Intersubband Electro-optic modulators

Lead Research Organisation: University College London
Department Name: Electronic and Electrical Engineering


Optical modulators are the key elements of optical transceivers. The multi-billion market of optical transceivers increasingly demands devices with higher performance with sustainable cost. Indium phosphide (InP) technology need to deliver next generation optical-communication systems beyond 100 G, and recent InP photonics innovations indeed promise high performance in terms of bandwidth, power consumption, and port density. In current generation InP based electro-absorption modulators that operate by interband absorption, the absorption recovery time reported is limited to 5 ps. On the other hand, intersuband transitions in InP based quantum wells is quite promising to achieve ultra-high speed optical modulation due to its intrinsic characteristics of sub-picosecond carrier relaxation time and large optical nonlinearities. Substantial improvements in the bandwidth can also be expected for devices operated by intersubband transitions along with other parallel processes, including thermionic emission and tunnelling. Moreover, the devices based on intersubband transitions take advantages of conventional III-V materials and the advanced InP engineering capability and reliable device technology, and thus different photonic components can be simply integrated on a single chip, leading to higher integration density and lower cost. Last but not least, standard interband EAMs are temperature dependent because the band edge moves with temperature at a rate around 0.5nm/C, while in intersubband electro-optic modulators, this rate is estimated to be reduced by one order, i.e. transition energy will move at around 0.05 nm/C, making it suitable for use as an uncooled device.

In this project, the potential of intersubband electro-optic modulators on InP substrates will be explored for the next generation data communication systems, which is aligned with the EPSRC thematic area, Information and communication technologies (ICT).

Aims and objectives:
The studentship project will focus on developing high speed modulators based on intersubband transitions.
The main objectives of the project are:
Objective 1: To understand the electro-optic effects of intersubband transitions in InGaAs/AlAsSb QWs.
Objective 2: Develop high quality quantum wells with abrupt interface and high crystal quality that are optically active at 1550 nm.
Objective 3: Optimise the device structure. Achieve high electro-optic coefficient and high speed modulation of the quantum wells.

Potential applications and benefits:
During the early stage of this project, both industrial and academic supervisors will guide the PhD student to develop necessary knowledge in this field by extensive literature review. Facility access and equipment will be provided for the training of the PhD student during the project, including epitaxy growth equipment and device processing cleanroom. The PhD student will also be trained for a number of material and device characterization equipment. At the end of the project, a new type of electro-optic modulator will be developed that can make the data communication faster and advance the ICT industry in UK. The PhD student will be provided the opportunities to attend domestic and international conferences to disseminate any scientific advance made in the project.


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Studentship Projects

Project Reference Relationship Related To Start End Student Name
EP/N509577/1 01/10/2016 30/09/2021
1928806 Studentship EP/N509577/1 01/10/2017 30/09/2021 Pouyan Matin