C. J. van der Poel

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

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.

Balanced phase matching in segmented KTiOPO4 waveguides

A new phase matching technique is described which is based on phase mismatch balancing in crystal or waveguide segments that are short compared to their respective coherence lengths. The technique is demonstrated experimentally in a mixed bulk crystal/waveguide structure in KTiOPO4, resulting in a second‐harmonic generation conversion efficiency of 15%/W/cm2 at 1.064 μm, close to the theoretical maximum. We show that this technique can significantly broaden processing latitude for fabricating practical nonlinear optical waveguide devices.

DIODE-PUMPED CR:LISAF ALL-SOLID-STATE FEMTOSECOND OSCILLATOR AND REGENERATIVE AMPLIFIER

An all-solid-state tunable diode-pumped Cr3+:LiSrAlF 6 (Cr:LiSAF) regenerative amplifier, seeded by a tunable diode-pumped Cr:LiSAF femtosecond oscillator, has been demonstrated for the first time to our knowledge. The oscillator was tunable over 75 nm and generated pulses as short as 24 fs. As much as 70 mW average output power was obtained with pulses of 40-fs duration. The amplifier produced recompressed pulses of less than 200-fs duration with energies exceeding 1 μJ at a repetition rate as high as 25 kHz.

Kink power in weakly index guided semiconductor lasers

A periodic dependence of kink power on laser length is observed and explained. Weakly index guided high power stripe lasers in the AlGaAs, InGaAlP, and InGaAs–AlGaAs material systems are studied and oscillation periods of 100–350 μm are found. Relative kink power differences exceeding a factor of 4 are observed. Facet coatings lead to differences in the oscillation amplitude but not in the oscillation period. The observations indicate that phase‐locked fundamental and first‐order modes exist at certain preferred laser lengths. This general model fully explains the oscillatory behavior of the kink power and the correlated changes in lateral far field distributions at the front and rear mirrors. It is concluded that the optimum diffraction limited power output can be obtained by choosing the proper laser length.

Improved performance of compressively as well as tensile strained quantum‐well lasers

The results of a theoretical study together with an experimental verification of the effects of strain on the laser characteristics of InxGa1−xAs/InGaAsP quantum‐well lasers are reported. It is shown that tensile strained quantum‐well lasers can perform as well as compressively strained lasers with respect to the threshold current density. Both show an improved performance when compared to the unstrained case. The origin of this improved performance is discussed.

Effect of strain on the threshold current of GaInP/AlGaInP quantum well lasers emitting at 633 nm

For the first time the performance of visible lasers operating at 633 nm is reported as function of the amount of applied strain. Varying the strain between /spl delta/a/a = -1 % and /spl delta/a/a = + 1 % two minima in threshold current density have been found and are explained.

Phase‐change optical recording in TeSeSb alloys

Some characteristics of reversible phase‐change optical data storage in TeSeSb alloys are given. High signal‐to‐noise ratios are reached at low recording energies. Upon passage of an oblong scanning laser spot, erasure occurs by growth from the crystalline surroundings of the amorphous effects at growth velocities of up to 5 cm/s. Isothermal transformation appears to be dominated by phase separation and diffusion processes. The tradeoff between long‐term stability and erasure time varies with alloy composition and, for some alloys, attractive properties with respect to data retention and erasure times are found.

Phase-change optical data storage in GaSb.

The amorphous to crystalline transition in the semiconductor GaSb has been studied as a recording mechanism for write-once optical storage. Amorphous as-deposited films, 100 nm thick, are transformed locally to the crystalline state by a focused laser beam. This recording process can be accomplished within 10 ns. The dimensions of the crystalline marks can be accurately controlled. Optical storage media based on GaSb are suitable for the archival storage of information modulated according to the compact disk format.

Strained layer GaAs1−yPy‐AlGaAs and InxGa1−xAs‐AlGaAs quantum well diode lasers

Separate confinement strained layer single quantum well diode lasers on GaAs substrates have been fabricated by low‐pressure organometallic vapor phase epitaxy. Laser diode structures with a 90 A quantum well under compressive strain, composed of InxGa1−xAs with x=0.00–0.17, as well as tensile strain, composed of GaAs1−yPy with y=0.00–0.29, have been studied. The emission wavelength ranges from λ=746 nm for y=0.29 up to λ=962 nm for x=0.17. The strain dependence of the threshold current for broad area devices is studied both experimentally and theoretically as a function of temperature. Regions of optimal laser performance, one for compressive and one for tensile strain, are identified.

Argon-ion-pumped and diode-pumped all-solid-state femtosecond Cr:LiSrAlF(6) regenerative amplifiers.

A tunable femtosecond solid-state amplifier system that uses only 3 W of 488-nm argon-ion pump power has been demonstrated to deliver microjoule pulses at repetition rates up to 20 kHz, with a maximum pulse energy of 14 mu;J obtained at 5 kHz. An all-solid-state, tunable, diode-pumped Cr:LiSrAlF(6) regenerative amplifier has been demonstrated, for the first time to our knowledge, that amplifies femtosecond pulses to energies exceeding 1 mu;mJ at up to a 16-kHz repetition rate.