The development of surface processing technology that modulate the intensity of light reflection over a wide wavelength range has important implications for the application of photonics technology. We previously reported that plasma irradiation to a pencil lead formed structural colors. This phenomenon occurs by the thin-layer interference between the clay in the pencil lead exposed by the plasma etching and the surface graphite of the sample. We now report that a pencil lead irradiated with plasma for a long time becomes a new photonic material that caused interference in the near-infrared or mid-infrared range. The thickness of the clay layer exposed by the plasma etching increased with the increment of the plasma irradiation time, and the reflection spectra in the near-infrared and mid-infrared ranges were changed by the light interferences. In addition, the reflection spectrum pattern of the plasma-treated sample well agreed with the simulated pattern based on a thin-layer interference model. According to this method, photonic materials with the desired reflectance over a wide wavelength range can be produced by varying the plasma irradiation time. Furthermore, the irradiation time required to produce the desired optical material can be estimated by the simulation. The infrared reflective area can be easily controlled by using a masking plastic plate. With this method, we succeeded in forming letters on the sample that could only be read by an infrared camera.