Spectral filtering in a diode-pumped Nd:YLF regenerative amplifier using a volume Bragg grating.

Area of Science:

• Laser Physics
• Optical Engineering

Background:

• Amplified Spontaneous Emission (ASE) is a fundamental noise source in regenerative amplifiers.
• Controlling ASE is crucial for achieving high-quality laser output.

Purpose of the Study:

• To demonstrate instrument-limited suppression of out-of-band ASE in a Nd:YLF Diode-Pumped Regenerative Amplifier (DPRA).
• To evaluate the effectiveness of a Volume Bragg Grating (VBG) as a spectrally selective element for ASE reduction.

Main Methods:

• Utilized a Volume Bragg Grating (VBG) with high diffraction efficiency (99.4%) and narrow reflection bandwidth (230-pm-FWHM).
• Integrated the VBG into a Nd:YLF Diode-Pumped Regenerative Amplifier (DPRA) setup.
• Measured the output spectral width with and without the VBG, including under conditions where seed pulse energy approached the ASE background.

Main Results:

• Achieved a significant reduction in the output spectral width from 150-pm FWHM to 43-pm FWHM using the VBG.
• Demonstrated instrument-limited ASE suppression even when the DPRA seed pulse energy was close to the ASE background level.
• The VBG acted as an effective spectrally selective reflective element.

Conclusions:

• Volume Bragg Gratings (VBGs) are highly effective for achieving instrument-limited Amplified Spontaneous Emission (ASE) suppression in Diode-Pumped Regenerative Amplifiers (DPRAs).
• This technique enables significant narrowing of the output spectral width, improving laser performance.
• The VBG's effectiveness is maintained even at high seed pulse energies, making it suitable for demanding applications.