Narrow-band Fabry-Perot Research Articles

Characterization of Birefringent Titanium-Oxide Thin Films Deposited by DC Sputtering

This work presents the characterization of birefringent properties of titanium-oxide thin films using spectrophotometry and double-cavity Fabry-Perot structures. All films were deposited by DC sputtering over tilted substrates and the birefringence was characterized as a function of the deposition angle by the numerical difference between the refractive indexes for s- and p-polarized light beams. As a result, the highest value of birefringence (0.03) was obtained for samples tilted at 21º (having the normal axis as reference). A polarizing narrow-band Fabry-Perot filter centered at 400 and 700nm was designed by means of numerical simulations of the multilayer structures using a MATLAB© toolbox to solve the classical optical equations. Using this designed double-cavity Fabry-Perot structure [Ag(40nm) / TiO2(160nm) / Ag(40nm) / TiO2(164nm) / Ag(40nm)], transmittance ratios (Tp/Ts) for p- and s-polarized light beams resulted 1.70 at a wavelength of 699nm and 1.36 at another wavelength of 393nm (centers of the two narrow-band peaks), which corroborated the birefringent characteristics of the nearly-stoichiometric titania (TiO2) thin films.

Towards an on-chip optical microsystem for spectroscopic detection of gastrointestinal dysplasia

This paper presents a CMOS optical microsystem with a 4 × 4 photodiodes array and their readout electronics, based on 16 light-to-frequency converters, and 16 high selective optical filters, for spectrophotometric measurement of diffuse reflectance and fluorescence signals, applied to the detection of gastrointestinal dysplasia. The photodiodes array is based on n+/p-epilayer junction silicon photodiodes. Their readout electronics outputs a digital signal, with a frequency proportional to the photodiode current, featuring a sensitivity of 26 Hz/nA at 550 nm, a spectral resolution of 9 MHz and a power consumption of 1 mW. The optical filters are based on 16 thin-film narrow-band Fabry-Perot resonators, in which dielectric mirrors are used. They feature high transmittances and low full-width-half-maximum. Experimental measurements, using phantoms representative of the main absorbing, scattering and fluorescence properties of gastrointestinal tissues, proved the viability of the CMOS optical microsystem with the optical filters to extract those signals, when comparing the obtained results with commercial equipment. The implemented apparatus is ready to be used as a portable system on a surgery room to verify the total removing of gastrointestinal cancer tissue. Moreover, the developed approach is a step forward in the implementation of a gastrointestinal dysplasia detection miniaturized tool.

Design of all-optical integrators and differentiators using Fabry-Perot filters based on fiber Bragg gratings

All-optical networks are the solution to overcome the speed limitation of electronic circuits. The basic and important components for all-optical circuits and optical signal processing are the integrator and differentiators. In photonics, there are many research, developments and implementations are going on in the area of above equivalents of fundamental devices that form basic building blocks in electronics signal processing. Here we are proposing a simple and cost-effective method to implement the optical differentiator and integrator using passive narrowband Fabry-Perot filters based on fiber Bragg gratings. Their high-speed performances are tested with Gaussian, Double Gaussian and Phase-Shifted Gaussian pulses.

温控频率可调谐窄带Fabry-Perot滤波器的研制

温控频率可调谐窄带Fabry-Perot滤波器的研制

Frequency stabilized coherent Brillouin random fiber laser: theory and experiments

A coherent random fiber laser based on stimulated Brillouin scattering as gain and Rayleigh scattering as distributed feedback mirror was constructed. Its frequency is stabilized by a high finesse narrow-band Fabry-Perot interferometer (FPI) to select lasing frequency within the gain bandwidth. The light confinement within single-mode fiber enhances largely the random lasing directionality, which enables a high-quality coherent random lasing in the weak scattering region by using a milliwatt continuous-wave pump source. The FPI in the laser configuration acts as a frequency selection on the Rayleigh feedback light, and thus the random lasing frequency was locked at one of its transmission peaks giving a relative frequency fluctuation of ~2.5 × 10(-11) at 100 s. The measured frequency jitter is within ~~ ± 20 kHz over 3 hours, 3 dB linewidth is ~50 Hz and frequency noise is ~20 mHz/Hz(1/2) at 10 kHz.

Far-infrared Fabry-Perot filters and laser resonators with high- Tc superconductor reflectors

We report on far-infrared Fabry-Perot filters and laser resonators with high- T c superconductor reflectors. We show that a MgO plate covered with a YBa 2Cu 3O 7−δ thin film at low temperature ( T⪡ T c ) can be used as a partially transparent mirror of high reflectivity up to the superconducting gap frequency of about 13 Thz. We demonstrate the use of reflectors for far-infrared narrow band Fabry-Perot filters and resonators of p-germanium lasers.

Transform-limited pulse generation in the gigahertz region from a gain-switched distributed-feedback laser diode using spectral windowing

For the first time, to our knowledge, transform-limited and high-power picosecond pulses in the gigahertz region are successfully generated from a distributed-feedback laser diode using spectral manipulation with a narrow-band Fabry-Perot resonator and erbium fiber amplifiers. The pulses, which before the optical filtering have a width of 27 psec and a spectral width of 1.24 nm, are transformed to transform-limited pulses with a width of 17 psec and a spectral width of 0.21 nm. The peak power of the pulse at a 6-GHz repetition rate is amplified to greater than 90 mW with an erbium fiber amplifier.

Time-resolved chirp evaluations of Gbit/s NRZ and gain-switched DFB laser pulses using narrowband Fabry-Perot spectrometer

A compact, easy-to-use, low-cost spectrometer for resolving the chirped spectrum of DFB lasers is demonstrated using narrowband Fabry-Perot etalons with resolutions comparable to grating spectrometers. Time-resolved chirp measurements of Gbit/s NRZ and gain-switched DFB laser pulses are presented.

Near-infrared observations of the dust coma of Comet Kohoutek (1973f) with a tilting-filter Fabry-Perot photometer

By means of narrow-band Fabry-Perot filters, which exclude the interference from molecular line fluorescence, the brightness of Comet Kohoutek (1973f) has been measured at 8560 and 8748 Å. Data reduction on the basis of averaged Mie-scattering cross sections indicates that the dust production rate was different before and after perihelion at the same heliocentric distances. This asymmetry suggests that vaporization and dust entrainment were governed by fractionation of a multicomponent mixture of parent molecules in a comparatively porous cometary nucleus.