Octave-spanning CW supercontinuum laser has a 72 W optical output

Supercontinuum lasers rely on nonlinear optical interactions within optical fibers driven by lasers to produce broadband light, usually with near single-transverse-mode quality. Many, although not all, supercontinuum lasers rely on specially engineered fibers to produce nonlinear effects. Also, many but not all supercontinuum lasers are driven by pulsed lasers due to the greater light/matter interaction resulting from the high peak powers of the pulses. Continuous-wave (CW) supercontinuum lasers do exist, most of which rely on engineered fibers for enhanced nonlinear effects. Now, a group at the Centre for Nano Science and Engineering, Indian Institute of Science (Bangalore, India) has created a CW supercontinuum laser that is based on standard telecom optical fiber—and the device shows a record output power of about 72 W.

Standard single-mode fiber (SMF 28e) has a zero-dispersion wavelength (ZDW) at around 1.3 μm, offering a simple and cost-effective way to produce a high-power supercontinuum. The Bangalore group had previously demonstrated a CW supercontinuum laser with an all-fiber architecture and 34 W output, with the device power limited by the driving laser, which was a single source. In the new 72 W device, dual ytterbium (Yb)-doped fiber-laser modules operating at different wavelengths and spectrally combined are used to scale up the pump power. The result is a conversion efficiency of 44%, a spectrum ranging from 850 to beyond 1900 nm (greater than an octave), and nearly single-mode beam quality. Power spectral densities of >3 mW/nm from 850 to 1350 nm and >100 mW/nm from 1350 to 1900 nm have been obtained. Reference: S. Arun et al., Opt. Lett. (2020); https://doi.org/10.1364/OL.384690.