• Korean Journal of Optics and Photonics
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• v.17 no.1
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• pp.99-103
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• 2006

A tunable wavelength filter was proposed and demonstrated by using the UV nanoimprint technique. It consists of a Bragg grating in polymer waveguides and a heating electrode. The manufacturing of the grating was substantially simplified with the introduction of a smart imprint stamp containing a waveguide pattern integrated with the grating pattern. The center wavelength of the filter was successfully tuned by taking advantage of the thermooptic effect in polymers, which was induced by supplying electrical power to the electrode. For the fabricated device, a transmission dip of ${\~}$15 dB and a 3-dB bandwidth of 0.8 nm were obtained at the Bragg wavelength of ${\~}$l560 nm. The achieved thermooptic tuning efficiency was ${\~}$0.28 nm/mW, while the center wavelength was shifted from 1560 nm to 1558 nm with the electrical power consumption of 7 mW.

• Korean Journal of Optics and Photonics
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• v.22 no.2
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• pp.102-107
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• 2011

In this paper, a small double ring resonator reflector was designed and fabricated using a polymer waveguide, and the measurement result was discussed. A widely tunable characteristic of the small double ring resonator caused by the Vernier effect, which results from the difference of the ring radii, was observed. The insertion loss of the double ring reflector was reduced by minimizing the device length to be as short as possible, and thus the output power and the SMSR (side mode suppression ratio) was greatly enhanced. The hybrid integrated laser based on the small double ring resonator reflector lased with the SMSR of 45 dB. In addition, the wide tuning range of 40 nm could be obtained by injecting a current of 30 mA to an electrode on top of the reflector.

• Journal of the Korean Society for Precision Engineering
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• v.24 no.4 s.193
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• pp.153-158
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• 2007

Recently nano imprint lithography to fabricate photonic crystal on polymer is preferred because of its simplicity and short process time and ease of precise manufacturing. But, the technique requires the precise mold as an imprinting tool for good replication. These molds are made of the silicon, nickel and quartz. But this is not desirable due to complex fabrication process, high cost. So, we describe a simple, precise and low cost method of fabricating PDMS stamp to make the photonic crystals. In order to fabricate the PDMS mold, we make the original pattern with designed hole array by finding the optimal electron beam writing condition. And then, we have tried to fabricate PDMS mold by the replica molding with ultrasonic vibration and pressure system. We have used the cleaning process to solve the detaching problem on the interface. Using these methods, we acquired the PDMS mold for photonic crystals with characteristics of a good replication. And the accuracy of replication shows below 1% in 440nm at diameter and in 610nm at lattice constant by dimensional analysis by SEM and AFM.

• Korean Journal of Optics and Photonics
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• v.8 no.3
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• pp.245-249
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• 1997

An electro-optic polymer digital optical switch with a coupling region modified for optimum coupling is designed and demonstrated. Its branch waveguide is fabricated by reactive ion etching. Then, the modified coupling region is adiabatically introduced along the propagation direction from the branching point of the two waveguides, and it is implemented by photobleaching after the device fabrication. The structure of the modified coupling region and its refractive index profiles are designed to optimize and mode coupling in the Y-branch waveguide. Therefore, the switching performance of the device was shown to be enhanced with a fixed device length. The measured drive voltage is reduced by more than 30 percents, and the crosstalk is also improved by about 4~6 dB.

• Korean Journal of Optics and Photonics
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• v.35 no.4
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• pp.175-183
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• 2024

Research into optical signal processing using photonic integrated circuits (PICs) has been actively pursued in various fields, including optical communication, optical sensors, and quantum optics. Among the materials used in PIC fabrication, polymers have attracted significant interest due to their unique characteristics. To fabricate polymer-based PICs, establishing an accurate manufacturing process for the cross-sectional structure of an optical waveguide is crucial. For stable device performance and high yield in mass production, a process with high reproducibility and a wide tolerance for variation is necessary. This study proposes an efficient method for fabricating polymer optical-waveguide devices by introducing the atomic layer deposition (ALD) process. Compared to conventional photoresist or metal-film deposition methods, the ALD process enables more precise fabrication of the optical waveguide's core structure. Polyimide optical waveguides with a core size of 1.8 × 1.6 ㎛² are fabricated using the ALD process, and their propagation losses are measured. Additionally, a multimode interference (MMI) optical-waveguide power-splitter device is fabricated and characterized. Throughout the fabrication, no cracking issues are observed in the etching-mask layer, the vertical profiles of the waveguide patterns are excellent, and the propagation loss is below 1.5 dB/cm. These results confirm that the ALD process is a suitable method for the mass production of high-quality polymer photonic devices.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.37 no.5
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• pp.39-48
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• 2000

We newly proposed a polymer based vertical asymmetric optical coupler, which was characterized by simple fabricating procedure and short coupling length. And we fabricated a thermo-optic modulator using the polymeric optical coupler. We optimized the proposed device by coupling characteristic analysis. In a TE polarized 1.33${\mu}{\textrm}{m}$ wavelength, we obtained very short coupling length(L=277.6${\mu}{\textrm}{m}$) with 0.4${\mu}{\textrm}{m}$ thickness of middle layer, high coupling efficiency(94%), and asymmetric vertical waveguides with n$_{u}$ = 1.522, n$_{l}$ = 1.51. We implemented vortical asymmetric thermo-optic modulator with lower inverted rib waveguide and upper slab waveguide. In the 600Hz bandwidth and 4.5㎽ input power, the extinction ratio of the mode was 17㏈ with an insertion loss of 4.5㏈.

• Korean Journal of Optics and Photonics
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• v.19 no.2
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• pp.127-131
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• 2008

A refractometric glucose biosensor incorporating a vertically coupled microring resonator in polymers was proposed and realized. The ring was covered with a target analyte of glucose solution with a certain concentration, so that its effective refractive index could be altered and, as a result, the resonance wavelength of the sensor was shifted. Therefore the concentration of the glucose solution can be estimated by observing the shift in the resonance wavelength. Two schemes were exploited for enhancing the sensitivity of the sensor. First, the effective refractive index of the polymeric waveguide used for the resonator sensor was adjusted to approach that of the target analyte as best as possible. Second, the ring waveguide, which serves as a crucial sensing part, was appropriately over-etched to enlarge its contact area with the analyte. The proposed resonator sensor was designed with the beam propagation method. The refractive indices of the core and cladding polymer involved were 1.430 and 1.375 respectively, leading to the waveguide's effective refractive index of ${\sim}1.390$, which is faiirly close to that of the glucose solution of ${\sim}1.333$. The prepared ring resonator with the $400-{\mu}m$ radius exhibited the free spectral range of 0.66 nm, the bandwidth of 0.15 nm, and the quality factor of 10,000. For the sensor operating at 1,550 nm wavelength, the achieved sensitivity was as great as 0.28 pm/(mg/dL), which is equivalent to 200 nm/RIU.

• Journal of the Institute of Electronics and Information Engineers
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• v.54 no.5
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• pp.17-23
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• 2017

Optical current sensors are suitable for operation in high voltage and high current environments such as power plants due to they are not affected by electromagnetic interference and have excellent insulation characteristics. However, as they operate in a harsh environment such as large temperature fluctuation and mechanical vibration, high reliability of the sensor is required. Therefore, many groups have been working on enhancing the reliability. In this work, an integrated optical current sensor incorporating polarization-rotated reflection interferometer is proposed. By integrating various optical components on a single chip, the sensor exhibits enhanced stability as well as the solution for low-cost optical sensors. Using this, we performed the characterization for the actual field application. By using a large power source, the current of 0.3 kA~36 kA was applied to the photosensor and the linear operation characteristics were observed. The error of the sensor was within $0{\pm}.5%$. Even when operating for a long time, the error range of the sensor was kept within $0{\pm}.5%$. In addition, the measurement of the frequency response over the range of 60 Hz to 10 kHz has confirmed that the 3-dB frequency band of the proposed OCT is well over 10 kHz.

• Applied Chemistry for Engineering
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• v.18 no.1
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• pp.77-83
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• 2007

It is essential that second order nonlinear optical materials have low optical propagation losses in the wavelengths of second harmonic generation for practical applications in waveguides. Three dipolar chromophores substituted with nitro, cyano, and alkyl sulfone as an electron withdrawing group were prepared. The UV-Vis absorption spectra of the cyano and alkylsulfone chromophores showed a blue-shift compared to the nitro chromophore. The introduction of oxadiazole segment in the chromophore structure led to similar spectral shift. The blue-shift can produce low optical loses at second harmonics. The chromophores were successfully attached to a polyimide, yielding side chain polymers. The nonlinear optical property of the prepared optical polymers was determined by measuring electro-optic coefficient at 1.55 mm. The polymers exhibited high glass transition temperature of over $185^{\circ}C$ and thermal stability to $300^{\circ}C$ through differential scanning calorimeter analysis and thermal gravimetric analysis.

• Korean Journal of Optics and Photonics
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• v.20 no.5
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• pp.266-271
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• 2009

We designed a thermo-optic switch based on a directional coupler with not only a high extinction ratio but also significantly low power consumption. The switch operates by using the thermo-optic effect of the polymer which the refractive index changes by heating the electrode. If the electrode is not powered (OFF), the input light will be coupled completely to the other waveguide. When the electrode is powered at a certain level (ON), input light launched into the input waveguide will remain in that waveguide due to the lower index adjusted in the other waveguide. The switch based on the directional coupler was designed using the generalized extinction ratio curve and the lateral shift of the input waveguide. The coupling length is 1,610 ${\mu}m$ and the extinction ratios are -28 and -30 dB for ON and OFF states, respectively. The electrode structures were optimized by thermal analysis. The transported heat into the waveguide is increased, as the electrode width (w) is increased and the center distance between the electrode and the waveguide (d) is decreased. Also, because the heat generated in the electrode affects the other waveguide, the temperature difference between two waveguides is varied as the given w and d. There are specific conditions which have the maximum of the temperature difference. That of the temperature difference is increased as the width and the temperature of the electrode are increased. Especially, when the switch is designed using the condition with the maximum of the temperature difference for switching, the temperature of the electrode can be decreased. We expect this condition will be the novel method for the reduction of the power consumption in a thermo-optic switch.