This web page has been laid out in the basic configuration I have developed for the final report. I have filled in each of teh sections I intend to address with the basic questions I have for each.
Molecular lasers like the carbon dioxide laser work on energy level transitions between vibrational, bending, and rotational energy states rather than electron energy level states. In the case of CO2, nitrogen is first excited to vibrational energy states above ground, then this energy is then transfered collisionally to the carbon dioxide molecules. The vibrational energy state of the nitrogen happens to coincide with the upper state of the carbon dioxide, so the pair of gasses make an a very good laser pump path. Helium is a very good conductor of heat so it carries away excess heat allowing the lower pump states to empty faster improving lasing. Even though this is a carbon dioxide laser, carbon dioxide is the smallest component in the laser's gasses.
I am interested in developing a deeper understanding of the physics of the lasing cycle of molecular gas lasers like the carbon dioxide laser.
Unlike early lasers which were built in a logitudnally excited fashion, like most gas lasers, most are now built in a transversly excited configuration. The transvers configuration allows the laser to be operated at higher pressures and lower voltages achieving greater power output and safety.
By exciting the gas at radio-frequencies it is possible maintain the stability of the plasma over a wider range of powers as well as quickly start and stop lasing in the laser. Synrad's CO2 lasers (the 10 watt model at least) can be pulsed in excess of 5 kHz with their standard driver. This proces is less efficient in comparison to just DC transverse excitation since the active devices at radio-frequencies waste a considerable amount of power. It is my interest to find information on the driving circuitry as well as gaining a deeper understanding of how the RF excitation effect the laser's operation.
Carbon dioxide lasers produce a high average output power and operate with high efficiency making them especially suited to many industrial applications such as cutting and welding. It is my interest, in this research project, to learn more of the mechanisms and processes that CO2 lasers operate on as well the material processing methods they are used for.
Since laser marking has been the subject of another project of mine for this paper I will look primarily at information on areas outside of what I was able to experiment on. Particular areas of interest here include the marking metals and other materials requiring higher power densities than was available for my project.
What range of power is necessary for marking materials? What type of optics are typically used for high resolution marking? These questions are ones I would like to find in this research project. Of interest here will also be attempting to separate the power actually required vs. the power used because 'look at what our new laser can do.'
What systems are available or are in common use? How do they compare with each oher and with the concept I used in my laser marking project?
Some of the questions I seek to answer include: How does metal respond to laser marking. What effect is there between power and feed rate.
This appears to be an interesting process. I saw the product of this process recently, and it would be very interesting to know what type of power is necessary, and by what process the stone was etched -- looked more like a separation process had flaked material from the surface. A major question will be if there is there any information on this or if it is still all too proprietary? One part I don't know yet is if it was done with a CO2 laser, or if it would even work with one?
What other innovative uses are there for laser marking with CO2 lasers?
A major industrial use for CO2 lasers is cutting. They are used to cut a wide variety of materials, and avoid many problems common to other methods. No force is placed on the material being cut, so clamping forces and positioning motors can be small. Heating is very localized so heat damage to the surrounding material can be minimized, as opposed to other methods such as using a cutting torch. And unlike high pressure water streams the material being cut is soaked.
My interest here is to compile information on the range of laser output power levels used to perform cutting operations on a variety of materials.
Of interest is the types of systems commonly used and available as well as improvements on the horizon -- if there are many, since this is a fairly mature technology. Are such systems high power marking systems or does the increase in power have other effects? I would like to find what methods are commonly used for beam delivery, material transport, laser construction, optics, etc.
Compile information on how various materials respond to laser cutting. Special measures that must be taken.a Materials suited/ not suited to laser cutting.
Works on small scale -- some articles/books indicate larger scales also work -- what range works, are there scales best done with other methods?
What range of power is suitable for laser welding; at different scales, in different materials?
What type of systems are out there for welding what type of laser construction/ operation is used. Any special requirements imposed by this process or is a laser cutting system capable of welding operations?
What effects does laser welding have on the material besides just fusing them together? What range of materials are candidates for laser welding? Types of metals, plastics, other materials?
Laser separation is an interesting process for separating (cutting--sort of) brittle materials than are susceptible to heat stress. Some information indicates that laser separation is capable of cutting complex shapes from such brittle materials. Obviously there must be limits to this, what are they, do they allow this to be a truly useful process.
What ranges of power are necessary to separate various materials? What are the consequences of operating outside this range?
Can standard systems for applications such as cutting be used for this, are there specialized systems, is this method used in industry, and how much is it used.
What types of materials are candidates for this process. Glass works, what about crystalline structures, are they brittle enough?
Kelin Kuhn, Introduction to Carbon Dioxide Lasers
Ed. Peter K. Cheo, Handbook of Molecular Lasers, New York: MARCEL DEKKER, INC., 1987.
William M. Steen, Laser Material Processing, London: Springer-Verlag, 1991.
O.D.D. Soares, M. Perez-Amor Editors, Applied Laser Tooling, Dordrecht, The Netherlands: Martinus Nijhoff Publishers, 1987.