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:

Phase ElementOutput IntensityPhase ElementOutput Intensity
TEM00Mode Converter Mode Converter TEM20Mode Converter Mode Converter
TEM01Mode Converter Mode Converter TEM12Mode Converter Mode Converter
TEM10 Mode Converter Mode Converter TEM21Mode Converter Mode Converter
TEM11Mode Converter Mode Converter TEM22Mode Converter Mode Converter
TEM02Mode Converter Mode Converter

Each mode HGlm is denoted by two indices, l & m, which represent the number of modes in the x & y directions, respectively.

Typical Applications

  • Communication
  • Scientific & research
  • Scanning applications
  • STED microscopy
  • Optical tweezing
  • Optical trapping

Feature

  • Aberration free
  • High efficiency
 

Typical Optical set-up:

Laser Setup lowres

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:

mode converter - Operating Principle

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

step height

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:

Materials:Fused Silica, Sapphire, ZnSe, Plastics
Wavelength range:193[nm] to 10.6[μm]
DOE design:Binary (2-level)
Element size:Few mm to 100 [mm]
Coating (optional):AR/AR Coating
Custom Design:Available

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.

mode converters - Pi phase plate

Standard Products:

Part NumberDiameter [mm]Aperture size [mm]MaterialDescriptionAdd to Quote
PE-20225.423.6 Fused SilicaHalf-space π difference mode converter, TEM01 (or TEM10) Add to Quote
PE-23025.423.6 Fused SilicaQuarter-space π difference mode converter, TEM11 Add to Quote
PE-215119.2Fused SilicaRound π phase at the center, diameter 4817 μm Add to Quote
PE-21623.69.2Fused SilicaRound π phase at the center, diameter 5680 μm Add to Quote
PE-2172023.6 Fused SilicaRound π phase at the center, diameter 6200 μm Add to Quote
PE-21825.4 18.2Fused SilicaRound π phase at the center, diameter 8428 μm Add to Quote
PE-21925.4 23.6Fused SilicaRound π phase at the center, diameter 10838 μm Add to Quote
PE-22025.4 23.6Fused SilicaRound π phase at the center, diameter 7224 μm Add to Quote
PE-221119.2Fused SilicaRound π phase at the center, diameter 3612 μm Add to Quote
PE-222119.2Fused Silica Round π phase at the center, diameter 4214 μm Add to Quote
PE-223119.2Fused Silica Round π phase at the center, diameter 3000 μm Add to Quote
PE-224119.2Fused SilicaRound π phase at the center, diameter 5400 μm Add to Quote
PE-22525.423.6Fused SilicaRound π phase at the center, diameter 6384 μm Add to Quote
PE-22612.5 10.7Fused SilicaRound π phase at the center, diameter 6840 μm Add to Quote
PE-22725.423.6Fused SilicaRound π phase at the center, diameter 8900 μm Add to Quote
PE-228119.2Fused SilicaRound π phase at the center, diameter 1200 μm Add to Quote
PE-229119.2Fused SilicaRound π phase at the center, diameter 1800 μm Add to Quote
PE-24125.422.9Fused SilicaRound π phase at the center, diameter 3860 μm Add to Quote

For a quotation of an above Part Number, please specify the wavelength used.

Contact us for more information or for a custom solution.

References: