Lasers
The Einstein Telescope (ET) will be a very precise interferometer to measure gravitational waves. In the ET, a laser beam is split and sent in two different directions. The reflected laser light from the two directions is combined, which produces a specific interference pattern. Read more about the Lasers technology domain here.
The existence of a gravitational wave can be observed and confirmed by measuring the change in the interference pattern of the two laser beams.
This makes the laser one of the key technologies for the operation of the Einstein Telescope . The requirements for the lasers are exceptionally high. The laser source must have an extremely narrow line width and high stability. These qualities must be maintained, despite the fact that high power is also required. Laser sources are already quite common for a wavelength of 1064 nm. For the ET, new lasers must be developed that operate at wavelengths of around 1550 nm or 2090 nm.
For comparison, the human eye is sensitive to wavelengths from 380 nm (violet) to 780 nm (red), with a maximum sensitivity at 550 nm (yellow-green). The laser light from the ET is therefore in the infrared region, and is not visible to humans.
Lasers used in Gravitational Wave Detectors (GWD) use wavelengths of 1064 nm and 1550 nm. Fiber optic lasers for 2090 nm are commercially available, but their linewidths and laser frequency stability are not yet sufficient for use in the Einstein Telescope , especially not at the high powers of 700 W. Therefore, more research will be needed.
In the current design, a crystal-based oscillator seeder is used to generate the narrow linewidth laser radiation. The laser beam is then amplified using a two-stage holmium- doped fiber optic amplifier. Further boosting of the power using thulium -doped fiber lasers is currently being investigated.
The laser system to be developed will be the primary beam source of the interferometer. The laser beam will be generated with a crystal-based oscillator seeder . The further amplification of the laser light will be done with a two-stage fiber optic amplifier, for which the development is currently underway.
The laser source must meet the following specifications.
- Radiation source with an output power greater than 5W.
- Target wavelength of 2090 nm.
- Narrow line width.
- Linearly polarized.
- A very small diffraction loss (TEM00) of the laser beam.
- High power stability.
- High frequency stability.
For pumping this laser beam source, another beam source will be developed with the following parameters:
- Radiation source with an output power greater than 25 W.
- Intended wavelength of approximately 1950 nm.
- Linearly polarized.
- A very small diffraction loss (TEM00) of the laser beam.
- High power stability.
- High frequency stability.
When completed, the new lasers will have unmatched power stability, beam quality and linewidths at the new wavelengths.
- Sensors
- The new lasers can be used for LIDAR applications, such as distance sensors for autonomous driving in the new mobility. The human eye is not sensitive to the laser frequency, which prevents blinding when used for autonomous driving. Further research will have to show in which specific weather conditions (rain, snow) the new sensors can be used.
- Medical devices
- The frequency of the required laser can be used for numerous medical applications, such as surgery and urology.
- Gas detection
- Several gases (e.g. CO2) have absorption lines in the 2 µm wavelength range. Lasers with a low linewidth can therefore be used for the detection of these gases.