Feng Lishuang

SiO2 Waveguide Resonator Used in an Integrated Optical Gyroscope

An integrated optical waveguide resonator based on a SiO2 waveguide is proposed, fabricated and tested. The method of designing the resonator is also presented. The optimal splitting ratio of the coupler is gained by simulating the relationship between the splitting ratio of the key coupler in the resonator and the resonators finesse with resonance depth. The calculated fundamental detection limit of this integrated optical waveguide resonator is l.6°/h. Finally, a micro-optical gyroscope system based on the integrated waveguide resonator is built, and the measured resonators finesse F is close to 70 under fluctuating temperature. To the best of our knowledge, the present F is the best result to date. For the coupler splitting rate the experimental results have fixed errors with the simulation results caused by fabrication processes which can be easily eliminated, implying that the method of design is effective and applicable.

Frequency Modulation Induced by using the Linear Phase Modulation Method used in a Resonator Micro-optic Gyro

Resonator micro-optic gyro (R-MOG) sensing rotation angular-velocity is based on Sagnac effect. We present a frequency modulation (FM) induced by the analog triangle-waveform phase modulation (ATAW-PM) technique in an R-MOG. Compared with the traditional serrodyne phase modulation or digital phase modulation methods, the proposed modulation technique has the intrinsic advantage in free of sweeping-back or step-effect induced pulse noise. The influence on dynamic range and resolution of the R-MOG by the parameters of analog triangle-waveform is theoretically analyzed. Experiments are carried out on an R-MOG composed of an integrated optic resonator with a free spectral range (FSR) and a fitness (F) of 1.6 GHz and 61, respectively. Dynamic range of ±500 deg/s and bias drift of 0.6 deg/s over 1 h and 0.05 deg/s for 60s are reliably obtained.

Structural Design of a Compact in-Plane Nano-Grating Accelerometer

A combination of large mass, weak spring and nano-grating is the key for a nano-grating accelerometer to measure nano-G acceleration. A novel compact nano-grating accelerometer integrating a large mass with nano-grating is proposed. First, the numbers of diffraction orders are calculated. Then, structure parameters are optimized by finite element analysis to achieve a high sensitivity in an ideal vibration mode. Finally, we design the fabrication method to form such a compact nano-grating accelerometer and successfully fabricate the uniform and well-designed nano-gratings with a period of 847 nm, crater of 451 nm by an FIB/SEM dual beam system. Based on the ANSYS simulation, a nano-grating accelerometer is predicted to work in the first modal and enables the accelerometer to have displacement sensitivity at 197 nm/G with a measurement range of ±1 G, corresponding to zeroth diffraction beam optical sensitivity 1%/mG. The nano-gratings fabricated are very close to those designed ones within experimental error to lay the foundation for the sequent fabrication. These results provide a theoretical basis for the design and fabrication of nano-grating accelerometers.

Optical Noise Analysis in Dual-Resonator Structural Micro-Optic Gyro

A novel micro resonator optic gyroscope comprising a dual-resonator structure is proposed. This design radically eliminates the noise induced by Rayleigh backscattering, the Kerr effect and polarization coupling. The configuration of the micro optic gyroscope (MOG) is given and described. Three methods are applied to suppress the optical noises in the system and to theoretically analyze the performance improvement. Experiments are carried out on both dual-resonator and single-resonator MOGs, which show the resonance depth improvement from 0.7477 to 0.9173 in the present MOG dual-resonator configuration.

Studies on 2,4-DNT Mixtures Using Reflection Terahertz Time Domain Spectroscopy for Explosives Detection

Absorption spectra (0.2?1.8 THz) of the mixtures of explosive 2,4-DNT and polyethylene(PE) at different ratios are obtained using reflection terahertz time domain spectroscopy (THz-TDS). The pronounced absorption peak of 2,4-DNT at 1.08 THz is always observed for the mixtures with 2,4-DNT ratios above 20%. Experimental results demonstrate that more applicable and realistic THz-TDS in reflection geometry can be used to distinguish explosive mixed with other material having no THz fingerprints, and has a high potential in the detection of explosives.

Micrograting Displacement Sensor with Integrated Electrostatic Actuation

A high-resolution micro-grating displacement sensor with diffraction-based and integrated electrostatic actuation is proposed and experimentally demonstrated. The Al reflecting membrane is fabricated at the bottom of a silicon moving part and the Au micro-gratings are patterned on a transparent substrate. This structure forms a phase sensitive diffraction grating, providing the displacement sensitivity of the micro-grating interferometer. It shows sensitivity adjustment and self-calibration capabilities with electrostatic actuation. Additional system components include a coherent light source, photodiodes, and required electronics. Experimental results show that the displacement sensor has a sensitivity of about 1.8 mV/nm and a resolution of less than 1 nm in the linear region. This displacement sensor is very promising in the fields requiring high sensitivity, broad dynamic range, and immunity to electromagnetic interference.

Difference frequency detecting through beat note in RFOG system

The Resonant Fiber Optical Gyroscope (RFOG) is an important component in the inertial navigation systems due to the small size, low cost and low power. A new method of using two semiconductor lasers locked to the clockwise resonance and the counter-clockwise resonance of a resonant is proposed. This paper analyzes the principle of beat note and do a simulation program. At last we can obtain the difference frequency through beat note between two separate semiconductor lasers, which is of significance to promote the wide application of RFOG in practical inertial systems.