Physicists Plan to Build World’s Most Stable Laser Inside a Lunar Crater
A block of silicon, housed in a permanently shadowed Moon crater, could become the heart of an ultrastable laser with applications spanning lunar GPS to gravitational wave detection.
The Core Concept
Physicist Jun Ye and colleagues have proposed building a critical component for an ultrastable laser—an optical silicon cavity—inside the permanently shadowed craters of the Moon’s south pole. The extreme cold, low vibrations, and high vacuum of these craters create near-ideal conditions for this device.
The Silicon Cavity
The proposed component is an optical silicon cavity: a block of silicon designed so that only specific frequencies of light can resonate between two precisely aligned mirrors. The Moon offers a unique combination of low seismic vibrations and an extraordinarily high vacuum. Permanently shadowed craters at the south pole have temperatures around 50 K and vacuum conditions even better than those achievable on Earth.
By radiating residual heat into the cold space surrounding the crater, the cavity could be cooled to 16 K—the temperature at which silicon's thermal expansion coefficient drops to zero. This eliminates frequency drift caused by thermal changes. A commercially available laser, locked to this cavity's resonant frequency, would produce a single, unchanging color of light with unprecedented stability.
Potential Applications
The resulting laser could serve multiple groundbreaking purposes:
- Lunar GPS: Acting as a master time signal, it could provide GPS-like navigation for spacecraft and rovers operating on the Moon.
- Gravitational Wave Detection: A network of multiple such lasers could precisely measure minute changes in distance, potentially detecting gravitational waves from space.
- Optical Atomic Clock: The laser could serve as the backbone for a highly precise optical atomic clock on the lunar surface.
Deployment Plan
The team has outlined a practical deployment strategy:
- The silicon cavity would be fully assembled on Earth, small enough to fit inside an Artemis spacecraft.
- Astronauts would use a lunar rover to carefully lower the cavity into a chosen crater.
- Co-author Yiqi Ni estimates a demonstration in low-Earth orbit within two years, followed by deployment on the lunar surface in three to five years. Installation inside a deep, dark crater would occur on a longer timescale.
Publication & Authors
The proposal was published on May 8, 2026, in the Proceedings of the National Academy of Sciences (DOI: 10.1073/pnas.2604438123). Authors include researchers from JILA, NIST, NASA JPL, PTB Germany, and Lunetronic Inc.