High-Brightness by Design

Brightness is a measurement of light power “concentration.”  Beam parameter product (BPP) is a laser specification indicating the beam “spread.”  For a given output power, the brightness is maximum when the BPP is smallest. 

The trick, then, is to design a system that has both high power and a small BPP.  High power blue lasers combine outputs of many individual diodes.  It takes some clever engineering to do this without making the BPP larger.  That’s important, because once the BPP gets larger, it can’t be made smaller. 

To optimize beam quality, the output of each of the many diodes needs to be circularized and collimated.  NUBURU does this with individual actively aligned micro-optics for each diode.  The individual beamlets are then spatially brought together.  That preserves the BPP while creating a high-power beam. 

As an alternative, consider diodes in a linear array — a bar.  Even if circularized, the beams are spread out.  When collimated and combined with a single lens, the angular divergence gets very large.  The BPP is then dominated by the angular spread.  And, once lost, the BPP can’t be recovered.  Larger BPP means smaller brightness, and that leads to lower power density and consequently longer processing times.

NUBURU’s approach maintains a small BPP, and that means higher brightness and higher power density.  For welding that means faster processing speed, deeper weld penetration, or both. 

You may not need to know the design details, but you need the end result: higher power density and improved performance.

Dr. Mark Zediker

FOUNDER AND CHAIRMAN

Dr. Zediker has over 30 years of experience as an entrepreneur. He has co-founded two other laser companies, Nuvonyx Inc. and Foro Energy Inc., and has successfully sold one of his companies to Coherent.

Mark graduated from the University of Illinois with a Ph.D. in Nuclear and Plasma Engineering in 1984; he received his M.S. in 1983, and his B.S. in Engineering Physics in 1978.

Integrating with Scanning Systems

Many materials processing systems would ideally be addressed with scanning systems. The general architecture of a scanning system calls for the laser beam to be steered at different angles to cover a given area. Just tilting the beam, however, leads to asymmetries and variations in power density across the field. Those effects can be minimized by using an F-theta lens — a lens fabricated to compensate for distortions across a given field. The laser beam on the input side of the lens is tilted, and on the output side it is displaced across a flat field specific to the design of the F-theta lens.

F-theta lenses, however, inherently enlarge the spot size at the focus. Low divergence — that is, high brightness — becomes a critical performance parameter. Consider the industry standard field of 100 X 100 mm at a working distance of 300 mm. To address this with a 400-µm spot the Beam Parameter Product needs to be better than 12, that is, less than 12.

Why a 400-µm spot? Because a 1.5 kW laser in a 400-µm spot delivers a power density  under the threshold for introducing spatter and voids.

Integrated with such a scanning system, the NUBURU AI-series enables the highest possible processing speed for defect-free copper welding.