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A versatile optofluidic dye laser based on the sub-micron thickness resonator embedded in the Kagome photonic crystal fiber is demonstrated. The hexagonal hollow core supported by the cladding scaffolds serves as the microcavity and microfluidic channel for gain medium in the meantime, offering good compactness and robustness. Lasing emission could be achieved by employing dyes with refractive index either lower or higher than silica background. The lasing thresholds for dye LDS751 dissolved in methanol or DMSO at 0.2 mM are 0.43 and $0.51~\mu \text{J}$ , respectively. In addition, the lasing peaks exhibit obvious redshift as the refractive index of the gain medium increases, which is in agreement with our theoretical expectation.

We have investigated the properties of silica-tube-based whispering gallery mode dye lasers based on two different pumping schemes. A comparison of some fundamental laser properties such as lasing threshold and slope efficiency under different pumping schemes is presented in this article. Moreover, we have also studied lasing emission spectral shift induced by self-absorption of dye materials as well as change of quality factor under different dye concentrations. The compactness, low lasing threshold and spectral tunability of the proposed opto-fluidic ring resonator dye laser make it a good candidate for on-chip light source and related biochemical sensing applications. © 2017 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:609–614, 2017

An acoustooptic-mode-coupling-based scheme is proposed for excitation of whispering gallery modes (WGMs) in a silica-capillary microresonator. By exploiting acoustooptic mode coupling in a cladding-etched optical fiber, the evanescent field is strengthened by the cladding modes coupled from the core mode through axial flexural wave modulation, leading to the significant enhancement of the mode coupling between evanescent field and WGMs in a silica-capillary microresonator. WGM resonance peaks have been experimentally acquired by employing a cladding-reduced optical fiber with a diameter of 20.68 μ m, which is more robust than the coupling fibers of a few microns in diameter used in conventional WGM excitation schemes. Our proposed WGM coupling approach has desirable merits such as compactness, ease of fabrication, improved WGM coupling efficiency, and robustness, which is anticipated to find potential applications in optical filtering, microresonator laser, fiber sensor, as well as signal processing. Additionally, by controlling the electric driving signals to apply acoustic modulation, it would be convenient to achieve flexible tuning of WGMs based on acoustooptic coupling approach.

A laser-tuned whispering gallery modes (WGMs) microsphere resonator integrated with ethyl-orange-(EO-) doped polyvinyl alcohol (PVA) coating has been proposed and experimentally demonstrated. Owing to the photo-induced isomerization feature of the azo-doped coating, the WGM resonance wavelength could be tuned by adjusting the 532 nm excitation laser power density based on a lateral pumping scheme. The WGM tuning principle of the proposed microresonator has been investigated, which is in accordance with our experimental observation results. Experimental results indicate that the proposed functionalized microsphere has a fully linear WGM resonance wavelength tunability up to 0.158 nm/(mW mm −2 ). Further experimental study shows nonlinear WGM resonance wavelength shift respectively dependent on EO weight percentage and pump laser power densities, which is in agreement with our theoretical analysis. Moreover, our proposed microresonator also exhibits good spectral reversibility as well as dynamic temporal response, which ensures its potential applications in optical modulation and future all-optical networking systems.

A micro-fluidic-channel is proposed based on a fiber-tip-excited hollow-core photonic crystal fiber microresonator. The reflection conical fiber tip is fabricated based on electric arc fusion technique. A quality factor up to $8.65 \times 10^{\mathrm { {4}}}$ has been experimentally acquired at $\sim 1557.75$ nm. Theoretical simulation results indicate that the refractive index sensitivity of the whispering-gallery-mode resonance wavelength reaches 1259.9211 nm/RIU for biocompatible low refractive index range. The proposed microfluidic detection platform has a few desirable merits, such as ease of fabrication, low-cost, and structure robustness, which ensures its applicability for practical use in chemical as well as biological sensing applications.

A compact light-intensity-controlled Mach–Zehnder interferometer has been proposed by exploiting the photosensitivity of ethyl orange solution in combination with the evanescent field property of a microfiber-assisted Mach–Zehnder structure. We have experimentally investigated the influences of irradiation laser power density as well as weight percentage ratio of ethyl orange solution on the transmission spectral characteristics of the proposed microfiber-assisted fiber-optic interferometer. Experimental results indicate that the interference transmission spectra are highly sensitive to the applied excitation laser power density. An optimal ethyl orange weight percentage of 0.5 wt% has been experimentally acquired, with which the largest interference dip wavelength sensitivity reaches 0.02576 nm/(mW cm −2 ). Moreover, experimental observation on the transmission spectrum shows that the proposed MZI possesses good spectral reversibility, which ensures its applicability for practical applications.

A magnetic-fluids-infiltrated microbubble resonator is proposed and experimentally demonstrated. WGM tuning property of this microresonator under different pump laser power densities has been investigated, showing its potential applications in optically manipulated photonic devices.

We investigate the diffraction of an optical vortex, when half of the beam is blocked by a knife edge. The Gouy phase is shown to influence the diffraction pattern strongly, in particular leading to the emergence of distorted and deformed diffraction fringes in the azimuthal direction. In analogy with single-slit diffraction, this phenomenon is analyzed in terms of angular diffraction within the azimuthal degree of freedom, by considering the uncertainty principle for the angular position and the angular momentum. Numerical simulations based on the fast-Fourier algorithm and the angular momentum expansion fit well with the experimental results.