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

Middle-infrared (MIR) spectroscopy in the 2 to 4 mum 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. 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.