Spectrally resolved optical microscopy using a transmission grating spectrograph: importance of spatial selection

Area of Science:

• Optical Microscopy
• Spectroscopy
• Materials Science

Background:

• Transmission grating (TG) spectrographs are underutilized for spatially resolved absorption measurements of solid samples.
• The impact of spatial selection on spectral characteristics in such systems is not well understood.

Purpose of the Study:

• To develop an efficient method for sub-micrometer spatial resolution absorption spectroscopy.
• To investigate the influence of spatial selection on spectral features using a slit-TG-CCD setup.

Main Methods:

• Integration of an adjustable slit, transmission grating (TG), and CCD detector with an optical microscope.
• Implementation of spectrally resolved optical microscopy (SROM) for analyzing both fluorescent and non-fluorescent samples.
• Systematic evaluation of spectral changes at varying slit widths, approaching diffraction limits.

Main Results:

• Spatial selection exceeding ~1 μm leads to loss of spectral features, line broadening, and peak shifts.
• Near diffraction-limited slit-width is essential for accurate absorption profiles in TG-CCD based spectroscopy.
• High spatial selection enables identification of spectral signatures of individual components in heterogeneous samples.

Conclusions:

• The developed SROM method provides reliable, spatially resolved absorption spectra at sub-micrometer resolution.
• Precise spatial selection is critical for obtaining accurate spectral data, especially for complex samples.
• This technique has potential for mapping marker distribution and estimating relative concentrations in cellular environments.