Dye laser pumped, continuous-wave KTP optical parametric oscillators

4 (KTP) optical parametric oscillators (OPOs) with pump and idler resonant cavities. With a linear two-mirror cavity the pump power at threshold was 70 mW. The single-frequency signal and idler output wavelengths were tuned in the range of 1025 to 1040 nm and 1250 to 1380 nm by tuning the dye laser in the range of 565 to 588 nm. With a dual three-mirror cavity the threshold was 135 mW. Pumped by 500 mW of 578 nm radiation the 1040 nm single-frequency signal wave output power was 84 mW. Power and frequency stable operation with a spectral bandwidth of less than 9 MHz was obtained by piezo-electrically locking the length of the pump resonant cavity to the dye laser wavelength. Similar performance was achieved by placing the idler resonant OPO inside the resonator of the dye laser. With this system power stable and single-frequency operation was achieved with a spectral bandwidth of less than 11 MHz for the idler wave. Received: 3 February 1998/Revised version: 9 March 1998     

Two-photon emission competing with cooperative and nonlinear processes

Stimulated non-degenerate two-photon emission from a pencil of lithium vapour is demonstrated on three decay cascades of the Li atom, namely accompanied with transitions from the 3s, 3d and 4s levels to the 2s level, upon pulsed two-photon excitation of the Li 4f and 4d levels. It competes with superfluorescence and parametric emission which show up at slightly shifted wavelengths. In the cascade via the 3d level, which is strongest under the experimental conditions, also two-photon Stokes scattering of the excitation light is identified.     

A deformation rig for synchrotron microtomography studies of geomaterials under conditions down to 10 km depth in the Earth

A hard X‐ray transparent triaxial deformation apparatus, called HADES, has been developed by Sanchez Technologies and installed on the microtomography beamline ID19 at the European Radiation Synchrotron Facility (ESRF). This rig can be used for time‐lapse microtomography studies of the deformation of porous solids (rocks, ceramics, metallic foams) at conditions of confining pressure to 100 MPa, axial stress to 200 MPa, temperature to 250°C, and controlled aqueous fluid flow. It is transparent to high‐energy X‐rays above 60 keV and can be used for in situ studies of coupled processes that involve deformation and chemical reactions. The rig can be installed at synchrotron radiation sources able to deliver a high‐flux polychromatic beam in the hard X‐ray range to acquire tomographic data sets with a voxel size in the range 0.7–6.5 µm in less than two minutes.     

The Industrial Research Program at the European Synchrotron Radiation Facility: The Past,the Present,and Challenges for the Future

The challenge of harnessing the power of third-generation synchrotron sources for industrial R&D has been taken up by the ESRF ever since the first users arrived in 1994. However, working with industry has its own special requirements, and often mismatches and clashes between a traditional scientific “ivory tower” culture and the needs of the market-driven commercial world. After more than 15 years of industrial research at the ESRF, during which strong industrial programs in protein crystallography and microtomography have been established, we continue to build bridges between the two worlds.     

High-efficiency mid-infrared ZnGeP2 optical parametric oscillator directly pumped by a lamp-pumped, Q-switched CrTmHo:YAG laser

We report a singly resonant optical parametric oscillator (SRO) based on a ZnGeP(2) crystal directly pumped by a lamp-pumped Q-switched CrTmHo:YAG laser. The IR was tunable from 4.7 to 7.8 microm via crystal angle tuning. A maximum optical to optical efficiency of 56% was obtained from the pump (2.09 microm) to total IR at a pump energy of 6.5 mJ. The corresponding idler energy was 1.45 mJ. The SRO was measured to have a slope efficiency of 64% and a threshold of 1 mJ. The spatial beam quality of the idler, characterized by the M(2) parameter, was 1.38 when the SRO was pumped at 2.5 times threshold. These results show that ZnGeP(2) optical parametric oscillators directly pumped by a CrTmHo:YAG laser can be operated efficiently, while maintaining good IR beam quality.     

A 180 mW Nd:LaSc3(BO3)4 single-frequency TEM00 microchip laser pumped by an injection-locked diode-laser array

A TEM₀₀ single-frequency, diode-pumped microchip laser of Nd(25%):LaSc₃(BO₃)₄ is operated with an output power of 180 mW. For best performance the laser was pumped by the 450 mW diffraction-limited single-frequency radiation of an injection-locked AlGaAs diode-laser array and cooled to the temperature of liquid nitrogen. The active and passive losses of the microchip laser were investigated by measuring the relaxation oscillation frequency and by comparing the experimental results with values obtained from appropriate rate equations. The power-dependent far-field pattern is in good agreement with the intensity distribution calculated by assuming a thermally induced waveguide cavity.     

Intensity noise of pump-enhanced continuous-wave optical parametric oscillators

4 (RTA), which provides a threshold pump power of 16 mW. The maximum signal wave power is 23 mW at a wavelength of 1243 nm. The spectral bandwidth of the signal wave is less than 750 kHz. Received: 3 February 1998