Superfluorescent Fiber Source Research Articles

Influence of the average wavelength on the scale factor stability of interferometric fiber optic gyroscope

The introduction of closed-loop mechanisms has significantly enhanced the performance of interferometric fiber optic gyroscopes (IFOGs). However, the poor scale factor (SF) stability limits its further application due to the use of broadband light sources. This study first reviewed the impact of the average wavelength of a light source on SF stability in a closed-loop IFOG setup. A simulation model is developed according to modulation and demodulation principles, and the SF error is found to be proportional to the wavelength drift in a closed-loop IFOG. Additionally, employing a laser with a more stable average wavelength instead of a super fluorescent fiber source (SFS) for driving the IFOG enhanced the SF stability by an order of magnitude to 0.38 ppm in ambient-air experiments, which is one of the best SF performances achieved thus far. With the significant improvement in stability during the variable temperature tests, the IFOG measures rotation rates more accurately.

Coherence-tailorable vector fiber source

Apart from the polarization and spatial mode, the degree of coherence (DoC), as a new degree of freedom (DoF), has actuated the control of structured optical fields beyond into a higher dimension. However, the control of DoC mainly focuses on the spatial coherence, and so far, there are no reports on the modulation of temporal coherence of the structured light. Here, a temporal coherence-tailorable vector fiber source is proposed and experimentally demonstrated. With a two-mode long-period fiber grating and polarization control, switchable transverse-mode outputs including azimuthally polarized mode TE01 and radially polarized mode TM01 are performed in an all-fiber compact regime. Benefitting from a tunable superfluorescent fiber source as the illumination of spatial mode control, the temporal coherence and the operating wavelength of vector beams can be simultaneously modulated. This work may not only advance a considerable protocol for creating and manipulating high-dimensional vectorial optical field, but also open up a promising avenue for potential applications in optical communication, high-resolution imaging, and particle trapping.

Influence of wavelength, linewidth, and temperature on second harmonic generation of a superfluorescent fiber source.

Low-coherence tunable visible light sources have a wide range of applications in imaging, spectroscopy, medicine, and so on. Second harmonic generation (SHG) based on a superfluorescent fiber source (SFS) can produce high-brightness visible light while retaining most of the characteristics of superfluorescent sources, such as low coherence, low intensity noise and flexible tunability. However, due to the limitations in phase matching conditions, SHG based on SFS is difficult to reach an equilibrium between high efficiency and robustness of phase matching to temperature variation. In this paper, based on a spectral tunable SFS, we provide a comprehensive analysis, both experimental and theoretical, of the impact of wavelength, linewidth, and temperature on the output performance of SHG. Our findings indicate that broader linewidths adversely affect conversion efficiency, yet they enhance the capacity to withstand temperature variations and central wavelength detuning, which is an advantage that traditional SHG methods do not possess. This work may pave the way for utilizing low-coherence visible light in domains and extreme environments where robust output stability becomes imperative.

Temperature Dependence of Spectral Properties of Yb-Doped Superfluorescent Fiber Source

Temperature Dependence of Spectral Properties of Yb-Doped Superfluorescent Fiber Source

Experimental investigation of high-power broadband all-fiber nanosecond superfluorescent source

In this work, we demonstrate a broadband nanosecond superfluorescent fiber source (ns-SFS) with an average power of several hundred watts and an adjustable repetition frequency of 25 kHz–100 kHz. To figure out a suitable active fiber length for ns-SFS seed, the impact of active fiber length on the output spectrum of SFS is investigated theoretically and experimentally. The results indicate an evident redshift in the central wavelength of output spectrum with increasing fiber length. By scaling the power of the ns-SFS seed employing three amplifier stages, the maximum average power and pulse energy are obtained with a value of 463 W, 17.6 mJ, respectively. To the best of our knowledge, this work is the first demonstration of a broadband ns-SFS amplifier with output power exceeding hundred watt and pulse energy exceeding 10 mJ.

All-fiberized linearly polarized superfluorescent fiber source with 5 kW power output.

A superfluorescent fiber source (SFS) is a special fiber source that commonly possesses high temporal stability and a wide spectral linewidth. In this work, an all-fiberized linearly polarized SFS with, to our knowledge, record output power and near-diffraction-limited beam quality is presented. Up to 5.03kW SFS is achieved at a pump power of 6.18kW with a corresponding conversion efficiency of ∼81.1%. At maximum output power, the signal-to-noise ratio to background spectral noise is over 50dB, the polarization extinction ratio is ∼17d B, and the beam quality factor is M x 2=1.49, M y 2=1.44. Further comparisons confirm the power scalability of fiber amplifiers employing SFSs as seed lasers. Overall, this work could provide a good reference for potential exploration of high-power fiber laser systems.

Improvement of the Temperature Stability of the Erbium-Doped Superfluorescent Fiber Source by Tuning the Reflectivity of the Fiber End

A novel and simple way of improving the mean wavelength temperature stability of the erbium-doped superfluorescent source is described and demonstrated. We show that by introducing small reflectivity feedback at the unpumped fiber end in the backward-pump superfluorescent source configuration, we can affect an overall temperature dependency of the mean wavelength of the output spectrum. The reflectivity adjustment can be made by an angled fiber cleave, varying the reflectivity between 0 to 4 %, or by a fusion arc, allowing its finer adjustment. With this approach, we were able to arbitrarily adjust the mean wavelength temperature trend from −4.38 to 5.23 ppm/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{\circ }$</tex-math></inline-formula> C. Furthermore, an optimal reflectivity was attained, providing almost zero trend and reducing the total mean wavelength variation to 130 ppm over the temperature range of −40 to +100 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{\circ }$</tex-math></inline-formula> C, which is a 5.7-fold and 4.4-fold improvement compared to 0 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{\circ }$</tex-math></inline-formula> and a standard 8 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{\circ }$</tex-math></inline-formula> fiber cleave angle, respectively. By avoiding any filtering components, a wide bandwidth of 37.8 nm and a power efficiency of 22% was reached. Since the proposed configuration does not include any extra components compared to the basic backward-pump configuration, it can be a viable solution for cost-efficient applications, such as, e.g., medium-grade fiber-optic gyroscopes. A benefit for these gyroscopes is the tunability of the source wavelength temperature dependency which can conveniently compensate the gyro coil temperature sensitivity.

Experimental investigation of the stimulated Raman scattering effect in high-power nanosecond superfluorescent fiber source

Abstract In this work, we experimentally investigate the dependence of the stimulated Raman scattering (SRS) effect on the seed linewidth of a high-power nanosecond superfluorescent fiber source (ns-SFS). The results reveal that the SRS in the ns-SFS amplifier is significantly influenced by the full width at half maximum (FWHM) of the ns-SFS seed, and there is an optimal FWHM linewidth of 2 nm to achieve the lowest SRS in our case. The first-order SRS power ratio increases rapidly when the seed’s linewidth deviates from the optimal FWHM linewidth. By power scaling the ns-SFS seed with the optimal FWHM linewidth, a narrowband all-fiberized ns-SFS amplifier is achieved with a maximum average power of 602 W, pulse energy of 24.1 mJ and corresponding peak power of 422.5 kW. This is the highest average power and pulse energy achieved for all-fiberized ns-SFS amplifiers to the best of our knowledge.

Mid-infrared side-pumping combiner and all-fiber superfluorescent fiber source (invited)

Mid-infrared side-pumping combiner and all-fiber superfluorescent fiber source (invited)

2.3 W, Linearly-Polarized Superfluorescent Generation From a Polarization-Maintaining Er3+-Doped Fluoride Fiber Amplifier Around 2.8 μm

We present a high-power, polarization-maintaining (PM) Er <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> -doped fluoride fiber amplifier, which enables watt- level, linearly-polarized (LP) superfluorescent outputs around 2.8 μm by using a non-PM Er <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> -doped fluoride fiber superfluorescent source (FSS) after polarization controlling as the seed. Based on an optimized scheme, the gained superfluorescent signal with a 20 dB bandwidth of 95 nm (2710∼2805 nm) can yield a maximum power of 2.32 W and a polarization extinction ratio (PER) of up to ∼23.6 dB. To our knowledge, this is the first demonstration of a mid-infrared (mid-IR) PM fiber amplifier, and the power also represents, until now, the highest level from a FSS in the mid-IR. Further power scaling is only limited by the seed power, and can be anticipated by boosting seed power or/and adopting multi-stage amplification. This work provides an alternative way for high-power, LP, mid-IR FSS, enabling a range of real-world applications.

3 kW power-level all-fiberized superfluorescent fiber source with linear polarization and near-diffraction-limited beam quality.

In this paper, we demonstrate a high-power linearly polarized all-fiberized superfluorescent fiber source (SFS) with near-diffraction-limited beam quality. The laser system is based on a master oscillator power amplifier configuration, which mainly consists of a polarization-maintained (PM) broadband SFS and multistage PM fiber amplifiers. A linearly polarized fiber laser over 3 kW is obtained at a pump power of about 4.3 kW with the corresponding slope efficiency of 71.9%. The polarization extinction ratio and the beam quality (M2 factor) of the output laser are about 12.7 dB and 1.18, respectively, at the maximum output power. To the best of our knowledge, this is the highest output power of a linearly polarized broadband SFS with near-diffraction-limited beam quality.

Correlation between emission and relative intensity noise spectral profiles of an Er-doped fiber superfluorescent source

The spectral characteristics of the relative intensity noise (RIN) of two amplified spontaneous emission (ASE) sources are experimentally measured. An Er-doped fiber superfluorescent source (EDF-SFS) is investigated and compared with a super-luminescent diode (SLD) source, using a simple tunable fiber Bragg grating filter-based system. Experimental results based on normal ASE operation conditions showed that the RIN distribution of the EDF-SFS is correlated with its emission spectral profile, which is different from the results observed using the SLD source. This finding shows for the first time that an EDF-SFS based ASE has fundamentally different RIN characteristics from other known existing spontaneous emission broadband sources. The amplifying process of the EDF-SFS is discussed and confirmed using a rate equation-based simulation.

Influence of temperature on detectable minimum rotation rate in i-FOGs using Er-doped SFSs

Abstract In this study, an interferometric fiber optic gyroscope (I-FOG) model exploiting the double-pass backward (DPB) erbium-doped superfluorescent fiber source (SFS) with both thin-film filter (TFF) and fiber bragg grating (FBG) reflectors has been constructed and the effects of temperature variations on mean wavelength and detectable minimum rotation rate (DMRR) have been theoretically analyzed. the simulations corresponding with the relations between these parameters for temperature variations in the range of −60 °C to + 90 °C, have been performed using Matlab 2021b. DMRR variations have been found as 6.01 ppm/K and 3.83 ppm/K for the system with TFF, whilst they are 15.31 ppm/K and 1.58 ppm/K for the system with FBG.

Experimental study on the impact of signal bandwidth on the transverse mode instability threshold of fiber amplifiers.

In this work, we conduct a detailed experimental study on the impact of signal bandwidth on the TMI threshold of fiber amplifiers. Both the filtered superfluorescent fiber sources and the phase-modulated single-frequency lasers are employed to construct seed lasers with different 3 dB spectral linewidths ranging from 0.19 nm to 7.97 nm. The TMI threshold of the fiber amplifier employing those seed lasers are estimated through the intensity evolution of the signal laser, and different criteria have been utilized to characterize the spectral linewidth of the seed lasers. Notably, the experimental results reveal that the TMI threshold of fiber amplifiers grows, keeps constant, and further grows as a function of spectral linewidth of seed lasers. Our experimental results could provide a well reference to understand the mechanism of the TMI effect and optimize the TMI effect in high-power fiber amplifiers.

Polarization stabilization of the mean wavelength of erbium-doped super fluorescent fiber optic sources

We investigate the influence of polarization on the stability of a single-pass fiber super fluorescent light source (SFS) operating under the forward or reverse setup. The measurement of amplified spontaneous emission (ASE) spectra obtained using different values for the power and state of polarization (SOP) of the optical pump (980 nm) is the basis of the analysis. The mean wavelength was the stability evaluation criterion used for comparing the forward and backward SFS emission. The results indicate that both super fluorescent sources become insensitive to the polarization state when the pump power reaches a saturated absorption condition. The influence of the SFS spectral range is also analyzed, defining four spectral bands; Ctot band (1520–1570 nm), C band (1530–1560 nm), C+ band (1520–1540 nm), and C− band (1540–1560 nm). We show that the stability of the SFS improves by discriminating one of the two peaks of the ASE emission spectrum, reaching the performance required for inertial grade sensors.

Comparisons of kilowatt Yb-Raman fiber amplifiers employing a superfluorescent fiber source and fiber oscillator.

In this paper, we demonstrate experimental investigations on kilowatt-level Yb-Raman fiber amplifiers (YRFAs) employing a superfluorescent fiber source (SFS) or a multi-longitudinal mode fiber oscillator (OSC) as the Raman-pump laser. Through comparing the output properties of the two YRFAs, the experimental results reveal that the YRFA employing the SFS is superior to the YRFA employing the OSC in the performances of power scalability and narrow-linewidth operation. Meanwhile, about 1.16 kW Raman-signal laser at 1120 nm is obtained through the YRFA employing the SFS as the Raman-pump laser. Overall, the presentation could provide an effective solution for the design of high-power narrow linewidth YRFAs.

Watt-level superfluorescent fiber source near 3 µm.

We report a watt-level mid-infrared (mid-IR) superfluorescent fiber source from ${{\rm Er}^{3 +}}$-doped ZBLAN fiber near 3 µm spectral range. With the power amplifier configuration, the mid-IR superfluorescent fiber source with power up to 1.85 W has been delivered successfully with slope efficiency about 18.6%. The experimental results may pave an avenue toward a high-power, high-temporal-stability superfluorescent source for versatile mid-IR applications.

Compact and low-cost superfluorescent fiber source assisted narrow linewidth Yb-Raman fiber amplifier.

Recent work has shown that temporally stable optical sources are required in a narrow linewidth Yb-Raman fiber amplifier to suppress the spectral broadening phenomenon. Superfluorescent fiber sources (SFSs) with different spectral widths are used as the Raman-pumped lasers in a 200-watt level narrow linewidth Yb-Raman fiber amplifier for the first time to the best of our knowledge. The experimental results reveal that the spectral broadening phenomenon could be well controlled by using the broadband SFS. Therefore, the narrow linewidth operation could be well maintained during the power scaling process. Moreover, the suppression of the spectral broadening phenomenon would deteriorate when the spectral width of the SFS decreases. This work could provide a compact, low-cost choice for the Raman-pumped laser in narrow linewidth Yb-Raman fiber amplifiers.

2-kW-level superfluorescent fiber source with flexible wavelength and linewidth tunable characteristics

Abstract The superfluorescent fiber source (SFS) with tunable optical spectrum has shown great application potential in the sensing, imaging, and spectral combination. Here, we demonstrate for the first time a 2-kW-level wavelength and linewidth tunable SFS. Based on a flexible filtered SFS seed and three stages of fiber amplifiers, the output power can be scaled from the milliwatt level to about 2 kW, with a wavelength tuning range of 1068–1092 nm and a linewidth tuning range of 2.5–9.7 nm. Moreover, a numerical simulation is conducted based on the generalized nonlinear Schrödinger equation, and the results reveal that the wavelength tuning range is limited by the decrease of seed power and the growth of amplified spontaneous emission, whereas the linewidth tuning range is determined by the gain competition and nonlinear Kerr effects. The developed wavelength and linewidth tunable SFS may be applied to scientific research and industrial processing.

High power, tunable, ultra-narrowband Yb-doped superfluorescent fiber source operating at wavelength less than 1055 nm with 20 nm tuning range

Tunable, narrowband superfluorescent fiber sources (SFSs) are significantly important for spectral combination. Here, we propose a high power, tunable, ultra-narrowband Yb-doped SFS operating at wavelength less than 1055 nm with 20 nm tuning range. The system is composed of a broadband SFS, a home-mode space-to-fiber tunable spectral filter, and a three-stage amplifier chain. In order to achieve three typical characteristics, namely, operating in the shorter wavelength region (SWR) with wide spectrum, tunable and narrowband, and high-power output, the performance of the system is investigated and optimized based on the rate equations with temperature, grating monochromator and the coupling theory of Gaussian beam between fibers. Theoretical investigation indicates that a broadband SFS operating in the SWR with wide spectrum can be achieved by controlling temperature within a certain range. Moreover, by optimizing space-to-fiber tunable spectral filter, the tunable, ultra-narrowband SFS with linewidth of 0.088 nm can be obtained. In addition, the seed laser with signal to noise ratio (SNR) of more than 30 dB and the appropriate length of active fiber can gain better amplification performance from the main amplifier. Based on these optimized parameters, a high power, tunable, ultra-narrowband Yb-doped SFS has been built experimentally. The output power of narrowband SFS operating in tunable range from 1035 nm to 1055 nm exceeds 300 W with M2 factor of 1.47, and the measured full width at half maximum and SNR of which are less than 0.1 nm and beyond 30 dB, respectively. This work extends the spectral region and capacity of narrowband SFSs, and will be useful for further power scaling of spectral beam combination.