Yb3+ has very strong absorption at 980 nm whereas weak absorption at 915 nm. For industrial fiber laser I think they use 980 nm laser.
that is true about absorption strength @ 915 nm and I also mentioned it in my comment. but , the width of absorption line @ 976 nm is much narrower than 915 nm which may cause big problems if temperature flactutation hapoens
Hello,
I agree with your point that at around 915 nm has broader absorption range, but i think, pumping at 915 nm will require more number of passes to extract high energy, because the absorption cross-section at this wavelength is less compared to 980 nm.
Temperature fluctuation will not be a problem if you use wavelength stabilized diode laser as which are slightly expensive.
So, it means commercial manufacturers dont use laser diodes @915 nm for fiber laser pumping. I am wondering why different manufaturers offer high poswer diode lasers ( with power of about 200 w ) @915 nm and mention their applications as fiber laser pumping?
Dear Dr. Massudi,
According to our knowledge almost all of well known fiber laser manufacturers use 980 nm for fiber laser pumping purpose. For example IPG typically use IPG diode laser with 974 nm center wavelength for laser pumping and also SPI Laser use JDSU diode laser for laser pumping. You know both of these diode laser types are very stable and have around 0.1 nm/C center wavelength shift. So there is no concern for laser performance.
in addition of above, all of them use both side pumping configuration (even raycus laser).
Newly ITF introduce a new product with the name of 2kW fiber Laser Engine block. This engine use 915 nm diode laser for pumping and they have claimed to reach high optical efficiency (more than 75%) by minimize splice point inside the laser cavity.
Hi dear Dr. Masoudi
It's right, and let's not forget that the gradual absorption of the input pump along its propagation through the active fiber will result in higher nonlinear effects for the signal.
915nm is some companies'choice , since cost.,thermal management, et., are also their concerns.
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