Russian Scientists Integrate Microdisk Laser and Waveguide on a Single Substrate
A group of Russian scientists led by Professor Natalia Kryzhanovskaya at HSE Campus in St Petersburg has been researching microdisk lasers with an active region based on arsenide quantum dots. For the first time, researchers have successfully developed a microdisk laser coupled with an optical waveguide and a photodetector on a single substrate. This design enables the implementation of a basic photonic circuit on the same substrate as the radiation source (microlaser). In the future, this will help speed up data transfer and reduce equipment weight without compromising quality. The study results have been published in Semiconductors.
The growing demands for higher speed and larger volumes of transmitted information necessitate improvements to current communication methods. Photonic integrated circuits (PICs), which use light to transmit information, operate faster, generate less heat, are more resistant to interference, and consume less energy compared to their electronic counterparts.
However, their effective use requires efficient, compact light sources, such as gallium arsenide (GaAs) microdisk lasers. The length of a conventional Fabry–Perot laser is around 1 mm, while a microdisk laser can be up to 1,000 times smaller. In this study, the laser size was reduced to a diameter of 30 to 40 microns.
Effective directional radiation output is essential for the successful implementation of optical communication in photonic integrated circuits (PICs). Directional radiation can be achieved by optically coupling microlasers with a nearby waveguide. The authors of the paper designed and fabricated both a microlaser and a waveguide from a single epitaxial structure, resulting in reduced size and increased stability.
'Creating microdisk lasers coupled to a waveguide is a challenging task. This process involves developing a thin-film epitaxial structure with a specific composition. In our case, we employed gas-phase epitaxy of metal-organic compounds, a method for layered formation of crystals of different substances on top of one another. Lasers and waveguides were created from the resulting structure. This was made possible thanks to the innovations developed by the Mokerov Institute of Ultra High Frequency Semiconductor Electronics of the Russian Academy of Sciences. All these processes required the use of advanced technology and the efforts of a team of experienced, talented, and qualified specialists,' according to Nikita Fominykh, Junior Research Fellow of the International Laboratory of Quantum Optoelectronics at HSE Campus in St Petersburg.
In addition to radiation sources, radiation receivers are also essential for the operation of PICs. In this work, waveguide photodetectors fulfil this role. Thus, it becomes possible to create an optocoupler that combines a microlaser and a waveguide photodetector with a matching operating wavelength on a single substrate. The photodetector used in the optocoupler measured no more than 90 microns, enabling the creation of a highly compact and energy-efficient optocoupler.
'Microdisk lasers are unique optoelectronic devices. With a size comparable to the diameter of a spider silk thread, they can generate a significant amount of optical power. We have experimentally demonstrated that all optoelectronic components necessary for a photonic integrated circuit—a microdisk laser, a waveguide, and a photodetector—can be fabricated from a single epitaxial heterostructure on the same substrate,' says co-author of the paper Natalia Kryzhanovskaya, Head of the International Laboratory of Quantum Optoelectronics at HSE Campus in St Petersburg.
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