Superfluorescent Source Research Articles

Mid-infrared all-fiber superfluorescent source in Er3+-doped fluoride fiber

We report, to the best of our knowledge, the first mid-infrared (MIR) all-fiber superfluorescent source based on a superfluorescent seed and a single-stage amplifier. A 7.8-m-long section of highly-Er3+-doped fluoride fiber is used in the superfluorescent seed and a 4.3-m-long section of lightly-Er3+-doped fluoride fiber acts as the amplifier. Two home-made MIR pump-signal combiners based on side-pumping technology are fabricated directly on two sections of gain fiber. By direct-low-loss fusion splicing of two kinds gain fiber, the power of MIR superfluoresescence main output is amplified to 0.35 W and the power of rear output is amplified to 0.2 W. The output spectrum under maximum power spans from 2680 nm to 2880 nm with 20 dB bandwidth of 60 nm. The measured time domain and output beam profile show that this superfluorescent source keeps relatively stable in microsecond time scale without self-pulsing effect occurrence and has near single-mode gaussian characteristic. This works provides a new way for MIR superfluorescent source, which is of practical interest in a range of applications.

The future of quantum technologies: superfluorescence from solution-processed, tunable materials

Abstract One of the most significant and surprising recent developments in nanocrystal studies was the observation of superfluorescence from a system of self-assembled, colloidal perovskite nanocrystals [G. Rainò, M. A. Becker, M. I. Bodnarchuk, R. F. Mahrt, M. V. Kovalenko, and T. Stöferle, “Superfluorescence from lead halide perovskite quantum dot superlattices,” Nature, vol. 563, no. 7733, pp. 671–675, 2018]. Superfluorescence is a quantum-light property in which many dipoles spontaneously synchronize in phase to create a collective, synergistic photon emission with a much faster lifetime. Thus, it is surprising to observe this in more inhomogenous systems as solution-processed and colloidal structures typically suffer from high optical decoherence and non-homogeneous size distributions. Here we outline recent developments in the demonstration of superfluorescence in colloidal and solution-processed systems and explore the chemical and materials science opportunities allowed by such systems. The ability to create bright and tunable superfluorescent sources could enable transformative developments in quantum information applications and advance our understanding of quantum phenomena.

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.

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.

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.

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.

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.

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.

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.

1.08 kW Narrowband All-Fiber Super-Fluorescent Source with Spectral-Broadening-Free Property

1.08 kW Narrowband All-Fiber Super-Fluorescent Source with Spectral-Broadening-Free Property

Optimization investigation for high-power 1034 nm all-fiber narrowband Yb-doped superfluorescent source

An optimization for all-fiber narrowband Yb-doped superfluorescent source with a central wavelength shorter than 1040 nm is conducted theoretically and then verified experimentally using steady-state rate equations. Theoretical investigation indicates that with the increase in fiber length, signal power presents one peak value, but the ratio of signal power to output power is decreasing monotonously. Moreover, a filter with high extinction ratio and a gain fiber with high absorption coefficient can have gain suppression on a long wavelength. One all-fiber superfluorescent source is built experimentally on the basis of the theoretically optimized parameters. The source achieves an output power of 214.64 W with a central wavelength of 1034.18 nm and signal–noise ratio of 30 dB. The output power of the source can have further power scaling with considerable available pump power.

Coherence length of a Yb fibre superfluorescent source with an adjustable linewidth

Characterization of coherence for superfluorescent light emitted from a diode-pumped Yb-doped fiber source is reported. We have constructed a superfluorescent light source with an adjustable linewidth employing a Yb-doped fiber master oscillator and two power-amplifier stages and measured its coherence length as a function of a linewidth in a Michelson interferometer. The experimental values are in good agreement with the numerically calculated values using the given spectral intensity distribution. The results indicate that the mechanism for linewidth broadening of the fiber superfluorescent output can be attributed to inhomogeneous line broadening of an atomic transition. The prospect of the fiber superfluorescent source with a tailored coherence length will be discussed.

30 W all-fiber tunable, narrowband Yb-doped superfluorescent fiber source

An all-fiber tunable, narrowband superfluorescent source is presented by using tunable seed source and two amplification stages. The output power reaches over 30 W with the tuning range of ∼35 nm (from ∼1045 to ∼1080 nm) and the slope efficiency in the final amplifier is about 67%. At the maximum output power, the full width at half maximum is about 0.7 nm and the signal-noise ratio reaches over 25 dB. More output power can be realized by simply adding pump source. To the best of our knowledge, it is the first time to use all-fiber configuration to realize the tunable output at 1 μm superfluorescent fiber source region.

Study on the power scalability of all-fiber superfluorescent source operating near 980 nm.

The high-power all-fiber superfluorescent source operating near 980 nm is studied experimentally and numerically. In experiment, an all-fiber superfluorescent source operating near 980 nm is fabricated with the distributed side-coupled cladding-pumping (DSCCP) Yb-doped fiber (YDF). By optimizing the active fiber and angle-cleaving of the output port, a recorded 17.1-W output power and 14.6% slope efficiency of 980-nm ASE are obtained. No parasitic laser oscillation is observed at the maximum output power. The power scalability of the source is also numerically investigated. A simple but effective method is present to numerically determine the threshold of parasitic laser oscillation. It is found that the output power can be scaled up to 50 W and 100 W with the optical feedback of each output port suppressed to 1.2 × 10-6 and 7 × 10-7, respectively. It is also revealed that coupling coefficient should be larger than 6 to realize more than 50% slope efficiency. These results provide significant guidance for understanding and designing the high-power superfluorescent Yb-doped source (SYFS) operating near 980 nm and other sorts of three-level fiber sources.

Experimental study on high-power all-fiber superfluorescent source operating near 980 nm

A high-power all-fiber superfluorescent source operating near 980 nm is experimentally studied with the help of a large-core distributed side-coupled cladding-pumped Yb-doped fiber. By optimizing the active fiber length and the angle cleaving of the output fiber facet, a 10 W all-fiber superfluorescent source operating near 980 nm is demonstrated for the first time, to the best of our knowledge. An 11.4 W combined 980 nm ASE power is obtained with a 9.3% slope efficiency and an 18 dB suppression of the ASE around 1030 nm. The output spectrum spans 973 nm to 982 nm with the 3 dB bandwidth around 3.5 nm. A 10.5 W output power with 13.1% slope efficiency is also obtained by changing the length of the active fiber. The variations of the output power and spectrum with the active fiber length and pump power are also investigated in the experiment.

Demonstration of multi-Watt all-fiber superfluorescent source operating near 980 nm* *Project supported by the National Natural Science Foundation of China (Grant No. 61405249).

The superfluorescent Yb-doped fiber source operating near 980 nm is studied. The design requirement is theoretically discussed aiming to suppress the amplified spontaneous emission around 1030 nm in the 980-nm superfluorescent fiber source. Based on the theoretical study, a multi-Watt, all-fiber, bi-directional, pumped, superfluorescent source operating near 980 nm is designed and experimentally demonstrated for the first time, to the best of our knowledge. The recorded 8.38-W combined output power is obtained with a 3-dB bandwidth about 3.5 nm. The power scaling of the 980-nm superfluorescent fiber source is limited by the parasitic laser oscillation.

Radiation resistance of an Er/Ce codoped superfluorescent source of conventional fiber and photonic crystal fiber

A superfluorescent fiber source (SFS) with the low Ge-doped and Er/Ce codoped photonic crystal fiber (ECPCF) is proposed to improve the radiation resistance of SFS. The radiation effects of SFSs for an Er/Ce codoped conventional fiber (ECF) and a low Ge-doped and ECPCF are investigated in a Co60 gamma-ray environment. Results show that the low Ge-doped photonic crystal fiber exhibits better radiation tolerance than its counterpart in the Er/Ce codoped fibers, and the attenuation of the power of ECPCF-SFS is significantly smaller than that of ECF-SFS. In addition, the radiation-induced spectral variation of ECPCF-SFS with increased radiation dose is less than that of ECF-SFS. ECPCF-SFS simultaneously exhibits higher recovery performance than ECF-SFS.

Stimulated Brillouin scattering suppression of thulium-doped fiber amplifier with fiber superfluorescent seed source.

We investigate the stimulated Brillouin scattering (SBS) effect in high-power thulium-doped fiber amplifier seeded with a narrow-linewidth fiber superfluorescent source or a conventional narrow-linewidth fiber laser. No random backward SBS pulses are observed when using a narrow-linewidth fiber superfluorescent source as the seed. The corresponding average power and peak power reach 153 W and 3.4 kW, respectively, only limited by the available pump power. This gives the average power and peak power extraction from the thulium-doped fiber amplifier with 17 fold enhancement, in comparison with the situation using the conventional narrow-linewidth fiber laser with similar central wavelength and spectral linewidth as the seed. This work indicates that using low coherent fiber superfluorescent sources is a good solution for power scaling in narrow-linewidth fiber amplifier system in order to overcome the limitation of SBS effect.

Studies of central wavelength of high-power all-fiber superfluorescent sources with Yb-doped double-clad fibers

The behavior patterns and dependencies of the central wavelength of high-power all-fiber superfluorescent sources (SFS) were studied based on the steady-state rate equations of Yb-doped fiber lasers. The relationships between the central wavelength and the pumping power as well as the fiber parameters including fiber length, core size, core/clad ratio, and absorption coefficient were analyzed based on the gain coefficient of the gain fiber. Experimental results from ten different fibers are presented, and the results agreed well with the simulations. The central wavelength of the ten SFSs ranged from 1034.75nm to 1072.4nm.

10.8 kW spectral beam combination of eight all-fiber superfluorescent sources and their dispersion compensation.

We report an 8-element spectral beam combination of Yb-doped all fiber superfluorescent sources around 1070 nm wavelength. Each source consists of a 60 mW front-end and a 1.5 kW three-stage fiber amplifier chain. The eight output beamlets are spectrally combined using a home-made polarization-independent multilayer dielectric reflective diffraction grating. 10.8 kW output power is achieved with an efficiency of 94%. Besides, both theoretical and experimental studies of dual grating dispersion compensation scheme have been performed, which is proved to be a prospective way for high brightness spectral beam combination.