Category Archives: Laser Research

Dennis Gabor and the Hologram Theory

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When questioned about the future, we often respond with painted Hollywood-influenced concepts and inventions. However, we have yet to truly understand the impact of thought and how often these made-up scenarios influence young scientists and engineers worldwide. One truly futuristic concept of the past that has yet to develop into a mainstream household commodity is the hologram. Having been first proposed in 1947 by Dennis Gabor, a Hungarian electrical engineer and physicist, the hologram continues to perplex modern technology companies with its physical makeup and complex function. Gabor invented the method of storing on photographic film three-dimensional (3-D) images of the information pattern encoded on a beam of light. He later became the recipient of the 1971 Nobel Prize in Physics for his outstanding Hologram Theory and the development of holograms.

The term hologram derives from the combination of the Greek words holos, meaning whole, and gramma, meaning anything written. In essence, a hologram or electromagnetic energy hologram is defined as the whole, holos, 3-D message contained or written in a single beam of light, gramma – this compares to the partial message that’s contained in a two-dimensional (2-D) photograph and is the major feat which distinguishes 2-D imaging from 3-D. However, technology wasn’t yet able to produce such mechanisms when Gabor first came up with his Hologram Theory in 1948 and it wasn’t until the invention of the laser in 1960 that experiments with this theory were able to commence.

Processes within holography share similarity to those within photography however there are major differing factors. As a whole, holography is a two-stage process. The first stage consists of recording a hologram in the form of an interference pattern or pattern showing the interaction of waves that are coherent with one another due to the two waves functioning at the same frequency. This feat is similar to the iridescent pattern or the mixing of colors that is visible to the naked eye in floating soap bubbles or atop an oil film. The second stage of holography requires the hologram to act as a diffraction grating or medium that splits, or diffracts, light into multiple beams that travel in different directions while the image of the subject is then reconstructed in order to display the final holographic image; the diffraction process gives each beam the ability to reconstruct the entire object. During this process, both intensity as well as the phase of a light wave are being recorded thus producing a 3-D picture of an object that can be viewed from several angles. An example of a modern technology that repeatedly exercises the benefits of holography lies within the medical field and is termed x-radiation or the x-ray.

Meanwhile, conventional photography uses a process that is much more simplified. Unlike holography, light intensity is the only medium that is recorded thus leading a photographing device to produce 2-D figures of an object rather than the aforementioned 3-D. This is also why figures within photographs can only be viewed from one angle at a time rather than showing a full 360-degree image.
Both of these image producing mediums, photography and holography, are light dependent methods of storing information. This means that both methods record information contained in the visible light region, the optical region, of the electromagnetic radiation spectrum and that lasers are imperative in the advanced processes of these functions. As a medium itself, the laser is an indispensable coherent light source that makes both conventional photography and optical holography possible.

An interesting fact about the hologram is that the general concept plays into the famous Holographic Principle which was first introduced by the Dutch theoretical physicist Gerardus’t Hooft and Leonard Susskind circa the 1980s. This principle states that 3-D spaces can be mathematically reduced to 2-D projections and that the 3-D universe we continuously experience and perceive is merely the “image” of a 2-D one. Many physicists strongly believe that the universe is simply one giant hologram. Even though we have come to see the importance in certain mediums that use holography, such as x-rays, we still question the importance of individual holograms. As unfamiliar with the concept as many consumers may be, this sub-field of laser technology may slowly start to find its place within our everyday lives as device-based learning begins to flourish.

With smartphone technology developing at such a rapid pace, it’s safe to assume that these hand-held devices may begin to experience changes within their hardware systems. Samsung has since advertised a smartphone prototype which displays holographic images “mid-air” via the cell-phone screen.

Young scientists and engineers worldwide are becoming more and more interested with holograms and all that is certain is the fact that major changes with this specific use of technology are currently underway and may even come to stare us in the face within the next five to ten years.

Using Lasers to Detect Mutant Bacteria

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Using lasers to detect harmful bacteria is a topic of interest to more than a few researchers. Previously, we highlighted developments where lasers were used to identify contaminated food, which may be used to stop food poisoning long before contaminated food hits a dinner plate. Now, researchers at Purdue University have developed a laser tool that not only detects harmful bacteria, it also recognizes mutated strains.

The tool, known as bacteria rapid detection using optical scatter technology or BARDOT, works similar to the TDLAS method developed at the Institute of Information Optics, Zhejiang Normal University, Jinhua, China. BARDOT scans colonies of bacteria, revealing patterns created the bacterium. Each type of bacteria has a unique “scatter pattern” which is used to help identify the strain, against known scatter patterns. Like TDLAS, bacterium such as salmonella, E. coli, and listeria can be identified in a short period of time.

What separates BARDOT from TDLAS and other bacteria-detecting scans? According to researchers Arun Bhunia and Atul Singh, BARDOT is also able to detect genetic mutations in listeria, and at the same rate that it detects other strains of bacteria. Even more intriguing is the fact that BARDOT can detect the mutations faster than scientists can physically analyse the bacteria, themselves. Where traditional analysis of mutated bacteria takes a handful of days, BARDOT takes hours to “read” a bacterial scatter pattern.

The researchers tested BARDOT by allowing it to analyse a regular, wild listeria pattern, then deleting a gene in the system. BARDOT was able to recognize the system with the deleted gene as a listeria pattern. When the original gene was replaced, BARDOT still recognized it as the initial type of bacteria, despite the major genetic change, or mutation.

Where TDLAS has already been tested and proven effective on biological surfaces, Bhunia plans to build a larger library of known bacterial patterns before testing BARDOT as a way to detect food contamination. The details of the findings can be found here, through the American Society of Microbiology.

Creating a Disposable, Printable Laser

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Disposable, single-use items are used by the general public on an almost daily basis. Whether it’s cups, razors, or cleaning products, the ability to consistently have essentials on hand is a convenience for many around the world. When thinking of disposable items and products, lasers are far from the first thing that pops into one’s mind. Teams in France and Hungary are looking to change that perception by creating a small, printed (and possibly disposable!) laser system.

Using inkjet printing, the researchers have designed and developed laser systems that are so low-cost and efficient, they might as well be thrown away after use.  The lasers are organic in nature, using carbon-based materials to amplify light. Organic lasers have the advantage in this application due to their low cost, ease of creation, range of wavelengths, and “high yield photonic conversion.”

One of the major criticisms of organic lasers is the faster degradation rate compared to inorganic lasers. By making the lasers less costly, the downfall becomes the perk, opening the door for disposable laser systems in the fairly near future.

This is not to say that laser systems are going to be coming out of your office printer anytime soon. The process of inkjet printing, however, is very similar across its many applications. Essentially, inkjet printing works by simply applying small amounts of a fluid ink to another surface. As dyes are already used in a number of laser applications, the team combined the dyes with an ink known as EMD6415, chosen due to its “printing and optical properties.”

The ink was then printed onto a slide made of quartz, in 50 mm² pixels to create a laser chip. The ink serves as the laser’s gain medium, as the chip is placed between two mirrors that reflect light back and forth through the gain medium and an energy source. An additional laser, referred to as the pump, provides the necessary energy for the laser chip to work.

The researchers estimate that the laser chips could be manufactured for a mere few cents, and could potentially be swapped out once the laser starts to deteriorate. The biggest obstacle to the widespread implementation of disposable, organic lasers is the need to be powered by a separate, high-energy laser. Once an alternative method is found, researchers speculate that the disposable, printed lasers could be used for sample analysis for chemical or biological materials.

Infrared Lasers: A Treatment for Alzheimer’s Disease

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According to recent studies, nearly 5 to 10 percent of Americans over age 60 are struggling with dementia. The term dementia is a common term which collectively classifies many degenerative brain diseases such as Alzheimer’s disease (AD). This disease is a neurological disorder which leads to memory loss that is caused by the death of brain cells thus labeling this disorder as a neurodegenerative type of dementia. AD starts mild and gets progressively worse through the passing of time.

This disease was diagnosed in 1906 after Dr. Alois Alzheimer observed many drastic changes in a patient’s brain tissue who had eventually died of an unusual mental illness. Observed symptoms included: memory loss, language problems, and unpredictable behavior.

One treatment that may be used to treat AD in the future includes an inspiring application of laser technology. The patient would have to undergo a process termed “photobiomodulation,” or low-level light therapy. Through this process, a low-level infrared laser is used in order to amplify light energy into radiant energy. This energy is then absorbed into tissues to enhance the body system’s wound healing process.

Through lab-mice experiments, a research group at the University of Sydney, lead by Dr. Siva Purushthuman, has recently discovered that five treatments each week of photobiomodulation drastically reduces the compulsive characteristics of Alzheimer’s disease or AD biomarkers. These results support the idea that infrared lasers show great potential as a minimally-invasive mediation for mitigating continuous AD symptoms.

In order for this process to work, Dr. Purushthuman observed that the light would have to penetrate through the thick human skull and into the brain. Even though these experiments were performed on mice with smaller and thinner skulls, this process does show the potential to be effective if the aforementioned obstacle were resolved. This gives room for future studies, experiments, and research in infrared light therapy.

The findings of Dr. Purushthuman and his research group have been published in Alzheimer’s Research and Therapy.

Deborah Jin and the Fermionic Condensate

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Deborah Jin is a respected American physicist who studies within polar molecular quantum chemistry in order to use lasers to make atoms cold. She has been involved in some of the earliest studies of the Bose-Einstein condensates which was led by Dr. Lene Hau. Dr. Jin is currently a NIST fellow at JILA while also being a professor adjoint in the Department of Physics at the University of Colorado in Boulder.

In 1990, Dr. Jin graduated from Princeton University and later received her Ph.D. in physics in 1995 from the University of Chicago. While performing focused research and studies within the field of polar molecular quantum chemistry, Dr. Jin’s team was the first to create the fermionic condensate, a new form of matter. This process included using magnetic traps and lasers as means to cool fermionic atomic gases to less than a millionth of a degree above zero. This process successfully demonstrated “quantum degeneracy.”

Within physics, particles are classified as being either fermions or bosons. Photons are bosons while electrons, protons, and neutrons are all fermions with fermions being the buildings blocks of matter.
Dr. Jin and her team used lasers and magnetic traps as a means to cool a vapor of fermions to a temperature less than a millionth of a degree above absolute zero on December 16 2003 and thus fermionic condensates were created. The study of Fermionic condensates is closely related to the study of Bose-Einstein condensates. However, unlike Bose-Einstein condensates, Fermionic condensates are formed using fermions instead of bosons and are a type of superfluid that is attained at temperatures lower than that of Bose-Einstein condensates.

The “superfluid phase” is formed by fermionic particles at low temperatures and are more difficult to produce than a bosonic one. Superfluids possess certain properties which are highly similar to those possessed by ordinary liquids and gases. These properties consist of the lack of a definite shape while simultaneously attaining the ability to flow and move about in response to various applied forces. In short, superfluids possess properties that aren’t typically found in ordinary matter thus being one of the major distinguishing factors between fermionic condensates and bosonic condensates.

For her amazing discoveries, Dr. Jin has also received several awards. These awards include the 2000 Presidential Early Career Awards for Scientists and Engineers (PECASE) and, more recently, the Benjamin Franklin Medal of Physics in 2008.

The findings of Dr. Jin and her research team were published in the online edition of Physical Review Letters on January 24, 2004.