High speed silicon optical switches based on carrier depletion - art. no. 67812D

The novel design of a silicon optical switch on the mechanism of a reverse p-n junction is proposed. The figuration of contact regions at slab waveguides and the ion implantation technology for creation of junctions are employed in the new design. The two-layer rib structure is helpful for reduction of optical absorption losses induced by metal and heavily-doped contact. And more, simulation results show that the index modulation efficiency of Mach-Zehnder interferometer enhances as the concentrations of dopants in junctions increase, while the trade-off of absorption loss is less than 3 dB/mu m. The phase shift reaches about 5 x 10(-4) pi/mu m at a reverse bias of 10V with the response time of about 0.2ns. The preliminary experimental results are presented. The frequency bandwidth of modulation operation can arrive in the range of GHz. However, heavily-doped contacts have an important effect on pulse response of these switches. While the contact region is not heavily-doped, that means metal electrodes have schottky contacts with p-n junctions, the operation bandwidth of the switch is limited to about 1GHz. For faster response, the heavily-doped contacts must be considered in the design.

High resolution interrogation technique based on linear photodiode array spectrometer for fiber Bragg grating Sensors - art. no. 65952C

A linear photodiode array spectrometer based, high resolution interrogation technique for fiber Bragg grating sensors is demonstrated. Spline interpolation and Polynomial Approximation Algorithm (PAA) are applied to the data points acquired by the spectrometer to improve the original PAA based interrogation method. Thereby fewer pixels are required to achieve the same resolution as original. Theoretical analysis indicates that if the FWHM of a FBG covers more than 3 pixels, the resolution of central wavelength shift will arrive at less than 1 pm. While the number of pixels increases to 6, the nominal resolution will decrease to 0.001 pm. Experimental result shows that Bragg wavelength resolution of similar to 1 pm is obtained for a FBG with FWHM of similar to 0.2 nm using a spectrometer with a pixel resolution of similar to 70 pm.

Investigation on pressure sensitivity of fiber optic mandrel hydrophone - art. no. 659544

Pressure sensitivity of the fiber optic mandrel hydrophone is analyzed in this paper. Based on the theory of elasticity, the mechanism of the pressure response is studied. The influence of the optical fiber on the compliant mandrel on the pressure response is taken into consideration for the first time. The radial deformation of the mandrel under the pressure of the fiber optic and the underwater pressure is analyzed in details. Based on the theory of photo-elasticity, the phase shift of the Mach-Zehnder interferometer is given. The pressure sensitivity is evaluated both theoretically and experimentally, and the results show a good correlation between the theoretical and experimental results.

Optical and structural properties of ZnO films grown on Si(100) substrates by MOCVD - art. no. 60290G

High quality ZnO films have been successfully grown on Si(100) substrates by Metal-organic chemical vapor deposition (MOCVD) technique. The optimization of growth conditions (II-VI ratio, growth temperature, etc) and the effects of film thickness and thermal treatment on ZnO films' crystal quality, surface morphology and optical properties were investigated using X-ray diffraction (XRD), atomic force microscopy (AFM), and photoluminescence (PL) spectrum, respectively. The XRD patterns of the films grown at the optimized temperature (300 degrees C) show only a sharp peak at about 34.4 degrees corresponding to the (0002) peak of hexagonal ZnO, and the FWHM was lower than 0.4 degrees. We find that under the optimized growth conditions, the increase of the ZnO films' thickness cannot improve their structural and optical properties. We suggest that if the film's thickness exceeds an optimum value, the crystal quality will be degraded due to the large differences of lattice constant and thermal expansion coefficient between Si and ZnO. In PL analysis, samples all displayed only ultraviolet emission peaks and no observable deep-level emission, which indicated high-quality ZnO films obtained. Thermal treatments were performed in oxygen and nitrogen atmosphere, respectively. Through the analysis of PL spectra, we found that ZnO films annealing in oxygen have the strongest intensity and the low FWHM of 10.44 nm(106 meV) which is smaller than other reported values on ZnO films grown by MOCVD.

The improvement of thick oxidized porous silicon layer growth process - art. no. 60290S

Oxidizing thick porous silicon layer into silicon dioxide is a timesaving and low-cost process for producing thick silicon dioxide layer used in silicon-based optical waveguide devices. The solution of H2O2 is proposed to post-treat thick porous silicon (PS) films. The prepared PS layer as the cathode is applied about 10 mA/cm(2) current in mixture of ethanol, HF, and H2O2 solutions, in order to improve the stability and the smoothness of the surface. With the low-temperature dry-O-2 pre-oxidizations and high-temperature wet O-2 oxidizations process, a high-quality SiO2 30 mu m thickness layer that fit for the optical waveguide device was prepared. The SEM images show significant improved smoothness on the surface of oxidized PS thick films, the SiO2 film has a stable and uniformity reflex index that measured by the prism coupler, the uniformity of the reflex index in different place of the wafer is about 0.0003.

Mode analysis of the UV-written channel waveguide - art. no. 60340J

The effective index method (EIM) was adopted to model the channel waveguide patterned by the UV in photosensitive silica film. The effective indexes of the different dimension symmetrical and asymmetrical channel waveguides were calculated, and the resource of the error of the method was pointed out. At last, the dimension rang to propagate single mode was presented.

High-speed photodetector characterization using tunable laser by optical heterodyne technique - art. no. 60200A

An ultra-wide-band frequency response measurement system for optoelectronic devices has been established using the optical heterodyne method utilizing a tunable laser and a wavelenath-fixed distributed feedback laser. By controlling the laser diode cavity length, the beat frequency is swept from DC to hundreds GHz. An outstanding advantage is that this measurement system does not need any high-speed light modulation source and additional calibration. In this measurement, two types of different O/E receivers have been tested. and 3 dB bandwidths measured by this system were 14.4GHz and 40GHz, respectively. The comparisons between experimental data and that from manufacturer show that this method is accurate and easy to carry out.

High-output very small aperture laser and its near-field distribution properties - art. no. 60200L

A Very-Small-Aperture Laser with a 250 X 500 nm(2) aperture has been created on a 650nm edge emitting LD. The highest far-field output power is 1.9mW and the power per unit emission area is about 15 MW/mu m(2). The special fabrication process and high output power mechanism are demonstrated respectively. The near-field distribution properties are also analyzed theoretically and experimentally.

Electroabsorption-modulated DFB laser integrated with dual-waveguide spot-size converter - art. no. 60200N

A 1.55-mu m ridge DFB laser and electroabsorption modulator monolithically integrated with a buried-ridge-stripe dual-waveguide spot-size converter at the output port for low-loss coupling to a cleaved single-mode optical fiber was fabricated by means of selective area growth, quantum well intermixing and dual-core technologies. These devices exhibit threshold current of 28 mA, side mode suppression ratio of 38.0 dB, 3-dB modulation bandwidth of 12.0 GHz, modulator extinction ratios of 25.0 dB dc. The output beam divergence angles of the spot-size converter in the horizontal and vertical directions are as small as 8.0 degrees x 12.6 degrees, respectively, resulting in 3.2 dB coupling loss with a cleaved single-mode optical fiber.

Tandem electroabsorption modulators integrated with DFB laser by ultra-low-pressure selective-area-growth MOCVD for 10 GHz optical short pulse generation - art. no. 60200O

A novel device of tandem multiple quantum wells (MQWs) electroabsorption modulators (EAMs) monolithically integrated with DFB laser is fabricated by ultra-low-pressure (22 mbar) selective area guowth (SAG) MOCVD technique. Experimental results exhibit superior device characteristics with low threshold of 19 mX output light power of 4.5 mW and over 20 dB extinction ratio when coupled into a single mode Fiber. Moreover, over 10 GHz modulation bandwidth is developed with a driving voltage of 2 V. Using I this sinusoidal voltage driven integrated device, 10GHz repetition rate pulse with a width of 13.7 ps without any compression elements is obtained.

Wavelength-selectable DFB laser with wide gain bandwidth realized in nonidentical quantum well - art. no. 60200W

Width varied quantum wells show a more flat and wide gain spectrume (about 115nm) than that of identical miltiple quantum well. A new fabricating method was demonstrated in this paper to realize two different Bragg grating in an selectable DFB laser based on this material grown identical chip using traditional holographic exposure. A wavelength by MOVPE was presented. Two stable distinct single longitudinal mode of 1510nm and 1530nm with SMSR of 45 dB were realized.

Microwave packaging for 10 Gb/s EML modulators - art. no. 60201O

A novel microwave packaging technique for 10Gb/s electro-absorption modulator integrated with distributed feedback laser (EML) is presented. The packaging parasitics and intrinsic parasitics are both well considered, and the packaging circuit was synthetically designed to compensate for the intrinsic parasitic of the chip. A butterfly-packaged EMI module has been successfully developed to prove that. The small-signal modulation bandwidth of the butterfly-packaged module is about 10 GHz. Optical fiber transmission experiments have shown that the module can be used for 10Gb/s optical transmission system. After transmission through 40km,. the power penalty is less than 1 dBm at a bit-error-rate of 10-12.

Recent progresses of SOI-based photonic devices - art. no. 60201R

SOI (Silicon on Insulator) based photonic devices, including stimulated emission from Si diode, RCE (Resonant Cavity Enhanced) photodiode with quantum structure, MOS (Metal Oxide Semiconductor) optical modulator with high frequency, SOI optical matrix switch and wavelength tunable filter are reviewed in the paper. The emphasis will be played on our recent results of SOI-based thermo-optic waveguide matrix switch with low insertion loss and fast response. A folding re-arrangeable non-blocking 4x4 matrix switch with total internal reflection (TIR) mirrors and a first blocking 16 x 16 matrix were fabricated on SOI wafer. The extinction ratio and the crosstalk are better. The insertion loss and the polarization dependent loss (PDL) at 1.55 mu m increase slightly with longer device length and more bend and intersecting waveguides. The insertion losses are expected to decrease 2-3 dB when anti-reflection films are added in the ends of the devices. The rise and fall times of the devices are 2.1 mu s and 2.3 mu s, respectively.

Subtraction of S-parameters for adiabatic small-signal modulation characteristics of laser diode - art. no. 60201V

An extended subtraction method of scattering parameters for characterizing laser diode is introduced in this paper. The intrinsic small-signal response can be directly extracted from the measured transmission coefficients of laser diode by the method. However the chip temperature may change with the injection bias current due to thermal effects, which causes inaccurate intrinsic response by our method. Therefore, how to determine the chip temperature and keep the laser chip adiabatic is very critical when extracting the intrinsic response. To tackle these problems, the dependence of the lasing wavelength of the laser diode on the chip temperature is investigated, and an applicable measurement setup which keeps the chip temperature stable is presented. The scattering parameters of laser diode are measured on diabatic and adiabatic conditions, and the extracted intrinsic responses for both conditions are compared. It is found that the adiabatic intrinsic responses are evidently superior to those without thermal consideration. The analysis indicates that inclusion of thermal effects is necessary to acquire accurate intrinsic response.

Leakage current analysis in AlGaInP/GaInP multi-quantum well lasers by the electrical derivative method - art. no. 60202F

In AlGaInP/GaInP multi-quantum well (MQW) lasers, the electron leakage current is a much more serious problem than that in laser diodes with longer wavelength. To further improve the output performance, the leakage current should be analyzed. In this letter, the temperature dependence of electrical derivative characteristics in AlGaInP/GaInP multi-quantum well lasers was measured, and the potential barrier for electron leakage was obtained. With the help of secondary ion mass spectroscopy (SIMS) measurement, theoretical analysis of the potential barrier was presented and compared with the measurement result. The influence of p-cladding doping level and doping profile on the potential barrier was discussed, and this can be helpful in metalorganic chemical vapor deposition (MOCVD) growth.