Showing papers on "Ring laser published in 2013"

Invited Review Article: Large ring lasers for rotation sensing

Abstract: Over the last two decades a series of large ring laser gyroscopes have been built having an unparalleled scale factor. These upscaled devices have improved the sensitivity and stability for rotation rate measurements by six orders of magnitude when compared to previous commercial developments. This progress has made possible entirely new applications of ring laser gyroscopes in the fields of geophysics, geodesy, and seismology. Ring lasers are currently the only viable measurement technology, which is directly referenced to the instantaneous rotation axis of the Earth. The sensor technology is rapidly developing. This is evidenced by the first experimentally viable proposals to make terrestrial tests of general relativistic effects such as the frame dragging of the rotating Earth.

Graphene and nanotube mode-locked fiber laser emitting dissipative and conventional solitons

Abstract: We propose a bidirectional erbium-doped fiber laser mode-locked with a mixture of graphene and single-walled carbon nanotubes for the first time to our best knowledge. The fiber laser can deliver dissipative soliton (DS) and conventional soliton (CS), circulating in opposite directions. The net-cavity dispersion is normal in the clockwise direction and anomalous in counter clockwise direction, respectively, and then DS and CS are generated with the suitable adjustment of attenuators. The output DS and CS approximately have the same central wavelength, but exhibit different optical spectra, pulse durations, and repetition rates. The all-fiber switchable laser can provide two different pulse sources, which is convenient for practical applications.

Widely tunable Vernier ring laser on hybrid silicon

Abstract: A hybrid silicon tunable Vernier ring laser is designed and fabricated by integration of two intra-cavity ring resonators, hybrid III-V-on-silicon gain elements, and resistive heaters for thermal tuning. Thermal tuning of more than 40 nm is demonstrated with side mode suppression ratio greater than 35 dB and linewidth of 338 kHz.

Bidirectional fiber soliton laser mode-locked by single-wall carbon nanotubes

Abstract: We report on the experimental observation of a bidirectional fiber soliton laser passively mode-locked by single-wall carbon nanotubes. Two stable pulse trains in opposite directions are delivered simultaneously from the ring cavity. The counterpropagating pulses have different central wavelengths, pulse durations, and repetition rates. By adjusting the fiber birefringence and cavity length, the central wavelengths of two solitons can be the same or different. Experimental observations and analyses demonstrate that the different operating wavelengths result in the unequal repetition rates of two pulses. These unique features may be attributed to the cavity asymmetry and fiber birefringence.

Switchable Dual-Wavelength PM-EDF Ring Laser Based on a Novel Filter

Abstract: A stable and switchable dual-wavelength polarization-maintaining erbium-doped fiber ring laser is proposed and demonstrated experimentally by using a novel filter, which is formed from dual-pass Mach-Zehnder interferometer incorporating a sagnac loop. By adjusting the polarization controllers, the output laser can be switched between single- and dual-wavelength. The wavelength spacing of the dual-wavelength can be tuned from 0.084 to 4.26 nm. Its 3-dB bandwidth and side mode suppression ratio are less than 0.015 nm and higher than 64 dB, respectively. In addition, the peak power fluctuation and wavelength shift are monitored to be less than 0.5 dB and 0.01 nm during an hour, respectively. The characteristics of the novel filter in experimental measurement accord with the result of theoretical analysis.

Raman-induced noiselike pulses in a highly nonlinear and dispersive all-fiber ring laser.

Abstract: Dual-wavelength noiselike pulses are generated in a fiber ring laser. A first series of pulses is induced at a wavelength of 1550 nm by the interplay of an erbium-doped fiber and nonlinear polarization rotation. From the Raman gain of these pump pulses emerges a second series of Stokes pulses at 1650 nm. With adequate control of the polarization states in the cavity, the noiselike Stokes pulses extend over 84 nm in the Ultralong-wavelengths band (U-band), while the pump pulses span over 46 nm.

Large-area fiber-optic gyroscope on a multiplexed fiber network

Abstract: We describe a fiber-optic gyroscope based on the Sagnac effect, realized on a multiplexed telecom fiber network. Our loop encloses an area of 20 km2 and coexists with Internet data traffic. This Sagnac interferometer is capable of detecting signals that are larger than 10−8 (rad/s)/Hz, thus approaching ring laser gyroscopes without using a narrow-linewidth laser or sophisticated optics. The proposed gyroscope could be useful for seismic applications, opening new possibilities for this kind of optical fiber sensor.

Resonantly pumped monolithic nonplanar Ho:YAG ring laser with high-power single-frequency laser output at 2122 nm

Abstract: We demonstrated a stable single-frequency laser operating at 2122 nm from a monolithic nonplanar Ho:YAG ring oscillator (NPRO). The Ho:YAG NPRO was resonantly pumped by a 1907 nm Tm:YLF laser built up by ourselves. The maximum multimode output power from the Ho:YAG NPRO was 9.66 W and the slope efficiency was 71.7%. With accurate adjustment of the pump position to make the laser oscillate in single frequency condition, an output power of 8.0 W was obtained with a slope efficiency of 61.4% and an optical-optical efficiency of 50.0%. The power stability of the Ho:YAG NPRO laser was 0.29% at maximum single frequency output power. The beam quality M2 factors were measured to be less than 1.1 in x- and y- directions.

Tm 3+ -tb 3+ -doped tunable fibre ring laser for 1700 nm wavelength region

Abstract: The first tunable fibre ring laser in the 1700 nm wavelength region has been developed. To achieve this fibre laser, a Tm3+–Tb3+-doped fibre is used as the active fibre, along with a tunable bandpass filter. A fibre ring laser that consisted of a 1.2/1.7 μm band wavelength division multiplexing coupler, a tunable bandpass filter, an active fibre and one 1.21 μm pump laser diode has been realised. A wide tuning wavelength band of 130.4 nm (from 1635.6 to 1766.0 nm) was achieved with a launched pump power of over ∼ 30 mW. The lasing threshold pump power at 1716 nm was ∼ 9 mW.

An L-band graphene-oxide mode-locked fiber laser delivering bright and dark pulses

Abstract: In this work we have demonstrated the generation of L-band bright and dark pulses from a graphene-oxide (GO) mode-locked erbium-doped fiber laser. The polymer-hosted graphene-oxide saturable absorber (SA) was fabricated by a vertical evaporation method, which permitted a flexible choice of GO concentration and SA thickness. Stable fundamental solitons with a width of ~770 fs and repetition rate of ~21.79 MHz could be directly generated from the laser cavity. The corresponding spectrum was centered at ~1596.0 nm with a 3 dB bandwidth of ~4.454 nm. Triple solitons and fundamentally repetitive dark pulses could also be achieved. By changing the laser cavity design, we also achieved the generation of dark pulses, which had one to three times the repetition rate. The multiple soliton and dark pulse generation were experimentally observed for the first time in such a GO mode-locked fiber laser system, to the best of our knowledge. Our experimental results indicate that the GOSA can be successfully utilized to realize different mode-locked states in the L-band.

Harmonic mode locking counterparts of dark pulse and dark-bright pulse pairs.

Abstract: We have investigated experimentally different operational states of an all-normal-dispersion ytterbium-doped fiber (YDF) ring laser with a long cavity. Various operational states were obtained by adjusting a polarization controller (PC) and the pump power. Self-pulsing, bright pulses, dark-bright pulse pairs and their harmonic mode locking (HML) counterparts, as well as dark pulses and their HML counterparts have all been obtained. Numerical simulations reproduce well the formation processes of dark pulses and dark-bright pulse pairs.

Zig-zag networks of self-excited periodic oscillations in a tunnel diode and a fiber-ring laser.

Abstract: We report numerical evidence showing that periodic oscillations can produce unexpected and wide-ranging zig-zag parameter networks embedded in chaos in the control space of nonlinear systems. Such networks interconnect shrimplike windows of stable oscillations and are illustrated here for a tunnel diode, for an erbium-doped fiber-ring laser, and for the H\'enon map, a proxy of certain CO${}_{2}$ lasers. Networks in maps can be studied without the need for solving differential equations. Tuning parameters along zig-zag networks allows one to continuously modify wave patterns without changing their chaotic or periodic nature. In addition, we report convenient parameter ranges where such networks can be detected experimentally.

A stable single-longitudinal-mode dual-wavelength erbium-doped fiber ring laser with superimposed FBG and an in-line two-taper MZI filter

Abstract: A simple approach to fabricate a stable single-longitudinal-mode (SLM) dual-wavelength erbium-doped fiber ring laser with one superimposed fiber Bragg grating (FBG) is proposed and demonstrated. The superimposed FBG is fabricated by the dual-exposure method for wavelength selection. A home-made in-line two-taper Mach?Zehnder interferometer is incorporated to balance the intra-cavity loss for the wavelengths. The SLM operation is guaranteed by a feedback fiber loop and saturable absorber. A stable dual-wavelength SLM fiber ring laser with a wavelength spacing of approximately 8.53?nm is experimentally realized. The optical signal-to-noise ratio of the laser output is over 50?dB and the linewidth of each wavelength measured by the delayed self-heterodyne method is 9.67?kHz and 9.07?kHz, respectively. The proposed scheme offers the possibility for difference frequency generation of terahertz radiation.

Stable and wavelength-tunable silicon-micro-ring-resonator based erbium-doped fiber laser

Abstract: In this work, we propose and demonstrate a stable and wavelength-tunable erbium-doped fiber (EDF) ring laser. Here, a silicon-on-insulator (SOI)-based silicon-micro-ring-resonator (SMRR) is used as the wavelength selective element inside the fiber ring cavity. A uniform period grating coupler (GC) is used to couple between the SMRR and single mode fiber (SMF) and serves also as a polarization dependent element in the cavity. The output lasing wavelength of the proposed fiber laser can be tuned at a tuning step of 2 nm (defined by the free spectral range (FSR) of the SMRR) in a bandwidth of 35.2 nm (1532.00 to 1567.20 nm), which is defined by the gain of the EDF. The optical-signal-to-noise-ratio (OSNR) of each lasing wavelength is larger than 42.0 dB. In addition, the output stabilities of power and wavelength are also discussed.

Switchable multi-wavelength erbium-doped photonic crystal fiber laser based on nonlinear polarization rotation

Abstract: A multi-wavelength erbium-doped photonic crystal fiber (ED-PCF) ring laser based on nonlinear polarization rotation was demonstrated experimentally. To the best of our knowledge, this study is the first to use a polarization-dependent isolator with an ED-PCF to form an equivalent fiber filter. The intensity-dependent inhomogeneous loss induced by nonlinear polarization rotation was applied to reduce the mode competition caused by ED-PCF. A detailed theoretical analysis using the Jones matrix method to calculate the transfer function of the laser was presented. The theoretical data, which were confirmed by the experimental results, showed that a multi-wavelength with a spacing of approximately 2.26 nm was achieved by controlling the polarization controller. The proposed fiber laser with a signal-to-noise ratio higher than 40 dB achieved a low threshold power of 30 mW. Therefore, stable multi-wavelength outputs with a power fluctuation of less than 2 dB were generated at room temperature.

2.1-watts intracavity-frequency-doubled all-solid-state light source at 671 nm for laser cooling of lithium

Abstract: We present an all-solid-state laser source emitting up to 2.1\,W of single-frequency light at 671\,nm developed for laser cooling of lithium atoms. It is based on a diode-pumped, neodymium-doped orthovanadate (Nd:YVO$_4$) ring laser operating at 1342\,nm. Optimization of the thermal management in the gain medium results in a maximum multi-frequency output power of 2.5\,W at the fundamental wavelength. We develop a simple theory for the efficient implementation of intracavity second harmonic generation, and its application to our system allows us to obtain nonlinear conversion efficiencies of up to 88\%. Single-mode operation and tuning is established by adding an etalon to the resonator. The second-harmonic wavelength can be tuned over 0.5\,nm, and mode-hop-free scanning over more than 6\,GHz is demonstrated, corresponding to around ten times the laser cavity free spectral range. The output frequency can be locked with respect to the lithium $D$-line transitions for atomic physics applications. Furthermore, we observe parametric Kerr-lens mode-locking when detuning the phase-matching temperature sufficiently far from the optimum value.

Controlling the nonlinear intracavity dynamics of large He-Ne laser gyroscopes

Abstract: A model based on Lamb's theory of gas lasers is applied to a He-Ne ring laser gyroscope in order to estimate and remove the laser dynamics contribution from the rotation measurements. The intensities of the counter-propagating laser beams exiting one cavity mirror are continuously observed together with a monitor of the laser population inversion. These observables, once properly calibrated with a dedicated procedure, allow us to estimate cold cavity and active medium parameters driving the main part of the nonlinearities of the system. The parameters identification and noise subtraction procedure has been verified by means of a Monte Carlo study of the system, and experimentally tested on the G-Pisa ring laser oriented with the normal to the ring plane almost parallel to the Earth rotation axis. In this configuration the Earth rotation-rate provides the maximum Sagnac effect while the contribution of the orientation error is reduced at minimum. After the subtraction of laser dynamics by a Kalman filter, the relative systematic errors of G-PISA reduce from 50 to 5 part in 10^3 and can be attributed to the residual uncertainties on geometrical scale factor and orientation of the ring.

Closed-loop locking of an optical frequency comb to a large ring laser.

Abstract: We report on the frequency locking of a 16 m2 ring laser to a single tooth of an optical frequency comb referenced to a hydrogen maser, obtaining a frequency stability of 1 kHz over several days. In common mode operation, where the counterpropagating laser beams run on the same longitudinal mode index, a sensitivity to rotation of 3×10−9 relative to Earth’s rotation is obtained. To test a proposal to bypass time-varying backscatter-induced readout errors in large ring laser gyroscopes, we have operated the laser on adjacent longitudinal cavity modes. The Sagnac frequency due to Earth’s rotation obtained in this fashion was strongly influenced by atmospheric pressure changes because the counterpropagating beams within the cavity are affected differently by geometric cavity fluctuations.

Dark solitons of the power-energy saturation model: application to mode-locked lasers

Abstract: The generation and dynamics of dark solitons in mode-locked lasers is studied within the framework of a nonlinear Schrodinger equation which incorporates power-saturated loss, as well as energy-saturated gain and filtering. Mode-locking into single dark solitons and multiple dark pulses are found by employing different descriptions for the energy and power of the system defined over unbounded and periodic (ring laser) systems. Treating the loss, gain and filtering terms as perturbations, it is shown that these terms induce an expanding shelf around the soliton. The dark soliton dynamics are studied analytically by means of a perturbation method that takes into regard the emergence of the shelves and reveals their importance.

Mode-locked all-fiber ring laser based on broad bandwidth in-fiber acousto-optic modulator

Abstract: Active mode-locking of long-cavity all-fiber ring laser based on broad bandwidth in-fiber acousto-optic modulator (AOM) is reported. The proposed AOM combines the advantages of intermodal coupling induced by standing flexural acoustic waves in a double-ended tapered fiber. We focus our attention on the effects of large tapered transitions to improve the bandwidth modulation. Our approach permits the implementation of broad modulation bandwidth (13 nm), high modulation depth (50 %), and low optical loss (1.1 dB) in an 80-μm configuration. The effects of the AOM in the laser performance are also investigated. Transform-limit optical pulses of 25 ps temporal width and 2.7 W peak power were obtained at 2.46 MHz repetition rate.

A Switchable Erbium Doped Fiber Ring Laser System for Temperature Sensors Multiplexing

Abstract: In this paper, a proof of concept of a switchable erbium-doped fiber ring laser (EDFRL) system that demonstrates temperature sensors multiplexing is carried out showing a high linearity and a sensitivity of 1.55 ${\rm GHz}/^{\circ}{\rm C}$ . The system is based on the detection in the electrical domain of the resulting beat signal of two different laser lines generated by an EDFRL that operates in single longitudinal mode regime (SLM). The SLM operation is achieved by the use of phase shift fiber Bragg gratings with ultranarrow bandwidths of 6 pm. Two independent cavities for the reference signal and sensor signal generation are used to avoid the wavelength competition and to improve the stability. This configuration allows the control of the temperature operation point of the system by adjusting the temperature in the reference side.

Wideband tunable Q-switched fiber laser using graphene as a saturable absorber

Abstract: An ultra-wide wavelength tuning range, which covers three different band regions consisting of the S-, C-, and L-bands, is proposed and demonstrated for a graphene-based Q-switched erbium-doped fiber laser using a tunable bandpass filter as the wavelength tuning and filtering mechanism. A 3 m length of erbium-doped fiber is used as the gain medium in a ring laser cavity configuration, with absorption coefficients of between 11 and 13 dB m−1 at 980 nm and about 18 dB m−1 at 1550 nm. The tuning range of the Q-switching pulses covers a wide wavelength range of 58 nm, which spans from 1512.5 nm to 1570.5 nm. In addition, the lasing and Q-switching thresholds are considerably low, with respective values of ∼11.0 mW and ∼18.4 mW. A repetition rate of 55.3 kHz is obtained at the maximum pump power of 100.4 mW, together with pulse width and pulse energy of 1.6 μs and 25.8 nJ, respectively.

A single-walled carbon nanotube wall paper as an absorber for simultaneously achieving passively mode-locked and Q-switched Yb-doped fiber lasers

Abstract: We demonstrate a fiber ring laser based on a single-walled carbon nanotube (SWCNT) wall paper absorber. It is found that the proposed Yb-doped fiber laser can either be operated in the mode-locked states or Q-switched states. First, SWCNT wall paper acts as a mode locker when the pump power is below 80 mW. Self-started mode locking can be obtained when the pump power is about 47 mW. The proposed Yb-doped mode-locked fiber lasers can be operated in the dissipative soliton regime that the spectra have a narrow peak. Second, SWCNT wall paper acts as a Q switcher when the pump power is above 80 mW. The Yb-doped fiber laser can work in the Q-switched states at higher pump power which is quite different from the conventional pulse fiber lasers. The repetition rate increases from 30 kHz to 50 kHz and the pulse duration decreases from 2.7 μs to 1 μs with the increase of pump power. This is due to the SWCNT wall paper induced loss in the cavity which leads to Q-switched state at higher pump powers. The combination of the Q-switching and mode-locking in one fiber laser have potential application in the fields that require different pulse fiber lasers.

Light extraction – a practical consideration for a plasmonic nano-ring laser

Abstract: An integrated semiconductor plasmonic nano-ring laser with a connecting output plasmonic waveguide for light extraction is proposed, designed and demonstrated numerically The maximum light extraction efficiency can be up to 56% The design was optimized with 2D FDTD and verified with 3D FDTD methods, where close agreement is shown between the two

A stable polarization switching laser from a bidirectional passively mode-locked thulium-doped fiber oscillator.

Abstract: We report on a novel polarization switching laser from a bidirectional passively mode-locked thulium(Tm)-doped fiber oscillator, which was characterized by the periodical change of polarization state of every pulse. The switching laser was created by combing two orthogonally stable vector solitons, which were found to be wave-breaking-free pulses in the all-anomalous-dispersion regime. The measured repetition rates of switching laser and the corresponding vector solitons were 49.596 MHz, 24.798 MHz, and 24.798MHz. By controlling wave plates, either of the polarized pulse trains can be switched on or off. To our knowledge, this is the first report of polarization switching laser with vector solitons in Tm fiber oscillators.

Freestanding nanowire ring laser

Abstract: We demonstrate a freestanding nanowire ring laser, assembled by splicing the two ends of a CdS nanowire via a dissolved polymer nanowire. With ring diameter of less than 50 μm, the free-standing nanowire ring laser shows low lasing threshold, high robustness, and excellent mechanical flexibility. Also, the nanowire ring laser works well in liquid environment, showing the possibility of integrating the nano-ring laser into an optofluidic system.