C.A. Burrus

The quantum well self-electrooptic effect device: Optoelectronic bistability and oscillation, and self-linearized modulation

We report extended experimental and theoretical results for the quantum well self-electrooptic effect devices. Four modes of operation are demonstrated: 1) optical bistability, 2) electrical bistability, 3) simultaneous optical and electronic self-oscillation, and 4) self-linearized modulation and optical level shifting. All of these can be observed at room-temperature with a CW laser diode as the light source. Bistability can be observed with 18 nW of incident power, or with 30 ns switching time at 1.6 mW with a reciprocal relation between switching power and speed. We also now report bistability with low electrical bias voltages (e.g., 2 V) using a constant current load. Negative resistance self-oscillation is observed with an inductive load; this imposes a self-modulation on the transmitted optical beam. With current bias, self-linearized modulation is obtained, with absorbed optical power linearly proportional to current. This is extended to demonstrate light-by-light modulation and incoherent-to-incoherent conversion using a separate photodiode. The nature of the optoelectronic feedback underlying the operation of the devices is discussed, and the physical mechanisms which give rise to the very low optical switching energy (∼4 fJ/ μm2) are discussed.

Novel hybrid optically bistable switch: The quantum well self‐electro‐optic effect device

We report a new type of optoelectronic device, a self‐electro‐optic effect device (SEED), which uses the same GaAs/GaAlAs multiple quantum well material simultaneously as an optical detector and modulator. Using a series resistor and constant voltage bias supply the SEED shows optical bistabilty (OB) of the recently discovered type which relies on increasing absorption and requires no mirrors. OB is seen at room temperature from ∼850–860 nm, at powers as low as 670 nW or switching times as short as 400 ns (limited only by power restrictions) with ∼1‐nJ optical switching energy in a 600‐μm‐diam device. Total energies per unit area (∼18 fJ/μm2) are substantially lower than any previously reported for OB.

Ultrawide-band long-wavelength p-i-n photodetectors

We compare different designs for very high-speed (millimeter-wave) long-wavelength photodetectors, different materials for such detectors, and different ways of characterizing the speed of these devices. Experimental results are given, showing high-speed response with bandwidths beyond 50 GHz, impulse responses less than 10 ps, and detection sensitivities to 0.1 fJ in packaged devices. Discussed is the inherent bandwidth-efficiency limit in conventional p-i-n detectors, which is then compared to theoretical and experimental results for waveguide-geometry detectors.

Neodymium‐doped silica lasers in end‐pumped fiber geometry

Fused SiO2 has been used as a new noncrystalline host for the fabrication of two types of neodymium‐doped room‐temperature lasers, one of which operates at 1.06‐μm and the other at 1.08‐μm wavelength. The lasers have the geometry of clad optical fibers, with active cores as small as 15‐μm diameter by 1‐cm length. They are end pumped at 0.590 and 0.5145 μm with a pulsed dye laser and an argon ion laser, respectively. Thresholds as low as 1–2 mW of absorbed pump power in a 40‐μm‐diam core have been obtained, and eventual pumping with high‐radiance semiconductor optical sources appears feasible.

Short-cavity InGaAsP injection lasers: Dependence of mode spectra and single-longitudinal-mode power on cavity length

Simple expressions are given to describe the lower and upper limits of the single-mode (single-frequency) power as a function of the cavity length for InGaAsP injection lasers. It has been found that the lower limit of the single-mode power is proportional to the cavity length, while the upper limit is inversely proportional to the cavity length. Thus, a short-cavity laser provides a favorable geometry for obtaining single mode output over a wide range of power levels and currents above threshold. The mode stability versus temperature is also improved by a short-cavity design. The theoretical results agree with our recent experiments on very-short-cavity ( 50-75 \mu m) stripe-geometry InGaAsP lasers, which have shown consistent single-mode output over wide current ranges.

Acceleration of gain recovery in semiconductor optical amplifiers by optical injection near transparency wavelength

By using optical injection near the transparency wavelength of semiconductor optical amplifiers, we show experimentally that both the saturation output power and the gain recovery can be greatly improved. By injecting 80 mW of pump power, we observe a 3-dB increase in saturation output power. For 73 mW of pump power, we find a reduction in gain recovery time from over 200 ps down to below 40 ps, while maintaining 14 dB of fiber-to-fiber gain at 1555-nm wavelength.

131 ps optical modulation in semiconductor multiple quantum wells (MQW's)

A new optical modulator has been fabricated which uses the recently discovered electroabsorption effect in MQWs. Optical pulses 131 ps long were generated when the device was driven with 122 ps electrical pulses. The input-output characteristics of the device show that it has low insertion loss with reasonable modulation depth and drive voltage.

Highly anisotropic optical properties of single quantum well waveguides

The first measurements of the linear and nonlinear anisotropic absorption of light propagating along the plane of a single quantum well are reported and discussed in terms of the structure of the valence band in ultrathin semiconductor layers. Nonlinear optical effects are compared to those of multiple layer structures and to recent theory.

Electro‐optic phase modulation in GaAs/AlGaAs quantum well waveguides

We present the first absolute measurements of the electric‐field‐induced refractive index change in GaAs/AlGaAs quantum well waveguides. Phase and intensity modulation are characterized as a function of wavelength both above and below the n=1 exciton resonances.

Strong polarization‐sensitive electroabsorption in GaAs/AlGaAs quantum well waveguides

We report the first measurements of perpendicular field electroabsorption (quantum confined Stark effect) in GaAs/AlGaAs quantum wells for light propagating parallel to the plane of the layers. This geometry is well suited for integrated optics. The absorption edge shifts to longer wavelengths with increasing field by as much as 40 meV, giving a modulation depth>10 dB. The strong dichroism present in this geometry is retained even at high fields, making polarization‐sensitive electro‐optical devices possible. We also demonstrate in the waveguide geometry optical bistability due to the self‐electro‐optic effect with 20:1 on/off ratio.