Differentiable design of continuous phase plates using multi-level B-splines with smoothness constraints.

Area of Science:

• Optics and Photonics
• Laser Technology
• Plasma Physics

Background:

• Continuous phase plates (CPPs) are essential for laser beam smoothing in inertial confinement fusion (ICF).
• Existing Gerchberg-Saxton (GS) algorithms have limitations in controlling phase smoothness and avoiding local optima.
• These limitations hinder the practical fabrication and performance of CPPs.

Purpose of the Study:

• To develop an improved CPP design method that enforces phase smoothness.
• To enhance the manufacturability of CPPs for ICF applications.
• To overcome the limitations of traditional GS algorithms in CPP design.

Main Methods:

• Modeling CPP phase distribution using multi-level B-splines.
• Integrating surface curvature and power spectral density (PSD) as regularization terms.
• Employing a multi-scale optimization strategy to avoid local optima.

Main Results:

• The proposed method significantly reduces root-mean-square deviation (RRMSD) compared to modified GS algorithms (59.7%, 51.6%, 47.4% reduction).
• Achieved enhanced phase smoothness, leading to improved manufacturability.
• Demonstrated effectiveness and versatility across multiple design tasks.

Conclusions:

• The novel CPP design method effectively enforces phase smoothness and improves manufacturability.
• The integration of regularization terms and multi-scale optimization addresses key limitations of traditional methods.
• This approach offers a more suitable and robust solution for CPP fabrication in ICF facilities.