Focal shift for a Gaussian beam: an experimental study
Abstract
The beam radius along a focused, unapertured Gaussian beam was measured and used to calculate the dependence of the geometrical Fresnel number on the effective Fresnel number of the beam as it emerged from the focusing lens. The resulting data clearly demonstrate a focal shift away from the focal plane given by geometrical optics. The data agree very well with a theory due to Carter. This theory indicates that a significant focal shift occurs in these beams if the focusing lens is placed within the near field of the focal plane.
- Publication:
-
Applied Optics
- Pub Date:
- December 1984
- DOI:
- 10.1364/AO.23.004345
- Bibcode:
- 1984ApOpt..23.4345S
- Keywords:
-
- Coherent Light;
- Focusing;
- Fresnel Lenses;
- Instrument Errors;
- Lens Design;
- Light Beams;
- Focal Plane Devices;
- Fresnel Diffraction;
- Geometrical Optics;
- Laser Applications;
- Near Fields;
- Normal Density Functions;
- Performance Tests;
- Spectral Energy Distribution;
- Lasers and Masers;
- BEAMS;
- FOCUS;
- DIFFRACTION