Ulf Öhlander

Influence of absorber length on inhomogenously pumped, bistable semiconductor lasers

We report on experiments with inhomogenously pumped semiconductor lasers of InGaAsP (1300 nm) having a saturable absorber. Bistability disappears for long relative length of the absorber, and lasing occurs for wavelengths considerably longer than the luminescence peak. Both these results are very important for designing bistable lasers and are consistent with recently published theoretical data.

Bistable operation of InGaAsP lasers using different absorber positions

Experiments reveal that the physical characteristics related to absorptive bistability, such as lasing threshold, hysteresis width, and carrier redistribution, are greatly altered when the absorber position is changed from the middle section to one of the end‐facet sections in a three‐section laser diode.

Subnanosecond switching of bistable tandem lasers by subpicojoule optical triggering

We report on the switching‐on characteristics of a bistable two‐section laser diode triggered by subnanosecond optical input pulses. Minimum switching energy as a function of current bias level was measured for different input pulse wavelengths. Subnanosecond and subpicojoule switching was obtained. Estimating the input coupling to be 10%, the lowest bistable switching energy recorded was 23 fJ. The fastest recorded rise time was less than 100 ps.

Polarization‐independent optical switching of an inhomogeneously pumped laser diode

The polarization dependence of the optical input energy required to switch an inhomogeneously pumped bistable laser diode is studied at various input signal wavelengths. Polarization‐independent switching is achieved for input pulse wavelengths 30–40 nm shorter than the lasing wavelength of the bistable laser diode, whereas input pulse wavelengths close to the lasing wavelength result in a strong polarization dependence. A simple theory explains the observed behavior.

Cavity-length dependence of quantum-well lasers with different strain

Previously, strain has shown to reduce the threshold current density for long cavity semiconductor lasers. However, also important is the cavity length for which the threshold current has a minimum. We find that for a given well width, an increase of the indium ratio from the lattice-matched value substantially reduces this optimum cavity length. We attribute this to the combined effects of strain on the valence bands and an increase in the confinement of the conduction band electrons to the well.

Bistability In Semiconductor Etalons And Lasers

Advances in the area of bistable semiconductor etalons and inhomogeneously pumped laser diodes are reviewed. Results concerning a novel method to fabricate thin AlGaAs etalons that can be thermally stable for 0.5 seconds is presented. The method is based on results from a rigorous numerical model for the temperature rise. Furthermore, results from optical triggering of multisection InGaAsP lasers at 500 MHz repetition rate with less than 1 fJ optical switching energy are reported.