Abstract: An external cavity laser and a tuning method therefor are provided. The external cavity laser includes a gain chip, and a tunable reflector. The tunable reflector includes a main waveguide, a beam splitter, a first branch waveguide, a first photonic crystal modulator, a second branch waveguide, and a second photonic crystal modulator. The beam splitter is configured to equally split the optical signal transmitted by the main waveguide into a first optical signal and a second optical signal and is configured to transmit the first optical signal to a first branch waveguide and the second optical signal to a second branch waveguide. A first photonic crystal modulator is configured to tune the first optical signal transmitted by the first branch waveguide. A second photonic crystal modulator is configured to tune the second optical signal transmitted by the second branch waveguide.

Abstract: Photon-based radiosurgery is widely used for treating local and regional tumors. The key to improving the quality of radiosurgery is to increase the dose falloff rate from high dose regions inside the tumor to low dose regions of nearby healthy tissues and structures. Dynamic photon painting (DPP) further increases dose falloff rate by treating a target by moving a beam source along a dynamic trajectory, where the speed, direction and even dose rate of the beam source change constantly during irradiation. DPP creates dose gradient that rivals proton Bragg Peak and outperforms Gamma Knife® radiosurgery.

Abstract: The invention relates to a brandnew multi-function static-errorless pressure control method and the valve thereof, in which a cylindrical two-side three-way valve is used as the pilot valve 20 and an asymmetric double-action differential hydraulic cylinder is used as the main valve 10 to constitute an 1-type static-errorless closed-loop negative feedback control system, a transfer means with special oil network connects to the oil circuits 1, 2, 8 and ports 4, 5, 9, L of the system and makes the valve to correspond to six operating modes of the relief valve, remote control relief valve, constant valve pressure reducing valve, constant difference pressure reducing valve, internal control sequence valve and external control sequence valve respectively. The test results have shown that the static error of the pressure control valve of present invention is 0.5%, the overshoot is less than 5%, and no self-excitation is found.