With MoS2 as saturable absorber, passive Q-switching and Q-switched mode-locking operations of a Tm-doped calcium lithium niobium gallium garnet（Tm:CLNGG） laser were experimentally demonstrated. The Q-switched laser...With MoS2 as saturable absorber, passive Q-switching and Q-switched mode-locking operations of a Tm-doped calcium lithium niobium gallium garnet（Tm:CLNGG） laser were experimentally demonstrated. The Q-switched laser emitted a maximum average output power of 62 mW and highest pulse energy of 0.72 μJ. Q-switched mode locking was also obtained in the experiment. The research results will open up applications of MoS2 at the mid-infrared wavelength.展开更多
This paper investigates a switching control strategy for the altitude motion of a morphing aircraft with variable sweep wings based on Q-learning.The morphing process is regarded as a function of the system states and...This paper investigates a switching control strategy for the altitude motion of a morphing aircraft with variable sweep wings based on Q-learning.The morphing process is regarded as a function of the system states and a related altitude motion model is established.Then,the designed controller is divided into the outer part and inner part,where the outer part is devised by a combination of the back-stepping method and command filter technique so that the’explosion of complexity’problem is eliminated.Moreover,the integrator structure of the altitude motion model is exploited to simplify the back-stepping design,and disturbance observers inspired from the idea of extended state observer are devised to obtain estimations of the system disturbances.The control input switches from the outer part to the inner part when the altitude tracking error converges to a small value and linear approximation of the altitude motion model is applied.The inner part is generated by the Q-learning algorithm which learns the optimal command in the presence of unknown system matrices and disturbances.It is proved rigorously that all signals of the closed-loop system stay bounded by the developed control method and controller switching occurs only once.Finally,comparative simulations are conducted to validate improved control performance of the proposed scheme.展开更多
More than 6 W average power ultraviolet radiation at 355 nm was generated in LiB3O5 (LBO) crystal through the frequency mixing of the fundamental and second harmonic radiation of a Nd:YAG laser. This performance was a...More than 6 W average power ultraviolet radiation at 355 nm was generated in LiB3O5 (LBO) crystal through the frequency mixing of the fundamental and second harmonic radiation of a Nd:YAG laser. This performance was achieved with 38% optical-to-optical conversion efficiency (532 nm to 355 nm).展开更多
Stable continuous-wave passive mode-locking of diode-end-pumped Nd:GdVO4 and Nd:YAG lasers with semiconductor saturable absorber mirrors (SESAMs) are reported. The comparative study shows that the Nd:GdVO4 crystal is ...Stable continuous-wave passive mode-locking of diode-end-pumped Nd:GdVO4 and Nd:YAG lasers with semiconductor saturable absorber mirrors (SESAMs) are reported. The comparative study shows that the Nd:GdVO4 crystal is efficient to decrease the Q-switched mode-locking tendency, and easier to continuous-wave (CW) mode lock than Nd:YAG.展开更多
We report on the operation of passively Q-switched waveguide lasers at 1 μm wavelength based on a graphene∕WS_2 heterostructure as a saturable absorber(SA). The gain medium is a crystalline Nd:YVO_4 cladding wavegui...We report on the operation of passively Q-switched waveguide lasers at 1 μm wavelength based on a graphene∕WS_2 heterostructure as a saturable absorber(SA). The gain medium is a crystalline Nd:YVO_4 cladding waveguide produced by femtosecond laser writing. The nanosecond waveguide laser operation at 1064 nm has been realized with the maximum average output power of 275 m W and slope efficiency of 37%. In comparison with the systems based on single WS_2 or graphene SA, the lasing Q-switched by a graphene∕WS_2 heterostructure SA possesses advantages of a higher pulse energy and enhanced slope efficiency, indicating the promisingapplications of van der Waals heterostructures for ultrafast photonic devices.展开更多
We report a high-peak-power, high-repetition-rate diode-side-pumped Nd：YAG Q-switched intracavity optical parametric oscillator （IOPO） at 1.57 μm with a type-Ⅱ non-critically phase-matched x-cut KTP crystal. The ...We report a high-peak-power, high-repetition-rate diode-side-pumped Nd：YAG Q-switched intracavity optical parametric oscillator （IOPO） at 1.57 μm with a type-Ⅱ non-critically phase-matched x-cut KTP crystal. The average power of 1.15 W at 1.57μm is obtained at 4.3-kHz repetition rate. The peak power of the pulses amounts to 33.4 kW with 8-ns duration. The average conversion efficiency from Q-switched 1.0μm-wavelenth input power to OPO signal output power is up to 10.5%.展开更多
基金supported by the National Natural Science Foundation of China (Grant Nos. 61008018 and 11421064)the National Basic Research Program of China (Grant No. 2013CBA01505)
文摘With MoS2 as saturable absorber, passive Q-switching and Q-switched mode-locking operations of a Tm-doped calcium lithium niobium gallium garnet（Tm:CLNGG） laser were experimentally demonstrated. The Q-switched laser emitted a maximum average output power of 62 mW and highest pulse energy of 0.72 μJ. Q-switched mode locking was also obtained in the experiment. The research results will open up applications of MoS2 at the mid-infrared wavelength.
基金supported by the National Natural Science Foundation of China(Nos.61873295,61833016)the Aeronautical Science Foundation of China(No.2016ZA51011).
文摘This paper investigates a switching control strategy for the altitude motion of a morphing aircraft with variable sweep wings based on Q-learning.The morphing process is regarded as a function of the system states and a related altitude motion model is established.Then,the designed controller is divided into the outer part and inner part,where the outer part is devised by a combination of the back-stepping method and command filter technique so that the’explosion of complexity’problem is eliminated.Moreover,the integrator structure of the altitude motion model is exploited to simplify the back-stepping design,and disturbance observers inspired from the idea of extended state observer are devised to obtain estimations of the system disturbances.The control input switches from the outer part to the inner part when the altitude tracking error converges to a small value and linear approximation of the altitude motion model is applied.The inner part is generated by the Q-learning algorithm which learns the optimal command in the presence of unknown system matrices and disturbances.It is proved rigorously that all signals of the closed-loop system stay bounded by the developed control method and controller switching occurs only once.Finally,comparative simulations are conducted to validate improved control performance of the proposed scheme.
基金This work was supported by the programme of High Tech Research And Development (863) Programme and the Project of Knowledge Innovation Program of Chinese Academy of Sciences (KJCX1-05-1).
文摘More than 6 W average power ultraviolet radiation at 355 nm was generated in LiB3O5 (LBO) crystal through the frequency mixing of the fundamental and second harmonic radiation of a Nd:YAG laser. This performance was achieved with 38% optical-to-optical conversion efficiency (532 nm to 355 nm).
基金This work was supported by the National Natural Sci-ence Foundation of China under Grant No.3021001.
文摘Stable continuous-wave passive mode-locking of diode-end-pumped Nd:GdVO4 and Nd:YAG lasers with semiconductor saturable absorber mirrors (SESAMs) are reported. The comparative study shows that the Nd:GdVO4 crystal is efficient to decrease the Q-switched mode-locking tendency, and easier to continuous-wave (CW) mode lock than Nd:YAG.
基金111 Project of China(B13029)Strategic Priority Research Program of CAS(XDB16030700)+2 种基金Key Research Program of Frontier Science of CAS(QYZDB-SSWJSC041)National Natural Science Foundation of China(NSFC)(11274203,61522510)STCSM Excellent Academic Leader of Shanghai(17XD1403900)
文摘We report on the operation of passively Q-switched waveguide lasers at 1 μm wavelength based on a graphene∕WS_2 heterostructure as a saturable absorber(SA). The gain medium is a crystalline Nd:YVO_4 cladding waveguide produced by femtosecond laser writing. The nanosecond waveguide laser operation at 1064 nm has been realized with the maximum average output power of 275 m W and slope efficiency of 37%. In comparison with the systems based on single WS_2 or graphene SA, the lasing Q-switched by a graphene∕WS_2 heterostructure SA possesses advantages of a higher pulse energy and enhanced slope efficiency, indicating the promisingapplications of van der Waals heterostructures for ultrafast photonic devices.
基金This work was supported in part by Tianjin Municipal Technological Development Plan.
文摘We report a high-peak-power, high-repetition-rate diode-side-pumped Nd：YAG Q-switched intracavity optical parametric oscillator （IOPO） at 1.57 μm with a type-Ⅱ non-critically phase-matched x-cut KTP crystal. The average power of 1.15 W at 1.57μm is obtained at 4.3-kHz repetition rate. The peak power of the pulses amounts to 33.4 kW with 8-ns duration. The average conversion efficiency from Q-switched 1.0μm-wavelenth input power to OPO signal output power is up to 10.5%.
