Portable lasers could be key to gen-next sensors

Researchers, including those of Indian-origin, have developed a custom-tailored, compact laser diode smaller than a penny which can help improve detection of chemicals, including explosives, industrial and pollutants.
This is the first time a single-laser diode demonstrated the ability to emit light at frequencies within 30 per cent of the laser central frequency.
Chemicals around and within us can tell many complicated stories, the researchers said.
By sensing them, security agents can uncover explosive threats, by monitoring them in our breath, doctors can diagnose serious illnesses, and by detecting them on distant planets, astronomers may find signs of life.
These chemicals sometimes show their secrets when probed with mid-infrared wavelength lasers.

Nearly all chemicals, including explosives, industrial, and pollutants, strongly absorb light in the mid-infrared wavelength region, which is often called the "fingerprint region" for chemicals, the researchers said.

However, lasers that work within this range have limitations. Larger, optically pumped lasers are too complex to use out in the field, and compact, lightweight diode laser sources have a limited spectral range.
Researchers at Northwestern University's Centre for Quantum Devices in US, including N Bandyopadhyay and S Sengupta, have used quantum mechanical design, optical engineering, and materials development to create a custom-tailored, compact laser diode by integrating multiple wavelength emitters into a single device.

Capable of emitting broadband wavelengths on demand, the device is smaller than a penny and works at room temperature.
It can also emit light at frequencies within 30 per cent of the laser central frequency, which has never before been demonstrated in a single-laser diode.
"When we started, we knew this technology had great potential," said corresponding author Manijeh Razeghi, professor of Electrical Engineering and Computer Science at Northwestern's McCormick School of Engineering.
"We can access any frequency in the laser's range on demand at room temperature, which is ideal for sensing applications," she said.
The study was published in the journal Optics Express.