Beam expansion is bought for three practical reasons. A larger beam focuses to a smaller spot, which is why expanders sit before the focusing and scanning optics of marking and micromachining systems. A larger beam also diverges more slowly, which keeps long delivery paths usable. And a smaller beam — expanders run in reverse as reducers — fits apertures that the raw laser output would overfill. In each case the expander's job is to change the diameter while preserving collimation, and its expansion ratio is the headline specification.
The manufacturer's documented position for this product is the lens device group, where beam expanders are catalogued with the F lenses (F-theta scan lenses) and telecentric lenses. The laser scanning chain runs expander, galvo mirrors, scan lens, and the three are best specified together: the expanded beam diameter must match the galvo aperture, and the scan lens's entrance pupil must accept what the expander delivers. The scan lenses page covers the downstream half of that chain.
Specifying a Beam Expander
- Expansion ratio — output diameter divided by input diameter; state it, or state both diameters.
- Wavelength — the design and coatings are band-specific.
- Input beam diameter — the raw beam the expander must accept without clipping.
- Adjustability — fixed-ratio, or adjustable divergence for focusing trim over the working distance.
Beam expanders are configuration-led products within a documented family, so pricing and minimums are confirmed per specification in the written quotation. Include the laser wavelength and the two beam diameters in the first message, so the configuration can be confirmed against them in the quotation.
Frequently Asked Questions
Why expand a beam before a scan lens?
A larger entrance beam focuses to a smaller spot and matches the scan lens's pupil to the galvo mirrors. The expansion ratio, the galvo aperture and the scan lens you are working with belong in the enquiry.
Can an expander also reduce a beam?
Yes — reversed, the same telescope geometry reduces diameter while keeping the beam collimated.
What does the quotation need?
Wavelength, input beam diameter and required output diameter (or the expansion ratio).
Fixed, Zoom and the Divergence Adjustment
Beam expanders divide into fixed-ratio and adjustable families, and the division is a system decision. Fixed designs give one expansion with the simplest, most stable construction. Adjustable designs add a divergence trim: a small, deliberate departure from perfect collimation that moves the focus or compensates a real laser's actual divergence. State in the enquiry whether the beam train is still being aligned or the laser may be swapped, and whether the beam size is a settled number, so the fixed or adjustable form is confirmed against the system as it stands. A second practical note concerns orientation: an expander accepts the small beam at one end and delivers the large beam at the other, and reversing one changes its ratio to the reciprocal — obvious on paper, easily confused in ordering, and worth one confirming sentence in the enquiry stating the input diameter and the required output diameter in that order. In the source catalogue the beam expander is grouped under Lens Device, alongside the F lens (F-theta) and telecentric lens lines.
Request a Quotation
Tell us the component, material, dimensions and coating you need. Pricing and lead time for your specification are confirmed in the written quotation.