Hermite-Gauss mode conversion
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 Element||Output Intensity||Phase Element||Output Intensity|
Each mode HGlm is denoted by two indices, l & m, which represent the number of modes in the x & y directions, respectively.
- Scientific & research
- Scanning applications
- STED microscopy
- Optical tweezing
- Optical trapping
- 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.
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.
|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|
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.
|Part Number||Diameter [mm]||Aperture size [mm]||Material||Description|
|PE-202||25.4||23.6||Fused Silica||Half-space π difference mode converter, TEM01 (or TEM10)|
|PE-230||25.4||23.6||Fused Silica||Quarter-space π difference mode converter, TEM11|
|PE-215||11||9.2||Fused Silica||Round π phase at the center, diameter 4817 μm|
|PE-216||23.6||9.2||Fused Silica||Round π phase at the center, diameter 5680 μm|
|PE-217||20||23.6||Fused Silica||Round π phase at the center, diameter 6200 μm|
|PE-218||25.4||18.2||Fused Silica||Round π phase at the center, diameter 8428 μm|
|PE-219||25.4||23.6||Fused Silica||Round π phase at the center, diameter 10838 μm|
|PE-220||25.4||23.6||Fused Silica||Round π phase at the center, diameter 7224 μm|
|PE-221||11||9.2||Fused Silica||Round π phase at the center, diameter 3612 μm|
|PE-222||11||9.2||Fused Silica||Round π phase at the center, diameter 4214 μm|
|PE-223||11||9.2||Fused Silica||Round π phase at the center, diameter 3000 μm|
|PE-224||11||9.2||Fused Silica||Round π phase at the center, diameter 5400 μm|
|PE-225||25.4||23.6||Fused Silica||Round π phase at the center, diameter 6384 μm|
|PE-226||12.5||10.7||Fused Silica||Round π phase at the center, diameter 6840 μm|
|PE-227||25.4||23.6||Fused Silica||Round π phase at the center, diameter 8900 μm|
|PE-228||11||9.2||Fused Silica||Round π phase at the center, diameter 1200 μm|
|PE-229||11||9.2||Fused Silica||Round π phase at the center, diameter 1800 μm|
For a quotation of an above Part Number, please specify the wavelength used.
Contact us for more information or for a custom solution.
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