Papers by Keyword: Optical Filter

Abstract: Physics package is the core of rubidium atomic frequency standards (RAFS). In this paper, a physics package of RAFS with enhanced performance is reported. The physics package is designed according to the separated filter scheme, in which an optical filter and a magnetron microwave cavity are used to reduce the white frequency noise and to intensify the resonance signal. The light-shift (LS) and temperature coefficient (TC) can be conveniently adjusted in the separated filter scheme. A preliminary test shows that a frequency stability of the RAFS is less than .

Abstract: By the Transfer Matrix Method (TMM), the properties of defect modes, such as splitting, coupling and filtering, have been researched in detail. The influence of refractive index and incident angle on the defect-mode coupling has been investigated. Simulating results exhibit that coupling mode split as two defect modes when they are close to each other. This property is closely related to the refractive index and the spacing interval between defect layers. The incident angle can reach 30 degree, which has a potential application in full angle filtering.

Abstract: We propose a new optical system that can be used to form the multi-soliton pulses within the micro-ring resonators. The system consists of two micro-ring resonators and an add/drop multiplexer that can be integrated into a single system. The large bandwidth signal is generated by using a soliton pulse propagating in a Kerr-type nonlinear medium. The tuned soliton pulses in either spatial or temporal modes are obtained by using the add/drop multiplexer. Results show the generation of multi-soliton pulses within the micro-ring resonator can be achieved for long distance communication. This results in an increase in the number of channels and spaces with a large free spectrum range (FSR) of 650 pm for dense wavelength division multiplexing (DWDM).

Abstract: By means of the transfer matrix method, transmission spectra and dispersion relationships of photonic crystals (AB) m (CD) n (AB) m (CD) n (AB) m are investigated herein. The number and highness of transmission peaks are found to relate closely with the repeating periodicity n, and (CD)n medium of positive- or negative- refractive index as well. The results may be helpful for designing optical filters of desired properties.

Abstract: The optical filter under development employing frustrated total internal reflection is a micromechanical device containing two silicon rectangular prisms. There is flat silicon plane among hypotenuse edges of the prisms. The silicon plane is a Fabry-Perot resonator, with clearances h1 among the plate and prism edges being its mirrors. Theoretical resolution of the optical filter would be R ≈ 1,5∙103 if h1 = 50 µm and R ≈ 3∙105 if h1 = 100 µm with the thickness of the silicon plane being h = 65 µm; wavelength λ = 100 µm; free spectral region Δλ/λ ≈ 0,3…0,4, transmission in the maximum of spectral characteristics 0,6 (provided input and output silicon prism legs bloom).

Abstract: An on-chip micro-droplet optical filter based on the evanescent wave coupling by fiber taper is presented in this paper. The optical filter consists of a T-junction for micro-droplets generation and an integrated optical fiber taper for light input and output. The light is coupled into the droplet resonator when it has the same wavelengths as the Whispering Gallery Modes (WGMs) of the droplet. The coupling efficiency can be adjusted by tuning the distance between the droplet and the fiber taper using micro fluidic flow. Compared with the solid sphere or ring optical filter using fiber taper coupling, the diameter and refractive index of liquid droplet can be easily tuned, which means the resonant modes can also be tuned. The diameter of the droplet is controlled by the flow rate ratio at the T-junction. The micro-droplet optical filter also has advantages as wide wavelength tuning range, easy fabrication process, simple manipulation, and low cost, which promise for many applications in optical analysis on micro-optical-fluidic chip.

Abstract: In this work, solar-blind UV 4H-SiC avalanche photodetectors were fabricated and tested in linear and Geiger modes. APDs with both PIN and separate absorption and multiplication (SAM) structures were investigated. PIN structures demonstrated higher quantum efficiencies while the SAM structure exhibit lower leakage currents. Deposition of a thin film optical filter on top of the devices was used to provide a high photon rejection ratio of (Stas add value here). However, an external filter showed a better photon rejection ratio compared to the deposited one by about one order of magnitude.

Abstract: In this paper, a promising class of optical filters is introduced, based on Al2O3/PS/Si structure. The filters consist of thin layer of aluminium electrochemically oxidized in different aqueous solution, on porous silicon. The spectral sensitivity can be easily varied by Al2O3 thickness. This result is a consequence of refractive index variation of Al2O3 and PS layers, confirmed by ellipsometry measurements.