Mode scrambler

About: Mode scrambler is a research topic. Over the lifetime, 896 publications have been published within this topic receiving 13595 citations.

Experimental study of a slot antenna excited by a TE011 mode coaxial cavity

Abstract: A slot antenna is developed to excite the high harmonic waveguide mode for generating large-area plasmas. This antenna consists of a TE011 mode coaxial cavity with the axial slots positioned on equal interval on the inner wall. The waves radiated from those slots can excite the high harmonic mode in the central area. With the azimuthal symmetric wave field of the TE011 mode, the number of the slots can be chosen to match the field pattern of the high harmonic mode. In this report, the dispersion relation of the coaxial waveguide, the coupling scheme and the mode competition of the cavity are studied. A method has been successfully developed to suppress the TE121 mode which is the most competing mode to the TE011 mode.

Hybrid Square-Rectangular Laser for Mode $\pmb{Q}$ -Factor Control and Single Mode Operation

Abstract: Hybrid square-rectangular lasers capable of mode control are proposed and fabricated. Single mode and unidirectional emission operation are obtained with a side-mode suppression-ratio up to 46 dB and single-mode-fiber coupling loss of 3.2 dB.

Mode Partition Noise In Nearly Single Mode Lasers With Multiple Side Modes

Abstract: The power penalty estimation for fiber optic communication due to mode partition noise in nearly single mode lasers is discussed. Nearly single mode lasers are modeled here as those with a single dominant mode and n side modes with significant strength. The dropout rate of each side mode obeys exponential distribution. The combined distribution of the dropout rate for n side modes is derived here. This distribution is combined with the statistically independent Gaussian receiver noise in estimating error probability and hence the power penalty. Calculations show that to ensure a 10 -12 error rate, the ratio of the main mode to the side modes must be greater than 57:1 for one side mode and greater than 67:1 for two side modes.

Phase-Disturbing Speckle-Suppressing by Contact Fiber Scrambler

Abstract: To measure the focal ratio degradation of astronomical fibers, we use laser as the light source which can do with bringing the light to a focal point and we can control the injection position. The laser has a high coherency and there are a number of modes in the large-core fiber. Consequently, the output spot will be a speckle. The presence of speckle makes the energy distribution of optical field uneven, so that it's hard to calculate the spot radius. To reduce the influence of the speckle, the contact-type mode scrambler is developed in our research. It's used to make the fiber vibrate at a suitable frequency of 0-80 Hz, and the vibration amplitude is 0.5 cm. The phase of different propagation modes is changed randomly in order to vibrate the modes and reduce the influence of the speckle. Different vibration result is observed by setting different vibration frequency and different CCD exposure time. The estimate of the vibration result can be given by using the method of contrast and Fourier Transform. Three different core diameters (10µm, 125µm, 320µm) are contrast with each other for convenience. The result shows that the vibration frequency between 65-70 Hz is best, and the optimum exposure time is 30 ms for all three diameters. The vibration of fiber using mode scrambler can reduce the speckle obviously under coherent illumination.