C. Ellmers

Ultrafast (GaIn)(NAs)/GaAs vertical-cavity surface-emitting laser for the 1.3 μm wavelength regime

(GaIn)(NAs) vertical-cavity surface-emitting lasers for room-temperature emission at 1.3 μm wavelength are designed and grown by metal-organic vapor-phase epitaxy using dimethylhydrazine and tertiarybutylarsine. Room-temperature operation at wavelengths up to 1.285 μm is achieved with low optical pumping thresholds between 1.6 and 2.0 kW/cm2. Stimulated emission dynamics after femtosecond optical pumping are measured and compare favorably with results on (GaIn)As/Ga(PAs)-based structures.

(GaIn)(NAs)/GaAs vertical-cavity surface-emitting laser with ultrabroad temperature operation range

The temperature dependence of the emission of a (GaIn)(NAs)/GaAs vertical-cavity surface-emitting laser is investigated. We find laser emission over an extremely broad temperature range from 30 K up to 388 K. The laser threshold varies from 5 kW/cm2 at 373 K down to a minimum of 1 kW/cm2 at 180 K and increases again to 4 kW/cm2 at 30 K. Picosecond emission dynamics after femtosecond optical excitation is obtained with peak delays below 33 ps and pulse widths below 20 ps over the entire operation range.

Emission dynamics and optical gain of 1.3-/spl mu/m (GaIn)(NAs)/GaAs lasers

The ultrafast emission dynamics of a 1.3-/spl mu/m (GaIn)(NAs)/GaAs vertical-cavity surface-emitting laser is studied by femtosecond luminescence upconversion. We obtain a minimum peak delay of 15.5 ps and a minimum pulse width of 10.5 ps. Laser operation with picosecond emission dynamics is demonstrated over a temperature range from 30 to 388 K. The bandgap shift with temperature of (GaIn)(NAs)/GaAs is determined to be about -2.9/spl middot/10/sup -4/ eV/K, which is smaller than for GaAs. Our measurements of the optical gain provide gain spectra similar to those of commercial (GaIn)(PAs)/InP-structures at moderate densities but broaden considerably for elevated carrier densities due to the stronger carrier confinement. We compare our experimental results with gain spectra calculated from a microscopic model and confirm the predictive capability of the model. The theoretical gain spectra are used as the input for a calculation of the temperature dependence of the (GaIn)(NAs)/GaAs surface-emitter emission which results in very good agreement with experiment.

Optically pumped (GaIn)As/Ga(PAs) vertical-cavity surface-emitting lasers with optimized dynamics

We present a vertical-cavity surface-emitting laser structure optimized for fast intrinsic emission dynamics, using the strain-compensated (GaIn)As/Ga(PAs) material system with a 2λ sin-type cavity. The high quality of the epitaxial growth is revealed by the large normal mode splitting of 10.5 meV found in reflectivity measurements. The fast dynamical response of our structure after femtosecond optical excitation at 30 K yields a pulse width of 3.2 ps and a peak delay of only 4.8 ps. A structure designed for laser emission at higher temperatures exhibits picosecond dynamics at room temperature.

Gain Spectra of an (InGa)As Single Quantum Well Laser Diode

A new method using the broad spectrum of a 10 fs Ti:sapphire laser is demonstrated for measuring the gain spectra of semiconductor lasers with high and quantitative accuracy. Results are shown for an edge-emitting ridge-waveguide In0.05Ga0.95As single quantum well (SQW) laser. The device is studied from the absorption regime up to the strong gain regime recording both, TE and TM polarizations. The experiments are compared to the predictions of a microscopic model based on the semiconductor Bloch equations including microscopic scattering and dephasing terms. A very good quantitative agreement is obtained.

Emission dynamics of (GaIn)(NAs)/GaAs lasers emitting at 1.3 μm

The emission dynamics of an optically pumped 1.3 +m (GaIn)(NAs)/GaAs vertical-cavity surface-emitting laser is investigated. We achieve room-temperature operation at 1285 nm with a low optical pumping threshold and fast emission dynamics: A minimum peak delay of 15.5 ps and a minimum pulse width of 10.5 ps are observed after excitation with 100 fs pulses. Laser operation with picosecond emission dynamics is demonstrated over a wide temperature range from 30 K to 388 K. We explain this extraordinarily large temperature operation range on the basis of measurements of the optical gain in (GaIn)(NAs)/GaAs. We find a gain broadening at elevated carrier densities due to contributions of higher subband transitions.

Emission Dynamics and Gain of (GaIn)(NAs)/GaAs Lasers

We find laser emission of a (GaIn)(NAs)/GaAs VCSEL with picosecond dynamics from 30 up to 388 K. The measured band-gap shift of (GaIn)(NAs) is comparatively small. Theoretically predicted gain spectra at high densities are broad. We conclude that the combination of both effects leads to the VCSEL operation in such a broad temperature regime.

Normal-Mode Linewidths in a Semiconductor Microcavity with Various Cavity Qualities

We measure the normal-mode linewidths in a semiconductor microcavity with various exciton–photon interaction strengths. Variation of the normal mode coupling and thus of the exciton–photon interaction is obtained reducing the cavity quality by stepwise removing of top mirror pairs. Excellent agreement of the measured linewidths with results of a linear dispersion theory is obtained.

Ultrafast dynamic response of strain-compensated (GaIn)As/Ga(PAs) microcavity lasers

Vertical-cavity surface-emitting lasers are optimized for fast intrinsic emission dynamics. The structure contains four times three quantum wells in a 2 (lambda) sin-type cavity. We have realized it using the strain-compensated (GaIn)As/Ga(PAs) material system with GaAs/AlAs Bragg mirrors. The laser emission after optical excitation with femtosecond pulses yields a pulse width of 3.2 ps and a peak delay of 4.8 ps to our knowledge the fastest values reported so far, at low temperatures. The design is successfully transferred to higher temperature operation. Picosecond dynamics is demonstrated also at room temperature with a pulse width of 13 ps and a peak delay of 9 ps. Laser operation over a broad temperature range from 140 K up to room temperature is achieved and also shows picosecond emission dynamics.

Pump geometry for resonant and quasi-resonant optical excitation of microcavity lasers.

A simple new pump geometry for optical excitation of microcavities and vertical-cavity surface-emitting lasers is presented. The technique circumvents the high reflectivity of the cavity stop band by excitation through the substrate at a large angle of incidence. Under these conditions, the reflectivity of the bottom Bragg reflector is small, and optical pumping at any desired photon energy becomes possible. Experimental results for optical excitation with this new geometry are compared with resonant optical pumping through the cavity mode.