Making fast cylindrical gradient-index lenses diffraction limited by using a wave-front-correction element.

Area of Science:

• Optics and Photonics
• Materials Science

Background:

• High-numerical-aperture gradient-index (GRIN) lenses are crucial for laser beam manipulation.
• Wave-front aberrations limit the performance of conventional GRIN lenses, especially with highly divergent sources like diode lasers.

Purpose of the Study:

• To develop and evaluate a wave-front-correction element (WFCE) for cylindrical GRIN lenses.
• To improve the diffraction-limited performance and beam collimation capabilities of GRIN lenses.

Main Methods:

• Fabrication of a cylindrical Ag-ion-exchanged GRIN lens with a high numerical aperture (0.53).
• Measurement of wave-front aberrations using a phase-shifting shearing interferometer.
• Production of the WFCE with continuous surface relief via a lithographic process.

Main Results:

• The GRIN lens achieved diffraction-limited performance with a wave-front error of 0.02λ rms.
• The WFCE was successfully applied to collimate highly divergent light (57° full diverging angle) from a high-power diode laser.
• The WFCE enhanced the power irradiated into a 2 mrad full angle by a factor of 1.8.

Conclusions:

• A WFCE can effectively correct aberrations in high-NA cylindrical GRIN lenses.
• The corrected GRIN lens significantly improves the collimation of diode laser beams.
• This technology offers enhanced power delivery for applications requiring focused or collimated laser light.