High-power electroabsorption modulator using intra-step-barrier quantum wells

Abstract

We propose an efficient high-optical-saturation-power electroabsorption modulator (EAM) using intra-step-barrier quantum wells (IQWs) incorporating a step-barrier inside the well for both the conduction and the valence bands. From the simulation, we show that in the IQW (a) the onset of the redshift of the quantum-confined Stark effect is delayed to a higher electric field; and after the onset, (b) the transition energy and the oscillator strength respond sharply to the electric field. As the screening effect by the photogenerated carriers is reduced at the higher electric field, the optical saturation effect in the IQWs can be significantly reduced. Due to the higher optical power handling capability and better modulation efficiency, the EAM with IQWs is expected to substantially improve the fiber link performance.

Design of a novel periodic asymmetric intra-step-barrier coupled double strained quantum well electroabsorption modulator at 1.55μm

“…It has also been reported that the strain-compensated InGaAsP/InGaAsP [4] and InAsP/GaInP [5], which have shallow wells, improves the saturation optical power at 1.3 and 1.55 lm, respectively. Recently, the use of an asymmetric QW with a step barrier to achieve high-optical-power operation has been proposed [6,7]. The intra-step quantum well (IQW) was shown to delay the onset of the red shift of the QCSE to a higher electric field, when the electric field was applied from the well to the step barrier.…”

High-Power Intrastep Quantum Well Electroabsorption Modulator Using Single-Sided Large Optical Cavity Waveguide

“…2. The slight blue shift at low field is characteristic of IQW [2], [6]. At field 60 kV/cm, the QCSE becomes dominant and the exciton resonance is redshifted and broadened.…”

“…For EAM with unmatched electrode, a factor of 4 is typically incorporated in (1) to account for the voltage enhancement caused by the microwave reflection. The equivalent is defined as (2) where is the slope efficiency of normalized EAM transfer curve. Thus, the higher the slope efficiency, the smaller is.…”

“…The basic approaches to obtain a high link gain in an externally modulated link are to have low insertion loss, high optical power handling, and high slope efficiency at the modulator. We have previously proposed to use the intrastep quantum well (IQW) to increase the biasing electric field at the electroabsorption region for sweeping out carriers at high optical power [2]. The IQW has the additional merit of large quantum confined Stark effect (QCSE) [3]- [5], which implies small drive voltage.…”

Gain–bandwidth relation of electroabsorption-modulated analogue fibre link: effect of photocurrent resistance

“…As the optical power driving the analogue fibre link has been increased to achieve higher radio-frequency (RF) gain, the operation of the EAM under high optical power has been studied and designs that enable the high-optical-power operation have been suggested. By combining the diluted waveguide that absorbs much reduced optical power per unit length and the modified quantum-well design [6][7][8], an EAM has been demonstrated to handle a very high optical power up to 25 dBm ( 320 mW) [9].Under this very high optical power, however, the analogue fibre link that utilises an EAM has been shown to have saturation in RF gain owing to the photocurrent resistance inherent in the EAM device [9][10][11][12]. The photocurrent resistance R ph is given by (dI ph /dV ) 21 , where I ph is the photocurrent generated in the EAM and V is the reverse bias voltage supplied to the device.…”