• Journal of the Korean Ceramic Society
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• v.39 no.6
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• pp.594-597
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• 2002

Silicon Oxynitride(SiON) thick films on p-type silicon(100) wafers have obtained by using plasma-enhanced chemical vapor deposition from SiH$_4$ , N$_2$O and N$_2$. Prism coupler measurements show that the refractive indices of SiON layers range from 1.4620 to 1.5312. A high deposition power of 180 W leads to deposition rates of up to 5.92${\mu}$m/h. The influence of the deposition condition on the chemical composition was investigated using X-ray photoelectron spectroscopy. After deposition of the SiON thick films, the films were annealed at 1050$^{\circ}C$ in a nitrogen atmosphere for 2 h to remove absorption band near 1.5${\mu}$m.

• Korean Journal of Materials Research
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• v.12 no.4
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• pp.254-258
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• 2002

To realize channel cross-connecting in optical communications systems, a high speed optical matrix switch was fabricated using z-cut $LiNbO_3$. For switch fabrication was design bending structure and coupling length and four $2{\times}2$ directional couplers were integrated on one substrate far construction of a $4{\times}4$ switch. Single-mode optical waveguides were formed by Ti-diffusion at a wet $O_2$ atmosphere. Ti-diffusion profile, refractive index variation and waveguide morphology were analyzed by Prism coupler and optical microscopy, respectively.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.12
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• pp.1321-1328
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• 2003

In this paper, we demonstrate that the directivity of the CPW(Coplanar Waveguide) directional coupler with finite-extent backed conductor is enhanced by eliminating center region of backed conductor appropriately. If the backed conductor is removed at center region of couplers, the couplers have two backed conductors. If effective odd mode dielectric constant is decreased at center region, the electrical length for odd mode is changed and phase velocity is same at the directional couplers. Hence, directivity is improved. The eliminated length is solved by an odd and even mode analysis. The designed moderate CPW directional coupler with the proposed compensation structure has excellent directivity and matching characteristic at center frequency in simulation and measurement.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.4
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• pp.449-456
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• 2012

Herein, we design a wideband $8{\times}8$ waveguide Butler matrix in order to use in a multi-port amplifiers(MPAs) at Ka-band. To achieve the broadband characteristic, we design a binomial 6-slot 3 dB directional coupler which is used to configure the $8{\times}8$ Butler matrix. The measured results of the fabricated $8{\times}8$ Butler matrix have low insertion loss of less than 0.3 dB, good return loss of over 26 dB and high isolation of over 35 dB within the design bandwidth of 3 GHz.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.15 no.2
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• pp.221-227
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• 2015

The polarization characteristics of nano-scale grating-assisted polarization-insensitive coupler (GA-PIC) consisted of double sandwiched rib-type layers are evaluated in detail by using modal transmission-line theory (MTLT) based on equivalent network. To obtain the polarization-insensitive condition of GA-PIC, the coupling lengths as a function of the refractive index and thickness of sandwiched rib-type layer as well as the grating thickness and period are analyzed for quasi-TE and quasi-TM modes. The numerical results show that the GA-PIC with hundreds of nanometer scale is realized by properly choosing structural and material parameters of double sandwiched layers and grating.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.31A no.8
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• pp.7-15
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• 1994

In this paper, the directional coupler for Ku-band, which is designed is of the crossguide type with a coupling value of about 3-dB. The apertures chosen for this design are crosses. We used polynomial approximations of rounded end slot to obtain the electric and magnetic polarizability of crossed-slot and compared the results with Cohn's experimental results. The optimized dimensions and positions of the cross aperture are obtained by a trial-and-error reiteration of the program. This paper presents the measurement results for the designed coupler. The very flat coupling shows a total variation of only 29.80$\pm$0.04dB for the design frequency ranges of 12.25GHz-12.75GHz. The measured minimum directivity is 25dB. The aperture attenuation for the finite diaphragm thickness is about 2dB pr 0.5mm, which is in agreement with the theoretical value. The transmission loss and input return loss at center frequency are 0.0564dB and 48.16dB respectively. We obtained the measured minimum directivity of the coupler. Whose apertures are both circles is better than that containing holes in the performance of directivity.

• 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㏈.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.23 no.6
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• pp.157-162
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• 2023

A highly sensitive refractive index bio-sensor based on grating-assisted strip directional coupler (GASDC) is proposed. The sensor is designed using two asymmetric strip waveguides with a top-loaded grating structure in one of the waveguides. Maximum light couples from one waveguide to the other at the resonance wavelength satisfying phase-matching condition (PMC), and it shows that the change in phase-matching condition with the change in refractive index of the analyte medium in the cover region can be used as a measure of the sensitivity. The proposed sensor will be an on-chip device with a high refractive index sensitivity, and the sensor configuration offers a low propagation loss, thereby enhancing the sensitivity. Furthermore, variation of the sensitivity with the waveguide parameters of sensor is evaluated to optimize the design.

• Korean Journal of Optics and Photonics
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• v.8 no.2
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• pp.149-153
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• 1997

We demonstrate the operating characteristics(center wavelength, bandwidth, TE/TM polarization, tuning range) of grating-assisted co-directional coupler(GACC) filter fabricated with InGaAsP compound semiconductor. A design of waveguide structure has been focused on the narrow bandwidth characteristics of the filter. Reactive ion etching technique was employed for the uniform waveguide formation. The bandwidths(FWHM) and center wavelengths of the fabricated GACC filter were measured by 1.5 nm and 1530.6 nm for TE polarization and 1.3 nm and 1494.0 nm for TM polarization. This is the one of the narrowest bandwidth at 1530 nm region ever reported. The center wavelength shifted form 1530 nm to 1538 nm when the current of 100 mA was injected at 4.5 mm-long device. Good agreement between the designed and measured operating characteristics for some waveguide structures is demonstrated.

• Journal of the Korean Ceramic Society
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• v.38 no.12
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• pp.1150-1154
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• 2001

Silicon oxynitride (SiON) thick films using the core layer of silica optical waveguide have been deposited on Si wafer by PECVD at low temperature (32$0^{\circ}C$) were obtained by decomposition of appropriate mixture of (SiH$_4$+$N_2$O+$N_2$) gaseous mixtures under RF power and SiH$_4$/($N_2$O+$N_2$) ratio deposition condition. Prism coupler measurements show that the refractive indices of SiON layers range from 1.4663 to 1.5496. A high SiH$_4$/($N_2$O+$N_2$) of 0.33 and deposition power of 150 W leads to deposition rates of up to 8.67 ${\mu}{\textrm}{m}$/h. With decreasing SiH$_4$/($N_2$O+$N_2$) ratio, the SiON layer become smooth from 41$\AA$ to 6$\AA$.