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06 April 2016

Cataract surgery: misnomer?

On left, the patient’s left eye has no cataract and all structures are visible. On right, retinal image from fundus camera confirms the presence of a cataract. (From Choi, Hjelmstad, Taibl, and Sayegh, SPIE Proc. 85671Y, 2013)

On left, the patient’s left eye has no cataract and all structures are visible. On right, retinal image from fundus camera confirms the presence of a cataract. (From Choi, Hjelmstad, Taibl, and Sayegh, SPIE Proc. 85671Y, 2013)
 
Article by guest blogger Roger S. Reiss, SPIE Fellow and recipient of the 2000 SPIE President's Award. Reiss was the original Ad Hoc Chair of SPIE Optomechanical Working Group. He manages the LinkedIn Group “Photonic Engineering and Photonic Instruments.”

The human eye and its interface with the human brain fit the definition of an "instrument system."  The human eye by itself is also an instrument by definition.

After the invention of the microscope and the telescope, the human eye was the first and only detector for hundreds of years, only to be supplemented and in most cases supplanted by an electro-optical detector of various configurations.

The evolution of the eye has been and still is a mystery.  In National Geographic (February 2016) an excellent article titled "Seeing the Light" has a very good explanation of the eye's development

Having recently had cataract surgery, my interest in the eye was stimulated. First, I wondered why "cataract surgery" is called "cataract surgery."

In cataract surgery, no surgery is performed on the cataracts (cataract material). A very small incision is made in the lens pocket and the cataract material is flushed out by using the opening to introduce the flushing substance, and the flushing substance carries out the cataract material through that opening. The cataract material may require ultrasonic fracturing to reduce particle size.  A man- and machine-made lens is inserted into the opening.  The opening may or may not require suturing. This procedure should more accurately be known as "lens replacement surgery."

Why are a large number of measurements made on the eye before the eye surgery?

Without invasion of the eyeball, a great many measurements from outside it must be made to determine the required focal length of the replacement lens. (Some people do need corrective glasses to achieve the correct value.) When I asked about all these measurements (made by high-precision lasers) other important factors were brought up, including knowledge of the instruments by the operator, guesswork, and finally…some luck.  Luckily, without glasses distance vision is infinite after surgery, but reading glasses are a necessity. Today, there are many options available to cataract patients, including multifocal lenses, which may enable complete independence from glasses.

After having lens replacement surgery myself, two haunting questions remain unanswered in my mind.

A. Where did the optical-quality fluid (vitreous) in the original eye lens and the eyeball come from, and how did it know where it belonged? Optical-quality liquid or gel occurs in the human eye but nowhere else in the human body.

B. How did the Creator (or whoever or whatever, a religious question) -- without Physics 101 or Optics 101 or Warren Smith's book on basic optics -- determine the focal length of the eye lens (the distance from the eye lens to the retina; some people do need corrective glasses to achieve the correct value). The focal length of the human eye lens is a mathematical value based on measurements and calculations or both and could not have just evolved without some knowledge and information about basic optics.

I wish I could answer either of these two questions but I will have to wait for someone smarter than me. Until then let’s at least change the name of the operational procedure to reflect what is actually being performed, so that people will understand that their cataracts are not being operated on but that their eye lens is being replaced.

Meanwhile, beyond these everyday procedures for improving vision, exciting advances are emerging from labs around the world, enabled by photonics. These include smart contact lenses for monitoring and even treating disease. Artificial retinas under development at Stanford, USC, and elsewhere offer the promise of vision to the blind. The results might not be as clear as what we are used to (yet), but imaging technologies and/or nanomaterials that send visual signals to the brain are helping counter the effects of age-related macular degeneration and other vision problems. New devices and treatments may offer a bright future to those with previously intractable vision problems.


09 March 2016

Graphene: changing the world with 2D photonics

In existing technologies, 2D technologies can be introduced
into products such as silicon electronics, semiconductor
nanoparticles, plastics and more for added new
functionality; above; a flexible 2d prototype sensor.
Graphene, anticipated as the next "killer" app to hit optical sensing, is expected to offer an all-in-one solution to the challenges of future optoelectronic technologies, says Frank Koppens. A professor at the Institute of Photonic Sciences (ICFO) in Barcelona, Koppens leads the institute's Quantum Nano-Optoelectronics Group.

Koppens, along with Nathalie Vermeulen of B-PHOT (Brussels Photonics Team, Vrije Universiteit Brussel), will lead a daylong workshop in Brussels on 5 April on transitioning graphene-based photonics technology from research to commercialization.

In his article on Light and Graphene in the current issue of SPIE Professional magazine, Koppens describes the 2D material's tunable optical properties, broadband absorption (from UV to THz), high electrical mobility for ultrafast operation, and novel gate-tunable plasmonic properties.

Two-dimensional materials-based photodetectors are among the most mature and promising solutions, Koppens notes. Potential applications include expanded communications networking and data storage, increased computing speeds, enhanced disease control utilizing increasingly larger and more complex data sets, and more accurate fire, motion, chemical, and other sensor systems including the next generation of wearables.

Graphene is gapless, absorbing light in the ultraviolet, visible, short-wave infrared, near-infrared, mid-infrared, far-infrared, and terahertz spectral regimes. A few of many advantages include:
  • Ability to be monolithically integrated with silicon electronics
  • Extremely fast -- exceeding 250GHz -- as a material-based photodetector
  • Able to bend, stretch, and roll while maintaining useful properties
  • Low-cost production with potential to integrate on thin, transparent, flexible substrates
  • Potential to be competitive against alternate applications in health, safety, security and automotive systems.

Koppens notes that the €1 billion European Union Graphene Flagship program is aiming to work through academia and industry to bring graphene into society within the next 10 years.

For more, read the complete article in the SPIE Professional, and watch Koppens' SPIE Newsroom video interview [7:09] on manipulating light with graphene.

08 February 2016

UPDATE! Gravitational waves ... detected!

Prior to sealing up the chamber and pumping the
vacuum system down, a LIGO optics technician
inspects one of LIGO’s core optics (mirrors) by
illuminating its surface with light at a glancing angle.
It is critical to LIGO's operation that there is no
contamination on any of its optical surfaces.
Credit: Matt Heintze/Caltech/MIT/LIGO Lab
Update, 11 February: A hundred years after Einstein predicted them, gravitational waves from a cataclysmic event a billion years ago have been observed.

For the first time, scientists have observed gravitational waves, ripples in the fabric of spacetime arriving at Earth from a cataclysmic event in the distant universe. This confirms a major prediction of Albert Einstein's 1915 general theory of relativity and opens an unprecedented new window to the cosmos.

The discovery was announced on 11 February at a press conference in Washington, DC, hosted by the National Science Foundation, the primary funder of the Laser Interferometer Gravitational Wave Observatory (LIGO).

The gravitational waves were produced during the final fraction of a second of the merger of two black holes to produce a single, more massive spinning black hole. This collision of two black holes had been predicted but never observed.

The event took place on 14 September 2015 at 5:51 a.m. EDT (09:51 UTC) by both of the twin (LIGO) detectors, located in Livingston, Louisiana, and Hanford, Washington. The LIGO observatories are funded by the National Science Foundation (NSF), and were conceived, built and are operated by the California Institute of Technology (Caltech) and the Massachusetts Institute of Technology (MIT).


Earlier this week (on 8 February), we wrote:

Gravitational wave rumors pulsate through media


The control room of the LIGO Hanford detector site
near Hanford, Washington. Credit: Caltech/MIT/LIGO Lab
The cosmic rumor mill has been busy lately with tweets and lots of buzz about a potential announcement of observation of gravitational waves by the Laser Interferometer Gravitational Wave Observatory (LIGO). Predicted by Einstein 100 years ago, gravitational waves are ripples in space-time caused by collisions of massive objects like black holes and neutron star.

The LIGO interferometers in Louisiana and Washington State were just retooled, based on what researchers learned from their first few years of observations from 2002 to 2010. They are already several times more sensitive, and as the instruments are tuned to design sensitivity, they will be even better. According to some reports, their first observing run may have already found something. We’ll know on 11 February and we will update this post after that. Until then, see these reports:



The SPIE Newsroom visited LIGO Hanford Observatory last fall, just after the first observing run began for Advanced LIGO. In the following video, observatory Head Frederick Raab and LIGO Hanford Lead Scientist Mike Landry introduce us to the instrumentation and setup of LIGO Hanford, from the laser whose beam travels through the 4-km tubes of LIGO, to the stabilization needed for the interferometer’s mirrors:

25 January 2016

The photonics of Star Trek: 6 ways sci-fi imagined the future that is today


Sci-fi meets reality in this 1975 NASA photo: The Shuttle Enterprise rolls out of its Palmdale, California, manufacturing facilities with Star Trek television cast members on hand for the ceremony. From left to right are James Fletcher (NASA), DeForest Kelley (“Dr. ‘Bones’ McCoy”), George Takei (“Mr. Sulu”), James Doohan (“Chief Engineer Montgomery ‘Scotty’ Scott”), Nichelle Nichols (“Lt. Uhura”), Leonard Nimoy (“Mr. Spock”), Star Trek creator Gene Roddenberry, an unnamed NASA official, and Walter Koenig (“Ensign Pavel Chekov”).



Fifty years after Gene Roddenberry launched the Star Trek series on American television, many of the then-futuristic devices and ideas on the award-winning show have become commonplace on Earth.

Roddenberry’s creativity and extensive homework in consultation with scientists and engineers of his day infused the show with technology such as photodynamic therapy, laser weapons, and handheld sensors and communication devices. In the process, his sci-fi world colored our expectations, inspiring more than a few young people with a level of interest that led to STEM careers.

The short list that follows notes photonics-enabled ideas and props from the initial series (1966–69) that have become reality. See the January 2016 SPIE Professional magazine article for more.

1. The Replicator: today’s 3D printer

Star Trek’s replicator synthesized food, water, and other provisions on demand.

Today, the company 3D Systems sells consumers a popular 3D printer based on stereolithography, a solid-imaging technology for which company founder Chuck Hull received a patent in 1986. General Electric uses laser-powered 3D printers to create jet-engine fuel nozzles and other complex components

In space, a 3D printer from the company Made in Space was delivered to the International Space Station to test the effects of microgravity on 3D printing.

2. The Communicator: the first flip phone

Captain Kirk and other Enterprise crew members flipped open their personal communicators to speak to someone elsewhere on the starship or on a planet below.

Motorola engineer Martin Cooper, who invented the first mobile phone, told Time magazine that his invention was inspired by the Star Trek communicator.

The flip phone already has been succeeded by smartphones and tablets; photonics devices with displays, lenses, cameras, and more. Lasers are used to manufacture the processors, cases, and batteries and to mark a serial number on each device.

3. The Long-Range Scanner: today’s space-based sensors

Scanners on the Enterprise could detect atmospheric chemistry and presence of water on faraway planets, and even count life forms.

All of this is possible today via satellites or aircraft equipped with photonics sensors.

This year, the European Space Agency will launch a spacecraft equipped with sensors that optical engineers developed to search Mars for evidence of methane and other trace atmospheric gases that could be signatures of active biological or geological processes, using two infrared and one ultraviolet spectrometer.

4. The Tricorder: tomorrow’s Tricorder!

The Star Trek tricorder (a TRI-function reCORDER) was a black rectangular device with a shoulder strap with three functions: to scan a person or unfamiliar area, record technical data, and analyze that data.

For today’s Tricorder, contestants for the $10 million Qualcomm Tricorder XPRIZE are competing in developing a consumer-friendly device capable of diagnosing 15 medical conditions and capturing metrics for health. Consumer testing of finalist teams’ solutions is scheduled for this September, with the winner to be announced in early 2017.

5. Invisibility Cloak: object cloaking

Metamaterials have been demonstrated to effectively cloak objects by manipulating the paths of lightwaves through a novel optical material, demonstrating the basic physics used to make Romulan and Klingon spacecraft invisible in Star Trek.

Sir John Pendry of Imperial College is one of the real-life pioneers of invisibility cloaking with negative-refractive-index metamaterials, and many others report on their research at various SPIE conferences on metamaterials and plasmonics.

6. Healing with light: photodynamic therapy

Star Trek’s chief medical officer, “Bones,” used light for surgery, wound care, accelerated bone healing, and as a dermal regenerator to rebuild skin -- all of which will be discussed at SPIE BiOS during SPIE Photonics West in San Francisco next month.

Lasers and specific wavelengths of light are used today to treat cancer and help skin heal faster, and for for aesthetic treatments, dentistry, and eye surgery. Transcranial near-infrared laser therapy (NILT) has been used to reduce the severity of stroke. Complex skin cancers have been treated at University of Lund and elsewhere using light-activated (photodynamic) medicine.

What fueled your dreams?

Theoretical physicist Stephen Hawking once wrote that "Science fiction such as Star Trek is not only good fun but it also serves a serious purpose, that of expanding the human imagination.” With a nod to such inspiration, the SPIE Photonics West 2016 welcome reception will celebrate the Star Trek anniversary.

What other light-based technologies depicted by Star Trek or elsewhere in science fiction serve a real purpose today or inspired your STEM career?

15 December 2015

Pigeon vision: ‘flocksourcing’ cancer detection

Researchers are learning more about how to improve cancer
detection through teaching pigeons like the two above
to identify images of cancerous cells.
Pigeons have been taught how to detect breast cancer -- with an accuracy rate that surpasses humans -- and in the process have inspired ideas about how to better teach humans how to visually detect cancer.

Researchers from the University of California Davis, the University of Iowa, and Emory University published a paper last month detailing how they trained pigeons -- Columba livia, commonly called rock doves, to be precise -- to detect cancerous cells. The birds attained an accuracy rate of 85%, higher than the accuracy of humans doing the task (84%), the Chicago Tribune reported. (Also see the Wall Street Journal for more coverage.)

And when four pigeons were tested on the image and their results combined (“flocksourcing”?), the birds were 99% accurate in identifying cancerous cells.

The researchers also found that while the pigeons had high-accuracy results when looking at slides from tissue samples, they were not able to learn how to accurately identify signs of cancer when looking at mammograms. Unlike biopsied cells viewed under magnification, mammogram images show neighboring tissues such as blood vessels, a factor which affects human accuracy as well.

Because a pigeon’s vision works much the same as a human’s, the research could help scientists improve the results in teaching humans how to visually identify cancer.

“Pathologists and radiologists spend years acquiring and refining their medically essential visual skills, so it is of considerable interest to understand how this process actually unfolds and what image features and properties are critical for accurate diagnostic performance,” the researchers wrote in their article in PLoS ONE.

The research team included Edward Wasserman, Stuit Professor of Experimental Psychology at the University of Iowa; Elizabeth Krupinksi, professor and Vice Chair for Research in the Department of Radiology and Imaging Sciences at Emory University; Richard Levenson, professor and Vice Chair for Strategic Technologies in the Department of Pathology and Laboratory Medicine at the University of California Davis Medical Center; and Victor Navarro, a graduate student in the Department of Psychological and Brain Sciences at the University of Iowa.

30 November 2015

Improve and carry on, use the fear: advice from women in STEM

SPIE Women in Optics 18-month
planner for 2016-2017.
Interest in science, technology, engineering, or mathematics (STEM) can lead to a wide variety of careers. A few examples:
  • exploring photonic nanostructures that can improve the efficiency of solar energy generation
  • observing micro-organisms in the Arctic ice to learn more about lifeforms of all sorts
  • developing optical systems for noninvasive diagnosis of tumors inside the body
  • assessing the radiation hazard to be incurred by humans travelling to the Moon, Mars, and beyond.
The paths to all careers include some challenges. For anyone looking at a career in STEM, the latest edition of a free annual publication offering insights on those paths has just been released.

The 12th edition of the Women in Optics Planner published by SPIE contains more insights from more than 30 women discussing their interests and occupations and offering advice. Among their stories:

Viera-Gonzalez
Perla Marlene Viera-Gonzalez, a PhD student at the Universidad Autónoma de Nuevo León, specializes in optical design applied to solar illumination systems.

Her biggest career obstacle is “swimming upstream and (meeting) resistance to change. I sometimes encounter people who prefer to always do things the same way. The solution? I never give up. Believe in yourself. Try new ideas, and if you fail, learn from that. Improve and carry on.”

Viera-Gonzalez shares her inspiration and passion with her community, organizing STEM conferences for students, workshops for kids, basic education for teachers, science fairs, and other events, with support from SPIE and her university.

Mikkelsen
Maiken Mikkelsen, now an assistant professor of electrical and computer engineering and of physics at Duke University, grew up in Denmark and  found physics to be her favorite subject in school.

Now she leads a research group exploring the behavior of novel nanoscale structures and materials by studying their interaction with laser light, which may lay the foundation for future quantum- or nano-based technologies. Her advice? “Follow your heart and do what you love!”

Lukishova
Svetlana Lukishova earned degrees through her PhD at Moscow Institute of Physics and Technology and is now a senior scientist at the University of Rochester leading a group in quantum nanophotonics.

As an undergrad, she followed the advice of a professor to select the strongest research group with an outstanding leader and ended up carrying out her master’s and PhD research under  Nobel Laureate Alexander Prokhorov.

As a working professional, she says, her biggest obstacle is that she is “too modest. In a competitive environment, it is necessary to defend your rights.” She advises young girls “to set the highest goals in your life and your scientific and engineering career; work hard, but with inspiration; and don’t forget that you are women.”

James Asirvatham
"Dream first, try next, and do your best," Juanita Saroj James Asirvatham, research associate at Lancaster University, advises young women who wish to pursue a career in optics and photonics.  

As a research associate at Lancaster University, Asirvatham explores novel photonic nanostructures to improve the efficiency and economy of solar energy production. "STEM is for creative thinkers," she says. "Choosing a career in STEM will provide lifelong professional development.”

Greenwood
Born in Germany and educated in Scotland, Bernadette Greenwood, the director of clinical services at Desert Medical Imaging, advises young women in STEM fields to overcome barriers to success by applying logic, sensibility, and patience to any situation.

"Sometimes it's impossible not to feel discouraged, but stay strong and believe in yourself. Use fear as fuel for action," she says.

Greenwood oversees an MRI-based prostate cancer clinical trial, delivering laser interstitial thermal therapy to prostate cancer using thermal mapping with MRI.

Wang
For Hui (Catherine) Wang, deputy director of the Department of International Cooperation at the Changchun Institute of Optics, Fine Mechanics, and Physics, the biggest challenge is not having a scientific background. She holds a master’s degree in English literature. Wang works at continually increasing her knowledge through reading books and journals, having discussions with colleagues, and attending academic conferences.

Do not to be afraid of difficulties and mistakes, Wang advises. "Facing these can make you stronger."

All the stories are available online; copies of the planner are free for the asking via the same link.

Thanks to all for the inspiration!

17 November 2015

Six dramatic advances in solar energy

Harvesting, collecting, and deriving usable energy from the Sun and other sustainable sources for people around our planet has made important leaps forward of late. Whether it is summer or winter in your part of the world, that’s excellent news for our future energy needs.

The dual nature of light, recently demonstrated
in an image from the Carbone group at École
Polytechnique Fédérale de Lausanne, and featured
as Figure 1 in a review paper in the Journal of Photonics
for Energy
: "Energy-space photography of light
confined on a nanowire simultaneously shows both
spatial interference and energy quantization."
doi:10.1117/1.JPE.5.050997
An open-access article in the Journal of Photonics for Energy co-authored by nine international experts* details some of those advances. Here’s a short list from their review of the state of the art, titled "The role of photonics in energy."

1. Making cheaper and more efficient solar cells

Today’s solar cells are based on inorganic semiconductors -– particularly silicon, the second most abundant material in the Earth’s crust. However, silicon solar cells, although relatively expensive to manufacture, are not the most efficient at converting solar energy into electrical energy.

Solar cells based on other semiconductors are more efficient at conversion but also cost more to make.

A new generation of solar cells in development promises the advantages of low-cost materials, high-throughput manufacturing methods, and low-energy expenditure. These very new emerging cells are still less efficient than more established inorganic solar cells, but they have been improved dramatically over the last few years. Particularly promising are technologies using organic-inorganic hybrid materials such as perovskites.

2. Limiting lost light

Researchers are also working on methods of trapping light within a solar cell more effectively, to limit the amount of energy lost due to reflection off the silicon crystals or layers of protective glass. Existing antireflective coatings have performance limitations, often minimizing the reflection for only a select region of the solar spectrum, and are also dependent on the angle of incidence.

One possible solution is adding nanostructured surfaces (e.g., micro- or nanopillars or nanowires) to minimize reflection.

3. Directing and driving

An alternative to converting sunlight into electricity is harvesting the thermal energy of sunlight directly. Sunlight can be focused onto long pipes coated with an optically absorbing material and filled with a high-thermal-capacity fluid, which is used to drive a turbine. Coatings such as carbon-nanotube and metallic-nanowire arrays with high absorption capabilities are helping toward the goal of creating nearly perfect absorbers.

4. Storing it for later

Research is also being done on storing solar fuels as an energy source, via water-splitting, a process which occurs naturally during photosynthesis. Splitting separates water into its oxygen and hydrogen elements, and can be induced in a photochemical reaction. The induced process of sunlight-driven water splitting is as yet not efficient. But with that solved, the hydrogen produced could be stored in fuel cells and later used for local electricity generation, for example as a transportation fuel for electric vehicles.

5. Following the Sun

Optical and photonic sensors are widely used to make existing technologies that harvest energy and produce power more effective. Tracking systems adjust the positioning of solar collectors to ensure a continued optimum angle relative to the Sun (perpendicular to solar radiation). Sun trackers have the potential to increase the energy collected by solar energy systems by 10% to 100%, depending on factors including the time of the year and geographical position.

6. … or the wind

Wind farms utilize light detection and ranging (LIDAR) technology, which determines wind speed by measuring the Doppler shift of light backscattered by aerosols in the atmosphere. The accurate measurements of wind speeds and turbulence make it possible to more effectively survey potential wind farm sites, optimize their design, and make dynamic adjustments to their operation.

Want to know more? Read the two-part synopsis of the review article in the SPIE Newsroom:



*The paper is authored by Zakya Kafafi, the journal’s editor-in-chief, and Nelson Tansu of Lehigh University; Raúl Martín-Palma of the Universidad Autónoma de Madrid; Ana Nogueira of the University of Campinas; Deirdre O’Carroll of Rutgers University; Jeremy Pietron of the U.S. Naval Research Laboratory; Ifor Samuel of the University of St Andrews; Franky So of North Carolina State University; and Loucas Tsakalakos of General Electric–Global Research Center.