MODE CONVERTER

HERMITE-GAUSS MODE CONVERSION

Introduction

Arbitrary solutions of the paraxial Helmholtz equation can be expressed as combinations of Hermite-Gaussian modes (whose amplitude profiles are separable in x and y using Cartesian coordinates).

For many applications, it is useful to convert the fundamental laser mode TEM00 to a higher order of Hermite-Gaussian beams:

Typical Applications

Feature

• Aberration free
• High efficiency

Typical Optical set-up:

Typical Operating Principle

The operating principle is quite straight-forward – a Fourier Transform (FT) is applied on the initial field amplitude and phase to obtain the desired field (or intensity) at far-field. In this way, the fundamental Gaussian beam TEM_00 is converted to a higher order of Hermite-Gaussian modes. For example – conversion of TEM_00 to TEM_10:

For the phase-plate element, the height of the step is defined as: 

where n is the refractive index of the material.

Design Considerations:

For a high-quality performance, the laser output should be Single Mode (TEM00 with an M2 value <1.3. If the M2 is larger, it may still be possible to reduce the M2 value by inserting a spatial filter in between the laser and the DOE lens component.

All optics in the beam path should be of high quality, i.e. have a low irregularity figure, in order not to introdcue wav-front errors which would degrade the diffractive phase element’s performance.

General Specifications:

Π PHASE-PLATE

Introduction:

For many applications, it is necessary to use a phase element with a π-phase at the center. For imaging purposes using this element will result in an increased depth-of-focus, and for particle manipulation purpose, using this element will result in optical tweezing\trapping.

Standard Products:

Contact us for more information or for a custom solution.