1：Experimental Design and Method Selection:

Direct laser writing was performed using a Nd:YAG laser providing 10 ns laser pulses at 1064 nm and at 532 nm. The laser beam was focused by a microscope objective on the samples. A nanopositioning stage was used to place the sample at the focal plane of the lens and precisely move it with respect to the laser beam. In situ inspection of the sample surface during the direct laser writing was provided by a light emitting diode, a CCD camera, and appropriate lenses.

2：Sample Selection and Data Sources:

AMTIR-1 (Ge33As12Se55) thin film layers were used for direct laser writing. The Sb2Te3 material was chosen for studying the beam size reduction.

3：List of Experimental Equipment and Materials:

Nd:YAG laser, microscope objective, nanopositioning stage, light emitting diode, CCD camera, appropriate lenses, AMTIR-1 thin film layers, Sb2Te3 material.

4：Experimental Procedures and Operational Workflow:

The laser beam size at the focal plane was measured by local ablation of the Sb2Te3 material using different laser energies and performing Scanning Electron Microscopy studies. Direct laser writing was then performed on AMTIR-1 thin film layers, and atomic force microscopy (AFM) measurements were performed at the irradiated zones to determine the thickness of the irradiated lines.

5：Data Analysis Methods:

The beam waist of the laser beam was found by fitting the findings obtained from several irradiated sites. A modified Beer-Lambert model was employed to estimate the resolution enhancement provided by the nonlinearity of the Sb2Te3 material.