High-power, ultrafast µ-PL spectrometer

• Subject Area: Condensed Matter Physics
• Term: Funded in 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 469987028

Ultrafast spectroscopy is an essential tool to understand the photophysics of luminescent materials and light emitting devices. The high-power, ultrafast µ-PL spectrometer described in this proposal plays a major role in the strategic plan of the Centre of NanoBioPhotonics to develop the next generation of biointegrated nano and microlasers for a wide range of biomedical applications. It will further critically enhance the research activities on fundamental properties of organic and biological polariton lasers. In addition, the instrument is ideally suited to guide the optimisation of highly fluorescent and phosphorescent materials, currently developed for ultra-bright organic light emitting diodes (OLEDs) and their application in optogenetics as well as for research on electrically driven organic lasers. The spectrometer will be able to excite nanolasers within live cells and determine their emission dynamics under single and multiphoton pumping. The high sensitivity of the temporal characteristics of nanolasers to geometric, physical and chemical changes will make this instrument a powerful tool for the development of novel sensing mechanisms based on biointegrated lasers. In addition, it will provide new insights into the photophysics and degradation mechanisms of nanolasers and other luminescent materials to guide their future optimisation.To be able to work on such a wide range of materials and devices, the time-resolved spectrometer comprises a streak-camera system that is designed to investigate temporal phenomena that stretch over 9 orders of magnitude in time, from 1 ps to 1 ms. To analyse processes on these timescales, the optical excitation of the sample must occur on an even faster, sub-picosecond time scale. In addition, to apply time-resolved spectroscopy deep within scattering biological tissue, multiphoton excitation will be required. Combining these properties while also providing enough pulse energy to excite biointegrated lasers above their lasing threshold requires a pump source that by far exceeds the power level of standard lasers used in non-linear microscopy. The proposed instrument is therefore based around a wavelength-tuneable (325 – 2500 nm) femtosecond laser system with exceptionally large pulse energy (>200 nJ/pulse), short pulses duration (<200 fs), MHz repetition rate, and group-velocity dispersion correction. Such high-power lasers (>80 W at the pump stage) have only recently become commercially available, allowing for the first time to optically pump a broad range of organic and inorganic semiconductor-based nanolasers with the ultra-short pulses required for efficient nonlinear excitation. Overall, the new instrument will be unique in its ability to study temporal phenomena of nano and biophotonic devices and will greatly improve the measurement capability.

• DFG Programme: Major Research Instrumentation
• Major Instrumentation: Ultraschnelles µ-PL Spektrometer mit hoher Pulsenergie
• Instrumentation Group: 5700 Festkörper-Laser
• Applicant Institution: Universität zu Köln
• Leader: Professor Dr. Malte Gather