Four-wave mixing (FWM) is a well-known technique to achieve all-optical control wavelength conversion. We propose a well-designed silicon nano-waveguide based on silicon-on-insulator (SOI) to achieve FWM conversion. Particularly, the original signal light continuously sweeps along the C band, and the generated idler light is correspondingly sweeping as the original signal is swept. The wavelengths of the idler and signal lights are symmetric with respect to the pump light wavelength. Simulation and experimental results of the FWM conversion properties are well-matched. With the pump light filtered out, a dual-frequency continuously sweeping laser source is achieved, which could be applied in dual-frequency scanning interferometry to eliminate dynamic errors in practical use.
We propose a technique to generate etendue maintained white light. The proposed technique uses three high-power blue light emitting diodes (LEDs) with identical characteristics to pump green aluminate (GAL) green-yellow phosphor coated on the inner channel of a waveguide. The technique offers two methods of generation of white light. Standalone partial conversion of blue to green and yellow light by GAL phosphor, combined with unconverted blue light, produces white light homogenized within the light guide. Complete conversion of blue to green and yellow light with the further addition of blue and red wavelengths from additional LED sources multiplexed with the output is also possible to further increase total white light output. Following design and optical modeling to prove the concept, the proposed technique is demonstrated, which shows white light emissions from the waveguide with no increase in aperture size while the original LED etendue is maintained. The proposed technique offers an alternative to low-lifetime, low-efficiency xenon lamps for light sources in etendue critical applications such as endoscopy.
Eccentric fiber Bragg gratings (EFGBs) in standard single-mode optical fiber by using point-by-point direct writing technique with 800 nm femtosecond laser. The experimental results show that the transmission spectrum amplitude is coupled by Bragg and cladding mode resonance over a wide spectrum range. Meanwhile, the spectral characteristics of EFBGs were studied by adjusting grating period, grating length, laser power and eccentric distance. The eccentric distance is the most essential parameter in terms of inscribing gratings. It can break up the original structural symmetry of the fiber by changing the offset of grating in the fiber core. This change will bring great opportunities and breakthroughs to the application of EFGBs.
The effects of pulse power, filling ratio, number of period and period on the long-period fiber gratings (LPFGs) by using radiation of femtosecond laser. The results show that the strong resonance peaks of LPFGs can be induced and the resonant peaks have different degrees of offset. When the parameters of the LPFG are set to be number of grating period of 70, filling ratio of 0.5, pulse power of 2.0 mW and period of 500 μm, the first resonance peak of LPFG has a blue-shift of 147.3 nm. Furthermore, the size of first resonance peak of LPFG is -19.4 dB. These characteristics of LPFGs provide a favorable opportunity for in-depth research of late-model sensing devices.
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