QCL: Boosting The Modulation Speed With Sound Waves

Lasers that switch on and off billions of times per second are the backbone of optical communications networks, but this feat is only possible at certain laser frequencies. A team of researchers has now taken a step towards extending this frequency range by using sound waves to modulate the emission of a terahertz (THz) quantum cascade laser (QCL).

In this new technique, the modulation rate is limited only by the duration of the acoustic pulse applied, meaning that rates of up to hundreds of gigahertz (GHz) are possible. It could transmit data at 100 gigabits per second – around a thousand times faster than current wireless systems, enabling faster medical sensing applications.

Although THz QCL signals have a shorter effective range than the microwave signals used in today’s wireless data systems, their higher frequency means they can carry more information over the same time frame. That makes THz radiation promising for ultra-fast, short-range data exchange – for example, across hospital campuses, between university research facilities, or in some satellite communications.

Researchers believe that audio modulation could be helpful in fields like high-resolution spectroscopy, active mode-locking, frequency comb synthesis, and high-speed communications. Ultimately, it enables them to investigate how THz sound and light combine, which may have practical technological implications.

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