Metrology of laser beams with high power has a number of challenges related to beam sampling technique, sensitivity control for the measurement device and achievable dynamic range. Main Objectives: development of an inexpensive, compact device for measurement of laser beam profile (LBP) and beam pointing stability (BPS) measurement device for pulsed and continuous high power lasers based on in-line beam sampling with continuous control of the laser intensity over very large dynamic range (>100dB).
State of the art: Lasers revolutionised internet communication through fibre, 2D and 3D printing, surgery, data storage on CD and DVD, spectroscopy, surgery, and material processing through extremely advance control of light field. Next envisioned revolution is related to the power increase of lasers, as confirmed by 2018 Nobel Prize in physics for advances in high power lasers for Donna Strickland and Gerard Mourou. Not only pulsed lasers but also continuous wave lasers advanced tremendously in terms of delivered power per unit price. To achieve large powers, an architecture master oscillator with multiple power amplifier stages is widely used. In this way, the output power of the laser beam varies several orders of magnitude, becoming destructive for most of the laser beam profiling systems.
Limitations: At large power levels, laser become self-destructive. Measuring the spatial structure of the laser electromagnetic field (EMF) becomes critical for machine operation, maintenance, and safety. The existing approaches based on video cameras coupled to optical glass filters, partially reflective coatings and control of polarisation with wave-plates have drawbacks such as: large size, discrete variation of the intensity sampling, limited dynamic range to <50dB and distortion of the measured beam.
Breakthrough: Here it is proposed a compact, all reflective laser beam profiler (LBP) with built in continuously variable attenuator with very low losses for beam apertures up to few cm, continuously tunable in transmission over 100dB (five orders of magnitude improvement against existing technologies), coupled to a sensor, allowing very simple diagnostics of high power lasers. With simple modifications it will also be used as beam pointing stability (BPS) measurement device.
The increase in the dynamic range will impact technologies using high power lasers such as additive manufacturing, surgery, materials science, and laser research facilities that produce applications for space science and radio-medical treatments. In particular, IFIN is hosting a research infrastructure Extreme Light Infrastructure Nuclear Physics, which will directly benefit from the technology proposed.