This study proposed a filter-free wavelength sensor with a double-well structure for detecting fluorescence without an optical filter. The impurity concentration was optimized and simulated to form a double-well-structured sensor, of which the result was consistent with the fabricated sensor. Furthermore, we proposed a novel wavelength detection method using the current ratio based on the silicon absorption coefficient. The results showed that the proposed method successfully detected single wavelengths in the 460–800 nm range. Additionally, we confirmed that quantification was possible using the current ratio of the sensor for a relatively wide band wavelength, such as fluorescence. Finally, the fluorescence that was emitted from the reagents ALEXA488, 594, and 680 was successfully identified and quantified. The proposed sensor can detect wavelengths without optical filters, which can be used in various applications in the biofield, such as POCT as a miniaturized wavelength detection sensor.

This study describes the bacterial sensing system using a photogate type fluorescence sensor for the purpose of identifying Legionella bacteria, which are known to emit different fluorescence for each bacterial species when irradiated with ultraviolet excitation light. First the weak photocurrent current measurement system in the combination with the photogate type optical sensor and a printed circuit bord which is mounted with a current-voltage converter, analog to digital converter, and a microcomputer was fabricated. Then the weak light measurement was performed by simulating the bacterial fluorescence of Legionella. The difference in the current ratio generated in the sensor was found depending on the wavelength for the light source of LED, shoeing that the system work as a spectrometer. Finally, the system was applied to measure the fluorescence of the species of Legionella dumoffii and Legionella erythra and identified each species of Legionella just by obtaining the current ratio.