Alignment-free difference frequency light source tunable from 5 to 20 µm by mixing two independently tunable OPOs

Area of Science:

• Optics and Photonics
• Spectroscopy
• Laser Technology

Background:

• Tunable mid-infrared ultrashort lasers are vital for vibrational spectroscopy.
• Current systems often use difference frequency generation (DFG) with birefringent phase-matching, causing beam pointing instability due to crystal rotation.
• Stable beam pointing is critical for spectroscopic applications.

Purpose of the Study:

• To present a novel DFG concept that eliminates crystal rotation and beam pointing variations.
• To enhance mid-infrared laser performance for spectroscopic applications.
• To enable research in the mid- to far-infrared spectral range.

Main Methods:

• Developed a DFG concept utilizing two independently tunable input beams from synchronously pumped parametric seeding units.
• Compared the new concept against the conventional DFG approach using a single optical parametric amplifier (OPA) or oscillator (OPO).

Main Results:

• The proposed DFG concept avoids crystal rotation, eliminating beam pointing variations over a broad wavelength range.
• Achieved over a tenfold enhancement in photon efficiency for wavelengths beyond 11 µm.
• Maintained milliwatt output power up to 20 µm.

Conclusions:

• The novel DFG concept significantly improves beam stability and efficiency for mid-infrared lasers.
• This advancement is particularly beneficial for beam-pointing-sensitive spectroscopic applications.
• The enhanced performance opens possibilities for research at the mid- and far-infrared spectral border.