Processing of materials by ultrashort laser pulses has evolved significantly over the last decade and is starting to reveal its scientific, technological and industrial potential. In ultrafast laser manufacturing, optical energy of tightly focused femtosecond or picosecond laser pulses can be delivered to precisely defined positions in the bulk of materials via two-/multi-photon excitation on a timescale much faster than thermal energy exchange between photoexcited electrons and lattice ions. Control of photo-ionization and thermal processes with the highest precision, inducing local photomodification in sub-100-nm-sized regions has been achieved. State-of-the-art ultrashort laser processing techniques exploit high 0.1–1 μm spatial resolution and almost unrestricted three-dimensional structuring capability. Adjustable pulse duration, spatiotemporal chirp, phase front tilt and polarization allow control of photomodification via uniquely wide parameter space. Mature opto-electrical/mechanical technologies have enabled laser processing speeds approaching meters-per-second, leading to a fast lab-to-fab transfer. The key aspects and latest achievements are reviewed with an emphasis on the fundamental relation between spatial resolution and total fabrication throughput. Emerging biomedical applications implementing micrometer feature precision over centimeter-scale scaffolds and photonic wire bonding in telecommunications are highlighted.

We propose a holographic femtosecond laser processing system capable of parallel, arbitrary, and variable patterning. These features are achieved by introducing a spatial light modulator displaying a hologram into the femtosecond laser processing system. We demonstrate the variable parallel processing of a glass sample.

Holographic femtosecond laser processing with multiplexed phase Fresnel lenses for high-speed parallel fabrication of microstructures is proposed. Use of a spatial light modulator (SLM) allows independent tunability of the diffraction peaks, three-dimensional parallelism, and arbitrary, variable features. The diffraction peaks are made uniform by changing the center phase and size of each phase Fresnel lens while taking account of the intensity distribution of the irradiated laser pulse and the spatial frequency response of the SLM.

Digital holography (DH) is a promising technique for modern three-dimensional (3D) imaging. Coherent holography records the complex amplitude of a 3D object holographically, giving speckle noise upon reconstruction and presenting a serious drawback inherent in coherent optical systems. On the other hand, incoherent holography records the intensity distribution of the object, allowing a higher signal-to-noise ratio as compared to its coherent counterpart. Currently there are two incoherent digital holographic techniques: optical scanning holography (OSH) and Fresnel incoherent correlation holography (FINCH). In this review, we first explain the principles of OSH and FINCH. We then compare, to some extent, the differences between OSH and FINCH. Finally, some of the recent applications of the two incoherent holographic techniques are reviewed.

We use an interferometric time-resolved observation of a femtosecond-laser pulse (800 nm/45 fs) interaction with glass from 100 fs to 10 ns at spatial lateral resolution down to the wavelength of the pulse. The phase and amplitude images reveal sequence of events after the irradiation of a single ultra-short laser pulse at close-to-threshold intensity when permanent refractive index changes occur. The proposed method is applicable to characterization of the processes induced by tightly focused fs-laser pulses during three-dimensional structuring of glasses and crystals for fundamental studies and optical applications. Generation of carriers, thermal expansion, generation and propagation of shockwaves, and formation of refractive index changes are experimentally observed and resolved in time and space with the highest resolution. Quantitative estimations of the threshold energies of different processes are achieved. The threshold energy of carrier generation is found the same as that of shockwave generation while the threshold energy of refractive index changes was by 40% higher. Application potential of the method is discussed.