The Advanced Optical Spectroscopy & Microscopy Facility combines a broad range of optical instruments suitable for studies of optical properties of hard, soft or biological materials using ultrafast and nonlinear spectroscopy, and single-molecule optical and confocal methods.
Contact: Matthew Sfeir
Our facility houses a state-of-the-art high power kilohertz femtosecond regenerative amplifier combined with an optical parametric amplifier that allows generation of sub 100 femtosecond pulses in the ultraviolet, visible, and infrared regions of the spectrum. This system is coupled to a series of user-friendly time-resolved and nonlinear optical techniques, providing Users with a broad suit of tools for characterizing the photophysical properties of their materials, including:
The CFN houses a broadband transient absorption spectrometer with approximately 100 fs time resolution in a time window of 0 - 3 ns. In this technique, the samples are optically "pumped" using a tunable (240 - 2600 nm) femtosecond laser pulse and "probed" for changes in transmission using a "white-light" laser generated supercontinuum. The system can be configured to record spectral transients in one of three operating modes: 350 - 700 nm, 450 - 820 nm, or 800 - 1600 nm. Sample holders for cuvettes and thin films are available.
In addition, the broadband transient absorption spectrometer can be configured to measure long-lived electronic and chemical species with sub-ns time resolution in a time window of 0 - 50 microseconds. In this configuration, spectral transients can be recorded in one of two operating modes: 370 - 900 nm or 800 - 1700 nm. Sample holders for cuvettes and thin films are available. This is an optically gated technique using a femtosecond excitation pulse and a longer (~ 500 ps) white-light laser probe pulse.
This spectrometer is able to measure ultrafast emission processes in the visible and NIR (400 - 1600 nm) with a time resolution of ~ 100 fs in a time window of 0 - 3 ns. In the upconversion method, the emitted photons are mixed with an optical gate pulse in a nonlinear crystal optimized for sum frequency generation. We detect the intensity of the higher energy upconverted photons as a function of time delay between the excitation pulse and the gate pulse to map out the kinetics. Alternatively, spectral emission transients can be recorded at a fixed delay time. For longer kinetic processes, the spectrometer can also be operated in time-correlated single photon counting mode (TCSPC) in which the emitted photons are directly detected. The use of fast electronics allows for a time resolution of 100 ps over a range of 0 – 1 ms.
We have implemented this technique for measuring multi-photon absorption coefficients and nonlinear refractive indices of novel photonic materials. In this experiment, a thin solid or liquid sample is translated through the focus of high pulse energy NIR light (700 – 1200 nm). The normalized transmission is detected as a function of position along the light focus and used to derive the nonlinear optical coefficients.
Contact: Mircea Cotlet