Olof Sahlén

Optical bistability and gating in metalorganic vapor phase epitaxy grown GaAs étalons operating in reflection

Nonlinear Fabry–Perot etalons of GaAs have been fabricated with metalorganic vapor phase epitaxy technology. The etalons operate in reflection mode, and have an epitaxially grown, rear dielectric mirror consisting of a stack of alternating AlAs/GaAlAs layers. Optical logic functions using a HeNe laser and optical bistability at room temperature are reported. Low switching powers and improved etalon uniformity are obtained.

LOW-POWER OPTICAL BISTABILITY IN A THERMALLY STABLE ALGAAS ETALON

Optical bistability with 10 mW input power is reported in a thermally stable, nonlinear AlGaAs etalon. A 3‐μm‐thick silver layer, which serves both as high‐reflecting mirror and heat sink, makes it possible to operate the device at arbitrary duty cycles and pulse lengths up to 0.5 s, without any regenerative pulsations, at room temperature. The device operation depends on the plasma‐induced electronic nonlinearity, and switching times are typically 10 ns. Device performance is compared with results from a numerical model which takes diffraction, diffusion, and heat conduction into account.

Transverse effects in switching of bistable Fabry–Perot etalons filled with a saturable medium

A systematic variation of the Fresnel number has been performed when solving the nonlinear wave equation for a Fabry–Perot etalon filled with a saturable medium and including unsaturable background absorption. We show that the optimum Fresnel number for absorptive and defocusing bistability in media such as CdS, using the nonlinearity due to the bound exciton resonance, can be considerably greater than one and that bistability is completely lost for tight focusing.

Switching power dependence on spot size in bistable ZnS etalons

Abstract The power required to switch bistable etalons with ZnS as the nonlinear medium is experimentally demonstrated to depend linearly on spot radius also for small radii. The nonlinear heat conduction equation is solved numerically, allowing a position-dependent heat conductivity to be used. Fair agreement between theory and experiments is achieved.

Bistable switching in nonlinear Al0.06Ga0.94As étalons

Optical bistability at 5 mW input power at 840 nm is reported in Al0.06Ga0.94As etalons grown by metalorganic vapor phase epitaxy, having an epitaxially grown high‐reflecting back mirror. The devices have been switched from the high‐reflecting to the low‐reflecting state with pulses from a laser diode operating at 778 nm with 10 pJ switching energy. The devices could be thermally stable for as long as 200 μs. The experimental results are compared with a simple theoretical model.

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.

Optical bistability in thin-film CdSe interference filters

Nonlinear, thin-film interference filters with CdSe as spacer material have been fabricated. Optical bistability is observed with less than 3 mW of optical power with wavelengths in the 810–850-nm region. The nonlinear mechanism is shown to be thermal. Filters having thicker CdSe spacers are more stable than filters with very thin spacers.

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.

Theory for the temperature rise in optically bistable GaAs/AlGaAs étalons including diffraction, heat conduction, and carrier diffusion

We report on a realistic model for optically bistable GaAs/AlGaAs Fabry-Perot étalons. The model incorporates diffraction, carrier diffusion, and heat conduction, taking all the layers of the structure into account. For the optical nonlinearity the carrier density and temperature-dependent plasma theory is used. Devices with less than a 1-K temperature rise should be possible to design.