Category Archives: Optics and Photonics

German Photonic Partnership Tackles Auto Welding Problem

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As the auto business strives toward lightweight components in the quest for greater fuel and energy efficiency, it will increasingly favor composite components that require bimetallic welded joints—particularly between steel and aluminum. But there’s a hitch: such shotgun weddings between different metals commonly produce intermetallic phases across the welding seam that are brittle and prone to failure.

To help tackle that problem, the LaserLeichter project, a German partnership including Laser Zentrum Hannover (LZH) and a variety of research and industrial partners, has announced the development of a process that uses lasers for the “quick and safe joining” of 3-D structures including steel–aluminum joints. According to the partnership, the process can achieve welds that approach the tensile strength of aluminum alloy, with a high throughput compatible with industrial production.

Lightweight construction, photonically driven

LaserLeichter (literally “Laser Lighter”) was unveiled several years ago as one of nine projects funded by the German  Federal Ministry of Education and Research (BMBF) in an initiative, Verband Photonischer Leichtbau, aimed at developing “photonic processes and tools for resource-efficient lightweight construction.” The initiative’s eight other projects focus on leveraging photonic technology, especially lasers, in the production of lightweight plastic components, carbon-fiber-reinforced plastics, and a variety of other component types.1

LaserLeichter has focused specifically on the problems of joining aluminum and steel, where the deployment of lasers in the weld process can escape some of the pitfalls of conventional welding that lead to joint-weakening intermetallic phases. That’s because the comparative precision of the laser targeting and the relatively low heat introduced into workpiece allows the melt and mixing at the joint to be controlled precisely, according to the LaserLeichter partners.

That leads, according to LZH, to a cleaner, stronger joint. A press release detailing the method noted that the joint can achieve a shear tensile strength of around 67 percent of aluminum alloy, or up to 95 percent in situations where three welds are arranged in parallel.

Speed is another advantage of the system, according to the research partnership: the technique can fashion mixed joints at what LZH calls “high welding speeds of up to seven meters per minute.” And one of the LaserLeichter partners, Volkswagen AG, has tested out sample welded components using the process and found that the mixed joints “have an advantageous crash behavior,” remaining connected even after stress.

Trumpf scanner

A key to the technique’s applicability to complex manufacturing environments is a 3-D scanner optic developed for the project by Trumpf. According to the LaserLeichter partnership, the scanner allows the laser to trace out “complex, three-dimensional seam geometries,” even in large-format settings such as car body manufacturing. Indeed, the team argues that the use of the scanner can even “replace complex robot movements” in such factories.

In addition to LZH, Volkswagen and Trumpf, LaserLeichter comprises thirteen other academic, research and industry direct or associated partners, including the automotive-innovation partnership InPro,  Robert Bosch, Brandenburgische Technische Universität, the Fraunhofer Institute and others.

Lidar Mapping of Yellowstone Lake

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Yellowstone National Park, in the United States, has been under attack from a vicious invasive species, the lake trout, for decades. But a lidar technology developed by Montana State University (MSU) researchers offers a tool for fighting back. The research team has designed and tested a device that can rapidly locate the invasive fish for removal, to a depth of at least 15 meters.

Ecosystem onslaught

Thought to have been introduced illegally to Yellowstone Lake in the 1980s, lake trout are decimating the lake’s population of cutthroat trout, its native trout species. Cutthroat trout’s range in the states of Montana, Idaho and Wyoming has dramatically shrunk in recent decades, and Yellowstone Lake is considered a stronghold of the remaining population. Since the introduction of lake trout to Yellowstone Lake, however, the cutthroat trout population has dropped by 99 percent in some areas. Moreover, cutthroat trout are a key food source for many other park predators, including bears, otters and eagles, so this radical population collapse threatens the Yellowstone ecosystem as a whole.

To combat this ecological crisis, the U.S. National Park Service (NPS) spends approximately US$2 million every year to remove hundreds of thousands of lake trout from Yellowstone Lake. This mass culling is a time-consuming and labor-intensive process dependent on small transmitters that are surgically implanted into individual lake trout. The transmitters emit sound frequencies that park staff detect with on-boat receivers, mapping the invasive fish’s whereabouts. During spawning season, park employees locate the fish using the transmitters and use gill nets to remove them. As only around 200 lake trout are implanted with transmitters, the arduous process results in an incomplete map of the fish spawning sites.

A better way

The Montana State team wanted to develop a more effective location process that didn’t require fish surgery, so it turned to lidar. The team first tested the use of lidar technology for fish mapping in 2004, when team leader and OSA Fellow Joseph Shaw, a professor of electrical engineering at MSU, borrowed a marine-fish-detecting lidar device from the U.S. National Oceanic and Atmospheric Administration (NOAA) and conducted test flights over Yellowstone Lake—collecting data that helped NPS to locate previously unknown spawning areas.

Ten years later, in 2014 and 2015, the MSU team designed a new lidar system specifically for affordable airborne studies of freshwater ecosystems. The lidar instrument is attached to a small aircraft and works by transmitting a short pulse of laser light from the plane into the water. The lidar receiver then measures the backscattered light and allows researchers to detect fish in the water. It uses a widely available, relatively affordable 532-nm pulsed Nd:YAG laser to keep the system cost as low as possible. The laser has a 26.8-mJ pulse energy, which provides enough optical power to profile groups of two or more lake trout to a depth of up to 8 m, and a 100-Hz pulse repetition frequency, which provides continuous coverage while flying at 80 km/hour.

In 2015 and 2016, the team tested the device in flights taken over Yellowstone Lake at an altitude of 300 m at both a 5- and 15-mrad field of view (FOV), equivalent to a 1.5- or 4.5-m-diameter spot size on the water. The MSU researchers used data patterns identified in previous studies with the NOAA marine lidar to identify fish in the lidar data from their 2015-2016 experiments. According to the team, the fish locations it identified from the lidar data corresponded with the preferred characteristics of lake trout spawning sites and was consistent with acoustic tracking data from the transmitters—though further investigation is needed to determine whether the locations were indeed spawning sites.

Adopting lidar

Two main improvements of the lidar system over the transmitter approach are that it takes hours rather than days to map the lake, and researchers can detect any fish in shallow water, not just tagged fish. The MSU lidar instrument was developed for less than US$100,000 and can be flown for US$500/hour, making it a relatively inexpensive option compared with acoustic tracking devices.

The researchers believe that the system can be improved by scanning the beam along the transverse axis of the aircraft to increase the survey area, as well as improving the depth penetration of the lidar to extend the range. They conclude that airborne lidar is a promising tool for fishery managers and researchers.

PHYSICISTS DISCOVER NEW FORM OF LIGHT THAT COULD TRANSFORM FUTURE OF FIBER-OPTIC COMMUNICATIONS

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A new discovery made by two Irish Physicists has changed our fundamental understanding of light, with implications effecting quantum computing and fiber-optic communications. The discovery was made by Paul Eastham and John Donegan from Trinity College Dublin’s School of Physics. In the 1830s physicists concluded that photons were limited to integer values of angular momentum. It was believed that angular momentum had to be multiples of Planks constant, ħ.

But a recent breakthrough made by Paul Eastham and John Donegan showed that this is not always the case. Photons in fact can have half-integer values of angular momentum when they are confined to fewer than three dimensions.

To make this discovery the team turned light into a hollow cylinder by passing it through a crystal, and measured its angular momentum when the light passed and bypassed the crystal. They found that when it passed through the crystal the angular momentum was shifted by one-half of planks constant. It has been long theorized that this could be the case but has never been proven before.

‘What I think is so exciting about this result is that even this fundamental property of light, that physicists have always thought was fixed, can be changed,’ said Professor Paul Eastham.

This discovery could have applications on quantum computing and fiber-optic data communications.

Make Clear Eye Contact, Wear Proper Contact Lens

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German ophthalmologist Adolf Fick embarked the journey of optometry with a pioneering method of refractive error correction, the “contact glasses”. The first breakthrough occurred when Bausch+Lomb launched the SofLens in the United States, using patents held by the National Patent Development Corp. and with that, the modern contact lens industry was born.

 Throwing an insight to the lenses:

Contact lenses are the medical contraption taken over directly on the cornea of eye to amend refractive blunders by adding or subtracting converging power to the eye’s lens. Depended on the type of material, lenses are opted for patients by five types:

  1. Soft lensesare made of hydrogels, a gel-like and water-containing plastic molecules. They are very thin lenses and flexible and imitate to the eyes front surface.
  2. Silicone hydrogel lensesare the progressive type of soft contact lenses which allow more oxygen to reach the cornea and are more permeable than regular hydrogel lenses.
  3. Gas permeable lenses(GP or RGP lenses) are inflexible contact lenses that are absorbent and permit oxygen to traverse them. They often afford high-pitched vision than soft and silicone hydrogel contacts, particularly in case of astigmatism.
  4. Hybrid contact lensesare premeditated to afford wearing coziness which adversaries soft or silicone hydrogel lenses, along with the crystal-clear optics of GP lenses. They have a firm gas permeable central zone enclosed by a “skirt” of hydrogel or silicone hydrogel substantial.
  5. PMMA lensesare made from a translucent unbending plastic solid called polymethyl methacrylate (PMMA). They have brilliant optics, but they cannot diffuse oxygen to the eye and thus can lead difficult to acclimate.

 Inspecting according to the Designs for Diseases:

Contact lenses are offered in a variety of strategies, reliant on their envisioned purpose:

  • Spherical contact lenses have the identical lens power throughout the complete visual part of the lens to accurate hyperopia (farsightedness) or myopia (nearsightedness).
  • Toric soft contact lenses have diverse powers in different peaks of the lens to accurate nearsightedness or farsightedness as well as astigmatism.
  • Multifocal contact lenses comprise of various power zones for near and far vision to precise presbyopia as well as myopia or hyperopia. Some multifocal lenses can correct astigmatism also.
  • Cosmetic contact lenses consist of color contacts premeditated to alteration or strengthen the eye color. Theatrical, Halloween and other special-effect contacts also considered as cosmetic lenses.

 More Fascinating Features to keep an eye on Contact Lenses:

  • Bifocal contacts for astigmatism -These are cutting-edge soft contacts which accurate both astigmatism and presbyopia, so that anybody can endure glasses-free also after the age of 40 if they are having astigmatism.
  • Contacts for dry eyes -Eyes can become uncomfortably dry at sometimes. Well, certain soft contact lenses are specifically made to decrease the hazard of this dry eye symptoms.
  • Colored lenses – Lenses in colors can definitely boost the natural beauty of eyes. They can make green eyes even greener or can change the color of eyes totally, as in from brown to blue.
  • Special-effect lenses – They are called novelty, or costume lenses, theatrical, special-effect contacts which can lead someone looking one step further making them look like a cat, a vampire, or another alter-ego of their choices. Remember Avatar, Mystique (X-Men Character), the Beast or any vampire character?
  • Prosthetic lenses -Colored contact lenses may be used for medical purposes too. Impervious soft lenses are known as prosthetic contacts which can be custom-designed for an eye when the eye has been blemished by injury or disease to cover the blemish and match with the appearance of another natural eye.
  • UV-inhibiting lenses -Some lenses help us to defend our eyes from the ultraviolet rays which can cause cataracts and other eye problems.

 New researches are emerging the modern era with explorations in the arena of contact lens, whether it is Biotrue Oneday lenses with recycling program to keep Mother Earth cleaner or Aquaform Technology to retain moisture in eyes even reducing blinking with Biofinity Energys. According to the report, “The global contact lenses market size was valued at USD 9.91 billion in 2016 and is expected to sustain its growth pace over the forecast period”. So true to say that the contact lenses are “As Modern as the World of Tomorrow”.

Vodafone India posts Rs 9,805 crore operating profit for 2017-18

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Vodafone India today posted operating profit of Rs 9,805 crore for the fiscal ended March 2018, largely on the back of Rs 3,850 crore gains from the sale of mobile towers.

 The UK based group had reported an operating loss of around Rs 30,690 crore for 2016-17 on account of Vodafone Group’s cutting down the valuation of its Indian business by taking gross impairment charge of 4.5 billion euro.

 Vodafone India, which is merging with Idea Cellular, expects the process to be completed by June, possibly making the latest results the last on standalone basis.

 Vodafone Group CEO Vittorio Colao said at a web conference that both the companies have already starting branding exercise for the new entity.

 The adjusted EBITDA of the company declined 34.5 per cent to around Rs 7,774 crore in 2017-18 from Rs 11,743 crore in the previous fiscal.

 Vodafone India continues to face tariff war heat and reported 18.7 per cent decline in organic service revenue to around Rs 35,045 crore in 2017-18 compared to Rs 42,927 crore service revenue registered in the preceding fiscal.

 “Intense competition is euphemism. There was 86 per cent decline in data price on year-on-year basis. Good news is that we have got 10 million customer in last quarter but there is a price to be paid for this success,” Colao said.

 The company added over 1 crore pre-paid customers but lost 5.76 lakh contract or post-paid customers in the January-March period.

 Data traffic on network of Vodafone India increased four fold but the company could not reap financial benefits because of sharp decline in data prices.

 Vodafone India service revenue declined by 21.2 per cent to Rs 7,750 crore in January-March 2018 period from Rs 9,835 crore it registered in the year-ago period. The average revenue per user of the company declined by 26 per cent to Rs 105 from Rs 142 during the quarters under review.

 The reduction in mobile termination rates added to the woes of the company.

 “Losses continued in India as service revenue declined 18.7 per cent as a result of intense price competition from the new entrant, aggressive competitor responses and a significant reduction in MTRs (mobile termination rates),” Vodafone said.

 It added that the impact of lower revenues was partially offset by significant actions to lower our operating cost base, as well as the benefit of a provision release in the fourth quarter following positive legal judgements.

Shrinking the synthesizer

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Only a few decades ago, finding a particular channel on the radio or television meant dialing a knob by hand and then making small adjustments to hone in on the right signal. That’s no longer the case, thanks to something called a radio-frequency synthesizer, which generates accurate signal frequencies.

While radio frequency control has long since been mastered, optical frequency control still exists in the bygone “tuner knob” era. This is because optical frequencies are so much higher (200 million megahertz) than radio frequencies (100 megahertz). Setting the absolute frequency, or color, of light emitted from a laser with precision is difficult because laser frequencies tend to drift as radio stations once did.

Optical frequency synthesizers provide unprecedented performance but until now have been large, expensive and power hungry. To address these limitations, the Defense Advanced Research Projects Agency (DARPA) in 2014 launched the Direct On-Chip Digital Optical Synthesizer (DODOS) program.

Now, a team of UC Santa Barbara scientists — including John Bowers, a professor of electrical and computer engineering, his colleague Luke Theogarajanand four UCSB graduate student researchers — has produced significant advances in chip-based integrated photonics and nonlinear optics that enable miniature, energy-efficient components for an optical synthesizer. Their findings appear in the journal Nature.

“We took something that occupied a whole optical bench, weighed 50 pounds and used a kilowatt of power and made it orders of magnitude more efficient by integrating the key elements onto silicon photonic integrated circuits,” said Bowers, UCSB’s Fred Kavli Chair in Nanotechnology and director of the campus’s Institute for Energy Efficiency.

Optical frequency synthesizers have proven extremely valuable in a variety of scientific endeavors, from searching the skies for far-off planets to detecting chemicals through sensitive laser spectroscopy and enabling high-precision light detection and ranging (LIDAR) by using light as a ruler to measure distance.

“The development of optical frequency synthesis has significantly enhanced our ability to accurately and precisely measure time and space,” said Gordon Keeler,the DARPA program manager leading DODOS. “However, our ability to leverage the technology has been limited. Through DODOS, we’re creating technologies that will enable broader deployment and unlock numerous applications. The goal is to shrink laboratory-grade capabilities down to the size of a sugar cube for use in applications like LIDAR, coherent communications, chemical sensing and precision metrology.”

Combining a pair of frequency combs, several miniature lasers and other compact optoelectronic components, the researchers were able to replicate the capabilities of a tabletop optical frequency synthesizer on three microchips, each less than 5 mm x 10 mm in size.

Theogarajan and his students designed and developed electrical integrated circuits to control the synthesizer, which can tune over 50 nanometers and deliver a frequency stability of 7 x 10-13 after one second of averaging — matching that of the input reference clock. A stable clock is important.

“The more accurate the clock is, the better you can resolve distance or velocity or do navigation,” Bowers explained. “GPS has a certain resolution. Your phone will locate you to within a few meters. But if you had a better, more stable clock, you could triangulate more precisely and get better resolution. It’s called PNT, for ‘precision navigation and timing.'”

The scientists created the two miniaturized frequency combs by circulating laser light generated with single-color “pump” lasers around optical racetracks fabricated on silicon chips. Doing so correctly can produce many additional colors, yielding a spectrum that looks like a hair comb where each “tooth” is an individual color or frequency. This is a significant departure from the tabletop version of an optical frequency synthesizer, which uses fiber optics, specialized mirrors and large mechanical components built by hand to achieve a similar effect.

The DODOS program is entering its final phase, during which researchers will work to integrate the individual components with electronics and fabricate a compactly packaged device suitable for use in future military and commercial optical systems. The synthesizer could have applications in navigation, spectroscopy and astronomy.

The goal, Bowers noted, is to make this very precise miniature laser cost almost nothing.