The develop of Volume Phase Holographic Gratings (VPHGs) working as echelle grating is reported based on binary structures. A mask lithography process was developed to produce the patterns on SU8 photoresist. The binary pattern with 50 l/mm were regular and defect free. The samples were characterized by different duty cycles, which is a key parameter in defining the diffraction efficiency in such binary gratings. The efficiency has been measured at different wavelengths and for different orders. The results have been compared with those obtained by simulations.
The progress in the field of organic photodetectors has recently led to the development of very fast and efficient devices, but their spectral sensitivity is mainly limited to the visible, without covering the regions of the spectrum of greater interest for telecommunications. One of the major issues when dealing with long wavelength organic photodetectors is the usually poor environmental stability of low bandgap organic semiconductors. A possible exception to this scenario is represented by coordination complexes with organic ligands. We employ as photosensitive materials transition metal dithiolene and dioxolene complexes which combine high thermal and photochemical stabilities with high molar extinction coefficients in the near infrared. Taking advantage of the broad tuning of electronic absorption spectra which can be exerted by changing the oxidation state of the complexes, we develop planar metal-semiconductor-metal phostodetectors which are spectrally matched to the optical fiber windows and which can detect light pulses with repetition rates in the range of hundreds of kbit/s.
This investigation demonstrates the existence of organic materials of potential telecom interest and that the detection of infrared light pulses is feasible, thus representing a first step toward organic photodetectors for telecommunications.