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In the framework of the design of a High Spectral Resolution Lidar (HSRL), a prototype receiver telescope based on a massive parabolic mirror is presented in this work. We also describe performance tests of three available etalons in resolving the He-Ne laser modes are given. Moreover we present a novel, generic and non-invasive characterization method of the etalons to be used for the proposed HSRL. This feature allows highest accuracy in distinguishing the aerosol and molecular backscattered signals.

In the framework of the design of a High Spectral Resolution Lidar (HSRL) for the atmospheric monitoring in High Energy Cosmic Ray Observatories, we demonstrate an accurate and noninvasive method for determination of the effective mirror spacing of the Fabry-Perot of one of the etalons being used for the receiver and having a nominal value of 5 mm. We used as a reference three very well known spectral lines of natural isotope mixture of Hg I at 435 and 546 and 579 nm. Furthermore, we present the investigation of the robustness of the obtained solution for the effective mirror spacing, by means of conclusions concerning the validity of the experimentally measured “excess fractions”. Because as the light source of the HSRL prototype we intent to use an SLM Nd:YVO4 laser it is very crucial to study and verify its spectral stability. This could be done using three Fabry–Perot etalons with precisely known mirror spacing.

We consider the design of a combined Fluorescence/Air-Cherenkov telescope prototype with capability to detect, in separate channels, the fluorescence and air-Cherenkov contributions. This radiation comes from air shower caused by an escaping tau from a nearby mountain, after being produced in a cosmic tau-neutrino mountain mass interaction. The location of the telescope, near the 2.3 meter diameter “Aristarchos”, is considered one of the darkest in Europe. In this work, we focus our design on the optical filter technology for the telescope, exploiting recent developments in the manufacturing such as rugate type optical filters, which promise the tailoring their spectral transmittance to optimize the optical signal-to-noise ratio.