Chinese scientists successfully develop world's first chip-scale titanium-doped sapphire laser

A research team led by Yale professor Hong Tang has developed the first chip-scale titanium-doped sapphire laser - an innovation that could lead to new applications such as atomic clocks, quantum computing and spectral sensors. The findings have been published in Nature Photonics [1].

Widest gain spectrum on a chip to date

The introduction of titanium-doped sapphire lasers in the 1980s was a major advance in the field of lasers. The key to its success lies in the material used as the gain medium, i.e., the material that amplifies the laser energy. Titanium ion-doped sapphire proved to be particularly powerful, providing a much wider bandwidth of laser emission than conventional semiconductor lasers. This innovation has led to significant discoveries and countless applications in physics, biology and chemistry.

Benchtop titanium sapphire lasers are essential equipment for many academic and industrial laboratories. However, the large bandwidth of such lasers comes at the cost of a relatively high threshold or required power. As a result, these lasers are expensive and take up a lot of space, which largely limits their use in laboratory research. If this limitation is not overcome, titanium sapphire lasers will remain limited to niche customers.

To this end, they have demonstrated the world's first titanium-doped sapphire laser with integrated chip-level photonic circuitry, which offers the widest gain spectrum on a chip to date - paving the way for numerous new applications. The performance of titanium sapphire lasers combined with the small size of the chip can drive power or space-constrained applications such as atomic clocks, portable sensors, visible light communication devices, and even quantum computing chips.

The key to success is the low threshold of the laser. While conventional titanium-doped sapphire lasers have thresholds in excess of 100 mW, the system they have developed has a threshold of about 6.5 mW. With further tuning, they believe it can be further reduced to 1 milliwatt. This system is also compatible with the gallium nitride optoelectronic family, which is widely used in blue light-emitting diodes and lasers.

Their prototype photonic circuit integrated with a titanium-doped sapphire laser opens up a reliable pathway to the next generation of broadband tunable lasers in active-passive integrated visible photonics.

About Professor Hong Tang

Hong Tang is currently the Llewellyn West Jones, Jr. Professor of Electrical Engineering at Yale University and received his PhD from Caltech in 2002. His research interests are in condensed matter physics and quantum physics, including nonlinear and quantum optics, nanoelectromechanical systems, superconducting detectors and circuits, and quantum transducer development. Current projects include quantum conversion from microwaves to photons, quantum networks and quantum communication, and superconducting quantum detectors.

Prof. Hong Tang

In January this year, Hong Tang's lab also developed the first realized on-chip photon number resolution (PNR) detector that can resolve up to 100 photons at a time.

Current photon counting devices are limited in the number of photons they can detect at a time, typically only one at a time and no more than 10 at a time. the Hong Tang lab's device not only increases the PNR capability by 100, but also improves the count rate by three orders of magnitude. It can also operate at easily accessible temperatures.

Building on their work, the researchers plan to make the device smaller and increase the number of photons it can detect. This includes increasing its photon count resolution to more than 1,000 using different dielectric materials.

Hong Tang has been honored with the 2010 Arthur Greer Memorial Award, the 2009 Packard Fellowship in Science and Engineering, the 2009 National Science Foundation Career Award, and the 2008 National Academy of Engineering (NAE) Symposium Invited Participant.

Reference Links：

[1]https://www.nature.com/articles/s41566-022-01144-2[2]https://seas.yale.edu/news-events/news/introducing-first-chip-sized-titanium-doped-sapphire-laser、