Abstract
We propose and demonstrate a new electro-absorption modulator (EAM) based on coupled tandem cavities (CTC) having asymmetric tandem quantum well (ATQW) structure with separated electrode configuration to achieve large transmittance change over a broad spectral range at low driving voltage for high definition (HD) 3D imaging applications. Our theoretical calculations show that CTC with ATQW structure can provide large transmittance change over a wide spectral range at low driving voltage. By introducing separated electrode configuration, the fabricated EAM having CTC with ATQW structure shows a large transmittance change over 50%, almost three times larger spectral bandwidth compared to that of EAM having single cavity with a single thickness quantum well without significantly increasing the applied voltage. In addition, the CTC with ATQW structure also shows high speed modulation up to 28 MHz for the device having a large area of 2 mm x 0.5 mm. This high transmittance change, large spectral bandwidth and low voltage operation over a large device area for the EAM having CTC with ATQW demonstrates their huge potential as an optical image modulator for HD 3D imaging applications.
Highlights
Quantum-confined Stark effect (QCSE) [1] based large area surface normal electroabsorption modulators (EAM) using GaAs/AlxGa1-xAs material operating at 850nm are attractive for high definition (HD) three dimensional (3D) imaging applications [2,3,4,5]
By introducing separated electrode configuration, the fabricated electro-absorption modulator (EAM) having coupled tandem cavities (CTC) with asymmetric tandem quantum well (ATQW) structure shows a large transmittance change over 50%, almost three times larger spectral bandwidth compared to that of EAM having single cavity with a single thickness quantum well without significantly increasing the applied voltage
We propose and demonstrate a new electro-absorption modulator (EAM) based on coupled tandem cavities (CTC) having asymmetric tandem quantum well (ATQW) structure with separated electrode configuration to achieve large transmittance change over a broad spectral range at low driving voltage for high definition (HD) 3D imaging applications
Summary
Quantum-confined Stark effect (QCSE) [1] based large area surface normal electroabsorption modulators (EAM) using GaAs/AlxGa1-xAs material operating at 850nm are attractive for high definition (HD) three dimensional (3D) imaging applications [2,3,4,5]. Extremely low voltage operation with high modulation performance over wide spectral range was achieved by using quasiwaveguide angled facet architecture [15] These reflection-type structures are not suitable for HD 3D imaging system since they significantly reduce the field of view and require complex optics system. We develop and demonstrate a large area transmission modulator that can be used for HD 3D imaging system having large transmittance change over wide spectral range and high modulation speed with low driving voltage at 850nm by introducing coupled tandem cavities (CTC) with asymmetric tandem quantum well (ATQW). By employing a n-i-p-i-n structure with separated electrode configuration, the two stacked diode with absorptive cavities of the modulator can operate simultaneously This is the reason why CTC with ATQW based EAM can reduce voltage requirements without degrading modulation performance. With a bias voltage larger than −7.5V, transmittance change of CTC with ATQW structure decreases since the excitonic peak of the constituent 7.5nm thick QW red shifts from 850 nm
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