An improvement of the electroluminescence (EL) intensity of the CdF2/CaF2 intersubband transition (ISBT) light-emitting structure is reported. In the ISBT active region, the precise control of crystal growth is strongly required. In this work, the hydrogen-annealing surface flattening of Si substrates was employed to obtain a high quality active region to suppress non-radiative leakage current. A markedly flat surface was obtained in the 30-µm-wide trench bottom after hydrogen annealing. In the EL measurement of the device fabricated in the trench, the EL intensity was approximately 40 times stronger than that of the device without patterning and hydrogen annealing.
We present details of a local high-index contrast silica waveguide that uses trenches filled with a low-refractive index material enabling bends with small radius to be used. The lateral relative refractive index difference was 8.34% and the minimum bend radius was 300µm. An 8-channel, 100GHz spacing compact arrayed-waveguide grating using waveguides with small bend radius was successfully fabricated.
An optical burst switching (OBS) node with a fast 4x4 PLZT (Lead Lanthanum Zirconate Titanate) optical matrix switch and an electronic label processor is presented. Successful collision detection and collision resolution is demonstrated by two methods: deflection routing and shared wavelength conversion. Error-free performance at 10Gbps payload was achieved for both. Switching speed of 3.5µs was achieved, demonstrating small data granularity in the order of 10µs.
Substrate noise is a key problem in the design of large mixed-signal circuits. Estimating the interaction from large digital blocks and its effect on on-chip performance degradation is extremely important in mixed-signal IC design and is a major challenge in system-on-chip(SOC) design. In this paper, we address efficient methods and models to simulate substrate noise coupling at high level design with the real-time capability .Techniques to directly or indirectly compute the values of the elements in the cell macromodel are described. This approach makes it possible to predict substrate noise generation of large digital blocks in a very efficient and fast way and makes it compatible with the design flow of mixed-signal circuits. For verification, the macromodel accuracy is demonstrated in some example circuits.
Gain and noise figure enhancements in an Er/Yb doped fiber amplifier (EYDFA) are demonstrated using a dual-stage amplifier configuration. In comparison to a conventional single-stage amplifier, the gain in this amplifier is enhanced at all wavelengths between 1530 to 1560nm for the input signal powers of -40 and 0dBm. A maximum gain improvement of 7.3dB is obtained at a small signal (-40dBm) wavelength of 1534nm. The noise figure of the design is also enhanced at all wavelengths between 1530 to 1560nm with a maximum reduction of 3.0dB obtained at the small signal wavelength (-40dBm) of 1542nm. The total pump power used in this design is fixed at 140mW. This improvement of gain and noise characteristics is attributed to the efficient pump power distribution within the amplifier and also the addition of a midway optical isolator between the two amplifier stages. The isolator blocks the backward propagating ASE to increase the population inversion at the first stage and thus, enhances the amplifier gain and noise figure. These results show that the usage of a dual-stage configuration with a midway optical isolator is an invaluable consideration when constructing a practical EYDFA.