Compact dual-crystal optical parametric amplification for broadband IR pulse generation using a collinear geometry

Area of Science:

• Optics and Photonics
• Ultrafast Lasers
• Nonlinear Optics

Background:

• Optical parametric amplification (OPA) is crucial for generating tunable laser pulses.
• Managing group velocity mismatch (GVM) is essential for broadband pulse generation.
• Ti:sapphire lasers are common pump sources in ultrafast optics.

Purpose of the Study:

• To theoretically investigate a novel compact dual-crystal optical parametric amplification (DOPA) scheme.
• To achieve efficient generation of broadband infrared (IR) pulses.
• To improve pulse characteristics such as spectrum, efficiency, contrast, and beam quality.

Main Methods:

• Utilizing a collinear pump configuration with a Ti:sapphire laser (0.8 μm).
• Employing two thin β-barium borate (BBO) crystals with inserted barium fluoride (BaF(2)) wedges.
• Simultaneously compensating for group velocity mismatch (GVM) between interacting pulses.

Main Results:

• Broadband IR pulses generated at non-degenerate wavelengths (1.2–1.4 μm and 1.8–2.1 μm).
• Achieved a nearly 20% broader signal spectrum centered at 1.3 μm.
• Observed increased conversion efficiency, improved pulse contrast, and enhanced beam quality due to better temporal overlap.
• Generated sub-two-cycle idler pulses with low carrier-envelope phase (CEP) fluctuation (<100 mrad RMS).

Conclusions:

• The novel DOPA scheme offers efficient generation of tunable few-cycle IR pulses with millijoule energy.
• The improved pulse characteristics make it suitable for advanced ultrafast research.
• This technique is particularly valuable for driving the generation of ultrafast coherent x-ray supercontinuum.