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A confocal optical microscope is a powerful tool for the high-resolution optical characterization of materials. Its core function is to provide detailed imaging and spectroscopic analysis at the micro- and nanoscale, enabling the study of morphology, defects, and optical responses with enhanced contrast and depth selectivity. Its fundamental principle is based on the use of a focused laser beam and a spatial pinhole placed in front of the detector to eliminate out-of-focus light. By scanning the sample point by point and reconstructing the image, the confocal configuration achieves superior axial resolution compared to conventional optical microscopy. This allows not only precise imaging of surface and subsurface features, but also the integration of complementary techniques such as photoluminescence or Raman spectroscopy mapping when coupled with appropriate detectors. The confocal microscopy is important for materials research because it bridges structural and optical information at the microscale. It enables the correlation of morphology with luminescence, defect distribution, and crystallographic orientation, providing insights into growth mechanisms and functional properties. In the context of semiconducting oxides and wide bandgap materials, it is particularly valuable for studying optical resonances, waveguiding effects, and defect-related emissions, which are key to advancing applications in optoelectronics, sensing, and photonic devices.
Key Capabilities
Key Capabilities
The FINE group is equipped with a Horiba Jobin-Yvon LabRam HR800 spectrometer coupled to an Olympus BXFM-ILHS confocal microscope. This system is optimized for the optical characterization of semiconducting oxides and other functional materials, offering high versatility in both excitation sources and detection modes. In addition, the setup is integrated with an INSTEC mK2000B cryostat, enabling temperature-dependent measurements over a wide range of experimental conditions.
Excitation Sources: The setup includes a He-Cd laser (λ = 325 nm), a He-Ne laser (λ = 633 nm), and a tunable EKSPLA NT200 OPO laser covering the 210–710 nm spectral range, enabling a wide variety of excitation conditions for different materials and optical transitions.
Operating Modes: The system supports both micro-photoluminescence (μ-PL) and micro-Raman (μ-Raman) measurements. In μ-PL, experiments can be performed in either aligned mode (excitation and detection at the same point) or misaligned mode (excitation and detection at different points), which is particularly useful for studying luminescence in nanostructures acting as optical waveguides.
Diffraction Gratings:
For μ-PL in the visible range, where a broad spectral window is required, a grating with a lower line density (≈600 lines/mm) is employed.
For μ-Raman, where high spectral resolution is essential, a grating with a higher line density (≈2400 lines/mm) is used.
Polarization Control: A polarizer can be placed before the spectrometer, allowing detection of vertically, horizontally, or arbitrarily polarized emission.
Excitation Power Tuning: Neutral density optical filters are available to finely adjust the laser power delivered to the sample, ensuring optimal conditions for both delicate and robust measurements.
Related Publications
Related Publications
In the published work of M. Alonso-Orts et al (2021), excitation and detection at different points along Ga₂O₃:Cr nanowires enabled the study of guided light and cavity resonances, while the use of a polarizer revealed polarization-dependent features. Furthermore, by varying the laser power with neutral density filters, controlled local heating was induced, producing spectral shifts of Fabry–Perot resonances. Together, these effects demonstrated the development of a wide dynamic range interferometric thermometer with a temperature resolution of about 1 K.
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