Low-Loss Single-Crystal Sapphire Optical Fibers

Single-crystal sapphire (α-Aℓ203) fibers are potentially useful in a wide variety of optical applications, particularly those involving high-power or high temperature light-guiding, over the wavelength range from 0.24 μm in the ultraviolet to 4.0 μm in the mid-infrared. These fibers are routinely grown at rates of up to 8 mm/min, and with diameter stability of better than 0.5% rms under feedback control. Recent measurements on unclad 150 μm diameter fibers show fundamental mode scattering losses of about 0.3 dB/m in the visible and less than 0.07 dB/m at 3.39 μm.