Compact-cavity two-dimensional Hermite-Gaussian lasing enabled by birefringence-induced astigmatism

Area of Science:

• Laser Physics
• Quantum Optics
• Materials Science

Background:

• Hermite-Gaussian (HG) modes are fundamental solutions in laser cavity theory.
• Achieving stable, controllable 2D HG lasing typically requires complex setups like spatial light modulators or intracavity apertures.
• Neodymium-doped yttrium orthovanadate (Nd:YVO4) crystals exhibit strong birefringence, which can be exploited for optical manipulation.

Purpose of the Study:

• To demonstrate a simple and compact method for achieving controllable two-dimensional Hermite-Gaussian (2D HG) lasing.
• To investigate the role of crystal birefringence and cavity design in modal discrimination.
• To enable axis-aligned 2D HG mode oscillation without external optical elements.

Main Methods:

• Utilizing the intrinsic birefringence of an alpha-cut Nd:YVO4 crystal within a plano-concave laser cavity.
• Employing 2D off-axis pumping to excite laser modes.
• Systematically varying the birefringent crystal length and the cavity length to observe changes in lasing modes.

Main Results:

• Demonstrated controllable 2D HG lasing by exploiting birefringence-induced astigmatism for modal discrimination.
• Showcased the evolution of output modes from tilted one-dimensional (1D) to axis-aligned 2D HG modes with increasing crystal length.
• Confirmed that cavity-length adjustments can enhance modal discrimination, enabling 2D HG oscillation in shorter cavities.

Conclusions:

• A simple and compact route to controllable two-index HG lasing has been verified.
• The intrinsic birefringence of Nd:YVO4 crystals offers an effective mechanism for modal control.
• This approach eliminates the need for pump shaping or intracavity loss elements for achieving 2D HG modes.