The mid-to-long-infrared spectral range (3–15 μm) is of high interest for a multitude of material processing and spectroscopic applications due to wavelength-specific absorption features of many polymers and organic molecules in this spectral region. Especially narrowband, spectrally wide tunable mid-to-long-IR source reaching μJ-level pulse energies are attractive due to their ability to address specific absorption bands of the target materials. Common sources for narrowband, wide spectral tunable pulse generation are pico- or nanosecond optical parametric oscillators (OPO) or parametric amplifier systems (OPA) combined with a subsequent difference frequency generation stage in order to reach the mid-to-long-infrared spectral region. In contrast optical parametric generators (OPG) possess a much higher simplicity of the optical design compared to OPOs or OPAs due the absence of specifically designed optical cavities nor the requirement of an optical seed. On the downside, the spectra generated in OPG systems are typically only limited by phase-matching constraints and therefore the generated bandwidth can be very broad and can vary significantly over the full spectral tuning range.