Fluorescence detection is a non-contact and non-destructive probing technique, which has achieved great attention due to its effectiveness and specificity[1–3]. Compared with traditional laser sources, light emitting diodes (LEDs) provide a cheaper light source and are easy-to-use in fluorescence detection systems[4–6]. Optical systems for the detection of fluorescent signals or fluorescence imaging are typically composed of a light source for emitting light at the dye absorption band, a filter for removing the unwanted excitation light at the receiving end, and a detector or CCD camera for receiving the fluorescence signal. Commonly, the optical systems are bulky and complicated due to a series of discrete free-space optical elements. Driven by the concept of “lab-on-chip” (LOC), many efforts have been paid to enhance the system integration[7–11]. For example, Novak et al. reported a miniaturized fluorescence detection system () by implementing LOC devices in a metal housing and achieved it. Xue et al. presented a miniaturized fluorescence detection device by mounting an LED and a minor filter into a polydimethylsiloxane (PDMS)-based microchip. This device can be further integrated into a smaller size of by integrating all necessary optical components into a metal package. Although the above work has realized the miniaturization of the detection system in the physical dimension, the components of each part are still discretely packaged, and the optical path is still divided into two paths: excitation and detection. If one can realize the coaxial transmission optical path, then the traditional system layout would be significantly simplified, leading to more miniaturized fluorescence detection or imaging devices.
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