According to McCombs, an optical frequency comb (OFC) is a laser source whose spectrum consists of a series of discrete, uniformly spaced comb lines that can be used for precise measurements. Over the past two decades, they have become major tools in applications such as precision ranging, spectroscopy and communications.
Most based on mode-locked lasaer pointer (mode – lock lasers, namely through the different lasing frequency modulation has a certain phase relationship between the longitudinal mode, in order to obtain a narrow pulse width and peak power of ultrashort pulse laser) of commercial optical frequency comb drive source are bulky and expensive, these feature restricts their development potential of large capacity and portable applications. Although chip-level optical frequency combs using microresonators were first introduced in 2007, they were hampered by high material losses and complex excitation mechanisms.
Tobias J of the federal polytechnic institute of lausanne (EPFL). Kippenberg and Michael l. of the Russian Quantum Center. Gorodetsky’s team, which is co-led by Gorodetsky, has built an integrated soliton microcomb driven by an 88ghz repetition frequency using a chip-grade indium phosphide laser diode and a silicon nitride (Si3N4) microresonator. At just 1 cubic centimeter, the device is the smallest of its kind to date.
Silicon nitride (Si3N4) microresonators are manufactured using the patented photon Damascus reflow welding process, which achieves unprecedented low losses in integrated photonics. These ultra-low-loss waveguides bridge the gap between the chip-level laser diodes and the power levels needed to excite dissipated Kerr solitons, which are the basis of the optical frequency comb.
This method USES commercial chip-grade indium phosphide lasers instead of traditional large laser modules. In the study, due to the inherent scattering of the micro-resonator, a small amount of the laser will be reflected back to the laser. This direct reflection helps stabilize the laser and produce a soliton comb. This shows that the resonator and laser can be integrated on a single chip, which is a unique improvement over previous technologies.
Kippenberg explains: “there has been a lot of interest in the optical frequency comb driver, which is optically driven and can be fully integrated through optoelectronics to meet the needs of a new generation of applications, particularly for LiDAR and data center information processing. This not only represents a technological advance in the field of dissipated Kerr solitons, but also provides an opportunity to gain insight into the nonlinear dynamics of the cavity with rapid feedback.
The whole system is less than 1 cubic centimeter in volume and can be controlled electrically. Arslan Sajid, PhD student and lead author of the study, explains: “the microcomb system features compact structure, easy adjustment, low cost and low repeatability, making it suitable for large-scale manufacturing applications. Its main advantage is fast optical feedback without the need for active electronics or any other on-chip tuning mechanism.”
Scientists now aim to implement integrated spectrometers and multi-wavelength light sources, and further improve the manufacturing process and integration methods of microcombs that work at microwave repetition rates.