We demonstrate and analyze a novel self-mixing laser particle sizing instrument using a He-Ne laser centered at around
632.8 nm and output power is 35 mW. A single mode fiber is used to deliver the incident light to the sample cell and the
fiber probe is worked as an optode. The scattered light is collected by the same fiber and re-injected into the laser.
Experimental investigations are presented for particle sizing using polystyrene particles in water from 100 to 400 nm in
diameter. Diameter of the scattering particle can be obtained by analyzing the optical power spectrum which is related to
the autocorrelation of the measured scattering intensity. The result has a good agreement with theory. As a significant
improvement, we gather the back-scattering light using a fiber optic probe accomplishes a task that is almost impossible
using conventional optics because the multiple scattering in a concentrated opaque suspension. Fiber optics also has the
advantages of being less prone to damage, less expensive and allowing for remote access in transmitting and collecting
The micro-actuator with the torsion beam and the cantilever beam on silicon is designed and analyzed, which is actuated by electrostatic force. Based on the torsion dynamics theory, the technique and relative formula are presented for analyzing the actuating voltage and the switching time, on which the effect of the air squeeze film damping is already considered. The optimized results of the structural parameters are compared between this technique and the finite element modeling (FEM). The optimized result of parameters is as: length, width and thickness of the torsion beam are 700, 12, and 10μm, length and width of the cantilever beam are 1900 and 1000μm, length and width of the balance beam are 100 and 1000μm, and distance of the upper and lower electrodes is 55 μm, respectively. The actuating voltage is about 50 V, and the switching time T off and T on are about 5 and 12 ms, respectively. The computed results show that the air squeeze film damping is an important factor for the study of dynamic response on micro-actuator. Finally, an optical technique is described for the measurement of the actuating voltage and switching time of the device, and the difference between the experimental results and theoretical datum is discussed.
Trapezoid index modulation (TIM) is introduced in long period fiber grating to decrease the index change. The coupled-mode equations of long period grating with trapezoid index modulation have been presented. The coupled interactions considered in these equations include not only the self-coupling of the core mode and the coupling between the fundamental core mode and the cladding modes, but also the self-coupling of the cladding modes. Compared with the long-period fiber grating with rectangle index modulation (RIM), the advantage of this novel grating is that it needs a smaller refractive index change. The value of refractive index change decreases with the increasing of the difference between the top width and the bottom width. When the difference between the top width and the bottom width is 30 μm, the refractive index change is only 80.2% of that of the long-period fiber grating with rectangle index modulation. Trapezoid index modulation can also be applied to the fiber Bragg and sampled grating to decrease the refractive index change. Sixteen uniform channels filtering with small refractive index change are also demonstrated.
The MOEMS 2×2 optical switch with slant lower electrode and with torsion beam on silicon is designed and analyzed theoretically. Analytical formulae for the squeeze film damping coefficient and the squeeze film damping moment on the cantilever beam of the optical switch are derived. Based on the torsion dynamics theory, the technique and relative results are presented for analyzing the actuating voltage and the switch time. The optimized result of parameters is as: length, width and thickness of the torsion beam are 700, 12 and 10 um, length and width of the cantilever beam are 1900 and 1000 um, length and width of the balance beam are 100 and 1000 um, shortest spacing between the upper and lower electrodes is 0.05 um, and highness of the lower electrode is 55 um, respectively. The actuating voltage is less than 10 V, and the switching time of Ton and Toff are 1.30ms and 1.25ms, respectively. The computed results show that the air squeeze film damping is an important factor for the study of dynamic response on MOEMS optical switch.
The diffraction characteristics are analyzed for a polymer arrayed-waveguide grating (AWG) multiplexer around the central wavelength of 1.55 μm with the wavelength spacing of 1.6 nm. The diffraction loss and diffraction efficiency in the input and the output slab waveguide are investigated and discussed for different values of parameters, such as the core width, pitch of adjacent waveguides, the number of arrayed waveguides, taper end width of waveguides, and number of output wavelength. Finally, we give a set of parameters which have been optimized in this device.