September 2020
Spotlight Summary by Jonathan Bradley
Spectroscopy of thulium-doped tantalum pentoxide waveguides on silicon
Lasers operating near 2 µm wavelength have recently attracted significant interest for applications in communications, medicine, sensing and spectroscopy. Thulium-doped waveguides are particularly promising for such applications because of thulium’s broad emission around 1.7-2.1 µm and efficient optical pumping at a wavelength of 790 or 1600 nm, the former with low-cost pump diodes and the latter allowing for commercial pump sources in the standard communications L band. Thulium lasers can reach efficiencies > 80%, in a wavelength region where semiconductor lasers are well-known to drop off in efficiency and increase in cost, which enhances thulium lasers’ prospects as light sources in photonic microsystems. Integrating such lasers on a silicon chip, as opposed to more well-developed bulk glass or fiber-optic platforms, adds the advantage of compact size and allows for co-integration with other well-established silicon-based integrated photonic components.
In this work, A. S. K. Tong and colleagues present on low-losses, spectroscopic measurements, and demonstration of lasing around 1860 nm in thulium-doped tantalum pentoxide waveguides on silicon. Tantalum pentoxide is a highly prospective CMOS-compatible material which has received much recent attention in the integrated photonics community, but prior to this work had been less explored as a rare-earth host material for thulium. Here, the authors have fabricated thulium-doped ridge waveguides using similar methods to those which their research group has used to demonstrate erbium-, neodymium- and ytterbium-doped devices. They characterize the fluorescent lifetime, showing a factor of ~5 increase in the thulium excited state 3F4 lifetime (up to 477 µs) with annealing at temperatures up to 650 °C. They also characterize the absorption and emission spectra and cross-sections for the Tm3+:Ta2O5 system, providing the groundwork for future device design and development on this promising platform. Importantly, they show laser emission at 1238, 1855 and 1858 nm in a 1-cm-long waveguide with polished end facets. From the laser results they deduce a very high gain in the material of 9 dB/cm, which is also promising for compact integrated amplifiers. These results add to many other recent advances on tantalum pentoxide photonic integrated circuits, including the development of low-loss waveguides and high-speed all-optical nonlinear devices. Thulium lasers are an important step for such circuits because they can provide efficient, high power light sources to power near to mid-infrared all-optical processes on the same chip, for many emerging applications including AI and quantum optics.
You must log in to add comments.
In this work, A. S. K. Tong and colleagues present on low-losses, spectroscopic measurements, and demonstration of lasing around 1860 nm in thulium-doped tantalum pentoxide waveguides on silicon. Tantalum pentoxide is a highly prospective CMOS-compatible material which has received much recent attention in the integrated photonics community, but prior to this work had been less explored as a rare-earth host material for thulium. Here, the authors have fabricated thulium-doped ridge waveguides using similar methods to those which their research group has used to demonstrate erbium-, neodymium- and ytterbium-doped devices. They characterize the fluorescent lifetime, showing a factor of ~5 increase in the thulium excited state 3F4 lifetime (up to 477 µs) with annealing at temperatures up to 650 °C. They also characterize the absorption and emission spectra and cross-sections for the Tm3+:Ta2O5 system, providing the groundwork for future device design and development on this promising platform. Importantly, they show laser emission at 1238, 1855 and 1858 nm in a 1-cm-long waveguide with polished end facets. From the laser results they deduce a very high gain in the material of 9 dB/cm, which is also promising for compact integrated amplifiers. These results add to many other recent advances on tantalum pentoxide photonic integrated circuits, including the development of low-loss waveguides and high-speed all-optical nonlinear devices. Thulium lasers are an important step for such circuits because they can provide efficient, high power light sources to power near to mid-infrared all-optical processes on the same chip, for many emerging applications including AI and quantum optics.
Add Comment
You must log in to add comments.
Article Information
Spectroscopy of thulium-doped tantalum pentoxide waveguides on silicon
Amy S. K. Tong, Colin J. Mitchell, Armen Aghajani, Neil Sessions, G. Senthil Murugan, Jacob I. Mackenzie, and James S. Wilkinson
Opt. Mater. Express 10(9) 2201-2211 (2020) View: Abstract | HTML | PDF