H. M. Gibbs

Saturation of the free exciton resonance in GaAs

Abstract The transmission of 500 ns pulses through GaAs-AlGaAs heterostructures has been studied as a function of light intensity (0.015 to 50 kW/cm 2 ) and wavelength (810 to 840 nm). The intrinsic exciton absorption (λ=818 nm at 10°K) can be modeled by the sum of a small unsaturable background and a dominant term which saturates as a Bloch resonance with a saturatiom parameter of about 150 W/cm 2 .

Optical modulation by optical tuning of a cavity

A signal beam transmitted by a Fabry‐Perot cavity is modulated by a control beam which changes the refractive index of the intracavity medium. High finesse at the signal wavelength and strong absorption at the control wavelengths result in efficient optical gating and modulation. Such modulation has been observed using GaAs (and using color filters) with switch‐on times of 1 ns (10 μs) and switch‐off times of 2–20 ns (1 ms), and a physical length of only 5 μm (60 μm).

Optical Bistable Devices: The Basic Components Of All-Optical Systems?

Intrinsic optical bistability experiments are reviewed and their contributions summarized. Very large nonlinearities in semiconductors give reason to hope that practical devices may evolve in the near future. Characteristics important for practical optical logic devices are discussed: size, temperature range, holding intensity, switching energy, switching times, and wavelength range and stability.

Direct observation of fluorescence narrower than the natural linewidth

Abstract Forty-MHz-wide fluorescence has been seen using the 80-MHz-wide 2852 A transition of 24 Mg atoms in an atomic beam irradiated by a doubled cw dye laser.

Standing wave effects in optical bistability

Abstract The problem of optical bistability in a Fabry-Perot cavity is investigated in the limit α L , T → 0 including standing wave effects. In contrast to previous works, we find there are significant differences between the standing-wave and no-standingwave cases.

Laser Spectroscopic Measurement of the 87 Rb– 85 Rb D 1 -Line Isotope Shift

High-resolution (few MHz) absorption spectroscopy was demonstrated by using an atomic beam and a laser. The Doppler absorption width of natural-abundance Rb was reduced from ≈570 to 15 MHz (5.7-MHz natural width) by using an atomic beam. A magnetic field of about 75 kOe was used to scan the six 85Rb and four 87Rb mI components of the D1 line ( 52S12 to 52P12; 7947.64 A in zero field) into coincidence with the 7944.66-A 1-μs 202Hg ii laser pulses. From the known ground- and excited-state hyperfine constants and the Breit–Rabi formula, we conclude that the 87Rb absorption spectrum is shifted up by 77±3 MHz relative to that of 85Rb. This uncorrected isotope shift can be compared with previous measurements of 105±15 and 77.7±2.1 MHz. Improved stability and a narrower atomic beam would permit reduction of the isotope-shift and hyperfine-constant errors to below 1 MHz.

Ultrashort laser: Lasing in MBE GaAs layer with perpendicular-to-film optical excitation and emission

Lasing was observed in a 4.5 μm thick GaAs MBE-grown heterostructure (0.2 μm Al<inf>0.42</inf>Ga<inf>0.58</inf>As, 4.1 μm GaAs, 0.21 μm AlGaAs). The laser was driven by pulses from a mode-locked Ar laser (514.5 nm) with a maximum of 20 W peak power in 100 ps long pulses focused to 25 μm. The lasing occured along the pump axis within a cavity defined by the coated AlGaAs surfaces.

Production of 300W, nanosecond, transform limited optical pulses

Abstract Intense nanosecond pulses have been produced from a cw dye laser using a dye amplifier pumped by 6 ns nitrogen laser pulses. The pulses have a transform limited spectrum and are convenient for coherent propagation experiments.

Faraday rotation under cw saturation and self-induced transparency conditions

Abstract Faraday rotation angles in excess of 180° were observed in Na vapor in a 1 kOe magnetic field with intensity transmissions greater than 80%. Identical angles were seen in both the cw saturation (SAT) and self-induced transparency (SIT) limits. This agrees with the theoretical expectation that when the absorption linewidth is large compared with the saturation hole or inverse pulse width, the linear, SAT, and SIT angles are equal.

Optical Bistability in a GaAs Etalon

The first observation of optical bistability in a passive semiconductor etalon is reviewed. The bistable etalon consists of a GaA1As-GaAs-GaA1As molecular-beam epitaxially-grown sandwich with 90% reflectivity coatings. The bistability is primarily dispersive with the nonlinear refractive index arising from light-induced changes in exciton absorption. Using light of frequency just below the exciton peak, we observed bistability from 5 to 120°K. The holding intensity was about 1 mW/μm2, and switching times of < 1 ns turn-on and 40 ns turn-off have been achieved. This device illustrates the use of a material resonance and optical cavity to reduce the holding intensity and switching energy. Further reductions are anticipated by further miniaturization and device development. The possibility of utilizing bistable devices in high-speed optical processing and computing motivates the development of these semiconductor etalons.