Mid-infrared laser (2 ~ 5μm) covers a number of atmospheric transmission window and many molecular chemical bond absorption peak "fingerprint" area, in space optical communications, environmental monitoring, medical, military and other fields have important application prospects. There are many technologies for producing mid-infrared laser. Among them, the mid-infrared laser technology based on direct pumping rare earth doped crystals has the advantages of simple structure, continuous output and high beam quality. Directly pumping erbium ion (Er3 +) -doped laser crystals is one of the most important technologies to realize mid-infrared laser in the 3μm band. In order to solve the problem of self-terminating effect of laser oscillation caused by the upper level (4I11 / 2) of Er ion 3μm laser output channel, the high-level doping of Er ions is adopted, The miscellaneous concentrations tend to be above 30 at% and even 50 at%. However, high concentration doping can cause the thermal conductivity of the laser crystal to decrease sharply, and the quenching of the upper level of the laser level (4I11 / 2) increases, resulting in limited output power and low laser efficiency in the 3μm band.
Prof. Su Liangbi, Ph.D., Shanghai Institute of Ceramics, Chinese Academy of Sciences (CASS), using clusters of low-phonon energy strontium fluoride (SrF2) as the doping matrix and clusters of rare earth-doped ions "Effect, overcomes the 3 m laser oscillation self-termination effect at extremely low doping concentration (<5 at%) of Er3 + ions, and achieves high-efficiency dual-wavelength laser output. When at%, the energy level life under 3μm laser is 1.58 times of the upper level, less than 4 at% at% at% at% at% ms? Cm2, higher than ms? Cm2 and much higher than ms? Cm2 and ms? Cm2 . The group worked with Professor Liu Jie from Shandong Normal University to directly pump 4at.% MW laser diodes with laser wavelengths of about 2789 nm and 2791 nm (2016 Scientific Reports 6, 36635).
Previously, the group worked with Shandong Normal University to make graphene a saturable absorber with an average output power of 172 mW at 4 at% μs, repetition frequency of 62 kHz (2016 Optical Materials Express 6, 1570-1575; 2016 Optical Materials Express 6, 409-415). On this basis, self-Q-switched laser output (ie, no additional saturable absorber needed) is excited at 3 at% Er, 0.03 at% μm by co-doping of excited ions Pr3 + with a pulse width of 718 ns and a repetition frequency of 52 kHz , With an average output of 262 mW (2016 Optics Letters 41, 4660-4663).
The above work has been funded by the National Natural Science Foundation of China, key projects and outstanding youth fund.
LD direct pump 4at.%
LD direct pump 4at.%
LD direct pump 3at.% Er, 0.03at.%
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