Output Coupling Ratio Research Articles

Polarization-maintaining, high-energy, wavelength-tunable, Er-doped ultrashort pulse fiber laser using carbon-nanotube polyimide film

A high-energy, wavelength-tunable, all-polarization-maintaining Er-doped ultrashort fiber laser was demonstrated using a polyimide film dispersed with single-wall carbon nanotubes. A variable output coupler and wavelength filter were used in the cavity configuration, and high-power operation was demonstrated. The maximum average power was 12.6 mW and pulse energy was 585 pJ for stable single-pulse operation with an output coupling ratio as high as 98.3%. Wide wavelength-tunable operation at 1532-1562 nm was also demonstrated by controlling the wavelength filter. The RF amplitude noise characteristics were examined in terms of their dependence on output coupling ratio and oscillation wavelength.

Optimization of output coupling ratio on the performance of a ring-cavity Brillouin-erbium fiber laser

The operation of a single-wavelength Brillouin-erbium fiber laser (BEFL) system with a Brillouin pump preamplified technique for different output coupling ratios in a ring cavity is experimentally demonstrated. The characteristics of Brillouin Stokes power and tunability were investigated in this research. The efficiency of the BEFL operation was obtained at an optimum output coupling ratio of 95%. By fixing the Brillouin pump wavelength at 1550 nm while its power was set at 1.6 mW and the 1480 pump power was set to its maximum value of 135 mW, the Brillioun Stokes power was found to be 28.7 mW. The Stokes signal can be tuned within a range of 60 nm from 1520 to 1580 nm without appearances of the self-lasing cavity modes in the laser system.

Pulse-shaping dynamics controlled by four structural parameters in an all-normal-dispersion mode-locked fiber laser

The characteristics of pulse-shaping dynamics based on four structural parameters in a fiber laser without any dispersion compensation are studied numerically. The simulations show that the four structural parameters, i.e., the location and bandwidth of the spectral filter and the location and output coupling ratio of the output coupler, are crucial for achieving high pulse energy and high pulse peak power in all-normal-dispersion fiber lasers. To obtain high pulse energy and high pulse peak power, optimal positions of the spectral filter and the output coupler inside the cavity are proposed.

Intensity noise of mode-locked fiber lasers

Intensity noise of mode-locked fiber lasers is characterized systematically for all major mode-locking regimes over a wide range of parameters. We find that equally low-noise performance can be obtained in all regimes. Losses in the cavity influence noise strongly without a clear trace in the pulse characteristics. Given that high-energy fiber laser oscillators reported to date have utilized large output coupling ratios, they are likely to have had high noise. Instabilities that occur at high pulse energies are characterized. Noise level is virtually independent of pulse energy below a threshold for the onset of nonlinearly induced instabilities. Continuous-wave peak formation and multiple pulsing influence noise performance moderately. At high energies, a noise outburst is encountered, resulting in up to 2 orders of magnitude increase in noise. These results effectively constitute guidelines for minimization of the laser noise in mode-locked fiber lasers.

被动锁模光纤激光器的耦合输出比

被动锁模光纤激光器的耦合输出比

Dynamics of an ultrahigh-repetition-rate passively mode-locked Raman fiber laser

We present an extended study of an ultrahigh-repetition-rate Raman fiber laser passively mode-locked through dissipative four-wave mixing. We demonstrate mode locking at 100 and 160 GHz repetition rates, corresponding to harmonic frequencies more than 400,000 times the cavity resonance frequency. By varying the output coupling ratio we are able to change the threshold and slope efficiency of the laser. The maximum average output power achieved was 926 mW, a further twofold increase of the output power reported previously for this type of laser. Further numerical analysis reveals that the main factor limiting the pulse quality of our setup is supermode noise. Subsequently, we experimentally investigate the use of all-fiber subcavity Fabry-Perot filters to reduce the noise and demonstrate a significant improvement in the laser operation.

Synchronously pumped optical parametric oscillator based on periodically poled MgOdoped lithium niobate

We demonstrate a room-temperature operation of the near-infrared femtosecond optical parametric oscillator based on MgO-doped stoichiometric periodically-poled lithium niobate, which is synchronously pumped by a Kerr-lens mode-locked Ti:sapphire laser. Wide tunability in the range from 0.98 microm to 1.50 microm was enabled for a single set of cavity mirrors by incorporating a BK7 window as an output coupler. For the output coupling ratio of 3.7%, the threshold pumping power of 460 mW and the slope power conversion efficiency of 37% were achieved. By controlling dispersion values with intra-cavity prisms, femtosecond pulses as short as 66 fs could be obtained.

Efficient coherent combining of tunable erbium-doped fibre ring lasers

Two ring cavity tunable erbium-doped fibre lasers are coherently combined by employing a Mach–Zehnder interferometer in the laser cavity. The combining efficiency is about 95% over the tuning range from 1530 to 1565 nm, which is further improved to be larger than 97% by moving the optical tunable filter from the common arm to the branch arm of the Mach–Zehnder interferometer. The proposed combining scheme is expected to exhibit the potential ability of efficiently combining lasers with different powers and even different output coupling ratios.

Effects of output coupler reflectivity on the performance of a linear cavity Brillouin/erbium fiber laser

The effect of output coupler reflectivity (or output coupling ratio) on the performance of a linear cavity Brillouin/erbium fiber laser (BEFL) is demonstrated. The operating wavelength, output laser power and number of channels vary with changes in the coupling ratio in the linear cavity system. The optimum BEFL operation is obtained with an output coupling of 40%, i.e., 60% of the laser power is allowed to oscillate in the cavity. A stable laser comb consisting of up to 40 channels with line spacings of approximately 0.09 nm are obtained at the Brillouin pump and 980 nm pump with powers of 2.5 mW and 100 mW, respectively. The linear cavity BEFL has the potential to be used in inexpensive wavelength division multiplexing system.

Femtosecond mode-locked Erbium-doped fiber ring laser with intra-cavity loss controlled full L-band wavelength tunability

By using a tunable-ratio optical coupler (TROC) to adjust the wavelength dependent intra-cavity loss, a L-band mode-locked erbium-doped fiber-ring laser (ML-EDFL) is demonstrated for generating wavelength-tunable femtosecond pulses. The change of output coupling ratio introduces different intra-cavity loss and shifts the peak of mode-locked gain profile to provide continuous detuning on wavelength of the ML-EDFL. A maximum tuning range of about 40 nm (from 1565.1 to 1605.3 nm) by decreasing the output coupling ratio from 95% to 5% is obtained, corresponding to a wavelength tuning slope of 2.25 nm/dB. The ML-EDFL exhibits a super-mode suppressing ratio as high as 47 dB and a pulsewidth of <5 ps at repetition frequency of 1 GHz. Nearly transform-limited pulsewidth of 580 fs is generated by linear dispersion compressing the EDFL pulses with a 32.5m-long single-mode fiber under an output coupling ratio of 10%.

L-band erbium-doped fiber laser with coupling-ratio controlled wavelength tunability

By controlling the output coupling ratio, we demonstrate a novel wavelength-tunable L-band Erbium-doped fiber laser (EDFL) with a maximum tuning range up to 58 nm (from 1567 to 1625 nm) by controlling its output coupling ratio between 1% and 99%. The L-band EDFL is configured by using a bi-directionally dual-wavelength pumped EDFA in close-loop with an output coupler of tunable coupling ratio and an air-gap inserted FC/PC connector pair. Such an EDFL exhibits a quantum efficiency of 42% and an ultra-high power conversion efficiency of 37% under optimized pumping scheme, providing the small-signal gain and output power of ~34 dB and 91 mW, respectively. Low variation of <1.2 dB on channel power, power fluctuation of 0.04% and a narrow linewidth of 0.03 nm are obtained.

Output power characteristics of tunable erbium-doped fiber ring lasers

The output power characteristics of a widely tunable erbium-doped fiber ring laser (EDFRL) have been analyzed. The effects of emission wavelength, total intracavity loss, erbium ion clustering, output coupling ratio, and active fiber length are investigated. A comprehensive theoretical model based on a two-level laser model with consideration of pair-induced quenching is proposed. To achieve good performance in an EDFRL, especially for a widely tunable bandwidth of over 100 nm and high slope efficiency, numerical results, which are in good quantitative agreement with the experimental results, indicate that minimization of the intracavity loss as well as optimization of the active fiber length and the output coupling ratio are very important. It is found that the existence of erbium ion clusters in the active fiber can help an EDFRL to emit at a longer wavelength, and hence may be favorable for achieving L-band laser although the output power is reduced and the power flatness is degraded significantly. These findings are useful for the design and optimization of erbium-doped fiber lasers, especially for tunable fiber lasers operating in the longer band or L-band.

High power erbium-doped fiber ring laser with widely tunable range over 100 nm

A high power/slope efficiency erbium-doped fiber ring laser (EDFRL) with widely tunable range over 100 nm is demonstrated by using the combination of a 1480 nm pump laser diode (LD) and a high concentration erbium-doped fiber (EDF). The effects of the length of EDF, output coupling ratio, and pump power on the laser performance are investigated. It is shown that both the length of EDF and the output coupling ratio have the effect on the output power and the tunable range significantly. Optimization of both parameters is necessary for achieving high output power/slope efficiency and large tunable range simultaneously in the EDFRL.

A feedback-injected Fabry–Perot laser diode filtering technique for side-mode suppression and linewidth reduction of erbium-doped fiber lasers

By adding a fiber-pigtailed Fabry–Perot laser diode (FPLD) into a close-loop erbium-doped fiber amplifier (EDFA) ring cavity, and feedback-injecting the FPLD biased at just below threshold and the EDFA each other via directional couplers, we demonstrate a low-cost band-pass filtering technique for constructing narrow linewidth erbium-doped fiber laser (EDFL) with ultrahigh side-mode suppression ratio (SMSR). Under an output coupling ratio of 90%, the mutually injection-locked EDFL–FPLD link exhibits a maximum output power and SMSR of up to 98.6 mW and 49.6 dB at wavelength 1561.37 nm, respectively. Wavelength tuning of up to 6 nm can be achieved by tuning the temperature and fine adjusting the below threshold driven current of FPLD. The minimum spectral linewidth at 3dB-decay of as small as 0.017 nm measuring by commercial optical spectrum analyzer with limited resolution bandwidth of 0.01 nm are observed. The stabilities in power, SMSR, peak wavelength of ±0.01 mW, ±0.5 dB, and ±0.025 nm, respectively, are also determined.

Optical filter design for multiwavelength erbium-doped fiber ring lasers

A model for designing optical filters on multiwavelength erbium-doped fiber ring lasers is proposed. For the given amplifier parameters and output spectrum the model provides the required cavity transfer function, from which the maximum output coupling ratio and the optical filter spectral shape can be obtained. Standard propagation and rate equations of a homogeneous medium are employed for the erbium fiber analysis. The calculated cavity transfer function is tested by analyzing the obtained erbium-doped fiber ring laser employing a previously presented model. The effectiveness of the method is tested with a nine-line signal on the 1525–1565 nm range.

Output characteristics of tunable fiber ring-laser:modeling and experimentation

Output characteristics of a tunable fiber ring laser are studied both by theoretical modeling and by experimentation. Dependencies of laser output power on lasing wavelength, pump power, erbiumdoped fiber (EDF) length, output coupling ratio, and intracavity loss are demonstrated by using a simple theoretical model. It is shown that a wide tunable range over 130nm (i.e.1500—1630nm) can be obtained through parameter optimization. As a result, the laser with a tunable range up to 100nm, high output power, and high signaltonoise ratio in most of the tunable range has been achieved in experimentation. The experimental data are in good agreement with the theoretical modeling results.

Numerical analysis of Yb3+-sensitised, Er3+-doped, fibre-ring laser

The performance of a Yb/sup 3+/-sensitised Er/sup 3+/-doped, continuous-wave, fibre-ring laser is analysed using a comprehensive numerical model. The model is based on iterative solution propagation-rate equations and takes account realistic refractive-index profile and Er/sup 3+//Yb/sup 3+/-doping distribution function, uniform upconversion from the /sup 4/I/sub 13/2/ erbium level and propagation of amplified spontaneous emission in the pump wavelength range. The dependence of output power on active fibre length, input pump power and output coupling ratio has been investigated. The analysis has shown that the laser can be tuned in the range 1525 nm - 1610 nm. The calculated ring-laser characteristics have been found in quantitative agreement with the experimentally obtained data.

A variable reflectivity output coupler for optically pumped far infrared lasers

In this paper we describe the design and performance of a variable reflectivity output coupler for optically pumped far infrared (FIR) lasers. The output coupler is a compact, tunable Michelson interferometer. The output coupling ratio (i.e. the Michelson transmission) is adjustable between 0 and ≥60% for laser line wavelengths between 110 and 500 μm. This output coupler provides increased output power and flexibility, since it can be tuned to optimum coupling ratio for different laser lines. Beam profile measurements show that the Michelson output coupler produces a well collimated Gaussian laser beam.

WB6 - DF-CO2transfer laser development

Power extraction and chemiluminescence experiments have been conducted in the large-scale DF-CO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> transfer chemical laser (TCL) (IRIS-I and IRIS-II) facility at Bell Aerospace Company (BAC). The modular design of the device allowed testing to be conducted with both a supersonic nozzle bank and also in subsonic flow with sonic injection for the deuterium. Power levels of 15 kW at 10.6 μ were obtained in IRIS-I (subsonic) employing an unstable resonator with a 50-percent output coupling ratio and cavity pressure of 35 torr. For IRIS-II (supersonic) somewhat lower power was obtained. In both systems the fluorine dissociation (α = F/F + 2F <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> ) was less than 0.01. Chemi-luminescent emission from HF and DF was monitored under zero-power conditions along an axis parallel to the laser-mirror axis. From the measured DF-concentration profiles it can be inferred that vibrationally excited DF is being produced throughout the cavity and, accordingly, the production of DF must be attributed largely to the chain reaction.