Chiemi Fujikawa

Tapered Spot Size Converter by Mask-Transfer Self-Written Technology for Optical Interconnection

A compact spot size converter (SSC) is the key to the future of optical interconnection. Hence, we proposed a tapered SSC using mask-transfer self-written (MTSW) technology with UV-curable resin. MTSW technology guarantees an easy and fast fabrication concept that makes it a promising technology for SSC devices. A prototype SSC adopting this technology was successfully fabricated. It was also confirmed that a tapered shape could be prepared from diffraction effect. A numerical calculation performed using the beam propagation method simulation shows that radiation loss decreases as SSC length increases. Comparison between the simulation and actual fabrication results shows acceptable value. Thus, this approach is reliable and has potential in the future of optical interconnection.

Self-written waveguide (SWW) optical pin for high optical coupling in multi-layer printed wiring board

The future of optical interconnection needs for high optical coupling efficiency for high density multi-layer printed wiring board (PWB). Hence, a self-written waveguide (SWW) optical pin is implemented between surface device and multi-layer channel as optical coupling for reaching high coupling efficiency. A comparatively studies of three configurations of coupling methods was carried out by ray-tracing simulation. The correlation between optical coupling efficiency and mirror angle was analyzed as well as the relationship between optical coupling efficiency and photodiode (PD) positional. A maximum value of optical coupling efficiency with optical pin is obtained for both correlations. The 1 dB down-tolerance width of the correlation between optical coupling efficiency and the mirror angle for vertical pin (case 1) is larger compared to case 2 and case 3 (without vertical pin). For the relationship between optical coupling efficiency and PD positional error, the 1 dB down-tolerance widths for case 1, case 2 and case 3 were ±13μm, ±19μm and ±20μm, respectively. From this result, it is found that vertical pin is well-suited to satisfy both coupling efficiency and tolerance for shifting mirror angle and PD positional error.

3-Beam laser Doppler velocimeter for 3-D velocity measurement

Laser Doppler Velocimeter (LDV) with a laser diode and Self-mixing effect is a new type of downsized and low cost LDV with high precision measurement. We propose a new LDV using a 3-beam fiber irradiation scheme. The sensor head consists of 3-fibers which are intersected perpendicularly each other. This new LDV enables three-dimensional velocity measurement. That is, the magnitude and direction of the velocity vector of the moving object can be measured independent on the relative position between the moving object and the 3-beam sensor head. We also study the case that these 3 beams are not right-angled each other. Operation principle and experimental results for both cases are reported.

Spot size converter using mask-transfer self-written waveguide method for optical interconnection

For the future of optical interconnect, the spot size converter (SSC) device is anticipated to be useful. Hence, we propose SSC using mask-transfer self-written (MTSW) method with UV-curable resin. Mask-transfer provides easy and fast fabrication concept. This makes these technology is a promising technology for SSC device. A prototype fabrication of tapered SSC shape was successfully fabricated due to diffraction effect. From beam propagation method (BPM) simulation, the graph shows that radiation loss decrease as SSC length increase. Comparison between simulation and actual fabricated result shows acceptable value around 0.1-0.2 dB. Thus, these approach is reliable and has potential in the future of optical interconnection.

Doppler velocity measurement with self-mixing effect of direct modulated laser diode enabling velocity direction

Doppler Laser Velocity measurement by self-mixing effect using direct modulation laser diode is proposed to distinguish the direction of the object movement. To distinguish the movement direction in conventional way, it is needed to assemble a frequency shift device such as an acoustic optic cell in the optical system. However, the self-mixing scheme cannot satisfy this condition this due to its simple system. Therefore, we applied triangularwave modulation current with repetition frequency of 250Hz directly to the laser diode emitting at a wavelength of 780nm. Target speed of 0.1 - 0.4 cm/s is measured and its movement direction forward and/or backward can be distinguished successfully. Both the velocity and moving direction of the target are obtained.

Optical coupling devices fabricated using UV-curable resin for board level optical interconnect

It is expected that opto-electronic printed wiring board (OE-PWB) will appear very soon. We study optical coupling schemes to multi-layer and multi-channel OE-OWB, and propose several optical coupling devices fabricated by using UV-curable resin. The “optical pin” is a vertical optical pillar, and that is one promising approach to achieve optical coupling with 90-deg path conversion between surface devices and optical wiring. Analysis using Optical Ray Tracing method shows that optical pin has potential to achieve higher optical coupling efficiency and larger positional tolerance. The optical pin can be fabricated by the Mask-Transfer Self-Written Waveguide (SWW) method using UV-curable resin. Next we propose optical coupling device with micro lens array. The advantage of using micro lens is that there will be no interaction between the beams crossings which means no crosstalk and noise will not occur. In addition, micro lens is flexible for fabrication. Starting fabrication of a single micro lens on tip of fiber, we succeeded in fabrication of micro lens array on patterned substrate.

Microlens fabricated on fiber tip using UV-curable resin for optical interconnect

The polymer microlens has been fabricated on a ferrule insert with fiber and directly on a bare fiber end to implement to optical interconnect. The Far Field Patterns have been measured for both and the divergence angle was calculated. From the result, the divergence angle of the microlens on fiber end is better compared to on the ferrule.

Polymer microlens fabricated on fiber tip for optical interconnect

An optical interconnect has attracted much interest to many researchers as it seemed as a solution to meet the requirement of future demand due to the limitations of the electrical interconnect. Low power consumption, small signal variation, and wide bandwidth are the example of the advantages of the optical interconnect. Nevertheless, the optical interconnect requires a high optical coupling which is a hurdle for the optical interconnect. The implementation of the microlens in optical interconnect seems as one of the possible ways which can solve the problem. It is expected that the microlens can focus the spreading light beam and improved the optical coupling. Thus, the polymer microlens has been fabricated on two different platforms; (i) on a ferrule insert with fiber inserted and (ii) directly on the fiber end. The Far Field Pattern measurement system has been used to evaluate the light collecting for both microlens and the divergence angle was measured. The results show that the divergence angle of the microlens on fiber end is better compared to the microlens on the ferrule.

Optical pin interface for 90-deg optical path conversion coupling to Printed Wiring Board

Special attention has been paid to introduction of “Optical wiring” in place of conventional “Metallic wiring” in Printed Wiring Board level. High efficiency and alignment-free coupling between optical wirings and optical devices is a key in this field. This paper introduces a new optical interface applying “Optical pin” which has an analogy to electrical pins widely used in present electronics boards. Concept of optical pin enabling 90-deg optical path conversion is proposed and a preliminary experiment using a fiber optical pin is introduced. Then a micro optical pin fabricated by Self-Written Waveguide Technology using UV-curable resin is shown.

Optical coupling for multi-layered optical printed wiring board using micro lens array

We proposed micro lens array coupling for multi-layered optical printed board. Optical coupling efficiency and optical positional tolerance of micro lens are discussed by ray trace simulation CAD. Polymer micro lens arrays can be fabricated easily by using UV curable resin. Our preliminary simulation indicated that four layers pitch of 125μm of optical printed wiring board is feasible for high coupling efficiency and high optical positional tolerance.