Size and morphology dependent evolution of resonant modes in ZnO microspheres grown by hydrothermal synthesis

Ngo, Trong Huynh-Buu; Chien, Ching-Hang; Wu, Shang-Hsuan; Chang, Yia-Chung

doi:10.1364/oe.24.016010

Cited by 17 publications

(5 citation statements)

References 24 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The fabrication of semiconductor microspheres remains challenging [5,6] owing to their crystalline structure. This can be compared with the ease of fabrication of the amorphous microspheres of silica or polymer [7,8].…”

Section: Introductionmentioning

confidence: 99%

Inner structure of ZnO microspheres fabricated via laser ablation in superfluid helium

Minowa¹,

Oguni²,

Ashida³

2017

Opt. Express

View full text Add to dashboard Cite

ZnO microspheres fabricated via laser ablation in superfluid helium were found to have bubble-like voids. Even a microsphere demonstrating clear whispering gallery mode resonances in the luminescence had voids. Our analysis confirmed that the voids are located away from the surface and have negligible or little effect on the whispering gallery mode resonances since the electromagnetic energy localizes near the surface of these microspheres. The existence of the voids indicates that helium gas or any evaporated target material was present within the molten microparticles during the microsphere formation.

show abstract

Section: Introductionmentioning

confidence: 99%

Inner structure of ZnO microspheres fabricated via laser ablation in superfluid helium

Minowa¹,

Oguni²,

Ashida³

2017

Opt. Express

View full text Add to dashboard Cite

show abstract

“…For synthesizing the ZnO microspheres, a hydrothermal method was used based on our previous report 27,28 . In short, aqueous solutions of 50 mM zinc nitrate hexahydrate (Zn(NO 3 ) 2 •6H 2 O), 50 mM zinc hexamethylenetetramine (HMT, C 6 H 12 N 4 ), and 35 mM trisodium citrate were first prepared.…”

mentioning

confidence: 99%

Interplay of Purcell Effect, Stimulated Emission, and Leaky Modes in the Photoluminescence Spectra of Microsphere Cavities

Chien

Ngo

et al. 2019

Phys. Rev. Applied

Self Cite

View full text Add to dashboard Cite

A theoretical model for describing the emission spectra of microsphere cavities is presented, and its predictions of detailed lineshapes of emission spectra associated with whispering gallery modes (WGMs) of various orders in ZnO microspheres (MSs) are verified experimentally by photoluminescence (PL) spectroscopy. The interplay of Purcell effect, quality factor, and leaky modes in spontaneous and stimulated emission spectra related to WGMs of all orders is revealed. The key success of the theory is based on the expansion of the full Green function of the MS in terms of all possible resonance modes in complex frequency space, which allows incorporation of contributions from leaky modes, stimulated emission processes, and Purcell effect. We show that the spontaneous emission spectrum calculated according to Mie theory (without Purcell effect) is dominated by the contribution of leaky modes, while the spontaneous and stimulated emission enhanced by Purcell effect are responsible for the main WGM resonance peaks observed experimentally. It is found that the stimulated emission peaks are doubly enhanced by their respective mode quality factor Q: one factor from the Purcell effect and the other factor from the photon number derived from the rate equation. After combining all these effects the theory can provide a quantitative description of fine features of both TE and TM modes (including higher-order modes) observed in the PL spectra of ZnO MSs. Surprisingly, it is found that for ZnO MS with diameter larger than 5 µm, the PL emission spectrum is dominated by higher-order modes. The quantitative understanding of the interplay of these emission mechanisms should prove useful for optimizing the performance of light-emitting devices based on micro resonators.

show abstract

“…The spheres obtained by this process will be of different sizes ranging from 0.5 µm to 25 µm, which gives an opportunity to explore the WGM emission property of spheres with different sizes in one time synthesis. More over, spheres obtained by laser ablation tend to have very smooth surface (with an average roughness [28] (r a ) ∼ 2 nm) which is one of the major requirements for WGM cavity lasing because rougher surface causes scattering leading to confinement loss [22]. In addition, we adopt this technique because of the challenge in effective doping of bigger Sm 3+ ion (1.075 Å) as a substitute to smaller Zn 2+ (0.74 Å) in ZnO lattice.…”

Section: Micro-sphere Fabricationmentioning

confidence: 99%

“…However, there are not many studies on the visible range WGM lasing in ZnO. To our best knowledge, the visible WGM studies so far in ZnO have been focused on the native defect related WGMs emissions [15][16][17][18][19][20][21][22][23][24][25][26] or WGMs of dye coated ZnO micro-cavity [27] except our recent report on achieving WGM lasing from Ho:ZnO micro-spheres in the red spectral range [28]. We have reported Ho 3+ -4f originated WGMs at 629-690 nm from Ho:ZnO micro-spheres of different sizes and their lasing properties [28].…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Realization of sharp visible WGM lasing from Sm³⁺ :ZnO micro-spheres fabricated by laser ablation technique

Fabitha

Wakiyama

Oshima

et al. 2020

J. Phys. D: Appl. Phys.

View full text Add to dashboard Cite

In this paper, the whispering gallery mode lasing from Sm 3+ doped ZnO micro-spheres operating in the visible wavelength range 550-750 nm is studied. Highly smooth and crystalline Sm 3+ :ZnO micro-spheres of various diameters were synthesized by simple laser ablation of sintered target in air. The dopant concentration has been restricted within the solid solubility limit of 1 mol%. The Sm 3+ ion substitution in ZnO matrix results in the formation of inter-band levels by the characteristic 4f level of Sm 3+ in the forbidden gap of ZnO. Thus, when the micro-spheres are excited with 488 nm, four major visible emissions associated with Sm 3+ f − f transitions namely, transitions from 4 G 5/2 to its low-lying multiplets of 6 H J (J = 5/2, 7/2, 9/2 and 11/2), are obtained. These emissions are coupled to the WGMs of the Sm 3+ :ZnO micro-cavity resulting in sharp resonances in the visible region. Interestingly, the resonances are found to be lasing above lower pumping powers. The Q-factor obtained is of the order of 10 3 for spheres of size ranging 1.8-10.2 µm. The best Q-factor obtained is 3744 for 561.61 nm peak (FWHM 0.15 nm) from 8 µm sphere. These results would find a place in visible range lasing and sensor applications.

show abstract

Size and morphology dependent evolution of resonant modes in ZnO microspheres grown by hydrothermal synthesis

Cited by 17 publications

References 24 publications

Inner structure of ZnO microspheres fabricated via laser ablation in superfluid helium

Inner structure of ZnO microspheres fabricated via laser ablation in superfluid helium

Interplay of Purcell Effect, Stimulated Emission, and Leaky Modes in the Photoluminescence Spectra of Microsphere Cavities

Realization of sharp visible WGM lasing from Sm³⁺ :ZnO micro-spheres fabricated by laser ablation technique

Contact Info

Product

Resources

About

Size and morphology dependent evolution of resonant modes in ZnO microspheres grown by hydrothermal synthesis

Cited by 17 publications

References 24 publications

Inner structure of ZnO microspheres fabricated via laser ablation in superfluid helium

Inner structure of ZnO microspheres fabricated via laser ablation in superfluid helium

Interplay of Purcell Effect, Stimulated Emission, and Leaky Modes in the Photoluminescence Spectra of Microsphere Cavities

Realization of sharp visible WGM lasing from Sm3+ :ZnO micro-spheres fabricated by laser ablation technique

Contact Info

Product

Resources

About

Realization of sharp visible WGM lasing from Sm³⁺ :ZnO micro-spheres fabricated by laser ablation technique