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We propose a new capacitive microinclinometer where oblique comb electrodes and double-folded suspension springs are aligned parallel to the vertical (111) plane of (110) silicon. The oblique comb utilizes both the overlapped area and the gap between movable and stationary electrodes, resulting in a considerable increase in sensitivity (capacitance change/angle). The resolution becomes even higher by taking advantage of the smooth (111) sidewalls of the oblique comb electrodes, which are fabricated using silicon deep reactive ion etching followed by crystalline wet etching. The surface roughness was reduced from 200 (Rrms) to 20 nm (Rrms), and the verticality was improved from 88.7° to 89.7°. The capacitance change of the fabricated inclinometer experimentally ranges from -0.793 to 0.783 pF for the full range of inclination angle (from -90° to 90°). The estimated worst resolution, which is obtainable at an inclination angle of ±85°, was as low as 0.25°.

We propose the use of a self-aligned epoxy microbridge with a metal layer for a low-cost, easy-to-make inline fiber optic chemical sensor that can sense the concentration of chemical solutions. The key component of the sensor is a cylindrical epoxy microbridge that can be assembled between input and output optical fibers by self-aligned UV curing. The microbridge is made from an epoxy that can rapidly diffuse liquid. The top of the microbridge was coated with Au/Ti to block diffusion of the surrounding solution and to induce optical dissipation that depends on the concentration of the chemical solution. We tested our fiber optic chemical sensor for deionized (DI) water and NaCl solution. The medium surrounding the microbridge asymmetrically diffuses into the epoxy microbridge due to the metal layer. The asymmetrical diffusion, consequently, makes a major change to the refractive index on the bottom of the microbridge, thereby altering the propagation mode of light. As a result, depending on the concentration of the NaCl solution, a fraction of the propagated light is absorbed into the metal layer. The sensitivity, which refers to the ratio of the concentration change and optical power, was experimentally confirmed to be 0.103 (wt%/photon count)

This paper presents a micromachined in-plane tunable optical filter using the thermo-optic effect of crystalline silicon. The device was fabricated by a silicon deep reactive ion etching process with a silicon-on-insulator wafer and thermal oxide removal to improve the sidewall smoothness. Optical fibers could be horizontally aligned on the fabricated TOF device by exploiting in-plane device structures, which enable TOFs to easily connect with other optical components. Tunability of the TOFs was experimentally achieved through thermal modulation of optical path length by heating the silicon etalon. As the input voltage increases, a notch in the reflectance spectrum shifts to a longer wavelength with an average tuning sensitivity of 0.9 nm K−1 and a best bandwidth of 1.1 nm. The proposed device can be utilized for spectroscopy or optical communication.

We have designed and characterized a novel micromachined variable optical attenuator (VOA) with a silicon optical wedge (SOW). Micromachined VOAs are being studied for effective signal balancing and device protection on a wavelength division multiplexing (WDM) network system. Several micromachined optical attenuators have been introduced using an optical shutter between two optical fibers. This reflective shutter in previous micromachined VOAs requires a troublesome sidewall metal coating to block out a part of the incident light signal. In this paper, we report on detailed design strategy and the characteristics of a refractive VOA with a wedge-shaped silicon microstructure. The proposed VOA is optimally designed to successively dissipate a blocked optical power by partial transmission and refraction outside the acceptance angle of the output fiber. The device can be simply fabricated using silicon-on-insulator (SOI) wafers and deep reactive ion etching (DRIE) without a sidewall metallization process. The fabricated VOA showed high performances, such as low insertion loss of 0.6 dB, wide attenuation range of over 43 dB with an optical response time of 6 ms. Return loss was experimentally obtained as high as 38 dB with beveled optical fibers even in an air-ambient condition. In the reliability test, the time-dependent loss (TDL), wavelength-dependent loss (WDL) and polarization-dependent loss (PDL) were measured as 0.08, 0.5 and 1.1 dB, respectively, for the attenuation level of 10 dB, and both WDL and PDL were considerably improved by the thermal oxidation and oxide removal in a high attenuation level.

We report on a novel refractive variable optical attenuator with a wedge-shaped silicon optical leaker, in which a part of the light signal is successively transmitted and refracted outside the acceptance angle of the output fiber. This device can be simply fabricated using a deep reactive ion etching and does not require sidewall metallization. We have theoretically estimated its optical characteristics and experimentally showed its high performances, such as low insertion loss of 0.6 dB and wide attenuation range of 43 dB. The fabricated device also showed a high return loss of over 39 dB even in an air-ambient condition and its polarization-dependent loss was smaller than 10% of the attenuation level.

We have developed a simple assembly technology to realize the tilted vertical combs for electrostatic micromirror scanners. The in-plane vertical comb electrodes are easily transformed into out-of-plane tilted comb by asymmetrical pushing down the levers of the spring that is attached to the micro mirror. The fabricated mirror scanner showed the optical scan angle of up to 1.3deg at 60 V and the resonant frequency of 3.15 kHz.

We describe a low cost, simply fabricated in-line fiber optic chemical sensor with gold coated, self-aligned epoxy waveguide for sensing the concentration of chemical solutions

This paper presents crystalline Si-based tunable Fabry-Perot filter, which enables its integration to align with other optical devices on an in-plane substrate. This device features wide tuning range over 80 nm and high tuning sensitivity of 11.7 nm/V.

In an optical wavelength division multiplexed (WDM) telecommunication system, optical add-drop multiplexers (OADM) with optical switches have been researched to change the paths of the signals. This paper reports on the design and characterization of a micromachined 2×2 optical switch aligned with 4 beveled fibers for low return loss in an optical add-drop application. For driving the micro mirror to change the optical paths an electrostatic comb actuator is used. The experimental return losses and polarization dependent loss were -43 and 0.05 dB, respectively.

Presents a new micromachined VOA with a wedge-shaped silicon optical leaker blocking and successively dissipating optical signal. This device features large attenuation range of -38 B, return loss of -40 dB and low cost owing to no troublesome sidewall metallization.

This paper presents, for the first time, a micromachined in-plane tunable optical filter (TOF) using thermo-optic effect for wavelength division multiplexed telecommunication. The TOFs are comprised of a Fabry-Perot silicon optical resonator formed between two distributed Bragg reflectors with high-reflectance based on silicon/air-gap pairs. The whole device was vertically fabricated using silicon deep reactive ion etching (DRIE). And input/output optical fibers were easily aligned along with the TOF structure on the substrate by exploiting in-plane fiber alignment. Tunability of the TOFs is experimentally achieved through thermal modulation of optical path length by heating the silicon resonator. As an input voltage increases, a notch of reflectance spectrum shifts to a longer wavelength with a tuning range of 9 nm and 3dB bandwidth of 2nm. The temperature of a silicon resonator was estimated to be about 93°C for the tuning range.

We design, fabricate, and characterize the micromachined refractive variable optical attenuator (VOA) with a wedge-shaped silicon optical leaker (SOL). The vertical structures of the VOA device can be simply fabricated by deep reactive ion etching with no sidewall metallization, and the 8 degrees angled fibers are employed for a high return loss even in air-ambient conditions. The SOL successively transmits and refracts part of the incident light far outside the acceptance angle of the output fiber, showing an effective optical attenuation. The fabricated VOA gives high optical performances, such as a response time of 6 ms, a return loss of 39 dB, an insertion loss of 0.6 dB, an attenuation range of 43 dB, and a polarization-dependent loss (PDL) of a 10% attenuation level, including a wavelength-dependent loss. The optical characteristics of the VOA are also theoretically investigated with respect to the wedge angles of the SOL. The experimental characteristics are in good agreement with the theoretical values calculated, considering light scattered from the endface of an optical fiber and sidewall of the SOL. The PDL estimation was confirmed especially to sufficiently explain the fundamental characteristic of the PDL for the refractive VOA.