Multi-wavelength Light Source Research Articles

Advanced synchrotron radiation stepper alignment system performance

Canon has been developing a synchrotron radiation stepper system for volume production known as the XR1. The system incorporates many-original technologies. In this article, the key features of the XR1 alignment system and its performance will be discussed. To align the mask and wafer, the alignment system uses Fresnel zone plates as alignment marks. Our alignment is based on an advanced dual grating lens method. In order to attain high alignment accuracy and large process latitude, we improved the design of alignment marks and optics of the alignment scope. The alignment marks are optimized to minimize alignment error resulting from changing the gap distance between the mask and wafer, which is called telecentricity. Using these newly designed alignment marks, we have evaluated alignment accuracy. We obtained alignment accuracy 3σ of 11.9(X) and 10.2 nm(Y) using etched SiN patterns on a Si substrate. Furthermore, the alignment scope is designed with multiwavelength light sources to illuminate the alignment marks. Selectable three laser diodes are applied in the optics. Multiwavelength light sources compensate each other and achieve robustness for various lithography processes.

Multiwavelength light emitters for scanning applications fabricated by flipchip bonding

We present a multiwavelength light source which was fabricated using a self-aligned flipchip bonding technique. The device consists of an InGaN-GaN light-emitting diode emitting light at around 420 nm, on top of which we flipchip-bonded a monolithically integrated red/infrared dual-beam laser. The upper two lasers were built by selective removal of the red laser, and subsequent regrowth of an infrared laser structure. Since all processes, including the deposition of the PbSn solder bumps for bonding, were based on photolithographic precision, tight alignment tolerances of /spl plusmn/μm in the lateral direction could be fulfilled between the ridge waveguides of the three light emitters. For a high-speed color scanning system, this is an important design criterion because it will allow the use of a single scanning optics for the three laser beams.

Fast thickness profile measurement of a thin film by using a line scan charge coupled device camera

A technique based on counting the interference fringes produced by a thin film with a fast line scan charge coupled device camera is developed to measure the thickness profiles of the film every 50 μS. When this technique is applied to the bursting of a soap film, the dynamics of the bursting can be reconstructed from these thickness profiles. A method of thickness calibration by using a white light laser as a multiwavelength light source and a video camera as a detector is also introduced. The merit of this calibration technique is that with the help of digital image processing nearly no alignments of the optics are needed.

Multiwavelength light source with precise frequency spacing using a mode-locked semiconductor laser and an arrayed waveguide grating filter

A multiwavelength light source with precise optical frequency spacing can be created by extracting an individual mode of a semiconductor mode-locked laser using an arrayed waveguide grating filter. The outputs of the light source are locked to wavelength division multiplexing (WDM) optical frequency grids using an optical frequency standard light source. They can be successfully modulated by 5 Gb/s nonreturn-to-zero (NRZ) signals and can be transmitted through 100-km-long optical fiber.

WDM ring network using a centralized multiwavelength light source and add-drop multiplexing filters

We propose and experimentally demonstrate a wavelength division multiplexed (WDM) ring network employing a centralized multiwavelength light source to supply all nodes with optical carriers of precise wavelength spacing. This approach overcomes the problem of monitoring and controlling the wavelengths of optical sources dispersed throughout the network. A four-node test bed using optical lattice-type add-drop multiplexing filters and a multiwavelength light source based on resonant cavity-enhanced four wave mixing in a Fabry-Perot laser diode was constructed to demonstrate the feasibility of the proposed method. The effects of coherent crosstalk in such networks are analyzed, and methods such as phase scrambling or the use of a pulsed optical source are shown to significantly reduce the effects of coherent crosstalk. The use of four-port add-drop multiplexer (ADM) filters instead of 1:n optical wavelength multiplexer/demultiplexers to implement the wavelength add-drop function at each node is shown to lead to a broader transmission bandwidth for each channel and also easier compatibility with the coherent crosstalk suppression mechanisms described.

Multiwavelength erbium-doped fibre laser using intracavity etalon and cooled by liquid nitrogen

The authors report simultaneous oscillation of 17 0.8 nm spliced wavelengths from a Fabry-Perot (FP) erbium doped fibre laser. Multiwavelength operation is made possible by inserting an intracavity etalon and cooling the erbium doped fibre at 77 K by liquid nitrogen. It is promising as the multiwavelength light source for wavelength division multiplexing (WDM) networks. Heterodyne measurement shows that two or three longitudinal modes exist in each wavelength.

Vertical cavity devices as wavelength selective waveguides

We show that novel wavelength-sensitive devices can be fabricated by coupling a semiconductor vertical cavity resonator to a low index waveguide. The optical mode in the resonator propagates at an angle, and the resonator resembles a high index waveguide. A taper in the thickness of the resonator allows different parts of the waveguide to operate at different wavelengths. These structures are analyzed using both thin film equations and waveguide normalism. Concentrating on a waveguide demultiplexer, simple design equations are derived, and a demonstration device is fabricated for TE mode at 0.75 /spl mu/m operation. Using AlGaAs/AlAs multilayers and a polymer top waveguide, the spectrometer exhibited a dispersion of 29 nm/cm, a wavelength resolution of better than 1 nm, and an intrinsic device efficiency of about 90%. A similar structure containing a light-emitting quantum well operated as a multiwavelength light source by modifying the spontaneous emission into the polymer waveguide.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Modification of late dermal necrosis in the pig by treatment with multi-wavelength light.

Low-level light from a multi-wavelength light source has been used to prevent late X-ray-induced dermal necrosis in the pig. Skin fields, measuring 4 cm x 4 cm on the flank, were irradiated with graded doses of X rays and the incidence of late dermal necrosis at 10-16 weeks after irradiation was scored. The control skin sites were irradiated only with 250 kV X rays but the test skin sites were subsequently exposed to low-level light. Local light exposure was from an array of gallium aluminium arsenide diodes, which produced wavelengths of 660, 820, 880 and 950 nm, pulsating at 5 kHz. Light treatment was given three times a week, from 6-16 weeks after X irradiation. Each treatment session was 1 min, which was equivalent to energy density of 1.08 Jcm-2. Light treatment increased the ED50, the dose which causes dermal necrosis in 50% of the irradiated skin fields, from 20.10 +/- 0.12 Gy to 21.94 +/- 0.30 Gy. This difference, although small, was highly significant (p < 0.001) and was equivalent to a dose modification factor (DMF) of 1.09. The effect of light treatment was minimal at incidence levels of less than the 50% but greater at higher levels of effect. These findings suggest that low-level light, when applied appropriately, may be useful in the prevention of late X-ray-induced damage to the dermis.

A new fibre ribbon identification technique for in-service passive branched optical fiber networks

A technique is proposed for identifying one of the branched fiber ribbons that are fanned out from a common fiber via optical splitters. Multiwavelength light sources, WDM-couplers, and the free-ports of biconical fiber couplers in an optical splitter are used for the remote injection of an identification signal, whose wavelength is different from the communication wavelength, into a particular branched fiber ribbon. A particular fiber ribbon is identified from among four fiber ribbons without disrupting a 1.31/1.55 mu m optical transmission by using an identifier operating at 1.61 approximately 1.67 mu m. >

OEICs: Movement and evolution.

Optoelectronic integrated circuits (OEICs), in which optoelectronic devices are integrated withother optoelectronic and/or electronic devices together, have potential advantages in increasingperformance, manufacturability and functionality over conventional discrete optoelectronic devices.Transmitters and receivers have most been developed, as have been represented by LSI levelintegration of GaAs-based receivers and ultrafast ('5 GHz) operation of In P-based integratedlasers. A variety of optical functions have also been generated by recent researches introducingwaveguide devices as demonstrated in multi-wavelength light sources, coherent optical receiversand laser-based optical logic elements. This paper describes such movements in OEIC researchand discusses possible evolution of OEICs in the future.

Increasing the Memory Capacity of the Digital Light Deflector by “Color Coding”

Considerations are given to the use of a multiwavelength light source in the digital light deflector for the purpose of increasing the memory capacity of the system. An increase of a factor of twenty or more is theoretically possible when potassium tantalate niobate (KTN) is used for the optical switches in the digital light deflector. Practical considerations may, however, limit the increase to about a factor of ten.