Nonlinear Optical Crystals: A Complete Survey

We report type I phase‐matched blue second‐harmonic generation from periodically segmented channel ion‐exchanged waveguides in KTiOPO4 with output wavelengths from 0.38 to 0.48 μm and efficiencies exceeding 50%/W cm2. Evidence is presented suggesting that these efficiencies result from ferroelectric domain reversals induced by waveguide fabrication. Waveguide structure, wavelength, and output power characteristics are presented.

Efficient type I blue second‐harmonic generation in periodically segmented KTiOPO4 waveguides

Co1−xPtx alloys with Pt contents in the range 0.45≤x≤0.9 show sizable perpendicular magnetic anisotropy, 100% perpendicular remanence and coercivities in the range 160 kA/m. Thin films of this material are grown by electron beam evaporation onto fused silica or Si, at substrate temperatures between 150 and 350 °C. Spectroscopic investigations of the polar Kerr rotation show a significant enhancement of the Pt related UV peak. A comparison of the static signal levels R×(θk2+ek2)1/2 of Co/Pt multilayers and alloys shows an overall 50% enhancement in the case of alloys. Curie temperatures around 200 °C are observed for Co∼22Pt∼78 compositions. These properties, together with the potentially high chemical stability and ease of manufacturing make Co1−xPtx alloys very attractive materials for short wavelength magneto‐optic recording.

Magnetic and magneto‐optical properties of cobalt‐platinum alloys with perpendicular magnetic anisotropy

Surface-emitting semiconductor lasers can make use of external cavities and optical pumping techniques to achieve a combination of high continuous-wave output power and near-diffraction-limited beam quality that is not matched by any other type of semiconductor source. The ready access to the laser mode that the external cavity provides has been exploited for applications such as intra-cavity frequency doubling and passive mode-locking. The purpose of this Topical Review is to outline the operating principles of these versatile lasers and summarize the capabilities of devices that have been demonstrated so far. Particular attention is paid to the generation of near-transform-limited sub-picosecond pulses in passively mode-locked surface-emitting lasers, which are potentially of interest as compact sources of ultrashort pulses at high average power that can be operated readily at repetition rates of many gigahertz.

https://eprints.soton.ac.uk/15016/1/TropperJPD04.pdf

Vertical-external-cavity semiconductor lasers

Continuous-wave, room temperature laser oscillation at 491 nm, 520 nm, 605 nm and 635 nm in a Pr3+-doped fluoro-zirconate fibre pumped simultaneously at 1.01 µm and 0.835µm is reported. An output power of 185mW has been measured for the 635 nm transition. The thresholds obtained suggest that laser diode-pumped operation of all four transitions should be possible in an optimised fibre.

/pdf/cw-room-temperature-upconversion-lasing-at-blue-green-and-2586ih5o10.pdf

CW room temperature upconversion lasing at blue, green and red wavelengths in infrared-pumped Pr3+-doped fluoride fibre

A monolithic ring resonator of KNbO3 was used for efficient frequency doubling of a 856 nm GaAlAs diode laser. A special electronic servo technique was devised to lock the diode laser frequency to the KNbO3 cavity so that stable generation of blue output was obtained. With 105 mW of incident near‐infrared power, 41 mW of 428 nm radiation were produced. The conversion efficiency from electrical input power into the diode laser to blue output was ∼10%.

Generation of 41 mW of blue radiation by frequency doubling of a GaAlAs diode laser

A concept for full-wafer processing (FWP) and full-wafer testing (FWT) for semiconductor laser fabrication in the AlGaAs-GaAs material system is presented. The approach is based on chemically assisted ion beam etching for the laser-mirror formation. Record values for mirror scattering, optimum mirror reflectivity, and equivalence to cleaved mirrors in terms of laser threshold and efficiency have been achieved. Promising results for uniformity and reproducibility for major laser diode characteristics on processed 2-in wafers have been found. The FWP technology has been extensively used for designing test sites to determine various materials, process, and laser parameters, such as sheet resistance, ridge dimensions, lithographic alignment errors, mirror surface leakage, etc. >

Full-wafer technology-A new approach to large-scale laser fabrication and integration

The high‐power integrity of strained single quantum well InGaAs/AlGaAs lasers grown by molecular beam epitaxy is investigated. In the high‐power regime, the lifetime of the Lz=7 nm strained quantum well laser emitting at ≂ 980 nm is found to be limited by the air‐cleaved facets. However, a comparison with lattice‐matched 7 nm quantum well GaAs/AlGaAs lasers, which otherwise have an almost identical vertical structure shows a substantial lifetime improvement. This indicates that lattice hardening due to the indium in the quantum well is effective in the facet region. The investigations demonstrate the feasibility of 150 mW single mode operation with sufficient lifetime for practical applications in the wavelength range of ≂1 μm.

High-power operation of strained InGaAs/AlGaAs single quantum well lasers

The time dependence of catastrophic optical damage (COD) was studied for the cw operation of AlGaAs single quantum well lasers with cleaved mirrors. An empirical rule is proposed, which yields the time for a COD failure in the form of a rate equation, containing a frequency factor and an activation energy. In this way COD is explained as a thermally activated process, depending on the mirror temperature.

Thermodynamics approach to catastrophic optical mirror damage of AlGaAs single quantum well lasers

An experimental memory model for investigating the feasibility of a 16K RAM memory with Josephson junctions was fabricated and tested. There are nearly 4500 Josephson junctions in the design which includes array, line drivers, and address decoders. Storage element is a single flux-quantum (SFQ) cell arranged in a 2K array. Drivers and decoders are based on the principle of current steering in superconducting loops, which is a medium speed but low power approach. The measured read-access time of the model is approximately 10 ns. Power dissipation of the unselected chip is zero, whereas for a read/write cycle time of 30 ns, it amounts to about 10 /spl mu/W. Results indicate that a 16K chip is feasible electrically. The estimated access time and power dissipation are 15 ns and 40 /spl nu/W, respectively.

A. Moser

Papers

Generation of 41 mW of blue radiation by frequency doubling of a GaAlAs diode laser

Full-wafer technology-A new approach to large-scale laser fabrication and integration

High-power operation of strained InGaAs/AlGaAs single quantum well lasers

Thermodynamics approach to catastrophic optical mirror damage of AlGaAs single quantum well lasers

Model for a 15 ns 16K RAM with Josephson junctions