Environmental sensing is a topic of increasing interest and has triggered much research towards fully integrated sensor solutions. In this context optical measurement approaches in the infrared can provide intrinsic selectivity and sensitivity for integrated gas sensors. Recently, we proposed the possibility of the incorporation of IR-active plasmonic materials to photonic crystal waveguides, which could allow to increase sensitivities and significantly reduce the size of such sensors. Here, we will first present the overall approach and compare two possible specific realizations.
Dipicolinic acid (DPA), bound to calcium (Ca), is a main component of bacterial endospores. Complexation of DPA with lanthanide ions, particularly Terbium (Tb), allows for rapid detection via monitoring the lanthanide luminescence, with applications spanning from cell imaging to contamination and biohazard detection, to sterilization control. Here we present time-resolved luminescence of the Tb-DPA complex upon UV excitation at 266 nm. Our measurements directly monitor the luminescence dynamics and speak for a rise of the luminescence on the ns time scale, which is orders of magnitude faster than previously reported, and raise questions about the details of the energy transfer process in this complex and the states involved. The results are relevant for the design of more sensitive detection schemes for Tb-DPA fluorescence, as well as for the design of novel Tb-based luminescence probes or novel fluorescence probes working as FRET acceptors of Tb energy.
We present a transient absorption setup based on a low-power laser system and a photonic crystal fiber for supercontinuum generation. The setup employs an ultrafast erbium-doped fiber laser system that emits at 775 nm with 80 MHz repetition rate which pumps a non-linear photonic crystal fiber that provides a supercontinuum in the NIR/VIS wavelength region for probing. By using an acousto optic modulator for pump-beam modulation and a lock-in amplifier we were able to achieve a detection-limit of 1 μOD. The setup reveals the potential of photonic crystal fibers as broadband sources in combination with low-power lasers.
Ultrafast fiber lasers represent an affordable source for performing non-linear spectroscopies, like transient absorption or coherent antistokes Raman scattering, and can advance these technologies towards commercial devices. We experimentally investigate the generation of white light in photonic crystal fibers at low pulse energies and high repetition rates using 775 nm pulses at 80 MHz from the second harmonic of an Er:fiber laser. Two different fibers were chosen based on non-linear beam-propagation simulations. The generated broadband light was characterized and compared in terms of spectral bandwidth, pulse duration and shot-to shot noise, showing good agreement with the simulations.
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