Quantum gravity sensing

Get accurate information about underground infrastructure.

Accurate quantum gravity sensors

Quantum gradiometers, gravity sensors, or gravimeters, allow you to accurately map local variations in gravity to ensure infrastructure integrity and safer constructions. They are great tools for, e.g., civil engineers, land surveyors, and railroad companies.

The most sensitive gravity sensors use atom interferometry on atoms cooled close to absolute zero and placed in a free fall. In a free fall, the distance traveled over a period of time is determined by the local gravitational pull.

You need accurate lasers to cool atoms

Laser cooling is a critical step that requires a tunable narrow-linewidth high-power laser such as our Koheras BASIK. Rubidium ions are typically cooled in a magneto-optical trap, MOT. A MOT uses a combination of magnetic fields and a narrow-linewidth high-power laser at 780 nm to cool and trap the ions and place them in an appropriate quantum state for further investigation by, e.g., atom interferometry.

We shoot light pulses at atoms as they undergo free fall. Each atom has a certain probability of absorbing a light pulse, and if it does, it slows down. The atoms that are slowed down do not travel as far as those not slowed down, which leads to two vertically separated outcomes with a relative distance determined by the gravitational pull.

Rubidium ions are often used in gravitational sensors. If you carefully observe the free-fall acceleration, you can determine the local gravity and reveal even the tiniest variations created by dense objects or underground cavities.

Pick a stable laser

When you look for a laser for a gravitational sensing system, pick a stable one. The system will be moved around a lot and must keep its stability and precision. A fiber laser is a good choice because it contains no moving parts and is intrinsically stable.

The Koheras DFB fiber lasers are well known for their unmatched Hz-level linewidth at watt-power levels. But DFB fiber lasers only come in a few infrared wavelength bands. And these bands rarely match the wavelengths needed for laser cooling of atoms and ions.

Frequency conversion gives you 780 nm

We suggest seeding an Erbium-Doped Fiber Amplifier (EDFA), such as the Koheras BOOSTIK HP, with a stable narrow linewidth seed laser such as the Koheras BASIK at 1560 nm. Use the Koheras HARMONIK frequency conversion module to efficiently convert the high-power light at 1560 nm into high-power light at 780 nm.

You get a 780 nm fiber laser system at watt level with a beam quality M2 ≈ 1.1 and a free-running linewidth less than 1 kHz – the ideal laser system for any Rb atom interferometer.

Frequency conversion is a nonlinear process. The HARMONIK frequency conversion module only converts the main laser signal while cleaning up any unwanted power at out-of-band wavelengths present in most lasers.

Robust enough for oil rigs yet sophisticated enough for the lab

Our fiber laser design is inherently compact and robust. It is developed for a lifetime of above 10 years in demanding environments where uptime is critical. With failure rates lower than 1%, we proudly deliver the most reliable low-noise lasers on the market. Alignment-free and maintenance-free.

The industrial-grade OEM lasers have a rugged design, a stable performance unaffected by changing environmental conditions, and wide temperature ranges in the field as well as the lab. We deliver lasers to the most advanced laboratories worldwide such as the UK Quantum Technology Hub for Sensors and Timing at the University of Birmingham and the Institute of Quantum Optics at Leibniz University Hannover.

We have more than 15,000 Koheras lasers deployed in the harshest environments on – and off – the planet. We have lasers on oil rigs, submarines, wind turbines, and even in space. With over 20 years of experience, we know they last. Also in your lab.

References

Our quantum engagements

We are part of the European Quantum Flagship, the European Quantum Industry Consortium, the Quantum Economic Development Consortium, and the Danish Quantum Community.