Development of compatible air-gap etalons used with both terahertz wave and near-infrared light

We have developed compatible air-gap etalons that can be used with both terahertz (THz) waves and near-infrared (NIR) light. The free spectral ranges for a THz wave and NIR light were in good agreement. This result shows that the air-gap etalons can be used to link the frequencies of two rays. This new type of etalon has potential for use as a simple and easy validation tool for THz time-domain spectroscopy.