A selective, rapid thermal-cyclic atomic-level etching (ALE) of tungsten is developed. The first step of this process is exposing the surface of tungsten with hydrofluorocarbon plasma at −22°C to form a tungsten fluoride-based surface modified layer on the tungsten surface. The second step is rapid thermal annealing with infrared (IR) irradiation to remove the surface modified layer. Tungsten 4f peaks and a fluorine 1s peak, which were assigned to tungsten fluoride, were observed by in-situ x-ray photoelectron spectroscopy immediately after plasma exposure. The peaks that originated from tungsten fluoride disappeared after the samples were annealed. Cyclic etching tests were carried out by repeating plasma exposure and IR irradiation with a 300-mm ALE tool. Films of tungsten, TiN, and SiO<sub>2</sub> were used as sample materials. The amount of etched tungsten increased as the number of cycle repetitions increased. The etched amount per cycle for tungsten was 0.8 nm. In comparison, etching of TiN and SiO<sub>2</sub> was not detected. Conformal etching profiles of patterned samples after 60 cycles were obtained. Furthermore, the etched amount per cycle showed saturation behavior with regard to plasma exposure time. Selective, rapid thermal cyclic ALE of tungsten was thus successfully demonstrated.
We have developed the uncooled electroabsorption modulator integrated distributed feedback (EA/DFB) lasers for small-footprint and low-power-consumption transceiver modulus. In this study, we used the temperature-tolerant InGaAlAs materials in EA modulator. We investigated the 10.7-Gbps, 40-km transmission performances over wide temperature range. The dynamic extinction ratio was 9.9 dB and 13.3 dB at the 10ºC and 85ºC. The modulated output power was more than +3.7 dBm even at 85ºC. The long-term reliability was also investigated under APC condition at ambient temperature of 85ºC with starting current of 120 mA. There was no significant degradation of the operation current up to 5000 hours. Uncooled 1300-nm range 25-Gbps and 43-Gbps EA/DFB lasers were also investigated. These devices will provide cost-effective 100-Gbps and 40-Gbps transceiver for next-generation high speed network system. A wide temperature ranged 12-km transmission with over 9.6-dB dynamic extinction ratio was demonstrated under 25-Gbps modulation. A 43-Gbps 10-km transmission was also demonstrated. The laser achieved clearly opened eye diagrams with dynamic extinction ratio of over 7-dB from 25ºC to 85ºC.
An InGaAlAs short-cavity DBR laser enabling 1.3-μm, uncooled, 10-Gbit/s operation at lower drive currents is demonstrated. This laser consists of a short InGaAlAs-MQW active region butt-jointed to an InGaAsP-DBR region. This structure provides moderate chip power, low threshold current, and a large relaxation oscillation frequency simultaneously, because it has an optimum cavity length in the range between 10 and 100 μm, at which both VCSELs and conventional edge-emitters cannot be formed because of their difficulty of manufacture. The fabricated 75-μm short-cavity laser demonstrated 100°C, 10-Gb/s operation at a record low drive current of 14 mA<sub>p-p</sub>. Furthermore, it achieved side-mode suppression ratio of more than 37 dB at a high yield of 95%, because of the naturally high single-mode stability of its short-cavity DBR structure.
We present a beam-shaping technique to enhance emitting power density for a high-power laser-diode array stack. By use of a stripe mirror and a high-reflection mirror, the laser source height of 42 mm is folded to 21 mm and the emitting power density is increased to 365 W/cm2 from a raw emitting power density of 194 W/cm2. Moreover, the beam parameter product (BPP) that is used to evaluate the beam quality is effectively improved to 168-mm mrad from a raw BPP of 336-mm mrad in the fast axis for the collimated high-power laser-diode array stack.
Recently, we report a new type of micro channel plate spatial light modulator (MSLM), in which the bulk LiNbO<SUB>3</SUB> crystal plate is replaced by an electro-optic composite material, namely, single crystal waveguide array. This array is a 2D LiNbO<SUB>3</SUB> single crystal waveguide array, which consists of single crystal waveguides with filling materials among adjacent waveguides. Since the dielectric constant of LiNbO<SUB>3</SUB> single crystal is much higher than that of gap filling materials such as polymer/epoxy, the electric field can mostly be constrained inside the crystal material. In addition, by selecting proper opaque filling material, there are also no optical crosstalks among adjacent waveguides. Thus, this special waveguide array works as a 2D set of optically and electrically isolated light guides. While the sensitivity is unchanged, the spatial resolution can be increased. In this paper, a prototype of such a MSLM is presented. The manufacturing processes of the MSLM is introduced. The evaluation on the performance of the MSLM is also reported. The advantages and limitations of the MSLM are addressed.
Wideband optical signal processing for adaptive antennas calls for a high-performance spatial light amplifier (SLA). The latter can be implemented as an upgrade of micro-channel SLA by replacing bulk crystal with a single-crystal fiber array (SCFA). This paper is focused on SCFA fabrication. The design process from specifying SCFA parameters to selecting fabrication technique (dice-and-fill or laser-heated pedestal growth) is reviewed. The results achieved with the dice-and- fill method are presented.
We first briefly review a new 3-D imaging technique called optical scanning holography (OSH). We then discuss the technique's 3-D holographic magnification in the context of optical scanning and digital reconstruction. Finally, we demonstrate the 3-D imaging capability of OSH by holographically recording two planar objects at different depths and reconstructing the hologram digitally.
We first review a newly developed 3D imaging technique called optical scanning holography (OSH), and discuss recording and reconstruction of a point object using the principle of OSH. We then derive 3D holographic magnification, using three points configured as a 3D object. Finally, we demonstrated 3D imaging capability of OSH by holographically recording two planar objects at different depths and reconstructing the hologram digitally.
Holographic information pertaining to an object can be generated using an active optical heterodyne scanning technique. In this technique, the holographic information manifests itself as an electrical signal which can be sent to an electron-beam-addressed spatial light modulator for coherent image reconstruction. Real-time holographic imaging of 2-D objects has recently been demonstrated. The use of alternate waveforms in the scanning beam can process the holographic content of the object in real time. In this communication, we propose a holographic edge extraction technique which utilizes alternate waveforms in the optical scanning holographic recording stage. We have developed a 1-D computer model of the optical heterodyne scanning holographic system using Fourier analysis which we use to simulate holographic edge extraction.