Visible light communication (VLC), with its significantly broader spectrum compared to radio frequency communication, has the potential to achieve higher data transmission rates, making it a promising candidate for 6G networks^[1–4]. The primary device used to receive optical signals at the VLC receiver end is the photodiode (PD). However, PDs typically have small receiving areas, which limit both the field of view (FOV) and the signal gain^[5,6]. To address this limitation, researchers have proposed lens-based optical antennas that capture and focus optical signals, concentrating light from a larger area onto a smaller receiving surface. While the antennas increase signal gain, their FOV is constrained by the limitation of extension conservation^[7–11]. To overcome this, fluorescent antennas (FAs) for VLC have been proposed, where luminescent particles within the antenna emit isotropic light upon excitation^[12,13]. This type of antenna effectively addresses the limitation of extension conservation of lens antennas, achieving both a wide FOV and high signal gain^[14,15]. While fluorescent antennas effectively mitigate the FOV limitations of traditional lens-based antennas, they remain inadequate for further enhancing signal gain. Patterned structures hold significant potential for photon control and have been widely used in applications such as enhancing light emission in light-emitting devices and improving light absorption in solar cells^[16–18]. However, their use in fluorescent antennas has been seldom reported.

In this Letter, we propose a patterned fluorescent antenna (PFA) to enhance optical signal transmission in fluorescent antennas by incorporating microstructures on the surface. These microstructures, fabricated using nanoimprinting technology, modulate the propagation of light, enabling a wide FOV while simultaneously enhancing signal gain. Experimental results show that the single-sided and double-sided PFAs achieve average signal gains of 4.34 and 6.19 dB, respectively, representing a notable improvement over conventional FAs. These enhancements make PFA a promising candidate for high-efficiency VLC receivers in large-FOV applications.

The schematic diagrams of the FA and PFA are shown in Fig. 1. Both structures consist of a quantum dot (QD) film attached to a reflective substrate. The QD film is composed of a high-refractive-index polymer that encapsulates fluorescent particles, forming an efficient optical waveguide that directs light toward the edges of the film. The fluorescent particles absorb shorter wavelength incident light and subsequently emit fluorescence with a longer wavelength. An avalanche photodiode (APD) is located at the edge of the fluorescent antenna to receive the optical signal. The structure of the conventional FA is shown in Fig. 1(a), where a large amount of fluorescence, which does not meet the total internal reflection condition, escapes from the QD film. In contrast, the PFA, shown in Fig. 1(b), features patterned microstructures on the film surface. Due to their periodic arrangement, these microstructures form a diffraction grating^[19]. When the incident light and the emitted fluorescence interact with this grating, part of the light is diffracted into higher-order modes. This diffraction alters the propagation direction of the optical signal, thereby improving its in-plane transport efficiency toward the edges of the film and enhancing the coupling of light into the photodetector. The incident light can also contact more QDs due to diffraction, thereby further improving the signal gain.

The fabrication process of the PFA is outlined as follows: oil-soluble CdSe/ZnS QDs with an emission wavelength of 630 nm are selected. Initially, a specified amount of QDs (Beijing Beida Jubang Science & Technology Co., Ltd.) is dissolved in hexane to obtain a dispersion. This dispersion is then thoroughly mixed with polydimethylsiloxane (PDMS, Dow Corning 184). Next, PDMS is combined with a curing agent in a 10:1 weight ratio, followed by vacuum degassing. The resulting QD-containing curable PDMS mixture is poured into a mold and heated at 90°C for 1 h to fully cure and form a QD film. Subsequently, the porous anodic aluminum oxide (AAO) template is ultrasonically cleaned with anhydrous ethanol, followed by plasma cleaning at 150 W for 300 s. A 2% treatment solution is prepared by dissolving 1H, 1H, 2H, 2H-Perfluorooctyltrimethoxysilane (Macklin, Shanghai, China) in anhydrous ethanol. The plasma-treated AAO template is immersed in the treatment solution for a specified duration and then dried on a hot plate at 90°C to complete the pretreatment. The purpose of the pretreatment is to reduce the surface energy of the AAO template, minimize the demolding force, and enhance the template’s lifespan and structural integrity. A uniform layer of QD-dispersed PDMS is spin-coated onto the QD film surface. The treated AAO template is then directly pressed onto the QD film surface, maintained under pressure, and placed in a 90°C oven until the microstructures are fully cured. Afterward, the AAO template is removed, and a micropillar array is formed on the QD film surface. The periodicity of the micropillars corresponds to the periodicity of the micropores on the AAO surface, as illustrated in Fig. 2(a). Upon cooling, the PDMS is gently peeled from the template and attached to a reflector. In addition to replicating the microstructures on the AAO surface, the microstructures can also be replicated using an intermediate template. The quartz glass surface is ultrasonically cleaned with anhydrous ethanol and acetone (AR analytical grade), followed by plasma cleaning for 300 s at 150 W. This step ensures that the glass surface adheres firmly to the UV glue, preventing demolding failure. The UV glue (Ormostamp) is evenly spin-coated onto the treated substrate, after which the treated AAO template is pressed onto the substrate under pressure, and UV light is irradiated from one side of the substrate. Due to the high transparency of quartz glass, the UV glue cures completely. Upon removing the AAO template, the intermediate template is obtained. As shown in Fig. 2(b), the intermediate template is then used to replicate the micropore array structure from the AAO surface onto the QD film. The resulting micropillar structures, fabricated using the aforementioned process, are depicted in Fig. 3.

To investigate how different PFA microstructures affect the signal transmission performance of VLC systems, we constructed a custom laser-based VLC experimental platform, as depicted in Fig. 4. This system serves as a proof-of-concept setup to evaluate the practical impact of antenna microstructures on optical signal propagation and reception. It comprises a signal transmitter and receiver, positioned 0.5 m apart. The transmitter couples a sine wave signal generated by an arbitrary function generator (AFG, Tektronix 3251) with a reference signal from a direct current (DC) power supply (DC, Keithley 2231 A) through a bias-T circuit (Bias T, Mini-Circuits ZFBT-4R2GW), which drives a 450 nm laser diode (LD, Guangzhou, 450 nm, 15 W) to convert the electrical signal into a modulated optical signal. On the receiver side, an avalanche photodiode (APD, Meno System APD210), positioned at the edge of the PFA, converts the received optical signal into an electrical signal. The signal is then transmitted to an oscilloscope (OSC, Tektronix TDS2000) for recording and analysis. The signal transmission performance results presented in Fig. 6 were obtained using this VLC system.

When optical signals propagate within the fluorescent antenna, they are modulated by the microstructures, resulting in light reflected at multiple angles. Through total internal reflection from the reflective layer and secondary reflection from the microstructures, these signals are directed toward the antenna edge for capture by the receiver. The impact of microstructures on optical signal transmission is evident, as the presence of microstructures influences signal transmission efficiency. In this section, we evaluate the ability of different microstructures to transmit optical signals toward the edge of the encapsulation layer by analyzing the spectral intensity at the edge of the FA. FAs with micropillar structures (P-PFA) with a period of 600 nm were fabricated using the nanoimprinting technique. A microhole structured fluorescent antenna (H-PFA) with the same period was produced using a secondary imprinting process. A conventional FA without microstructures was also prepared as a control.

To measure the spectral intensity at the antenna edge, the spectral intensities of the two microstructured PFAs and FAs were first recorded under normal and 50° incident angles. A second measurement was taken after wrapping the antenna edge with black tape to shield it. The edge spectral intensity was obtained by subtracting the two measurements. Spectral intensities were recorded using a spectrometer (Ocean Optics, USB 2000+), and the results are shown in Figs. 5(a) and 5(b). As shown in the figures, H-PFA exhibits the highest spectral intensity in both cases, with an increase of 37.9% and 65.2% over the conventional FA for normal and oblique incidences, respectively. In addition, the edge spectral intensity of H-PFA is higher than that of P-PFA with the same period. This improvement is mainly attributed to the microhole structure on its surface, which forms a quasi-continuous porous medium. This structure enhances internal reflection and suppresses vertical transmission, effectively reducing optical leakage and enabling more fluorescence to be guided toward the edge. As shown in Fig. 5(c), the transmittance of H-PFA is lower than that of P-PFA, especially under oblique incidence, which confirms its stronger light-confinement capability. In contrast, the micropillar array in P-PFA presents a more open geometry, resulting in higher transmittance and greater vertical loss. The differences in optical behavior between H-PFA and P-PFA are further illustrated schematically in Figs. 5(d) and 5(e).

Figure 6(a) presents the APD measurement results for PFA and FA at different angles of incidence of the optical signal using a laser-based VLC system. As the angle of incidence increases, signal attenuation becomes more pronounced. The microstructures in the PFA reduce optical signal loss, thereby increasing the output voltage, which surpasses that of the FA at angles of incidence from 0° to 60°. Figure 6(b) displays the average signal gain of the different structures across the FOV. The signal gain is given by Gain=10×lg(PFAP0)=20×lg(VFAV0),(1)where PFA and P0 are the received signal powers with and without the antenna, respectively, and VFA and V0 are the received output voltages with and without the antenna, respectively. It is evident that H-PFA provides the highest signal gain, with an average signal gain of 4.34 dB over the 0°–60° range, while P-PFA offers an average signal gain of 2.53 dB, which is higher than the 1.34 dB average signal gain of the conventional FA. This performance trend is consistent with the spectral results shown in Fig. 5. The lower transmittance and stronger optical confinement provided by the microhole array in H-PFA facilitate more efficient guidance of light toward the detector, especially under large-angle incidence, leading to enhanced signal gain compared to the P-PFA.

Considering that the microstructure of the PFA surface can change the direction of optical signal transmission through diffraction, we used the proposed nanoimprint technology to manufacture a double-sided microhole PFA (2H-PFA) and double-sided micropillar PFA (2P-PFA). Figure 6(c) shows the APD measurement results for double-sided PFAs and the conventional FA under varying angles of incidence. Compared to the single-sided PFAs, the double-sided PFAs demonstrate further improvement in output voltage across the entire 0° to 60° range. This is because in single-sided PFAs, the propagation direction of optical signals only changes due to diffraction when passing through surfaces containing microstructures, while double-sided PFAs increase the probability of diffraction of optical signals when propagating inside the fluorescent antenna due to the presence of microstructures on both surfaces, effectively improving the efficiency of optical signal propagation towards the edge of the fluorescent antenna. This dual interface design significantly enhances the modulation of light propagation direction. Figure 6(d) illustrates the average signal gain of different double-sided PFA structures within the FOV. The 2H-PFA achieves an average signal gain of 6.19 dB, representing a 361% increase over the FA. Additionally, the 2P-PFA structure delivers an average signal gain of 4.03 dB, which exceeds the average signal gain of the P-PFA. In summary, the prepared double-sided PFAs demonstrate higher signal gain over a larger FOV compared to conventional FAs.

In comparison with fluorescent fiber antennas reported in Refs. [13,14], the PFA proposed in this work adopts a fundamentally different strategy for enhancing optical signal transmission. The work in Ref. [13] comprehensively evaluates the performance of red, orange, and green fluorescent fibers in a white-LED-based VLC system, demonstrating how the trade-off between absorption/emission spectra and detector responsivity affects the signal-to-noise ratio and bandwidth. Reference [14] further extends the application of fluorescent fiber antennas to a wavelength-division multiplexing (WDM) VLC system using RGB LEDs and multiple fluorescent fibers. It introduces a subcarrier-level channel estimation method for effective signal separation, and applies pairwise coding (PWC) to mitigate channel imbalance, significantly improving data throughput under different illuminance conditions.

While fluorescent fiber antennas offer advantages in flexibility, fiber–detector coupling, and WDM compatibility, our PFA design leverages patterned microstructures to actively manipulate fluorescence propagation paths. This structure not only enhances photon guidance toward the photodetector but also allows for compact, planar integration. Experimental results confirm that the PFA achieves higher average signal gain across a wide FOV, offering an effective alternative for high-performance VLC reception in integrated photonic systems.

To enhance the signal gain of VLC systems under a large FOV, this study proposes a PFA fabricated using nanoimprint technology. The microstructures on the PFA surface regulate the transmission direction of optical signals within the fluorescent antenna. A VLC system was constructed to evaluate the signal gain of both conventional FA and the proposed PFA across different FOVs. The results demonstrate that the fabricated PFA achieves higher signal gain than conventional FA while maintaining a large FOV. Within an incident angle range of 0° to 60°, both single-sided PFA and double-sided PFA exhibit higher output voltage than conventional FA, with maximum average signal gains reaching 4.34 and 6.19 dB, respectively. These findings show that the proposed PFA provides an effective solution for the development of VLC systems requiring high signal gain under large-FOV conditions.