One material that allows almost 100% transmission of infrared, visible, and ultraviolet light is fused quartz. Fused quartz is a high-purity form of quartz glass that has excellent optical properties. It has a wide transparency range, extending from the ultraviolet (UV) region through the visible spectrum and into the infrared (IR) region.
Fused quartz is often used in applications where transparency to multiple wavelengths is required, such as in scientific instruments, optics, and high-temperature environments. It has low absorption and scattering characteristics, allowing light to pass through with minimal loss.
By placing a transparent fused quartz sheet or window above a black (light-absorbing) box, you can allow the transmission of infrared, visible, and ultraviolet light while preventing reflections and absorbing unwanted light within the box.