- New electro-optic laser is 100 times faster than conventional ultrafast laser light.
- The system is reliable and produces accurate and stable pulses at 30 GHz.
- It can be used in biological/chemical imaging and to implement faster communication networks.
Ultrafast lasers generate a series of light pulses that last up to femtoseconds. They can function as frequency combs to provide a frequency and time reference bridging the microwave and optical domains of the electromagnetic spectrum.
Since the phase of these pulses can be controlled, it has a variety of applications ranging from steering quantum states of matter to optical atomic clocks. Although capabilities of ultrafast lasers have enhanced over years, they need an integral stability of the mode-locked resonator.
Now, researchers at the National Institute of Standards and Technology have come with an alternative approach that generates a series of optical pulses without mode locking. They are calling it electro-optic laser that emits pluses 100 times faster than traditional ultrafast laser. Basically, it’s electro-optic modulation of a laser developed with common electronics.
How It’s Different From Ultrafast Lasers?
Although the idea of building an electro-optic is quite simple and the technology has been around for almost 50 years, scientists haven’t been able to switch light to emit ultrafast pulses while eliminating electronic interference.
Usually, the mode-locking method involves bouncing light back and forth in a mirrored cavity in such a manner that waves constructively interfere with each other to produce short pulses. However, the new technique works on a more brute force mechanism: it carves up a continuous laser beam into separate pulses, reducing the heat-induced interference.
As the signals bounce back and forth inside the cavity, fixed waves appear at highest frequencies, blocking all other frequencies. Signal stabilization and filtration are done within this cavity.
More specifically, they used an infrared laser (emitting continuous wave) to generate pulses with an oscillator stabilized by a customized cavity. All pulses are uniform and passed through a microchip waveguide structure to produce different colors in the frequency comb.
Reference: ScienceMag | doi:10.1126/science.aat6451 | NIST
An optical frequency comb is used as a source in the traditional ultrafast light. Such combs are built with mode-locked lasers that create pulses from several light waves colors overlapping with each other and forming links between microwave and optical frequencies. The electro-optic laser, on the other hand, applies electronic vibrations on an infrared laser, efficiently shaping pulses into the light.
Electro-optic laser isolates light of particular frequencies to form a frequency comb of different colors | David Carlson/NIST
The mode-locked lasers generate pulses at every 10 nanoseconds, whereas electro-optic laser takes only 100 picoseconds to generate one pulse (100 times faster).
To construct the electro-optic laser, researchers chose to use only commercially available microwave and telecommunications instruments. This makes the system more reliable. Also, its stability and accuracy are pretty decent, making it suitable for faster communication systems and long-term measurement of optical clock networks.
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Moreover, this kind of laser can be used in biological and chemical imaging to speed up specific types of imaging of tissues/chemical. For example, hyperspectral imaging that usually takes a minute could be performed in real-time.
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