Birefringent beam splitter for intracavity mode selection in high-power multimirror lasers

Area of Science:

• Optics and Photonics
• Laser Physics
• Materials Science

Background:

• Interferometric laser resonators require efficient beam splitting and output coupling.
• Controlling axial modes is crucial for laser stability and performance.
• Free-electron lasers (FELs) benefit from enhanced temporal coherence.

Purpose of the Study:

• To describe the design and application of an uncoated sapphire plate as a dual-function optical element.
• To demonstrate its use in an interferometric laser resonator for an rf linac free-electron laser.
• To analyze its effect on temporal phase coherence and axial mode reduction.

Main Methods:

• Utilizing a single uncoated sapphire plate for both beam splitting and output coupling.
• Employing p-polarized (TM) reflection near Brewster's angle for output coupling.
• Using s-polarized (TE) reflection at the same angle for axial-mode selection.
• Analyzing the impact on pulse coupling and temporal phase coherence in an FEL.

Main Results:

• The sapphire plate effectively serves as both beam splitter and output coupler.
• P-polarized reflection near Brewster's angle enables efficient output coupling.
• S-polarized reflection at the same angle enforces axial-mode selection.
• Coupling of optical pulses induces temporal phase coherence, reducing axial modes in the FEL output.

Conclusions:

• The described sapphire plate design offers a novel and efficient solution for laser resonator control.
• This approach enhances temporal phase coherence and reduces axial modes in free-electron lasers.
• The design has potential applications in advanced laser systems, including cavity dumping.