A new on-chip laser frequency comb was born! The efficiency has been improved 10

On chip laser frequency comb is a promising technology in the fields of environmental monitoring, optical computing, astronomy and metrology. However, due to the inability to design an on-chip laser frequency comb that is both efficient and has significantly improved bandwidth, this problem has puzzled researchers for many years, and also hindered the widespread commercialization of these devices.

Recently, a team from the John Paulson School of Engineering and Applied Sciences (SEAS) of Harvard University developed an electro-optical frequency comb, which combines a coupled resonator with an electro-optical frequency comb to improve the efficiency and bandwidth of the frequency comb.

The results show that it not only improves the efficiency by 100 times, but also has more than twice the bandwidth of the previous version. In the future, this electro-optic frequency comb is expected to support a series of potential applications such as optical communication, astronomy, optical computing, ranging and optical metrology.

Image source: Harvard SEAS

The above research integrates the concepts of high efficiency and broadband to solve the efficiency bandwidth tradeoff problem currently existing in the resonator based electro-optical frequency comb. The research results were published in the journal Nature Photonics.

It is reported that as early as 2019, the team announced and demonstrated what is said to be the world's first stable chip frequency comb that can be controlled by microwave. This electro-optical frequency comb is built on the lithium niobate platform, which spans the entire telecommunication bandwidth, but has limited efficiency. By 2021, the team will have developed a coupling resonator device for controlling optical flow. Researchers will use this device to demonstrate the frequency shifter on the chip, which can change the color of light with an efficiency of nearly 100%.

Recently, the SEAS team obtained the results in the on-chip frequency comb experiment based on the thin-film lithium niobate coupled resonator platform, which showed that the conversion efficiency of the on-chip laser frequency comb reached 30%, and the optical span was 132 nm, which successfully improved the efficiency without sacrificing the bandwidth.

The researchers also showed that the electro-optic frequency comb can be used as an integrated femtosecond pulse source. The ability to generate femtosecond pulses on a chip is very important for nonlinear photonics, optical atomic clocks, optical sensing and optical computing with time bin coding. It is reported that in the case of ultra fast and high power, the team demonstrated a frequency comb with electro-optic and third-order nonlinear effects.

Mengjie Yu, a postdoctoral fellow of SEAS, said: "We found that when you improve the performance of the comb source to this level, the device starts to operate in a new state, which combines the electro-optical frequency comb generation process with the more traditional Kerr frequency comb method."

On chip frequency combs with high efficiency and wide span are of great significance for a series of optical applications. For example, a hundredfold increase in comb efficiency can increase the signal-to-noise ratio of frequency multiplexing applications (such as optical communications) by 20 decibels. The advanced on-chip frequency comb can also reduce the optical pump power required to operate the optical neural network. In addition, the integration of an on-chip microwave resonator with an efficient, broadband, on-chip electro-optical frequency comb source can reduce microwave power consumption. The high conversion efficiency of the on-chip frequency comb is expected to bring a new generation of wide-band electro optical comb with entangled photons, which can widely implement quantum information processing in the frequency domain.

Source: OFweek