Group develops first-ever evolutional femtosecond laser system
-Set-up and initial alignment time reduced by 99%—
-Potential for industrial applications expand due to automated alignment capability and small size-

The National Institute of Advanced Industrial Science and Technology (AIST) has developed a system to align and optimize a femtosecond laser in 30 minutes (less than 1% of the time required with previous technologies), through the development of an automatic alignment system using a genetic algorithm.

Until now, laser alignment has relied on expert manipulation. The new system uses digital processing based on a genetic algorithm, enables alignment to be completed in a shorter period of time, and ensures reproducibility and reliability. The potential for femtosecond laser system applications has been increased because of the improved reproducibility and reliability, both of which are crucial in system applications.

The automatic control system developed is expected to significantly reduce production and maintenance costs and to dramatically accelerate development of products for practical applications. Moreover, as the alignment does not rely on human adjustments, the laser device itself can be made smaller and lighter. Previously, femtosecond lasers could only be used in clean room environments, but use should now be possible in a range of other environments because of the automatic alignment system that enables the device to be optimized on site.

Femtosecond lasers store light internally at levels on the order of megawatts (1-million W). Therefore, the lasers need to have various optical components accurately distributed internally on a scale of micrometers. There are over ten alignment locations and a change in just one location produces a large effect on optical power, wavelength, and pulse width. Therefore, until now, femtosecond laser set-up took around 1 week for an expert to complete.

To summarize the problems with the current system:
(1) Optimal laser alignment takes a long time (low throughput and high production costs).
(2) Different performance depending on the skill of the person conducting the alignment (no reproducibility).
(3) Experts required for device maintenance and repair (high maintenance and repair costs).

AIST has developed the evolutionary femtosecond laser system, the first-ever automatic alignment system based on a genetic algorithm. The evolutionary femtosecond laser system includes a small-scale position sensor and a small-scale actuator, which enables precise measurement in real time of the optical component locations within the laser. The data from the location sensor is processed using the genetic algorithm, enabling automatic optimization of the optical component locations by the actuator.

The system allows simultaneous control of the position of 12 locations and enables alignment to be completed in 30 minutes, less than 1% of the time required in previous systems. After alignment, the system can be used to maintain the laser in its optimal state by adapting to any external disturbances. As a result, the femtosecond laser system set-up can be automated and no longer needs to rely on expert manipulation. This is expected to allow a 100-fold increase in production efficiency. The laser can also be maintained in an optimal state even if there are external changes, such as temperature changes.

The evolutionary femtosecond laser system should enable a dramatic improvement in femtosecond laser system reliability and is expected to increase the potential for industrial applications.

This automated alignment method using a genetic algorithm is expected to have applications in other non-laser optical systems. For example, it is already being used in experiments to optimize the connection between optical fibers and researchers have achieved good connection efficiency in short periods of time, compared with existing systems. Where previous optical fiber connections took an expert 20–30 minutes to achieve, the new system allows the process to be completed in around 3 minutes. Moreover, the team plans to use the automated control system in mounting technologies for optical components.