What characterizes pulsed mode laser emission?

Pulsed mode laser emission is characterized by having varying on and off cycles, which is commonly referred to as the duty cycle. In this mode, the laser does not operate continuously; instead, it emits energy in bursts or pulses. This pulsing can be beneficial for certain therapeutic applications, as it allows the tissue to have brief periods of rest between pulses, potentially reducing the heat buildup and improving patient comfort.

The duty cycle, defined as the ratio of the time the laser is on to the total time of one cycle (on plus off), can be adjusted to meet specific treatment goals or to target different types of tissue effectively. By manipulating the duty cycle, practitioners can control the intensity and depth of penetration of the laser light.

The other options describe characteristics that do not apply to pulsed mode. For instance, if the laser were on continuously, it would be operating in continuous wave mode, not pulsed mode. Additionally, pulsed lasers do not necessarily operate only at high frequencies; they can have varying frequencies depending on the treatment requirements. Lastly, while pulsed lasers do emit light in bursts, these bursts are not random; they are precisely controlled and deliberate, in contrast to the description of random intervals.