There is no short answer... look into the laser equipment manual and YES! look into the advanced beam optics settings section.....
C'mon Steve! You can do this!!!

Steve, is this what you're referring to?

"Fluence (J/cms2) = energy density. Note: This information is posted so that mostly anyone reading this could understand what the term "fluence" means with respect to lasers.

Fluence refers to the amount of energy (J) delivered to the treated area (in square centimeters). It is called the dose of energy or energy density. Fluence = Energy/Area."

Laser Properties and Parameters
When working with lasers, there are a few definitions that need to be clearly understood. For continuous-wave lasers, time, power, and spot size are essential. For pulsed lasers, energy per pulse, pulse duration, fluence, and spot size are the most important parameters.

The energy of laser light refers to the number of photons delivered in a single pulse and is measured in joules. Joules are thus suitable to describe the energy of pulsed lasers. The energy per area is the fluence or energy density, which is expressed in joules per cm2.

The power of a laser is measured in watts and expresses the amount of energy the laser releases per unit time, i.e. how many joules are delivered per second (W = J/s). Watts are mainly used for continuous- wave lasers.

Irradiance describes the power density, i.e. watts per square centimeter. It describes the intensity of a continuous- wave
laser beam.

The time over which energy is delivered – i.e. the time of actual lasing, which is especially important in pulsed lasers – is the pulse duration or the pulse width. It can reach anywhere from nanoseconds to seconds.

The frequency (pulse repetition rate) at which the single pulses are delivered is measured in hertz and 1 Hz equals 1 pulse per
second.

The wavelength characterizes the type of laser light and is measured in nanometers. It refers to the distance between two peaks of the light waves.

Finally, the spot size is the diameter of the laser beam, and is measured in millimeters.

Energy joules = watts × seconds
Fluence energy density = joules/cm2 = watts × seconds/cm2
Power watts = joules/second
Irradiance power density = watts/cm2
Pulse duration: seconds, milliseconds, nanoseconds
Frequency hertz = pulses per second
Wavelength: nanometers
Spot size: millimeters

Fluence describes the energy density of a pulsed laser beam: Fluence = intensity × time = watts × seconds = joules area cm2 cm2

Irradiance describes the power density of a continuous wave laser beam: Irradiance = intensity = watts

Now here's something I found online that could be of some use for you:

http://www.ophiropt.com/laser-measurement-instruments/laser-power-energy-meters/services/sensor-finder

Here's something else to chew on when reminiscing of the "Star Wars" days back when power was KING!

http://cobweb.seas.gwu.edu/~mpnl/papers/2009/MK3.pdf

This one is pretty interesting:

http://www.lasers.org.uk/paperstore/micro13.pdf

Finally, these links are always informative and may just be helpful in diagnosing some problems one may encounter with CO2 lasers as well as many other types of lasers:

http://www.repairfaq.org/sam/laserco2.htm#co2opt0

http://www.repairfaq.org/sam/laserfaq.htm#faqtoc

http://www.repairfaq.org/sam/laserlir.htm#lirtoc

That's all for now Steve. P.S. Here's a brochure you might be interested in:

http://www.rli.com/pubs/Industrial_Training_Brochure.pdf

Respectfully,
Henry