High power coherent polarization locked laser diode.

Area of Science:

• Optics and Photonics
• Semiconductor Lasers

Background:

• Broad area diode lasers offer high power but suffer from poor beam quality.
• Coherent combining of laser diodes is crucial for achieving high brightness.
• Previous work focused on Gaussian beams, limiting applications for multimode broad area diodes.

Purpose of the Study:

• To demonstrate coherent polarization locking for multimode broad area diode lasers.
• To achieve high-power, single-lobed output from a diode laser array.
• To improve the brightness of broad area diode lasers.

Main Methods:

• Spatially combined four diode emitters using walk-off crystals and waveplates.
• Passively locked diode phases via polarization discrimination.
• Employed a resonator with retro-reflection feedback to mitigate smile effect.

Main Results:

• Produced 7.2 W of coherent output power at 980 nm.
• Achieved a single-lobed, coherent beam with an M2 value of 1.5x11.5.
• Improved diode laser brightness by over an order of magnitude.

Conclusions:

• Coherent polarization locking is feasible for multimode broad area diode lasers.
• The developed technique significantly enhances diode laser brightness and beam quality.
• This advancement opens possibilities for high-power laser applications.