Adding a second AgGaS₂ stage to Ti:sapphire/BBO/AgGaS₂ setups increases mid-infrared power twofold

Area of Science:

• Optics and Photonics
• Laser Physics
• Nonlinear Optics

Background:

• Conventional methods for generating mid-infrared (mid-IR) laser pulses often involve optical parametric amplifiers (OPAs) and difference frequency generation (DFG).
• Ti:sapphire amplifiers are commonly used pump sources for these systems.
• Existing DFG stages often discard near-infrared (NIR) light, representing a loss of potential energy.

Purpose of the Study:

• To present a novel method for significantly increasing the power of mid-infrared laser pulses.
• To improve the overall photon conversion efficiency in mid-IR generation.
• To achieve higher mid-IR pulse energy without requiring additional pump power from the primary laser source.

Main Methods:

• Implementing an additional parametric amplification stage using a second AgGaS₂ crystal.
• Utilizing selected near-infrared (NIR) outputs (∼1.9 µm) from the conventional DFG stage as a pump for the new amplification stage.
• Employing dichroic mirrors to manage and direct the optical beams.

Main Results:

• The proposed method successfully amplifies mid-infrared light twofold.
• The technique reuses typically discarded NIR light, enhancing overall energy efficiency.
• Characterization shows minimal changes in pulse properties (center frequency, bandwidth, duration) for ∼150-fs pulses between 4 and 5 µm.

Conclusions:

• The presented method offers an effective way to boost mid-infrared laser power and photon conversion efficiency.
• This approach is cost-effective as it reuses existing components and discarded light, avoiding the need for additional pump lasers.
• The technique is suitable for generating high-power, ultrashort mid-IR pulses with preserved spectral and temporal characteristics.