New laser technology can make objects invisible

Agencies
September 14, 2017

London, Sept 14: Scientists have developed a cloaking technology that can make opaque materials invisible by using light waves from lasers, paving the way for novel ways of camouflaging objects.

A completely opaque material is irradiated from above with a specific wave pattern - with the effect that light waves from the left can pass through the material without any obstruction.

The technique can be applied to different kinds of waves, and should work with sound waves just as well as with light waves, researchers said.

"Complex materials such as a sugar cube are opaque, because light waves inside them are scattered multiple times," said Stefan Rotter, from Technische Universitat Wien (TU Wien) in Austria.

"A light wave can enter and exit the object, but will never pass through the medium on a straight line. Instead, it is scattered into all possible directions," said Rotter.

For years many different attempts have been made to outwit this kind of scattering, creating a "cloak of invisibility."

Special materials have been worked out, for example, which are able to guide light waves around an object. Alternatively, also experiments have been performed with objects that can emit light by themselves.

When an electronic display sends out exactly the same light as it absorbs in the back, it can appear invisible, at least when looked at in the right angle.

"We did not want to reroute the light waves, nor did we want to restore them with additional displays. Our goal was to guide the original light wave through the object, as if the object was not there at all," said Andre Brandstotter, one of the authors of the study.

"This sounds strange, but with certain materials and using our special wave technology, it is indeed possible," said Brandstotter.

To make the laser shine, energy has to be supplied by means of a pump beam. Otherwise, the laser material behaves just like any other material - it absorbs part of the incident light.

"The crucial point is to pump energy into the material in a spatially tailored way such that light is amplified in exactly the right places, while allowing for absorption at other parts of the material," said Konstantinos Makris from the University of Crete in Greece.

"To achieve this, a beam with exactly the right pattern has to be projected onto the material from above - like from a standard video projector, except with much higher resolution," said Makris.

If this pattern perfectly corresponds to the inner irregularities of the material which usually scatter the light, then the projection from above can effectively switch off the scattering, and another beam of light travelling through the material from one side can pass without any obstruction, scattering or loss.

"Mathematically, it is not immediately obvious that it is at all possible to find such a pattern," said Rotter.

"Every object we want to make transparent has to be irradiated with its own specific pattern - depending on the microscopic details of the scattering process inside," he said.

"The method we developed now allows us to calculate the right pattern for any arbitrary scattering medium," he added.

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Agencies
June 22,2020

Chennai, Jun 22: Commuting the death sentence to life imprisonment for five convicts, the Madras High Court on Monday set free Chinnasamy, the main convict, who had also been sentenced to death in the Udumalpet Shankar honour killing case.

A Division Bench comprising Justice M. Sathyanarayanan and Justice M. Nirmal Kumar also dismissed the appeal by the state police against the acquittal of three persons by a lower court.

The Bench ordered the five convicts sentenced for life to undergo a jail term of not less than 25 years.

In 2016, V. Shankar, who had married C. Kausalya, was killed by a gang in Udumalpet in Tamil Nadu. The gang also injured Kausalya in the attack.

It was alleged the parents of Kausalya -- Chinnasamy, Annalakshmi -- were against the marriage.

P. Pandidurai, the uncle of Kausalya at the behest of Chinnasamy and Annalakshmi had hired a gang to kill Shankar.

The gang killed Shankar in broad daylight in a public place and Kausalya too got injured in the attack as she tried to save her husband.

The Principal District and Sessions Court in Tiruppur had convicted and sentenced to death six accused persons -- Chinnasamy, P. Jagadeesan, P. Selvakumar, M. Manikandan, M. Mathan alias Michael and P. Kalaithamilvaanan.

The court also sentenced two other accused, K. Dhanraj for life and Manikandan to a five year jail term, while acquitting Annalakshmi, Pandidurai and Prasanna.

The convicts had filed an appeal against their sentence in the Madras High Court while the police filed an appeal against the acquittal of three persons.

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Agencies
June 18,2020

New Delhi, Jun 18: Vodafone Idea on Thursday told the Supreme Court that it has incurred Rs 1 lakh crore losses as it insisted it is not in a position to furnish bank guarantees.

A bench comprising Justices Arun Mishra, S. Abdul Nazeer, and M.R. Shah, taking up the adjusted gross revenue (AGR) matter through video conferencing, directed the telecom companies to submit their financial documents and books for the last 10 years.

Asking Vodafone if it was a foreign company, the bench said that how can the company say it would not furnish any bank guarantee.

"What if you fly away overnight in future without paying anything?" it asked.

Senior advocate Mukul Rohatgi, representing Vodafone Idea, denied his client is a completely foreign firm and cited before the bench its tie-ups and investments.

Vodafone owes over Rs 58,000 crore as AGR dues and so far, has paid close to Rs 7,000 crore.

Rohatgi contended before the court that the telecom company is in a tough situation, and cannot furnish any fresh bank guarantee, as profits have eluded the company in past many quarters. He submitted before the bench that Rs 15,000 crore bank guarantees are lying with the government, and his client's losses are over Rs 1 lakh crore.

"I cannot offer any more surety," he informed the bench.

Justice Mishra noted that this is public money and these dues should be recovered. "Do not tell us that you will pay if you were to make profits... the money must come," he noted.

Justice Shah observed that the telecom industry is the only industry which earned during the Covid-19 pandemic. "After all, this money will be used for public welfare", he said.

Rohatgi argued that his client would have to fold up if orders were issued to clear dues tomorrow. "11,000 employees will have to go without notice, as we cannot pay them," he added.

Senior advocate Abhishek Manu Singhvi, appearing for Bharti Airtel, contended before the court that out of Rs 21,000 crore AGR dues, the company has already deposited a sum of Rs 18,000 crore.

He argued that his client has given a bank guarantee, in excess of demand, to DoT, and supported the proposal for phased repayment of remaining AGR dues. He insisted that the company needs to sit down with the government and calculate the dues. Airtel owes Rs 25,976 crore after paying Rs 18,000 crore, as per the government.

Senior advocate Arvind Datar, representing Tata Telecom, informed the bench that his client has paid Rs 6,504 crore in AGR dues so far, and furnishing a bank guarantee may adversely impact investments in the sector.

The total AGR dues are close to Rs 1.5 lakh crore.

The top court will now take up the matter in the third week of July.

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Agencies
June 12,2020

Mumbai, Jun 12: Following an overwhelming response for the mega rights issue of Mukesh Ambani-owned Reliance Industries, the partly paid-up rights shares are set to debut on stock exchanges on June 15.

The biggest ever Rs 53,124 crore rights issue was subscribed 1.59 times and received bids worth Rs 84,000 crore on June 3.

Reliance said the rights issue saw a huge investor interest, including from lakhs of small investors and thousands of institutional investors, both Indian and foreign.

In 2019, Ambani said in the Reliance's annual general meeting that the company will be net zero debt by March 2021. The company is on course to achieve its target ahead of the deadline.

"In spite of the COVID-19 crisis and the lockdowns, the due-diligence by Saudi Aramco for the planned investment in the O2C business is on track as both the parties are committed and actively engaged," he said recently.

"With a strong visibility to these equity infusions, Reliance is set to achieve net zero debt status ahead of its own aggressive timeline. We believe rights issue was a part of the company's strategy of deleveraging its balance sheet," said Ambani. 

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