When it comes to cutting with a 100W CO2 laser, the thickness that can be cut is largely dependent on the material being cut. For example, if you are cutting through wood, the thickness that can be cut will be less than if you are cutting through metal. In general, though, a 100W CO2 laser can cut through materials that are up to 1/4 inch thick.
Of course, the thickness that can be cut will also depend on the specific 100W CO2 laser that you are using. Some lasers are more powerful than others, so they will be able to cut through thicker materials. If you are unsure about the capabilities of your specific laser, it is always best to consult the manufacturer or a professional to get the most accurate information.