Power/Performance Bits: July 22

Lasers to replace quartz in electronics?
While nearly all electronics today require devices called oscillators that create precise frequencies, future high-end navigation systems, radar systems, and even possibly tomorrow’s consumer electronics will require references beyond the performance of quartz, according to researchers at Caltech.

In fact, these researchers have developed a method to stabilize microwave signals in the range of gigahertz, or billions of cycles per second—using a pair of laser beams as the reference, in lieu of a crystal.

They explained that quartz crystals “tune” oscillators by vibrating at relatively low frequencies—those that fall at or below the range of megahertz, or millions of cycles per second, like radio waves – but quartz crystals are so good at tuning these low frequencies that years ago, researchers were able to apply a technique called electrical frequency division that could convert higher-frequency microwave signals into lower-frequency signals, and then stabilize these with quartz.

Caltech’s new laser frequency reference (left) is a small 6 mm disk; the quartz “tuning fork” (middle) is the frequency reference commonly used today in wristwatches to set the second. The dime (right) is for scale. (Source: Caltech)

The new technique that the team has dubbed ‘electro-optical frequency division,’ builds off of the method of optical frequency division, developed at the National Institute of Standards and Technology more than a decade ago. This new method reverses the architecture used in standard crystal-stabilized microwave oscillators—the ‘quartz’ reference is replaced by optical signals much higher in frequency than the microwave signal to be stabilized.

Breakthrough broadband modulator
A UCLA research team has developed a broadband modulator that could eventually lead to more advanced medical and security imaging systems.

Modulators manipulate the intensity of electromagnetic waves, such as the modulators in cell phones convert radio waves into digital signals that the devices can use and understand. In terahertz-based communication and imaging systems, they modify the intensity of terahertz waves.

Today’s technologies take advantage of many parts of the electromagnetic spectrum — notably light waves and radio waves — but they rarely operate in the terahertz band, which lies between infrared and microwave on the spectrum.

Led by Mona Jarrahi, UCLA associate professor of electrical engineering, the group developed a terahertz modulator that performs across a wide range of the terahertz band with very high efficiency and signal clarity. Among the device’s advantages are that it could easily be incorporated into existing integrated circuit manufacturing processes, can operate at room temperature and does not require an external light source to operate.

Electron microscope image showing the metasurface for a terahertz modulator developed by a group led by UCLA professor Mona Jarrahi. (Source: UCLA)

Better batteries
A team at SLAC, is working to make a better battery by making the cathode of sulfur instead of today’s lithium-cobalt oxide.

Tucked in a small laboratory at SLAC National Accelerator Laboratory, a team of engineers and scientists from the Stanford Institute for Materials and Energy Sciences (SIMES) is making and testing new types of lithium-ion batteries. Their goal is to move beyond today’s lithium-ion to create a battery five times better than those we use now.