Picosecond pulse generation and its simulation in a nonlinear optical mirror mode-locked laser

Area of Science:

• Laser Physics
• Nonlinear Optics
• Solid-State Lasers

Background:

• Diode-pumped solid-state lasers are crucial for various applications.
• Passive mode-locking techniques enhance laser performance, enabling ultrashort pulse generation.
• Lithium triborate (LBO) crystals are effective nonlinear optical materials.

Purpose of the Study:

• To passively mode-lock an Neodymium-doped Yttrium Orthovanadate (Nd:YVO4) laser using a nonlinear mirror.
• To characterize the output performance, including power, repetition rate, pulse width, and beam quality.
• To validate numerical simulations of the steady-state pulse width against theoretical limits.

Main Methods:

• Utilized a nonlinear mirror comprising a lithium triborate crystal and a dichroic output coupler.
• Employed diode laser array pumping for the Nd:YVO4 laser.
• Performed numerical simulations to determine the required average gain for bandwidth-limited pulses.

Main Results:

• Achieved a mode-locked output power of 3.2 W at 1064 nm with 10.0 W pump power.
• Obtained a repetition rate of 178 MHz and a pulse width of 8.4 picoseconds (ps).
• Measured a beam quality parameter (M2) of 1.27 and found good agreement between simulated and bandwidth-limited pulse widths.

Conclusions:

• The nonlinear mirror effectively achieved passive mode-locking of the Nd:YVO4 laser.
• The experimental results align well with theoretical predictions for steady-state pulse width.
• A new definition for double-pass average gain (g(ave)) was introduced and validated through simulation.