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.

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.

Enhancement of the far-field output power and the beam properties of plasmonic very small aperture lasers

The properties of plasmonic very small aperture lasers are shown: these integrate surface plasmon structures with very small aperture lasers. The transmission field can be confined to a spot of subwavelength width in the far field, and according to the finite difference time domain simulation results the focal length of the spot can be modulated using different ring periods. Scanning of the subwavelength gating in the far field has been realized numerically. Such a device can be used with a high-resolution far-field scanning optical microscope.

A simple ac bridge for detecting small resistance change

A simple ac resistance bridge is proposed. The stability of the design is better than 10(-6), which is especially suitable for detecting tiny changes of resistance. An example of magnetoresistance measurement for a 220 nm Au film shows the good performance of the bridge. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3202284]

Plasmonic very-small-aperture lasers

The fabrication of plasmonic very-small-aperture lasers is demonstrated in this letter. It is an integration of the surface plasmon structures and very-small-aperture lasers (VSAL). The experimental and numerical results demonstrate that the transmission field can be confined to a spot with subwavelength width in the far field, and the power output can be enhanced 140% of the normal VSAL. Such a device can be useful in the application of a high resolution far-field scanning optical microscope. (C) 2007 American Institute of Physics.

The whispering gallery mode in photonic crystal ring cavity - art. no. 698438

Whispering gallery modes (WGMs) in microcavities possess ultra-high cavity Q factor. Such microcavity are easy to be fabricated, so WGMs have attracted much attention in the area of photonics and integrated photonic circuits. It is well known that the effect of total internal reflection restricts the size of this mirocavity. Such drawback goes against the integration of photon. However, the photonic crystal microcavities (PCMC) make a breakthrough recently. The WGMs in the PCMC are possible to gain both ultra-high Q and ultra-small mode volume. In this paper, the property of the mode in photonic crystal ring cavity is analyzed by FDTD and PWE. By modifying the airholes in the corners of the ring cavity, we can obtain the WGM. Also the Q factor of WGM in photonic crystal ring cavity is calculated. This favors the design of the photonic crystal microcavity components.

Superluminescent diode monolithically integrated with novel Y-branch by bundle integrated waveguide for fiber optic gyroscope - art. no. 68380D

We have developed a novel InP-based, ridge-waveguide photonic integrated circuit (PIC), which consists of a 1.1-um wavelength Y-branch optical waveguide with low loss and improved far field pattern and a 1.3-um wavelength strained InGaAsP-InP multiple quantum-well superluminescent diode, with bundle integrated guide (BIG) as the scheme for monolithic integration. The simulations of BIG and Y-branches show low losses and improved far-field patterns, based on the beam propagation method (BPM). The amplified spontaneous emission of the device is up to 10 mW at 120 mA with no threshold and saturation. Spectral characteristics of about 30 nm width and less than I dB modulation are achieved using the built-in anti-lasing ability of Y-branch. The beam divergence angles in horizontal and vertical directions are optimized to as small as 12 degrees x8 degrees, resulting in good fiber coupling. The compactness, simplicity in fabrication, good superluminescent performance, low transmission loss and estimated low coupling loss prove the BIG and Y-branch method to be a feasible way for integration and make the photonic integrated circuit of Y-branch and superluminescent diode an promising candidate for transmitter and transceiver used in fiber optic gyroscope.

Realization of SOI submicrometer optical waveguide components - art. no. 68380L

Submicrometer channel and rib waveguides based on SOI (Silicon-On-Insulator) have been designed and fabricated with electron-beam lithography and inductively coupled plasma dry etching. Propagation loss of 8.39dB/mm was measured using the cut-back method. Based on these so-called nanowire waveguides, we have also demonstrated some functional components with small dimensions, including sharp 90 degrees bends with radius of a few micrometers, T-branches, directional couplers and multimode interferometer couplers.

Measurement and analysis of microwave frequency response of semiconductor optical amplifiers - art. no. 682406

The measurement and analysis of the microwave frequency response of semiconductor optical amplifiers (SOAs) are proposed in this paper. The response is measured using a vector network analyzer. Then with the direct-subtracting method, which is based on the definition of scattering parameters of optoelectronic devices, the responses of both the optical signal source and the photodetector are eliminated, and the response of only the SOA is extracted. Some characteristics of the responses can be observed: the responses are quasi-highpass; the gain increases with the bias current; and the response becomes more gradient while the bias current is increasing. The multisectional model of an SOA is then used to analyze the response theoretically. By deducing from the carrier rate equation of one section under the steady state and the small-signal state, the expression of the frequency response is obtained. Then by iterating the expression, the response of the whole SOA is simulated. The simulated results are in good agreement with the measured on the three main characteristics, which are also explained by the deduced results. This proves the validity of the theoretical analysis.

Fabrication and characterization of TO packaged high-speed laser modules - art. no. 682407

Various high-speed laser modules are fabricated by TO-Packaged processes, such as FP laser modules, DFB laser modules, and VCSEL modules. Furthermore,, the resonance among the circuit elements provides an approach to compensating the TO packaging parasitics, and improving the frequency response of the devices. The detailed equivalent circuit model is established to investigate both the laser diode and packaging comprehensively. The small-signal modulation bandwidths of the TO packaged FP laser, DFB laser and the VCSEL modules are more than 10, 9.7 and 8 GHz, respectively.

Wavelength tunable distributed Bragg reflector laser integrated with electro-absorption modulator by a combined method of selective area growth and quantum well intermixing - art. no. 68240N

Wavelength tunable electro-absorption modulated distributed Bragg reflector lasers (TEMLs) are promising light source in dense wavelength division multiplexing (DWDM) optical fiber communication system due to high modulation speed, small chirp, low drive voltage, compactness and fast wavelength tuning ability. Thus, increased the transmission capacity, the functionality and the flexibility are provided. Materials with bandgap difference as large as 250nm have been integrated on the same wafer by a combined technique of selective area growth (SAG) and quantum well intermixing (QWI), which supplies a flexible and controllable platform for the need of photonic integrated circuits (PIC). A TEML has been fabricated by this technique for the first time. The component has superior characteristics as following: threshold current of 37mA, output power of 3.5mW at 100mA injection and 0V modulator bias voltage, extinction ratio of more than 20 dB with modulator reverse voltage from 0V to 2V when coupled into a single mode fiber, and wavelength tuning range of 4.4nm covering 6 100-GHz WDM channels. A clearly open eye diagram is observed when the integrated EAM is driven with a 10-Gb/s electrical NRZ signal. A good transmission characteristic is exhibited with power penalties less than 2.2 dB at a bit error ratio (BER) of 10(-10) after 44.4 km standard fiber transmission.

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.

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.

Novel compact SOI-based reconfigurable optical add/drop multiplexer using microring resonators - art. no. 60190L

Novel compact design for 4-channel SOI-based reconfigurable optical add/drop multiplexer using microring resonators is presented and analyzed. Microring resonators have two important attributes as a key new technology for future optical communications, namely functionality and compactness. Functionality refers to the fact that a wide range of desirable filter characteristics can be synthesized by coupling multiple rings. Compactness refers the fact that ring resonators with radii about 30 mu m can lead to large scale integration of devices with densities on the order of 10(4) similar to 10(5) devices per square centimeter. A 4-channel reconfigurable optical add/drop multiplexer comprises a grid-like array of ridge waveguides which perpendicularly cross through each other. SOI-based resonators consisted of multiple rings at each of the cross-grid nodes serve as the wavelength selective switch, and they can switch an optical signal between two ports by means of tuning refractive index of one of the rings. The thermo-optic coefficient of silicon is 1.86x 10(-4) /K. Thus a temperature rise of 27K will increase the refractive index by 5 x 10(-3), which is enough to cause the switching of our designed microring resonators. The thermo-optic effect is used to suppress the resonator power transfer, rather than to promote loss. Thus, the input signal only suffers small attenuation and simultaneously low crosstalk can be achieved by using multiple rings.

Narrow stripe selective growth of InGaAlAs waveguides used for buried heterostructure lasers - art. no. 63210I

The narrow stripe selective growth of the InGaAlAs bulk waveguides and InGaAlAs MQW waveguides was first investigated. Flat and clear interfaces were obtained for the selectively grown InGaAlAs waveguides under optimized growth conditions. These selectively grown InGaAlAs waveguides were covered by specific InP layers, which can keep the waveguides from being oxidized during the fabrication of devices. PL peak wavelength shifts of 70 nm for the InGaAlAs bulk waveguides and 73 nm for the InGaAlAs MQW waveguides were obtained with a small mask stripe width varying from 0 to 40 gm, and were interpreted in considering both the migration effect from the masked region (MMR) and the lateral vapor diffusion effect (LVD). The quality of the selectively grown InGaAlAs MQW waveguides was confirmed by the PL peak intensity and the PL FWHM. Using the narrow stripe selectively grown InGaAlAs MQW waveguides, then the buried heterostructure (BH) lasers were fabricated by a developed unselective regrowth method, instead of conventional selective regrowth. The InGaAlAs MQW BH lasers exhibit good performance characteristics, with a high internal differential quantum efficiency of about 85% and an internal loss of 6.7 cm(-1).