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We report the realization and characterization of an optofluidic microlaser based on a Fabry-Perot resonator fabricated by exploiting two direct writing fabrication techniques: the femtosecond laser micromachining and the inkjet printing technology. In this way a standard Fabry-Perot cavity has been integrated into an optofluidic chip. When using rhodamine 6G dissolved in ethanol at concentration of 5∙10^-3 mol/l, laser emission was detected at a threshold energy density of 1.8 μJ/mm² at least one order of magnitude lower than state-of-the-art optofluidic lasers. Linewidth below ~0.6 nm was measured under these conditions with a quality factor Q~10³. These performances and robustness of the device makes it an excellent candidate for biosensing, security and environment monitoring applications.

We report a full roughness analysis carried out upon the internal walls of fs-fabricated micro-structures embedded in fused silica glass. In addition to the standard mapping methods based on RMS evaluation, we performed a spectral analysis to compare different types of surface morphology. In detail, introducing the correlation length Lc as a key parameter to describe the profile periodicity, we highlight that the bottom- top- and side-wall of a square micro-channel show a different surface order and differently affect the light scattering. This is further validated by fast Fourier transform calculations and supported by beam transmission holograms. Here we suggest that proper beam shaping could ensure uniform energy distribution and low scattering effects.