Superfluorescent Source Research Articles

采用混合控制器稳定超荧光光源的输出功率

采用混合控制器稳定超荧光光源的输出功率

Broadband Tm-doped superfluorescent fiber source with 11 W single-ended output power

High-power operation of a cladding-pumped Tm-doped broadband superfluorescent fiber source in the two-micron wavelength regime is described. Predominately single-ended operation was achieved using a simple all-fiber geometry without the use of a high reflectivity mirror or fiber Bragg gratings. The source produced >11 W of single-ended amplified spontaneous emission output spanning the wavelength range from approximately 1930 nm to 1988 nm for a launched diode pump power of approximately 40 W at approximately 790 nm, corresponding to a slope efficiency of 38% with respect to launched pump power. The wavelength spectrum of the superfluorescent source spanned the range from approximately 1650 to 2100 nm with a bandwidth (FWHM) of > 100 nm for output power levels of < 20 mW.

Superfluorescence from Yb- and Yb–Er-doped phosphotellurite glass fibres

Short length, air-clad, multimode fibres were fabricated using high concentration Yb- and Yb–Er-doped phosphotellurite glass. Superfluorescent light sources are obtained by optically pumping the fibres using a 980 nm laser diode. Ytterbium-doped fibre showed amplified spontaneous emission (ASE) in the 1000–1100 nm wavelength region, whereas Yb–Er-codoped fibre in both 1000–1100 nm (due to Yb 3+ ions) and 1450–1650 nm (due to Er 3+ ions) wavelength regions. The ASE spectra from the fibres are compared for different fibre lengths and pump powers. The observed change in the ASE spectral shape and the shift in peak wavelength with the length of the optical fibre is discussed.

Double clad tapered fiber for high power applications

We report a novel type of active fiber - tapered double clad fiber suitable for pumping by low brightness sources with large beam parameter product of 50/300 mm x mrad. Ytterbium double clad all-silica fiber (core/1(st) clad/2(nd) clad diameters 27/834/890 mum, NA(core)=0.11, NA(clad)=0.21), tapered down by a factor 4.8 for a length of 10.5 m was drawn from a preform fabricated by plasma chemical technologies. At a moderate Yb-ion concentration and 1:31 core/cladding ratio, the tapered double clad fiber demonstrates 0.9 dB/m pump absorption at 976 nm and excellent lasing slope efficiency. An ytterbium fiber laser with 84 W of output power and 92% slope efficiency, a 74 W superfluorescent source with 85% slope efficiency and amplifiers operating both in CW and pulsed regimes have been realized. All devices demonstrated robust single mode operation with a beam quality factor of M(2)=1.07.

High-power, single-mode, linearly polarized, ytterbium-doped fiber superfluorescent source

High-power operation of a single-mode, linearly polarized, broadband superfluorescent fiber source has been achieved by using a two-stage cladding-pumped fiber configuration comprising a low power, single-ended, ytterbium-doped superfluorescent fiber seed source and a high-power cladding-pumped, polarization-maintaining, large-mode-area, ytterbium-doped amplifier pumped by a high-power diode source at 976 nm. The source yielded a maximum linearly polarized output of 106 W with a slope efficiency of up to 67% with respect to the launched pump power and with a measured polarization extinction ratio of 13.5 dB. The wavelength spectrum of the superfluorescent source spanned the range continuously from ~1035 to 1100 nm, and the bandwidth (FWHM) of the emission spectrum was 21 nm. The minimum seed power required for an output power over 100 W was only 10 mW, corresponding to an effective power gain in the amplifier stage of 40 dB. Single-spatial-mode operation with a beam propagation factor (M(2))<1.1 was achieved by bending the amplifier fiber to a bend radius of ~8 cm, without a significant reduction in output power.

A new broadband fiber light source for optical coherence tomography

A new type of Gaussian-like broadband superfluorescent fiber light source suitable for optical coherence tomography (OCT) is introduced in this paper. Erbium-doped optical fiber simultaneously pumped by 980nm laser diode (LD) and 1480 nm LD is used as the gain medium. Both optical controllers and temperature controllers are employed to adjust the output of LDs and to improve the stability of output power of light source. A fiber coupler with a specific splitting ratio plus multi-stage long period fiber gratings are used to modulate the output spectrum so that the spectral profile of the broadband light source is near Gaussian. The output power is about 27mW with center wavelength at 1.57μm and the bandwidth over 75 nm. The experiment results reveal that the sidelobes of the autocorrelation function of the output spectrum are effectively suppressed, which can meet the need of optical coherence tomography.

Power Scaling of Ytterbium-doped Fiber Superfluorescent Sources

Power scaling of ytterbium-doped fiber superfluorescent sources based on single-stage and two-stage cladding-pumped fiber configurations is reported. For the single-stage configuration, a novel fiber-end termination scheme was employed to suppress laser oscillation in combination with a simple all-fiber scheme for achieving a predominantly single-ended output. The fiber was cladding-pumped by a diode stack at 976 nm and yielded ~62 W of single-ended amplified spontaneous emission output for 119 W of launched pump power, limited by the onset of parasitic lasing. At pump powers in excess of 40 W, the slope efficiency with respect to the launched pump power was 67%. The emission spectrum spanned the wavelength range from 1030 to 1100 nm and the bandwidth (FWHM) was 12 nm. Scaling to higher power levels was demonstrated using a two-stage cladding-pumped fiber configuration comprising of a low-power fiber superfluorescent seed source and a high-power amplifier. The two-stage source yielded 122 W of amplified spontaneous emission output (limited by available pump power) in a beam with M2 ap 2.1. The slope efficiency for the amplifier with respect to the launched pump power was 77%. The prospects for further improvement in performance and output power are considered.

110 W double-ended ytterbium-doped fiber superfluorescent source with M^2=16

High-power operation of a broadband superfluorescent fiber source has been achieved via the process of amplified spontaneous emission (ASE) in a double-clad Yb-doped multimode-offset-core fiber by using a novel fiber-end termination geometry to suppress lasing. The fiber was cladding pumped by a high-power diode source at 976 nm and yielded a maximum ASE output of 63 and 47 W from the two ends of the fiber, respectively. The maximum combined ASE output was 110 W with slope efficiency with respect to launched pump power of up to 68%. The wavelength spectrum of the ASE source spanned the range from approximately 1032 to 1120 nm, and the bandwidth (FWHM) of the emission spectrum was 40 nm. The output beam was slightly multimode with a beam-quality factor (M2) of 1.6. The prospects for further improvement in performance are considered.

High-power superfluorescent source of Yb3+-doped double-cladding photonic crystal fiber

A new type of high-power broadband superfluorescent source of Yb3+-doped double-cladding photonic crystal fiber is reported experimentally, which is pumped at 976 nm by a high-power laser diode with the end-coupling method. We have obtained a smooth broadband output of superfluorescence. The maximum output power is 1.649 W with a slope efficiency of 56.7%. The 3 dB bandwidth is 22.4 nm. To the best of our knowledge, this is the first report about SFS with such high output power of 1.649 W.

2 W Yb-doped double-clad fiber superfluorescent source with 42 nm 3 dB bandwidth

The output spectrum of Yb-doped double-clad fiber superfluorescent source (SFS) is tailored by placing a broadband dichroic mirror in the pump end of conventional single-pass forward configuration, which constitutes double-pass forward configuration. The 3 dB bandwidth is increased from 11 to 42 nm. A maximum output SFS power of 2.12 W and a slope efficiency of 43.2% are obtained. The double-clad fiber is 25 m and the pump power is adequate to saturate the fiber as far as the feedback-induced lasing appears.

Investigation of Yb3+-doped superfluorescent fibre sources around 105 3nm

Based on theory analysis, we have demonstrated experimentally how to use cascaded wideband fibre Bragg grattings (FBGs) as reflectors in the superfluorescent fi bre sources (SFS) configuration. In the experiment, we investigated the output c haracteristcs of the set-up with cascaded wideband FBGs, and compared it with th ose of the set-up with fibre ring reflector or without any reflector. From what we have achieved in the experiment, we find that the cascaded wideband FBGs is p romising to be used as reflectors in SFS.

Role of an Isolator in Optimization of Forward Conversion Efficiency in an Er-Doped SFS Source at 1.55 μm

By incorporating an isolator at an appropriate location, it is shown that it is possible to realize an efficient single-pass superfluorescent-doped fiber source with a major fraction of its emitted power in the forward direction. A theoretical model to estimate the performance of such a superfluorescent source (SFS) has been suggested and verified with experiments performed on an erbium-doped fiber in a novel pump bypass SFS configuration. Results on design issues such as optimum location of the isolator, pump power requirements, and spectral characteristics are also presented.

Wavelength stability characteristics of a high-power, amplified superfluorescent source

This paper demonstrates a stable, broad-band two-stage superfluorescent source at 1.55 /spl mu/m consisting of an erbium-doped fiber (EDF) seed source and a high-power Er-Yb fiber amplifier. The source exhibited from 140 to 220 mW of power, 18 to 28 nm bandwidth, with an estimated mean wavelength stability from 1 to 10 ppm. Operating conditions for the seed source and amplifier required to achieve these performance characteristics are described.

Fiber-optic gyroscope with suppression of excess noise from the radiation source

A new optical system is proposed and investigated experimentally for a Sagnac fiber interferometer in which the excess noise of the wide-band radiation source is suppressed. A tenfold improvement in the sensitivity of a fiber-optic gyroscope with an erbium/ytterbium fiber superfluorescent light source was achieved experimentally. It is shown that the identity of the polarization characteristics of the interferometer channels plays an important role.

High-power superfluorescent source with a side-pumped Yb-doped double-cladding fiber

A compact superfluorescent source based on an Yb-doped double-cladding fiber amplifier is described. The packaged amplifier is pumped at 975 nm by side-coupling emission from a 2.0-W broad-stripe laser diode through an imbedded V groove. The fiber source generates 485 mW of broadband emission centered at 1055 nm with a 41-nm FWHM flat power spectrum.

Excess noise of an Er/Yb fiber superfluorescent radiation source

A study is made of the noise in the output intensity of a high-power superfluorescent fiber radiation source generating 20 mW in the 1.55 μm region of the spectrum. The source is constructed in an all-fiber technology from a quartz fiber activated with ytterbium and erbium. It is found that the spectral density of the noise in the frequency range 100–500 kHz is uniform and corresponds to the excess noise of “thermal” sources. It is shown that the noise in the output intensity of the source can be compensated (decreased by an order of magnitude) in a two-channel scheme of photodetection, where it approaches a level close to the photon shot noise.

Fabrication and superfluorescence of rare-earth chelate-doped graded index polymer optical fibers

Rare-earth chelate-doped graded index (GI) polymer optical fibers (POF) are proposed and fabricated. The attenuation loss was measured to be 0.4 dB/m at 650 nm for a GI POF doped with 1 wt % of europium (Eu) chelate. Lifetime shortening and spectral narrowing verified the occurrence of superfluorescence at 614 nm in the Eu chelate-doped GI POF pumped with xenon flashlamps. The demonstration of superfluorescence shows that rare-earth chelate-doped GI POFs are appealing as optical amplifiers and superfluorescent sources in a variety of communication and sensor applications.

High power superfluorescent source with stable single-transverse-modeoutput using a multimode Er-doped fibre

A high power superfluorescent Er-doped fibre source with an environment-insensitive single-transverse-mode output is demonstrated using multimode fibre. The efficient fundamental mode selection is explained by strong ground state absorption. The fibres deliver up to ≃770 mW of output power with the highest conversion efficiency of 58%.

Hybrid coherence multiplexing/coarse wavelength-division multiplexing passive optical network for customer access

We propose a passive optical network for customer access based on a hybrid coherence multiplexing/coarse wavelength-division multiplexing (WDM) technique. Coherence multiplexing provides asynchronous multichannel transmission, and coarse WDM provides bidirectional transmission. A cost-shared superfluorescent source is used for downstream transmission, and inexpensive lightemitting diodes are employed for upstream transmission. Asynchronous two channel transmission at 40 Mb/s per channel is demonstrated for both upstream and downstream. Our experiment indicates that upstream and downstream aggregate bit rates of 640 Mb/s are feasible based on current commercially available components.

Efficient superfluorescent light sources with broad bandwidth

We demonstrate various efficient broad band light sources at /spl sim/1-/spl mu/m wavelength with a 3-dB bandwidth of up to 65 nm at 108-mW output power, based on rare-earth doped silica fibers and a simple adjustable spectral filter.