Quasi-point NIR light source based on laser-driven photoluminescence for eye-safe imaging applications

Near-infrared (NIR) imaging, as a newly emerged technique, demonstrates immense potential in various imaging applications such as biological detection, night vision, and anti-counterfeiting. The imaging quality of the currently available NIR light sources is limited by their low radiant exitance and poor beam quality. Herein, a quasi-point NIR light source based on a laser-driven photoluminescence technique was successfully developed. A single blue laser diode (LD) with a power of ∼2250 mW and a minimum spot size of ≈ 0.13 mm^-2 is employed as the pumping source. A Cr-doped MgO ceramic displaying strong luminescence in the NIR region is used as the emitter. Interestingly, the prepared MgO:Cr ceramic is able to withstand the blue laser irradiation density of > 5600 mW·mm^-2, and therefore, the fabricated NIR light source demonstrates a high radiant flux of ∼234 mW with a high radiant exitance of ∼139 mW·mm^-2. Furthermore, the emitting area is as small as ∼1.6 mm², which is highly beneficial for optical design and device miniaturization. The overall performance of the quasi-point NIR light source in blood vessel imaging and night vision applications is evaluated.