Effect of particle on the lasing threshold of optofluidic laser based on Fabry–Pérot microcavity

Nanowire Oligomer Waveguide Modes towards Reduced Lasing Threshold

Materials ◽

10.3390/ma13235510 ◽

2020 ◽

Vol 13 (23) ◽

pp. 5510

Author(s):

Henrik Mäntynen ◽

Nicklas Anttu ◽

Harri Lipsanen

Keyword(s):

Coating Layer ◽

Gain Medium ◽

Semiconductor Nanowires ◽

Lasing Threshold ◽

Modal Properties ◽

Waveguide Modes ◽

Fabry Perot ◽

Index Contrast ◽

Modal Field ◽

Nanowire Lasers

Semiconductor nanowires offer a promising route of realizing nanolasers for the next generation of chip-scale optoelectronics and photonics applications. Established fabrication methods can produce vertical semiconductor nanowires which can themselves act both as a gain medium and as a Fabry–Pérot cavity for feedback. The lasing threshold in such nanowire lasers is affected by the modal confinement factor and end facet reflectivities, of which the substrate end reflectivity tends to be limited due to small refractive index contrast between the nanowire and substrate. These modal properties, however, also depend strongly on the modal field profiles. In this work, we use numerical simulations to investigate waveguide modes in vertical nanowire oligomers (that is, arrangements of few vertical nanowires close to each other) and their modal properties compared to single nanowire monomers. We solve for the oligomer waveguide eigenmodes which are understood as arising from interaction of monomer modes and further compute the reflectivity of these modes at the end facets of the nanowires. We consider either the nanowires or an additional coating layer as the gain medium. We show that both types of oligomers can exhibit modes with modal properties leading to reduced lasing threshold and also give directions for further research on the topic.

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DENSITY OF STATES AND LASING THRESHOLD IN DYE-DOPED CHOLESTERIC LIQUID CRYSTALS

Journal of Nonlinear Optical Physics & Materials ◽

10.1142/s0218863510005078 ◽

2010 ◽

Vol 19 (01) ◽

pp. 15-32 ◽

Cited By ~ 2

Author(s):

L. M. BLINOV

Keyword(s):

Density Of States ◽

Cholesteric Liquid Crystal ◽

Lasing Threshold ◽

Analytical Technique ◽

Fabry Perot ◽

Dye Absorption ◽

Complex Transmission ◽

Different Thickness ◽

Threshold Gain ◽

Good Agreement

As the complex transmission coefficient for a Fabry–Perot dielectric plate is well-known, the density of states (DOS) approach by J. Bendickson et al. [Phys. Rev. E53, 4107 (1996)] was applied to the plate and a formula was found for the spectrum of its threshold gain for lasing from the dye-doped plate. Next, the dispersion relation and the spectrum of the threshold gain was discussed for the infinite helical cholesteric liquid crystal (CLC). Then the DOS approach was applied to the non-absorbing CLC layers having finite, different thickness. The threshold gain spectra were calculated and dependences were found of the minimum threshold gain on the layer thickness and the optical anisotropy of the material. Finally, the results of the DOS analytical technique were compared with numerical calculations based on the precise solutions of the Maxwell equations and, in such a way, the DOS technique has been proven. The contribution of the dye absorption was discussed separately. The experimental data presented in the paper are in good agreement with the threshold gain calculations.

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