The role of refractive index gradient on sensitivity and limit of detection of microdisk sensors

Najafi, Zohreh; Vahedi, Mohammad; Behjat, Abbas

doi:10.1016/j.optcom.2016.04.046

Cited by 10 publications

(5 citation statements)

References 29 publications

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“…Among the graded index structures, a modified form of "Maxwell's fish eye" has been studied in [4,5]. The authors investigated by numerical simulation the features of WGM in a 2D graded index micro-disk (with radius R) where refractive index varies according to the radial position r as n(r) = n 0…”

Section: Introductionmentioning

confidence: 99%

Mathematical analysis of whispering gallery modes in graded index optical micro-disk resonators

et al. 2020

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We study from a theoretical point of view whispering gallery modes (WGM) in graded index micro-disk resonators where the refractive optical index varies with the radial position. Using a quantum mechanical analogy, we highlight three different behaviors for the WGM depending on the sign of a key parameter expressed as the ratio of the refractive index value to its derivative at the cavity boundary. This results in three asymptotic expansions of the resonances for large polar mode index providing first-approximations of WGM in a simple and quick way. Besides, these expansions yield a theoretical fundation to considerations of Ilchenko et al. in J. Opt. Soc. Am. A 20, 157 (2003), about three sorts of effective potentials for TE modes in a dielectric sphere.

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Section: Introductionmentioning

confidence: 99%

Mathematical analysis of whispering gallery modes in graded index optical micro-disk resonators

et al. 2020

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“…The mainstream solution methods for the GRIN resonators are to substitute the refractive index analytic equation into Maxwell's equations to find the analytical solution [12][13][14][15], including the wave vector k and the component electric field E or magnetic field H of the mode field. However, since the actual GRIN cavities cannot be expressed analytically, this analytical method cannot guide the actual fabrication well.…”

Section: Numerical Methods Of the Rotationally Symmetric Microresonatorsmentioning

confidence: 99%

“…However, methods for solving GRIN resonators are still lacking. Although there have been some studies on GRIN resonators [12][13][14][15], they are for fixed refractive index distributions and cannot be used in real-world processes like ion-exchange. Additionally, the process parameters must be adjusted to choose the best n(r), which is time-consuming and difficult to program using commercial tools.…”

Section: Introductionmentioning

confidence: 99%

Large mode volume microresonator with a gradient refractive index

Chen,

Kang,

Zhang

et al. 2024

J. Opt. Soc. Am. B

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Whispering gallery mode microcavities have been widely explored because of high Q factors and small mode volumes. Although small mode volumes are beneficial in sensors and nonlinear applications, recent studies suggest that large mode volumes are required for noise reduction in advanced applications. To enhance the mode volume, one possible method is to utilize the material inside the cavity. Herein, a radial gradient refractive index (GRIN) microresonator has an internal potential well and allows the mode field to shift inward. The GRIN resonator is formed by changing the radial refractive index n(r), and can be produced by the mature ion-exchange process. By adjusting the process parameters, the internal potential well can be widened to generate large mode volumes. However, it takes a lot of time to optimize the process parameters of wide potential well resonators using commercial software. Therefore, in this paper, we propose a fast algorithm for radial GRIN microcavities. Using this algorithm, we optimize the diffusion and annealing times of the GRIN resonator to increase the mode volume to more than four times that of the WGM microcavity. COMSOL simulations also support the conclusion with no additional loss in the Q factor.

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“…Self-focusing lenses can be produced by GRIN in the radial direction of glass rods, which have been widely used in optical fiber couplers, semiconductor laser collimators, and so on, and have a wide range of applications in the optical communication field [13]. Earlier articles have discussed the characteristics of WGM microresonators manufactured with GRIN medium [14][15][16][17][18]. In 2003, V. S. Ilchenko et al discovered that if GRIN material is used for WGM microcavity, the position of the mode field will be shifted inward, thus significantly increasing the Q factor [14].…”

Section: Introductionmentioning

confidence: 99%

“…Furthermore, in 2016, Z. Najafi et.al. studied WGM microdisk resonator sensors with GRIN to achieve higher sensitivity [17]. Meanwhile, based on [14], S. Balac et al studied WGMs in GRIN microdisk resonators using a quantum mechanical analogy in 2020 [18].…”

Section: Introductionmentioning

confidence: 99%

Geometrical optical analysis of a gradient refractive index microresonator

Chen

Kang

et al. 2023

J. Opt. Soc. Am. A

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Optical microresonators confine light to small volumes through resonant circulation. Herein, whispering gallery mode (WGM) microresonators have high Q factors among these microresonators, which have significant research value in the fields of fundamental physics research and optoelectronic devices. However, maintaining a very high surface finish on the side of the microresonator is necessary, as is keeping a coupling distance of tens of nanometers between the microresonator and the coupling waveguide. Thus, this makes the fabrication, coupling, and packaging of the microresonator very difficult and seriously hinders the practical application of the microresonator. In this study, the concept of gradient refractive index (GRIN) microresonator is proposed, and the radial GRIN is introduced to change the light direction and form a closed optical path within the microresonator. Herein, the mode field position of the GRIN microresonator is derived from the light transmission equation, and the theoretical result is proved by finite difference time domain (FDTD) simulation. Hence, there are several advantages to using this novel optical microresonator, including its high Q factor, strong coupling stability, and ease of integration.

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The role of refractive index gradient on sensitivity and limit of detection of microdisk sensors

Cited by 10 publications

References 29 publications

Mathematical analysis of whispering gallery modes in graded index optical micro-disk resonators

Mathematical analysis of whispering gallery modes in graded index optical micro-disk resonators

Large mode volume microresonator with a gradient refractive index

Geometrical optical analysis of a gradient refractive index microresonator

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