The power scaling of an all-solid-state visible laser is limited by the mode-to-pump ratio related to the thermal effect based on the spatial rate equation. The mode-to-pump ratio is also known as the overlap efficiency factor (OEF). We investigated the thermal effect as a function of pump power, the waist radius of pump beams, and the waist position of pump beams and have simulated the three-dimensional distribution of the OEF as a variable of the waist position and size of pump beams. Also, it is seen that the calculated optimal OEF under a plane–concave cavity is a decreasing function of input pump power, and it is less than unity in the case of high pump power. The practical example of a Pr:YLF laser pumped by 9-W fiber-coupled laser diodes confirms our theoretical analysis. The output power instability was < ± 1 . 625 % (RMS) within 1 h. In addition, by changing the cavity length to 38 mm, the output power of 607 nm is up to 103 mW with an OEF of 0.741.
Mode-locked erbium-doped fiber lasers (EDFL) with the low repetition rate and high pulse energy play an important role in many fields, such as micromechanical processing, ophthalmic surgery, biological sample detection, and LiDAR detection. However, in the 1550 nm band, due to the anomalous dispersion and nonlinear effects of erbium-doped fiber lasers (EDFLs), it is difficult to achieve mode-locked pulses especially in long cavities, which brings many difficulties to engineering applications. We analyze and simulate the pulse formation and evolution process in a mode-locked EDFL at a low repetition rate of sub-megahertz. The results show that by decreasing the gain or increasing modulation depth/saturation light intensity of saturable absorber in a specific range, a stable single-pulse mode-locked state can be achieved. Then a multipulse mode-locked state can be achieved by gradually increasing the gain or decreasing the saturation light intensity. In addition, the pulse width can be compressed by adjusting the second-order dispersion coefficient. The numerical simulation results are instructive for the design and development of EDFL at a low repetition rate of sub-megahertz.
The nonlinear effect of fiber limits the further increase in pulse energy, and Mamyshev oscillator shows outstanding advantages in managing nonlinearity in waveguide medium, which is now associated with high peak power and high pulse energy. The potential applications of these laser sources based on Mamyshev mechanism have facilitated aggressive research and innovative ideas by researchers around the world. Here, we focus on the mode-locked principle and starting dynamics of Mamyshev oscillator. The review of Mamyshev technology is summarized from two starting modes of seed source injection and self-starting. Initial research and significant progress in this field, plus new insights and challenges of Mamyshev oscillator for ultrafast fiber laser technology are analyzed.
A 37-core optical fiber with 14 air holes is proposed in this paper. This optical fiber can transmit the fundamental mode and part of the second mode. Effects of structure parameters on effective refractive index, bending loss and effective area of the fundamental mode HE11 and the second-order mode HE21 are investigated systematically. By adjusting the structure parameters, at wavelength of 1550 nm and bending radius of 5 cm, the effective mode field area of the fundamental mode is 1776.289 μm2 , and the bending loss is 4.656×10-5 dB/m. Due to the flexibility of multi-core structure, it is significant for theoretical research and practical manufacturing.
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