Electrotunable Non‐reciprocal Laser Emission from a Liquid‐Crystal Photonic Device

A liquid crystal (LC) photonic device with an anisotropic optical heterojunction structure has been fabricated. The device has a phase‐retarding nematic LC (NLC) layer sandwiched between two polymer cholesteric LC films with right‐handed helices of different pitches. Electrotunable non‐reciprocal light transmittance and unidirectional circularly polarized (CP) lasing emission have been successfully demonstrated for this device structure. Two left CP (LCP) lasing emission peaks are observed at the edges of the overlapping region between the two photonic bands in the structure and are shifted upon the application of a voltage. In contrast, a non‐reciprocal right CP (RCP) lasing emission peak emerges at one of the band edges and diminishes upon the application of a voltage. These phenomena are interpreted based on the selective reflection of RCP light and the reorientation of the NLC molecules by the application of a voltage.     

通信网交换系统的发展趋向

本文对宽带综合通信网交换系统几个主要方面技术的发展趋向作了概括介绍，内容包括：电子交换的分布结构、ＡＴＭ交换的开始应用，个人通信的无线进网，宽带交换引用光子技术和多媒体交换结构分析。     

Composition tuning of room-temperature nanolasers

We show that careful preparation conditions enable the preparation of high quality nanoribbons capable of room-temperature lasing covering the complete spectral range from near infrared (NIR) to ultraviolet (UV). Two ternary compound II-VI semiconductors, CdS_1−XSe_X and Zn_YCd_1−YS, can be grown on single c-Si substrates to achieve this task. High-resolution transmission electron microscopy and x-ray diffraction showed that the ternary nanoribbons were single phase and single crystal. Room-temperature optical measurements showed that band-gap engineering could be realized via composition modulation in X and Y, with fine tuning of the lasing wavelength via composition changes (ΔX and ΔY) capable of overlapping thermally induced tuning, demonstrating the possibility of continuous tuning in the lasing wavelength throughout the complete 340-710 nm spectral range. We further demonstrate that it is possible to control the spatial composition gradient with sub-mm resolution thus opening the possibility for the fabrication of devices with full spectral optimization.     

Plasmonic and photonic scattering and near fields of nanoparticles

We theoretically compare the scattering and near field of nanoparticles from different types of materials, each characterized by specific optical properties that determine the interaction with light: metals with their free charge carriers giving rise to plasmon resonances, dielectrics showing zero absorption in wide wavelength ranges, and semiconductors combining the two beforehand mentioned properties plus a band gap. Our simulations are based on Mie theory and on full 3D calculations of Maxwell’s equations with the finite element method. Scattering and absorption cross sections, their division into the different order electric and magnetic modes, electromagnetic near field distributions around the nanoparticles at various wavelengths as well as angular distributions of the scattered light were investigated. The combined information from these calculations will give guidelines for choosing adequate nanoparticles when aiming at certain scattering properties. With a special focus on the integration into thin film solar cells, we will evaluate our results.     

从Photonics Asia-2002看自适应光学的发展趋势

简要介绍了SPIE举办的亚洲光电子学会议（Photonics Asia-2002）,对其中的一个分会《自适应光学及其应用》进行了详细的介绍、分析与评述,对自适应光学的发展趋势作出了展望。     

Atomic‐Layer Graphene as a Saturable Absorber for Ultrafast Pulsed Lasers

The optical conductance of monolayer graphene is defined solely by the fine structure constant, α = (where e is the electron charge, is Dirac's constant and c is the speed of light). The absorbance has been predicted to be independent of frequency. In principle, the interband optical absorption in zero‐gap graphene could be saturated readily under strong excitation due to Pauli blocking. Here, use of atomic layer graphene as saturable absorber in a mode‐locked fiber laser for the generation of ultrashort soliton pulses (756 fs) at the telecommunication band is demonstrated. The modulation depth can be tuned in a wide range from 66.5% to 6.2% by varying the graphene thickness. These results suggest that ultrathin graphene films are potentially useful as optical elements in fiber lasers. Graphene as a laser mode locker can have many merits such as lower saturation intensity, ultrafast recovery time, tunable modulation depth, and wideband tunability.     

再现曙光 迎接灿烂──发展浙江光产业的思考

探讨光产业的发展前景,提出发展浙江光产业,将它培育成为21世纪支柱产业的思路,分析了浙江光产业的有利条件、发展方向和对策建议。