Yongxiao Li

Quadrature demodulation with synchronous difference for interferometric fiber-optic gyroscopes

We propose a novel method of quadrature demodulation with synchronous difference for suppressing noise in interferometric fiber-optic gyroscopes (IFOGs). For an IFOG with sine wave phase modulation, an in-phase result and a quadrature result are obtained simultaneously by coherent detection. Eigenfrequency modulation is used and a phase shift of 45° is set between the modulation signal and the reference signal, so that two results have the same expectation of amplitude but with opposite signs. A synchronous difference procedure is carried out for output, in which signals are added up and common noise between two results is eliminated. Theoretical analysis and experimental results show that both short term noise and long term instability of the IFOG are reduced by this method. In experimental comparison with the traditional demodulation method on the same IFOG with a 1982 m fiber coil, this method reduces the bias drift from 0.040°/h to 0.004°/h.

All-Depolarized Interferometric Fiber-Optic Gyroscope Based on Optical Compensation

We propose and demonstrate a novel configuration for depolarized interferometric fiber-optic gyroscopes (IFOGs). This configuration utilizes optical compensation between two orthogonal polarizations for suppressing errors induced by polarization nonreciprocity. Theoretical analysis shows that it is a new approach different from conventional IFOGs where a polarizer is mandatory. An experimental demonstration of the proposed IFOG (2097-m coil, open-loop configuration) achieves a low bias drift of 0.016 °/h in detecting the Earths rotation rate. Furthermore, this configuration requires no polarizer or any other polarization-maintaining device.

1.54 μm electroluminescence from p-Si anode organic light emitting diode with Bphen: Er(DBM) 3 phen as emitter and Bphen as electron transport material

1.54 microm Si-anode organic light emitting devices with Er(DBM)(3)phen: Bphen and Bphen/Bphen:Cs(2)CO(3) as the emissive and electron transport layers (the devices are referred to as the Bphen-based devices) have been investigated. In comparison with the AlQ-based devices with the same structure but with AlQ:Er(DBM)(3)Phen and AlQ as the emissive and electron transport layers, the maximum EL intensity and maximum power efficiency from the Bphen-based devices increase by a factor of 3 and 2.2, respectively. The optimized p-Si anode resistivity of the Bphen-based device of 10 Omega.cm is significantly lower than that of the AlQ-based device. The NIR EL improvement can be attributed to the energy transfer from Bphen to the Er complex and equilibrium of electron injection from the Sm/Au cathode and hole injection from the p-Si anode at a higher level.

A multi-frequency signal processing method for fiber-optic gyroscopes with square wave modulation.

The bias stability and random walk coefficients (RWC) of interferometric fiber-optic gyroscopes (IFOGs) are directly affected by characteristic noises produced by optoelectronics interactions in optic sensors. This paper documents a novel demodulation method for square wave modulated IFOGs, a method capable of suppressing the white noise that results from optical intensity noises and circuit noises as well as shot noises. In addition, this paper provides a statistical analysis of IFOG signals. Through use of orthogonal harmonic demodulation followed by deployment of matched filters to detract the Sagnac phase from the IFOGs, these channels we then processed, using principle component analysis (PCA), to establish optimal independent synchronous quadrature signal channels. Finally a difference procedure was carried out for the outputs. Our results showed that an experimental sample of the proposed IFOG (1982 m coil under uncontrolled room temperature) achieved a real-time output variance improvement in detecting the Earths rotation rate, which is well matched with theoretical calculations of its Cramèr-Rao bound (CRB).

Capability of GaN based micro-light emitting diodes operated at an injection level of kA/cm2

Different size InGaN/GaN based micro-LEDs (μLEDs) are fabricated. An extremely high injection level above 16 kA/cm2 is achieved for 10 μm-diameter LED. The lateral current density and carrier distributions of the μLEDs are simulated by APSYS software. Streak camera time resolved photoluminescence (TRPL) results show clear evidence that the band-gap renormalization (BGR) effect is weakened by strain relaxation in smaller size μLEDs. BGR affects the relaxation of free carriers on the conduction band bottom in multiple quantum wells (MQWs), and then indirectly affects the recombination rate of carriers. An energy band model based on BGR effect is made to explain the high-injection-level phenomenon for μLEDs.

Highly efficient phosphorescent organic light-emitting diode with a nanometer-thick Ni silicide / polycrystalline p-Si composite anode

A phosphorescent organic light-emitting diode (PhOLED) with a nanometer-thick (approximately 10 nm) Ni silicide/ polycrystalline p-Si composite anode is reported. The structure of the PhOLED is Al mirror/ glass substrate / Si isolation layer / Ni silicide / polycrystalline p-Si/ V(2)O(5)/ NPB/ CBP: (ppy)(2)Ir(acac)/ Bphen/ Bphen: Cs(2)CO(3)/ Sm/ Au/ BCP. In the composite anode, the Ni-induced polycrystalline p-Si layer injects holes into the V(2)O(5)/ NPB, and the Ni silicide layer reduces the sheet resistance of the composite anode and thus the series resistance of the PhOLED. By adopting various measures for specially optimizing the thickness of the Ni layer, which induces Si crystallization and forms a Ni silicide layer of appropriate thickness, the highest external quantum efficiency and power conversion efficiency have been raised to 26% and 11%, respectively.