Prototype of a new kind of ultrafast laser. [Image: Simone Bianconi, EPFL]
Pockels cells give many types of lasers, from giant research instruments to small telecommunications devices, their ability to deliver precisely controlled light pulses. European researchers have developed a hybrid integrated Pockels laser that fits on a photonic chip, exhibits a wide tuning range and delivers 15 mW of output power.
The new wafer-scale device gets its improved performance from an external distributed Bragg reflector combined with a semiconductor optical amplifier (Nat. Photonics, doi: 10.1038/s41566-025-01687-0). The scientists tested the Pockels laser in lidar and spectroscopy experiments, and they say that it could be leveraged for other metrological applications.
The tuning boost
Scientists already know how to lock distributed-feedback laser diodes to Pockels-type resonators based on thin-film lithium niobate to build tunable lasers on a chip. Previous lasers of this type, however, had a limited tuning range—roughly five times too narrow for applications in molecular spectroscopy.
The team at the Swiss Federal Institute of Technology Lausanne (EPFL), Switzerland, and the Norwegian University of Science and Technology (NTNU), Norway, coupled an indium phosphide reflective semiconductor optical amplifier (RSOA) to a single-crystal lithium-niobate photonic circuit containing an extended distributed Bragg waveguide grating reflector 7.25 mm long.
The scientists measured the device’s tuning range at greater than 10 GHz, with a tuning efficiency of more than 550 MHz/V.
Using an RSOA as a gain medium simplifies and reduces the cost of the laser design, according to the researchers. Gold electrodes on both sides of the Bragg reflector created the Pockels tuning effect. The scientists measured the device’s tuning range at greater than 10 GHz, with a tuning efficiency of more than 550 MHz/V. “Our results can give us a new type of laser that is both fast, relatively cheap, powerful and easy to use,” said Johann Riemensberger, NTNU.
Testing and next steps
As a proof-of-concept study, the Swiss-Norwegian team tested the new laser in a setup for long-range frequency-modulated continuous-wave lidar in a laboratory environment. The device captured 20,000 voxels in just 100 ms.
Next, the researchers tried using the hybrid laser to pick up the hydrogen cyanide absorption line at 1545 nm. The device demonstrated long-term stability with a frequency deviation of less than 25 MHz over two and a half hours of continuous observations.
The team says its results demonstrate that the laser has the stability and simplicity of operation as well as the tuning range and linearity needed to potentially be used for spectroscopy. They plan on continuing to develop the technology for such applications.
