Is 532nm the Optimum Wavelength for Atmospheric Particle Tracking?

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Discussion Overview

The discussion centers on the optimum wavelength for atmospheric particle tracking, specifically questioning whether 532nm is the best choice. Participants explore the implications of laser power specifications in atmospheric pulsed Lidars, the relationship between pulse energy and power, and the factors influencing system design.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions whether the power listed in scientific papers refers to the energy per pulse or the total energy over a second, noting a lack of clarity in the literature.
  • Another participant suggests that it is standard practice to refer to the energy in each pulse, arguing that discussing energy across multiple pulses would complicate communication.
  • A different participant clarifies that power is measured in watts and relates pulse energy to power output, emphasizing the importance of pulse duration in determining meaningful power values.
  • One participant cites an article stating that the optimum wavelength for tracking atmospheric particles is influenced by system design, specifically favoring lidar over radar, and mentions considerations like beam expansion and divergence.
  • A later reply humorously notes the coincidence of 532nm being a common wavelength for high-power visible lasers, suggesting that the choice may be influenced by practical considerations rather than purely optimal performance.

Areas of Agreement / Disagreement

Participants express differing views on the definition of power in the context of laser specifications and the implications of choosing 532nm as an optimum wavelength. There is no consensus on whether 532nm is definitively the best wavelength, as practical and technical factors are debated.

Contextual Notes

Participants highlight the complexity of defining power in terms of pulse energy and the various factors that influence the choice of wavelength for atmospheric particle tracking. The discussion reflects uncertainties regarding definitions and assumptions in the context of lidar technology.

Who May Find This Useful

This discussion may be of interest to researchers and engineers working with atmospheric lidar systems, as well as those studying laser technology and its applications in environmental monitoring.

pyroartist
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TL;DR
Looking for the definition of a term.
In reading scientific papers on atmospheric pulsed Lidars there is often a table that includes system information such as the type of laser, the power in uJ or mJ and the rep rate. Examples of the power would be usually somewhere between 50 uJ and 30 mJ. Rep rates are between 10 and 10,000 pulses a second. Here is just one of many such articles:
http://www.scielo.org.za/scielo.php?pid=S0038-23532009000600018&script=sci_arttext
My question: Is the power listed the value for each pulse or is it the total of the pulses in one second? This has never been made clear in any article so it must be commonly known among Lidar engineers.
If you have a link for this answer I would like to see it please.
Thanks.
 
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If the author does it they way most laser people do, then it's the energy in each pulse. It's just too confusing to talk about the energy in 10, 100, or 1000 pulses, then you would have to also say how many pulses in your definition. Everyone with any sense will default to 1 pulse.

BTW: I didn't read your link, so I may have misunderstood something.
 
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pyroartist said:
Examples of the power would be usually somewhere between 50 uJ and 30 mJ. Rep rates are between 10 and 10,000 pulses a second.
The unit of energy is the joule. The rate of energy flow is power in watts.
A pulse energy of 1mJ repeated 100 times per second would be 100mJ/sec = 100mW.
The power of one pulse is less meaningful. It would be the pulse energy divided by the pulse duration.
 
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From the article:

1608740596249.png


The author states that optimum wavelength to track atmospheric particles determined system design; thus, lidar instead of radar. Average pulse energy refers to multiple pulses over time with attention to beam expansion and divergence at intended target ranges.

Consider also the maximum unambiguous range of pulsed transmit/receive systems. This allows one to optimize PRF/PRT (pulse repetition frequency and its reciprocal, pulse repetition time) depending on required range and vice-versa. The linked calculator applies to radar, lidar and some acoustic models.
 
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Klystron said:
optimum wavelength to track atmospheric particles
LOL, ok. What an unusual coincidence that it landed on/near 532nm, which is the very cheapest (i.e. easiest) wavelength to generate in high power visible lasers, and one that Continuum is good at doing. Thank god they didn't land on 514nm where they might have needed an Ar-Ion laser! Too bad it didn't land on 1064nm which is even cheaper.

OTOH, they said lidar vs. radar. Which is at least a factor of a thousand difference. So, OK, I guess it's optimum by some definition.
 
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