Wireless laser charging could redefine lifestyle

By Sudeep Sonawane
September 2, 2022

Scientists continue to race ahead with inventions and applications at incredible speeds. The application, reach, and impact of their innovations are far-reaching and frightening as well because it either out dates or make existing technology redundant.
Earlier this week, a report published by Science Daily says experts succeeded in transferring power 30 metres without wire by using infrared light.
Research applications are many. Some could make consumers’ lives easy and convenient. Many gadgets and feature phone-based applications have made life comfortable for the 21st century consumer.
Not all consumers can afford hi-tech gadgets. They make life easy for people who can buy them. Millions of low-income people living in under developing countries do not have the money to buy these costly mobile phones, tablets, and bluetooth devices.
Public places such as airport, bus stations and malls could offer this service of wireless charging via infrared either free or paid. How convenient for people to get their phone battery charged while buying groceries in a store!
Optics Express, a journal of Optica Publishing Group, first published the new research.
The new system uses infrared light to transfer safely high levels of power. Laboratory tests showed transfers of 400mW light power over distances of up to 30 meters. This power is enough to charge sensors.
The researchers beat challenges previously hindered attempts to develop safe and convenient mobile charging applications. Further fine-tuning could increase its levels enough to charge hand-held devices.
Commercial application of this research would make wall-mounted socket-based chargers with cables obsolete. A member of the research team corroborates this.
Sejong University, South Korea, research lead Jinyong Ha says, “The ability to power devices wirelessly could eliminate the need to carry around power cables for phones or tablets. It could also power various sensors such as those in Internet of Things (IoT) devices and sensors used for monitoring processes in manufacturing plants.”
Previous researchers had failed to transfer power wirelessly over long distances.
This research panel perfected distributed laser charging. This method delivers high-power illumination with less light loss.
Explaining the new method Ha says, “While most other approaches require the receiving device to be in a special charging cradle or to be stationary, distributed laser charging enables self-alignment without tracking processes if the transmitter and receiver are in the line of sight of each other. It automatically shifts to a safe low power delivery mode if an object or a person blocks the line of sight.”
Ha and fellow researchers used an erbium-doped fibre amplifier optical power source with a central wavelength of 1550nm. This wavelength range is in the safest region of the spectrum and poses no danger to human eyes or skin at the power used. Another key component was a wavelength division multiplexing filter that created a narrowband beam with optical power within the safety limits for free space propagation.
“In the receiver unit, we incorporated a spherical ball lens retroreflector to facilitate 360-degree transmitter-receiver alignment, which maximized the power transfer efficiency. We experimentally observed the system’s overall performance depended on the refractive index of the ball lens, with a 2.003 refractive index being the most effective,” says Ha.
The researchers demonstrated the system by setting up a 30-meter separation between a transmitter and a receiver. They made the transmitter from the erbium-doped fibre amplifier optical source, and the receiver unit included a retroreflector, a photovoltaic cell that converts the optical signal to electrical power and an LED that illuminates when it receives power. They integrated this receiver, around 10 by 10 millimetres, into devices and sensors.
The experimental results showed a single-channel wireless optical power transfer system could provide an optical power of 400mW with a channel linewidth of 1 nm over 30 meters. The photovoltaic converted this to an electrical power of 85mW.
The researchers showed the system automatically shifts to a safe power transfer mode when human hand blocked the line of sight. In this mode, the transmitter produced an incredibly low intensity light that did not pose any risk to people. The researchers now work on making this system more practical.

[Sudeep Sonawane, an India-based journalist, has worked in five countries in the Middle East and Asia. Email: [sudeep.sonawane@gmail.com]

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