Nonlinear optical down- and up-conversion in PPLN waveguides for mid-infrared spectroscopy

Middle-infrared (MIR) spectroscopy in the 2 to 4 µm spectral range is a powerful tool in particular for environmental analysis and monitoring. However, this method suffers from missing compact, tuneable, coherent light sources and sensitive detectors. To overcome these problems to a certain extent we demonstrate consecutive nonlinear wavelength down- and up-conversion in Ti-indiffused periodically poled lithium niobate (Ti:PPLN) waveguides to generate and to detect MIR radiation [1]. In detail, nonlinear difference frequency generation (DFG) using pump and signal sources in the near infrared (NIR) is used in the transmitter. On the receiver side, we apply sum-frequency generation (SFG) to reconvert the MIR signal to the NIR.