Visible Broadband Source

A Visible Broadband Source is a high-brightness, spatially coherent light source that emits a continuous (or quasi-continuous) spectrum spanning much of the visible range (~400–700 nm), often extending into the near-IR. It combines the spectral width of a lamp with laser-like beam quality, directionality, and brightness.

The dominant implementation is a fiber supercontinuum (SC) source.

How it is generated:

A pulsed pump laser (commonly 800 nm Ti:sapphire or ~1060 nm fiber/microchip laser, femtosecond to nanosecond pulses) is launched into a highly nonlinear medium—most often a photonic crystal fiber (PCF) or other specialty fiber. 

Multiple nonlinear processes act together:

• Self-phase modulation.

• Four-wave mixing.

• Soliton fission and Raman scattering.

• Cross-phase modulation.

These processes massively broaden the spectrum while preserving a single spatial mode. Pumping in the anomalous-dispersion regime typically yields broader but noisier continua; all-normal-dispersion (ANDi) designs produce flatter, more coherent spectra at the cost of some bandwidth.

Commercial examples (NKT Photonics SuperK FIANIUM, COMPACT, EVO, etc.) typically cover 390–2400 nm with visible-band power from tens of mW to >2 W, single-mode output, and high long-term stability. Other approaches include fiber Cherenkov radiation sources, multi-SLD combinations, or frequency-doubled/swept NIR sources, but SC lasers are the most common “visible broadband source” in research and industry.

Key properties versus lamps or LEDs:

• Spectral brightness orders of magnitude higher.

• Diffraction-limited or near-diffraction-limited beam.

• Fiber delivery possible.

• Pulsed (useful for time-resolved work) or effectively CW after averaging.

• Can be filtered, polarized, or made tunable with accessories.

Applications:

• Visible-light optical coherence tomography (vis-OCT) — higher axial resolution and access to hemoglobin absorption for retinal oximetry.

• Spectroscopy and hyperspectral imaging.

• Confocal, multiphoton, and STED microscopy.

• Fluorescence lifetime imaging and flow cytometry.

• Photonic component characterization and test & measurement.

• Semiconductor inspection.

• Frequency metrology (when the SC is coherent enough to support a frequency comb).

• Biomedical sensing and imaging where visible wavelengths provide molecular contrast that NIR sources lack.

The combination of laser-like spatial properties and lamp-like spectral coverage makes these sources especially useful wherever a single compact source needs to replace multiple discrete lasers plus a broadband lamp.