What is a Laser

Laser Components

Time Modes of Operation

Laser Modes

Longitude Modes

Tramsverse Modes

M2 Factor

Wavelength Chart

DPSS Laser

Infrared Filter

Apparent Brightness

Laser Safety

Laser Classification

Laser Modes

The fundamental TEM00 mode is only one of many transverse modes that satisfy the round-trip propagation criteria. The figure below shows examples of the primary lower-order Hermite-Gaussian (rectangular) solutions to the propagation equation.

Hermite modes
Low-order Hermite-gaussian resonator modes

Note that the subscripts n and m in the Eigenmode TEM nm are correlated to the number of nodes in the x and y directions. In each case, adjacent lobes of the mode are 180กใ out of phase.

The propagation equation can also be written in cylindrical form in terms of radius (r) and angle (f). The eigenmodes (Erf) for this equation are a series of axially symmetric modes, which, for stable resonators, are closely approximated by Laguerre-Gaussian functions, denoted by TEMrf. For the lowest order mode, TEM00, the Hermite-Gaussian and Laguerre-Gaussian functions are identical, but for higher order modes, they differ significantly, as shown in the figure below.

Low-order axisymetric resonator modes

The mode, TEM01*, also known as the "bagel" or "doughnut" mode, is considered to be a superposition of the Hermite-Gaussian TEM10 and TEM01 modes, locked in phase quadrature.

In real-world lasers, the Hermite-Gaussian modes predominate since strain, slight misalignment, or contamination on the optics tends to drive the system toward rectangular coordinates. Nonetheless, the Laguerre-Gaussian TEM10 "target" or "bulls-eye" mode is clearly observed in well-aligned gas-ion and helium neon lasers with the appropriate limiting apertures.

Home | Company Profile | Lasers | Optics | Crystals | Support | Constact
Copyright © 2002-2008 by Shanghai Dream Lasers Technology Co., Ltd.