absorption.

Imagine two lasers irradiating the atom from opposite directions. One laser forces the atom to bounce off towards the other laser. This induces absorption.

Schematics of laser cooling
a) A group of atoms is irradiated. Assume it moves to the right. b)Then, it encounters the laser beam which seems a bit more blue than its static state. It absorbs radiation. c)It releases the radiation losing momentum and energy and is thus 'cooled'. d)The process is repeated.

Now this excited atom can release energy as a photon. The momentum it loses due to the emission of this photon lowers the kinetic energy. Thus, the kinetic energy decreases. But this is basically a lowering of temperature (point 1). Lo and behold, we have cooling.

Now this excited atom can release energy as a photon. The momentum it loses due to the emission of this photon lowers the kinetic energy. Thus, the kinetic energy decreases. But this is basically a lowering of temperature (point 1). Lo and behold, we have cooling.