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Abstract: A type of Mach–Zehnder modulator based on optical bias method which use organic polymer DR1/PMMA as the ridge waveguide material is designed. Variations of the relations between effective indexes and the structure parameters include the width, height and thickness of ridge waveguide and the upper and lower cladding thicknesses are analyzed by the effective index method (EIM). A single microstrip electrode and the ridge waveguide have been used in this modulator to achieve velocity-match between light wave and microwave. The optical field and power are simulated by BPM using the above optimized parameters of the structure. The initial phase difference between the two arms achieves 89.8° and the extinction ratio achieves 27dB in this organic polymer Mach–Zehnder modulator. [Copyright &y& Elsevier]

Microwave photonic channelizers assisted by coherent dual optical frequency combs (OFCs) have been widely considered for wideband radio frequency (RF) spectrum analysis. However, it requires dual OFCs with a large free spectral range (FSR) and multiple comb lines to support a wide RF coverage, leading to a complicated system structure and low optical spectrum efficiency. To this end, we propose a simplified, high optical spectrum-efficiency microwave photonic channelizer, wherein the odd-order and even-order OFCs with a double frequency spacing are generated and isolated to directly slice two frequency-shifted modulated optical spectra into a series of subbands. N comb lines can support 4 × N channels but take up a significantly reduced optical spectrum range. Partial experiments and simulations are presented to demonstrate the scheme. By exploiting a four-lines odd-order OFC and three-lines even OFC, a wideband RF spectrum range of 0–56 GHz is divided into 28 channels with a channel bandwidth of 2 GHz, and various wideband signals are spectrally analyzed with a high measurement accuracy and large image rejection suppression higher than 30 dB. Moreover, a 16-quadrature amplitude modulation (16QAM) vector signal with a center frequency of 7 GHz and a bit rate of 1 Gbps is channelized and successfully recovered with a good constellation diagram. • Propose a simplified, high optical spectrum-efficiency microwave photonic channelizer. • N comb lines can support 4 × N channels. • 0–56 GHz RF range is divided into 28 sub-channels with a channel bandwidth of 2 GHz. • The filtering accuracy requirement of the optical channelized filter is reduced by half. [ABSTRACT FROM AUTHOR]

Based on the extended coupled nonlinear Schrödinger equations in an optical fiber with quintic nonlinearity (QN), the approximate analytical frequency chirps and the critical distances for the cross-phase modulation induced optical wave breaking (OWB) are discussed for the initial Gaussian optical pulses. Evolutions of the frequency chirps, shapes and spectra of pulses are numerically calculated in the normal dispersion regime. It is shown that, the approximate analytical frequency chirps accords well with the numerical ones at the initial evolution stages of the pulses. And the calculated approximate critical OWB distances accord well with the numerical ones only for the traditional OWB. In addition, for the positive QN and the negative one but with small absolute values, the traditional OWB can be observed. While for the negative QN with large absolute values, non-traditional OWB may occur. Namely, soliton pulse trains may develop during the pulse propagation. [ABSTRACT FROM AUTHOR]

Abstract We demonstrated the mode structure of a folded telescopic structural resonator used in high energy laser. The scalar diffraction theory and iterative algorithm are applied to simulate the effect of intracavity phase disturbation on eigenmode features of the telescope structural unstable resonator. The transverse-mode properties and beam quality have been investigated experimentally with H S wavefront analysis and Zernike aberration function by including resonator misalignment parameters. Starting from a comparative analysis of the first 64-order Zernike coefficient of the wavefront, it is shown that typical low order perturbation notablely affects the eigenmode intensity, and will also increases the relevant high-order aberrations such as A 3 , A 5 and A 7 in wavefront features. High order frequency Zernike aberration of beam will obviously degrade outcoupled beam properties, e.g., the base transverse mode will turn into the multi-mode. The beam quality can be effectively improved by the priority correction of low order intracavity Zernike aberration in such structural resonators. [ABSTRACT FROM AUTHOR]

The influence of representative aberration on the performance of a side pumped electro-optic Q-switched Nd:YAG lasers was demonstrated. The spatial and temporal behavior of the laser with intracavity disturbation was modeled using a numerical calculation of the diffraction integral equations and then experimentally characterized. The eigenmode properties, including the coaxial state with thermal effect of the active medium and geometric misalignment of the cavity OC mirror have been analyzed. Zernike polynomials are further adopted to describe beam distortions by combining the model wavefront reconstruction. Experiment illustrates that the lower-order Zernike aberration such as Z 3 , Z 4 Z 5 and Z 10 , etc. caused by the typical phase disturbation will significantly affect the mode characteristics and the uniform symmetry of wavefront. Other related beam properties e.g. PSF can also be acquired by further calculation. In addition, the proposed method has the merit of working stability and high efficiency. Corresponding strategies are suggested to consider active compensation of intracavity aberration in such lasers. [ABSTRACT FROM AUTHOR]

• The absorption spectrum of the Rubrene:MoO3 (in 1:1 wt ratio)mixed film was measured and the results demonstrate that the mixed film shows intensively absorption at the near-infrared region(∼930nm). • To further analysis the affection of MoO3 to Rubrene, the Rubrene:MoO3 films with different proportion of MoO3 were also prepared. • The absorption spectrum of the mixe films demonstrates that the interaction between Rubrene and MoO3 is enhancing with the concentration of MoO3 increasing and the energy is decreasing. • The near-infrared photo-detection device based on Rubrene:MoO3 film was fabricated. • The current-voltage(I–V) characteristic of the device was measured and the infrared detector exhibits an photo dark I / I ratio of ∼8 under a 940nm light illumination with a light intensity of 0.5Wcm-2. Rubrene:MoO 3 mixed films(in 1:1 wt ratio) were deposited on quartz substrates using the thermal evaporation technique and the absorption spectrum of the mixed film was measured. The results demonstrate that the mixed film shows intensively absorption at the near-infrared region(∼930 nm) which indicates that the interaction between Rubrene and MoO 3 is intensively and induced intermediate level in the band gap of Rubrene and formed charge-transfer complex(CTC). Furthermore, the type of transition is direct allowed transition according to the measurement of optical band gap. To further analysis the affection of MoO 3 to Rubrene, the Rubrene:MoO 3 films with different proportion of MoO 3 were also prepared using the thermal evaporation technique. The absorption spectrum of the mixed films was measured and the results demonstrate that the interaction between Rubrene and MoO 3 is enhancing with the concentration of MoO 3 increasing and the energy needed by the transition of electrons is decreasing. The near-infrared photo-detection device based on Rubrene:MoO 3 film was fabricated. The current-voltage(I–V) characteristic of the device was measured and the results demonstrate that under 5 V bias, the infrared detector exhibits an I photo / I dark ratio of ∼8 under a 940 nm light illumination with a light intensity of 0.5 W·c m − 2. [ABSTRACT FROM AUTHOR]

The analytical treatment of typical defocus aberration and its impact on the mode wavefront properties of a confocal structural laser resonator is discussed. Numerical modeling of the system is deduced to predict the influence of defocus disturbation on mode intensity and phase distribution. In addition, an experimental method by combining Zernike aberration function and wavefront reconstruction to measure the dynamic wavefront aberration for such lasers has been developed. Beam mode characteristics, including the alignment state and defocus aberration perturbation have been presented. It is shown that the typical Zernike aberration such as A 3 , A 5 and A 10 caused by intracavity perturbation significantly affected the beam properties, PSF profiles and circle energy distribution in the far field. The experimental results show that defocus aberration characteristics can be used as an effective basis for dynamic compensation of typical aberration in such lasers. Furthermore, corresponding strategies are proposed to implement the active correction of typical optical aberration in such resonators. [ABSTRACT FROM AUTHOR]