Another option if you have a few mW of power is to use temperature sensitive
liquid crystal sheets from Edmund Scientific that change color with
temperature.
IR detection card
In the distant past I used a CO2 laser (10 um), (to pump an FIR
laser.) there was a viewing 'card'. It was a piece of metal with some
sort of phosphorescent coating. You needed to illuminate it with a UV
light to be able to see the yellowish glow from the CO2 laser. I
have no idea if it would work at 2 um. or if you laser would have
enough power.
http://www.appscintech.com/products/visualizeir
http://www.thorlabs.us/newgrouppage9.cfm?objectgroup_id=296
How to measure the power or energy of a high intensity laser beam with a low threshold meter?
The first step in attenuating a high power laser beam is to pick off or sample a small percentage of the beam from the main beam, without affecting the beam profile of the sampled beam. There are basically three ways to perform this pickoff. The most common is to have a beam splitter that is mostly transmitting and partially reflecting. The beam splitter is typically put in the beam at 45°, so that a small percentage of the beam is reflected at 90° to the incident beam.
The most commonly used beam pickoff surface is quartz, usually used at a 45° angle to the incoming beam. If the quartz is not AR coated, it reflects an average of 4% of the beam per surface. However, at 45° the quartz becomes polarization sensitive, and one polarization is reflected at about 2%, and the other can be as high as 8-10%. Thus the reflected sample beam does not truly represent the incoming laser beam. This problem can be solved by placing a second quartz surface in the path of the initially sampled beam, but angled in a perpendicular plane that reflects the two polarization’s opposite of the first surface. (I.e., the first surface may reflect the beam 90° in the horizontal, and the second surface20 reflects 90° in the vertical.) After two such reflections the sampled beam once again has the same characteristics as the initial beam. (from http://aries.ucsd.edu/LMI/TUTORIALS/profile-tutorial.pdf)