Ultrashort mid-infrared (mid-IR) laser pulses are essential for applications such as molecular spectroscopy, nonlinear microscopy, and biomedical imaging, but their generation often relies on complex and power-intensive systems that are difficult to implement outside of specialized laboratories. These systems usually require high pump powers, elaborate optical setups, and precise alignment, which can limit their widespread adoption and practical use in everyday research and clinical settings.
In a paper made available online on 28 November 2025 and published in Volume 62, Issue 1 of the IEEE Journal of Quantum Electronics on 01 February 2026, a team of researchers from SASTRA Deemed University, Thanjavur, report a compact, fiber-based method for generating clean ultrashort mid-IR pulses at significantly reduced input power. The study demonstrates that high-quality pulse compression can be achieved using a holmium-doped ZBLAN photonic crystal fiber integrated into a nonlinear optical loop mirror (NOLM), offering a simpler and more energy-efficient alternative to conventional systems.
A carefully engineered tapered fiber geometry enables self-similar pulse evolution, ensuring that the pulse maintains its shape as it propagates along the fiber. This is crucial for achieving efficient compression and preserving pulse fidelity during propagation. Holmium doping provides optical gain near 2.86 μm, which amplifies the signal and compensates for losses that can occur during propagation. Together, these features enable efficient pulse compression, suppress unwanted temporal pedestals that can reduce pulse quality, and prevent fiber damage even under high-intensity operation. The integration of these components within a single fiber-based architecture allows for a compact and robust system design that minimizes alignment complexity and enhances overall operational stability, making it more suitable for real-world deployment.
“By combining rare-earth enabled gain and nonlinear pulse shaping mechanism of nonlinear optical loop mirror configuration, we reduced the required input power from the kilowatt range to just 80 watts,” said G. Sornambigai, the lead author. This dramatic reduction in power not only improves energy efficiency but also reduces the thermal load on the fiber, lowering the risk of damage and extending the operational lifetime of the system significantly.
At the optimized fiber length, the system compressed 5-picosecond pulses to 187 femtoseconds, achieving a compression factor of 26.7 with pedestal energy as low as 0.63%. “This architecture delivers clean, high-contrast pulses that are well suited for mid-IR spectroscopy and nonlinear imaging,” added co-author R. Vasantha Jayakantha Raja.
Self-similar pulse modelling and system-level analysis played a key role in optimizing performance and ensuring reliable pulse compression. The researchers note that this is the first demonstration of a Ho:ZBLAN-based NOLM system producing sub-200 femtosecond pulses in the mid-infrared, marking an important milestone in the development of compact, low-power, and highly efficient ultrafast mid-IR sources.
By providing a robust, alignment-free, and energy-efficient route to ultrashort mid-IR pulse generation, this fiber-based approach has the potential to accelerate advances in spectroscopy, nonlinear imaging, and other emerging photonic applications, bringing ultrafast mid-infrared technologies closer to practical real-world deployment.
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Reference
Authors: G. Sornambigai 1 , A. Esther Lidiya 2 , and R. Vasantha Jayakantha Raja 3
DOI: 10.1109/JQE.2025.3638679
Affiliations: 1 School of Electrical and Electronics Engineering, Centre for Nonlinear Science and Engineering (CeNSE), SASTRA Deemed to be University, Thanjavur, Tamilnadu, India
2 Leibniz Institute of Photonic Technology, Albert Einstein Straße 9, Jena, Thuringia, Germany
3 School of Electrical and Electronics Engineering, Centre for Nonlinear Science and Engineering (CeNSE), SASTRA Deemed to be University, Thanjavur, Tamilnadu, India
About the SASTRA Deemed University
SASTRA Deemed University, located in Thanjavur, Tamil Nadu, India, is a leading private university known for its strengths in engineering, science, and interdisciplinary research. The university emphasizes innovation, industry collaboration, and high-impact research across emerging areas of science and technology, including photonics, materials, and advanced manufacturing.
Website: https://www.sastra.edu/
About G. Sornambigai, Research Scholar, SASTRA Deemed University
G. Sornambigai is a Ph.D. doctoral student in the Department of Physics at SASTRA Deemed University, Thanjavur, India. Her research focuses on nonlinear fiber optics and numerical modeling of ultrashort pulse dynamics in specialty fibers, with particular interest in mid-infrared pulse generation and fiber-based nonlinear photonic technologies.
Funding information
RVJR acknowledges SERB (CRG/2022/003162 dated 451 02 June 2023) and the DST-FIST program (Grant No. 452 SR/FST/PS1/2020/135) for providing financial support.
IEEE Journal of Quantum Electronics
Computational simulation/modeling
Not applicable
Pulse compression in Ho:ZBLAN photonic crystal fiber using a NOLM configuration for ultrashort Mid-IR generation
1-Feb-2026
The authors declare no competing interests.