Tiny Gold Sensors That Beat Light Into Heat Signals

Ultrathin Gold Films Become Tiny Light Sensors

A recent study demonstrates that gold films only a few nanometers thick can be transformed into miniature mechanical sensors. These devices vibrate at exceptionally high frequencies—on the order of millions of cycles per second. When illuminated by a laser, their vibration frequency shifts in a predictable manner, allowing the sensor to act as a miniature thermometer for light energy.

• Responsivity
  The team measured the change in vibration frequency per unit of absorbed power, finding a responsivity of approximately 11 parts‑per‑million per microwatt—remarkably high for such diminutive structures.

• Power Range & Stability
  Performance remained stable across a wide laser power spectrum, from just a few microwatts up to nearly 0.5 mW.

• Linearity
  The sensor’s behavior is highly linear, with a non‑linearity factor of only 0.0865, enabling reliable conversion of light power into frequency changes without complex calibration.

• Material Properties
  By analyzing how vibration frequency scales with size, the researchers extracted key material parameters:
• Young’s modulus: ~75.6 GPa, close to bulk gold values.
• Pretension in membranes: ranging from 0.09 N/m to 0.8 N/m.

These findings open the possibility of fabricating large arrays of such sensors on a single chip. Their thinness and mechanical simplicity make them ideal for integration into photonic circuits or for monitoring light intensity in compact devices. The work underscores how adding mechanical motion to ultrathin metal films introduces a powerful new dimension to sensing capabilities.