Volume Fresnel zone plates fabricated by femtosecond laser direct writing

Abstract

In this letter, volume Fresnel zone plates fabricated inside fused silica using femtosecond laser direct writing are demonstrated. A volume zone plate consists of a number of layers of Fresnel zone plates designed to focus light together. Results indicate that volume Fresnel zone plates increase the overall diffraction efficiency significantly. Phase zone plates yield considerably higher diffraction efficiency due to a number of reasons including negligible light absorption, robustness against fabrication phase errors, and minimum interference between different zone plates in a volume.

Beam propagation modeling of modified volume Fresnel zone plates fabricated by femtosecond laser direct writing

“…The volume Fresnel zone plate (VFZP) is a focusing device consisting of a number of Fresnel zone plate (FZP) layers inside a transparent medium [1,2]. The FZPs are aligned on the same optical axis and designed to focus light to a single spot as shown in Fig.…”

“…The experimental study of VFZP shows that the efficiency of the VFZP continues to increase up to a certain number of FZP layers before it starts to drop [1,2]. Consequently, it is difficult to predict the diffraction efficiency of the VFZP, since light propagation by diffraction through 3D VFZP structures is complicated.…”

[INVITED] Ultrafast laser micro-processing of transparent material

“…Four-level diffractive lenses were shown to provide a maximum efficiency of 56.9% [50]. Srisungsitthisunti et al demonstrated a volume Fresnel zone plate, which consists of a number of layers of Fresnel zone plates designed to focus light together inside fused silica [51].…”

Effective removal of adhering cells via ultrashort laser pulses

“…The substantial plasma absorption enables the ablation of materials that are normally difficult to ablate by conventional lasers, such as transparent or low absorption materials [1,2]; and the ablation does not depend on the laser wavelength and material absorption property. Extensive studies utilizing USP laser ablation in basic science and industrial applications have been carried out [3,4]. In recent years, USP lasers have attracted increasing attention in biomedicine, including imaging of early cancers [5,6], human chromosomes dissection [7], and ablation of soft and hard tissues [8][9][10].…”