
Holmium Laser Theory of Operation
Lumenis Pulse 120H UM-10012510 Rev. F
Page 12
Holmium Laser Theory of
Operation
A laser, an acronym for Light Amplification of Stimulated Emission of
Radiation, produces a highly concentrated beam of light of a given
wavelength. Laser energy is generated by converting electrical energy to
light energy using a flash lamp. The flash lamp energy is then used to
excite the lasing medium, in this case a holmium YAG laser rod. The laser
energy is amplified in the laser resonator cavity and a small portion of the
energy is allowed to leak out as the laser working beam.
The Lumenis Pulse 120H holmium laser emits a laser beam at a
wavelength of 2100 nm. This wavelength is strongly absorbed by water.
Since soft tissue is comprised primarily of water, holmium laser energy
can be used effectively for excision, incision, ablation, and vaporization.
Holmium laser energy is also very effective in lithotripsy of calculi.
When working in liquid environment the holmium laser energy provides
additional safety, since laser energy will be absorbed by the surrounding
liquid, limiting its reach to non-target tissue.
The holmium laser wavelength falls in the mid-infrared region of the
electromagnetic spectrum. This wavelength is invisible to the human eye.
Therefore, a low-power, visible aiming beam is used to verify the laser’s
target tissue.
Laser Power Parameters
Tissue laser interaction is primarily governed by the laser wavelength and
the target tissue absorption coefficient at that wavelength, defining the
effectiveness of the laser energy absorption in the target tissue. However
additional characteristics of the specific laser affect the laser tissue
interaction.
Pulsed lasers (such as the holmium laser) deliver an average power
(measured in Watts) that is achieved by multiplying the laser energy
emitted during each pulse (measured in Joules) and the frequency at
which these pulses are delivered (measured in Hertz). For example the
Lumenis Pulse 120H can deliver a maximum average power of 120W
obtained by delivery of 2 Joules per pulse at a frequency of 60 Hz.