Dual-wavelength self-mode-locked semiconductor disk laser

Abstract

Dual-wavelength mode-locked lasers can be widely used in optical communication, pump-probe experiment, nonlinear frequency conversion, etc. In this paper, a dual-wavelength self-mode-locked semiconductor disk laser is reported for the first time, to the best of our knowledge. A simple linear resonator is formed by using a high reflectivity distributed Bragg reflector at the bottom of the gain chip, and an external output mirror; the cavity length is about 135 mm, with no need of additional inserted elements. Based on the Kerr effect of the gain medium and the soft aperture formed by the pump spot on the gain chip, along with the fine adjustment of cavity length and pump intensity, the mode-locking process can be started from the free running and the stable self-mode-locking can be realized. The mode-locked pulse width is 4.3 ps, the repetition rate is 1.1 GHz, and the maximum output power is 323.9 mW, which corresponds to a peak power of 68 W. After the laser is mode locked, a readily available blade, which can introduce a wavelength-dependent loss for different laser modes, resulting in a lager cavity loss for a longer-wavelength mode and a smaller cavity loss for a shorter-wavelength mode, is used as a wavelength tuning element, and is inserted into the cavity in the direction perpendicular to the optical axis of the resonator. By changing the depth of the blade inserted into the cavity, the laser wavelength can be continuously tuned from the initial oscillating wavelength (longer-wavelength) to a shorter wavelength, a stable dual-wavelength output with equal intensity can be obtained at a specific position, and the stable continuous-wave mode-locking can be maintained simultaneously. The steady dual-wavelengths in the experiment are 951 and 961 nm, and the corresponding output power is 32 mW. The above dual-wavelength outputs have good coherence since they are stimulated radiations from the same gain chip. Meanwhile, they have relatively high peak power and strictly meet the coaxial conditions, and these are all advantages for the difference frequency generation (DFG). The frequency of the DFG in the experiment is approximately 3.3 THz, which can be widely used in laser radar, remote sensing, homeland security, counter-terrorism, atmospheric and environmental monitoring and otherareas.