S. D. Smith

Optical bistability and signal amplification in a semiconductor crystal: applications of new low‐power nonlinear effects in InSb

We report the observation of optical stability for a plane parallel semiconductor crystal which forms a Fabry‐Perot interferometer using only the natural reflectivity of its surfaces. Nonlinear transmission is observed for cw laser intensities above ∼ 100 W/cm2 for radiation at 1895 cm−1 near the energy gap of InSb at 5 K. The effect is interpreted in terms of a very large intensity‐dependent refractive index giving a 5λ/2 optical thickness change for an intensity of ∼2 kW/cm2. Clear bistability is seen in fifth‐order interference, the first such observation above first order in an intrinsic, one‐element system, in addition to regions exhibiting signal amplification. The same crystal also shows strong modulation of the transmission of one laser beam induced by a second, with real signal gain, thus demonstrating an ’’optical transistor.’’

Electron-beam-tunable interference filter spatial light modulator

A new type of electron-beam-addressed spatial light modulator has been demonstrated. It is based on the local tuning of an optothermal nonlinear interference filter by the scanned electron beam. Such an e-beam-tunable interference filter device should find applications in both display technology and optical data processing.

Room temperature, visible wavelength optical bistability in ZnSe interference filters

Abstract The observation of milliwatt-power optical bistability at room-temperature in interference filters based on ZnSe spacers is reported. Switching times of a few milliseconds have been achieved using 514 nm wavelength radiation at an irradiance of ∼250 W cm -2 . The device has been operated in a steady-state manner and switched between the two stable states by an external beam.

Optical bistability, photonic logic, and optical computation

This paper presents new results and reviews the latest state of research in all-optical nonlinear logic switches, amplifiers, and memories. Optical circuit elements that perform the logic functions of the electronic computer are described. Switching speed on a picosecond time scale, the availability of fast high bandwidth consistent communication, and the application of optical parallelism in free space optical wiring are some advantages of the optical computing elements.

Nonlinear Optical Circuit Elements As Logic Gates For Optical Computers: The First Digital Optical Circuits

The first digital all-optical circuits based on intrinsic bistable devices have now been realized. Experimental results with two systems, InSb etalons and nonlinear interference filters containing ZnSe, are presented and discussed. These results indicate that a digital optical processor incorporating devices of this type would appear to be feasible.

Optical bistability in InSb at room temperature with two‐photon excitation

We report the observation of optical bistability in an InSb resonator at room temperature. This effect and fringe shifts were caused by nonlinear refraction induced by two‐photon absorption of radiation from a single longitudinal mode injection‐locked pulsed CO2 laser operating at 9.6–10.6 μm. Intensities as low as 100 kW/cm2 were found to be sufficient to tune the 250‐μm‐thick cavity through a fringe maximum. From our results we deduce a value of χ(3) of the order of 10−4 esu over the range of intensities investigated.

Optical bistability in bulk ZnSe due to increasing absorption and self‐focusing

We report the first observation of cavityless optical bistability in ZnSe. A shift in the band edge and self‐focusing occurs due to the temperature rise of the material as the laser irradiance is increased. These two mechanisms are believed to provide the feedback necessary for bistable operation.

Realization of an InSb bistable device as an optical and gate and its use to measure carrier recombination times

We report the novel operation of a natural reflectivity InSb bistable resonator at 77 K, pumped with a cw CO laser at 1819 cm−1, as a single pulse detector with definite threshold energy and as an optical AND gate. The two switching pulses for the AND gate logic operation are 30‐ps single, switched‐out pulses from a mode‐locked neodymium: yttrium aluminum garnet (Nd:YAG) laser. Introduction of a variable time delay between the logic pulses provides a unique technique for measurement of the photogenerated carrier lifetime and yields a recombination time ∼90 ns for a cw CO holding intensity ∼80 W/cm2.

Absorption switching and bistability in InSb

Abstract For a temperature-dependent absorption appropriate to a thermally shifting semiconductor band-edge at low temperatures, or to a broadening Urbach tail at high temperatures, the criteria for pure absorptive bistability are shown to be (i) α0L 2.7 T0. L is the sample thickness, α0 the initial absorption coefficient, A is a thermal constant, T0 is the temperature coefficient of the absorption and I0 is the incident irradiance. Observation of absorption switching and of purely absorptive bistability under such conditions is reported for InSb near 77 K.

High gain signal amplification in an InSb transphasor at 77 K

We present experimental observations of the variations of the input‐output characteristic of a nonlinear Fabry–Perot resonator as a function of initial detuning. The characteristics include regions with various differential gains, or show hysteresis with the width of the bistable region being variable. Operating the device as a transphasor (optical transistor), a signal of 3 μW can be amplified with a signal power gain of up to 104 with the device operating at 77 K and 1819 cm−1.