Excitability in a quantum dot semiconductor laser with optical injection.

We experimentally analyze the dynamics of a quantum dot semiconductor laser operating under optical injection. We observe the appearance of single- and double-pulse excitability at one boundary of the locking region. Theoretical considerations show that these pulses are related to a saddle-node bifurcation on a limit cycle as in the Adler equation. The double pulses are related to a period-doubling bifurcation and occur on the same homoclinic curve as the single pulses.

Efficient frequency doubling of a vertical-extended-cavity surface-emitting laser diode by use of a periodically poled KTP crystal.

Blue light with a cw power in excess of 42 mW is generated from a frequency-doubled, extended-cavity InGaAs/GaAs 980-nm surface-emitting laser by use of a periodically poled KTP crystal.

Experimental observation of traveling waves in the transverse section of a laser.

The selection of a transverse traveling wave by an inhomogeneous pump profile has been experimentally observed in a class B laser structure. The laser structure consisted of a wide-aperture edge-emitting laser diode operating in pulsed mode to avoid thermal guiding effects. The injection current's profile was modified from the usual top-hat configuration to a Lorentzian-like profile by the inclusion of a 10-mum p-type expitaxial spreading layer. Spatial dependance of the far field on the near field was observed. The same behavior is also demonstrated numerically by use of Maxwell-Bloch equations for semiconductor lasers.

193 nm photolysis of aromatic and aliphatic dipeptides in aqueous solution: dependence of decomposition quantum yield on the amino acid sequence.

The values of molar absorption coefficient and quantum yields of photodecomposition and peptide bond scission were determined for a number of aromatic and aliphatic dipeptides under 193 nm laser irradiation in neutral argon-saturated aqueous solution. Under these conditions we could show that no dependence of the dipeptide decomposition quantum yield on the sequence of amino acid residues exists, neither for aromatic dipeptides nor for aliphatic ones.

Analysis of the fast recovery dynamics of a semiconductor laser with feedback in the low-frequency fluctuation regime.

We experimentally investigate the temporal evolution of the power of an external cavity semiconductor laser in the low-frequency fluctuation regime with subnanosecond resolution. We show, for the first time to our knowledge, that generally the laser power drops to a value significantly different from the solitary laser power. We demonstrate the analogy between the recovery of the laser intensity and the turn-on transient of a semiconductor laser.

Effects of the injection current profile shape on sidelobes in large-aperture semiconductor laser amplifiers.

Sharply peaked near-field sidelobes are formed when the input optical field pattern interacts with the edges of the current stripe in a semiconductor laser amplifier. The strength of this interaction is shown theoretically to depend principally on the first and second derivatives of the transverse current profile, and hence one can suppress the sidelobes by smoothing the sharp edges in the current injection.

Near field wavefront measurements of semiconductor laser arrays by shearing interferometry.

A reliable technique for measuring near field phase fronts of phased-array semiconductor lasers is proposed and demonstrated. Laterally sheared interferograms are generated in a ring-type interferometer with zero optical path difference between two beams, eliminating problems due to equal optical path requirements in other systems. Fourier transform methods are used to extract phase difference information from the nonuniformly illuminated interferograms, and phase discontinuities between adjacent stripes of carrierguided laser arrays are observed. Test data agree with theoretical predictions and far field interpretations.

Low-frequency self-pulsations in asymmetric external-cavity semiconductor lasers due to multiple-feedback effects.

We investigate the dynamical stability of external-cavity semiconductor lasers with deliberate tilt asymmetries. Experimentally observed low-frequency self-pulsations are explained by small-signal analysis based on a new rateequation model that uses a time-dependent effective reflectivity to include multiple-feedback effects. We observe and explain the dependence of the self-pulsation frequency on the strength and degree of asymmetry of the feedback, on the injection current, and on the external-cavity length. These results are important in interpreting instabilities, chaos, and other complex dynamical phenomena in external-cavity semiconductor lasers.