Analysis and observation of finite beam Bragg diffraction by a thick planar phase grating

Area of Science:

• Optics and Photonics
• Wave Propagation
• Diffractive Optics

Background:

• Planar phase gratings are crucial optical components.
• Understanding beam propagation and diffraction is essential for device design.
• Existing models may not fully capture complex beam-grating interactions.

Purpose of the Study:

• To introduce a numerical-impulse-response technique for analyzing finite-width beam diffraction in planar phase gratings.
• To investigate the influence of the grating-length-to-beam-width ratio on diffraction characteristics.
• To explore the trade-offs between diffraction efficiency and beam profile.

Main Methods:

• Development of a numerical-impulse-response technique.
• Simulation of finite-width beam propagation and diffraction.
• Experimental verification using a planar waveguide geometry.

Main Results:

• The technique accurately models both symmetric and asymmetric diffractions.
• The grating-length-to-beam-width ratio significantly impacts beam-profile distortion and sidelobe suppression.
• Observed a transition from single to multiple diffraction peaks with increasing ratio.
• Demonstrated trade-offs between diffraction efficiency and beam profile.

Conclusions:

• The numerical-impulse-response method is effective for studying beam diffraction in phase gratings.
• Grating and beam dimensions are critical parameters for controlling diffraction outcomes.
• Experimental results confirm the theoretical predictions of beam behavior.