Unidirectional emission from circular dielectric microresonators with a point scatterer

Dettmann, Carl P.; Morozov, G. V.; Sieber, Martin; Waalkens, Holger

doi:10.1103/physreva.80.063813

Cited by 60 publications

(57 citation statements)

References 33 publications

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“…36 also briefly discussed numerical simulations of a notched ellipse but for the situation of microcavities with dimensions comparable to the free-space wavelength and that the lens effect of the ellipse was not discussed. A "point scatterer" (37) in circular shaped microresonators has also been proposed recently to achieve directional emission. However, the shape of the resonator is not optimized and the structure is difficult to fabricate as the "high-index scatterer" is placed inside the cavity.…”

Section: Resultsmentioning

confidence: 99%

Whispering-gallery mode resonators for highly unidirectional laser action

Wang

Yan

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

199

125

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Optical microcavities can be designed to take advantage of total internal reflection, which results in resonators supporting whispering-gallery modes (WGMs) with a high-quality factor (Q factor). One of the crucial problems of these devices for practical applications such as designing microcavity lasers, however, is that their emission is nondirectional due to their radial symmetry, in addition to their inefficient power output coupling. Here we report the design of elliptical resonators with a wavelength-size notch at the boundary, which support in-plane highly unidirectional laser emission from WGMs. The notch acts as a small scatterer such that the Q factor of the WGMs is still very high. Using midinfrared (λ ∼ 10 μm) injection quantum cascade lasers as a model system, an in-plane beam divergence as small as 6 deg with a peak optical power of ∼5 mW at room temperature has been demonstrated. The beam divergence is insensitive to the pumping current and to the notch geometry, demonstrating the robustness of this resonator design. The latter is scalable to the visible and the near infrared, thus opening the door to very low-threshold, highly unidirectional microcavity diode lasers.F ollowing the first description of the whispering-gallery mode (WGM) phenomenon in the acoustic regime by Lord Rayleigh in London's St Paul's Cathedral (1) and its subsequent analysis in terms of guided surface waves by Raman and Sutherland (2), its study was later extended to the radiofrequency (3) and optical domains (4) through the investigation of the ionosphere and solid spheres, respectively. WGMs were later investigated in liquid droplets (5) and microdisk diode lasers (6), opening a previously undescribed direction in photonics technology. WGM resonators offer great promise for investigation in the physical sciences (6-8), and applications of these devices have spanned a wide range from unique laser sources (9) and dynamic filters in communications (10) to sensors (11). One drawback, however, is that, in rotationally symmetric cavities (6, 12), WGMs can only be coupled out inefficiently and isotropically through scattering of evanescent waves by surface roughness or diffraction losses when the radius of curvature is comparable to the wavelength (9).Previously, this problem was addressed through evanescent coupling using prisms (13), in-plane waveguide (14), or tapered fibers (15). The technique of using tapered waveguide (16) for coupling high Q WGMs out of cavities is quite successful for the study of fundamental cavity physics; however, it requires careful alignment and the devices are relatively sensitive to mechanical vibrations or other variations in the surrounding environment, which limit its usage for practical applications such as achieving microcavity lasers with directional emission. Another approach is to break the rotational symmetry by using deformed optical microcavities to increase the directionality of emission and power collection efficiency (17, 18), which has the advantage of easy and robust fabrication. Th...

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Section: Resultsmentioning

confidence: 99%

Whispering-gallery mode resonators for highly unidirectional laser action

Wang

Yan

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

199

125

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“…This has been shown in theoretical works for a microdisk with a point scatterer (Dettmann et al, 2009b) and a deformed microdisk (Ryu and Lee, 2011).…”

Section: B Exceptional Pointsmentioning

confidence: 99%

“…An alternative way to direct the scattered rays is to insert a vertical groove at which the light is reflected back towards the cavity's boundary (Cai et al, 2011). The effect of internal point-like defects on WGMs has been analyzed by Dettmann et al (2008Dettmann et al ( , 2009b and Deych et al (2011). A line defect inside the disk has been studied by Apalkov and Raikh (2004).…”

Section: A Polygonal Cavitymentioning

confidence: 99%

Dielectric microcavities: Model systems for wave chaos and non-Hermitian physics

2015

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“…This problem can be solved by deforming the boundary of the cavity [12][13][14]. Several shapes for unidirectional light emission have been proposed, for example the spiral cavity [15][16][17], the annular cavity [18], the limaçon cavity [19], the circular disk with a point scatterer [20], and the notched ellipse [21].…”

Section: Introductionmentioning

confidence: 99%

Nonorthogonal pairs of copropagating optical modes in deformed microdisk cavities

Wiersig¹,

Eberspächer²,

Shim³

et al. 2011

Phys. Rev. A

108

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Recently, it has been shown that spiral-shaped microdisk cavities support highly nonorthogonal pairs of copropagating modes with a preferred sense of rotation (spatial chirality) [Wiersig et al., Phys. Rev. A 78, 053809 (2008)]. Here, we provide numerical evidence which indicates that such pairs are a common feature of deformed microdisk cavities which lack mirror symmetries. In particular, we demonstrate that discontinuities of the cavity boundary such as the notch in the spiral cavity are not needed. We find a quantitative relation between the nonorthogonality and the chirality of the modes which agrees well with the predictions from an effective non-Hermitian Hamiltonian. A comparison to ray-tracing simulations is given.

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Unidirectional emission from circular dielectric microresonators with a point scatterer

Cited by 60 publications

References 33 publications

Whispering-gallery mode resonators for highly unidirectional laser action

Whispering-gallery mode resonators for highly unidirectional laser action

Dielectric microcavities: Model systems for wave chaos and non-Hermitian physics

Nonorthogonal pairs of copropagating optical modes in deformed microdisk cavities

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