The laser power has increased, but the energy density has not increased?

With the continuous upgrading of semiconductor hair removal products, the laser power is also increasing, from 500W to 1000W, and then to 2000W, but the energy density has not increased significantly, why is this?

 

With the continuous upgrading of semiconductor hair removal products, the laser power is also increasing, from 500W to 1000W, and then to 2000W, but the energy density has not increased significantly, why is this?

Before we explain this question, let's take a look at what frequency, pulse width, and energy density are?

(1) Frequency (Hz): the number of times the light is emitted in one second;

(2) Pulse duration (ms): the time of each light emitted;

(3) Energy density (J/cm²): energy per unit area;

So, the question is, why does the laser power increase, but the energy density does not increase?

The main reason is that due to the increase in laser power, the heat generated per unit time will increase sharply (E = P×t), and in order to prevent the laser from being burned out, the laser manufacturer has imposed strict restrictions on the laser parameters (laser power and duty cycle, etc.);

therefore, semiconductor instrument manufacturers cannot rely on their own performance when making designs, and must design according to the parameters specified by the laser; otherwise, the resulting shortening of the laser life or burn-out failure is not covered by the laser manufacturer's warranty.

For example, the parameters of a 1200W laser (maximum duty cycle of 20%) are as follows:

As can be seen from the above figure,

when the frequency is 1Hz (period T=1000ms), the maximum pulse width is 200ms;

when the frequency is 2Hz (period T=500ms), the maximum pulse width is 100ms;

... ...

What parameters are specified by the laser manufacturer that limit the energy?

       From "energy = power x pulse width (E = P×t)", it can be seen that when the laser power increases, the parameter limiting the increase of energy is the pulse duration, and the maximum pulse width of the laser is determined by the maximum duty cycle of the laser.

 

What is Duty Cycle?

Duty cycle is the proportion of light time to total time in a pulse cycle. For example, if the frequency is set to 1Hz, that is, there is light once in 1 second, and 1 second = 1000ms.

(1) For 500W lasers, the manufacturer's maximum light duty cycle is 40%, that is, the maximum pulse width is 400ms;

(2) For 1200W lasers, the manufacturer stipulates that the maximum light output duty cycle is 20%, that is, the maximum pulse width is 200ms;

(3) For 2000W lasers, the manufacturer stipulates that the maximum light duty cycle is 12%, that is, the maximum pulse width is 120ms;

In summary, according to "energy = power x pulse width (E = P×t)", although the laser power increases, the maximum pulse width decreases, and the overall energy does not increase significantly.

If the energy density is not increasing, why pursue more power? We know that hair removal is a process of energy accumulation, that is, under the appropriate energy density, the energy accumulates to a certain extent, the hair follicles will be destroyed, and the hair will lose its ability to regenerate, so as to achieve the effect of permanent hair removal.

The higher laser power and narrower pulse width can effectively reduce the pain of hair removal, improve the comfort experience, and further enhance the hair removal effect.

Some people say that hair removal will become more and more frequent and thicker, is it true?

If you use laser hair removal, it may be that the laser energy density is too low or the cumulative energy is insufficient, which does not destroy the hair follicles and hair follicle growth stem cells, but accelerates blood circulation due to heat, causing the hair to absorb more nutrients and fall out more and more. As long as you choose the right energy or accumulate enough energy, the hair will gradually decrease.

In the end, you will find that if the energy density of the instrument you see is adjusted to the maximum, and the pulse width can be adjusted arbitrarily without limitation, then most of the parameters of this machine are fake, because this is not scientific!