Integrated orbital angular momentum mode generator with wide spectral tunability [Invited]

We demonstrate tunable generation of orbital angular momentum (OAM) modes with low loss (0.7 dB) and high efficiency ( > 90 % ) over a 230 nm in the visible and near-infrared spectral range using all-fiber acousto-optic-induced long period gratings. This represents tuning over almost 33% of the carrier frequency, and measured output OAM mode purities are as high as 99%. Our device construction allows accessing any wavelength in the range we probed (591–818 nm) with at most a 55 µs response time. The high-speed tunability, large spectral coverage, and high mode purity can be potentially useful in numerous applications requiring spectrally diverse OAM light.