Even if a laser is designed to emit purely in one wavelength, changes in temperature and other environmental factors often introduce noise that causes the light emission to shift or broaden in frequency. The broadened spectral extent of this emission is known as the laser linewidth. The researchers used a new approach to create an optical fiber laser with a spectral linewidth narrower than ever achieved by a fiber or semiconductor laser. The same laser also provides a method to sense and correct for temperature changes as small as 85 nanoKelvin, or 85 billionths of a degree.
“Today, ultra-low expansion (ULE) cavity lasers exhibit the narrowest linewidth and highest performance, but they are bulky and very sensitive to environmental noise,” said William Loh, the paper’s first author. “Our goal is to replace ULE lasers with one that could be portable and isn’t sensitive to environmental noise.”
Achieving narrow linewidth
The researchers developed a laser based on a short loop (~2 meters) of optical fiber configured as a ring resonator. Fiber lasers are compact and rugged and tend to react relatively slowly to environmental changes. The researchers combined the advantages of fiber with a nonlinear optical effect known as Brillouin scattering to achieve a laser with a linewidth of just 20 hertz. For comparison, other fiber lasers can achieve linewidths between 1000 to 10,000 hertz, and off-the-shelf semiconductor lasers typically have a linewidth of around 1 million hertz.
To make the laser extremely stable in the face of long- and short-term environmental changes, the researchers developed a way to reference the laser signal against itself to sense temperature changes. Their method is highly sensitive compared to other approaches for measuring temperature and allows the calculation of a precise correction signal that can be used to bring the laser back to the emission wavelength of the original temperature.
“Temperature is an important contributor to laser noise,” said Loh. “A high-quality laser needs to not only have a narrow laser linewidth but also a way to keep that emission stable over the long term.”
This new light source could be used to improve a new generation of optical atomic clocks used for GPS-enabled devices. GPS enables users to pinpoint their location on Earth by triangulating with the signals received from a network of satellites containing advanced atomic clocks. Each satellite provides a time stamp, and the system calculates a location based on the relative differences among those times.
“We think that atomic clocks based on our stable, narrow linewidth laser could be used to more precisely pinpoint the signal’s time of arrival, improving the location accuracy of today’s GPS systems,” said Loh. “The fact that our laser is compact means it could be used aboard satellites.”
The laser could also be beneficial for interferometers like the ones used by the Laser Interferometer Gravitational-wave Observatory (LIGO) to detect gravitational waves coming from colliding black holes or collapsing stars. Ultrastable lasers are necessary for this application because laser noise prevents the interferometer from being able to detect the very small perturbations of a gravitational wave.
“There are efforts underway to use lasers in space to create longer interferometer arms for gravitational wave observation,” said Loh. “Due to its compact size and robustness, our laser might be a candidate for gravitational wave detection in space.”
The researchers say that although their new laser is robust, it is currently a benchtop system suitable for laboratory use. They are now working to develop smaller packaging for the laser and will incorporate smaller optical components to create a portable version that might be as small as a smartphone.
Opera 54 builds blockchain into browser
Opera has announced that it is the first major browser to integrate a crypto wallet to enable access to a range of blockchain services.
Opera has added cryptocurrency capabilities to its latest version of its Opera browser for Android – Opera for Android 54. This version of the browser integrates Bitcoin (BTC) and TRON payments to its crypto wallet, along with a refreshed user interface (UI) with ten new colour themes.
The Android version of Opera had supported Ethereum only, and has now added support for Bitcoin and TRON, enabling payments and transactions to be made directly in the browser without any extensions. By opening its Crypto Wallet to some of the world’s most popular cryptocurrencies, Opera is making it possible to send and receive these virtual currencies directly from the browser in the same way one would send or receive an image or music file.
Opera also now supports online payments with blockchain where merchant support exists. This means users can pay with their cryptocurrency that’s a built-in wallet, including sending person-to-person and interacting with websites to pay for goods or services.
Stefan Stjernelund, Product Manager of Opera for Android, says: “We realise that mobile browsers are no longer just a means to connect users to the internet – they have evolved into multipurpose tools that are actively removing the barriers to owning and transacting using cryptocurrencies.”
Now for ‘transition focus’
Opera has added a splash of colour to its user experience. The browser’s upgraded UI focuses on reducing unnecessary distractions by introducing a new concept called “transition focus”.
“Transition focus is a beautiful interface that features a clean, bloat-free design to ensure features like a free unlimited VPN, a built-in ad blocker and the Crypto Wallet that can be accessed quickly and fluidly,” says Stjernelund.
Opera has added ten colour options that enable users to adjust the browser to their taste and preference. The browser’s colour themes can match the Android system’s dark or light mode or be set up independently.
Stjernelund says: “We want the Opera browser to set a new standard among browsers by providing the features that a modern browser should have. With this version, we are ushering in a series of design changes and digital tools that speak to the future of browsing, one that goes beyond just connecting users to the internet.”
Opera continues to provide an integrated news service – Opera News – that keeps users up to date with current affairs. It also includes a cleaner design with integrated night mode to put less strain on readers’ eyes.
Opera for Android 54 is available for download on the Google Play Store.
Vodacom launches 4G smart feature phone
Vodacom has launched the Vibe 4G, which is a smart feature phone with 4G and sells for R299, packaged with a free data allocation.
Today, Vodacom launched a 4G smart feature phone, the Vodacom Vibe 4G, at only R299. The mobile operator says the device is designed for customers who are looking at getting their hands on a smart yet affordable device, and to help them connect to social media platforms.
This smart feature phone runs on a proprietary operating system, but still runs WhatsApp like other smart feature phones.
The Vibe 4G follows the successful launch of Vodacom’s first smart feature phone, the Vodacom Vibe 3G. it includes a bumped up 2.8-inch display, familiar feature phone menu navigation, long-battery life and a 2MP rear camera.
Using 4G equates to a faster social media surfing and instant messaging experience, as well as enabling Voice over LTE (VoLTE), which ensures calls can be made in some cases when the 2G network is unavailable. The device also has Voice over Wi-Fi (VoWiFi) capability, which enables users to make calls using a Wi-Fi network for better-sounding voice calls.
“In the past six years, smartphone penetration has doubled from 30% to 60% as customers migrate from 2G devices to 3G and 4G smartphones,” says Davide Tacchino, terminals managing executive at Vodacom. “To further drive this transition and help bridge the digital divide, we have now introduced South Africa’s first 4G feature phone for just R299, having launched the country’s first smart feature phone with a traditional keypad during the course of last year.”
Vodacom says that its focus is not only on selling mobile devices, but it is also determined to create an ecosystem, enabling its customers to access educational content through Vodacom’s e-School as well as entertainment content, through Video Play.
Vodacom Vibe 4G retails at R299 at Vodacom stores and other participating outlets. Customers purchasing the device will also get 150MB of data, per month over 12 months. This will keep customers connected and, at the same time, allow them to experience the functionality of 4G connectivity.
For more information, visit www.vodacom.co.za