A team of physicists at Stanford University recently announced that they have developed a new optical amplifier that is only about the size of a fingertip. It can increase the intensity of optical signals by about 100 times while consuming only a few hundred milliwatts of power, while maintaining low noise and full-bandwidth performance, opening up new possibilities for future integrated photonic chips and battery-powered devices. Relevant results were published in the journal Nature.
Optical amplifiers function like power amplifiers in audio systems and are used to enhance the intensity of optical signals. They are a key link in various optical-based technologies such as optical fiber communications and satellite communications. Currently common compact optical amplifiers generally have high power consumption, high noise, and have limitations in being integrated into chips. The plan proposed by the Stanford team focuses on greatly improving efficiency through "energy recovery" design and reducing energy consumption without sacrificing bandwidth and noise performance.
Amir Safavi-Naeini, corresponding author of the paper and associate professor of physics in the School of Humanities and Sciences at Stanford University, said that this is the first time to achieve a new type of optical amplifier that is truly versatile and low-power. It can cover a wide range of bands in the optical spectrum and is efficient enough to be integrated on a chip, thus providing a basis for building more complex optical systems.
According to the research team, the amplifier can amplify the input optical signal intensity by about 100 times while maintaining a compact chip-level size. It only requires hundreds of milliwatts of power, significantly reducing energy consumption compared with similar devices. Due to its small size and low power consumption, the device is expected to be directly powered by batteries and embedded in portable terminals such as laptops and smartphones. During the signal amplification process, the new device can also effectively suppress additional noise and provide a wider operating bandwidth than existing compact amplifiers, supporting a wider range of optical frequencies, increasing data capacity and reducing interference.
The core of this amplifier lies in the energy recovery and utilization of "pump light". In the traditional design, the pump light only serves as the driving medium, and its energy utilization efficiency is limited. However, the Stanford team uses a resonant structure to circulate the pump light inside the system and continuously enhance it, thereby obtaining higher field strength with lower input power. Devin Dean, co-first author of the paper and a doctoral student in the Safavi-Naeini research group, pointed out that by recycling pump energy, the team achieved an improvement in amplifier efficiency without sacrificing other key performance indicators.
Specifically, the researchers used a structure similar to a laser resonant cavity in the device to "reflect light back to itself", causing it to repeatedly travel back and forth in the cavity and gradually accumulate intensity. In this design, the pump light circulates in a ring resonator shaped like a "racetrack" and continuously increases along the closed loop to provide more efficient gain for the target signal. This "optical racetrack" structure allows the system to achieve higher pump intensity at lower input energy, significantly improving overall energy efficiency.
Thanks to reduced power consumption and chip-level shrinkage, this amplifier is expected to be implemented in a variety of application scenarios, including high-speed data communications, biosensing, and the development of new light sources. Dean said that once such a device can be mass-produced and driven by batteries, its application space will be very broad because it is small enough and can be deployed in batches in various terminal devices.
The research paper is titled "Low-power integrated optical amplification through second-harmonic resonance" and the authors are from Stanford University and partner institutions. The research work has been funded by the U.S. Defense Advanced Research Projects Agency (DARPA), Japan's NTT Research, and the U.S. National Science Foundation.
Compiled from /ScitechDaily