FIGURE 4.16
Volume-to-surface ratio S/V
in units of (2πV ) 1/3 vs L/R.
o
15 C
o
22 C
o
25 C
o
40 C
FIGURE 4.15
The cat intuitively knows the inventive principle of changing her
surface-to-volume ratio depending on the external temperature.
4.2.4 Fiber lasers and slab lasers
Fiber laser technology is a perfect illustration of the inventive
principle of changing the surface-to-volume ratio.
Indeed, if the main technical issue with high average
power laser amplifiers is cooling the active medium, then
one would try to increase its surface, without changing its
volume, to enhance thermal exchange with the environment.
Fig. 4.16 clearly demonstrates that the typical geometry of
the active medium (when its length L is similar to its radius
R) is the most disadvantageous, in terms of cooling.
On the other hand, either increasing L/R towards fiber
geometry of the active medium, or decreasing L/R toward
slab geometry, would both have advantages in terms of the
surface-to-volume ratio S/V , thus making it easier to manage
their temperature regimes.
64 unifying physics of accelerators, lasers and plasma
In particular, lasers with ultra-short and ultra-high power
pulse have had their share of challenges. Ultra-short intense
pulses can cause nonlinear effects in the medium, while the
high-power pulses cause heating up of the amplifier medium.
These issues limit the repetition rate, power and efficiency of
laser systems. Some of the most powerful lasers fire just once
every few hours!
4.2.3 Laser repetition rate and efficiency
Let’s take a look at the challenges of high average power
lasers from the point of view of AS-TRIZ. The TRIZformulated problem is as follows: as the intensity of the
pulsed laser light increases, it takes much more time for the
medium to cool down and be ready for its next use. The identified contradiction is between the parameter that needs to be
improved, INTENSITY, and the parameter that gets worse,
REPETITION RATE.
A general principle that can solve this contradiction can
be looked up in nature (see Fig. 4.15) or taken from AS-TRIZ,
where Principle 4, Volume-to-surface ratio, suggests changing
this ratio in order to alter the object’s characteristics (such as
its cooling rate or its fields).
Volume-to-surface ratio S/V
in units of (2πV ) 1/3 vs L/R.
o
15 C
o
22 C
o
25 C
o
40 C
FIGURE 4.15
The cat intuitively knows the inventive principle of changing her
surface-to-volume ratio depending on the external temperature.
4.2.4 Fiber lasers and slab lasers
Fiber laser technology is a perfect illustration of the inventive
principle of changing the surface-to-volume ratio.
Indeed, if the main technical issue with high average
power laser amplifiers is cooling the active medium, then
one would try to increase its surface, without changing its
volume, to enhance thermal exchange with the environment.
Fig. 4.16 clearly demonstrates that the typical geometry of
the active medium (when its length L is similar to its radius
R) is the most disadvantageous, in terms of cooling.
On the other hand, either increasing L/R towards fiber
geometry of the active medium, or decreasing L/R toward
slab geometry, would both have advantages in terms of the
surface-to-volume ratio S/V , thus making it easier to manage
their temperature regimes.
64 unifying physics of accelerators, lasers and plasma
In particular, lasers with ultra-short and ultra-high power
pulse have had their share of challenges. Ultra-short intense
pulses can cause nonlinear effects in the medium, while the
high-power pulses cause heating up of the amplifier medium.
These issues limit the repetition rate, power and efficiency of
laser systems. Some of the most powerful lasers fire just once
every few hours!
4.2.3 Laser repetition rate and efficiency
Let’s take a look at the challenges of high average power
lasers from the point of view of AS-TRIZ. The TRIZformulated problem is as follows: as the intensity of the
pulsed laser light increases, it takes much more time for the
medium to cool down and be ready for its next use. The identified contradiction is between the parameter that needs to be
improved, INTENSITY, and the parameter that gets worse,
REPETITION RATE.
A general principle that can solve this contradiction can
be looked up in nature (see Fig. 4.15) or taken from AS-TRIZ,
where Principle 4, Volume-to-surface ratio, suggests changing
this ratio in order to alter the object’s characteristics (such as
its cooling rate or its fields).