ScIentIFIc RepoRts | 7: 16699 | DOI:10.1038/s41598-017-16968-0
Interface and material engineering
for zigzag slab lasers
, Siyu Dong
, Jinlong Zhang
, Hongfei Jiao
, Bin Ma
, Zhanshan Wang
Laser damage of zigzag slab lasers occurs at interface between laser crystal and SiO
lm. Although an
layer could be used to manipulate electric-eld on the crystal-lm interface, their high
absorption and polycrystalline structure were unacceptable. SiO
was then doped in HfO
its crystallization and to achieve low absorption by annealing. Hf
nanocomposite layers were
then inserted between laser crystal and SiO
lm to minimize electric-eld at crystal-lm interface.
Laser damage resistance of this new architecture is two times higher than that of traditional zigzag slab
e zigzag slab architecture is widely used in high power lasers. It can restrain thermally induced lensing and
birefringence to obtain high output energy and exceptional beam quality
. Extremely high laser power has
been obtained using zigzag slab laser architecture by Northrop Grumman
. Usually, the total internal reection
(TIR) in zigzag slab architecture is achieved by depositing lower index coatings on the surfaces of a laser crystal.
Moreover, the coating is connected to the heat sink to take waste heat away
. When laser passes a zigzag path
between two TIR surfaces in the crystal, strong electric-eld intensity (EFI) is created. e coating must have low
absorption, otherwise the joint eect of EFI and absorption will induce strong thermal eects and decrease the
beam quality. SiO
is the dominant material for zigzag slab lasers due to its extremely low absorption from near
ultraviolet to near infrared region.
When the operating uence of laser is higher and higher, the laser-induced damage becomes a severe issue.
e crystal-lm interface is the most vulnerable to laser damage, because massive nano-sized absorbers are cre-
ated in vicinity of crystal-lm interface due to surface contamination, polishing residues in the subsurface of the
laser crystal, extraction of defects during coating deposition, or microstructure mismatch between the crystal and
. Laser damage at crystal-lm interface is induced by the joint contribution of nano-sized absorbers
and strong EFI
. e laser-induced damage threshold (LIDT) can be increased either by removing the mas-
sive nano-sized absorbers near crystal-lm interface or by reducing EFI in vicinity of the crystal-lm interface.
Because it is quite challenging to remove all these nano-sized absorbers at crystal-lm interface, the approach that
reduces EFI is very promising. However, until now, the laser crystal with a SiO
coating is the only used cong-
uration. No other slab laser architecture has been proposed to minimize EFI at crystal-lm interface to improve
LIDT. It is highly desirable to explore novel slab laser architecture to replace the traditional one.
Our previous studies have investigated the high reection (HR) coatings that were irradiated from crystal-lm
. It was found that adding a high index coating between the laser crystal and SiO
thin lm could
minimize the EFI at crystal-lm interface and increase the laser damage resistance. However, there is a cru-
cial dierence between HR coatings and TIR coatings. Standing-wave EFI is created in HR coatings, whereas,
evanescent-wave EFI develops in the SiO
layer for the TIR case. What a role that evanescent-wave EFI plays in
laser damage and the experimental studies of interfacial damage of TIR surfaces have been rarely reported. In
this work, the laser damage characteristics of traditional zigzag slab lasers was rst investigated. en, interface
and material engineering were performed to nd novel architecture of the zigzag slab lasers with increased LIDT.
Results and Discussion
Laser damage characteristics of the traditional zigzag slab lasers.
e traditional conguration of
the zigzag slab Nd:YAG laser working at 1064 nm is given in Fig.1(a). e dimensions of slab are about 1.7 mm
high, 67 mm long, 11 mm wide and 45° angle cut at the end. e crystalline orientation of Nd:YAG crystal is (111).
MOE Key Laboratory of Advanced Micro-Structured Materials, Shanghai, 200092, China.
Institute of Precision
Optical Engineering, School of Physics Science and Engineering, Tongji University, Shanghai, 200092, China.
Collaborative Innovation Center, Shanghai Jiao Tong University, Shanghai, 200240, China. Fei Liu and Siyu Dong
contributed equally to this work. Correspondence and requests for materials should be addressed to X.C. (email:
Received: 4 October 2017
Accepted: 19 November 2017
Published: xx xx xxxx