29 August 2016

Big dreams and nanomedicine: optical nanotransformers

Guest blogger: Elizabeth Bernhardt, a physics research assistant in nonlinear optics at Washington State University, is  blogging on presentations at SPIE Optics + Photonics in San Diego, California, 28 August through 1 September.

Dream big dreams, create amazing solutions:
Paras Prasad offered inspiration in a talk on
how nanomedicine can save lives
Treating diseases in the human body can be incredibly difficult and certain cancers may even be inoperable.

In the opening all-symposium plenary at SPIE Optics + Photonics 2016, Paras Prasad, Executive Director of the Institute for Lasers, Photonics, and Biophotonics at the University at Buffalo, New York, told how he aims to bring treatment directly to the source of the disease, using light.

Inspired early on by James Cameron's move Fantastic Voyage (1966), Dr. Prasad imagined sending something tiny into the human blood stream to specifically target disease. He turned science fiction into reality via nanomedicine.

Nanomedicine uses incredibly small devices, such as multilayered nanotransducers, to treat human diseases from inside the body. The first layer absorbs a particular wavelength of light. The next layer takes this absorbed energy and converts it to a higher or lower wavelength, which is then re-radiated.

The overarching idea is to take low-energy light, such as infrared, send it to a particular location in the body, then change the light to a different, more useful energy. IR light easily passes through the human body with very little damage. Nanotransducers absorb this light, turning it into useful, high-energy visible light, which is easily and readily absorbed by nearby cells. The cells are then destroyed, for an effective and potentially less dangerous way of treating cancer.

Dr. Prasad described another dream becoming reality, via the work of Nobel Laureate Maria Goeppert-Mayer, who developed the theory of two-photon absorption.

At the time, it was assumed experimental verification would never be possible. However, with development of the laser, two-photon absorption occurs every time one uses a green laser pointer.

Moreover, two-photon absorption can be used for dental bonding, killing bacteria, two-photon microscopy, and more. Indeed, Dr. Prasad showed materials applicable to night vision, security, and friend-foe identification. These materials appear to be different colors based on the light they absorb.

He challenged the audience to turn their own imaginings into reality as well. Perhaps the next project in optogenetics (using light to effect genes) will cure or help people with neurological disorders, or even enhance capabilities ... maybe one day neurophotonics will help Superman jump from the pages of a comic book into real-life super-human capabilities.

Note: On Wednesday 31 August, Dr. Prasad will receive the SPIE Gold Medal, the highest award of the Society, in recognition of his work.

25 August 2016

Eight to anticipate: photonics technologies coming our way

Optics and photonics technologies are at work improving our lives in many ways.

These technologies are what provide sustainable lighting and energy-generation systems. Nanoparticles are used to rapidly diagnose disease or derive 3D images of living, functioning cells. Optical resonators detect counterfeit or pirated goods. Airborne telescopes probe deep into the Universe while optical fibers send messages instantly across the globe.

Engineers and scientists from around the world meet every August at SPIE Optics + Photonics in San Diego to advance research in several broad areas of optics and photonics. A few of the 3,000+ researchers who will present reports next week have provided previews via articles they have authored recently for the SPIE Newsroom.

Multicolor rapid diagnostics for infectious disease,” Kimberly Hamad-Schifferli, Chunwan Yen, Helena de Puig, José Goméz-Marquéz, Irene Bosch and Lee Gehrke [ref. 9923-28, Tuesday 30 August, 9 a.m.]
Recent epidemic outbreaks have highlighted the need for a rapid point-of-care assay that can provide a diagnosis to enable treatment, proper quarantining, and disease surveillance. One promising diagnostic is the lateral flow test, i.e., the same type of assay used in pregnancy tests: a paper strip to which a biological fluid is added. These are attractive for diagnostics because they are inexpensive, easy to use, and do not require special reagents or experts to run them.

Custom complex 3D microtubule networks for experimentation and engineering,” Michael Vershinin, Jared Bergman and Florence Doval [ref. 9930-4, Sunday 28 August, 10 a.m.]
Cargo logistics — driven by cytoskeletal motors and proceeding along actin and microtubule filaments — are an essential subsystem of the overall machinery of eukaryotic cells. It is no stretch to say that virtually every process in a living cell depends, directly or indirectly, on proper routing of cargoes in a timely fashion. Much progress has been made in the last few decades in understanding the structure and properties of individual filaments and motors, but clean experimental modeling of how these components add up to a functional cytoskeleton still poses many challenges.

Anisotropic Fabry-Perot resonators for anticounterfeiting applications,” In-Ho Lee, Eui-Sang Yu, Se-Um Kim and Sin-Doo Lee [ref. 9940-2, Sunday 28 August, 8:55 a.m.].
The prevalence of counterfeited and pirated goods in modern society has increased the demand for anticounterfeiting technologies. Global trade of such items in 2015 was estimated to be worth $960 billion, and a danger to 2.5 million jobs. Much effort has been made in the development of smart security labels designed to hide information in normal conditions and reveal it in others.

Organic LEDs with low power consumption and long lifetimes,” Satoshi Seo [ref. 9941-18, Sunday 28 August, 4:40 p.m.]
An LED with an emissive organic thin film sandwiched between the anode and cathode is known as an organic-LED (OLED). The emission mechanism of an OLED is superficially similar to that of a standard LED, i.e., holes and electrons are injected from the anode and cathode, respectively, and these carriers recombine to form excited states (excitons) that lead to light emission. In recent years, smartphones and TVs with OLED displays have rapidly become widespread because OLEDs provide high contrast, a wide color gamut, light weight, thinness, and flexibility for the displays. OLEDs also have great potential for the creation of new lighting applications. The high power consumption and short lifetime of OLEDs, however, remain key issues.

Using femtosecond lasers to grow nonlinear optical crystals in glass,” Carl Liebig, Jonathan Goldstein, Sean McDaniel, Eric Glaze, Doug Krein and Gary Cook [ref. 9958-5, Sunday 28 August, 10:30 a.m.]
Non-centrosymmetric crystals whose optical response does not vary linearly with the strength of an electric field — known as nonlinear optical (NLO) crystals — are the fundamental building blocks for most electro-optic applications. The production of novel NLO crystals is very difficult because it entails bulk techniques that require long growth times and expensive equipment, and that often result in low-quality crystals. For more than three decades, lasers have been used to make modifications to glass refractive indices in the fabrication of high-efficiency waveguides. In recent work, the use of femtosecond laser sources facilitates the fabrication of multidimensional structures composed of many types of NLO crystals.

Synchrotron ‘pink beam’ tomography for the study of dynamic processes,” Mark Rivers [ref. 9967-33, Tuesday 30 August, 3:00 p.m.]
Computerized axial tomography scanning has revolutionized medical imaging, and through microtomography, its spatial resolution can be reduced from the millimeter scale to the micrometer scale. Microtomography has developed rapidly, driven by developments in x-ray sources, computers, and particularly in detectors. There are now microtomography systems available for laboratory use and microtomography has been applied to fields including biology, geology, soil science, and the study of meteorites. Monochromatic beams are generally unsuitable for dynamic studies. So-called pink beam microtomography is an alternative.

Making unique IR observations with an airborne 2.5m telescope,” Eric Becklin, Maureen Savage, Erick Young and Dana Backman [ref. 9973-17, Tuesday 30 August, 8:30 a.m.]
Large parts of the IR spectrum are inaccessible in observations made from ground-based telescopes because of absorption by water vapor in the atmosphere.For this reason, the Stratospheric Observatory for IR Astronomy (SOFIA) — a joint project between NASA and the German Aerospace Center (DLR) — was designed and has been operational since 2010. SOFIA has become a key facility for several astronomy investigations, e.g., for studying regions of star formation, observing objects obscured by interstellar dust, and making time-critical measurements of transient events.

Robust photon-pair source survives rocket explosion,” Zhongkan Tang, Rakhitha Chandrasekara, Yue Chuan Tan, Cliff Cheng, Kadir Durak and Alexander Ling [ref. 9980-8, Monday 29 August, 8:05 a.m.]
Quantum key distribution (QKD) is of much interest for quantum communications because of its high level of privacy (underpinned by quantum mechanics). In particular, entanglement-based QKD is a powerful technique in which quantum correlations between photons are leveraged. In this process, the entangled photons can be distributed with the use of optical fibers or ground-level free-space links. Current QKD networks, however, suffer from a distance limit because of fiber losses and the lack of quantum repeaters.

16 August 2016

Keeping nighttime lighting under control

Yosemite National Park offers stunning views of mountain vistas during the day and star-filled skies at night. This view often includes the Milky Way -- invisible to almost one third of Earth’s population due to light pollution.

Artificial lighting is restricted in Yosemite, but some areas in the park require lighting, such as parking lots and pathways between buildings. Light pollution can not only have a negative effect on visitors’ experiences, but can also change the natural rhythms of the park’s wildlife.

University of California, Merced (UC Merced) graduate student Melissa Ricketts has found a solution – by turning one of her professor’s inventions upside down. In an article from UC Merced’s University News, Ricketts describes what she calls “prescribed irradiance distribution.”

Ricketts is a member of UC Solar, a multicampus research institute headquartered at UC Merced headed by Roland Winston, the inventor of nonimaging optics. His compound parabolic concentrator (CPC) is a key piece of solar-collecting equipment in the emerging solar energy industry. Ricketts has developed a way to make Winston’s CPC emit light rather than gather it.

“It’s the reverse of the solar collector,” Ricketts said. “We can make a perfect square of LED light, or a circle, or whatever shape works best to illuminate only what needs to be illuminated.

Ricketts has been working with Steve Shackelton, a UC Merced staff member and former Yosemite chief ranger, on what they call “The Sand Pile Project.” Although most of their work is done in the lab, designs are occasionally tested in Yosemite on a large pile of sand that snowplow operators spread on the park roads when needed. The park needs to keep the sand pile well-lit so it can be accessed at any time, but lighting should have minimum effects on the surrounding areas.

UC Merced graduate student Melissa Ricketts sets up her LED
 lighting solution in the Sand Pile at Yosemite National Park
Credit: Courtesy of UC Merced

Yosemite is cautious about introducing new technology into the park, but they have been supportive of Ricketts’ research toward managing light by letting her use the area as a test where her work could eventually have global implications for wildlife and park visitors.

“We’re hoping to show the park we can eliminate the unnecessary light,” Ricketts said. She’s currently seeking funding to make the project viable for Yosemite and other parks

08 August 2016

Laser-induced removal of space debris

If you never thought something as small as a paint chip could have the potential to destroy the International Space Station, think again. Traveling at speeds upwards of 17,500 mph, the ISS could be torn apart by debris smaller than a marble in an instant. NASA is currently tracking more than 500,000 objects orbiting Earth including non-operational satellites and obsolete disengagements from past rocket missions. But the greatest risk to active satellites and space missions comes from the millions of pieces of debris that are nearly impossible to track.
7 mm chip on ISS window caused by a small
fragment of space debris no larger than
a few microns across

An article from 12 May 2016 in the Washington Post reported the International Space Station’s recent collision with “something as unassuming as a flake of paint or a metal fragment just a few thousandths of a millimeter across.”

The fragment left a 7-millimeter chip in a window of the European-built Cupola module. ESA astronaut Tim Peake was the first to snap a picture of the damage, then shared it with the world on his twitter account.

So how might we deal with all this hazardous space material? Lasers!

Authors of Laser-based removal of irregularly shaped space debris, Stefan Scharring, Jascha Wilken, and Hans-Albert Eckel of the German Aerospace Center discuss a new method in applying laser-induced damage principles to clean up space junk, where the use of high-energy laser pulses modify the orbit of debris causing it to burn up in the atmosphere.

The greatest improvement from previous studies in laser-based removal of debris is the ability to target irregularly-shaped objects – a characteristic shared by most space material.

To get a better picture of how much debris we’re working with, watch this short video simulating the increasing amount of space junk that has accumulated over the years in low Earth orbit (LEO).

Claude Phipps of Photonic Associates, LLC and his colleagues have been researching laser orbital debris removal (LODR) for over 15 years and have concluded that it is a very promising technique. Laser technology is improving at an astounding rate and is proving to be the most cost-efficient solution to space junk clean up.