Bangren Shi

A single-mode single-polarization monolithically silica waveguide ring resonator used in microoptic gyro

A single-mode single-polarization waveguide (SMSPW) ring resonator for the microoptic gyro (MOG) was proposed, and it could be monolithically integrated onto a silica planar lightwave circuit. We have presented the design of a three-dimensional SMSPW ring resonator in which the TM mode cuts off and the TE mode transmits by taking into consideration the stress-induced birefringence effect of the Si-based silica waveguide using the effective-index method. The characteristics of the light propagation across the SMSPW resonator were studied by a three-dimensional finite difference beam propagation method. Numerical simulation results showed the SMSPW ring resonator has a high extinction ratio over 50 dB cm−1 for the TM mode, low propagation loss of 0.055 dB cm−1 for the TE mode, and a high finesse of 36. A rate detection limit of 0.8° h−1 can be achieved. Without increasing the complexity of the waveguide fabrication process, this structure can solve the MOGs output bias instabilities induced by polarization fluctuations and provide a new solution for MOGs.

A 2×2 multimode interference coupler with exponentially tapered waveguide

An exponentially tapered structure is introduced into multimode interference (MMI) devices. Compared with a parabolically tapered structure, which has been successfully used in MMI devices, this structure can further reduce the length of these devices. The performances of the 2×2 MMI coupler with exponentially tapered structure, such as the optical transmission, the splitting ratio, the wavelength response and the fabrication tolerance, are investigated by the 2D finite difference beam propagation method. Results show that the exponentially tapered MMI coupler exhibits a similar property to that with a parabolically tapered structure except for the splitting ratio. The exponentially tapered structure can offer a possible application in MMI couplers with a free choice of the splitting ratio.

Experimental study on resonator micro-optic gyroscope

Resonator optic gyroscope (ROG) based on Sagnac effect has been investigated over the past years and developed as an attractive device for many applications. Resonator micro-optic gyroscope (R-MOG) with an only several-cm-long ring on a wafer is a promising candidate for the new generation inertial rotation sensor. Using micro machining process, R-MOG was manufactured on the silicon or LiNbO3 wafer by etching passive optical ring resonator devices. It has great advantages by realizing the minitype. R-MOG is a kind of optic gyroscope by detecting the resonance frequency difference of the clockwise and counterclockwise resonance to measure the angular velocity. The Sagnac effect is extremely weak, so the detection method has been the key point in researching R-MOG. Using the multi-beam superposition principle, we theoretically analyzed the signal detection scheme based on laser frequency modulation and experimentally investigated the equivalent open-loop signals of a R-MOG chip. The passive ring resonator (PRR), the core component of R-MOG, was composed of a ring waveguide with a radius of 2cm and an optical coupler with the coupling ratio of 12%. The resonance curve showed that the free spectral range (FSR), full width at half maximum (FWHM) and fineness were 3.0378GHz, 74.09MHz and 41, respectively. In the equivalent open-loop experiment, the counterclockwise (CCW) light frequency was locked to its resonant point, and the clockwise (CW) optical frequency changed around the CW resonant point. The experimental results illustrated that the sensitivity of the R-MOG was 6.15 rad/s.

Direct-Coupled Large-Diameter Silica on Silicon Waveguide Ring Resonator Used in Microoptic Gyro

A kind of direct-coupled large-diameter silica on silicon waveguide ring resonator used in microoptic gyro with 4 cm diameter was presented. An optical and electromechanical test platform was designed to investigate the performance of the ring resonator. The resonance curve, demodulation curve and three relative important resonator parameters were obtained. The free spectral range of the resonator, the full width at half maximum of the resonance curve and the finesse of the resonator, are 3 GHz, 73 MHz and 41, respectively. Open-loop experiments of resonator are set up using the acousto-optic frequency modulation spectroscopy technique. The output of MOG is investigated by the platform rotate and equivalent gyro rotate. The slope of the linear fit is about 3.154 mV/(°/s) based on the −50∼50°/s rotating rates and 0.330 mV/(°/s) based on the −900∼900 KHz equivalent frequency shift, respectively. The demodulation curve shows a strongly nonlinear and the linear approximation has a great limitation.

A novel silica-waveguide acousto-optic frequency shifter using ZnO piezoelectric films and its beam propagation analysis

A novel silica-waveguide integrated acoustooptic frequency shifter (AOFS) with high diffraction efficiency is proposed for an optical wavelength of 1.55μm in this paper. Choose tapered silica waveguides fabricated on silicon substrates by PECVD and C-axis oriented ZnO piezoelectric films deposited using RF-sputtering as the interdigital transducer for the excitation of SAW. The interdigital Al electrodes are located at the interface between the nonpiezoelectric substrates (SiO2) and the ZnO piezoelectric films, that is, ZnO/IDT/SiO2 structure; when the ZnO films thickness h and SAWs wavelength Λ satisfy the relation h/Λ=0.4~0.5, electromechanical coupling coefficient of the interdigital transducer achieves the maximum value 17%. Diffraction properties are simulated and analyzed using beam propagation method (BPM) and AO interaction area is well-designed in order to obtain optimum interaction characteristics. The results show that a diffraction efficiency of approximately 70% can be obtained.

Optimal design and fabrication of ring resonator composed of Ge0 2 -doped silica waveguides for IOG

The ring resonator is the core sensing element in the resonant integration optical gyroscope (IOG) . Its performances influence the minimum resolution and the error items of gyroscope directly and it is the key of the design and manufacturing. This paper presents optimal design of ring resonator composed of Ge02 -doped silica waveguides fabricated on silicon substrates using wide angle beam propagation method (WA-BPM). The characteristic of the light propagating across the ring resonator is analyzed. According to the design results, we succeed in fabricating the ring resonator by Plasma Enhanced Chemical Vapor Deposition (PECVD) method and Reactive Ion Etching (RIE) technology. In order to characterize the ring resonator, an optical measurement setup is built, fiber laser line-width is 50 kHz, detector responsibility is 0.95A/W and integral time is 10s. By testing, propagation loss and total loss of ring resonator are 0.02dB/cm and 0.1dB/circuit respectively. Observed from the resonance curve, a finesse of 12.5.

The spot diagram of waveguide geodesic lens

Geometric Optic analysis method is introduced into GL, two principle surface functions of GL are obtained. And from them, GL can be approximated to a thin lens just like gas lens. With light trail approaching, GL phase transission function can be found. Based on Fresnel diffractive theory, mode distribution of GL is obtained. Our optimal GL of non-curvature singularity and non-spherical has reference numbers: focus 20mm, aperture 8mm transition region 10mm. Incident light wavelength is 0.6328 μm. these parameters are substituted into GL field distribution, Matlab method is used to do analytical solution and intensity distribution. The theory model is similar to experiments.