Tandem organic light-emitting diode with a molybdenum tri-oxide thin film interconnector layer

A 10-nm-thick molybdenum tri-oxide（MoO3） thin film was used as the interconnector layer in tandem organic lightemitting devices（OLEDs）.The tandem OLEDs with two identical emissive units consisting of N,N-bis（naphthalen-1-yl）N,N-bis（phenyl）-benzidine（NPB） /tris（8-hydroxyquinoline） aluminum（Alq3） exhibited current efficiency-current density characteristics superior to the conventional single-unit devices.At 20 mA/cm2,the current efficiency of the tandem OLEDs using the interconnector layers of MoO3 thin film was about 4.0 cd/A,which is about twice that of the corresponding conventional single-unit device（1.8cd/A）.The tandem OLED showed a higher power efficiency than the conventional single-unit device for luminance over 1200cd/m2.The experimental results demonstrated that a MoO3 thin film with a proper thickness can be used as an effective interconnector layer in tandem OLEDs.Such an interconnector layer can be easily fabricated by simple thermal evaporation,greatly simplifying the device processing and fabrication processes required by previously reported interconnector layers.A possible explanation was proposed for the carrier generation of the MoO3 interconnector layer.

Analysis of laser induced thermal mechanical relationship of HfO_2/SiO_2 high reflective optical thin film at 1064 nm

A numerical model is developed for the calculation of transient temperature field of thin film coating induced by a long-pulsed high power laser beam. The electric field intensity distribution of HfO2/Si02 high reflective （HR） film is investigated to calculate the thermal field of the film. The thermal-mechanical relationships are discussed to predict the laser damage area of optical thin film under long pulse high energy laser irradiation.

Measurement of absolute phase shift on reflection of thin films using white-light spectral interferometry

A novel method to measure the absolute phase shift on reflection of thin film is presented utilizing a white-light interferometer in spectral domain. By applying Fourier transformation to the recorded spectral interference signal, we retrieve the spectral phase function Ф, which is induced by three parts： the path length difference in air L, the effective thickness of slightly dispersive cube beam splitter Teff and the nonlinear phase function due to multi-reflection of the thin film structure. We utilize the fact that the overall optical path difference （OPD） is linearly dependent on the refractive index of the beam splitter to determine both L and Teff. The spectral phase shift on reflection of thin film structure can be obtained by subtracting these two parts from Ф. We show theoretically and experimentally that our new method can provide a simple and fast solution in calculating the absolute spectral phase function of optical thin films, while still maintaining high accuracy.

Impact of cascaded thin-film filters on metro networks employing NRZ, LPF-DB, and CSRZ formats

We studied the transmission performance of metro networks employing cascaded thin-film filters (TFFs) for three modulation formats including non-return-to-zero (NRZ), duobinary, and carrier-suppressed RZ (CSRZ). The effects caused by TFFs' dispersion and passband characteristics are investigated for 10- and 40-Gb/s signals, respectively. Simulation results show that the penalty resulted from dispersion can be partially compensated by the passband effects of the cascaded filters. CSRZ is shown to be a preferred format compared with NRZ and duobinary primarily originating from its good back-to-back performance.

Enhanced ultraviolet emission from ZnO thin film covered by TiO_2 nanoparticles

A ZnO thin film covered by TiO2 nanoparticles is prepared by electron beam evaporation. The structure and surface morphology of the sample are analyzed by X-ray diffraction （XRD） and atomic force microscopy （AFM）, respectively. Photoluminescence is used to investigate the fluorescent property of the ample. The results show that the ultraviolet （UV） emission of the ZnO thin film is greatly enhanced after it is covered by TiO2 nanoparticles while the green emission is suppressed. The enhanced UV emission mainly results from the fluorescence resonance energy transfer （FRET） between ZnO thin film and TiO： nanoparticles. This TiO2-ZnO composite thin film can be used to fabricate high-efficiency UV emitters.

Review of recent progresses on flexible oxide semiconductor thin film transistors based on atomic layer deposition processes

The current article is a review of recent progress and major trends in the field of flexible oxide thin film transistors（TFTs）, fabricating with atomic layer deposition（ALD） processes. The ALD process offers accurate controlling of film thickness and composition as well as ability of achieving excellent uniformity over large areas at relatively low temperatures. First, an introduction is provided on what is the definition of ALD, the difference among other vacuum deposition techniques, and the brief key factors of ALD on flexible devices. Second, considering functional layers in flexible oxide TFT, the ALD process on polymer substrates may improve device performances such as mobility and stability, adopting as buffer layers over the polymer substrate, gate insulators, and active layers. Third, this review consists of the evaluation methods of flexible oxide TFTs under various mechanical stress conditions. The bending radius and repetition cycles are mostly considering for conventional flexible devices. It summarizes how the device has been degraded/changed under various stress types（directions）. The last part of this review suggests a potential of each ALD film, including the releasing stress, the optimization of TFT structure, and the enhancement of device performance. Thus, the functional ALD layers in flexible oxide TFTs offer great possibilities regarding anti-mechanical stress films, along with flexible display and information storage application fields.

Free-space 1×2 wavelength-selective switches for wavelength-division multiplexing optical networks

A free-space 1 ×2 wavelength-selective switch （WSS） based on thin-film filter technology is proposed. The 1 × 2 WSS is fabricated with an electromagnetic actuator, a reflecton prism, a narrow-band thin-film filter, and three fiber collimators. The working principle and the configuration of WSS are illuminated. The experimental results indicate a fiber-to-fiber insertion loss ranging from 1.109 to 1.249 dB with 2-V voltage input, which satisfies the application of optical fiber communication.

A 500-600 MHz GaN power amplifier with RC-LC stability network

The GaAs-based TF-IPD fabrication process and equivalent lumped element circuit are utilized to re- duce the circuit size for double-section Wilkinson power divider. Ultimately the dimension of the proposed S-band power divider is reduced to 1.03 × 0.98 mm2. Its measured results show an operating fractional bandwidth of 54%, and return losses and isolation of greater than 20 dB. In addition the excess insertion loss is less than 1.1 dB. More- over the good features contain amplitude and phase equilibrium with the values of better than 0.03 dB and 1.5° separately. This miniaturized power divider could be widely used in RF/microwave circuit systems.