Development of flexible mid-infrared light delivery system with bioprobe for beam control

The objective of this paper is to fabricate a flexible mid-infrared (IR) light delivery system with bioprobesince remarkable biological effect of mid-IR light and lack of corresponding technical devices. Hollow optical fiber with sealing window of different materials and shapes was fabricated and packaged within a metal tube for delivering mid-IR light and electrical signal. The thickness of the sealing window was optimized consideringmechanical strength, loss, and power density threshold. A bioprobe with a SMA connector was manufactured. A patch cord loaded with low-loss mid-IR hollow optical fiber was prepared and can be connected to the bioprobeby a standard SMA jointer. The loss of the bioprobe was 1.38 dB and 1.07 dB at the wavelength of 5.1 μm and 10.6 μm, respectively. The output beam of the bioprobe can be controlled by sealing windows of different shapes, which had a far-field half divergence angle of 0.03–0.44 rad. The system had a power density threshold of 382 mW/mm² and a loss of 3.44 dB at 10.6 μm. A light delivery system with bioprobe was manufactured, which provided a photoelectric device for the application of mid-IR light in the field of neuroscience. The presented system is of high efficiency electro-optic transmission and of high power density threshold, and the applicable wavelength can be extended to far-IR and terahertz by changing the fabrication process of hollow optical fiber.