• Korean Journal of Optics and Photonics
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• v.18 no.3
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• pp.185-189
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• 2007

A novel technology for CWDM (Coarse Wavelength Division Multiplexer) utilizing a PLC (Planar Lightwave Circuit)-AWG (Arrayed Waveguide Grating) fabrication process is proposed. BPM (Beam Propagation Method) Simulation results on the employed parabolic-horn-type input slab waveguide of AWG and the performance of the 20 nm-channel spacing CWDM with flattened passband are presented. Waveguides of $0.75{\triangle}%$ have been used in this experiment and the insertion loss at the peak wavelength is 3.5 dB for a Gaussian spectrum and is 4.8 dB for a flat-top spectrum. The bandwidth at 3 dB is better than 10 nm and 13 nm for Gaussian and flat-top spectra, respectively.

• Korean Journal of Optics and Photonics
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• v.15 no.5
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• pp.469-474
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• 2004

We have fabricated and designed wavelength-tunable sampled grating distributed Bragg reflector laser diodes(SGDBR-LD) by using, for the first time, planar buried heterostructures(PBH). The diodes have low threshold current values and high-performance of laser operation. Growth condition using metal organic chemical vapor deposition(MOCVD) was optimized for the formation of a good butt-coupling at the interface. A maximum output power of the fabricated device was 20 mW under 200 mA continuous wave(CW) operation at $25^{\circ}C$. Average threshold current and voltage were 12 mA and 0.8 V, approximately. This output power is higher than those of ridge waveguide(RWG) and buried ridge stripe(BRS) structures by amounts of 9 mW and 13 mW, respectively. We obtained a tuning range of 44.4nm which is well matched with the target value of our design. The side mode suppression ratio of more than 35 dB was obtained for the whole tuning range. Optical output power variation was less than 5 dB, which is 4 dB smaller than that of RWG structures.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.38 no.8
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• pp.34-42
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• 2001

The 1${\times}$2, 1${\times}$4 and 1${\times}$8 multimode interference(MMI) optical power splitters are fabricated by using $Ag^+-Na^+$ ion exchange on BK7 glass. Before fabricating the MMI optical power splitters, we find the refractive index of the channel waveguide and calculate the multimode section length and width. The multimode section lengths and widths are 887${\mu}m$, 1666${\mu}m$ and 1834${\mu}m$ and 40${\mu}m$, 80${\mu}m$ and 120${\mu}m$ for 1${\times}$2, 1${\times}$4 and 1${\times}$8 MMI optical power splitters respectively. The measured properties of the fabricated MMI optical power splitters show that the unbalance ratios of the 1${\times}$2, 1${\times}$4 and 1${\times}$8 MMI optical power splitters are 1.4[dB], 1.7[dB] and 2.0[dB] and the excess losses of those sre 0.96[dB], 2.26[dB] and 1.67[dB]. respectively.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.4
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• pp.777-790
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• 2001

Theoretical analyses have been tried to design high power and stable operating SLD at 1.55${\mu}{\textrm}{m}$ wavelength range which is the lowest absorption wavelength in optical fiber. The materials of active layer and SCH layer were chosen as conventional In1-xGaxAsyPl-y quaternary composition systems. From the transverse mode and the lateral mode analyses of waveguide, the optical power distributions and the optical confinement factor have been studied for single-mode high power operation. According to these analyses, it was calculated the composition and the thickness of SCH layer to obtain the maximum optical confinement factor. In order to obtain low values of the reflectivity, we used the window region and the lateral tilted angle between tile active region and window region. And the reflectivity of SLD was calculated with the gaussian beam approximation and mode analysis. From these researches, it was confirmed for several results to fabricate the efficient and stable SLD. In case of using $1.3\mum$, InGaAsP SCH layer, the layer thickness was obtained $0.08\mum$, to get the maximum optical confinement factor. Using $0.2\mum$, active layer thickness and $0.08\mum$, SCH layer thickness, the window region length is about $100\mum$ without An coating, $10\mum$ in 1% AR coating to obtain about 10-4 reflectivity. When the tilted angle is about $10~15^{\circ}$, the reflectivity is about 10-3. From these results, if the window region length and tilted angle were controlled appropriately in given device structure, it was confirmed that it is possible to fabricate the stable SLD without AR coating analytically.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.44 no.11
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• pp.26-35
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• 2007

We characterized the properties of the fabricated filter with the total internal reflection mirror (TIR) in the rectangular ring resonator and very small multimode interference (MMI) couplers on an InP material platform for photonic integrated circuits. Coupling power in and out of a resonator is increased by using an optimum MMI length of 110 ${\mu}m$ and a width of 9 ${\mu}m$, respectively. The semiconductor optical amplifier with the length of 120 ${\mu}m$ is integrated in the resonator to compensate the loss of the internal waveguide and the TIR mirror. A free spectral range of approximately 2 nm (244 GHz) is observed with an on-off ratio of 13 dB. The curve fitting also yields the power coupled per pass as 42%. To reach critical coupling at this coupling level would require a round trip loss of about 2.4 dB.

• Korean Journal of Optics and Photonics
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• v.17 no.4
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• pp.371-380
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• 2006

We design and fabricate a novel tunable wavelength filter, which utilizes long-range surface plasmon-polaritons excited along nm-thick-metal strips. A gold metal strip, with $\sim$ cm length, 20 nm thickness, and $\sim$ 5$\mu$m width, is embedded in thick thermo-optic Polymer films supported by a silicon wafer. A dielectric Bragg grating structure is Placed on the metal strip, so that transmission signals at telecom wavelength are selected by thermal effect of the thermo-optic polymer. High extinction ratio of 25 dB and total insertion loss of $\sim$25 dB/cm can be measured by single-mode coupling of optical fibers. We also verify that wavelength tuning of the long-range surface plasmon-polariton filters can be achieved by electric current directly applied to the metal-strip waveguides.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.6
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• pp.52-60
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• 1999

Fabricability of phase shifted grating filters has been theoretically studied by an effective index transfer matrix method. In the optical band-pass filter with multiple ${\lambda}/4$ phase-shifts, the phase-shift error and random variation of the grating period should be suppressed such that corresponding resonance frequency lies within, the filter pass-band. The tolerance for the relative error is less than $10^3$, and is quite stringent in typical filters for WDM application. End facet reflection produces ripple in the transmission spectra and the reflectivity should be less than 1% in order to keep the ripple less than 0.25dB. Also, the effect of waveguide absorption loss is enhanced by the resonance in the filter, and the absorption should be limited to 1dB/cm for the signal loss of less than 0.2dB.

• 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.

• Macromolecular Research
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• v.11 no.3
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• pp.133-145
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• 2003

We have developed novel lanthanide-cored supramolecular systems with highly efficient light-harvesting dendritic arrays for integrated planar waveguide-typed amplifiers. Er$^{3+}$ ions were encapsulated by the supramolecular ligands, such as porphyrins and macrobicyclics. The supramolecular ligands have been designed and synthesized to provide enough coordination sites for the formation of stable Er(III)-chelated complexes. For getting a higher optical amplification gain, also, the energy levels of the supramolecular ligands were tailored to maintain the effective energy transfer process from supramolecular ligands to erbium(III) ions. Furthermore, to maximize the light-harvesting effect, new aryl ether-functionalized dendrons as photon antennas have been incorporated into lanthanide-cored supramolecular systems. In this paper, molecular design, synthesis and luminescent properties of novel lanthanide-cored integrated supramolecular systems with highly efficient light-harvesting dendritic arrays will be discussed.d.

• Korean Journal of Optics and Photonics
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• v.9 no.2
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• pp.76-85
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• 1998

Organic single crystal of p-toluene sulfonate(PTS) bulks and thin films were fabricated using a slow solution evaporation method. Third and fifth order nonlinear refractive indices, $n_2$and $n_3$, of PTS crystals at 1600 nm were determined by the Z-scan method and the multimode output of the PTS thin film waveguide was observed at 1350 nm. When the beam intensity is in 2-5 GW/$cm^2$, the nonlinear refractive indices are $n_{2}=6{\times}10^{-4}cm^{2}$/GW and $n_{3}=-7{\times}10^{-5}cm^{4}/GW^{2}$ and the two and three photon absorption coefficients are zero. When the beam intensity is in 5~16 GW/$cm^2$, the split-step fast Fourier transform beam propagation method simulation shows that the beam propagation in the PTS is distorted from the gaussian shape.