Semiconductor microcavities

Bjork, G. and Yamamoto, Y., 1991, Analysis of semiconductor microcavity lasers using rate equations, IEEE J. Quantum. Electron., 27( 11 ) 2386-2396. 

Lidzey et al. have demonstrated that, under appropriate conditions, there can be strong coupling between excitons and photons in organic semiconductor microcavities.14 Clear evidence has been found for the formation of polariton... 

In spite of impressive experimental demonstrations of basic quantum information effects in a number of different mesoscopic solid state systems, such as quantum dots in semiconductor microcavities, cold ions in traps, nuclear spin systems, Josephson junctions, etc., their concrete implementation is still at the proof-of-principle stage [1]. The development of materials that may host quantum coherent states with long coherence lifetimes is a critical research problem for the nearest future. There is a need for the fabrication of quantum bits (qubits) with coherence lifetimes at least three-four orders of magnitude longer than it takes to perform a bit flip. This would involve entangling operations, followed by the nearest neighbor interaction over short distances and quantum information transfer over longer distances. 

A Dodabalapur, LJ Rothberg, TM Miller, and EW Kwock, Microcavity effects in organic semiconductors, Appl. Phys. Lett., 64 2486-2488, 1994. 

Figure 7. Difference in the spontaneous emission enhancement in a LED (a) and a microcavity laser (b) Density of electronic states in bulk semiconductor material and lowdimensional semiconductor heterostructures (c).

It should be noted, however, that the Q factors of open microcavities do not characterise directly the threshold gain values of the corresponding semiconductor lasers. To overcome this difficulty a new lasing eigenvalue problem (LEP) was introduced recently (Smotrova, 2004). The LEP enables one to quantify accurately the lasing frequencies, thresholds, and near- and far-field patterns separately for various WG modes in semiconductor laser resonators. However, the threshold of a lasing mode depends on other... 

Microcavity studies have employed a number of optically active materials inorganic semiconductors,6,9 organic liquids,2 and organic thin-film structures capable of charge transport.10,19 In this chapter, we shall be concerned with the latter class of materials, which include evaporated small molecules and conjugated polymers. These materials are used in device configurations that often include electron- and... 

For the formation of microcavities, it is necessary that a complete two-dimensional PBG exists at least for one polarization (TE or TM) and ideally for both polarizations. This involves careful design and requires that there be a sufficient index difference between the two materials. The photonic band structure of a triangular lattice of air holes in a membrane of SiCF coated with a thin layer of organic semiconductor has been described in Ref 24. Such a structure has been shown to possess a complete bandgap for TE polarized light. In a photonic lattice which possesses a complete bangap, it is possible to create a microcavity... 

The effects produced by a planar microcavity on the electroluminescence characteristics of organic materials have been described. A number of organic and polymeric semiconductors have been employed by various groups in studies on microcavity LEDs. However, for detailed descriptions, three categories of emissive materials have been considered undoped Alq, Alq doped with 0.5% pyrromethene, and Alq+NAPOXA. Alq has a broad free-space emission spectrum spanning the... 

Dodabalapur A, Rothberg L.J., Rothberg L.J., Miller T.M., " Electroluminescence from organic semiconductors in patterned microcavities". Electron. Lett., 30,1994,1000. 

In conventional LEDs, the spectral characteristics of the devices reflect the thermal distribution of electrons and holes in the conduction and valence band. The spectral characteristics of light emission from microcavities are as intriguing as they are complex. However, restricting our considerations to the optical axis of the cavity simplifies the cavity physics considerably. If we assume that the cavity resonance is much narrower than the natural emission spectrum of the semiconductor, then the on-resonance luminescence is enhanced whereas the off-resonance luminescence is suppressed. The on-axis emission spectrum should therefore reflect the enhancement, that is, the resonance spectrum of the cavity. The experimental results shown in Fig. 1.9 confirm this conjecture. 

Lasing was also observed for semiconductor nanocrystals in solution at room temperature, by using a cylindrical microcavity with nanosecond excitation. For this, a simple microcavity set-up was used which provided an uncomplicated means... 

A. Dodabalapur, L. J. Rothberg, T. M. Miller, E. W. Kwock, Microcavity Effects in Organic Semiconductors. Appl. Phys. Lett. 1994,64, 2486. 

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