This is a CO2 surgical laser built by Laser Dynamics in Ernest Junction, Queensland. It is a continuous wave laser meaning that it produces a continuous beam rather than pulses. This particular laser has an output power of up to 80 watts with a 10 µm wavelength. Lasers such as these are used during surgery to cut tissue. This laser is missing its focusing unit (the handheld device the surgeon would direct the laser beam with, located at the end of the articulated arm) and the side of the device has been opened to allow the inner sections of the device to be seen.
A laser is made up of three main sections: an energy source, a gain medium, and an optical resonator. The optical resonator consists of two parallel mirrors, placed either end of the gain medium. In the case of a CO2 laser the gain medium is gaseous CO2. For this kind of laser, the energy source, also known as the ‘pump’, consists of an electrical discharge in a mixture of CO2, N2, and He. CO2 molecules are excited into vibrating by collisions and can then shed this energy through emission of photons. The wavelength of the photons is 10µm, which we experience as “radiant heat”. Other materials and compounds will produce different wavelengths.
Once some photons have been produced within the optical resonator by ‘spontaneous emission’, they reflect repeatedly between the two mirrored ends of the optical cavity. As they reflect, they cause a second emission effect within the cavity called ‘stimulated emission’. Stimulated emission occurs when an already-excited atom or molecule interacts with a photon with an equal amount of energy. This interaction forces the atom or molecule to emit an identical photon. Essentially, as light reflects back and forwards through the cavity, it forces the CO2 to produce more and more light. One of the mirrors on the end of the cavity is partially transparent, allowing some radiation to pass through and leave the cavity.
The CO2 laser was invented at Bell Labs in 1964, and was for a long time the most powerful continuous wave laser available. The first time a laser was used in a surgical operation, however, was in December 1961 when Dr. Charles J. Campbell used a ruby laser to destroy a retinal tumor.
This item is part of the UQ Physics Museum ‘2015, International Year of Light’ Tour
< Previous Item | Return to Tour Menu | Next Item >
JDB, SN
End of discharge tube, mirror assembly, and entry to articulated arm
Power supply heat exchanger
Operator's control panel
