We have successfully generated a 1.3/1.4 µm random fiber laser (RFL) using bismuth (Bi)-doped phosphosilicate fiber. The Bi-doped RFL has shown excellent long-term operational stability with a standard deviation of approximately 0.34% over 1 h at a maximum output power of 549.30 mW, with a slope efficiency of approximately 29.21%. The Bi-doped phosphosilicate fiber offers an emission spectrum ranging from 1.28 to 1.57 µm, indicating that it can be tuned within this band. Here, we demonstrated a wavelength-tuning fiber laser with a wavelength of 1.3/1.4 µm, achieved through the using of a fiber Bragg grating or a tunable filter. Compared to traditional laser sources, the RFL reduces the speckle contrast of images by 11.16%. Due to its high stability, compact size, and high efficiency, this RFL is highly promising for use in biomedical imaging, communication, and sensor applications.

In this paper, we propose a temperature-sensing scheme utilizing a passively mode-locked fiber laser combined with the beat frequency demodulation system. The erbium-doped fiber is used in the laser ring cavity to provide the gain and different lengths of single-mode fibers inserted into the fiber ring cavity operate as the sensing element. Different temperature sensitivities have been acquired in the experiment by monitoring the beat frequency signals at different frequencies. The experimental results indicate that the beat frequency shift has a good linear response to the temperature change. The sensitivity of the proposed sensor is about -44 kHz/°C when the monitored beat frequency signal is about 10 GHz and the ratio of the sensing fiber to the overall length of the laser cavity is 10 m/17.5 m, while the signal-to-noise ratio (SNR) of the monitored signal is approximately 30 dB. The proposed temperature-sensing scheme enjoys attractive features such as tailorable high sensitivity, good reliability, high SNR, and low cost, and is considered to have great potential in practical sensing applications.

Conventional ultrashort pulsewidth measurement technology is autocorrelation based on second-harmonic generation; however, nonlinear crystals and bulky components are required, which usually leads to the limited wavelength range and the difficult adjustment with free-space light alignment. Here, we proposed a compact all-fiber pulsewidth measurement technology based on the interference jitter (IJ) and field-programmable gate array (FPGA) platform, without requiring a nonlinear optical device (e.g., nonlinear crystal/detector). Such a technology shows a wide measurement waveband from 1 to 2.15 µm at least, a pulsewidth range from femtoseconds to 100 ps, and a small relative error of 0.15%–3.8%. In particular, a minimum pulse energy of 219 fJ is experimentally detected with an average-power-peak-power product of 1.065×10-6W2. The IJ-FPGA technology may offer a new route for miniaturized, user-friendly, and broadband pulsewidth measurement.

We demonstrate a 2080 nm long-wavelength mode-locked thulium (Tm)-doped fiber laser operating in the dissipative soliton resonance (DSR) regime. The compact all-fiber dumbbell-shaped laser is simply constructed by a 50/50 fiber loop mirror (FLM), a 10/90 FLM, and a piece of large-gain Tm-doped double-clad fiber pumped by a 793 nm laser diode. The 10/90 FLM is not only used as an output mirror, but also acts as a periodical saturable absorber for initiating DSR mode locking. The stable DSR pulses are generated at the center wavelength as long as 2080.4 nm, and the pulse duration can be tunable from 780 to 3240 ps as the pump power is increased. The maximum average output power is 1.27 W, corresponding to a pulse energy of 290 nJ and a nearly constant peak power of 93 W. This is, to the best of our knowledge, the longest wavelength for DSR operation in a mode-locked fiber laser.

The direct generation of passively Q-switched lasers at a green wavelength has rarely been investigated in the past. In this Letter, we demonstrate a passively Q-switched praseodymium-doped yttrium lithium fluoride green laser at 522 nm using CdTe/CdS quantum dots as a saturable absorber. A maximum average output power of 33.6 mW is achieved with the shortest pulse width of 840 ns. The corresponding pulse energy and peak power reached 0.18 μJ and 0.21 W, respectively. To the best of our knowledge, this is the first demonstration in regard to a quantum dots saturable absorber operating in the green spectral region.