KEYWORDS: Laser stabilization, Bragg cells, Signal to noise ratio, Control systems, Field programmable gate arrays, Sensors, Optical tweezers, Telecommunications, Semiconductor lasers, Laser systems engineering
Levitated microspheres have enabled a wide variety of precision sensing applications which have caught great attentions in recent years. Optical tweezers technology is one of the most important methods of microspheres levitation. The stability of laser power directly affects the microspheres levitation and the precision of the measurement. This paper discusses the major factors of power stabilization in semiconductor laser. A PID-controlled model is used to control the feedback on the laser. The system mode is established after the analyzing of the characteristic of the model parameters. The experiment is demonstrated with a commercial semiconductor laser. With the external power stabilization module a 16dB laser power stability control is achieved at the relaxation oscillation, and the long-term stability is improved from 3% to 0.4%.
In this paper, we simulate the dynamic movement of a dielectric sphere in optical trap. This dynamic analysis can be used to calibrate optical forces, increase trapping efficiency and measure viscous coefficient of surrounding medium. Since an accurate dynamic analysis is based on a detailed force calculation, we calculate all forces a sphere receives. We get the forces of dual-beam gradient radiation pressure on a micron-sized dielectric sphere in the ray optics regime and utilize Einstein-Ornstein-Uhlenbeck to deal with its Brownian motion forces. Hydrodynamic viscous force also exists when the sphere moves in liquid. Forces from buoyance and gravity are also taken into consideration. Then we simulate trajectory of a sphere when it is subject to all these forces in a dual optical trap. From our dynamic analysis, the sphere can be trapped at an equilibrium point in static water, although it permanently fluctuates around the equilibrium point due to thermal effects. We go a step further to analyze the effects of misalignment of two optical traps. Trapping and escaping phenomena of the sphere in flowing water are also simulated. In flowing water, the sphere is dragged away from the equilibrium point. This dragging distance increases with the decrease of optical power, which results in escaping of the sphere with optical power below a threshold. In both trapping and escaping process we calculate the forces and position of the sphere. Finally, we analyze a trapping region in dual optical tweezers.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.