A power efficient optical frequency comb (OFC) is highly desired for applications with limited power supply, e.g., microwave photonics applications in moving vehicles. An ultraflat OFC generation is demonstrated with 0.19-dB flatness, 15 comb lines, and 18.3-dBm total RF power consumption. The scheme is based on spectral convolution. A five-line comb with 0.06-dB flatness and 4.0-GHz spacing is first generated in an intensity modulator. Then the signal is injected to a phase-modulator driven by ×5 frequency of 20.0 GHz to obtain the ultraflat 15-line comb with 0.19-dB flatness. The comb spacing is adjustable by controlling the input frequency of microwave source within the bandwidth of phase-modulation. Our work demonstrates a power efficient approach to obtain ultraflat comb and may benefit microwave photonics applications requiring low-power consumption.
We report a tungsten diselenide (WSe2) polyvinyl alcohol (PVA)-based, saturable absorber and related experiment results of a Q-switched fiber laser. WSe2-PVA film is synthesized by liquid phase exfoliation method, and its saturable absorption is measured via a nonlinear transmission experiment. The result shows that WSe2-PVA saturable absorber has a modulation depth of 3.5%, which means it has potential for generating an ultrafast pulse laser. We apply this absorber into a ring-cavity erbium-doped fiber laser and obtain Q-switched pulses under appropriate pump power. Our work demonstrates the reliable nonlinear optical characteristics of WSe2 and the feasibility for this two-dimensional material to be applied in the field of nonlinear optics.
Mode-locked fiber lasers with low timing jitter and high repetition rate is desired for various applications including
photonics analog-to-digital conversion, microwave synthesis and high-precision clock distribution. We demonstrate a
compact all fiber laser mode locked by semiconductor saturable absorber mirror with linear cavity. The laser is operating
near 1.55 μm. It has a repetition rate of 250 MHz and the root-mean-square timing jitter is 8 fs integrated from 100 Hz to 1 MHz measured at the third harmonic frequency of 750 MHz.
A novel ring fiber laser based on Er-doped photonic crystal fiber (EDPCF) is demonstrated. EDPCF is used as gain
medium to implement stable CW operation. The laser output wavelength can be continuously tuned over the range from
1529 to 1535 nm by adjusting the polarization state of the light inside the cavity. Stable dual-wavelength CW operation
is also observed with proper settings of the intracavity polarization controllers. The laser stability in terms of the output
power and the operation wavelength is characterized, and less than ±0.05 dB power fluctuation as well as 18 pm
wavelength perturbation are obtained.