The researchers put forward precise requirements for the laser pointer parameters of the 589 nm yellow laser light source in optogenetic applications:
1) Because it is a study of living organisms, the light power intensity and width should be moderate (too long acting time will destroy cell tissues and cause irreversible damage). After satisfying the stimulation of neurons, photosensitivity can be achieved and specific biological behaviors can be controlled. At the same time, it is also required that the power consistency of the laser should be good, the stability should be high, and the fluctuation of the collected biological response current data is small, which is convenient for the scientific researcher to extract the data for analysis later.
2) At the same time, the laser is required to have a modulation function, which should have a modulation response of the order of ms. In high-end applications, in order to maintain a stable laser power and a fast modulation speed at the same time, a fiber modulator is usually added to solve the corresponding problem.
3) The laser is required to have fiber coupling output, and the laser is required to have high beam quality, and the coupling system should match the fiber core diameter and NA value to achieve efficient fiber coupling. The size of the light spot that the optical fiber acts on the neuron needs to be controlled. When it acts on a certain neuron circuit, a better behavioral response can be achieved. If the light spot is too large, it acts on multiple neuron circuits and stimulates the behavior of different areas at the same time, which may lead to the disappearance of the controlled biological behavior, so it is also more important to choose an appropriate irradiation area.
4) The green laser pointer must meet multi-step program control such as pulse amplitude modulation, variable duty cycle modulation, and variable interval modulation to realize the control of the biostimulation mode.
Application in sodium guide star. The resolution of large ground telescopes cannot reach the theoretical diffraction limit due to the interference of atmospheric turbulence, and adaptive optics correction technology is needed to compensate for the distorted wavefront to improve imaging quality and clarity.
When observing a darker target, the adaptive optics system also needs a bright point light source to sample the atmosphere. Generally, a natural star is selected near the observation target. In recent years, the rapid development of laser guide star technology can provide artificial guide stars for large telescopes, greatly expanding the detection range and imaging quality of the telescope, and it has become a necessary system for large-scale telescopes abroad.