Fiber Ring Resonator Research Articles

In-fibre temperature tuned fibre ring resonator for laser mode monitoring

We demonstrate a simple design for an in-fibre Fabry-Perot interferometer (FPI) equivalent, constructed by splicing together two ports of a 99:1 in-fibre beamsplitter to form a fibre ring resonator (FRR). A Peltier device is used to heat a length of the fibre, which scans the resonant frequency of the FPI in a controllable manner primarily by changing the refractive index of the fibre. This allows the device to be employed in applications where a standard Fabry-Perot cavity is used, in this case for laser mode monitoring. Our FRR has a measured finesse of 123(2) and is shown to be stable over long time periods. This provides an inexpensive and simple solution for applications with low performance requirements, and with relatively minor upgrades could be used for more exacting applications such as frequency locking.

Nonlinear correction of a laser scanning interference system based on a fiber ring resonator.

The laser scanning interferometry system has been successfully applied to many measurement fields because of its efficient measurement ability. However, the practical application ability of this measurement method is restricted due to the laser tuning nonlinearity. In this paper, the fiber ring resonator is equidistant in the frequency domain, which is used as the external clock signal to resample the main interference signal so as to realize the equifrequency sampling of the laser scanning interference system and correct the tuning nonlinearity. The final experimental result shows that this method can effectively reduce the phase noise caused by tuning nonlinearity and improve the performance of the system.

Self-injection locking technique for resonant micro-optical gyroscope

A self-injection locking method for resonant micro-optical gyroscope (RMOG) is proposed. The resonator is used as the sensitive element of the gyroscope and the device of light compression locking. The fiber and waveguide ring resonator (WRR) are designed and fabricated, consecutively. Both of the resonators can narrow the linewidth by three orders of magnitude, and the phase noise and the relative intensity noise can be reduced to −120 and −150 dBc / Hz, respectively. By evaluating the locking effect, WRR is more suitable for optical locking of a resonant micro-optical gyroscope (RMOG) light source, and its theoretical locking accuracy can reach 6.02 deg/s.

Improving the sensitivity of new passive optical fiber ring sensor based on meta-dielectric materials

In this paper a new passive optical fiber sensor depends on surface plasmon resonance (SPR) decorate by fabricating a configuration on metal-dielectric materials. A single-mode fiber is applied to harness the transmission light. In this work, FDTD method is introduced to control the injected refractive index on ring and fiber; hence, this leads to the shifting of the fiber SPR resonance wavelength. The advantageous of this mechanism is optical fiber sensor has a high sensitivity with the maximum of up to 1700 nm/RIU, wide detection range of 1–1.4 RIU (refractive index unit), and a nanometer resolution with a minimum of 4 nm. In addition, moreover we consider several performance parameters like sensitivity and FOM, interestingly it is shown applying silicon optical fiber improve the sensitivity. Comparing with the reported numerical and measurements based on an optical fiber structure, the experimental results based on fiber ring resonator demonstrate good ability and agreement, therefore the proposed structure pave the path new operation of optical fiber sensors.

Experimental investigation of light-matter interaction when transitioning from cavity QED to waveguide QED

Cavity quantum electrodynamics (cavity QED) is conventionally described by the Jaynes- or Tavis-Cummings model, where quantum emitters couple to a single-mode cavity. The opposite scenario, in which an ensemble of emitters couples to a single spatial mode of a propagating light field, is described by waveguide QED, where emitters interact with a continuum of frequency modes. Here we present an experiment where an ensemble of cold atoms strongly couples to a fiber-ring resonator with variable length containing an optical nanofiber. By changing the length of the resonator we can tailor the density of frequency modes and thus explore the transition from cavity QED to waveguide QED. We analyse the response of the ensemble–cavity system after the sudden switch-on of resonant laser light and find that for progressively longer resonators, the Rabi oscillations typical of cavity QED disappear and the single-pass dynamics of waveguide QED appear. Our measurements shed light on the interplay between the single-pass collective response of the atoms to the propagating cavity field and the ensemble–cavity dynamics.

A Hollow-Core Photonic-Crystal Fiber-Optic Gyroscope Based on a Parallel Double-Ring Resonator.

A novel system structure of resonant fiber optical gyroscope using a parallel double hollow-core photonic crystal fiber ring resonator is proposed, which employs the double closed loop and reciprocal modulation–demodulation technique to solve the problem of the length mismatch between rings. This structure can suppress the residual amplitude modulation noise and laser frequency noise, essentially eliminating the influence of the Rayleigh backscattering noise and dramatically reduce the Kerr-effect-induced drift by three orders of magnitude. Thanks to its excellent noise suppression effect, the sensitivity of this novel system can approach the shot-noise-limited theoretical value of 8.94 × 10−7 rad/s assuming the length of the fiber ring resonator is 10 m.

Compact fiber-ring resonator for blue external cavity diode laser stabilization

We demonstrate a compact and low-cost all-fiber-based locking setup for frequency-noise suppression of a 420 nm external-cavity diode laser. Frequency noise reduction in the 100 Hz to 800 kHz range is demonstrated up to 40 dB associated with a linewidth narrowing from 850 kHz to 20 kHz for 10 ms integration time. This simple locking scheme might be implemented for a large range of wavelengths and can be integrated on a small footprint for embedded applications requiring narrow linewidth blue laser diodes.

Numerical investigations of cavity-soliton distillation in Kerr resonators using the nonlinear Fourier transform

Dissipative cavity solitons (CSs) in a Kerr resonator have wide applications from optical communications to spectroscopy due to their broad bandwidth. Although the broadband spectrum ultrashort pulses are easy to be generated in a high-$Q$ microresonator, such kinds of solitons in the macroscopic fiber ring resonator are difficult to be obtained. Dispersion management can be a feasible method to realize soliton compression, but the Kelly-like sidebands in the frequency domain are increased inside the cavity. To achieve a perfect soliton from a macroscopic cavity, an ingenious method of nonlinear Fourier transform (NFT) is utilized here to filter out the sidebands. The CS is mapped to different components in the nonlinear spectrum and a pure soliton can be reconstructed from the resonant continuous-wave background accordingly. Numerical simulations demonstrate NFT can be an effective method for CS analysis both in the time and frequency domains. Our investigations exemplify another application of NFT in a dissipative nonlinear system.

Tunable Q-switched Tm/Ho-codoped fiber laser based on a thermo-optically controlled multimode interference fiber structure

We present all-fiber tunable Q-switched lasers incorporating a thin-film GaAs saturable absorber and a single-mode–multimode–single-mode (SMS) fiber structure with a liquid cladding in a Tm/Ho-codoped fiber ring resonator. The fiber laser generates a pulse train with a peak pulse power of 535 mW, a repetition rate of 37.4 kHz and a pulse width of 680 ns under a pump power of 221 mW. The oscillation wavelength is tunable over a 111 nm range from 1858 to 1969 nm by controlling the temperature of the SMS fiber structure. We expect that all-fiber tuning and Q-switching techniques without mechanical elements will provide compact and efficient laser systems for environmental sensing, eye-safe measurement, and medical applications.

Resonant fiber optical gyroscope using the single-mode fiber ring resonator.

This paper provides a scheme for realizing high-accuracy, low-cost resonant fiber optical gyroscopes (RFOGs) with single-mode (SM) fibers. The temperature-related polarization noise, which deteriorates the bias stability of the RFOG, has been suppressed thanks to a much longer birefringence beat length of SM fibers. It is also helpful to improve the theoretical sensitivity of the RFOG because of the very low loss of the SM fiber components. A transmissive 39-m-long SM fiber ring resonator (FRR) is fabricated. The measured finesse is 58.7, and its total loss is calculated to be less than 0.3 dB. Using this SM-FRR as the sensing element, an RFOG is then set up that achieves an angular random walk of 0.0039∘/√h and a bias stability of 0.05°/h. The experimental results show that the SM-FRR scheme would be a good candidate for producing high-accuracy and low-cost RFOGs.

Incoherence suppression method of optical noises in a resonant fiber optic gyro based on the circularly polarized light propagation mechanism in a resonator

Resonant fiber optic gyros (RFOGs) generally use fiber ring resonator propagating linearly polarized light, so it is inevitably affected by coherent optical noises between two counterpropagation beams such as nonlinear effect and backscattering noise. So, we propose the incoherent suppression method of optical noises in a RFOG based on the circularly state of polarization (CSOP) light. The spun-fiber is used to fabricate a resonator that can realize the reciprocal transmission of CSOP light for the first time, and the highly reciprocal signal processing scheme is applied in RFOG based on the Faraday effect. We demonstrate that the designed resonator realizes orthogonal separation of backscattered light thereby suppressing the backscattering noise, and we confirm that the reciprocal CSOP light can greatly reduce the nonlinear effect due to incoherence. With the closed-loop method based on the Faraday effect and spun-fiber resonator, whose finesse is 6.6 with a length of 11-meter spun-fiber and 6-meter single-polarization fiber, the long-term stability and short-term stability of a RFOG have been greatly improved. The incoherence method based on a reciprocal CSOP light propagation mechanism has great potential in the suppression of coherence optical noises in a RFOG, which provides a new, to the best of our knowledge, idea to solve the problem.

Parametric control of propagation of optical vortices through fibre ring resonators

In this paper, we have studied transmission of optical vortices (OVs) through ring resonators (RRs) based on multimode fibres. Using the formalism of transfer matrix we have obtained in the scalar approximation the analytical expressions for amplitudes of transmitted OVs with opposite topological charges (TCs) as functions of RR’s parameters. We have calculated the orbital angular momentum (OAM) of the outcoming field and shown that by changing such parameters one can efficiently control its TC and continuously change its OAM. We have established that TC and OAM feature wavelength-scale sensitivity to variations of the ring’s length. We have demonstrated that this ability of RRs to influence OAM is due to a multipass interference assisted with TC inversion in the coupling area. We have also studied the effect of losses on the transmission of OVs through RRs and established that by controlling the attenuation parameter one can also control the TC of the outcoming field. Finally, we have solved the problem of OV transmission within the frameworks of a fully vectorial approach that allows for the spin–orbit interaction (SOI) in fibres. We have shown that accounting the SOI does not alter the main properties of RRs established with the use of the scalar approximation theory. We have shown that RRs, which operate on OAM modes, can be used for emulation of the quantum logical X, Y, S, T and Z gates. This can be useful for optical simulation of quantum computations.

Phase Shift-Cavity Ring Down Spectroscopy in Linear and Active Fiber Cavities for Sensing Applications at 1550 nm

Liquid phase sensing applications at 1550 nm are highly desirable due to widely available off-the-shelf components. Generally, liquids at 1550 nm induce a high absorption loss that limits the overall sensor’s sensitivity and detection limit. One solution is to use an active fiber loop in conjunction with cavity ring down spectroscopy to overcome these absorption losses. However, the amplifier inside the fiber loop suffers from inherent gain fluctuations that limit the sensing system’s overall performance. Here, we provide a novel sensor using the wavelength-scanned phase shift-cavity ring down spectroscopy (PS-CRDS) in conjunction with a linear active fiber cavity that potentially offers a more sensitive solution than traditional fiber loop sensors. We use a tapered fiber as a sensing head inside the active cavity built from fiber Bragg gratings. We derive a theoretical phase shift expression for our system and simulate it using the finite element method to determine optimum tapered fiber diameter for glucose sensing in DI water. Compared to a non-amplified system, we find that our amplified system can increase the sensitivity by fourteen times via the amplifier gain tuning. We also conduct experimental measurements using 0-15.5 mM glucose solutions and find them in excellent agreement with our theoretical predictions. Experimentally we obtain the sensor’s sensitivity of 0.768°/mM (1164°/RIU) and detection limit of 0.75 mM ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4.5\times 10^{-4}$ </tex-math></inline-formula> RIU) without any temperature stabilization in the system. We anticipate that the present work will find a wide range of sensing applications in fiber cavities, ring resonators, and other microcavity structures.

Tunable Fano and EIT-Like Resonances in a Nested Feedback Ring Resonator

In this paper, we realize tunable Fano and electromagnetically induced transparency (EIT)-like resonances in the outputs of a nested feedback ring resonator. Compared with the traditional add-drop ring resonator, the feedback arm introduces interference between different resonance modes. Using coupled mode theory, we reveal that the output Fano resonances are the interference of discrete modes and continuum modes, whereas the EIT-like resonance only appears in the over-coupled state. We experimentally confirm the two effects using optical fiber ring resonators, finding that the Fano effect can be easily controlled with phase shifts in the feedback arm. Moreover, we achieve the double Fano resonance, which displays an ‘X’ type lineshape utilizing one ring resonator, predicting it to be a good candidate in wavelength monitor. The proposed simple configuration provides a platform to study Fano and EIT-like effect, which is useful in the optical filter, fast and slow light, optical switching, and optical sensing.

Fiber based all-optical infinite impulse response filter tuned via stimulated Brillouin scattering

In this paper, we present a novel configuration for an all-fiber tunable infinite impulse response optical filter using stimulated Brillouin scattering. By applying the Brillouin acoustic waves within the coupling area of an optical coupler, we can control its transmissivity and so to affect the spectral response of the IIR optical filter. In this paper, we explain the principle of operation of the proposed device and experimentally demonstrate the ability to control the spectral response of an optical filter based on fiber ring resonator configuration.

Theory of filter-induced modulation instability in driven passive optical resonators

We present the theory of modulation instability induced by spectrally dependent losses (optical filters) in passive driven nonlinear fiber ring resonators. Starting from an Ikeda map description of the propagation equation and boundary conditions, we derive a mean field model - a generalised Lugiato-Lefever equation - which reproduces with great accuracy the predictions of the map. The effects on instability gain and comb generation of the different control parameters such as dispersion, cavity detuning, filter spectral position and bandwidth are discussed.

Dissipative Polarization Domain Walls in a Passive Coherently Driven Kerr Resonator.

Using a passive, coherently driven nonlinear optical fiber ring resonator, we report the experimental realization of dissipative polarization domain walls. The domain walls arise through a symmetry breaking bifurcation and consist of temporally localized structures where the amplitudes of the two polarization modes of the resonator interchange, segregating domains of orthogonal polarization states. We show that dissipative polarization domain walls can persist in the resonator without changing shape. We also demonstrate on-demand excitation, as well as pinning of domain walls at specific positions for arbitrary long times. Our results could prove useful for the analog simulation of ubiquitous domain-wall related phenomena, and pave the way to an all-optical buffer adapted to the transmission of topological bits.

Laser stabilization to a cryogenic fiber ring resonator.

The frequency stability of lasers is limited by thermal noise in state-of-the-art frequency references. Further improvement requires operation at cryogenic temperature. In this context, we investigate a fiber-based ring resonator. Our system exhibits a first-order temperature-insensitive point around 3.55K, much lower than that of crystalline silicon. The observed low sensitivity with respect to vibrations (<5⋅10-11m-1s2), temperature (-22(1)⋅10-9K-2), and pressure changes (4.2(2)⋅10-11mbar-2) makes our approach promising for future precision experiments.

Graphene Self-Phase-Lockers Formed around a Cu Wire Hub for Ring Resonators Incorporated into 57.8 Gigahertz Fiber Pulsed Lasers.

We demonstrate graphene-functionalized self-phase-locking of laser pulses for a dramatically elevated repetition rate by employing an intrinsic resonating structure in a fiber ring laser cavity, the modes thereby satisfying the phase-matching condition passively, through both the resonator and the laser cavity. Graphene is directly synthesized around a 1-mm-diameter Cu wire catalyst, avoiding the deleterious transfer process. The wire provides a form factor to the fiber ring resonator as a versatile winding hub, guaranteeing damage-minimized and recyclable contact of the synthesized graphene with a diameter-controlled optical microfiber. In-depth analysis of the graphene confirms the optical nonlinearity critically required for pulse formation. The laser-graphene interaction, the intermode phase-locking function of graphene, and the pulse formation with the resonator are systematically elucidated to explain the experimentally generated laser pulses at a repetition rate of 57.8 gigahertz (GHz). Additionally, tunability of the repetition rate up to 1.5 GHz by the photothermal effect of graphene is demonstrated.

Research on laser frequency locking technology based on temperature and PZT control

Aiming at the application requirement of resonator fiber optic gyroscopes, a frequency tracking and locking control scheme based on laser temperature and PZT control is proposed in this paper. By taking advantages of the large range of laser temperature tuning as well as the high precision and high dynamicity of PZT tuning, tracking of the fiber laser's central frequency to the fiber ring resonator's resonance frequency is realized. Typical transmission resonant curve is simulated by mathematical methods. Hardware design, algorithm simulations of temperature and PZT control scheme are carried out. The influence of control parameters on tracking stability is analyzed. The development of laser frequency tracking systems is assembled. The high-precision and long-time tracking of laser's central frequency to resonance frequency is realized successfully. The locking precision is low to 4.8×10-9 over one hour under room temperature. The locking precision is low to 9.74×10-8 over 5.5 hours under variable temperature. This work has laid an important foundation for improving the long-term performance of resonator fiber optic gyroscopes.