TE, TM and TEM Modes in Lasers

In summary, the conversation discusses confusion about the definitions of TE and TM modes in relation to semiconductor laser diodes. The person is seeking clear explanations and recommendations for learning these definitions. A helpful resource is suggested, along with a brief explanation of the differences between TE, TM, and TEM modes. The importance of double-checking definitions is also emphasized.
  • #1
Septim
167
6
Greetings everyone,

I am confusing the definitions in the title of the post all the time. I have books about lasers, yet none of them explain these concepts lucidly and clearly in my opinion. For example, what is our reference plane when we are dealing with semiconductor laser diodes and mention TE and TM modes? How can a mode be TEM; are there two reference planes? These sort of questions always confuse my mind and the books I found usually aim too high or too low with regard to my level in my opinion. Where can I learn these definitions by heart? Please do not hesitate to post your suggestions and ideas.

Thanks in advance
 
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  • #2
Does this help: http://www.imedea.uib.es/~salvador/coms_optiques/addicional/ibm/ch02/02-13.html
 
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  • #3
UltrafastPED said:
Does this help: http://www.imedea.uib.es/~salvador/coms_optiques/addicional/ibm/ch02/02-13.html

Thanks, I will have a through look on this text, by the way I think TE and TM definitions for waveguides and lasers are similar. That is for example in a semiconductor laser in TE mode electric field of the wave is perpendicular to the p and n type planes at the end of semiconductor materials.
 
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  • #4
A TE mode is one where the B-field component in a given direction (typically z; whatever the longituinal direction is) is 0.
A TM mode is one where the E-field component in a given direction is 0.

A TEM mode is one where neither the Magnetic or Electric fields are 0 in said direction.

Remember modes = solutions to the PDE that governs the device. TE and TM definitions are usually the same for waveguides and lasers, but it is not compulsary...it always pays to double-check these things.

Claude.
 
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1. What are TE, TM, and TEM modes in lasers?

TE, TM, and TEM modes refer to different types of electromagnetic modes that can exist inside a laser. In a laser, light is confined within a resonator cavity, and the different modes correspond to different patterns of standing waves that can be formed within the cavity.

2. How do TE and TM modes differ?

TE and TM modes differ in the orientation of their electric and magnetic fields. In TE (transverse electric) modes, the electric field is perpendicular to the direction of propagation, while in TM (transverse magnetic) modes, the magnetic field is perpendicular to the direction of propagation.

3. What is the difference between TE and TEM modes?

The main difference between TE and TEM (transverse electromagnetic) modes is that in TEM mode, both the electric and magnetic fields are perpendicular to the direction of propagation. This means that there is no net flow of energy in the direction of propagation, making TEM mode useful for transmission of signals.

4. How do these modes affect the performance of a laser?

The mode that a laser operates in can affect its output power, beam quality, and stability. For example, TEM modes tend to have a lower output power and less stability compared to TE and TM modes. The choice of mode can also impact the efficiency of the laser and the type of beam that is produced.

5. How are TE, TM, and TEM modes controlled in a laser?

The selection and control of modes in a laser can be achieved through the use of specialized mirrors and lenses within the resonator cavity. These components are designed to shape and manipulate the electromagnetic fields, allowing for the selection of specific modes and control over the laser's performance.

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