There is an increasing demand for high-intensity subnanosecond lasers for emerging industrial applications. While femtosecond and picosecond laser sources are considered promising, they suffer from the significant drawbacks of increased complexity and cost. In this regard, we demonstrate a unique edge-pumped passively Q-switched Nd∶YAG/Cr4+∶YAG microchip laser. The microchip is made of a Nd∶YAG/Sm∶YAG composite ceramic, and a Sm∶YAG cladding is utilized as both the pump beam waveguide and amplified spontaneous emission absorber. With the use of a flat-concave laser cavity, we obtain single-pulse energy of 1.66 mJ for an absorbed pump energy of 24 mJ. Further, the resulting pulse width is 683 ps, and the repetition rate is 10 Hz.
The output performances of a compact, passively Q-switched Nd:YAG/Cr4+:YAG laser were investigated using single
crystals and poli-crystalline ceramics Nd:YAG with doping level between 1.0 and 2.0-at.% Nd, and single crystals and
poli-crystalline ceramics Cr4+:YAG with various initial transmission. Q-switch laser pulses at 1.06 μm with energies up
to 2 mJ and duration below 1 ns were realized at a pump repetition rate of 10 Hz. An all-ceramics Nd:YAG/Cr4+:YAG
laser could be a solution for ignition of automotive engines. The optical intensity of a laser pulse with ns duration that
induces optical air breakdown was determined.
Recently, the advantages of Yb:YAG materials for high-power and short-pulse lasers are well recognized because of its low thermal loading and broad emission bandwidth even if it is a quasi-four-level system. A face-cooled microchip, equivalent configuration to the active mirror, can reduce the thermal problems. Additionally, it is possible to minimize the re-absorption loss in Yb:YAG due to its short active medium in compensation for the pump absorption degradation. Our approach to this problem is to employ an edge-pumping configuration. Pump light propagates from the edge of outer transparent composite ceramic YAG wave-guide to the internal single crystal Yb:YAG small core without optical loss by total internal reflection. Proper designs of core size and Yb concentration allow efficient pump absorption in the core. It should be emphasized that the absorption ratio of pump light in the core does not depend on the thickness of the microchip then thinner microchip allows higher pump power absorption intensity and higher gain in the core. The sintering method has advantages in composite structure fabrication due to its solid-solution nature. It is attractive for actual applications because of low fabrication cost by mass production and short delivery time compared with conventional diffusion bonding. In this research, we'd like to report about >300 W CW laser operation in edge-pumped 300μm-thick, single crystal Yb:YAG/ceramic YAG composite microchip. Further power scaling possibility will be discussed.
High track density magneto-optical recording, using a crosstalk canceller which eliminates crosstalk from two adjacent tracks, has been developed. By this recording method, both land area and groove area can be used for data storage tracks, and twice the track density, cornpared with the conventional method, has been achieved. Applying this crosstalk canceller also realizes intersymbol interference compensation.
A digital video recording system using a four-beam magneto-optical disk drive has been developed. In order to realize continuous parallel read/write operation on an ordinary single-spiral disk, periodic single track jumping during one disk rotation has been employed. Digital video signal recording has been carried out on the entire disk.