Ultrafast Optics

Prof. Nolte is Professor of Experimental Physics/Laser Physics at Friedrich Schiller University Jena and heads the Ultrafast Optics group at the Institute of Applied Physics. He is also Deputy Director and member of the Scientific Directorate of the Fraunhofer Institute for Applied Optics and Precision Engineering IOF.

His research focuses on the interaction of ultrashort laser pulses with matter and its use for high-precision material processing, three-dimensional structuring of transparent materials, photonic component fabrication, and medical applications.

Research Areas

The research of Prof. Nolte focuses on ultrashort laser pulses and their interaction with materials, from fundamental excitation and relaxation processes to industrial and biomedical applications. Research topics include:

• Linear and nonlinear laser–matter interaction
• Micro- and nanostructuring with ultrashort laser pulses
• 3D volume structuring of glasses, crystals and semiconductors
• Ultrashort-pulse laser cutting and welding
• Fiber and volume Bragg gratings
• Integrated and discrete photonic structures
• Additive manufacturing with ultrashort laser pulses
• Ultrafast laser applications in ophthalmology

Teaching Fields

Stefan Nolte is teaching courses ranging from fundamental aspects of physics to state-of-the-art research. He is also responsible for the ASP optics training laboratory, including labwork internships. He gives courses in Atomic and Molecular Physics and Ultrafast Optics.

Research Methods

Our laboratories are equipped with a wide variety of lasers, handling equipment and characterization technology. They include:

• High repetition rate ultrashort pulse laser systems (7 fs to 20 ps) including wavelength conversion (300 nm to 10 µm), and average powers up to 500 W
• High-precision positioning and laser scanner systems
• Equipment for sample preparation and characterization (optical microscopes, electron microscope, Raman microscope, etc.)
• Characterization of spectral and spatial properties of micro- and nanostructured samples
• Characterization of nonlinear spatio-temporal dynamics

Recent Research Results

Current research explores how ultrashort laser pulses can be used to precisely modify materials both at surfaces and deep inside transparent or semiconducting solids. A major focus is three-dimensional in-volume structuring. Recent work showed that picosecond double pulses can enable reproducible internal modification of silicon despite the strong nonlinear propagation effects that usually limit subsurface processing. By controlling pulse delay, polarization and energy balance, the deposited energy and modification size can be tailored with high precision [1].

The group also continues to advance ultrafast-laser-written photonic components. Recent work demonstrated additional control over the spectral response of fiber Bragg gratings by spatially shaping the inscription beam, enabling short gratings, apodization and suppression of spectral side lobes [2]. Related developments address chirped volume Bragg gratings written directly into fused silica for high-energy ultrashort-pulse laser systems [3].

Another major research direction is ultrashort-pulse laser welding. Localized nonlinear absorption enables robust joining of transparent materials with minimal heat-affected zones, and recent work has extended this approach towards direct glass-to-metal welding [4]. In parallel, ultrashort-pulse laser powder bed fusion is used to process challenging materials and alloys that are difficult to access with conventional additive-manufacturing techniques [5].

Medical applications remain an important part of the research portfolio, particularly femtosecond-laser approaches for ophthalmology and the controlled modification of the human crystalline lens.

[1] Blothe et al., Opt. Lett. 50, 6650 (2025).
[2] Krämer et al., Opt. Express 33, 28152 (2025).
[3] Perevezentsev et al., Opt. Express 31, 14286 (2023).
[4] Richter et al., Opt. Laser Technol. (2025).
[5] Lippmann et al., Addit. Manuf. (2025).

Link to the Ultrafast Optics Group