# Femtosecond pulse bursts raise photocurrent 57% in amorphous gallium oxide UV photodetector

- Published: 2026-11-07 16:23 UTC
- Section: Machines & Making › Materials science
- Tags: digital cold strain engineering, amorphous gallium oxide, femtosecond pulse sequences, ultraviolet photodetector, photocurrent, responsivity, detectivity, East China Normal University, Advanced Photonics
- URL: https://realtech.media/news/rt-1a3e79a0242fada8d3fe486c_femtosecond_pulse_bursts/

**East China Normal University team tuned amorphous gallium oxide films with programmed femtosecond sub-pulses; a test UV photodetector gained responsivity but became slower.**

![Femtosecond pulse bursts raise photocurrent 57% in amorphous gallium oxide UV photodetector](https://realtech.media/media/2026/11/c4e3fd65c880cdd7.jpg)
*Onlywww, Wikimedia Commons, CC BY 4.0*

Researchers led by Heping Zeng at East China Normal University reported a laser method for modifying thin films of amorphous gallium oxide, according to a paper in Advanced Photonics. The approach, called digital cold strain engineering (DCSE), uses GHz-frequency femtosecond pulse sequences to produce stress-mediated changes in the film. The team tested it on a representative ultraviolet photodetector. [1]

Strain engineering in amorphous oxides is impeded by crystallization and mechanical damage, which limits device performance. An amorphous material has no repeating atomic arrangement over long distances, so heating or deformation can damage it or trigger crystallization. DCSE is meant to modify the amorphous network while keeping it predominantly amorphous. [1]

## How the pulse sequence works

At constant laser power, the authors program the number of sub-pulses. This produces a controllable ultrafast stress field and suppresses pronounced ablation craters on the film. [1] At the same average power, more sub-pulses mean less energy in each individual interaction, while the pressure responses of closely spaced pulses can overlap before relaxing. The term "cold" does not mean there is no heating: energy is deposited faster than it spreads, so thermal and mechanical processes still have to be considered together.

Multimodal characterization showed the amorphous phase preserved within the detection limit. Surface roughness and film thickness decreased, and the refractive index increased. [1] The Ga 3d and O 1s binding energies shifted. The authors suggest that modification of the amorphous network and changes in the local electronic environment may contribute to the blue shift of the optical absorption peak from 263 to 256 nm. [1]

## Photodetector results

The representative photodetector showed about 57% higher photocurrent and about 58% higher responsivity (about 0.126 versus about 0.080 mA/W). Detectivity improved by about 25%, from about 4.4×10^9 to about 5.5×10^9 Jones. [1]

There were tradeoffs. According to the summary of the work, dark current increased moderately and the device responded more slowly, so the gain does not apply to every parameter, especially where fast detection and recovery are needed. The precise mechanisms, long-term stability and suitability for larger-scale manufacturing remain under investigation.

The authors present DCSE as a strategy for programmable structural and electronic modification of amorphous materials through discrete laser pulse programming. [1]

## Sources

1. [Advanced Photonics](https://doi.org/10.1117/1.ap.8.5.056015)
2. [knowridge.com](https://knowridge.com/2026/11/programmed-laser-bursts-could-tune-materials-for-more-sensitive-ultraviolet-sensors)

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Source: RealTech, realtech.media — https://realtech.media/news/rt-1a3e79a0242fada8d3fe486c_femtosecond_pulse_bursts/