Calibration of spatial light modulators suffering from spatially varying phase response

Area of Science:

• Optics and Photonics
• Holography
• Spatial Light Modulator Technology

Background:

• Spatial light modulators (SLMs) exhibit spatially varying phase responses due to factors like liquid crystal thickness, non-uniform electric fields, and laser-induced heating.
• Conventional methods using global look-up tables (LUTs) with scale factors lack the precision needed for applications like holographic optical trapping (HOT).

Purpose of the Study:

• To develop a more accurate method for converting desired hologram phase values to spatial light modulator (SLM) pixel addressing values.
• To address the limitations of existing phase conversion techniques in applications requiring precise control of holographic output fields.

Main Methods:

• A novel approach using a three-dimensional polynomial to map pixel addressing values based on (x, y) position and desired phase values.
• Determining polynomial coefficients by measuring phase response in 8x8 sub-sections of the SLM surface.
• Optimizing polynomial degree for accurate interpolation and replication of measured phase responses.

Main Results:

• The proposed polynomial method significantly improves the accuracy of phase conversion compared to traditional LUT-based approaches.
• Demonstrated enhanced control over trap intensities in holographic optical trapping (HOT) applications.
• Effectively suppressed the occurrence of strong, unwanted 0th order diffraction patterns.

Conclusions:

• The 3D polynomial method offers a highly accurate and computationally efficient solution for SLM phase modulation, even with spatially varying responses.
• This technique is crucial for advancing applications demanding precise holographic field control, such as advanced optical trapping and manipulation.