Whispering Gallery Mode Microsphere Resonator Research Articles

A Reflective Whispering Gallery Mode Microsphere Resonator Integrated With a Thick-Wall Capillary Tube

A Reflective Whispering Gallery Mode Microsphere Resonator Integrated With a Thick-Wall Capillary Tube

Fano-like line shape and its tuning effect in a double-handle whispering gallery mode microsphere resonator

Fano-like line shape and its tuning effect in a double-handle whispering gallery mode microsphere resonator

Whispering gallery mode microsphere resonator based on cylindrical air cavity coupling.

In this Letter, an optical fiber whispering gallery mode microsphere resonator based on cylindrical air cavity coupling is proposed and demonstrated. The cylindrical air cavity is vertical to the axis of a single-mode fiber and in touch with the fiber core, fabricated by using femtosecond laser micromachining together with hydrofluoric acid etching. A microsphere is inserted into the cylindrical air cavity and in tangential contact with the inner cavity wall, which is in touch with or inside the fiber core. The light traveling in the fiber core is coupled into the microsphere via an evanescent wave when the light path is tangential to the contacting point of the microsphere and the inner cavity wall, resulting in whispering gallery mode resonance when the phase-matching condition is satisfied. Such a device is highly integrated, robust in structure, low in cost, stable in operation, and has a good quality factor (Q) of 1.44 × 104.

Whispering gallery mode resonator based on dual microspheres in an expanded hollow sphere cavity of capillary tube

A whispering gallery mode microsphere resonator is proposed and demonstrated. The device is based on dual microspheres embedded in an expanded hollow sphere cavity formed by splicing a single-mode fiber and a capillary tube. The whispering gallery mode resonance is excited by the light traveling along the hollow sphere cavity wall and directed out by use of a tapered optical fiber in closing contact with one of the microspheres. The device has a good quality factor (Q) of 2.072 × 103, and a number of asymmetric Fano resonance lines. It is compact in structure, low in cost, simple in fabrication, and convenient in operation.

A Whispering Gallery Mode Microsphere Resonator Integrated With Angle Polished Multimode Fiber

We demonstrate a robust whispering-gallery-mode (WGM) microsphere resonator, fabricated by splicing two sections of multimode fiber (MMF) with end face polished to an angle of 45 degree. The polished end faces are etched by hydrofluoric (HF) acid to form an elliptical-shaped cavity to embed a microsphere before being firmly connected by UV adhesive. Part of the incident light traveling along the fiber core is coupled into the microsphere in the tangential direction to the surface of the microsphere and excites WGM. Such a microsphere resonator is highly robust and compact in size, and has a Q-factor of 5.15 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> . When used as a temperature sensor, the sensitivity obtained is 6.4 pm/°C.

All-Pass and Add-Drop Microsphere Resonator in a Suspended Dual-Core Hollow Fiber

In this paper, we demonstrate an in-fiber all-pass and add-drop whispering gallery mode microsphere resonator. We fusion splice a section of single mode fiber (SMF) to a section of suspended dual-core hollow fiber (SDCHF), into which a microsphere is then embedded. Most of the input light from the SMF can be coupled into the cores of the SDCHF, with a maximum coupling efficiency obtained when maintaining a balance between the cone-apex angle and the core size of SDCHF in the conical region. The optical spectrum can be clarified by reducing coupling paths between the microsphere and the SDCHF. It is observed that the linewidth of the resonance peak is halved with halved coupling paths in the coupling model. When the microsphere with a suitable diameter is located at a critical position in the SDCHF, the coupler turns from an all-pass into an add-drop coupling structure. The device also demonstrates good stability as a refractive index (RI) sensor with a sensitivity of -386.12 dB/RIU when the RI of the surrounding medium ranges from 1.3333 to 1.3714. This in-fiber resonator device is inherently robust, compact, and has a great potential for sensing applications.

Integrated in-fiber coupler for a whispering-gallery mode microsphere resonator

An integrated in-fiber coupler is proposed and demonstrated, which can excite whispering-gallery mode (WGM) in a microsphere resonator. This device is fabricated firstly by using femtosecond laser micromachining and a fusing splicing technique to create an inner air cavity with a suspended fiber core, then an open micro-channel is drilled on the top of the inner air cavity, and finally a microsphere is placed inside the air cavity, in contact with the suspended fiber core, to excite the WGM through the evanescent field. In the transmission spectrum of the device, the slopes of the two asymmetric Fano resonance lines of 41.12 dB/nm and $ - {18.46}\;{\rm dB/nm}$-18.46dB/nm, respectively, and a symmetrical Lorentz line with a quality factor of ${9.32} \times {{10}^3}$9.32×103 can be obtained simultaneously. Such an in-fiber WGM microsphere resonator has the advantages of compact structure, convenient operation, and high durability.

Research on Fabrication and Sensing Properties of Fiber-Coupled Whispering Gallery Mode Microsphere Resonator

In this paper, a fiber-coupled whispering gallery mode (WGM) microsphere resonator was fabricated with using a simple package scheme. The resonant properties of the WGM resonator are analyzed and their responses to bulk refractive index and temperature are theoretically and experimentally investigated. Experiment results show that the bulk refractive index sensitivity is about 20.49 nm/RIU with detection limit of $4.3\times 10^{-4}$ RIU and very low temperature sensitivity of 7.38 pm/°C. Moreover, the WGM microsphere resonator is firstly used for acoustic intensity level sensing, and the sensitivity is about −1.9 pm/dB, which can enlarge the application field of the WGM sensor and can be used for noise monitoring to enhance environmental protection.

Whispering gallery mode microsphere resonator with microsphere-microsphere coupling

Abstract We demonstrate a new type of whispering gallery mode microsphere resonator with microsphere-microsphere coupling. The device is based on two cascaded microspheres glued on a single mode fiber tip. The incident light from the fiber core diverges in the first microsphere and part of light is coupled to the surface of the second microsphere, exciting whispering gallery mode resonance when the angle between the connection line of the two microsphere centers and the fiber axis is appropriate. Such a whispering gallery mode microsphere resonator is robust in structure, compact in size, easy in fabrication and stable in operation.

In-fiber whispering-gallery mode microsphere resonator-based integrated device.

A novel in-fiber whispering-gallery mode (WGM) microsphere resonator-based integrated device is reported. It is fabricated by placing a silica microsphere into an embedded dual-core hollow fiber (EDCHF). Using a fiber tapering method, a silica microsphere can be placed and fixed in the transition section of the hollow core of the EDCHF. The transmitted light from the tapered-input single-mode fiber is coupled into the embedded silica microsphere via the two suspended fiber cores, and hence effectively excites the WGMs. A Q-factor of 5.54×103 is achieved over the wavelength range of 1100-1300nm. The polarization and temperature dependence of the in-fiber WGM microsphere resonator device is also investigated experimentally. This integrated photonics device provides greatly improved mechanical stability, compared with the traditional tapered fiber-coupled WGM microresonator devices. Additional advantages include ease of fabrication, compact structure, and low cost. This novel in-fiber WGM resonator integrated device is ideally positioned to access a wide range of potential applications in optical sensing and microcavity lasing.

A scatterer-assisted whispering-gallery-mode microprobe

Abstract A fiber-based whispering-gallery-mode (WGM) microprobe, combining both the high optical field enhancement of the WGMs and the compact structure of the optical fiber, is highly desired for sensing and imaging. Here we report a WGM microsphere resonator coupled to a single-mode fiber interfaced by a graded-index lens. By scattering a focused laser beam through a nano-scatterer, with the help of a two-step focusing technique as well as Purcell effects, the efficient far-field coupling of WGMs with an efficiency as high as 16.8% has been demonstrated in our system. With the feature of both input and output of the probe light propagating along the same fiber, such a scatterer-assisted WGM microprobe will serve as a convenient tool for sensing/imaging applications.

In-Line Fiber Michelson Interferometer for Enhancing the Q Factor of Cone-Shaped Inwall Capillary Coupled Resonators

An in-line fiber Michelson interferometer in a cone-shaped inwall capillary with the whispering gallery mode microsphere resonator integrated inside is demonstrated for enhancing the Q factor, which is fabricated on the etched capillary by the femtosecond laser micromachining to decrease the coupling paths. The modulated symmetric WGM resonances and asymmetric Fano resonances induced by the Michelson interferometer are observed in the reflection spectra, with a slope of 91.87 dB/nm and Q factor as 3.85 × 104 achieved. Numerical simulations with the transfer matrix method also validate the resonator spectra modulated by the Michelson interference. This method shows a perspective potential for the enhancement of the Q factor by tailoring interacting paths through the femtosecond laser micromachining.

Whispering gallery mode microsphere resonator integrated inside a microstructured optical fiber

A compact and robust scheme for broadband excitation of whispering gallery mode (WGM) resonances into a microsphere is demonstrated. A polymer microsphere (10 μm) is encapsulated into the capillary of a microstructured optical fiber, in direct contact with the guiding core. Such a configuration allows efficient and reproducible excitation of the in-MOF-microsphere resonator that is characterized by two launch/collection schemes: core input/scattering output, and sphere input/core output. The latter allows an excitation of the microsphere WGMs externally to the fiber. Numerically calculated WGM spectra are in agreement with experiments. Q factors in the range of 10(3) are typically measured.