External seminar archive:

Tammtronics: Quantum light sources and photodetectors based on Tamm plasmons

13 September 2019
Dr Edmund Harbord, University Of Bristol

Quantum dots (QDs) - semiconductor nanostructures confined in all three dimensions - are attractive not only as single photons sources (SPS) but also as a gain medium for lasers. They possess close-tounity internal quantum efficiency. However, practical applications require photonic structures to produce a high external quantum efficiency, and to shape the optical mode of the emitting light.

I will be talking about the Tamm plasmon structure, a way to confine light at the interface between a distributed Bragg reflector and a thin metal mirror - these confined states are the optical analogue of the well-known electronic surface states described by Tamm.

This allows us to create spatial light confinement simply by patterning a metal layer, avoiding the electronic surface states formed by processing into the semiconductor, and thus gives us a simple and attractive of forming structures for light sources, photodetectors, and single photon sources.

I will talk about our design [1] and fabrication [2] of confined Tamm plasmons at telecoms wavelengths, as well as our fabrication of a photodetector exploiting confined Tamm plasmons to achieve polarisation selectivity and spectral discrimination [3].

I will discuss some joint work with the University of Essex to develop a semi-analytical model to design Tamm plasmon devices rapidly, minimising the need for computationally intensive calculations [4]. I will also discuss progress towards future applications based on Tamm plasmon structures, including Tamm lasers, single photon sources, and THz generation.

Figure 1 above:

  • (a) Schematic of a Tamm plasmon structure, consisting of a GaAs/AlAs distributed Bragg reflector with a thin layer of gold on the top to provide the confinement.

  • (b) Calculated reflectivity by the 1D transfer matrix method for the reflectivity of a 17.5 layer DBR with a 75nm GaAs spacer layer (blue) and with a 25nm layer of gold on top (yellow). With the gold, the pronounced dip corresponding to the Tamm mode is clearly visible at 1,300nm.

  • (c) The electric field calculated for the for the bare DBR (blue) and the Tamm plasmon mode (yellow). The field is strongly enhanced by the gold, especially in the spacer layer.

  • (d) Characterisation of the as-grown sample - PL (red, with grey shade) from the QDs in the spacer layer shows a broad (FWHM~55nm) range of QD sizes, with a maximum at 1,310nm. The reflectivity (blue) agrees well with the reflectivity calculated by the 1D transfer matrix method.

  • (e) Schematic of the device - the confined Tamm mode is formed under the disk at the centre. The QDs form the absorption medium. Metal contacts allow the photoresistance to be measured.

  • (f) Electron microscope image showing the fabricated device, with the Tamm disk in the middle. The C-shaped contacts on either side allow the photoresistance to be measured.


  1. Parker, Harbord et al., IET Optoelectron., 12(1), pp. 11-14 (2018).

  2. Parker, Harbord et al., arXiv:1903.01151v1.

  3. Harbord et al., (under submission).

  4. Adams et al., JOSA B, 36(1), pp. 125-130 (2019).