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We demonstrate a reflection electroabsorption modulator grown on a GaAs substrate operating near 1.3 μm, the dispersion minimum for silica fibers. The device was grown by molecular beam epitaxy and uses a novel technique of integrating the bottom quarter‐wave mirror into a buffer with linearly graded In composition. The active area consisted of thirty InGaAs quantum wells with GaAs barriers. The mirror was formed by layers of InGaAs and InAlAs where the In concentration was graded from 0% to 35%. A maximum relative change in reflectivity, ΔR/R, of 73% at 1.33 μm was achieved. Experimental results agree with simulations performed using the transfer matrix technique.

By analyzing the exciton line shapes of quantum wells, we can determine the wavelengths and biases at which they exhibit large absorption changes and zero refractive index changes relative to zero bias. To use this effect, we placed GaAs/AlGaAs quantum wells in the intrinsic region of a reverse‐biased p‐i‐n diode asymmetric Fabry–Perot modulator. We then developed a sample that could be post‐growth processed to optimize all relevant parameters. We used computer simulation to determine the exact post‐growth correction required and produced reflection modulators with 90% reflection change and zero relative phase change.

We report the first observation of intersubband transitions in InyGa1−yAs(y=0.3,0.5)/ AlGaAs quantum wells. These quantum wells were grown on a GaAs substrate with a linearly graded InGaAs buffer to achieve strain relaxation before growth of the quantum wells. Measured intersubband transition energies of 316 and 350 meV are among the largest ever reported. Asymmetric step In0.5Ga0.5As/AlGaAs quantum wells designed for second harmonic generation measurements also demonstrate strong intersubband absorption at 224 meV corresponding to the 1‐2 transition. With the large conduction band offsets (larger than 800 meV) available in this material system, extension to larger intersubband transitions energies for quantum well photodetector and nonlinear optics applications should be possible.

The influence of refractive index changes on the phase characteristics of a reflection Fabry–Perot quantum well modulator is discussed and compared with experiment. Although a Fabry–Perot cavity can reduce the effective chirp near resonance, the phase change is highly nonlinear and critically dependent on the wavelength.

We demonstrate a novel approach to the molecular beam epitaxial (MBE) growth of vertical Fabry–Perot cavities with quarter‐wave mirrors. At two selected points, the growth is interrupted and the reflectivity spectrum is measured without removing the wafer from the vacuum system. Corrections are then made in the growth of subsequent layers. By making measurements on the incomplete structure, separate corrections can be made to center both the mirror reflectivity and the cavity resonance at the desired wavelength. We present theoretical and experimental data demonstrating the effectiveness of the approach, and estimate the effects on device performance.

We demonstrate both theoretically and experimentally that the quantum‐confined Stark effect leads to larger absorption changes in GaAs/AlAs quantum wells compared to the more conventional GaAs/AlGaAs system due to the higher Γ confinement. The lower indirect valleys in AlAs do not degrade the performance and the exciton resonance is maintained at higher‐energy shifts. The improvement in exciton oscillator strength is nearly 50% with a 70‐meV shift. The greater exciton strength at high fields has important applications for optical modulators and switches that operate at the long‐wavelength side of the zero‐bias exciton.

Theoretical and experimental work shows that electroabsorption improves and the quantum‐confined Stark effect becomes stronger in In0.2Ga0.8As/AlxGa1−xAs quantum wells as the aluminum concentration (x) is increased in the barriers. This improved electroabsorption was used in a reflection modulator that exhibited the largest reported reflectivity change of 77%.