Real-Time Measurement of Photodissociation with a Static Modulated Fourier Transform Spectrometer

Abstract

A static modulated Fourier transform spectrometer composed of a modified Sagnac interferometer was implemented for real-time remote sensing of the spectral property changes in a solid dye. In the spectrum obtained from the implemented spectrometer, the relationship between spectral resolution and dependent factors was discussed to prevent aliasing. As a target material, a solid-state dye of rhodamine-6G was fabricated in the laboratory. When an intense pumping laser light was irradiated to a solid dye, with increasing irradiating time, photodissociation occurred due to the accumulated heat and the fluorescence intensity decreased rapidly. The fast change in the fluorescence spectrum of the solid dye due to photodissociation could be measured and analyzed in real time using a static modulated Fourier transform spectrometer implemented in the laboratory. As the pumping light source, a diode laser of 1 W output power at 530 nm, in which pulse width modulation was possible, was used. When the solid-state dye sample was irradiated with a 10 Hz pulse repetition rate and 2.5 ms pulse duration for 900 s, the fluorescence intensity decreased by 44%, the fluorescence peak wavelength shifted from 590 to 586 nm, and the maximum temperature of the irradiated portion rose up to 45 °C. Under the same conditions, when the pulse duration was increased by 4 times to 10 ms, the fluorescence intensity decreased by 65%, the fluorescence peak wavelength shifted from 590 to 580 nm, and the maximum temperature of the irradiated portion rose up to 76 °C. The spectrometer proposed in this study was effective in measuring and analyzing the spectral properties of rapidly changing materials in real time.

Keywords

• Fourier transform spectrometer
• Sagnac interferometer
• rhodamine-6G
• solid-state dye
• photodissociation
• static modulation