Bidirectional Ring Laser Research Articles

Coherent optical gyroscope on the basis of the bidirectional ultra-short pulse Erbium ring fiber laser

A gyroscopic effect has been studied in the bidirectional ultra-short pulse erbium-doped fiber ring laser hybridly mode-locked with a co-action of a Single-Walled Carbon Nanotube-based saturable absorber (SWCNT-SA) and Nonlinear Polarization Evolution introduced by means of the short-segment polarizing fiber. Owing to the Kerr nonlinearity contribution through self-phase modulation and self-steepening effects to the carrier-to-envelope phase slip of both clockwise (CW) and counterclockwise (CCW) solitons, wideband controllable tuning of a gyroscope bias point has been demonstrated by means of an appropriate adjustment of either intracavity polarization or pump power. Angular velocity detected ranges from 0.12 deg/s to 360 deg/s while the highest rotation sensitivity reaches 7 kHz/(deg/s) for 0.79 m2 single-coil ring gyroscope being in agreement with the calculated scale factor value. The gyroscope dead band with upper limit of ≈5.15 deg/s corresponding to the beat-note frequency of ≈15 kHz has been detected during clockwise rotation of the gyroscope. The highest gyroscope resolution of ≈0.01 deg/s=38 deg/h has been estimated on the basis of the bias point drift measurement.

Bidirectional Single Longitudinal Mode Er-Doped Fiber Ring Laser Using a Bandpass Filter and Cascaded Fiber Ring Filter

Bidirectional single longitudinal mode fiber ring laser have advantages and potential in optical sensing, especially angular velocity sensing. The current methods for implementing bidirectional single longitudinal mode fiber ring laser cannot ensure complete reciprocity in the optical path, and the side mode suppression ratio needs to be increased, while the laser linewidth is relatively wide. This paper proposes a combined filtering structure using a bandpass filter and a cascaded add-drop type fiber ring filter. When realizing bidirectional single longitudinal mode output, the optical path structure is fully reciprocal including polarization state reciprocity, while the side mode suppression ratio is relatively high. The linewidth of the bidirectional laser is around 1.1 kHz, far lower than the previous report of tens of kHz. The fully reciprocal combined filter structure proposed in this paper does not require special devices, and its theoretical system is mature, which is conducive to the subsequent application and improvement of bidirectional single longitudinal mode fiber ring laser.

Observation of four self-sweeping regimes in a single-mode bi-directional ytterbium-doped fiber ring laser.

In this work, for the first time, four self-sweeping regimes in a single-mode bi-directional ytterbium-doped fiber ring laser are observed by adjusting the polarization controller (PC): normal self-sweeping, reverse self-sweeping, mixed state, and wavelength stop state. In addition, regulating the PC can artificially selectively make the laser operate in normal self-sweeping or reverse self-sweeping within a certain pump power range, and their self-sweeping characteristics (e.g., sweeping rate, sweeping range, etc.) and intensity dynamics are investigated in detail, respectively. In conclusion, we can flexibly regulate the sweeping direction and sweeping characteristics of the bi-directional self-sweeping fiber ring laser in a simple approach by adjusting the PC, which is potentially valuable for its practical application.

Bi-directional superluminal ring lasers without crosstalk and gain competition

In this paper, we present the experimental observation of simultaneous bi-directional superluminal lasing in a triangular ring cavity without gain competition and crosstalk as needed for realizing a gyroscope based on the Sagnac effect. The gain spectrum for each of the lasers is tailored to be a narrow dip on top of a broad gain using two stable isotopes of Rb. Specifically, we make use of 85Rb to produce a broad gain spectrum via the optically pumped Raman gain process and 87Rb to produce a narrow absorption spectrum via the optically pump Raman depletion process. A separate gain cell is used for the laser in each direction. Inferred from the simulation, the spectral sensitivity enhancements of the clock-wise and counter-clock-wise superluminal ring lasers are ∼362 and ∼505, respectively, with the imbalance attributed to differences in pump powers.

Investigation of a tunable and switchable multi-wavelength bidirectional Brillouin-erbium fiber ring laser

A multi-wavelength bidirectional Brillouin-erbium fiber ring laser with switchable Brillouin frequency spacing (BFS) is proposed and experimentally demonstrated. In the presented Brillouin-erbium ring laser, including an optical amplifier and a highly nonlinear fiber, and without any optical isolator, due to Rayleigh scattering, stimulated Brillouin scattering, and cascaded four-wave mixing initiated successively by the Brillouin pump (BP) light, the odd- and even-order Stokes lines are generated and circulate in the opposite direction in the ring cavity. The BP light and Stokes-induced Rayleigh backscattering light also simultaneously circulate in the ring cavity. Only by adjusting BP power, the gain competition between Brillouin based Stokes and cavity modes’ oscillation can be controlled, the laser output can be conveniently switched between single BFS and odd- or even-order double BFS. In addition, under the certain BP power conditions, the proposed multi-wavelength Brillouin-erbium fiber laser also can realize switchable odd- or even-order Stokes generation and Stokes generation with single BFS, with an increasing wavelength number in turn, only by simply adjusting pump power of the erbium-doped fiber amplifier. Stability and wavelength tunability of the proposed multi-wavelength bidirectional Brillouin-erbium fiber ring laser are also investigated, respectively.

Elastic tape behavior of a bi-directional Kerr-lens mode-locked dual-comb ring laser.

We experimentally investigate a fixed point of a bi-directional dual-comb ring laser and the behavior of dual-comb signals in different spectral regions. We show that the results are quite different from those obtained with traditional dual-comb spectroscopy. We explain the difference using the elastic tape formalism that we apply to a bi-directional ring laser. We also discuss how the results can aid efforts to synchronize two bi-directional laser systems to enable rapid and high-resolution multidimensional coherent spectroscopy with a compact apparatus.

Self-wavelength-sweeping in a bi-directional thulium-doped fiber ring laser

We report for the first time the self-wavelength-sweeping phenomenon of a bi-directional thulium-doped fiber ring laser. The laser wavelength can spontaneously sweep in both lasing directions at a rate up to 0.2 nm s−1 over 15 nm sweeping range in the 1.95 μm wavelength region. The sweeping rate can be controlled by simply changing the state of polarization of the laser cavity. The laser can be tuned to generate a periodical wavelength-swept output with microsecond pulses in the time domain. The sweep rate can also be tuned to zero to give a static lasing wavelength.

Kerr-lens mode-locked bidirectional dual-comb ring laser for broadband dual-comb spectroscopy

Fourier-transform spectroscopy is an indispensable tool for analyzing chemical samples in scientific research as well as the chemical and pharmaceutical industries. Recently, its measurement speed, sensitivity, and precision have been shown to be significantly enhanced by using dual-frequency combs. Moreover, recent demonstrations of inducing nonlinear effects with ultrashort pulses have enriched the utility of dual-comb spectroscopy. However, wide acceptance of this technique is hindered by its requirement for two frequency combs and active stabilization of the combs. Here, we overcome this predicament with a Kerr-lens mode-locked bidirectional ring femtosecond-pulse laser that generates two broadband frequency combs with slightly different pulse repetition rates and a tunable yet highly stable rate difference. Since these combs are produced by one and the same laser cavity, their relative coherence stays passively stable without the need for active stabilization. To show its utility, we demonstrate broadband dual-comb spectroscopy with the single laser.

Simple Phase Control System in Bidirectional Ring Laser

Optical sensors are commonly used and most of them detect the variation of light intensity and then if there is the uctuation of light source intensity or change in propagation loss it causes measurement errors. A ring laser sensor is one of the potential candidates which are insensitive to such uctuation, but it has mainly two problems. One is lock-in effect and the other is insensitiveness to detect the sign (polarity) of the sensing signal. To solve these problems a new phase control system has been proposed. It consists of two polarizers, two quarter-wave plates, and one Faraday rotator. Using this system the phase is controlled by the simultaneous rotation of two quarter-wave plates.

Beam Combining of SOA-Based Bidirectional Tunable Fiber Nested Ring Lasers With Continuous Tunability Over the C-band at Room Temperature

Nested ring cavities are used to develop a simple compact, low-cost semiconductor optical amplifier (SOA)-based bidirectional tunable fiber ring laser source. We propose a bidirectional tunable fiber ring laser structure based on ( N > 1) number of SOAs that has a great potential for achieving a high power laser source that uses low-power optical components by coherently coupling the nested ring cavities. A commercial tunable filter is used to deliver a wavelength tuning range of 30 nm. The lasing tunable range can be further changed by using SOAs with operating wavelengths in different regions of the optical spectrum. The output power of the bidirectional fiber ring resonator with three SOAs was around 3.5 times larger than the output of a single SOA fiber ring laser (i.e., 17.7 versus 5.14 mW) at 1550 nm wavelength. The optical signal-to-noise ratio was measured to be up to +49 dB, wavelength stability was ±0.015 nm, and optical power stability was better than ±0.2 dB.

Generation regimes of bidirectional hybridly mode-locked ultrashort pulse erbium-doped all-fiber ring laser with a distributed polarizer.

We report on the stable picosecond and femtosecond pulse generation from the bidirectional erbium-doped all-fiber ring laser hybridly mode-locked with a coaction of a single-walled carbon nanotube-based saturable absorber and nonlinear polarization evolution that was introduced through the insertion of the short-segment polarizing fiber. Depending on the total intracavity dispersion value, the laser emits conservative solitons, transform-limited Gaussian pulses, or highly chirped stretched pulses with almost 20 nm wide parabolic spectrum in both clockwise (CW) and counterclockwise (CCW) directions of the ring. Owing to the polarizing action in the cavity, we have demonstrated for the first time, to the best of our knowledge, an efficient tuning of soliton pulse characteristics for both CW and CCW channels via an appropriate polarization control. We believe that the bidirectional laser presented may be highly promising for gyroscopic and other dual-channel applications.

Graphene-based passively mode-locked bidirectional fiber ring laser

We present an all-fiber bidirectional passively mode-locked soliton laser with a graphene-based saturable absorber for the first time to the best of our knowledge. Our design includes a four-port circulator to introduce different sections of cavity for the two counter-propagating pulses, so they have distinct output characteristics. Simultaneous bidirectional operation is achieved by appropriately adjusting the net cavity birefringence and loss. In the clockwise direction, the laser emits ~750 fs pulses at 1561.6 nm, with a repetition rate of 7.68 MHz. In the counter clockwise direction, the central wavelength, pulse width, and repetition rate are 1561.0 nm, ~850 fs, and 6.90 MHz, respectively.

Bidirectional Dual-Wavelength Raman Fiber Ring Laser

A new stable dual-wavelength fiber ring laser based on Raman amplification, deploying a dispersion-compensating fiber (DCF) as gain medium, is introduced. The gain competition effects in the fiber Raman amplification are mitigated because the two emission lines, selected by fiber Bragg grating within the resonant ring cavities, travel in opposite directions through the gain medium. The experimental results confirm that the novel multiwavelength ring laser source is stable and it offers a high optical signal-to-noise ratio.

Erratum to: Nucleation of wave defects and formation of optical localized structures in bi-directional ring lasers

Erratum to: Nucleation of wave defects and formation of optical localized structures in bi-directional ring lasers

Bidirectional mode-locked fiber ring laser using self-regenerative, passively controlled, threshold gating

We demonstrate a technique to achieve bidirectional mode locking of a fiber ring laser using two amplitude modulators passively driven by a signal regenerated from the oscillation of the laser itself. The new scheme allows generation of two independent-frequency unlocked-countercirculating pulses and active control of their crossing points. The technique minimizes the effects of the dead band associated with crossing at a scattering media. Results show stable bidirectional pulses at a 5MHz repetition rate with no detectable dead band.

Erratum: Bichromatic emission and multimode dynamics in bidirectional ring lasers [Phys. Rev. A81, 043817 (2010)

Erratum: Bichromatic emission and multimode dynamics in bidirectional ring lasers [Phys. Rev. A<b>81</b>, 043817 (2010)

Nucleation of wave defects and formation of optical localized structures in bi-directional ring lasers

We show that class A bi-directional ring lasers do not support the existence of cavity solitons even under the presence of diffusion for the electromagnetic field. However there is a parameter range where an infinite number of patterns coexist. Such coexistence yields optical localized structures whose dynamical properties are in many ways similar to those of cavity solitons. In particular they allow writing and erasing under the action of very specific perturbations.

Bichromatic emission and multimode dynamics in bidirectional ring lasers

The multimode dynamics of a two-level ring laser is explored numerically using a bidirectional traveling wave model retaining the spatial effects due to the presence of counter-propagating electric fields in the population inversion. Dynamical regimes where the emission in each direction occurs at different wavelengths are studied. Mode-locked unidirectional emission for large gain bandwidth and relatively small detuning is reported.

Could cavity solitons exist in bidirectional ring lasers?

We show numerically that bright and dark cavity solitons can be obtained in bidirectional class A ring lasers only if the phase invariance of the electromagnetic field is broken. The phase invariance symmetry is responsible for the existence of phase waves, which generate long-range interactions destroying the property of independence among otherwise localized structures. We improved the usual model describing such types of lasers, and we prove that it leads to genuine cavity solitons.

Synchronized and unsynchronized chaos in a modulated bidirectional ring laser

Regimes of antisynchronized quasiperiodic and synchronized and unsynchronized chaotic oscillations have been observed in a bidirectional solid-state ring laser with modulated pump and are chracterized in terms of the maximum Lyapunov exponent. The results can be understood in terms of the coupled dynamics of two counterpropagating modes of a ring laser coupled to atomic population inversion.