External Cavity Laser: Ultra Narrow Line Width

  • Context: Graduate 
  • Thread starter Thread starter narra
  • Start date Start date
  • Tags Tags
    Cavity Laser
Click For Summary
SUMMARY

External cavity lasers, specifically diode lasers equipped with external diffraction gratings, achieve ultra-narrow line widths by utilizing the diffraction grating as a tuning mechanism for the central wavelength. Despite the larger cavity potentially introducing more longitudinal modes, the external cavity configuration effectively narrows the linewidth. This counterintuitive result is primarily due to the ability of the external diffractive element to filter and select specific modes, enhancing the laser's performance.

PREREQUISITES
  • Understanding of external cavity laser design
  • Knowledge of diffraction gratings and their role in laser tuning
  • Familiarity with longitudinal modes in laser physics
  • Basic principles of laser operation and cavity dynamics
NEXT STEPS
  • Research the principles of external cavity diode lasers
  • Explore the function of diffraction gratings in laser applications
  • Study the impact of cavity length on longitudinal modes
  • Investigate techniques for measuring laser linewidth
USEFUL FOR

Laser physicists, optical engineers, and researchers focused on high-precision laser applications will benefit from this discussion.

narra
Messages
37
Reaction score
0
Hello,

How does an external cavity laser produce ultra narrow line width when it's larger cavity should reduce the free spectral range and thus introduce more longitudinal modes?

Thanks.
 
Science news on Phys.org
The external cavity lasers I am familiar with are diode lasers that have an external diffraction grating and vertical-cavity surface emitting lasers that use an external distributed Bragg reflector:

http://www.rp-photonics.com/external_cavity_diode_lasers.html

The external diffractive element provides the mechanism for narrowing the linewidth.
 
Hi,

Thanks for your reply. My understanding was that the diffraction grating just provided a means of tuning the central wavelength. I thought that perhaps the fact that the cavity was external was the key to offering ultra narrow linewidth ... although seems counter intuitive since a shorter cavity would promote fewer longitudinal modes.
 

Similar threads

  • · Replies 12 ·
Replies
12
Views
4K
  • · Replies 2 ·
Replies
2
Views
3K
  • · Replies 6 ·
Replies
6
Views
5K
  • · Replies 0 ·
Replies
0
Views
2K
Replies
9
Views
3K
  • · Replies 2 ·
Replies
2
Views
3K
  • · Replies 3 ·
Replies
3
Views
3K
  • · Replies 16 ·
Replies
16
Views
3K
  • · Replies 14 ·
Replies
14
Views
3K
  • · Replies 5 ·
Replies
5
Views
2K