Transmittance/Absorbance

Absorption spectroscopy is a popular analytical tool to determine the presence of a particular chemical or biological substance in a sample, and often to quantify the amount of the substance present. Infrared and ultraviolet-visible spectroscopies are particularly common in analyses. Absorption spectroscopy is also employed in molecular and atomic physics, astronomical spectroscopy and remote sensing. In this setup, a tungsten light source is coupled to a sample compartment. The light passes through the sample and the remaining light is collected through a MicroHR and may be directed to either a CCD or silicon single point detector.

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Internal/External Quantum Efficiency

Internal Quantum Efficiency (IQE) and External Quantum Efficiency (EQE) measurements are indicators of the effectiveness of a photosensitive device such as those used in telecommunications and solar cells. EQE is the ratio of the charges generated to the total amount of photons incident on the surface; a larger EQE indicates a more efficient device. IQE is the ratio of the charges generated to the number of photons that hit the surface and are absorbed by the cell. Both EQE and IQE measurements are vital in the interrogation of light-responsive devices. In this setup, a tungsten light source is coupled to an iHR550 spectrometer to produce tunable light with narrow bandpass. The light is passed through a chopper and impinges on the device under test. The signal is analyzed using a lock-in amplifier synchronized with the chopper.

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Laser Induced Fluorescence

Laser induced fluorescence spectroscopy can be used to probe the complex molecular dynamics in a variety of systems. One example of such a dynamic process is intramolecular vibrational redistribution (IVR), wherein one vibrational mode is excited, and the energy is dispersed into other modes in the molecule. By using low pressure gas cells, the IVR processes can be isolated from effects from the surrounding environment, such as solvent interactions. In this setup, a high resolution 1000M spectrometer is used to conduct a dispersed fluorescence measurement. A liquid nitrogen cooled Symphony II CCD is used to detect the resulting signal.

Biological Fluorescence and Diffuse Reflectance

Optical spectroscopy can be used to differentiate between healthy tissue and benign tissue. This is particularly important for intra-operative diagnostics to locate small regions of cancer within normal tissue. Specifically, diffuse reflectance spectroscopy has been used to characterize both benign and malignant breast tissue ex situ. In this setup, a light source and dual grating monochromator produce tunable light which is coupled to a fiber bundle and introduced to the tissue under study. Another set of fibers then collect the signal and couple it to a spectrograph and detector for analysis.

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