[en] Upconversion luminescence characteristics of a multi-rare-earth-doped 0.05K₂O-0.1ZnO-0.1BaO-0.2PbO-0.2GeO₂-0.35TeO₂ glass have been investigated under 976 nm excitation for potential use in full colour displays. Two luminescence ions, Er³⁺ and Tm³⁺, were used as blue, green and red emitters to control the colour of the emitted light. Sensitizer ions, Yb³⁺, were used to increase the upconversion emission intensity. With the substitution of Er³⁺ for Tm³⁺, the intensities of the blue, green and 657 nm upconversion emissions simultaneously increase

[en] We report on an effective and universal technique to fulfill intensity noise suppression for single-frequency fiber lasers (SFFLs) at 1.5 μm. Utilizing a gain-saturated semiconductor optical amplifier and the effective filtering of amplified spontaneous emission, the resultant relative intensity noises of three diverse SFFLs are maintained at −155 dB Hz⁻¹; which is only <0.9 dB from the shot noise limit in the frequency range from 100 kHz to 50 MHz. Refering to the three paradigmatic experimental results, this technology, as a promising external solution of noise suppression, can be modularized to promote the application of SFFLs. (paper)

[en] We demonstrate an optoelectronic feedback method to simultaneously reduce the intensity and frequency noise of a single-frequency phosphate fiber laser for the first time. Based on the fact that the intensity and frequency noise in this laser mainly originate from the pump power fluctuations, we implement a simple and compact feedback loop and achieve a maximum noise reduction of over 20 dB for the intensity noise at frequencies of 0.3–3 kHz and 10 dB for the frequency noise at around 1 kHz. In addition, the laser instability is improved from ±1.7% to ±0.1%, and the laser line shape is observed to be compressed at the central part. (paper)

[en] A novel linearly frequency modulated narrow linewidth single-frequency phosphate fiber laser has been demonstrated. The output power of the laser is more than 40 mW. A maximum frequency excursion of more than 700 MHz at the modulating bandwidth of 1 kHz has been achieved. Single longitudinal mode operation under modulation is confirmed and the linewidth of the laser is measured to be less than 2 kHz. This type of laser source shows real promise for applications in coherent optical frequency domain reflectometry. (letter)

[en] The photonic generation of tunable microwave signal from a dual-wavelength distributed-Bragg-reflector (DW-DBR) highly Er³⁺/Yb³⁺ co-doped phosphate fiber laser is presented. Microwave signals centered at ∼15, ∼22 and ∼25 GHz with <10 kHz linewidth were obtained. The laser cavity of the fiber laser consists of a dual-channel narrowband fiber-Bragg-grating (DC-NB-FBG), a 0.4-cm-long Er³⁺/Yb³⁺ co-doped phosphate fiber and a wideband FBG (WB-FBG). The wavelength selecting gratings are spatially separated to create partially separated resonant cavities. Er³⁺/Yb³⁺ co-doped phosphate fiber ensures that mode competition is relative weak under low pump power. The short cavity length and the DC-NB-FBG ensure that only one longitudinal mode is supported by each reflection peak. Dual-wavelength single-frequency lasing with laser linewidths of <4 kHz is achieved. (letter)

[en] A compact frequency-modulation Q-switched single-frequency fiber laser is demonstrated at 1083 nm. The short linear resonant cavity consists of a 12 mm long homemade Yb"3"+-doped phosphate fiber and a pair of fiber Bragg gratings (FBGs) in which the Q-switching and the frequency excursion is achieved by a tensile-induced period modulation. Over 375 MHz frequency-tuning range is achieved with a modulation frequency varying from tens to hundreds of kilohertz. The highest peak power of the output pulse reaching 6.93 W at the repetition rate of 10 kHz is obtained. (paper)

[en] A thorough investigation of the effect of amplified spontaneous emission (ASE) on the noise characteristics of a heavily Yb-doped phosphate fiber single-frequency laser at 1083 nm was made. Both the intensity noise and the frequency noise were measured and analyzed by introducing a band pass filter (BPF) into the fiber laser. For the intensity noise, it was found that the ASE noise is present at frequencies beyond the resonant relaxation oscillation (RRO) and until 6 MHz at low pump intensity, while it is diminished in the high power regime. Under a pump power of 42 mW, a maximum reduction of over 3 dB of the relative intensity noise (RIN) was observed with the help of the BPF. As for the frequency noise, a transition of the dominating noise sources from ASE noise in the low pump intensity condition to pump noise in the high pump intensity condition was observed. In the low power condition, more than 7 dB of the ASE noise was found to add to the frequency noise spectrum. It is believed that the obtained results will be helpful in understanding and optimizing the noise characteristics of this type of fiber laser. (letter)

[en] We demonstrate an experimental investigation on the linewidth of a single-frequency Yb-doped phosphate fiber laser through a loss-compensated recirculating delayed self-heterodyne (LC-RDSH) method at 1.0 μm. A resolution of 3 kHz is achieved by only using a 6 km fiber delay line in the linewidth measurement system. With optimal parameters of the LC-RDSH system, more than 16 orders of beat note are detected. By analyzing the behaviors of different orders of beat note, a broadening effect on the linewidth is observed with an increasing pump strength of the under-tested fiber laser. Associated with theoretical analysis, the frequency noise incorporated with the linewidth broadening is shown to be the attribution of the Lorentzian noise. Frequency noise of the laser is also measured, to verify the observed linewidth characteristics. To the best of our knowledge, this is the first time that the LC-RDSH has been applied to the 1.0 µm window. (paper)

[en] An all-fiber Yb-doped kHz-linewidth low-noise linearly polarized single-frequency master-oscillator power-amplifier (MOPA) laser with a stable CW output power of >52 W is demonstrated. By suppressing the intensity noise of the DBR phosphate fiber oscillator, the linewidth of MOPA laser is not noticeably broadened, and an ultra-narrow linewidth of <3 kHz is obtained. Furthermore, the low-noise behavior of MOPA lasers is investigated. A measured relative intensity noise of < −130 dB Hz"−"1 at frequencies of over 2 MHz, a phase noise above 1 kHz of <5 μrad/Hz"1"/"2, and a signal-to-noise ratio of >63 dB are achieved. (paper)

[en] A continuously spacing-tunable multi-wavelength single-frequency fiber laser (MW-SFFL) at 1.06 μm is investigated based on cascaded four-wave mixing (CFWM) in a high-nonlinearity photonic crystal fiber (HN-PCF). By using two separate wavelength-tunable continuous-wave (CW) SFFLs for pumping the HN-PCF, the MW-SFFL with up to ten stable wavelengths is generated under a total pump power of 890 mW. Furthermore, when the wavelength and the power of pump lasers are appropriately manipulated, the wavelength spaces of the MW-SFFL can be tuned freely within 166 pm and the numbers of wavelengths can be controlled to 4, 6, 8, and 10, respectively. To our knowledge, it is demonstrated for the first time that the MW-SFFL based on CFWM at 1.0 μm band are directly excited by CW SFFLs. (paper)